| Summary: | <p>Abstract</p> <p>Background</p> <p>The evasion of host immune response by the human malaria parasite <it>Plasmodium falciparum </it>has been linked to expression of a range of variable antigens on the infected erythrocyte surface. Several genes are potentially involved in this process with the <it>var</it>, <it>rif </it>and <it>stevor </it>multigene families being the most likely candidates and coding for rapidly evolving proteins. The high sequence diversity of proteins encoded by these gene families may have evolved as an immune evasion strategy that enables the parasite to establish long lasting chronic infections. Previous findings have shown that the hypervariable region (HVR) of STEVOR has significant sequence diversity both within as well as across different <it>P. falciparum </it>lines. However, these studies did not address whether or not there are ancestral <it>stevor </it>that can be found in different parasites.</p> <p>Methods</p> <p>DNA and RNA sequences analysis as well as phylogenetic approaches were used to analyse the <it>stevor </it>sequence repertoire and diversity in laboratory lines and Kilifi (Kenya) fresh isolates.</p> <p>Results</p> <p>Conserved <it>stevor </it>genes were identified in different <it>P. falciparum </it>isolates from different global locations. Consistent with previous studies, the HVR of the <it>stevor </it>gene family was found to be highly divergent both within and between isolates. Importantly phylogenetic analysis shows some clustering of <it>stevor </it>sequences both within a single parasite clone as well as across different parasite isolates.</p> <p>Conclusion</p> <p>This indicates that the ancestral <it>P. falciparum </it>parasite genome already contained multiple <it>stevor </it>genes that have subsequently diversified further within the different <it>P. falciparum </it>populations. It also confirms that STEVOR is under strong selection pressure.</p>
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