Plasmodium falciparum: Variations in the C-terminal cysteine-rich region of the merozoite surface protein-1 in field samples among Indian isolates

Lalitha, P. V., Malhotra, P., Chattopadhyay, R., and Chauhan, V. S. 1999. P lasmodium falciparum: Variations in the C-terminal cysteine-rich region of the merozoite surface protein in field samples among Indian isolates. Exper imental Parasitology 92, 12-18. The cysteine-rich C-terminal region of the merozoite surface protein-1, MSP-1(19), of Plasmodium falciparum has been t he most promising vaccine target antigen to date, based on protective immun ization studies with recombinant proteins in mice and monkey models. To be further developed as a vaccine candidate, it is essential to study its sequ ence heterogeneity in field isolates from diverse geographical areas. We ha ve analyzed the DNA sequences encoding the C-terminal region of P. falcipar um MSP-1 (1526-1744 aa, corresponding to part of the 16th and all of the 17 th blocks) of 16 isolates from different regions in India. The PNG-MAD20 ty pe of MSP-1 sequence predominated in this subcontinent. The MSP-1(19) regio n as usual was found to be highly conserved, with amino acid variations at four positions. Based on these variations, only three MSP-1(19) forms (Q-KN G, E-KNG, and E-TSG, a novel variant) were detected among these isolates. T he two MSP-119 variant forms (Q-KNG and E-TSG) were expressed in Escherichi a coil as histidine-tagged polypeptides and were characterized immunologica lly to corroborate the sequence data. (C) 1999 Academic Press.