Duffy Negative Antigen Is No Longer a Barrier to Plasmodium vivax – Molecular Evidences from the African West Coast (Angola and Equatorial Guinea)

Recent reports of Plasmodium vivax infections, the most widely distributed species of human malaria, show that this parasite is evolving and adapting, becoming not only more aggressive but also more frequent in countries where it was not present in the past, becoming, therefore, a major source of concern. Thus, it is extremely important to perform new studies of its distribution in West and Central Africa, where there are few reports of its presence, due to the high prevalence of Duffy-negative individuals. The aim of this study was to investigate the presence of P. vivax in Angola and in Equatorial Guinea, using blood samples and mosquitoes. The results showed that P. vivax seems to be able to invade erythrocytes using receptors other than Duffy, and this new capacity is not exclusive to one strain of P. vivax, since we have found samples infected with two different strains: VK247 and classic. Additionally we demonstrated that the parasite has a greater distribution than previously thought, calling for a reevaluation of its worldwide distribution

Plasmodium vivax Cell Traversal Protein for Ookinetes and Sporozoites (PvCelTOS) gene sequence and potential epitopes are highly conserved among isolates from different regions of Brazilian Amazon

The Plasmodium vivax Cell-traversal protein for ookinetes and sporozoites (PvCelTOS) plays an important role in the traversal of host cells. Although essential to PvCelTOS progress as a vaccine candidate, its genetic diversity remains uncharted. Therefore, we investigated the PvCelTOS genetic polymorphism in 119 field isolates from five different regions of Brazilian Amazon (Manaus, Novo Repartimento, Porto Velho, Plácido de Castro and Oiapoque). Moreover, we also evaluated the potential impact of non-synonymous mutations found in the predicted structure and epitopes of PvCelTOS. The field isolates showed high similarity (99.3% of bp) with the reference Sal-1 strain, presenting only four Single-Nucleotide Polymorphisms (SNP) at positions 24A, 28A, 109A and 352C. The frequency of synonymous C109A (82%) was higher than all others (p<0.0001). However, the non-synonymous G28A and G352C were observed in 9.2% and 11.7% isolates. The great majority of the isolates (79.8%) revealed complete amino acid sequence homology with Sal-1, 10.9% presented complete homology with Brazil I and two undescribed PvCelTOS sequences were observed in 9.2% field isolates. Concerning the prediction analysis, the N-terminal substitution (Gly10Ser) was predicted to be within a B-cell epitope (PvCelTOS Accession Nos. AB194053.1) and exposed at the protein surface, while the Val118Leu substitution was not a predicted epitope. Therefore, our data suggest that although G28A SNP might interfere in potential B-cell epitopes at PvCelTOS N-terminal region the gene sequence is highly conserved among the isolates from different geographic regions, which is an important feature to be taken into account when evaluating its potential as a vaccine candidate

Genotyping Plasmodium vivax isolates from the 2011 outbreak in Greece

Background: Plasmodium vivax malaria was common in Greece until the 1950s with epidemics involving thousands of cases every year. Greece was declared free of malaria by the World Health Organization in 1974. From 1974 to 2010, an average of 39 cases per year were reported, which were mainly imported. However, in 2009 and 2010 six and one autochthonous cases were reported culminating with a total of 40 autochthonous cases reported in 2011, of which 34 originated from a single region: Laconia of Southern Peloponnese. In this study the genotypic complexity of the P. vivax infections from the outbreak in Greece during 2011 is described, to elucidate the possible origin and spread of the disease. Methods: Three polymorphic markers of P. vivax were used; Pvmsp-3a and the microsatellites m1501 and m3502 on P. vivax isolates sampled from individuals diagnosed in Greece. Thirty-nine isolates were available for this study (20 autochthonous and 19 imported), mostly from Evrotas municipality in Laconia region, in southern Greece, (n = 29), with the remaining representing sporadic cases originating from other areas of Greece. Results: Genotyping the Evrotas samples revealed seven different haplotypes where the majority of the P. vivax infections expressed two particular Pvmsp-3a-m1501-m3502 haplotypes, A10-128-151 (n = 14) and A10-121-142 (n = 7). These haplotypes appeared throughout the period in autochthonous and imported cases, indicating continuous transmission. In contrast, the P. vivax autochthonous cases from other parts of Greece were largely comprised of unique haplotypes, indicating limited transmission in these other areas. Conclusions: The results indicate that several P. vivax strains were imported into various areas of Greece in 2011, thereby increasing the risk of re-introduction of malaria. In the region of Evrotas ongoing transmission occurred exemplifying that further control measures are urgently needed in this region of southern Europe. In circumstances where medical or travel history is scarce, methods of molecular epidemiology may prove highly useful for the correct classification of the cases