Recent Efforts in the Development of a Sporozoite Vaccine Against Human Malaria

Abstract

Nineteen monoclonal antibodies were produced against sporozoites of Plasmodium falciparum. They have been characterized immunochemically, as well as by isotype, CSP reactivity, and stage and species specificity. Five of these monoclonal antibodies were used to screen a genomic library of P. falciparum in the expression vector λ gt 11. Aspects of the cloning and sequencing of the gene encoding for the CS protein of P. falciparum are described. The CS gene encodes for a sporozoite surface protein which is thought to be important in eliciting protective immunity in man. The protein has regions that include a signal sequence, charged region, a series of repeating peptides in the middle of the protein, followed by another charged region and then an anchor sequence. There are also two regions of amino acid homology between the CS proteins of P. falciparum and P. knowlesi. Both the repeating region and the conserved sequences could form the basis for a vaccine. The immunogen for such a candidate vaccine could be produced in bacterial fermentation systems or by development of synthetic peptides coupled to a carrier.