Studies in owl monkeys leading to the development of a synthetic vaccine against the asexual blood stages of Plasmodium falciparum.

During the development of a synthetic vaccine for human use against the asexual blood stages of Plasmodium falciparum, monkey trials were performed to assess safety, immunogenicity, and protectivity. We determined the minimal infective dose of the P. falciparum FVO strain, the kinetics of the immune response induced by vaccination with the synthetic peptide mixture (S7 + S12 + S17) or the synthetic hybrid polymeric protein SPf66, and the induction of protective immunity against the experimental challenge with 2 P. falciparum strains. A clear boosting effect was observed, determined by the increased antibody titers against synthetic peptides S7, S12, S17, and SPf66, and by improvement in the protective immune response against the challenge. These studies suggest that either the peptide mixture or the synthetic hybrid polymeric protein are excellent choices for the development of a vaccine against P. falciparum.