Characterization of a Plasmodium chabaudi gene encoding a protein with glutamate-rich tandem repeats

Several highly antigenic proteins containing tandem repeats rich in glutamic acid residues have been described in Plasmodium falciparum. However, relatively little information is available about analogous genes in rodent parasites. This report describes a 4.2-kb genomic DNA fragment from P. chabaudi with a deduced amino acid sequence that is predominantly glutamate-rich tandem repeats. Several different monoclonal antibodies raised against a 93-kDa P. chabaudi protein, which does not correspond to the cloned DNA fragment, recognize a recombinant protein expressed from the 4.2-kb DNA fragment. The only sequence similarities between these two genes are tandem repeats with a predominance of glutamate pairs followed by a hydrophobic residue. This repetitious-sequence motif may be the basis for the observed cross-reactivity. A similar motif has been demonstrated to be the basis for antibody cross-reactivity between glutamate-rich proteins of P. falciparum. The expression of multiple glutamate-rich proteins with cross-reacting epitopes may be a general phenomenon in Plasmodium species.