title: Characterization of the repertoire diversity of the Plasmodium falciparum stevor multigene family in laboratory and field isolates.
abstract: BACKGROUND
  The evasion of host immune response by the human malaria parasite Plasmodium falciparum 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 var, rif and stevor 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 P. falciparum lines. However, these studies did not address whether or not there are ancestral stevor that can be found in different parasites.
  
  
  METHODS
  DNA and RNA sequences analysis as well as phylogenetic approaches were used to analyse the stevor sequence repertoire and diversity in laboratory lines and Kilifi (Kenya) fresh isolates.
  
  
  RESULTS
  Conserved stevor genes were identified in different P. falciparum isolates from different global locations. Consistent with previous studies, the HVR of the stevor gene family was found to be highly divergent both within and between isolates. Importantly phylogenetic analysis shows some clustering of stevor sequences both within a single parasite clone as well as across different parasite isolates.
  
  
  CONCLUSIONS
  This indicates that the ancestral P. falciparum parasite genome already contained multiple stevor genes that have subsequently diversified further within the different P. falciparum populations. It also confirms that STEVOR is under strong selection pressure.
authors: Nanyang Technological University, School of Biological Sciences, Singapore, Singapore. JEB@kcs.org.uk
authors: Jane E
authors: JE
authors: Blythe
authors: Makhtar
authors: M
authors: Niang
authors: Kevin
authors: K
authors: Marsh
authors: Anthony A
authors: AA
authors: Holder
authors: Jean
authors: J
authors: Langhorne
authors: Peter R
authors: PR
authors: Preiser
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics*; D016000:Cluster Analysis; D016054:DNA, Protozoan / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D007630:Kenya; D016778:Malaria, Falciparum / Q000469:parasitology*; D005810:Multigene Family; D010802:Phylogeny; D010963:Plasmodium falciparum / Q000235:genetics* / Q000302:isolation & purification; D011110:Polymorphism, Genetic; D016053:RNA, Protozoan / Q000235:genetics; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D017385:Sequence Homology
chemical_list: D000953:Antigens, Protozoan; D016054:DNA, Protozoan; D016053:RNA, Protozoan; C474556:STEVOR antigen, Plasmodium falciparum