Naturally acquired immune responses to malaria vaccine candidate antigens MSP3 and GLURP in Guahibo and Piaroa indigenous communities of the Venezuelan Amazon

A cross-sectional study was carried out in two indigenous population groups in Amazonas/Venezuela. Data from the regional malaria documentation system were extracted and participants from the ethnic groups of the Guahibo (n = 180) and Piaroa (n = 295) were investigated for the presence of Plasmodium parasites and naturally acquired antibodies to Plasmodium falciparum antigens in serum. The GMZ2 vaccine candidate proteins MSP3 and GLURP were chosen as serological markers.The incidence of P. falciparum in both communities was found to be less than 2%, and none of the participants harboured P. falciparum at the time of the cross-sectional. Nearly a quarter of the participants (111/475; 23,4%) had positive antibody titres to at least one of the antigens. 53/475 participants (11.2%) were positive for MSP3, and 93/475 participants (19.6%) were positive for GLURP. High positive responses were detected in 36/475 participants (7.6%) and 61/475 participants (12.8%) for MSP3 and GLURP, respectively. Guahibo participants had significantly higher antibody titres than Piaroa participants.Considering the low incidence of P. falciparum, submicroscopical infections may explain the comparatively high anti-P. falciparum antibody concentrations.To date, malaria is among the top ten causes of death in low-income countries [1]. In Venezuela, particularly the southern states of Bolivar and Amazonas are affected by malaria transmission. However, mortality is insignificant and malaria can be considered as controlled [2]. Amazonas (180,145 km2) covers an area nearly twice as big as Portugal and is inhabited by approximately 150,000 persons. Roughly half of the population is of indigenous origin and - although the absolute number of cases is low - Amazonas has the highest malaria incidence per capita in Venezuela (2007: 68.4 cases/1,000 inhabitants). Overall, the main malaria species is Plasmodium vivax (ca. 80%) followed by Plasmodium falciparum (ca 20%, with declining tendency). Plasmodium