Sequence variation of ookinete surface proteins Pvs25 and Pvs28 of Plasmodium vivax isolates from Southern Mexico and their association to local anophelines infectivity

The polymorphism of Pvs25 and Pvs28 ookinete surface proteins, their association to circumsporozoite protein repeat (CSPr) genotypes (Vk210 and Vk247) and their infectivity to local Anopheles albimanus and Anopheles pseudopunctipennis were investigated in Plasmodium vivax-infected blood samples obtained from patients in Southern Mexico. The pvs25 and pvs28 complete genes were amplified, cloned and sequenced; and the CSPr genotype was determined by PCR amplification and hybridization. The amino acid Pvs25 and Pvs28 polymorphisms were mapped to their corresponding protein structure. Infected blood samples were simultaneously provided through artificial feeders to both mosquito species; the ratio of infected mosquitoes and oocyst numbers were recorded. The polymorphism of pvs25 and pvs28 was limited to few nucleotide positions, and produced three haplotypes: type A/A parasites presented Pvs25 and Pvs28 amino acid sequences identical to that of Sal I reference strain; parasites type B1 presented a mutation 130 Ile → Thr in Pvs25, while type B2 presented 87 Gln → Lys/130 Ile → Thr in the same molecule. Both types B1 and B2 parasites presented changes in Pvs28 at 87 Asn → Asp, 110 Tyr → Asn and five GSGGE/D repeat sequences between the fourth EGF-like domain and the GPI. Most P. vivax parasites from the coastal plains and the overlapping region were Pvs25/28 A/A, CSPrVk210 and were infective only to An. albimanus ( p ≤ 0.0001). Parasites originating in foothills were Pvs25/28 type B1/B or B2/B and CSPrVk210 or Vk247, and were more infective to An. pseudopunctipennis than to An. albimanus ( p ≤ 0.001). These results and the analysis of Pvs25/28 from other parts of the world indicated that non-synonymous variations in these proteins occur in amino acid residues exposed on the surface of the proteins, and are likely to interact with midgut mosquito ligands. We hypothesize that these molecules have been shaped by co-evolutionary adaptations of parasites to their susceptible vectors.