A protective merozoite protein of Plasmodium falciparum shares an epitope with surface antigens of Paramecium.
A Plasmodium falciparum cDNA expression clone, lambdaPf9, had been identified earlier as a protective epitope, using anti-lambdaPf9 antibodies and combinatorial phagotopes. A segment of the Pf9 gene showed homology with Paramecium immobilization surface antigens such as 51B, 51A and 156G. A synthetic Pf9-peptide was designed from this region, and specific antibodies were raised. Each of these anti-Pf9 antibodies and combinatorial reagents, as well as anti-Paramecium 51B antibodies, recognized the Pf9-peptide on ELISA, and the same protein band in parasite immunoblots. The P. falciparum protein was released from the merozoite membrane fraction on treatment with PI-PLC, indicating the presence of a GPI anchor. Anti-Pf9-peptide antibodies specifically inhibited the growth of P. falciparum in culture. Immunofluorescence assays showed the reactivity of anti-Pf9-peptide sera with P. falciparum merozoites and gametocytes, as well as on the surface of Paramecium tetraurelia. The Pf9-peptide was able to induce proliferation of splenic lymphocytes obtained from mice infected with the rodent malarial parasites Plasmodium berghei and Plasmodium yoelii. These results point towards Plasmodium Pf9 as a conserved novel protective protein, sharing an epitope with Paramecium surface antigens.
Sehgal
A
A
Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India.
Singh
N J
NJ
Chakraborty
T
T
Sharma
S
S
D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D000953:Antigens, Protozoan / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D015153:Blotting, Western; D049109:Cell Proliferation; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology*; D019085:Fluorescent Antibody Technique, Direct; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016805:Paramecium tetraurelia / Q000276:immunology*; D010446:Peptide Fragments / Q000276:immunology; D010716:Phosphatidylinositols / Q000276:immunology; D010963:Plasmodium falciparum / Q000276:immunology*; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D010738:Type C Phospholipases / Q000276:immunology
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D000954:Antigens, Surface; D000939:Epitopes; D010446:Peptide Fragments; D010716:Phosphatidylinositols; D010738:Type C Phospholipases