The immune system depends on its Major Histocompatibility Complex (MHC) genes to be primed to work against the invading pathogens. The MHC loads small peptides of processed antigen and presents it to T-cells (CD4+ and CD8+). During processing of antigen, not all peptides can bind to MHC. In Choga's study, his group aims to identify those peptides from HBV genotype A and D that can bind to MHC haplotypes common in Botswana. The peptides that are able to elicit a response will be used as epitope-based vaccines.