Diversity and population structure of Plasmodium falciparum in Thailand based on the spatial and temporal haplotype patterns of the C-terminal 19-kDa domain of merozoite surface protein-1

Abstract

BackgroundThe 19-kDa C-terminal region of the merozoite surface protein-1 of the human malaria parasite Plasmodium falciparum (PfMSP-119) constitutes the major component on the surface of merozoites and is considered as one of the leading candidates for asexual blood stage vaccines. Because the protein exhibits a level of sequence variation that may compromise the effectiveness of a vaccine, the global sequence diversity of PfMSP-119 has been subjected to extensive research, especially in malaria endemic areas. In Thailand, PfMSP-119 sequences have been derived from a single parasite population in Tak province, located along the Thailand-Myanmar border, since 1995. However, the extent of sequence variation and the spatiotemporal patterns of the MSP-119 haplotypes along the Thai borders with Laos and Cambodia are unknown.MethodsSixty-three isolates of P. falciparum from five geographically isolated populations along the Thai borders with Myanmar, Laos and Cambodia in three transmission seasons between 2002 and 2008 were collected and culture-adapted. The msp-1 gene block 17 was sequenced and analysed for the allelic diversity, frequency and distribution patterns of PfMSP-119 haplotypes in individual populations. The PfMSP-119 haplotype patterns were then compared between parasite populations to infer the population structure and genetic differentiation of the malaria parasite.ResultsFive conserved polymorphic positions, which accounted for five distinct haplotypes, of PfMSP-119 were identified. Differences in the prevalence of PfMSP-119 haplotypes were detected in different geographical regions, with the highest levels of genetic diversity being found in the Kanchanaburi and Ranong provinces along the Thailand-Myanmar border and Trat province located at the Thailand-Cambodia border. Despite this variability, the distribution patterns of individual PfMSP-119 haplotypes seemed to be very similar across the country and over the three malarial transmission seasons, suggesting that gene flow may operate between parasite populations circulating in Thailand and the three neighboring countries.ConclusionThe major MSP-119 haplotypes of P. falciparum populations in all endemic populations during three transmission seasons in Thailand were identified, providing basic information on the common haplotypes of MSP-119 that is of use for malaria vaccine development and inferring the population structure of P. falciparum populations in Thailand.

Allelic Diversity and Geographical Distribution of the Gene Encoding <i>Plasmodium falciparum</i> Merozoite Surface Protein-3 in Thailand

“…1 ). A detailed description of the study locations has been previously described [ 28 ]. The procedures of parasite collections and maintenance were performed as previously described [ 28 ].…”

“…A detailed description of the study locations has been previously described [ 28 ]. The procedures of parasite collections and maintenance were performed as previously described [ 28 ]. The parasite species were confirmed by microscopic examinations of Giemsa-stained thin blood smears and verified by PCR using primers specific to the P. falciparum cytochrome B gene (data not shown).…”

“…The parasites were grown to a parasitemia level of 5-10% and harvested for genomic DNA preparation. The origins of P. falciparum reference clones 3D7 and K1CB1 (K1) were described previously [ 28 ].…”

“…Additionally, the analyses of msp -3 allele frequencies in P. falciparum samples collected from 6 countries in Central and West Africa between 2007 and 2009 showed a high degree of genetic homogeneity between the countries [ 27 ]. Genotyping of msp -3 from 48 and 50 P. falciparum samples from Nigeria and Thailand revealed that the polymorphism of msp -3 was likely to be maintained under frequency-dependent selection [ 28 ]. However, in the latter study, the msp -3 sequence data from Thailand was derived from only a single population at Tak Province on the Thailand-Myanmar border and, to date, there have been no further reports that elucidate the extent of genetic diversity in other regions of the country or other countries in Southeast Asia.…”

Application of a new PCR-RFLP panel suggests a restricted population structure for Eimeria tenella in UK and Irish chickens

“…Studies into naturally occurring diversity have yielded notable insights for parasites such as Plasmodium falciparum , revealing varied levels of polymorphism with evidence of clonal, as well as panmictic structures, depending on geographic location and rates of transmission (Annan et al, 2007, Larranaga et al, 2013). Locus-specific analyses have also detected considerable diversity for P. falciparum vaccine candidates such as apical membrane antigen-1 and merozoite surface protein-1 (AMA1 and MSP1, (Healer et al, 2004, Simpalipan et al, 2014)). In contrast, Toxoplasma gondii has been defined as having a clonal population structure across much of the world apart from South America, where genetic diversity and inter-clonal interbreeding is common (Minot et al, 2012).…”