Subset analysis of the EBV-specific CD4+ T cell response in primary and persistent infection And Characterisation of CD8+ T cell responses against CMV derived antigens protected in wild type strains of the virus

CD4+ T cell responses are critical components of the immune response to viral infections, yet unlike their CD8+ counterparts, CD4+ responses to many viral agents remain uncharacterised. The CD4+ T cell subsets involved in controlling primary and persistent EBV infection (causative agent of IM) have not been extensively studied. This investigation attempted the first systematic analysis of the CD4+ T cell response to epitopes from across the EBV genome in a subset-specific manner. It combined MHC II tetramer technology (nine epitopes) with intracellular staining for transcription factors of the Thl/Th2/Treg subsets to analyse 8 healthy and 2 IM donors. Although the analysis ofThl ffh2 subsets requires further optimisation, MHC II tetramer staining and intracellular staining were successfully combined for FOXP3. Evidence is presented for the presence of EBV-specific Treg responses, within healthy persistent carriers but the absence of such responses in acute primary IM patients. The results implicate that a lack of Tregs, in combination with other genetic factors, may play a role in IM development. Preliminary Th1 responses and negative Th2 responses in healthy and IM patients were observed. Further understanding the subsets involved in controlling EBV, will help focus therapeutic applications towards EBV-associated malignancies at specific subsets. In CMV-seropositive elderly donors virus-specific CD8+ T cells against the pp65 and IE-1 proteins can occupy up to 40% of the total CD8+ T cell pool. CMV encodes for several immunomodulatory proteins that interfere with the MHC class I antigen presenting pathway. Studies using an immunevasion-deleted virus strain (RV798) revealed a large proportion of CMV-specific T cell responses are evaded by cells infected with WT virus, but are primed in vivo. This study undertook the first functional and phenotypical characterisation of CD8+ T cells in young and elderly donors responding to CMV-derived epitopes identified using the deletion mutant. These CD8+ T cells seem to accumulate within the elderly reaching up to 32%, against a HLA-C restricted epitope, of the total CD8+ T cell pool producing IFN-y, TNF-a and l ittle IL-2. The CD8+ T cells were CD4SRA+/CDS7+/CD28-/CCR7- and therefore of the EMRA compartment. In vitro they recognised their antigen in the context of RV798 infection, but not wild type (WT) infection. In summary the CD8+ T cells specific for the 'protected' antigens studied here display very similar characteristics compared to previously studied CMV-specific CD8+ T cells. What is currently unclear is the in vivo role they play in controlling the virus