Natália Ketrin Almeida-de-Oliveira1,2, Lidiane Lima-Cury1,2, Rebecca de Abreu-Fernandes1,2, Aline de Rosa Lavigne1,2, Anielle de Pina-Costa3,2,4, Daiana de Souza Perce-da-Silva1,2, Marcos Catanho5, Patrícia Brasil3,2, Cláudio Tadeu Daniel-Ribeiro1,2, Maria de Fátima Ferreira-da-Cruz6,7. 1. Laboratório de Pesquisas em Malária, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (Fiocruz), Avenida Brasil 4365, Manguinhos, Rio de Janeiro, Brazil. 2. Centro de Pesquisa, Diagnóstico e Treinamento em Malária Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, Brazil. 3. Laboratório de Pesquisa Clínica em Doenças Febris Agudas, Instituto Nacional de Infectologia Evandro Chagas, Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Brazil. 4. Centro Universitário Serra dos Órgãos (UNIFESO), Teresópolis, Rio de Janeiro, Brazil. 5. Laboratório de Genética Molecular de Microrganismos, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Brazil. 6. Laboratório de Pesquisas em Malária, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (Fiocruz), Avenida Brasil 4365, Manguinhos, Rio de Janeiro, Brazil. mffcruz28@gmail.com. 7. Centro de Pesquisa, Diagnóstico e Treinamento em Malária Reference Laboratory for Malaria in the Extra-Amazonian Region for the Brazilian Ministry of Health, SVS & Fiocruz, Rio de Janeiro, Brazil. mffcruz28@gmail.com.
Abstract
BACKGROUND: Plasmodium vivax is the most widespread human malaria parasite outside Africa and is the predominant parasite in the Americas. Increasing reports of P. vivax disease severity, together with the emergence of drug-resistant strains, underscore the urgency of the development of vaccines against P. vivax. Polymorphisms on DBP-II-gene could act as an immune evasion mechanism and, consequently, limited the vaccine efficacy. This study aimed to investigate the pvdbp-II genetic diversity in two Brazilian regions with different epidemiological patterns: the unstable transmission area in the Atlantic Forest (AF) of Rio de Janeiro and; the fixed malaria-endemic area in Brazilian Amazon (BA). METHODS: 216 Brazilian P. vivax infected blood samples, diagnosed by microscopic examination and PCR, were investigated. The region flanking pvdbp-II was amplified by PCR and sequenced. Genetic polymorphisms of pvdbp-II were estimated based on the number of segregating sites and nucleotide and haplotype diversities; the degree of differentiation between-regions was evaluated applying Wright's statistics. Natural selection was calculated using the rate of nonsynonymous per synonymous substitutions with the Z-test, and the evolutionary distance was estimated based on the reconstructed tree. RESULTS: 79 samples from AF and 137 from BA were successfully sequenced. The analyses showed 28 polymorphic sites distributed in 21 codons, with only 5% of the samples Salvador 1 type. The highest rates of polymorphic sites were found in B- and T cell epitopes. Unexpectedly, the nucleotide diversity in pvdbp-II was higher in AF (0.01) than in BA (0.008). Among the 28 SNPs detected, 18 are shared between P. vivax isolates from AF and BA regions, but 8 SNPs were exclusively detected in AF-I322S, K371N, E385Q, E385T, K386T, K411N, I419L and I419R-and 2 (N375D and I419M) arose exclusively in BA. These findings could suggest the potential of these geographical clusters as population-specific-signatures that may be useful to track the origin of infections. The sample size should be increased in order to confirm this possibility. CONCLUSIONS: The results highlight that the pvdbp-II polymorphisms are positively selected by host's immune pressure. The characterization of pvdbp-II polymorphisms might be useful for designing effective DBP-II-based vaccines.
BACKGROUND:Plasmodium vivax is the most widespread humanmalaria parasite outside Africa and is the predominant parasite in the Americas. Increasing reports of P. vivax disease severity, together with the emergence of drug-resistant strains, underscore the urgency of the development of vaccines against P. vivax. Polymorphisms on DBP-II-gene could act as an immune evasion mechanism and, consequently, limited the vaccine efficacy. This study aimed to investigate the pvdbp-II genetic diversity in two Brazilian regions with different epidemiological patterns: the unstable transmission area in the Atlantic Forest (AF) of Rio de Janeiro and; the fixed malaria-endemic area in Brazilian Amazon (BA). METHODS: 216 Brazilian P. vivaxinfected blood samples, diagnosed by microscopic examination and PCR, were investigated. The region flanking pvdbp-II was amplified by PCR and sequenced. Genetic polymorphisms of pvdbp-II were estimated based on the number of segregating sites and nucleotide and haplotype diversities; the degree of differentiation between-regions was evaluated applying Wright's statistics. Natural selection was calculated using the rate of nonsynonymous per synonymous substitutions with the Z-test, and the evolutionary distance was estimated based on the reconstructed tree. RESULTS: 79 samples from AF and 137 from BA were successfully sequenced. The analyses showed 28 polymorphic sites distributed in 21 codons, with only 5% of the samples Salvador 1 type. The highest rates of polymorphic sites were found in B- and T cell epitopes. Unexpectedly, the nucleotide diversity in pvdbp-II was higher in AF (0.01) than in BA (0.008). Among the 28 SNPs detected, 18 are shared between P. vivax isolates from AF and BA regions, but 8 SNPs were exclusively detected in AF-I322S, K371N, E385Q, E385T, K386T, K411N, I419L and I419R-and 2 (N375D and I419M) arose exclusively in BA. These findings could suggest the potential of these geographical clusters as population-specific-signatures that may be useful to track the origin of infections. The sample size should be increased in order to confirm this possibility. CONCLUSIONS: The results highlight that the pvdbp-II polymorphisms are positively selected by host's immune pressure. The characterization of pvdbp-II polymorphisms might be useful for designing effective DBP-II-based vaccines.
Entities:
Keywords:
DBP; Genetic diversity; Malaria; Plasmodium vivax; Positive selection; SNP