[Protective antibody response to recombinant fragments of Plasmodium falciparum apical membrane antigen 1]

To determine the role of putative apical membrane antigen (AMA)1 domains in inducing protective immunity and to provide basis for selection of vaccine applicable segments.

Encoding gene segments of AMA1 were amplified and cloned into pET prokaryotic expression vectors. Recombinant proteins were expressed and purified. Groups of BALB/c mice were immunized by using recombinant protein in Freund's adjuvant, and the IgG titer and specificity of the immune sera were analyzed by IFA and Western blotting. Efficiency of the immune sera in inhibiting Plasmodium falciparum in vitro growth was evaluated.

Recombinant AMA1 fragments including the entire ectodomain E and subdomain I + II, I, II and III were successfully expressed and purified. Different levels of antibody were induced in mice by individual proteins and all the immune sera recognized native antigen in the parasites. Sera from protein E and I + II immunized mice inhibited the growth of parasites.

The integrality of the ectodomain of AMA1 determines the conformation of the protective antibody epitopes, and these protective epitopes distribute mainly in the subdomain I.