Genetic polymorphism and natural selection of circumsporozoite protein in Myanmar Plasmodium vivax

Abstract

Background Circumsporozoite surface protein (CSP) of malaria parasites has been recognized as one of the leading vaccine candidates. Clinical trials of vaccines for vivax malaria incorporating Plasmodium vivax CSP (PvCSP) have demonstrated their effectiveness in preventing malaria, at least in part. However, genetic diversity of pvcsp in the natural population remains a major concern. Methods A total of 171 blood samples collected from patients infected with Plasmodium vivax in Myanmar were analysed in this study. The pvcsp was amplified by polymerase chain reaction, followed by cloning and sequencing. Polymorphic characteristics and natural selection of pvcsp population in Myanmar were analysed using DNASTAR, MEGA6 and DnaSP programs. The polymorphic pattern and natural selection of publicly accessible global pvcsp sequences were also comparatively analysed. Results Myanmar pvcsp sequences were divided into two subtypes VK210 and VK247 comprising 143 and 28 sequences, respectively. The VK210 subtypes showed higher levels of genetic diversity and polymorphism than the VK247 subtypes. The N-terminal non-repeat region of pvcsp displayed limited genetic variations in the global population. Different patterns of octapeptide insertion (ANKKAEDA in VK210 and ANKKAGDA in VK247) and tetrapeptide repeat motif (GGNA) were identified in the C-terminal region of global pvcsp population. Meanwhile, the central repeat region (CRR) of Myanmar and global pvcsp, both in VK210 and VK247 variants, was highly polymorphic. The high level of genetic diversity in the CRR has been attributed to the different numbers, types and combinations of peptide repeat motifs (PRMs). Interestingly, 27 and 5 novel PRMs were found in Myanmar VK210 and VK247 variants, respectively. Conclusion Comparative analysis of the global pvcsp population suggests a complex genetic profile of pvcsp in the global population. These results widen understanding of the genetic make-up of pvcsp in the global P. vivax population and provide valuable information for the development of a vaccine based on PvCSP.

A universal vaccine candidate against Plasmodium vivax malaria confers protective immunity against the three PvCSP alleles

“…Each variant displays repeating nonapeptides, of which the more prevalent are GDRA(D/A)GQPA and ANGA(G/A) (C/D)QPG, respectively 8 , 9 . Nonetheless, several different peptide repeat motifs were described in the central region of both variants, and this genetic polymorphism could have impact on the efficacy of CSP-based vaccines 10 . A third variant from a parasite that causes P. vivax malaria in humans, called Plasmodium vivax- like, expresses CSP with APGANQ(E/G)GAA repeats (hereafter named Pv CSP- P. vivax -like) and was described in endemic regions of Papua New Guinea, Brazil, Indonesia and Madagascar 11 .…”

Genetic Diversity of Circumsporozoite Surface Protein of Plasmodium vivax from the Central Highlands, Vietnam

“…P. vivax genomic DNA was extracted from the dried blood spots using the QIAamp DNA Blood Kit (Qiagen, Hilden, Germany) according to the manufacturer’s protocols. The amplification of pvcsp in Vietnamese P. vivax isolates was performed by a nested polymerase chain reaction (PCR) with the same primer sets and amplification conditions as described previously [ 17 ]. To minimize nucleotide mismatching during the amplification steps, Ex Taq DNA polymerase (Takara, Otsu, Japan) with proofreading activity was used.…”

“…The genetic diversity and natural selection of pvcsp among the global P. vivax population were analyzed. The pvcsp sequences from P. vivax isolates ( n = 632) from Myanmar ( n = 171) [ 17 ], Cambodia ( n = 41) [ 26 ], India ( n = 79), Iran ( n = 50), South Korea ( n = 39), Brazil ( n = 41) [ 27 ], Mexico ( n = 19) [ 16 ], Colombia ( n = 25), Sudan ( n = 30) [ 28 ], Vanuatu ( n = 21) [ 29 ], and Vietnam ( n = 116) were included (Supplementary Material File S2: Table S1 ). Genetic polymorphism and the test of neutrality were analyzed for the pvcsp population with DnaSP ver 5.10.00 [ 21 ] and MEGA6 [ 22 ].…”

“…These motifs are usually repeated multiple times in the CRR. They contribute to high polymorphic characters of pvcsp along with synonymous and non-synonymous single nucleotide polymorphisms (SNPs) in the region [ 16 , 17 ].…”

“…Therefore, understanding the genetic make-up of pvcsp in the wild-type P. vivax population would be informative for the development of a universal vaccine. Non-neglectable patterns of genetic polymorphism of pvcsp have been identified in global P. vivax isolates [ 17 ]. In this study, we investigated the genetic polymorphisms and natural selection of pvcsp from P. vivax isolates collected from the Central Highlands, a malaria-endemic region in Vietnam.…”