Genetic diversity of the merozoite surface protein-3 gene in Plasmodium falciparum populations in ThailandReport as inadecuate

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Malaria Journal

, 15:517

First Online: 21 October 2016Received: 15 July 2016Accepted: 07 October 2016DOI: 10.1186-s12936-016-1566-1

Cite this article as: Pattaradilokrat, S., Sawaswong, V., Simpalipan, P. et al. Malar J 2016 15: 517. doi:10.1186-s12936-016-1566-1


BackgroundAn effective malaria vaccine is an urgently needed tool to fight against human malaria, the most deadly parasitic disease of humans. One promising candidate is the merozoite surface protein-3 MSP-3 of Plasmodium falciparum. This antigenic protein, encoded by the merozoite surface protein msp-3 gene, is polymorphic and classified according to size into the two allelic types of K1 and 3D7. A recent study revealed that both the K1 and 3D7 alleles co-circulated within P. falciparum populations in Thailand, but the extent of the sequence diversity and variation within each allelic type remains largely unknown.

MethodsThe msp-3 gene was sequenced from 59 P. falciparum samples collected from five endemic areas Mae Hong Son, Kanchanaburi, Ranong, Trat and Ubon Ratchathani in Thailand and analysed for nucleotide sequence diversity, haplotype diversity and deduced amino acid sequence diversity. The gene was also subject to population genetic analysis Fst and neutrality tests Tajima’s D, Fu and Li D* and Fu and Li’ F* tests to determine any signature of selection.

ResultsThe sequence analyses revealed eight unique DNA haplotypes and seven amino acid sequence variants, with a haplotype and nucleotide diversity of 0.828 and 0.049, respectively. Neutrality tests indicated that the polymorphism detected in the alanine heptad repeat region of MSP-3 was maintained by positive diversifying selection, suggesting its role as a potential target of protective immune responses and supporting its role as a vaccine candidate. Comparison of MSP-3 variants among parasite populations in Thailand, India and Nigeria also inferred a close genetic relationship between P. falciparum populations in Asia.

ConclusionThis study revealed the extent of the msp-3 gene diversity in P. falciparum in Thailand, providing the fundamental basis for the better design of future blood stage malaria vaccines against P. falciparum.

KeywordsDNA sequencing Genetic diversity Vaccine Merozoite surface protein Southeast Asia Electronic supplementary materialThe online version of this article doi:10.1186-s12936-016-1566-1 contains supplementary material, which is available to authorized users.

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Author: Sittiporn Pattaradilokrat - Vorthon Sawaswong - Phumin Simpalipan - Morakot Kaewthamasorn - Napaporn Siripoon - Pongchai Har


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