Processing of the Plasmodium chabaudi chabaudi AS merozoite surface protein 1 in vivo and in vitro.

Processing of the Plasmodium merozoite surface protein 1 (MSP-1) has been described for parasites maintained under in vitro conditions. We have now demonstrated, using CBA/Ca mice infected with Plasmodium chabaudi chabaudi AS, that MSP-1 processing also occurs in vivo. The major proteolytic cleavage sites and a processing scheme were deduced from N-terminal amino-acid sequences of the MSP-1 breakdown products. Comparison of MSP-1 processing in P. falciparum and P.c. chabaudi indicates a degree of conservation and in two cases the position of protease cleavage appears identical. Significant amounts of MSP-1 polypeptides are found in plasma during schizogony. Various aspects of MSP-1 processing including immunological and physiological reactions in the host during the critical period of schizogony can now be examined in vivo.