| Summary: | <p>Abstract</p> <p>Background</p> <p>The <it>Plasmodium falciparum </it>parasite is transmitted in its sexual gametocyte stage from man to mosquito and as asexual sporozoites from mosquito to man. Developing gametocytes sequester preferentially in the bone marrow, but mature stage gametocytes are released to the bloodstream. Sexual stage parasite surface proteins are of interest as candidate target antigens for transmission blocking vaccines.</p> <p>Methods</p> <p>In this study, the transcript profiles of <it>rif </it>and <it>var </it>genes, known to encode surface antigens in asexual blood stage parasites, were investigated at different stages of 3D7/NF54 gametocytogenesis and in sporozoites.</p> <p>Results</p> <p>Gametocytes exhibited a <it>rif </it>transcript profile unlinked to the <it>rif </it>and <it>var </it>transcript profile of the asexual progenitors. At stage V, mature gametocytes produced high levels of a single <it>rif </it>gene, PF13_0006, which also dominated the <it>rif </it>transcript profile of sporozoites. All <it>var </it>genes appeared to be silenced in sporozoites.</p> <p>Conclusions</p> <p>The most prominent variant surface antigen transcribed in both gametocytes and sporozoites of 3D7/NF54 is a single variant of the RIFIN protein family. This discovery may lead to the identification of the parasites binding ligands responsible for the adhesion during sexual stages and potentially to novel vaccine candidates.</p>
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