NUCLEOTIDE-SEQUENCE ANALYSIS AND EPITOPE MAPPING OF THE MEROZOITE SURFACE PROTEIN-1 FROM PLASMODIUM-CHABAUDI CHABAUDI AS

The complete nucleotide sequence of the gene encoding the merozoite su rface protein 1 (MSP-1) from the rodent malaria parasite Plasmodium ch abaudi chabaudi AS has been determined by direct sequencing of overlap ping PCR derived fragments. Comparison of the P. c. chabaudi AS nucleo tide sequence with the previously published P. c. chabaudi IP-PCI sequ ence indicates that although the MSP-1 gene of these two P. c. chabaud i strains is highly conserved, with sequence identity often approachin g 100%, interspersed throughout the molecule are 5 regions of divergen ce. This is at variance with published data which suggested that the P . c. chabaudi AS and P. c. chabaudi IF-PCI MSP-1 sequences are largely identical. Epitope mapping studies with a panel of anti-P. c. chabaud i AS MSP-1 monoclonal antibodies demonstrate that whilst most of these mAbs recognise epitopes at the N-terminus of the MSP-1 molecule, two mAbs, including one capable of inhibiting challenge infections in mice in an in vivo passive transfer assay, recognise epitopes which map to the C-terminus.