Affliation: Principal Investigator, Singapore Immunology Network, A*STAR

Convenor: Dr. Stephan Gasser

Abstract:
All Dendritic cells (DCs) are in a dynamic balance with an estimated half-life ranging from 7 days to 14 days during steady state conditions. Although this rapid turnover mandates a continuous replacement by DC precursors, the identity of these precursors that contribute to steady state DC replenishment remained a subject of controversy and past attempts to identify these committed DC precursors have lead to a wide range of results. In the recent years, several elegant studies had succeeded in the characterization of DC committed progenitors in lymphoid tissues and a plausible DC ontogeny scheme from the bone marrow to the lymphoid tissues is now emerging.  

However, none of the studies discussed above examined the capacity of these DC precursors to give rise to non-lymphoid tissues DCs. Indeed, very little is known about the precise origin and the mechanisms that control the development of non-lymphoid tissue DCs in steady state. Here we show that two populations of CD11c⁺MHCII⁺ cells separated on the basis of CD103 and CD11b expression co-exist in most non-lymphoid tissues. CD103⁺ DCs are related to lymphoid organ CD8⁺ DCs in that they are derived exclusively from pre-DCs under the control of Flt3 ligand, Id2 and IRF8. The other population of CD11c⁺MHCII⁺ cells in tissues, which is CD103^–CD11b⁺, is heterogenous and depends on both Flt3 and MCSF-R. Our results reveal that non-lymphoid tissue CD103⁺ DCs and lymphoid organ CD8⁺ DCs derive from the same precursor along a similar differentiation program and also reveal the existence of a DC restricted lineage in the control of DC homeostasis in all tissues, lymphoid and non-lymphoid. The discovery of DCs related to lymphoid organ CD8⁺ DCs in most non-lymphoid tissues including the skin, lung, liver, kidney and pancreatic islets, together with recent results revealing the presence of a CD8⁺ DC equivalent population in human blood have important impact on immunotherapy strategies aiming at targeting CD8⁺ T cells.

Affiliation: Departments of Surgery, Immunology and Infectious Diseases & Microbiology, University of Pittsburgh and University of Pittsburgh Cancer Institute, USA

Convenor: Dr. Stephan Gasser

Abstract:
NK cells and CD8+ T cells, traditionally considered as immune effector cells, can also play regulatory functions, either suppressing or enhancing the immunogenic properties of dendritic cells (DC). These opposed functions are performed at different stages of activation of NK- and CD8⁺ T cells and involve different molecular mechanisms, allowing us to selectively suppress or enhance them for therapeutic purposes.  The “effector” pathway of activation of NK cells and the effector stage of CD8⁺ T cell activation are associated with the perforin- and granzyme B-mediated elimination of DCs. In contrast, IL-18-induced “helper” NK cells and memory-type CD8⁺ T cells, that both release TNF and IFN-prior to acquisition of cytotoxic function, protect DCs from CTL-mediated killing and induce mature type-1 polarized DCs (DC-1) characterized by strongly-enhanced, rather than “exhausted”, ability to produce IL-12p70 and other CTL-, Th1-, and NK cell-activating cytokines. A single round of in vitro sensitization with DC-1s loaded with tumor-related antigens induces 40-70-fold higher numbers of functional CTLs against different types of tumors, when compared with nonpolarized mature DCs. Such polarized DC-1s are particularly effective in inducing tumoricidal activity of CD8⁺ T cells and NK cells and Th1 differentiation of CD4⁺ Th cells (delivery of “signal 3”). They also induce tumor-relevant homing properties of the immune cells (delivery of “signal 4”). DC1s generated ex-vivo (DC-based vaccines) or in vivo (by promoting DC interaction with memory-type virus-specific CD8⁺ T cells), have proven effective in multiple mouse tumor models, and show early promise in our ongoing phase I/II clinical trials. Modulation of helper and suppressive activities of NK- and CD8⁺ T cells is also a potential target for immunotherapy of chronic infections and autoimmune diseases.

Affliation: FRCP, MPH, MD, DTM&H, Kings College London

Convenor: Dr. Stephan Gasser

Abstract:
Long term-non-progression: Despite varying rates of disease progression, the majority of HIV-infected individuals eventually progress to AIDS in the absence of antiretroviral therapy (ART). However, approximately 2% of HIV infected individuals maintain long-term stability in their CD4 count (>500 cells) and are referred to as long-term non-progressors (LTNPs).  A further subset (0.5 -1%) also achieve impressive viral control (viral load <500 or even <50 copies/ml) in the absence of ART and are termed Elite controllers. An understanding of the mechanisms for LTNP and natural viral control may yield critical insights for prophylactic and therapeutic antiviral interventions. The heterogeneous mechanisms that contribute to this phenotype will be reviewed briefly, including host genetic factors, innate and adaptive immune responses, and attenuated viral infection.

HIV Immune Reconstitution Syndrome: Between 10% and 40% of patients who start ART experience a syndrome characterized by an excessive inflammatory response and a paradoxical deterioration in clinical status. This phenomenon is thought to be due to an ART-associated recovery of pathogen-specific immune responses to pre-existing or latent infections, and has been termed immune reconstitution inflammatory syndrome (IRIS). While the clinical features of IRIS are well-documented, a better understanding of the immunopathogenesis is needed to develop strategies to prevent and treat IRIS. I will show data from clinico-pathological assessment of patients with IRIS that mechanisms differ according to the type of pathogen, and whether the immune response is against viable or non-viable organisms.

Affiliation: Viertel Fellow and HHMI Scholar, Division of Immunology, The Walter and Eliza Hall Institute of Medical Research.

Convenor: Dr. Stephan Gasser

Convenor: A/Prof Ho Bow

Abstract:
The recent SARS epidemic has boosted global interest in the discovery of novel human and animal coronaviruses. The number of coronavirus species with complete genomes available has increased from nine in 2003 to about 30 in 2009, of which nine, including human coronavirus HKU1, bat SARS coronavirus, group 1 bat coronavirus HKU2, three groups 2c and 2d coronaviruses, and three group 3c avian coronaviruses were sequenced by our laboratory. Recently, we have also developed a comprehensive database, CoVDB (http://covdb.microbiology.hku.hk), of annotated coronavirus genes and genomes, for rapid and accurate batch sequence retrieval, the cornerstone and bottleneck for comparative gene or genome analysis. With the increasing amount of genomes available and the user-friendly database, easy comparative genome analysis and more specific blast search results can be generated for efficient downstream analysis.

Affliation: Departments of Microbiology, National University of Singapore

Convenor: A/Prof Ho Bow

Abstract:
MAP kinase signaling pathways are evolutionary conserved immune regulators, having critical roles in innate and adaptive immune responses. The biological outcome of MAP kinase activation is determined by the duration and magnitude of their activation. It has been shown that members of MAP kinase phosphatase (MKP) protein family are major negative regulators of MAP kinase signaling. By controlling the activation of MAP kinases, MKPs play critical roles in immune responses. The functions of several MKP members, including MKP1, MKP5, and Pac-1, in immune responses have been studied. However, the functions of most of the MKP members in regulation of MAP kinases and in immune responses are not clear. In this study, we found that the deficiency of one MKP member, MKP7, led to an  impaired function of NK cells in innate immunity.  MKP7 deficient mice are defective in anti-intracellular bacterial infection. In adaptive immunity, MKP7 deficient mice have reduced Th17 responses, which resulted in the resistance of the mice to MOG-induced EAE disease. This study demonstrate that MKP7 has specific function in immune responses to infection and in autoimmune diseases.

Affliation: Assistant Professor, Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University.

Convenor: A/Prof Ho Bow

Abstract:
Wound healing is a complex process that consists of a cascade of overlapping events, including inflammation reepithelialization and remodeling, directed at the restoration of the epidermal barrier. The regulation of wound repair is dictated by epithelial–mesenchymal interactions and purportedly mediated by the action of central players such as growth factors. This complex interplay demands the expression of soluble factors exerting autocrine and paracrine activities and, importantly, the integration of such diverse signals, which culminate in appropriate cellular responses. We have previously showed that nuclear receptor PPARb/d plays a pivotal role in keratinocyte response to inflammation. In this presentation, I will describe the roles of two PPARb/d target genes, namely angiopoietin-like 4 (ANGPTL4) and secreted interleukin-1 receptor antagonist (sIL-1ra) in wound healing and their implications in cancer.

Affliation: Professor of Surgery, Chair in Paediatric Surgery, Imperial College,     London,  UK.

Convenor: A/Prof Ho Bow

Abstract:
A novel subset of lung stem/progenitor cells expressing CD34 and Oct-4 were identified in human lung. These cells could be isolated from the lung of newborn mice and they are susceptible to infection of a variety of viruses in vitro, including SARS coronavirus and highly pathogenic avian influenza H5N1 virus. In the autopsy human lung, the lung stem/progenitor cells are indeed the major target for SARS and H5N1 infection. The lung stem/progenitor cells also express a C-type lectin pathogen-binding receptor L-SIGN (CD209L), whose polymorphism is significantly associated with SARS susceptibility through modulating the viral degradation via a proteasome-dependent pathway. Furthermore, infection of these viruses induces a unique regulatory pattern of the production of soluble factors and molecules critical for fat metabolism. The lung stem/progenitor cells can also rescue pulmonary function insufficiency induced by chemicals by regenerating type II pneumocytes in vivo.  Finally, cells expressing similar phenotype also exist in the small bowel surface layer of the neonates and its polymorphism affects the disease progression of neonatal necrotising enterocolitis.

Convenor: A/Prof Ho Bow

Abstract:
Pathogenic bacteria constitute a serious threat to global health and have evolved a variety of strategies to defeat their hosts. A critical first line of defence that is evolutionarily conserved across metazoans is the innate immune system, which enables the host to recognize the aggressors and to communicate this information between and within cells to elicit appropriate responses to pathogens. Elucidation of both local and systemic effects is best accomplished by studying host-pathogen interactions within the context of a whole organism. Using infection of C. elegans by a variety of human bacterial pathogens as the experimental system, we have identified new factors that act in the intestinal cells to mediate local immunity, and factors within the nervous system that function non-cell autonomously to modulate immune function in vivo.  Factors that act within the intestine to affect immune gene expression include the ELT-2 GATA transcription factor, and two polyunsaturated fatty acids, gamma-linolenic and stearidonic acids. Within the neurons signal transduction pathway mediated by Goa affects immune function non-cell autonomously, in part by regulating the release of an insulin-like agonist, INS-7, by dense core vesicles.  INS-7 activates insulin signaling, which results in the retention of the FoxO transcription factor DAF-16 in the cytoplasm and the downregulation of immune gene expression. The importance of GATA factors and neuronal regulation of immunity is further underscored by the discovery of novel mechanisms by which Pseudomonas aeruginosa and Burkholderia pseudomallei target ELT-2 and the neuro-immuno axis to suppress host immunity.

Affliation: Cambridge Institute for Medical Research, University of Cambridge, School of Clinical Medicine

Convenor: Dr. Stephan Gasser

Abstract:
Part 1: FcγRIIb is an inhibitory Fc receptor, and defects in it are known to predispose to systemic lupus erythematosus (SLE) in both mouse and man.  Mechanisms by which these deficiencies contribute to disease will be discussed, as will the role played in the pathogenesis of disease by genetic variation in FCGR2B.  Data will be presented implicating malaria is an important evolutionary selection factor driving retention of these autoimmunity-associated polymorphisms in the gene pool. Gene copy number variation (CNV) has recently been recognised as a major source of genetic variation in the human population.  FCGR3B CNV is very common in the population, and is associated with marked alterations in expression and function of the receptor on neutrophils.  Low CNV can be demonstrated to the risk of some autoimmune diseases (such as SLE) but not others, shedding light on the functional role it plays.  Novel data on interactions between FCGR3B CNV and FcγRIIb in driving autoimmunity will be discussed. 

Part 2: We have performed detailed microarray-based analysis of gene expression in purified leucocyte subsets from patients with various autoimmune diseases.  Analysis of the transcriptome of CD8 T cells in these diseases shows evidence of a transcriptional signature which correlates with long term disease outcome.  The dysregulated genes which create the signature immediately suggest a mechanism by which it might drive CD8 T cell contribution to disease.  This biomarker is now being assessed for its ability to guide therapy in autoimmune disease. 

Affliation: Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine

Convenor: Dr. Kevin Tan

Abstract:
The NK cells of a human individual are highly heterogeneous and comprise cellular repertoires that display substantial person-to-person variation. A prime factor responsible for functional NK cell heterogeneity is the variegated expression of HLA class I-specific inhibitory receptors: members of the KIR family, the NKG2A and LILRB1 receptors. Utilizing 14-parameter, high-dimension flow cytometry, multiplex cell-based assays and multi-parameter analyses, we succeeded in examining the function and structure of human NK cell repertoires. Through our analyses, we discovered that the polymorphisms of HLA class I and KIR combine to endow NK cell repertoires with a range of cellular subsets that exhibit significant variation in levels of missing-self response. Repertoires are structured to prevent excessively strong or weak function, a phenomenon we have termed 'repertoire calibration'. Thus, HLA class I polymorphisms hold key roles in controlling cells of both innate and adaptive immunity; in education and regulation of NK cell subsets and in antigen presentation to T lymphocytes. We are now at the stage where these analyses will be applied to understand human variation in health and disease, and to develop effective immunotherapy.

Affiliation: Professor, Molecular Genetics and Microbiology, Professor, Medicine Director, Duke Center for RNA Biology, Duke University Medical Center, Duke-NUS Graduate Medical School

Convenor: Dr. Kevin Tan

Abstract:
Dengue fever (DF) is the most frequent arthropod-borne viral disease of humans, with almost half of the world’s population at risk of infection.  The high prevalence, lack of an effective vaccine, and absence of specific treatment conspire to make DF a global public health threat.  Given their compact genomes, dengue viruses (DENV 1-4) and other flaviviruses likely require an extensive number of host factors; however, only a limited number of human, and an even smaller number of insect host factors have been identified.  To discover insect host factors required for DENV-2 propagation, we carried out a genome-wide RNA interference screen in Drosophila melanogaster cells using a well-established 22,632 dsRNA library.  This screen identified 116 candidate dengue virus host factors (DVHFs).  While some were previously associated with flaviviruses (e.g., V-ATPases and alpha-glucosidases), most DVHFs were newly implicated in DENV propagation.  The dipteran DVHFs had eighty-two readily recognizable human homologues and, using a targeted siRNA screen, we showed that forty-two of these are human DVHFs.  This indicates remarkable conservation of required factors between dipteran and human hosts.  This work suggests novel approaches to control infection in the insect vector and the mammalian host.

Convenor: Dr. Kevin Tan

Abstract:
Wiskott-Aldrich syndrome (WAS) is an X-linked genetic disorder caused by alterations in the Wiskott-Aldrich syndrome protein (WASP). Mutations in this gene gives rise to three related disease, WAS, XLT (X-linked thrombocytopenia) and XLN (X-linked neutropenia). WASP is expressed predominantly in the hematopoietic cells while its homologue N-WASP (Neural), is expressed ubiquitously. Both WASP and N-WASP are proline rich proteins and have been shown to interact with the mammalian verprolins (WIP: WASP Interacting Protein, CR16: Corticoid Regulated, WIRE: WIP Related). More than 50 missense mutations have been identified in WASP and majority of these mutations are in the region which mediates interaction with the verprolins. In order to understand the molecular defect causing the disease we are analyzing the function of the 50 mutants. The availability of S.cerevisiae mutant has allowed us to divide the mutants into two categories and the availability of N-WASP^-/- mouse fibroblast cell line has allowed us to evaluate the function of mutants without the contribution from N-WASP. WASP has been proposed to adopt a closed conformation (auto-inhibited conformation) due to interaction between the carboxy terminal and the GTPase binding domain and a number of WASP interacting proteins have been suggested to relieve this auto inhibition. We have used the split YFP (yellow Fluorescent Protein) to analyze the conformation of WASP as well as WASP-WIP complex. Using these approaches we are proposing that WASP and WIP function together in a complex compared to the generally held believe that WASP-WIP complex is inactive and that WIP has to dissociate from WASP before WASP can promote actin polymerization.

Speaker: Dr Paul Edward Hutchinson
Date: Wednesday, 29 April 2009 @ 12.00 pm  

Affiliation: Head, Flow Cytometry Laboratory, Instituto de Medicina Molecular, Portugal

Convenor: Dr. Stephan Gasser

Abstract:
The ability to rapidly analyse multiple parameters of single cells, and to purify specific populations of cells on the basis of these measurements, has made flow cytometry an essential tool in life science research. In recent years there have been significant advances in machine technology and in the applications researchers use flow cytometry. For instrumentation the switch to nearly full digitised signal processing has increased the speed and accuracy of what can be measured. The rate at which cells can be sorted, and the number of populations that can be sorted, has also increased. The development of cheaper and smaller lasers has expanded the range and number of excitation wavelengths that can be used. Also new companies are on the market offering low cost and smaller alternatives for those who want to do routine analysis. In parallel to the hardware developments, there has been an increase in the number of fluorescent probes that can be used to investigate your cells of interest.  These new fluorochromes include tandem-dyes, quantum dots, and a wide range of fluorescent reporter proteins. It is also possible now to easily and cheaply make your own custom fluorochrome antibody conjugations. The combination of these advances is expanding the boundaries of what can be done by flow cytometry. There has also been growth in non-traditional flow cytometry technology. These include the Amnis ImageStream which can record the image of the cell as it passes through the laser; and developments in microfluidics which offer the promise of doing flow cytometry on a chip, with very precise and specific manipulation and measurement of individual cells. This talk will present an overview of these advances and an insight into what flow cytometry can do for you now.

Affliation: AIDS Research C, AIDS Research Center, National Institute of Infectious Diseases, Tokyo, Japan

Convenor: Dr. Kevin Tan

Abstract:
Although antiviral strategies are still evolving, the success of anti-retroviral drug development clearly indicates that any virus can be potentially tackled and controlled. Most of the viral diseases are apparently associated with efficient viral replication. And many antiviral drugs attempt to interfere with viral replication. The discovery of inhibitors of viral replication is dependent on understanding the key events taking place at the molecular level during viral infection. All the essential steps during the viral life cycle are potential targets for antiviral drugs. However, several steps of the viral life cycle remain incompletely characterized, and therefore cannot be effectively exploited in antiviral strategies. For this purpose, we have been particularly interested in the involvement of host factors in the viral replication and pathogenesis.

We attempted to control HIV-1 and HTLV-I infection in vitro as well as in vivo using our unique NOG mice model through developing novel antagonists against chemokine receptor and NF-kB as targets. These studies were further extended to suppress growth of non-virally induced human tumors in the NOG mice. As is the case with host proteins, viral proteins are also modified post-translationally by several modifications, such as phosphorylation, and ubiquitination, and such modification is pivotal in the regulation of their function. Recently, we found several host factors including the SOCS1, and atypical protein kinase C which appear to be important in HIV-1 Gag trafficking or polarized budding of HIV-1 virion, respectively.

Affiliation: Group leader, University of Munich, Germany

Convenor: Dr. Kevin Tan

Abstract:
Trypanosomes are mammalian pathogens with a complex parasitic life cycle in different hosts. Changes in gene expression profiles that result in specialized life cycle stages are crucial to adapt to these very different host environments. There is increasing evidence that changes in chromatin structure are necessary for developmental differentiation and might correlate with differential gene expression. We discovered that DOT1B, a member of the DOT histone methyltransferase family, is essential for the differentiation process. Recent data suggest that DOT1B is also involved in the regulation of cell cycle progression in trypanosomes. We want to understand how DOT1B is involved in these two very different biological processes to unravel the link between cell cycle control and developmental differentiation.
 

Abstract:
In recent years, histones have been shown to be not only passive structural components of eukaryotic chromatin, but to rather function as regulatory factors in many different biological processes, such as gene transcription/repression, mitosis, apoptosis and DNA repair. Processes involved in the alteration of chromatin are diverse and include numerous posttranslational modifications (PTMs) of histone proteins, incorporation of specific histone variants, methylation of DNA, ATP-dependent chromatin remodeling, non-coding RNAs and localization of chromatin domains in the nuclear architecture.  All of these factors seem to be interconnected constituents of a larger “epigenetic circuit” that is still not well understood. The goal of my group is to better understand the biological role(s) of mammalian histone H3 variants and their PTMs during mitosis and transcriptional regulation.

Convenor: Prof Vincent Chow

Abstract:
Understanding the genetic and ecological conditions which support the emergence of new clones of pathogenic bacteria and the waterborne spread of bacterial epidemics is vital to developing appropriate preventive measures. Vibrio cholerae the causative agent of cholera represents a paradigm for these processes in that this organism evolved from environmental non-pathogenic progenitors by acquisition of virulence associated genes, and that cholera epidemics spread through water. V. cholerae can also serve as a suitable model to study a variety of natural phenomena related to microbial genetics, pathogenesis, coordinated gene expression, bacterial evolution, and the mechanisms that sustain the bacteria in water under unfavorable conditions of hypo-osmotic stress and reduced nutrient availability. 

V. cholerae strains capable of causing cholera carry the genes for cholera toxin (CT) and a colonization factor, toxin coregulated pilus. CT, the major enterotoxin produced by V. cholerae is encoded by a lysogenic filamentous bacteriophage known as CTX phage. Our studies have demonstrated that naturally occurring strains of toxigenic V. cholerae produce infectious CTX phage particles which can convert non-toxigenic V. cholerae strains to toxigenic strains. We have also discovered and characterized other filamentous phages of V. cholerae, which cooperate with the CTX phage in the horizontal transfer of cholera toxin genes. Phage-bacterial interactions have also been shown to have a crucial role in modulating the dynamics of cholera epidemics. Our recent studies in V. cholerae genetics, epidemiology and ecology are beginning to explain the mechanisms involved in the initiation of seasonal cholera epidemics, and how the epidemics naturally end in a self-limiting manner.  

Affiliation: Professor of Biological Engineering and Comparative Medicine, Massachusetts Institute of Technology, United States of America

Convenor: Dr. Kevin Tan

Abstract:
Although antigenic variation has been recognized for almost 100 years as the primary mechanism that allows the African trypanosomes to evade the immune system until the inevitable death of the host, we have only recently developed the experimental tools to elucidate how antigenic variation works at the molecular level. Ultimately, this understanding should generate new ways to treat the disease.
 

Abstract:
The development of effective therapies to prevent and treat persistent infections is of the highest priority as they cause considerable clinical challenges and on-going health care costs. Efforts to improve the treatment and prevention of chronic viral infections require a better understanding of the immune responses needed to achieve optimal control of persistent viruses long-term. Although innate and adaptive immune responses were thought to be non-overlapping, recent evidence suggests that interplays between them occur frequently and are required for effective immunity.  Our studies attempt to define the cellular and molecular interactions required for on-going effective anti-viral immunity. We have described interactions between NK cells and dendritic cells (DC) and their impact on effective innate immunity. Whether NK cells can influence adaptive immunity remains poorly understood.  Our recent studies have focused on defining the impact of NK cells on: cytokine responses, virus-specific T cell responses and immunopathology. These findings, and the insights they provide to the critical requirements for efficient control of viral infection, will be discussed.

Convenor: Prof Chan Soh Ha

Abstract:
Group A streptococcus (GAS) is a versatile human pathogen causing diseases ranging from uncomplicated mucosal infections to life-threatening invasive diseases. The development of human-relevant models of GAS infection and the introduction of new technologies have markedly accelerated the pace of discoveries related to GAS host-pathogen interactions. 

By applying a signature-tagged mutagenesis and using murine model that mimics human necrotizing fasciitis (NF) we identified a novel serine protease of GAS (ScpC) which plays a central role in GAS in soft-tissue infections. Isogenic mutants deficient in ScpC constructed in two highly invasive GAS strains, M14-type isolate from a NF patient in Israel and M1T1 type, the most prevalent sterile site isolate globally, allowed us to show that ScpC is solely responsible for GAS-mediated IL-8 cleavage in-vitro, resulting in loss of its biological functions. We also demonstrated that ScpC cleaves the murine CXC chemokines, MIP-2 and KC in-vivo during the process of GAS-mediated soft-tissue infections. The cleavage of these chemokines has a major impact on host neutrophil functions. It impairs neutrophil recruitment to the site of infection, lowers neutrophil state of activation, and also reduces neutrophil extracellular trap formation, thus promoting GAS survival and proliferation.

Topic: Using genomics to reveal biology in multiple myeloma
Speaker: Associate Professor CHNG Wee Joo
Date: Tuesday, 11 November 2008 @ 11.00 am

Affiliation: Department of Medicine, National University of Singapore
Consultant - Haematology, National University Hospital

Convenor: Assoc Prof Herbert Schwarz

Abstract:
Multiple myeloma is an incurable post-germinal center B-cell malignancies that is the second most common haematological malignancies. It is characterized by infiltration of the bone marrow by clonal plasma cell that secretes monoclonal immunoglobulins and clinically manifest with anaemia, lytic bone lesion, hypercalcaemia and/or renal impairment. The use of global genomics technology such as gene expression profiling and array-based comparative genomic hybridization has led to a number of significant new discoveries that has led to significant insights into underlying biology, including the genetic basis of NFKB activation in myeloma and the potential importance of the non-canonical pathway and its relation to therapeutic response, and the identification of MYC activation as an important early pathogenic event in myelomagenesis and the subsequent development of a genetic mouse model of myeloma.

Topic: Hemopoietic processes in the development and maintenance of atopy and allergic inflammation
Speaker: Professor Judah A. DENBURG, MD, FRCPC
Date: Thursday, 20 November 2008 @ 4.00 pm  

Affiliation: William J. Walsh Professor of Medicine
Director, Division of Allergy & Clinical Immunology
McMaster University, Hamilton, ON, Canada

Convenor: Assoc Prof Herbert Schwarz

Abstract:
Respiratory and allergic/immune diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, cystic fibrosis, and acute and chronic lung infections are leading causes of morbidity and mortality in Canada and globally. An inflammatory pathology is central to all of these diseases, recently recognized to include systemic processes involving the active recruitment and differentiation of hemopoietic and non-hemopoietic progenitors (also termed ‘stem cells’, SC). These cells have the potential to differentiate into a diversity of cell types found in normal tissue, as well as to contribute to repair and remodeling following lung injury. Recently, it has been proposed that circulating SC ‘sense’ injured tissue, and undergo migration and recruitment into sites of tissue damage where they can differentiate into inflammatory effector cells (such as neutrophils, eosinophils, basophils, mast cells and monocytes), or non-hemopoietic cells that can promote structural and functional tissue repair, revealing the plasticity of these pluripotent cell populations and their participation in regenerative and/or inflammatory processes. Within tissues, the fate of hemopoietic progenitors is determined by locally elaborated growth factors that permit a process termed “in-situ hemopoiesis”, leading to the accumulation of inflammatory effector cells, immunocompetent cells, and tissue structural cells (e.g., dendritic and endothelial cells).   

Accumulation of eosinophils and basophils in tissues is characteristic of allergic inflammation in rhinitis, nasal polyposis and asthma. These airway tissue inflammatory events are coincident with relevant changes and fluctuations of circulating and marrow populations of eosinophil-basophil (Eo/B) progenitors, including  SEQ CHAPTER \h \r 1upregulation of IL-5R-alpha, CCR3 (eotaxin receptor) and CXCR4 (SDF-1 receptor) on bone marrow (BM) as well as airways tissue CD34⁺ cells; the latter axis plays a critical role in adult hemopoietic SC homing, as it does during embryogenesis. The functional consequence of increased levels of progenitors in numerous compartments highlights the multiple levels at which BM SC can respond to allergic stimuli, and the results are consistent with the hypothesis that eosinophils and basophils accumulate at sites of allergic reactions, at least in part, by recruitment of SC from circulation and BM, under the influence of tissue-elaborated hemopoietic cytokines and chemokines.  

There is now a burgeoning body of evidence showing that activation of selective hemopoietic processes is not only associated with the onset and maintenance of allergic inflammation in atopic adults, but also with the development of the allergic diathesis in infants: SC functional and phenotypic alterations relevant to Eo/B lineage commitment have been observed in neonates at risk for atopy and asthma, and are further outlined below. This area promises to be of great interest in understanding the role and fate of the very abundant CD34⁺ SC populations present in cord blood (CB) at birth. 

Dysfunctional adaptive (T-cell) immunity in the genesis of atopy and asthma is paralleled by abnormalities in innate immunity, including the contribution of SC, particularly progenitors of the Eo/B lineage. We have recently reported that CB Eo/B progenitor cytokine receptors are associated with increased atopic risk, showing an inverse correlation between maternal skin prick test responses to common allergens and IL-5R-alpha/GM-CSFR-alpha expression on CB CD34+ cells at birth, and a positive correlation with IL-3R-alpha.  These alterations in CB progenitors correlate with clinical outcomes at one year, predicting both atopic dermatitis and wheeze, and can be modified in response to maternal dietary intervention during pregnancy. We have also examined the relationship between CB SC function and phenotype in 39 infants from an atopic high-risk Australian birth cohort, and the clinical response to acute respiratory illness (ARI) in the first year.  A consistent relationship was observed between increased numbers of GM-CSF- and IL-3-responsive Eo/B-colony forming cells (CFU) at birth, and the frequency and severity of ARI, including accompanying wheeze or fever.  Comparable associations were found between ARI and CB IL-3R-alpha⁺ and GM-CSFR-alpha⁺ CD34⁺ cell numbers. Conversely, a reciprocal decrease in the proportion of CB IL-5R-alpha⁺ cells was found in relation to the clinical outcomes.  

Real-time polymerase chain reaction (Q-PCR) has also recently been employed in our laboratory to ascertain the kinetic patterns of expression of Eo/B-lineage specific genes, GATA-1, MBP and IL-5R-alpha, in random fresh and frozen CB samples. Stimulation with IL-5 results in an early up-regulation of GATA-1 expression, peaking at 24-48h. In contrast, MBP is up-regulated in a slowly progressive pattern, maximally at 72h, while there is stable, low expression of IL-5R-alpha (with increase over time of the soluble, and decrease of the transmembrane, isoforms).  Numbers of Eo/B-CFU relate to antecedent GATA-1, and inversely to MBP, expression. These results provide a plausible mechanism for predicting the generation of tissue airway eosinophilic and neutrophilic inflammation in infancy and early childhood, in response to viral or allergenic stimuli. Molecular markers of critical differentiation-specific events in CB SC may herald future atopic and asthmatic biological and clinical outcomes.

Abstract:
The urgent need for vaccines to improve the global malaria situation justifies giving the highest priority to their elaboration and clinical development. Epidemiological and experimental studies have shown that protective immunity can be induced against malaria. In the field, natural immunity is acquired with time after repeated infections, and it is thought that it targets principally the merozoite. Experimentally, sterile immunity has been obtained in humans against the pre-erythrocytic stage only after immunization with radiation-attenuated sporozoites, and against blood stage parasites only after repeated immunization with live blood stage parasites under drug prophylaxis. However such high levels of protection have never been obtained with current sub-units vaccines. The reasons for this failure may be due to the use of inappropriate antigen(s) and the fact that the absence of validated correlates of protection is a serious obstacle to guide vaccine development.

The overall objective of this project is to develop new tools and approaches where a thorough comparative immunological analysis of naturally and experimentally protected versus non-protected individual will be conducted in order to identify correlates of protection against Plasmodium infection. This will allow to determine whether the immune responses associated with specific antigens actually play a role in the induced protection and subsequently to identify mechanisms of this protection.

These aims will be actively pursued by creating a library of antigens that are leading or have the potential to be vaccine candidate with a systematic analysis of the immune responses in the protected versus non-protected individuals. Such an analysis has not been previously performed. Moreover, the investigations will be greatly strengthen as they will conducted using experimental material from mice and humans and from individuals from endemic residents. Elucidating the mechanisms and targets of protection will contribute to accelerate malaria vaccine development.

Abstract:
For the development of medical diagnostics, therapeutics, and vaccines against select infectious diseases, it is crucial to identify those pathogen-specific epitopes against which the immune system mounts its unique response.

Traditional epitope discovery tools frequently rely on in vitro expansion of antigen-specific CD8+ T cell populations and probe only the cytotoxic capability of these cultured cells. Alternatively, class I MHC tetramer technology allows direct phenotypic identification of CD8+ T cell populations. The production of MHC tetramers, however, remains an arduous affair. A novel peptide exchange strategy, which employs class I MHC products loaded with conditional ligands, provides a fast and straightforward method to obtain arrays of class I MHC tetramers of diverse specificity, to facilitate CD8+ T cell epitope discovery. When combined with multicolor flow cytometry, detailed information on the T cell populations can be obtained based on characteristic cell surface markers and intracellular cytokine production.

The peptide exchange technology, in principle, allows the screening for T cell epitopes that are generated upon infection with any clinically relevant pathogen. Here, CD8+ T cell epitope discovery for Chlamydia trachomatis, Toxoplasma gondii and murine gamma herpes virus (MHV-68) will be discussed in detail, as well as ongoing efforts regarding dengue virus (DV) and respiratory syncytial virus (RSV) epitope identification.

Topic: Differential modulation of TLR4 signalling as a paradigm for macrophage “desensitization”
Speaker: Dr. Subhra Biswas
Date: Tuesday, 2 September 2008 @ 11:00AM

Affiliation: Singapore Immunology Network (SIgN)
Biomedical Sciences Institutes (A*STAR), Singapore

Convenor: Assoc. Prof. Herbert Schwarz

Abstract:
“Desensitization” of Toll-Like Receptor (TLR) signaling in innate immune cells has been proposed as a basis for their immunosuppressive phenotype in various chronic pathologies. We are engaged in investigating the molecular mechanisms for desensitization of TLR4 signalling in macrophages under different pathological conditions.

Evidence for TLR4 desensitization will be presented from an in vitro model of repeated exposure to low doses of endotoxin that resulted in progressive hyporesponsiveness to subsequent endotoxin challenge, a phenomenon often encountered following sepsis. Lipid A-induced desensitization was linked to suppressed transcription of inflammatory genes like TNFa, CCL3 and a differential regulation of MyD88 vs TRIF signalling.

Use of genetic, biochemical and bioinformatics approaches pertaining to the TLR4 pathway, we will demonstrate that the desensitization-induced suppression of TNFa and CCL3 expression was mediated by the functional TRIF pathway and its downstream mediators. These observations constitute evidence for a role of TRIF/IFN pathway in the regulation of LipidA/TLR4-mediated endotoxin desensitization. Interestingly, studying the transcriptome and molecular phenotype of tumor associated macrophages (TAM) in chemically-induced murine fibrosarcoma, we also observed a strikingly similar basis for desensitization.

This was characterized by defective MyD88/NF-kB signaling, but constitutively upregulated TRIF pathway. Defective NF-kB signaling in both the above cases was attributed to overexpression of inhibitory NF-kB p50 homodimers. Indeed, targeting of p50 NF-kB could partially reverse TAM desensitization. These studies establish the differential modulation of MyD88 and TRIF pathway as an emerging paradigm for macrophage desensitization in different pathologies.

Topic: Immunomodulatory properties of polysaccharide-protein complex from Lycium barbarum L
Speaker: Mr. Chen Zhisong
Date: Friday, 5 September 2008 @ 2:00PM 

Affiliation: Department of Microbiology, NUS

Convenor: Prof. Chan Soh Ha

Topic: New insights into erythrocyte invasion by malaria merozoites
Speaker: Assoc. Prof. Peter R Preiser
Date: Tuesday, 9 September 2008 @ 11.00AM

Affiliation: School of Biological Sciences
Nanyang Technological University, Singapore

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
Malaria merozoites are able to invade erythrocytes using a range of different invasion pathways. Each invasion pathway is specified by the interaction of parasite ligands with their appropriate receptors on the erythrocyte surface. Only if all the appropriate interactions are formed will invasion occur. While significant insights have been gained from the studies of individual parasite ligand-host receptor interactions our overall understanding of what defines a parasite invasion pathway is still limited.

Recent work using the rodent malaria parasite P. yoelii has shown that variation in the amount of parasite ligands also make a significant contribution to erythrocyte invasion (Iyer et al., 2007).

To obtain a better understanding of the contribution of merozoite proteins to different invasion phenotypes we have combined microarray analysis with quantitative proteomics to investigate changes in the expression pattern of merozoite proteins in P. falciparum merozoites displaying different invasion pathways. This approach has led to a number of new and surprising insights about merozoite invasion.

Topic: Characterising of Helicobacter pylori biofilm as a survival strategy in the extragastric environment
Speaker: Miss Ng Chow Goon (MSc candidate)
Date: Friday, 12 September @ 11:00AM

Affiliation: Department of Microbiology, NUS

Convenor: Assoc. Prof. Ho Bow

Topic: uPAR induces shape changes in integrin CD11bCD18
Speaker: Dr. Tan Suet Mien (DPhil), Assistant Professor
Date: Tuesday, 16 September 2008 @ 11:00AM

Affiliation: School of Biological Sciences
Nanyang Technological University, Singapore

Convenor: Assoc. Prof. Herbert Schwarz

Abstract:
Integrins are type I membrane cell adhesion molecules form by two distinct subunits. In general, the transition of an integrin from a bent conformation to an extended conformation serves as a hallmark of its activation – a prerequisite for ligand-binding.

However, gaining evidence suggest important roles of integrins with bent conformations. A good example comes from the association of integrins with uPAR (urokinase-type plasminogen activator receptor; CD87) in the same cell. The marked difference in the dimensions of these molecules disfavors uPAR interacting with an extended integrin.

In this talk, I will discuss the interaction of uPAR with integrin CD11bCD18 (CR3), which are both important players in leukocyte functions, and suggest a possible mechanism of uPAR-integrin signaling.

Topic: Malaria Drug Discovery at the Novartis Institute for Tropical Diseases (NITD)
Speaker: Dr. Thierry Diagana
Date: Tuesday, 30 September 2008 @ 11:00AM

Affiliation: Novartis Institute for Tropical Diseases Singapore

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
Today, artemisinin is the last defense against drug resistant malaria and recent reports suggest that decades of continuous use of these potent antimalarials as monotherapies may have fostered artemisinin drug resistance in Plasmodium. Unfortunately there are few ongoing efforts to discover and develop novel and effective antimalarial drugs to fight this
ancient and resilient scourge.

To address this unmet global health need, NITD has led the formation of a research consortium to bring together Novartis' cutting-edge drug discovery with world-class malaria biology expertise. Armed with a grant from the Wellcome Trust, the Medicines for Malaria Venture and the Singapore Economic Development Board, the consortium has the ambitious
goals of identifying (1) new drugs with a potential for a single-dose cure for P. falciparum malaria and, (2) a curative modality for P. vivax malaria.

These two goals were set to address two weaknesses with the current antimalarials, namely the poor patient compliance with most P. falciparum malaria treatments and the inability to rapidly and safely eradicate the parasite liver stages following a P. vivax infection. An overview of our efforts to achieve these goals will be presented.

Topic: Involvement of X-box binding protein 1 and nucleophosmin in cellular and viral transcription
Speaker: Dr. Jimmy Chao Sheng Hao
Date: Tuesday, 12 August 2008 @ 11:00AM

Affiliation: Research Scientist, Expression Engineering II, Bioprocessing Technology Institute, Singapore

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
Many cellular factors are involved in host-virus interaction and required for viral transcription. In this seminar, I will present our recent findings regarding the involvement of two cellular proteins, X-box binding protein 1 (XBP-1) and nucleophosmin (NPM), in cellular and viral transcription.

Firstly, XBP-1, a basic leucine zipper protein, was found to bind to the long terminal repeat of human T-lymphotropic virus type 1 (HTLV-1) and activate HTLV-1 transcription through the interaction with a viral transactivator, Tax. Furthermore, elevated XBP-1 mRNA levels were detected in the HTLV-1-infected cell lines and Tax was identified as a positive regulator of the gene for XBP-1. Collectively, our results suggest a novel host-virus interaction between XBP-1 and HTLV-1.

Secondly, a nucleolar protein, NPM, was identified as a hexamethylene bis-acetamide-inducible protein 1 (HEXIM1) binding protein. HEXIM1 functions as an inhibitor of positive transcription elongation factor b (P-TEFb), which controls elongation phase of RNA polymerase II (Pol II) transcription. Overexpression of NPM leads to activation of P-TEFb-dependent transcription, including human immunodeficiency virus (HIV) Tat and HTLV-1 Tax transactivation.

We also show that a cytoplasmic mutant of NPM, NPMc+, associates with and sequesters HEXIM1 in the cytoplasm resulting in higher RNA Pol II transcription. Considering that 35% of acute myeloid leukemia (AML) patients are diagnosed with NPMc+ mutation, our findings suggest that in some cases of AML, RNA Pol II transcription may be disregulated by the malfunction of NPM and the mislocation of HEXIM1.

Topic: Novel cytokines in infectious and inflammatory disease
Speaker: Prof. Eddy Liew
Date: Monday, 18 August 2008 @ 11:00AM 

Affiliation: Glasgow Biomedical Research Centre, University of Glasgow, Glasgow, G12 8TA, UK

Convenor: Assoc. Prof. Herbert Schwarz

Abstract:
Cytokines are the hormones of the immune system and play a pivotal role in the induction and regulation of immune response. Cytokine targeting is arguably the most important contribution of immunology to clinical practice. Thus there is a considerable interest in the search for novel cytokines. The latest members of the cytokine family are IL-33 and IL-35.

IL-33, a member of the IL-1 family, is the newly discovered ligand for the orphan receptor ST2 which is expressed on a subset of Th2 cells (but not on Th1 cells) and mast cells. IL-33 is also able to skew a predominantly Th1 cell population to a mainly Th2 cells phenotype in vivo. IL-33 could attenuate an on going atherosclerosis in ApE mice on high fat diet. The disease attenuation was accompanied by the elevation of IL-5 and IL-6 production and the reduction of IFNγ synthesis in vitro and in vivo. Furthermore, the IL-33-treated mice produced increased level of anti-oxLDL antibody which is known to be protective against atherosclerosis. The effect of IL-33 on atherosclerosis was reversed by the co-treatment of the mice with sST2 (a decoy receptor of IL-33) and anti-IL-5 antibody. Hence it appears that IL-33 may be a potential therapeutic agent against atherosclerosis via the induction of IL-5 produced by Th2 cells and consequently enhances the production of anti-oxLDL antibody by B cells. However, IL-33 is a double-edged sword. It can also enhance allergic reaction and inflammatory disease such as arthritis and asthma.

IL-33 is expressed in synovial fibroblasts from patients with rheumatoid arthritis (RA). Expression is markedly elevated in vitro by inflammatory cytokines such as IL-1 and TNFα. Mice lacking ST2 developed attenuated collagen-induced arthritis (CIA) and reduced ex vivo collagen-specific induction of and proinflammatory antibody production. cytokines (IL-17, TNFα and IFNγ) of wild type (WT) but notConversely, treatment ST2 mice with IL-33 exacerbated CIA and elevated proinflammatory cytokine and anti-collagen antibody production. Mast cells express high levels of ST2 and responded directly to IL-33 to produce a spectrum of inflammatory cytokine and chemokines in vitro. In vivo, IL-33 treatment exacerbated CIA in ST2 mice engrafted with mast cells from WT but not from ST2 mice. The disease exacerbation was accompanied by elevated levels of proinflammatory cytokine expression. Thus IL-33 is a critical pro-inflammatory cytokine for inflammatory joint disease.

ST2 mice also developed attenuated airway inflammation and IL-5 production in a murine model of asthma. Conversely, IL 33 administration induced the IL 5-producing T cells and exacerbated allergen-induced airway inflammation in wild-type as well as IL 4 mice. Thus, in the presence of antigen, IL 33 induces IL 5 producing T cells and promotes airway inflammation independent of IL-4.

IL-33 mRNA is expressed early during parasite infection of the intestinal-dwelling nematode Trichuris muris in mice. Susceptible BALB/c mice can be induced by IL-33 to expel the parasite. Thus IL-33 may be evolutionally preserved for the host defence against intestinal parasitic infection.

IL-35 is the latest cytokine of the IL-12 family. It is formed by pairing Epstein-Barr virus-induced gene 3 (EBI3) and the p35 subunit of IL-12. The Fc fusion protein of IL-35 induced proliferation of murine CD4+CD25+ and CD4+CD25- T cells when stimulated with immobilized anti-CD3 and anti-CD28 antibodies in vitro. The IL-35-expanded CD4+CD25+ T cell population expressed Foxp3 and produced elevated levels of IL-10, whereas the IL-35-induced CD4+CD25- T cells produced IFNγ but not IL-4. The in vitro-expanded CD4+CD25+ T cells retained their suppressive functions against CD4+CD25- effector cells. Furthermore, when cultured with soluble anti-CD3 and antigen-presenting cells, IL-35 suppressed the proliferation of CD4+CD25- effector cells. Moreover, IL-35 inhibited the differentiation of Th17 cells in vitro. In vivo, IL-35 effectively attenuated established CIA in mice with concomitant suppression of IL-17 production but enhanced IFNγ synthesis. Thus IL-35 is a novel anti-inflammatory cytokine suppressing the immune response through the expansion of regulatory T cells and suppression of Th17 cell development.

Topic: Techniques with Focused Laser Beam: Optical Tweezers and their Potential Applications to Biological Samples?
Speaker: Assoc. Prof. Chorn Haur Sow
Date: Tuesday, 26 August 2008 @ 11:00AM

Affiliation: Department of Physics, National University of Singapore

Convenor: Dr Kevin Tan Shyong Wei

Abstract:
Laser traps or laser tweezers, also commonly known as optical traps or optical tweezers, are finding increasingly widespread applications in the study of mechanical deformation of isolated biological cells. In this method a laser beam, which is focused through a microscope objective lens, attracts and traps a high refractive index particle, and deformation is induced as the particle attached to a cell moves with the beam. The range of forces that can be imposed by the optical trap is typically on the order of tens-to-hundred of pico-Newton (pN = 10-12 N). Many important phenomena in biology, such as cell deformation, can be investigated using the optical tweezers. In this presentation, we hope to introduce the basic principles behind the optical tweezers and discuss some of the practical issues of setting up laser tweezers. We will also discuss some of the variations in experimental setups to achieve multiple-spots tweezers, line tweezers and optical tweezers in microfluidic device.

Topic: Characterising of Helicobacter pylori biofilm as a survival strategy in the extragastric environment
Speaker: Miss Ng Chow Goon
Date: Wednesday, 16 July 2008 @ 3:00PM

Affiliation: MSc Candidate, Department of Microbiology, NUS

Convenor: Assoc. Prof. Ho Bow

Topic: “Hokoviruses” and the discovery of other novel pathogens in HK
Speaker: Dr. Herman Tse
Date: Friday, 25 July 2008 @ 11:00AM

Affiliation: Department of Microbiology, The University of Hong Kong, Hong Kong

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
The dangers presented by previously unknown viruses had been exemplified by the SARS outbreak. Active surveillance is one important component in the defense against these dangers. My colleagues and I have been screening different clinical and animal specimens, with several new human and animal viruses identified. “Hokovirus” is the designation for a group of novel viruses most recently identified in our laboratory. The novel viruses are phylogenetically related to the newly discovered human parvoviruses PARV4 and PARV5. Their epidemiological and genomic features will be discussed, and the story of the serendipitous discovery will also be touched upon.

Topic: Chronic enteroviral infections in the post-polio syndrome and type-1 diabetes mellitus
Speaker: Prof. Antonio Toniolo, MD
Date: Wednesday, 30 July 2008 @ 4:00PM

Affiliation: University of Insubria Medical School, Varese, Italy

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
Polioviruses (PVs) belong to the human Enterovirus (HEV) group of Picornaviridae and are the etiologic agents of paralytic poliomyelitis. Decades after being hit by the virus, polio survivors may develop the “post-polio syndrome” (PPS), a progressive condition characterized by chronic fatigue and pain, new muscular weakness, and cold intolerance. The etiopathogenesis of PPS is unclear. To check whether PV genomes could persist for decades in polio survivors developing PPS, we used molecular tests, tissue culture studies, and immunoassays with HEV-specific antibody. PVs were detected in samples of 27/27 PPS patients (CSF, peripheral blood leukocytes, saliva, urine) 30 to 75 years from the onset of the disease. Viral sequences and infectivity were not detected in samples of 16 control patients. Analysis of partial sequences revealed that persisting PV genomes were mostly related to the PV type-1 and were markedly different from those of reference strains.

Based on this experience, HEV infections have been investigated in blood samples of 90 children with early stage type 1 diabetes mellitus (T1D). Gene amplification and sequencing showed EV genomes in 86% of the above patients up to one-year from onset, but not in 20 control children. Different HEV types of the B and C species were represented. Cases of temporal and geographic clustering were observed in different years. In some cases, HEV genomes were detected both in probands and their family members. However, diabetes developed only in individuals carrying the high-risk DR3/DR4 HLA aplotypes.

The above data do not prove a causal relationship between chronic HEV infection and PPS or T1D. However, the high prevalence of EV sequences in PPS and diabetic patients indicates that HEVs represent significant biomarkers of both conditions.

Innovative diagnostic methods may pave the way to preventative/therapeutic interventions in order to stop the progression of virus-induced cell damage.

Topic: Bacterial genomic island discovery: a quest with a purpose
Speaker: Dr Kumar RAJAKUMAR, MBBS, MBiotech
Date: Wednesday, 11 June 2008 @ 11:00PM  

Affiliation: PhD, FRCPA, Clinical Senior Lecturer & Honorary Consultant Microbiologist

Department of Infection, Immunity & Inflammation, University of Leicester, United Kingdom

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
The discovery of genomics islands in virtually every bacterial genome characterized to date challenges our views on what constitutes a bacterial species and provokes the question as to whether 'pathovar' level identification could offer clinical benefits. Given the likely diversity within any one species, the scale of the challenge is enormous. Nevertheless, high-throughput genomics, targeted island discovery programmes and associated functional studies may ultimately define a role for high-resolution pathogen identification in particular settings.

Topic: Analysis of transcription factors in living cells with the help of the split-ubiquitin system
Speaker: Ms. Xue Xiaowei, PhD Candidate
Date: Friday, 23 May 2008 @ 2:00PM  

Affiliation: Department of Microbiology, National University of Singapore

Convenor: Dr. Norbert Lehming

Topic: Innate clearance of ring-infected RBCs by the human spleen and malaria pathogenesis: The spleen microcirculatory factor
Speaker: Dr. Innocent Safeukui
Date: Thursday, 29 May 2008 @ 11:00AM  

Affiliation: Pasteur Institute, France

Convenor: Dr. Kevin Tan S. W.

Topic: Elucidation of the biology of retroviruses and their adaptation as vectors for gene therapy
Speaker: Prof. Walter H Günzburg
Date: Friday, 30 May 2008 @ 12:00PM  

Affiliation: Christian-Doppler Laboratory for Gene Therapeutic Vector Development, Singapore & Vienna

Research Institute for Virology & Biomedicine
University of Veterinary Medicine
Vienna, Austria

Convenor: Dr. Kevin Tan S. W.

Topic: Persistence of mycobacteria in fatty biofilms
Speaker: Dr. Anil Kumar Ojha, PhD, Research Assistant Professor
Convenor: Dr. Norbert Lehming

Affiliation: Department of Biological Sciences, University of Pittsburgh, United States of America

Date: Wednesday, 16 April 2008 @ 11:00AM  4:00PM
           (Please take note of the change in time.)

Abstract:
The extraordinary ability of Mycobacterium tuberculosis (Mtb) to persist during prolonged chemotherapy has been the biggest hurdle in a short and effective treatment of TB. In a novel approach to understand the persistence of Mtb I found that bacilli in biofilms are significantly more tolerant to antibiotic stress as compared to their planktonic counterparts.

This led me to further investigate the molecular basis of biofilm development in Mtb and a closely related species M. smegmatis. Using a combination of genetic and biochemical tools and aided by the techniques of functional genomics, such as microarrays and proteomics, I identified two regulatory mechanisms during the development of M. smegmatis biofilms.

First, a GroEL-1 dependent regulation of mycolic acid synthesis and matrix development during biofilm maturation (Ojha et.al., Cell, 2005, p 861) and second, an iron dependent growth regulation in the early developmental stages (Ojha and Hatfull, Mol. Micro., 2007, p 468).

In another study, I observed that development of Mtb biofilms has distinct genetic and environmental requirements that are not essential for planktonic growth. Furthermore, manipulations of these conditions have direct consequences not only on biofilm formation but also on the development of drug tolerant persisters (manuscript communicated). My future interest is to study the regulatory mechanisms of mycobacterial biofilm development with an aim of identifying drug targets that can be exploited to reduce the frequency of persisters.

During the first few years I will characterize the genetic and environmental factors that control the growth of mycobacterial biofilms- in particular the role of iron in the early developmental stages. From the perspective of basic science, I am interested in fundamental questions about microbial adaptation in a dynamic environment within a complex multicellular structure.

Topic: Development of effective vaccines against Enterovirus 71 (EV71)
Speaker: Mr. Foo Guang Wei Damian, PhD Candidate
Convenor: Dr. Sylvie Alonso

Affiliation: Department of Microbiology, National University of Singapore

Date: Tuesday, 29 April 2008 @ 3:00PM

PhD Open Seminar – Thesis Defense

Topic: Effects of the histones and histone-interactive partners on transcription regulation
Speaker: Ms. He Hongpeng
Convenor: Dr. Norbert Lehming

Affiliation: Department of Microbiology, NUS

Date: Monday, 10 March 2008 @ 3:00PM

*Update: This seminar has been cancelled.

Topic: Messenger RNA cap formation: a potential anti-viral target in negative strand RNA viruses
Speaker: Dr. Li Jianrong

Affiliation: Department of Microbiology & Molecular Genetics Harvard Medical School USA

Date: Wednesday, 12 March 2008 @ 11:00AM

Abstract:
Non-segmented negative-strand (NNS) RNA viruses comprise a number of significant human, animal, and plant pathogens. Examples of NNS RNA viruses include rabies virus, measles virus, canine distemper virus, human respiratory syncytial virus, and Newcastle disease virus, as well as the highly lethal Ebola and Marburg viruses and the newly emerged Nipah and Hendra viruses.

For many of these viruses, there are no effective vaccines or antiviral drugs. NNS RNA viruses utilize a common strategy in gene expression. Viral genomic RNA encapsidated with the nucleocapsid (N) protein to form an N-RNA complex serves as a template for transcription as well as genome replication. The N-RNA complex is recognized by the RNA dependent RNA polymerase (RdRp), whose major components, are the large protein catalytic subunit (L) and the cofactor phosphoprotein (P), to synthesize uncapped leader RNA and capped, methylated, and polyadenylated mRNA. Messenger RNA cap formation of NNS RNA viruses has evolved an unconventional mechanism in which 5' monophosphate RNA is transferred to GDP acceptor by a polyribonucleotidyltransferase.

Working with vesicular stomatitis virus (VSV), we have identified a new motif in conserved region V (CRV) of large polymerase protein plays an essential role in mRNA cap formation. Using a genetic and biochemical approaches, we found that mRNA cap methyltransferase activities are also unique. A single methyltransferase active site in the conserved region VI (CRVI) of large polymerase protein that is essential for both guanine-N-7 and 2’-O methyltransferases. Furthermore, these two methyltransferases share a single S-adenosylmethionine (SAM) binding site.

We also demonstrated that compounds that inhibited viral mRNA methylation diminished virus replication, and that methyltransferase defective VSV mutants are highly attenuated in cell culture. Taken together, these results suggest that mRNA cap formation is an attractive anti-viral target in NNS viruses. A model consistent with these results will also be discussed.

PhD Open Seminar – Thesis Defense

Topic: Development of molecular diagnostics and antiviral therapy against Enterovirus 71 (EV71)
Speaker: Mr. Tan Eng Lee
Convenor: Assoc. Prof. Vincent Chow

Affiliation: Department of Microbiology, NUS

Date: Monday, 24 March 2008 @ 2:00PM

Topic: Development of Anti-Viral Strategies for Dengue and West Nile Viruses
Speaker: Dr. Justin Chu J.H. and Lee Kuan Yew Fellow
Convenor: Dr. Norbert Lehming

Affiliation: Department of Microbiology, NUS

Date: Wednesday, 13 February 2008 @ 11:00AM  

Abstract:
Both dengue and West Nile (WNV) viruses are mosquito-borne flaviviruses that represent important emerging infectious diseases and pose international health concern.  Currently, there is no effective vaccine or anti-viral drugs for these flavivirus infections.

In our first approach, we focused on the characterization of the receptor-binding domain of the West Nile virus envelope (E) protein as a potential target for the development of a subunit vaccine.  Domain III of the WNV E protein was expressed as a recombinant protein and its potential as a subunit vaccine candidate was evaluated in BALB/C mice. This part of our study constitute a proof-of-concept demonstrating that the recombinant WNV E DIII protein delivered in combination with CpG adjuvant to mice generated a Th1 immune response type against WNV and can serve as a potential vaccine to prevent WNV infection.

The alternative approach focused on the development of an effective high-throughput anti-dengue screening platforms.  Towards this end, we have developed a high content imaging platform for dengue virus infection and this platform has been used to screen a structurally diverse collection of bioactive small molecule library.  A number of potential small molecule inhibitors are identified and their effects in dengue virus biology will be presented.  These results indicated that cell-based screening platform may serve as powerful tools in identification of virus and cellular targets and might be the most expeditious route to new anti-dengue therapeutics.

Topic: A tale of two centrins
Speaker: Dr. Cynthia He Yingxin and Assistant Professor

Affiliation: Department of Biological Science, NUS

Date: Wednesday, 20 February 2008 @ 11:00AM  

Abstract:
Centrins are small calcium-binding proteins associated with centrosomes, spindle pole bodies and basal bodies. These highly conserved proteins have been implicated in several cellular functions including organelle duplication, cell signaling and mRNA transport.  In the protozoan parasite Trypanosoma brucei, three Centrins have been found essential for parasite growth. 

Centrin1 is present on the basal bodies which seed the flagellum used for cell locomotion. Centrin2 and Centrin4 are additionally present on a bi-lobed structure closely associated with the single Golgi apparatus in these cells. Interestingly, despite their similarity in sequence and localization, Centrin2 and Centrin4 have very different effects on Golgi duplication and cell division. These differences and possible mechanism will be discussed.

PhD Open Seminar – Thesis Defense

Topic: Mutational analysis of the TATA-binding protein (TBP) in Saccharomyces cerevisiae
Speaker: Ms. Chew Boon Shang
Convenor: Dr. Norbert Lehming

Affiliation: Department of Microbiology, NUS

Date: Friday, 15 February 2008 @ 2:00PM

PhD Open Seminar – Thesis Defense

Topic: Development of a novel Toll-like receptor-based two-hybrid assay for detecting protein-protein interactions and its application in the study of CD14 dimerization and FcyR activation
Speaker: Ms. Linda Wang
Convenor: Assoc. Prof. Lu Jinhua

Affiliation: Department of Microbiology, NUS

Date: Monday, 25 February 2008 @ 3:00PM     

Topic: Staphylococcus aureus and its cell envelope in microbe/host interaction
Speaker: Prof. Andreas Peschel

Affiliation: Cellular and Molecular Microbiology
University of Tubingen (Germany)

Date: Wednesday, 9 January 2008 @ 11:00AM

Abstract:
The skin of humans and warm-blooded animals represents an ecosystem for more than 30 staphylococcal species, which are highly specific for certain host organisms and even certain areas of the skin. Staphylococcus aureus, found in the anterior nares of 30% of the human population, is distinguished by a large number of virulence factors and represents one of the most frequent and dangerous bacterial pathogens.

Many key aspects of staphylococcal physiology, virulence, and immune recognition have remained elusive. The bacterial cell envelope represents a highly variable interface for interactions with environment, other microorganisms, or host factors. Complex macromolecules such as teichoic acids, peptidoglycan, membrane lipids, and surface proteins play crucial roles in many aspects of bacterial physiology and host interaction.

We are studying S. aureus binding to host cells, resistance to innate antimicrobial molecules, and recognition by immune cells by combining molecular biology, biochemistry, cell biology, and chemical analytics. Using staphylococci as model organisms, our research should reveal general principles of microbe/host interaction and may enable novel strategies for preventing and combating microbial infections.

Topic: Coronaviruses found in Hong Kong
Speaker: Prof. Kwok Yung Yuen

Affiliation:State Key Laboratory of Emerging Infectious Diseases, Department of Microbiology, Research Centre of Infection and Immunology
University of Hong Kong (Hong Kong, China)

Date: Tuesday, 29 January 2008 @ 10:30AM

Abstract:
This talk will be a comprehensive review of our research on new coronaviruses including HKU1 and SARS coronavirus (Clinical Microbiology Reviews 2007; 20:660-694).

Venue
Seminar Room @ Level 3
Department of Microbiology
YLL School of Medicine
National University of Singapore
Block MD4, 5 Science Drive 2
Singapore 117597

All Are Welcome!