Definition of T cell epitopes within the 19 kDa carboxylterminal fragment of Plasmodium yoelii merozoite surface protein 1 (MSP1(19)) and their role in immunity to malaria

MSP1(19) is one of the leading malaria vaccine candidates. However the mech anism of protection is not clear. To determine whether MSP1(19)-specific ef fector T cells can control parasitaemia, we analysed the specificity of T c ells induced following immunization with recombinant forms of P. yoelii MSP 1(19) and asked whether they could protect mice. There was no evidence that effector T cells were capable of protecting since: (1) immunization of mic e with yMSP1(19), but not defined epitopes, was able to induce protection; and (2) long term MSP1(19)-specific CD4(+) T cell lines were incapable of a doptively transferring protection In contrast, priming mice with the T cell epitopes resulted in a rapid anamnestic antibody response to MSP1(19) afte r either challenge with MSP1(19) or parasite. Thus, MSP1(19) contains multi ple T cell epitopes but such epitopes are the targets of helper T cells for antibody response but not of identified effector T cells capable of contro lling parasitaemia.