Abstract
BackgroundPlasmodium vivax is a protozoan parasite with an extensive worldwide distribution, being highly prevalent in Asia as well as in Mesoamerica and South America. In southern Mexico, P. vivax transmission has been endemic and recent studies suggest that these parasites have unique biological and genetic features. The msp1 gene has shown high rate of nucleotide substitutions, deletions, insertions, and its mosaic structure reveals frequent events of recombination, maybe between highly divergent parasite isolates.MethodsThe nucleotide sequence variation in the polymorphic icb5-6 fragment of the msp1 gene of Mexican and worldwide isolates was analysed. To understand how genotype diversity arises, disperses and persists in Mexico, the genetic structure and genealogical relationships of local isolates were examined. To identify new sequence hybrids and their evolutionary relationships with other P. vivax isolates circulating worldwide two haplotype networks were constructed questioning that two portions of the icb5-6 have different evolutionary history.ResultsTwelve new msp1 icb5-6 haplotypes of P. vivax from Mexico were identified. These nucleotide sequences show mosaic structure comprising three partially conserved and two variable subfragments and resulted into five different sequence types. The variable subfragment sV1 has undergone recombination events and resulted in hybrid sequences and the haplotype network allocated the Mexican haplotypes to three lineages, corresponding to the Sal I and Belem types, and other more divergent group. In contrast, the network from icb5-6 fragment but not sV1 revealed that the Mexican haplotypes belong to two separate lineages, none of which are closely related to Sal I or Belem sequences.ConclusionsThese results suggest that the new hybrid haplotypes from southern Mexico were the result of at least three different recombination events. These rearrangements likely resulted from the recombination between haplotypes of highly divergent lineages that are frequently distributed in South America and Asia and diversified rapidly.
Highlights
Plasmodium vivax is a protozoan parasite with an extensive worldwide distribution, being highly prevalent in Asia as well as in Mesoamerica and South America
Msp1 icb5-6 SSCP genotype frequency and circumsporozoite repeat type The PCR-SSCP analysis of the msp1 icb5-6 fragments obtained from single-P. vivax genotype infections allowed three patterns to be distinguished, designated as A, B and C
Sequence types of the msp1 icb5-6 gene fragment A total of fourteen sequences ranging from 645 to 729 bp were obtained from single P. vivax genotype infections, they comprised codons 678–920 and 683–903 of the Sal I and Belem sequences
Summary
Plasmodium vivax is a protozoan parasite with an extensive worldwide distribution, being highly prevalent in Asia as well as in Mesoamerica and South America. The inter-species conserved fragment (icb) 5 and 6 shows high polymorphism due to intra-allelic recombination, insertions, deletions and further point mutations, generating a wide range of new genotypes [15,16,17,18,19,20,21,22]. This high gene polymorphism has allowed the identification of different genetic forms of the parasite, most of which are unique [23,24] and suitable for molecular discrimination of relapse episodes [13,25], and useful for phylogenetic studies [26]
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