Identification of a conserved region of plasmodium falciparum msp3 targeted by biologically active antibodies

Abstract

Antigenic and immunogenic determinants of Merozoite surface protein 3 (MSP3). Antigenicity and functional assays identified a 68-amino acid conserved domain of MSP3 as a target of biologically active antibodies. A peptide comprising amino acid residues 184-251 of SEQ ID NO: 2, may also be employed as may peptides consisting of different combinations of the MSP3 a, b, c, d, e and f peptides. Particular non-overlapping or overlapping segments of MSP3 a, b, c, d, e and f peptides may also be used. The various overlapping segments and nonoverlapping segments among the different MSP3 peptides are shown in FIG. 6. MSP3 determinants include targets of antibody-dependent cellular inhibition (ADCI) which is a protective mechanism against Plasmodium falciparum malaria. Six overlapping peptides were derived from the C-terminal end of the MSP3 polypeptide. Each of these peptides defined at least 1 non-crossreactive B cell epitope and contained T helper epitopes. Distinct patterns of antibody responses, by level and IgG subclass distribution, were observed to MSP3 peptides in inhabitants of a malaria-endemic area. Antibodies affinity purified toward each peptide differed in their functional capacity to mediate parasite killing in ADCI assays: 3 of 6 overlapping peptides had a major inhibitory effect on parasite growth. Passive transfer of anti-MSP3 antibodies in vivo in a P. falciparum mouse model confirmed the functional properties of antibodies to these MSP3 determinants.

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