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Consortium to Analyze Tolerogenic Dendritic Cells in Respiratory Syncytial Virus Infection
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PI: John Connolly
Funding Organization: Dana Foundation
Project Start: July 1, 2006
Project End: June 30, 2009
Abstract:
There is a need for novel therapeutic approaches in diseases associated with an excess of immune response such as autoimmune disease or transplantation. Indeed, current therapies are largely symptomatic and based on non-specific immunosuppressive regimes. Dendritic cells (DCs) represent attractive candidates for such therapies owing to their capacity to regulate the development and polarization of an adaptive immune response. DCs have the unique ability to induce primary immune responses. In addition, emerging evidence indicates that DCs control immune tolerance.
Indeed, distinct subsets of DCs exist with unique capacities to induce both T-cell anergy and the activation or generation of regulatory T-cells. Viruses and tumors have developed multiple strategies to subvert immune effectors by altering DCs survival, maturation and function. Therefore, we surmised that by studying the interactions between viruses and DCs we will be able to identify specific pathways/molecules rendering tolerogenic DCs. These molecules can then be used to reach our overall goal, i.e., to develop tolerogenic DC therapy for autoimmune disease and transplant rejection.
Respiratory syncytial virus (RSV) is the leading respiratory pathogen in infants and young children worldwide. Viral exposure does not induce protective immunity and repeated infections continue to occur as children get re-exposed to the same viral strain in subsequent seasons, indicating that mechanisms may exist for viral subversion of adaptive host response. Our preliminary studies indicate that children with acute RSV infection undergo a transient state of immune suppression which coincides with a loss of APC function at the site of infection.
We have demonstrated that RSV exposed human myeloid DCs, but not plasmacytoid DCs, are incapable of inducing allogeneic T-cell proliferation in vitro. 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. Our hypothesis is that RSV subverts the immune response by selectively influencing the maturation of myeloid dendritic cells, inducing their conversion to tolerogenic dendritic cells.
We propose 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 1 month after resolution of viral infection. We will measure 1) DCs gene expression by microarray analysis.
Data acquired form 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.
We will also determine whether blocking 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.
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. This will lead to novel tolerogenic DCs that may be used for therapy of diseases associated with an excess of immune response.
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