Genetic polymorphism of merozoite surface protein 1 and merozoite surface protein 2 in the Vietnam Plasmodium falciparum population

Abstract

Background: Plasmodium falciparum merozoite surface proteins 1 (PfMSP1) and 2 (PfMSP2) are potential candidates for malaria vaccine development. However, the genetic diversity of these genes in the global P. falciparum population presents a significant challenge in developing an effective vaccine. Hence, understanding the genetic diversity and evolutionary trends in the global P. falciparum population is crucial.

Methods: This study analyzed the genetic variations and evolutionary changes of pfmsp1 and pfmsp2 in P. falciparum isolates from the Central Highland and South-Central regions of Vietnam. DNASTAR and MEGA7 programs were utilized for analyses. The polymorphic nature of global pfmsp1 and pfmsp2 was also investigated.

Results: A total of 337 sequences of pfmsp1 and 289 sequences of pfmsp2 were obtained. The pfmsp1 and pfmsp2 from Vietnam revealed a higher degree of genetic homogeneity compared to those from other malaria-endemic countries. Remarkably, the allele diversity patterns of Vietnam pfmsp1 and pfmsp2 differed significantly from those of neighboring countries in the Greater Mekong Subregion. Declines in allele diversity and polymorphic patterns of Vietnam pfmsp1 and pfmsp2 were observed.

Conclusions: The Vietnam P. falciparum population might be genetically isolated from the parasite populations in other neighboring GMS countries, likely due to geographical barriers and distinct evolutionary pressures. Furthermore, bottleneck effects or selective sweeps may have contributed to the genetic homogeneity of Vietnam pfmsp1 and pfmsp2.

Keywords: Plasmodium falciparum; Genetic diversity; Merozoite surface proteins; Vietnam.

Fig. 1

Map of blood collection areas. The blood samples used in this study were collected from P. falciparum-infected patients residing in five provinces of Vietnam from 2018 to 2022

Fig. 2

Polymorphic patterns in Vietnam pfmsp1 block II. A total of 27 different alleles were found in Vietnam pfmsp1 block II, including 25 alleles for MAD20 type, 1 allele for K1 type, and 1 allele for RO33 type. Vietnam MAD20 block II consisted of seven different PRMs, including SGG, SVT, SVA, SKG, SSG, PVA, and TVA. Meanwhile, Vietnam K1 block II included three distinct PRMs: SAQ, SGT, and SGP. Vietnam RO33 block II had sequences identical to the reference sequence. The total number of isolates for each allele is indicated

Fig. 3

Allelic diversity of the global pfmsp1 block II. Different proportions of three pfmsp1 types including MAD20, K1, and RO33 were observed in the global pfmsp1 populations

Fig. 4

PRM profiles of the global pfmsp1 block II. Differences in PRM types in the global MAD20 and K1 populations. MAD20 block II comprised 10 different PRMs, while K1 block II included 17 distinct PRMs

Fig. 5

Size polymorphism patterns of the global pfmsp1 block II. Size differences in the global pfmsp1 block II were caused by varying numbers of PRMs. The global MAD20 block II exhibited 17 different sizes with PRM counts ranging from 1 to 19. The global K1 block II displayed 20 different size polymorphisms resulting from distinct PRMs counts that ranged from 4 to 25

Fig. 6

Polymorphic patterns in Vietnam pfmsp2 block III. In Vietnam, seven distinct alleles of the 3D7 types (A1–A7) were identified in the pfmsp2 population

Fig. 7

Allelic diversity of the global pfmsp2 block III. In global populations, different proportions of two pfmsp2 subtypes, namely 3D7 and FC27, were evident

Fig. 8

Comparison of polymorphism patterns in the R1, R2, and E3 regions of the global pfmsp2 3D7 type. (A) Distinct PRM profiles in the R1 region. (B) Varied poly-T patterns in the R2 region. (C) Diverse insertion sequences in the E3 region. N/A, not available for analysis due to the sequence missing corresponding to the region