T cells, dendritic cells and the human immune response to viruses and vaccines
The work presented in this thesis investigates human immune responses to measles virus (MV). Identification of potential MV T cell epitopes for use as part of a new generation component vaccine could overcome problems associated with live vaccines in early life. HLA-A2*0201-restricted epitopes, both predicted sequences and previously identified epitopes, were used to stimulate peripheral blood samples from immune adult donors. Responses were investigated using the IFNy ELISpot. This approach failed to identify dominant epitopes. Therefore methods of enhancing presentation were investigated. To screen for immunodominant epitopes, overlapping 15mer peptides from 3 major MV proteins F, H and NP were used, looking for responses to peptide pools and individual peptides. Although some responses were seen this did not identify any dominant epitopes. In vivo boosting of the response was undertaken by vaccinating HLA-A2 individuals with MMR vaccine. PBMC and serum samples were stored from several time points' pre and post vaccination. Cell phenotyping, serology and response to peptides, along with in vitro expansion of antigen specific cells, were used to assess response in vaccinees. In vitro expansion of cells responding to MV proteins was to be achieved using adenoviral vectors containing cDNA coding for individual MV proteins. This might allow expression of antigen in autologous dendritic cells (DC) via the natural route of infection without encountering the cytopathic effect of live MV on DCs. This work, although unsuccessful, led to the observation that adenovirus-infected DCs suppress T cell proliferation, leading to a novel body of work looking at the effects of adenoviral infection on human DCs. In parallel with this work, similar methodology was used to investigate T cell responses to an OMV based meningococcus B vaccine in vaccinated donors. However it transpired that this vaccine did not stimulate an immune response in the majority of donors investigated.