Isolation from phage display libraries of single chain variable fragment antibodies that recognize conformational epitopes in the malaria vaccine candidate, apical membrane antigen-1

Phage display of single chain variable fragment (scFv) antibodies is a powerful tool for the selection of important and useful antibody specificities. We have constructed such a library from mice protected from malaria challenge by immunization with recombinant Plasmodium chabaudi DS apical membrane antigen (AMA-1). Panning on refolded AMA-1 enriched a population of scFvs which specifically bound the antigen. The single chain antibodies recognize conformational epitopes on AMA-1 from the P. chabaudi DS strain but not on AMA-1 of the 556KA strain of P. chabaudi. A subset of the antibody fragments recognized AMA-1 from the human malaria parasite Plasmodium falciparum. Nucleotide sequencing revealed that at least four unique scFv genes were selected by the panning procedure. These scFv antibodies are valuable reagents for probing the structure and function of AMA-1 and will be used to test the feasibility of using recombinant antibodies in a passive immunization therapy against malaria.