Detailed analysis of T cell responses from individuals enrolled in vaccinia virus vaccine trials may dramatically improve our understanding of the effects of dilution on vaccine immunogenicity and on the relationship of cell-mediated immunity to protection from adverse events following immunization. Our experiments will begin to address the level of cell-mediated immunity elicited in naive adults following vaccination with the Aventis Pasteur smallpox vaccine. Furthermore, these studies will establish a paradigm in which researchers can begin to incorporate improved measures of cell-mediated immunity in clinical environments, generating data that will provide useful surrogate biomarkers of immune responses related to adverse events or protection. Specifically, we will test the hypothesis that the lack of a vigorous response of host T cells to immunodominant cytolytic T cell epitopes following primary immunization is associated with adverse events that are related to failure to clear virus shedding rapidly. Previous work examining cell-mediated immunity to vaccinia virus during clinical vaccine trials is very limited. Small studies have examined the effects of smallpox vaccination and identified that human CTL memory responses to vaccinia virus do occur. Much of the work performed to date examining CM1 responses in humans to specific antigens/viruses have been performed using bulk culture proliferation techniques and standard cytotoxicity assays. While these assay provide a measure of T cell responsiveness to specific antigens, they fail to delineate which of the subsets of T cells are involved in protective memory responses or are associated with adverse events. We will examine many of these questions by taking advantage of new technology that allows for examination of T cell responses at the single cell level, and in an immunodominant epitope specific manner. ? ?
