Effect of seasonal malaria chemoprevention on the acquisition of antibodies to Plasmodium falciparum antigens in Ouelessebougou, Mali

Abstract

BackgroundSeasonal malaria chemoprevention (SMC) is a new strategy to reduce malaria burden in young children in Sahelian countries. It consists of the administration of full treatment courses of sulfadoxine–pyrimethamine plus amodiaquine to children at monthly intervals during the malaria season. However, it is not clear if there is a cumulative effect of SMC over time on acquisition of antibodies to malaria antigens.MethodsA cross-sectional serosurvey was carried out 1 month after the last dose of SMC in 2016. Children aged 3–4 years were randomly selected from areas where SMC was given for 1, 2 or 3 years during the malaria season. Children in the areas where SMC had been implemented for 1 year but who failed to receive SMC were used as comparison group. Antibody extracted from dry blood spots was used to measure IgG levels to CSP, MSP-142 and AMA1.ResultsThe prevalence of antibodies to AMA-1 were high and similar in children who received SMC for 1, 2 or 3 years and also when compared to those who never received SMC (96.3 vs 97.5%, adjusted OR = 0.99, 95% CI 0.33–2.97, p = 0.99). The prevalence of antibodies to MSP-142 and to CSP were similar in children that received SMC for 1, 2 or 3 years, but were lower in these children compared to those who did not receive SMC (87.1 vs 91.2%, adjusted OR = 0.55, 95% CI 0.29–1.01, p = 0.05 for MSP-142; 79.8 vs 89.2%, adjusted OR = 0.52, 95% CI 0.30–0.90, p = 0.019 for CSP).ConclusionsSMC reduced seropositivity to MSP-142 and CSP, but the duration of SMC did not further reduce seropositivity. Exposure to SMC did not reduce the seropositivity to AMA1.

Some evidence that seasonal malaria chemoprevention with SPAQ has an effect on blood stage antibody responses and pre-erythrocytic stage of Plasmodium falciparum infections in Niger.

“…The concentrations of both antibodies against CSP and GLURP-R2 showed an increase with SMC implementation probably as a result of decrease of either liver-stage maturation or erythrocyte stage by SPAQ. This is contrasting with other studies [14], [13], [28], [12] which found a decrease in the titers of antibodies after SMC delivery. Previous studies established that chemoprophylaxis conferred protective immunity against reinfections when anti-malaria drugs are not present [29], [30], [31].…”

“…SMC was primarily directed against bloodstage parasites, because sulfadoxine-pyrimethamine and amodiaquine association inhibits the erythrocyte stage and liver-stage, which may contribute to increase the titer of IgG against the antigen of these stages. This nding is contrasting with a recent study published SMC reduced antibody against liver-stage antigens MSP-142 and CSP in malaria journal by Mahamar et al [14]. Others studies demonstrated that sulfadoxine does not affect liver stages, pyrimethamine has some inhibitory effect on liver stages in P. yoelii models [24] but there are high levels of resistance to pyrimethamine in SMC countries [25].…”

“…The total number of children to include was 249, and calculated based on 78% circumsporozoite protein antibody prevalence in children that received SMC for 1, 2 or 3 years [14] (95% CI) with a precision of 5%.…”

“…In Mali, Mahamar et al, concluded that exposure to SMC/SPAQ decreasing of anti-AMA-1, MSP1_ 42 and CSP titers [14]. Other Malian study conclude that duration of exposure to SMC had no effect on antibody to MSP1_ 42 and CSP [14].…”

“…In the same country, Sylla et al, showed that SMC with SPAQ can induce decreasing of IgG anti-AMA1 and anti-MSP1_ 42 [13]. In Mali, Mahamar et al, concluded that exposure to SMC/SPAQ decreasing of anti-AMA-1, MSP1_ 42 and CSP titers [14]. Other Malian study conclude that duration of exposure to SMC had no effect on antibody to MSP1_ 42 and CSP [14].…”