Analysis of the stevor multigene family of Plasmodium falciparum

In their natural hosts malaria parasites cause long lasting chronic infections. This is in spite of a vigorous immune response by the host. The ability of the parasite to antigenically vary is thought to be one of the main reasons for this observation. Several multigene families have been described in the human parasite Plasmodium falciparum and they have been linked to antigenic variation and the pathology associated with malaria. The stevor multigene family of P. falciparum has only been partially characterised. Around 34 copies of the stevor gene family are found on all 14 chromosomes of the parasite genome. The overall structure and size of all stevor genes is conserved. Each gene codes for an approximately 30-40 kDa protein, consists of two exons and has 2-3 predicted transmembrane regions. In an attempt to get a better understanding of how the parasite utilises stevor, I have studied this gene family at the DNA, RNA and protein level. Stevor is transcribed during a very tight window of the parasite life cycle. However, only a subset of the genes is transcribed in cultured parasites and this is reflected in single micromanipulated parasites. Finally, there does not appear to be a direct link between stevor and var transcription. Antibodies raised against different regions of STEVOR recognise proteins of ~ 37 kDa and locate STEVOR within discrete sites (Maurer's clefts) of the infected red blood cell in late trophozoites and schizonts. Moreover, STEVOR is also expressed in gametocytes. These results suggest that STEVOR many have a novel role in P. falciparum biology