Exploiting host immunity and parasite genomics to develop a robust sub-unit vaccine against East Coast fever in cattle - Where are we?

Theileria parva, a tick-borne api-complexan protozoan parasite, causes East Coast fever (ECF) in cattle. Control of the disease by improved vaccination is believed to provide a sustainable solution. Class I MHC-restricted CD8+ cytotoxic T lymphocytes (CTL) directed at schizontinfected cells constitute the effector immune mechanism against ECF in cattle recovering from a single or multiple infection(s). Schizont antigens recognised by CTL are therefore prime vaccine candidates. We describe a rational approach used to identify 8 CTL target antigens as vaccine candidates. The genes encoding the target antigens have been engineered in plasmid DNA and viral vectors for evaluating their immunogenicity and efficacy in cattle. In a preliminary trial, five of the candidate vaccines demonstrated the capacity to induce CTL responses that correlated with survival and reduced disease severity following a lethal parasite challenge