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A novel protein antigen of the malaria parasite Plasmodium falciparum, located on the surface of gametes and sporozoites

1991; Elsevier BV; Volume: 45; Issue: 2 Linguagem: Inglês

10.1016/0166-6851(91)90086-l

1872-9428

Inge I.M.D. Moelans, Jacques F. Meis, Clemens H. M. Kocken, Ruud N.H. Konings, John G.G. Schoenmakers,

Vector-borne infectious diseases

A Plasmodium falciparum cDNA clone was isolated of which the insert is transcribed at high rates as a 1.4-kb mRNA in the sexual stages of the malaria parasite. The cDNA clone contains a copy of a non-interrupted gene which codes for a protein of 157 amino acids (MΓ = 16607). This 16-kDa protein does not contain repetitive sequences and is characterised by a putative N-terminal signal sequence, a hydrophobic membrane anchor sequence and a highly hydrophilic C-terminal region suggesting that it is an integral membrane protein. Rabbit antisera raised against a synthetic peptide covering amino acids 31–47 of the 16-kDa protein and against recombinant fusion proteins recognised the 16-kDa antigen in protein extracts of gametocytes, macrogamete/zygotes and sporozoites by Western blot analysis. The rabbit antisera also reacted with gametes, gametocytes and sporozoites in a standard immunofluorescence assay. By immunoelectron microscopy using the protein A-gold method the 16-kDa protein could be clearly visualised on the surface of macrogametes and sporozoites, whereas the antigen was not detectable in the asexual erythrocytic stages of the parasite. The 16-kDa antigen of P. falciparum therefore might have the potential to elicit a dual protective immune response against the sporozoite and sexual stage parasites.