Increased Plasmodium falciparum EBA175RIII-V antibody titres despite a 13-month malaria mass testing, treatment, and tracking intervention in a high malaria endemic community in Ghana

Background: Naturally acquired immunity (NAI) against malaria is developed through repeated exposure of humans to malaria parasites. Efforts to decrease malaria incidence can potentially alter the development of immunity. This work aimed to monitor total IgG titres against PfEBA-175RIII-V during the implementation of a quarterly mass testing, treatment, and tracking (MTTT) strategy in a high malaria transmission setting in Ghana. Methods: In total, 314 individuals aged 6 months–90 years participating in four quarterly MTTT studies were selected for this study. Finger-pricked blood was collected from each participant and used to prepare dried blood spots, which were used for molecular diagnosis of Plasmodium falciparum infection and elution of antibodies for serological evaluation of PfEBA-175RIII-V specific antibodies. Results: The infection prevalence by PCR was reduced from 56.2% at baseline to 46.8% at the end of the study. During the four MTTT rounds and surveys, 212 participants (67.5%) were infected at least once. Participants aged 10–14 years had the highest infection prevalence at the baseline and experienced a consistent decrease throughout the study. The overall antibody titers against PfEBA175RIII-V fluctuated during the study period, reaching the highest at the end of the study. Consistent with the age-dependent acquisition of host immunity against malaria parasites, a significant positive correlation was detected between age and anti-PfEBA175RIII-V IgG titres. Over the study period, infected participants also had significantly higher anti-PfEBA175RIII-V IgG titres than the uninfected. However, the number of times one is infected had a mixed impact on antibody titres to the PfEBA-175RIII-V antigen. Conclusions: Higher anti-PfEBA175RIII-V titres were associated with infection. The 13-month MTTT exercise in a malaria hyper-endemic community did not significantly reduce the titres of PfEBA-175RIII-V antibodies, and thus had no significant effect on NAI in relation to PfEBA-175RIII-V.