One of the key immune responders to HIV-1 infection are the cytotoxic T-Lymphocyte (CTL), which function by killing cells infected by the virus. Hence, CTLs have been targets for vaccine design and development. CTLs do not necessarily see the whole virus but see parts of viral proteins, called peptides, that are presented on the surface of infected cells. In vaccine design and development, libraries of truncated viral peptides are powerful tools for identifying peptides recognised by CTLs thus determine which part of pathogenic viral proteins can stimulate CTLs. This process of discovering immunogenic viral peptides is celled called epitope-mapping. These viral peptides can then be used in vaccine development. In this project the process of epitope-mapping will be used to determine CTL epitopes in Transmitter founder viruses (TFV). A TFV is the virus that initially causes HIV infection. Michelo and his team hypothesise that this approach will be a more efficient tool for mapping novel CTL peptides recognised during early infection that are linked to viral control and could contribute to vaccine design and development.