Vaccination with a purified blood-stage malaria antigen in mice: correlation of protection with T cell mediated immunity.

A purified 230,000 mol wt protein antigen from the lethal mouse malaria parasite Plasmodium yoelii YM which had previously been shown to be highly effective as a vaccine, was tested for its ability to stimulate specific helper T cells and T cells responsible for delayed hypersensitivity. Strong stimulation was found in both assays, but larger doses were required for delayed hypersensitivity, correlating well with the requirements for protection. It is suggested that T stimulation may be a requirement for effective protection by purified antigens in malaria.