The discovery and validation of HLA-restricted cytotoxic and helper T cell epitopes derived from the Severe Acute Respiratory Syndrome coronavirus (SARS CoV) represents a significant challenge because of the large genome size and because of the extreme polymorphism of HLA alleles. Herein, we propose to combine bioinformatic approaches and high throughput MHC- peptide binding assays to identify epitopes restricted by HLA class I and class II molecules representative of >95% of the general population, irrespective of ethnicity. These epitopes will be further validated with in vivo and in vitro immunogenicity studies utilizing HLA transgenic mice and human PBMC from healthy unexposed donors. Animal models are likely to play a vital role in the development of SARS specific vaccines and diagnostics. Accordingly, we also plan to identify epitopes presented by mouse and human MHC molecules expressed in human MHC transgenic mice. In the final part of this application, we propose to explore development of a multi-epitope SARS vaccine construct. This construct could be utilized by itself, or in conjunction with other vaccine constructs aimed at inducing anti-SARS antibody responses. Because the proposed approach is based on a systematic definition of the immunogenic potential of SARS-derived peptide sequences, only minimal use of live SARS virus or biological samples from infected or convalescent individuals is required. The studies proposed herein will lead to the definition of a broad range of epitopes, facilitate the development of diagnostic reagents necessary to rigorously evaluate T cell responses associated with infection in humans, and enable the evaluation, at the level of T cell immunity, of the performance of different vaccine candidates.