Magnitude and longevity of antibody responses to key Plasmodium vivax Erythrocyte Binding–Like proteins in an amazonian cohort: a long-term follow-up study

Plasmodium vivax , the second most common cause of malaria, remains a significant public health concern, with no vaccine approved to date. Although the DBL domain of Duffy binding protein (DBPII) is a leading blood-stage candidate, its extensive polymorphism, allele-specific immune responses, and low immunogenicity limit its effectiveness. In contrast, EBP2, a DBP homologue, emerges as a promising vaccine target due to its lower genetic variability and potential role in a distinct invasion pathway. Here, a long-term cohort of malaria-exposed individuals from the Amazon enabled the comparison of the magnitude and longevity of naturally acquired antibody responses to the DBL domains of EBP2 and DBP. A 15-years follow-up study was carried out among long-term P. vivax exposed Amazonian individuals (363, median age 36 years) and included 10 cross-sectional surveys at periods of high and low malaria transmission. The experimental approach focused on the longitudinal monitoring of IgG antibodies against the full DBL domains of EBP2 and DBP, as assessed by conventional serology (ELISA). Antibody durability was estimated by time to the first documented loss of seropositivity (Kaplan–Meier), while repeated serological measurements over follow-up (GLMM) identified factors associated with seropositivity. Regardless of the malaria transmission period, IgG reactivity and seroprevalence were consistently higher for EBP2 than DBPII. EBP2-dominant IgG antibody profile was detected in 68–88% of individuals, compared to 9–30% for DBPII. The median time of the first loss of DBPII seropositivity was estimated at 72 months, with EBP2 seropositivity remained above 50% throughout the 180-month follow-up period. Although time living in the study area was associated with antibody response to both antigens, malaria infection — predominantly submicroscopic — was identified as an independent predictor of anti-EBP2 IgG seropositivity. EBP2 induces more robust and long-lasting IgG antibody responses than DBPII, even in the absence of frequent reinfection-induced boosting. Further studies are warranted to determine the protective role of naturally acquired anti-EBP2 antibodies in the Amazonian population.