Abstract
BackgroundTransmission-blocking vaccines (TBVs) have been considered an important strategy for disrupting the malaria transmission cycle, especially for Plasmodium vivax malaria, which undergoes gametocytogenesis earlier during infection. Pvs25 and Pvs28 are transmission-blocking vaccine candidates for P. vivax malaria. Assessment of genetic diversity of the vaccine candidates will provide necessary information for predicting the performance of vaccines, which will guide us during the development of malaria vaccines.ResultsWe sequenced the coding regions of pvs25 and pvs28 from 30 P. vivax isolates from Yunnan Province, identifying five amino acid haplotypes of Pvs25 and seven amino acid haplotypes of Pvs28. Among a total of four mutant residues, the predominant haplotype of Pvs25 only had the I130T substitution. For Pvs28, a total of eight amino acid substitutions were identified. The predominant haplotype of Pvs28 had two substitution at positions 52 (M52L) and 140 (T140S) with 5-6 GSGGE/D tandem repeats at the end of fourth EGF-like domain. Most amino acid substitutions were common with previous reports from South Asian isolates. Although the nucleotide diversity of pvs28 (π = 0.0034 ± 0.0012) was significantly higher than pvs25 (π = 0.0013 ± 0.0009), it was still conserved when compared with the blood stage vaccine candidates.ConclusionsGenetic analysis revealed limited genetic diversity of pvs25 and pvs28, suggesting antigenic diversity may not be a particular problem for Sal I based TBVs in most P. vivax-endemic areas of China.
Highlights
Transmission-blocking vaccines (TBVs) have been considered an important strategy for disrupting the malaria transmission cycle, especially for Plasmodium vivax malaria, which undergoes gametocytogenesis earlier during infection
Sequence polymorphisms of the pvs25 and pvs28 genes Pvs25 and pvs28 genes were successfully amplified in 30 P. vivax samples obtained from Yunnan
The 30 pvs25 sequences contained four polymorphic nucleotide sites (C103A, G289C, T389C, and C391A), which resulted in four amino acid substitutions (L35M, E97Q, I130T, and Q131K)
Summary
Transmission-blocking vaccines (TBVs) have been considered an important strategy for disrupting the malaria transmission cycle, especially for Plasmodium vivax malaria, which undergoes gametocytogenesis earlier during infection. Pvs and Pvs are transmission-blocking vaccine candidates for P. vivax malaria. Plasmodium vivax, the most widespread species of human malaria parasites, is responsible for the majority of malaria cases outside of Africa, and the most prevalent form of relapsing malaria. As The Ministry of Health of China has set the goal of malaria elimination by 2020 [4], interruption of vivax malaria transmission is a major challenge. Yunnan is one of the two provinces that have year-round local transmission of P. vivax and P. falciparum. It is located in southwest China and borders Myanmar to the west and Laos and Vietnam to the south [5]. It is important to develop effective strategies to control and eliminate malaria in this region
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