NATURALLY ACQUIRED HUMAN-ANTIBODIES WHICH RECOGNIZE THE FIRST EPIDERMAL GROWTH FACTOR-LIKE MODULE IN THE PLASMODIUM-FALCIPARUM MEROZOITE SURFACE PROTEIN-1 DO NOT INHIBIT PARASITE GROWTH IN-VITRO

Merozoite surface protein 1, one of the major surface proteins of the invasive blood stage of the malaria parasite, is a prime candidate for the development of a vaccine against the human disease. Previously, m onoclonal antibodies which both inhibited the growth of Plasmodium fal ciparum in vitro and bound to the first of two epidermal growth factor -like modules located near the carboxy terminus of the protein had bee n identified. In this study, we have used affinity chromatography on a recombinant fusion protein corresponding to the first epidermal growt h factor-like module in P. falciparum merozoite surface protein 1 to p repare antibody induced by natural infection. The antibody was purifie d from the total immunoglobulin G fraction of adult West African donor s, shown to passively confer immunity against falciparum malaria. Such affinity-purified antibodies were shown to recognize the native prote in by a number of separate criteria and to block the binding of an inh ibitory monoclonal antibody, but they failed to inhibit parasite invas ion in an in vitro growth assay. These results indicate that antibody alone is not sufficient to interfere with erythrocyte invasion.