How Does RSV Virus Subvert Immunity, and Can This Process Be Used to Curtail Autoimmunity?

John Connolly, Ph.D.

Baylor Research Institute

Funded in June, 2006: $300000 for 3 years
LAY SUMMARY . ABSTRACT . BIOGRAPHY . HYPOTHESIS .

LAY SUMMARY

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How Does RSV Virus Subvert Immunity, and Can This Process Be Used to Curtail Autoimmunity?

This consortium will define how the respiratory syncytial virus (RSV) is able to subvert the immune system from developing protection against subsequent infections by the virus. Understanding how certain molecules block protective immunity may lead to development of a vaccine that circumvents this process. Moreover, the findings also may lead to novel ways to use these molecules to block unwanted immune responses against the body's own tissues, which occur in people with autoimmune diseases and in instances of organ transplant rejection.

RSV is a highly prevalent virus. It affects virtually all children by the age of three, some so severely that they require hospitalization. In contrast to other traditional viral infections in childhood, however, RSV does not elicit protective immunity against subsequent infections by the virus. The investigators hypothesize that RSV subverts the immune response by selectively influencing the maturation of a subset of immune system dendritic cells (called myeloid dendritic cells).

Dendritic cells ordinarily are the body's first line of defense against viruses. While still immature, and called myeloid dendritic cells, they enter the bloodstream and migrate to tissues. The myeloid dendritic cells rapidly mature when they encounter a virus. They learn the virus' structure and migrate to lymph nodes, where they teach specific immune T cells to recognize and attack the virus. Consortium investigators will undertake two sets of studies in patients' nasal mucosa and blood cells to learn how the RSV virus induces the myeloid dendritic cells to become tolerant to it and ignore it.

In the first study, researchers will work to identify the genes that produce the dendritic cells found in the respiratory tract of children infected with RSV. These genes will be compared to genes that produce mature dendritic cells in response to flu infection. In the second study, investigators will determine whether the RSV virus activates certain inhibitory receptors (molecules) on the surface of myeloid dendritic cells to prevent the cells from initiating an immune response. The investigators will determine this by studying whether the inhibitory receptors can be blocked by monoclonal antibodies made by the researchers, and whether this blockade reverses the dendritic cells' tolerance and instead activates them into action. Baylor researchers bring expertise in translational (bench to bedside) research on dendritic cells, and UT Southwestern researchers bring expertise in children's immune responses to viral infections.

Significance: If the research demonstrates that RSV prevents an immune response by inhibiting immature dendritic cells from taking action, the findings may lead to ways of preventing this process from occurring. Most importantly, if researchers learn the molecular basis for inhibiting dendritic cell responses, the findings could lead to therapies that prevent the unwanted immune attacks that occur in autoimmune diseases and immune system rejection of transplanted organs.

ABSTRACT

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How Does RSV Virus Subvert Immunity, and Can This Process Be Used to Curtail Autoimmunity?

Respiratory syncytial virus (RSV) is the leading respiratory pathogen in infants and young children worldwide. Viral infection does not induce protective immunity and repeated infections continue to occur as children get re-exposed to the same virus in subsequent seasons, indicating that mechanisms may exist for viral subversion of adaptive host response. Our preliminary studies in children with acute RSV infection suggest that RSV induces a transient state of immune suppression, which coincides with a loss of APC function at the site of infection. In vitro we have demonstrated that human myeloid DCs exposed to RSV, but not plasmacytoid DCs, are incapable of inducing allogeneic T-cell proliferation. These results suggest that RSV might have developed mechanisms to subvert the immune system by modulating dendritic cell function, leading to the state of tolerance.

Overall significance: We will define basic mechanisms and molecules involved in the interaction between RSV and DCs, and how these interactions perturb normal dendritic cell function to subvert the establishment of protective immunity.

INVESTIGATOR BIOGRAPHIES

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John Connolly, Ph.D.

John Connolly, Ph.D., is an assistant investigator at the Baylor Institute for Immunology Research (BIIR) in Dallas. He earned his Ph.D. in biochemistry from Dartmouth Medical School in 2001, where he then moved to the Department of Immunology and Microbiology as a research associate. Dr. Connolly came to BIIR in 2003. He is the director of two core facilities at the Dallas campus: the Imaging Core and the Cytokine Multiplex Core. In 2005, he received the appointment of adjunct professor of biomedical studies at Baylor University in Waco. Dr. Connolly's research focuses on the antigen processing/presentation pathways of dendritic cells and the mechanisms by which respiratory viruses evade these steps in the immune response. As director of the two core facilities, he is also involved in projects using multiplex proteomic analysis and live cell confocal, fluorescence digital imaging.

Octavio Ramilo, M.D. is a professor in the Division of Infectious Disease of the Department of Pediatrics at the University of Texas (UT) Southwestern Medical Center in Dallas, as well as professor in the Cancer Immunobiology Center at UT Southwestern. A practicing physician, Dr. Ramilo is also medical director of both clinical research and AIDS-related medical services at the Children's Medical Center of Dallas.

Dr. Ramilo earned a medical degree from Facultad de Medicina, Universidad Complutense in Madrid, Spain, where he also completed a pediatric residency at Hospital Universitario 12 de Octubre. Subsequently, he completed a fellowship in pediatric infectious diseases and additional postdoctoral research training in immunology at UT Southwestern Medical Center. An avid researcher in the immunopathogenesis of viral infections, particularly respiratory syncytial virus (RSV), Dr. Ramilo is currently principal investigator on numerous research projects, including a study of dendritic cells, RSV, and influenza infection in children for the National Institute of Allergy and Infectious Diseases of the National Institutes of Health. He is also studying the incidence rates and clinical features of human metapneumovirus infection of the lower respiratory tract in high-risk hospitalized children. In 2004, Dr. Ramilo and colleagues at UT Southwestern used a mouse model to establish a link between RSV infection and risk of developing reactive airway disease.

A prolific writer, Dr. Ramilo has authored many book chapters and monographs, and his clinical research has appeared in peer-reviewed journals that include The Journal of Infectious Diseases, Antimicrobial Agents and Chemotherapy, and The Pediatric Infectious Disease Journal. He is a frequent national and international presenter and a regular reviewer for a number of clinical journals, including The Journal of Pediatrics, Proceedings of the National Academy of Sciences of the United States of America, and Vaccine.

Certified by the American Board of Pediatrics, with a subspecialty in pediatric infectious diseases, Dr. Ramilo is a member of the American Academy of Pediatrics, the Society for Pediatric Research, and the Pediatric Infectious Diseases Society, among other professional organizations. He is a member of the board of directors of the National Pediatric Infectious Diseases Foundation.

HYPOTHESIS

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Hypothesis:
RSV subverts the immune response by selectively influencing the maturation of myeloid dendritic cells, inducing their conversion to tolerogenic dendritic cells. We propose two aims analyzing the phenotype and function of RSV-exposed dendritic cells:

Goals:
1. To analyze the phenotype of DCs present in the respiratory tract of children with RSV infection. mDCs and pDCs from the respiratory tract of patients with RSV or flu infection will be isolated during acute infection and one month after resolution of viral infection.

We will measure 1) DCs gene expression by microarray analysis. Data acquired from DCs isolated from the site of RSV infection will be compared to results obtained for DC respiratory isolates of pediatric patients with flu infection. 2) Surface expression of phenotypic markers using multicolor flow cytometry and compared with those of in vitro exposed DCs.

2: To determine whether blocking of inhibitory receptors induced by RSV would revert the mDCs function from tolerogenic to immunostimulatory.

We will 1) Determine the role of inhibitory receptors in tolerogenic function of RSV-DCs by functional blockade; 2) Generate monoclonal antibodies to high priority tolerogenic molecules upregulated by RSV; 3) Generate and characterize monoclonal antibodies to RSV-exposed DCs.