CHARACTERIZATION OF NATURALLY ACQUIRED HUMAN-IGG RESPONSES AGAINST THE N-TERMINAL REGION OF THE MEROZOITE SURFACE PROTEIN-1 OF PLASMODIUM-VIVAX

The primary structure of the merozoite surface protein 1 of Plasmodium vivax (PvMSP-1) revealed the existence of conserved and polymorphic b locks of the protein among different Plasmodium species. To characteri ze the naturally acquired IgG antibody responses to the PvMSP-1 molecu le, the entire N-terminal portion of this protein was expressed as 10 overlapping glutathione S-transferase fusion proteins. The affinity-pu rified recombinant products were tested by enzyme-linked immunosorbent assay and Western blot against the sera of malaria patients from the state of Rondonia, Brazil. We found that the majority of these sera di d not contain IgG antibodies recognizing recombinant proteins expressi ng exclusively interspecies conserved blocks of the molecule. In contr ast, a high proportion of these same sera reacted against recombinant products expressing interspecies polymorphic regions of this protein. The poor B cell immunogenicity of the interspecies conserved blocks of the PvMSP-1 molecule most Likely reflects important and unknown struc tural or functional features of these regions.