Plasmodium falciparum: the repetitive MSA-1 surface protein of the RO-71 isolate is recognized by mouse antibody against the nonrepetitive repeat block of RO-33.
We have expressed in Escherichia coli the nonrepetitive repeat zone of the MSA-1 surface protein of the RO-33 isolate of Plasmodium falciparum. The recombinant protein was used to immunize mice and the resulting RO-33 monospecific serum was used to screen our P. falciparum strain collection in order to recover additional alleles lacking tripeptide repeats in block 2 of MSA-1. Only 1 (RO-71) out of 30 isolates tested reacted strongly with the serum by indirect immunofluorescence assay. Surprisingly, block 2 of the RO-71 MSA-1 allele contains tripeptide repeats resembling those of the K1 isolate of P. falciparum. Additional sequence analysis of the entire DNA coding for the 80-kDa MSA-1-derived surface component did not reveal any amino acid stretches similar to block 2 of RO-33 which could rationalize the immunological cross-reactivity. We eliminated the possibility that the RO-71 culture was contaminated with RO-33 type alleles of MSA-1 by Southern blotting and PCR analysis. The RO-33-specific mouse serum used for the initial selection of RO-71 did not react with the antigen in the denatured state (Western blot). This and the sequence analysis suggest that the cross-reactive epitope in the MSA-1 protein of RO-71 is conformational. The possibility that a truncated frame-shift protein encoded by mutated MSA-1 mRNA is recognized by the serum is discussed.
Olafsson
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P
Department PRTB, F. Hoffmann-La Roche Limited, Basel, Switzerland.
Matile
H
H
Certa
U
U
D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology*; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D000954:Antigens, Surface / Q000235:genetics / Q000276:immunology; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D003429:Cross Reactions; D020066:Merozoite Surface Protein 1; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010963:Plasmodium falciparum / Q000235:genetics / Q000276:immunology*; D011498:Protein Precursors / Q000235:genetics / Q000276:immunology*; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D000954:Antigens, Surface; D020066:Merozoite Surface Protein 1; D011498:Protein Precursors; D015800:Protozoan Proteins