A systematic review on malaria sero-epidemiology studies in the Brazilian Amazon: insights into immunological markers for exposure and protection

Abstract

BackgroundConsiderable success in reducing malaria incidence and mortality has been achieved in Brazil, leading to discussions over the possibility of moving towards elimination. However, more than reporting and counting clinical cases, elimination will require the use of efficient tools and strategies for measuring transmission dynamics and detecting the infectious reservoir as the primary indicators of interest for surveillance and evaluation. Because acquisition and maintenance of anti-malarial antibodies depend on parasite exposure, seroprevalence rates could be used as a reliable tool for assessing malaria endemicity and an adjunct measure for monitoring transmission in a rapid and cost-effective manner.MethodsThis systematic review synthesizes the existing literature on seroprevalence of malaria in the Brazilian Amazon Basin. Different study designs (cross-sectional surveys and longitudinal studies) with reported serological results in well-defined Brazilian populations were considered. Medline (via PubMed), EMBASE and LILACS databases were screened and the articles were included per established selection criteria. Data extraction was performed by two authors and a modified critical appraisal tool was applied to assess the quality and completeness of cross-sectional studies regarding defined variables of interest.ResultsFrom 220 single records identified, 23 studies were included in this systematic review for the qualitative synthesis. Five studies reported serology results on Plasmodium falciparum, 14 papers assessed Plasmodium vivax and four articles reported results on both Plasmodium species. Considerable heterogeneity among the evaluated malarial antigens, including sporozoite and blood stage antigens, was observed. The majority of recent studies analysed IgG responses against P. vivax antigens reflecting the species distribution pattern in Brazil over the last decades. Most of the published papers were cross-sectional surveys (73.9%) and only six cohort studies were included in this review. Three studies pointed to an association between antibodies against circumsporozoite protein of both P. falciparum and P. vivax and malaria exposure. Furthermore, five out 13 cross-sectional studies evidenced a positive association between IgG antibodies to the conserved 19-kDa C-terminal region of the merozoite surface protein 1 of P. vivax (PvMSP119) and malaria exposure.ConclusionsThis systematic review identifies potential biomarkers of P. falciparum and P. vivax exposure in areas with variable and unstable malaria transmission in Brazil. However, this study highlights the need for standardization of further studies to provide an ideal monitoring tool to evaluate trends in malaria transmission and the effectiveness of malaria intervention programmes in Brazil. Moreover, the score-based weighted tool developed and used in this study still requires further validation.

Mosquito Bite-Induced Controlled Human Malaria Infection with Plasmodium vivax or P. falciparum Generates Immune Responses to Homologous and Heterologous Preerythrocytic and Erythrocytic Antigens

“…Antibodies to sporozoites and the central repeat region of CSP have been used as markers of exposure to Plasmodium spp. The repeat sequences of plasmodia are species specific; therefore, anti-CSP antibodies have been used to demonstrate correlation with infection prevalence, transmission intensity, and exposure (1,37). Blood-stage antigens, such as MSP-1 and AMA-1, are also used for seroepidemiological studies (38).…”

“…Due to the ease of their detection, the presence of antigen-specific antibodies is used as a biomarker for exposure to specific pathogens. Seroepidemiological analysis is widely used as an indicator of clinical immunity (1-4) as well as endemicity and transmission intensity (1,5,6) of malaria caused by both Plasmodium falciparum and P. vivax. Naturally acquired immunity (NAI) studies are usually performed with the goal of understanding clinical (i.e., antidisease) immunity.…”

IgG subclass responses to excreted-secreted antigens of Plasmodium falciparum in a low-transmission malaria area of the Peruvian Amazon

“…However, this process is not at all complete in symptomatic carriers, as the results reflect higher antibody levels and seroprevalence of IgG4 in symptomatic carriers. The binding of IgG4 to an antigen blocks the recognition of the antigen by cytophilic IgG and, therefore, the activation of effector cells through Fc receptors [ 4 , 22 , 51 , 54 – 56 ]. This imbalance in the major mechanism controlling malaria symptoms is reflected in the fever, chills, nausea, and body aches observed in Zungarococha settlers [ 33 ].…”

Malaria Burden and Trend Among Clients Seeking Healthcare in the Western Region: A 4-Year Retrospective Study at the Sefwi-Wiawso Municipal Hospital, Ghana

“…Malaria infection continues to be of significant public health importance worldwide and in the developing world in spite of sustained global efforts targeted at eliminating the disease [1,2]. According to a recent report by the World Health Organization (WHO), 212 million new cases of malaria were recorded worldwide in 2015, out of which, the Africa region accounted for about 90% of the global malaria cases [3].…”