Antibody response against Plasmodium vivax Duffy binding protein (PvDBP) in semi-immune Amazonian population

Plasmodium vivax requires interaction between Duffy binding protein (PvDBP) expressed by the parasite and Duffy antigen receptor for chemokines (DARC) expressed on the surface of erythrocytes. Due to the importance of PvDBP to ensure parasitism in erythrocytes, this antigen is an important vaccine candidate. Here, we carried-out a cohort study to evaluate antibody immune response against PvDBP and the risks associated with the acquisition and persistence of antibody response in a population of Mâncio Lima municipality, Acre state, Brazilian Amazon region. Overall, 1326 individuals were enrolled in this study, where 1100 individuals were enrolled at the baseline and 1120 individuals participated 16 months later. At the baseline, the frequency of malaria infection was 5,2% (57/1100), with predominance of P. vivax(74%). Regarding to antibody response, the frequency of PvDBPII ELISA-detected antibodies was 24,7% (272/1100), with age and lifetime malaria episodes (self-reported) independent variables associated with PvDBP seropositivity. Although low frequency of DBPII responders (15,8%, 177/1120) was detected at 16-months of follow-up, the study population could be classified as: (i) persistent non-responder (70,0%, 626/894) - individuals whose antibody response was not detectable at anytime; (ii) transient responder (17,4%, 156/894) – with temporary antibody response; and (iii) persistent responder (12,5%, 112/894) – positive antibody response during all the follow-up period. Logistic regression models identified malaria-exposure variables (age and life-time malaria history) as associated with the persistence of antibody response. In conclusion, the results confirm previous studies in the Amazon area showing that presence and persistence of antibody response to PvDBPII are associated with age and malaria history.