Genetic diversity of transmission-blocking vaccine candidates Pvs25 and Pvs28 in Plasmodium vivax isolates from Yunnan Province, China

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>Transmission-blocking vaccines (TBVs) have been considered an important strategy for disrupting the malaria transmission cycle, especially for <jats:italic>Plasmodium vivax</jats:italic> malaria, which undergoes gametocytogenesis earlier during infection. Pvs25 and Pvs28 are transmission-blocking vaccine candidates for <jats:italic>P. vivax</jats:italic> 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.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>We sequenced the coding regions of <jats:italic>pvs25</jats:italic> and <jats:italic>pvs28</jats:italic> from 30 <jats:italic>P. vivax</jats:italic> 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 <jats:italic>pvs28</jats:italic> (π = 0.0034 ± 0.0012) was significantly higher than <jats:italic>pvs25</jats:italic> (π = 0.0013 ± 0.0009), it was still conserved when compared with the blood stage vaccine candidates.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Genetic analysis revealed limited genetic diversity of <jats:italic>pvs25</jats:italic> and <jats:italic>pvs28</jats:italic>, suggesting antigenic diversity may not be a particular problem for Sal I based TBVs in most <jats:italic>P. vivax</jats:italic>-endemic areas of China.</jats:p> </jats:sec>