Faculty
John Treanor, M.D.
Professor of Medicine and Professor of Microbiology and Immunology
Human immune responses to influenza virus, and clinical vaccine trials
Dr Treanor is the Principal Investigator and Director of the University of Rochester Vaccine and Treatment Evaluation Unit (VTEU). Recent studies have included evaluation of live attenuated influenza vaccines in infants and young children, evaluation of smallpox, anthrax and genital herpes vaccines in healthy adults, and evaluation of novel inactivated influenza vaccines and of protein-conjugate pneumococcal vaccines in ambulatory elderly adults. In collaboration with Ed Walsh and Ann Falsey, the unit also evaluates the immune response to respiratory syncytial virus (RSV) in adults using a recently described human infection model. Dr. Treanor has a long standing interest in influenza pathogenesis and vaccine development. He has collaborations with Dr. Eun-Hyung Lee and Timothy Mosmann in studies evaluating aging and the immune response to influenza vaccine, with Dr. Xi Jin on the effect of lipid supplementation on influenza vaccine responses in the elderly, and with Dr. Jan Moynihan on the effects of stress on influenza immune responses in elderly residents of nursing homes.
David Topham, Ph.D.
Associate Professor of Microbiology and Immunology in the David H Smith Center for Vaccine Biology and Immunology
T cell responses to influenza virus infection
The specter of a pandemic caused by avian influenza virus highlights the need to identify possible mechanisms of immune protection from emerging strains of the flu virus. We cannot accurately predict which influenza will emerge as the next pandemic, making it difficult to select and manufacture sufficient conventional vaccine to elicit protective homotypic antibodies. Protective T cell mediated heterosubtypic immunity to influenza is an established paradigm in animal models, but is not well documented in humans. Though it is likely that heterosubtypic immunity to influenza exists in humans, there is little evidence of its specificity, and the reasons why it may or may not be protective are unclear. Our lab has shown that optimal CD8 T cell mediated heterosubtypic immunity is provided when T cells are retained in the lung tissue and airways via their interaction with collagen via the VLA-1 collagen receptor (Ray et al., 2004). One hypothesis is that heterosubtypic immunity to influenza fails in humans because of insufficient memory in the lung tissue. Having these T cells in place would not prevent infection, but could limit the duration and magnitude of viral replication. This could be the difference between life and death when encountering an emerging pandemic strain of influenza. Conventional influenza subunit vaccination is designed to generate antibodies, and does not strongly stimulate tissue-memory. Future strategies for influenza vaccine design should target both antibodies and cross-reactive lymphoid and tissue memory T cells. Our goals are to better understand potentially heterosubtypic immune responses to influenza and begin to develop the means to evaluate and, in the future, promote optimal vaccination strategies. To accomplish these goals, the Topham lab has established assays for detailed analysis of cell-mediated immunity (CMI) against influenza in humans, and has developed improved animal models for studying CD4 T cell mediated influenza immunity in mice. Comprehensive assay systems are established to target CD4 and CD8 T cells, and B cells responding to influenza virus, viral hemagglutinin, or influenza vaccines.
Ongoing Research Projects
Immune protection against viral infections: The Topham lab is committed to understanding immune protection from virus infections. Since most viral infections occur outside of the blood and lymphatic organs, we are focused on the regulation of lymphocytes in extralymphoid tissues. This expertise in the regulation of extralymphoid T cells was called upon when I was asked to write a commentary (Topham and Crispe, 2003) on a paper in Immunity that showed extralymphoid CD8 T cells were resistant to apoptosis compared to lymphoid T cells.
Function of VLA-1 on CD8 and CD4 T cells: CD4 and CD8 memory T cells become established in extralymphoid tissues following a virus infection. However, the mechanism by which these cells could be retained and survive in these environments was not known. In 2004, Steven Ray, a graduate student in the lab, published a paper in Immunity showing that influenza-specific CD8 T cells were retained in the lung and other extralymphoid tissues by the collagen-binding integrin VLA-1 (Ray et al., 2004). Furthermore, CD8 T cells that express this integrin were found to be less apoptotic, suggesting that VLA-1 might promote survival of these cells.
Regulation of T cell survival via interaction with extracellular matrix: Dr. Martin Richter (postdoc) is performing experiments to test the hypothesis that VLA-1/collagen ligation inhibits apoptosis of the T cells. He has shown that VLA-1+ T cells have reduced caspase 8 activity, suggesting this as a mechanism to inhibit activation or death receptor mediated cell death in the tissues. Martin has also developed fluorescent immunohistochemical techniques to determine the distribution of collagen subtypes, antigen-specific CD8 T cells, and viral antigens, and caspase activity in lung tissue. These methods will be used to test the hypothesis that T cell localization in the lung environment is determined by the distribution of collagen subtypes.
CD4 T cell mediated immune protection from influenza: Tim Chapman (graduate student) has developed a system to track antigen-specific CD4 T cells during influenza infection by using ovalbumin specific TCR transgenic CD4 T cells and a recombinant influenza virus expressing the OVA epitope seen by the T cells (Chapman et al., 2005). Tim’s project is focused on determining the relative contributions of lymphoid and extralymphoid CD4 memory T cells to influenza immunity, and he has recently contributed to a review on the subject (Topham et al., 2006)
Function of VLA-2 on NK cells and T cells: VLA-2 is another collagen-binding integrin thought to promote migration of lymphocytes in matrix. VLA-2 is constitutively expressed on NK cells and upregulated on T cells in the lung during viral infection and asthma. Sarah Austin (graduate student) has recently shown that inhibition of VLA-2 compromised control of mCMV in mice, and inhibited the translocation of NK cells into influenza virus-infected airways. She will be pursuing experiments to test the hypothesis that VLA-2 regulates lymphocyte invasion of extralymphoid tissues by stimulating cell migration.
Collateral damage and immunoregulation of CD8 T cells in the liver: In studying the fate of virus-specific CD8 T cells in the extralymphoid environments, we observed that T cells accumulated very early and to a large magnitude in the liver. Furthermore, this CD8 T cell accumulation caused a frank hepatitis and hepatocyte injury in both mice and humans infected with influenza (Polakos et al., 2006). Inhibition of the accumulation or interaction with liver macrophage both abrogated hepatitis and increased the number of CD8 T cells in all tissues. The hypothesis that the liver selective traps activated virus-specific CD8 T cells in acute extrahepatic infections and regulates the number of these cells in circulation, and that the CD8 cells mediate liver injury is being tested by Noelle Polakos (graduate student).
Cell mediated immune responses to vaccines in humans: In collaboration with Dr. John Treanor, director of the Vaccines and Treatments Evaluation Unit (VTEU) we are participating in expanded studies of cell mediated immune responses in humans participating in vaccine trials. The first example of this collaboration was a study of T and B cell responses to smallpox vaccine (vaccinia). In particular, we examined the relative quality of recall responses in individuals who had been recently vaccinated versus those that had been vaccinated decades earlier. Currently we are collaborating on a study of a new AMA-1 malaria vaccine using synthetic CpG adjuvants. In addition we are studying secondary immune responses to experimental H5 influenza vaccines in human subjects previously vaccinated with an earlier version of a vaccine against H5 influenza.
1. Chapman, T. J., Castrucci, M. R., Padrick, R. C., Bradley, L. M., and Topham, D. J. (2005). Antigen-specific and non-specific CD4(+) T cell recruitment and proliferation during influenza infection. Virology 340, 296-306.
2. Polakos, N. K., Cornejo, J. C., Murray, D. A., Wright, K. O., Treanor, J. J., Crispe, I. N., Topham, D. J., and Pierce, R. H. (2006). Kupffer cell-dependent hepatitis occurs during influenza infection. Am J Pathol in press.
3. Ray, S. J., Franki, S. N., Pierce, R. H., Dimitrova, S., Koteliansky, V., Sprague, A. G., Doherty, P. C., de Fougerolles, A. R., and Topham, D. J. (2004). The collagen binding alpha1beta1 integrin VLA-1 regulates CD8 T cell-mediated immune protection against heterologous influenza infection. Immunity 20, 167-179.
4. Topham, D. J., Chapman, T. J., and Richter, M. (2006). Lymphoid and extralymphoid CD4 T cells that orchestrate the anti-viral immune response. Exp Rev Clin Immunol in press.
5. Topham, D. J., and Crispe, I. N. (2003). Contrasting urban and rural lifestyles of memory CD8+ T cells. Immunity 18, 584-586.
Tim Mosmann, Ph.D.
Professor of Microbiology and Immunology
Director, David H Smith Center for Vaccine Biology and Immunology
T cell regulation of host responses to influenza virus infection
Steve Dewhurst Ph.D.
Professor of Microbiology & Immunology and of Oncology
Baek Kim Ph.D.
Assistant Professor of Microbiology and Immunology
Role of avian
flu RNA polymerase kinetics and fidelity in viral genomic mutagenesis,
evolution and host species change:
Genetic drift in influenza viruses is responsible for antigenic changes
in hemagglutinin and neuraminidase proteins and is likely responsible
for the ability of the current H5N1 avian influenza species to make the
host species transition to humans, with fatal consequences.
Genetic drift implicates the viral replication machinery as
mechanistically
involved in this process. The viral replication machinery
must be
capable of frequent mutation synthesis and massive viral replication in
order to generate viral quasi-species capable of making this host
specificity switch. Our laboratory has initiated a series of
projects involving biochemical analysis and reverse genetic approaches
aimed at understanding the involvement of avian influenza virus RNA
polymerase kinetics and error rates in viral genetics and evolution.
Toru Takimoto, DVM, Ph.D.
Assistant Professor of Microbiology and Immunology
Influenza virus determinants of host adaptation
The introduction and subsequent spread in the human population of Influenza A virus with novel hemagglutinin (HA) and neuraminidase (NA) subtypes is a serious threat to human health because of the lack of immunity against these viruses. Recent human fatal infections caused by highly pathogenic avian influenza A viruses (H5N1) highlighted the continuous threat of new pathogenic influenza viruses emerging from a natural reservoir in birds. The molecular determinants and related mechanisms that make certain influenza viruses highly pathogenic for mammalian species, including humans, remain poorly understood, although recent evidence has suggested that the viral polymerase proteins play a key role in this process. In my lab, we are studying the role of polymerase and matrix proteins in host adaptation of influenza A viruses. Using a reverse genetics system, we are analyzing mutations and molecular mechanisms associated with viral adaptation to mammalian hosts. Our goal is to reveal the molecular basis of mammalian host adaptation of avian influenza A viruses.
Andrea J. Sant, Ph.D.
Professor of Microbiology and Immunology in the David H Smith Center for Vaccine Biology and Immunology Immunodominance of CD4 T cell responses to influenza virus
Dr. Sant is funded by NIAID to develop and implement stragies to
elucidate the molecular mechanisms that control immunodominance in
CD4 T cell responses to forgeign antigens. Dr. Sant's laboratory has
developed expertise in epitope identification and T cell ELISPOT assays
to quantify CD4 T cell responses as well as biochemical assays to
elucidate the critical features of peptide:MHC class II interactions
that regulate the ability of those complexes to elicit CD4 T cell
responses in vivo. Because of the striking findings made thus far in
these studies, Dr. Sant has recently been funded by a R21 award to
initiate studies of human T cell responses to influenza.
1. Nanda, N. and A.J. Sant. 2000. DM dictates crypticity and immunodominant fate of T cell epitopes. J. Exp. Med. 192:781.
2. Sant, A.J. and J. Yewdell 2003. Editorial Overview: Antigen Processing and Recognition. Current Opinion Immunology 18:66.
3. Chaves, F, Hou, P. and A. J. Sant, 2005 Replacement of the membrane proximal region of I-Ad MHC class II molecule with I-E derived sequences promotes production of an active and stable soluble heterodimer without altering peptide-binding specificity. J. Immunol. Methods. 300:74.
4. Lazarski, C, Chavez, F, Jenks, S, Wu, S Richards, K, Weaver, J.M. and A.J. Sant. 2005. The kinetic stability of MHC:class II complexes is a key parameter that dictates immunodominance. Immunity 23:29-40.
5.. Sant, A.J. Chaves, F.C., Jenks, S, Richards, K., Zschoche, P., Weaver, J.M. and C. Lazarski. 2005. The relationship between immunodominance, DM editing and the kinetic stability of MHC class II:peptide complexes. Immunological Reviews, 207:261-278.
6.. Lazarski, C, Chaves, F, Jenks, S, A.J. Sant. 2006. The impact of DM on MHC class II-restricted antigen presentation can be altered by manipulation of MHC:peptide kinetic stability J. Exp. Med, In press
7. Chaves, F.A, Richards, K.A., Torelli, A, Wedekind, J., and A.J. Sant. 2006. Peptide-binding motifs for the I-Ad MHC class II molecule: Alternate pH dependent binding behavior. Biochemistry, in press
B. Paige Lawrence, Ph.D.
Associate Professor,
Department of Environmental Medicine
(Dr Lawrence is newly recruited and starts at URSMD on 7/1/06)
A major focus of our research is defining the molecular mechanisms by which pollutants adversely affect the immune response to respiratory infection. Specific focus is currently on the pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin) and the immune response to influenza A viruses. Dioxins bind and activate a receptor called the aryl hydrocarbon receptor (AhR). The AhR is a ligand-activated transcription factor and is expressed in cells of the immune system and the lung. It is often considered an "orphan receptor," because it has been difficult to identify an endogenous ligand. However, in addition to dioxin, many other pollutants activate the AhR, including coplanar polychlorinated biphenyls (PCBs) and polyaromatic hydrocarbons (PAH), such as benzo[a]pyrene and 7,12-dimethylbenzanthracene, which are found in cigarette smoke and diesel exhaust. In addition to pollutants, many plant-derived natural compounds and tryptophan metabolites bind to the AhR. Therefore, we are exposed to AhR ligands daily through ingestion and inhalation.
It has been known for quite some time that dioxins are very potent immune suppressants, and that their toxicity is mediated by the AhR; however, the molecular mechanism is not known. Nevertheless epidemiological data suggest that exposure to pollutants that contain AhR agonists correlates with diminished host resistance, altered immune function and an increased incidence of influenza and other respiratory infections. In animals, AhR activation impairs survival following infection with influenza virus, further illustrating the relationship between exposure to AhR ligands and altered host resistance to infection.
Our specific focus is currently on defining the molecular mechanisms by which dioxin impairs the immune response to influenza virus infection. This work includes assessment of effects on innate and adaptive immune responses, and currently involves the following projects:
- Elucidating the role of the AhR in pulmonary inflammation and determining the role of the AhR in dioxin-mediated impairment of host resistance to infection;
- Determining the mechanisms by which AhR activation impairs the activation, proliferation and differentiation of virus-specific T lymphocytes; and,
- Characterizing the effects of dioxin on immunological memory.
A separate but related project involves studies to understand how developmental exposure to dioxin causes functional alterations in the immune system of the offspring. The changes observed following exposure to dioxin during development include suppressed lymphocyte expansion and differentiation, altered cytokine production, and increased inflammation in the lungs after influenza virus infection. These changes in the immune response to infection occur at developmental exposures to dioxin that cause no detectable change in hematopoiesis or the cellularity of immune organs, suggesting that inappropriate AhR activation during development interferes with the normal programming of the immune system via epigenetic mechanisms.