Abstract
BackgroundPlasmodium vivax is the most prevalent malaria parasite in many countries. A better understanding of human immunity to this parasite can provide new insights for vaccine development. Plasmodium vivax Reticulocyte Binding Proteins (RBPs) are key parasite proteins that interact with human proteins during erythrocyte invasion and are targets of the human immune response. The aim of this study is to characterize the human antibody response to RBP2P1, the most recently described member of the RBP family.MethodsThe levels of total IgG and IgM against RBP2P1 were measured using plasmas from 68 P. vivax malaria patients and 525 villagers in a malarious village of western Thailand. The latter group comprises asymptomatic carriers and healthy uninfected individuals. Subsets of plasma samples were evaluated for anti-RBP2P1 IgG subtypes and complement-fixing activity.ResultsAs age increased, it was found that the level of anti-RBP2P1 IgG increased while the level of IgM decreased. The main anti-RBP2P1 IgG subtypes were IgG1 and IgG3. The IgG3-seropositive rate was higher in asymptomatic carriers than in patients. The higher level of IgG3 was correlated with higher in vitro RBP2P1-mediated complement fixing activity.ConclusionsIn natural infection, the primary IgG response to RBP2P1 was IgG1 and IgG3. The predominance of these cytophilic subtypes and the elevated level of IgG3 correlating with complement fixing activity, suggest a possible role of anti-RBP2P1 antibodies in immunity against P. vivax.
Highlights
Plasmodium vivax is the most prevalent malaria parasite in many countries
IgM and total IgG in the community survey 525 plasma samples from a cross-sectional survey in Kanchanaburi province were used to examine the presence of RBP2P1 antibodies in the community
When the cross-sectional samples were classified into four age groups: 0–6 years, 7–12 years, 13–17 years and ≥ 18 years, the anti-RBP2P1 IgM levels were higher (Kruskal-Wallis test with Dunn’s multiple-comparison test, p = 0.0168) in children aged 7–12 years compared to adults (Fig. 1A)
Summary
Plasmodium vivax is the most prevalent malaria parasite in many countries. A better understand‐ ing of human immunity to this parasite can provide new insights for vaccine development. Plasmodium vivax Reticulocyte Binding Proteins (RBPs) are key parasite proteins that interact with human proteins during erythro‐ cyte invasion and are targets of the human immune response. The aim of this study is to characterize the human antibody response to RBP2P1, the most recently described member of the RBP family. We characterized a novel RBP, RBP2P1, and found that a higher level of total IgG to RBP2P1 is associated with lower parasitaemia, suggesting an involvement in functional immunity [13].
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