Immune Response Pattern in Primary and Recurrent Plasmodium vivax Malaria in a Gold-Mining Area from Amazon Region

Background: P. vivax is the causative agent of human malaria of large geographic distribution, with 35 million cases annually. P. vivax malaria is highly prevalent in Latin America, Asian and some Pacific region. In Brazil, the Amazon region concentrates almost all cases infections registered countrywide, with more than three hundred thousand cases per year. Several evidences suggest that an exacerbated inflammatory response associated to parasitism is likely to aggravate the malaria symptoms. Materials and Methods: A cross-sectional study was performed in Itaituba, municipality situated on southwest of Para state, including 50 malaria patients and 79 healthy individuals. The plasmatic cytokine profile was assessed, aiming at establishing patterns of immune response characteristic of primary malaria (n=15), recurrent malaria (n=35) and endemic control (n=79). The plasmatic cytokines IL-2, IL-4 IL-6, IL-10, TNF-α and IFN-γ were quantified by BD Human Th1/Th2 cytokine Kit II and all purchased from BD Biosciences Pharmingen. Statistical analyses were carried out using the Graph-Pad Prism software, version 6.0 and comparative analyses amongst groups (endemic controls vs primary malaria vs recurrent malaria) were performed by Kruskal–Wallis followed by multiple comparisons performed by Dunn’s post-test. Results: Data analysis indicated significant increase in the IL-6 and IL-10 plasmatic levels in both malaria groups as compared with endemic control group; the primary malaria patients displayed the highest significant plasmatic IFN-γ levels as compared with recurrent malaria patients and with endemic control; the recurrent malaria patients displayed the highest significant plasmatic TNF-α as compared with endemic control; no significant differences was detected in the IL-2 and IL-4 plasmatic levels in the groups. Conclusions: Although this study has been conducted with a relatively small number of patients, our findings have shown that primary malaria induces a relevant INF-γ and IL-10-mediated response, suggesting that the gradual remodeling of the immune response is not dependent on the repeated exposure to the parasite in this population. The present study is a descriptive investigation and does not report the mechanisms underlying the development of distinct patterns.