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Global genetic diversity and evolution of var genes associated with placental and severe childhood malaria

Authors :
Trimnell, Adama R.
Kraemer, Susan M.
Mukherjee, Sandeep
Phippard, David J.
Janes, Joel H.
Flamoe, Eric
Su, Xin-zhuan
Awadalla, Philip
Smith, Joseph D.
Source :
Molecular & Biochemical Parasitology. Aug2006, Vol. 148 Issue 2, p169-180. 12p.
Publication Year :
2006

Abstract

Abstract: In Plasmodium falciparum, var genes encode adhesive proteins that are transported to the surface of infected erythrocytes and act as major virulence determinants for infected erythrocyte binding and immune evasion. Var genes are highly diverse and can be classified into five major groups (UpsA, B, C, D, and E). Previous serological studies have suggested that the UpsA var group may contain common antigenic types that have important roles in severe childhood malaria. Here, our analysis found that UpsA vars are highly diverse between 22 world-wide parasite isolates, although they could be grouped into two broad clusters that may be separately recombining. By comparison, orthologs of the UpsA-linked Type 3 var and UpsE-linked var2csa were detected in nearly all parasite isolates, and a var2csa ortholog was also present in a chimpanzee malaria P. reichenowi that diverged from P. falciparum ∼5–7 million years ago. Although the specific function of Type 3 var genes is unknown, var2csa is a leading candidate for a pregnancy associated malaria vaccine. Compared to typical var genes, var2csa is unusually conserved but still had only 54–94% amino acid identity in extracellular binding regions. However, var2csa alleles have extensive gene mosaicism within polymorphic blocks that are shared between world-wide parasite isolates and recognizable in P. rechenowi suggesting a high rate of self–self recombination and an ancient and globally-related pool of var2csa polymorphism. These studies aid our understanding of the evolutionary mechanisms that shape var diversity and will be important to the development of vaccines against pregnancy associated malaria and severe malaria. [Copyright &y& Elsevier]

Details

Language :
English
ISSN :
01666851
Volume :
148
Issue :
2
Database :
Academic Search Index
Journal :
Molecular & Biochemical Parasitology
Publication Type :
Academic Journal
Accession number :
21426382
Full Text :
https://doi.org/10.1016/j.molbiopara.2006.03.012