Abstract
BackgroundIn endemic areas, children develop slowly and naturally anti-Plasmodium antibodies and become semi-immune. Seasonal Malaria Chemoprevention (SMC) with sulfadoxine-pyrimethamine + amodiaquine (SPAQ) is a new strategy to reduce malaria morbidity in West African young children. However, SMC may impact on the natural acquisition of anti-Plasmodium immunity. This paper evaluates the effect of SMC with SPAQ on antibody concentration in young children from Niger.MethodsThis research was conducted in areas benefitting from SMC since 2014 (Zinder district), without SMC (Dosso district), and with 1 year of SMC since 2016 (Gaya district). To assess the relationship between SMC and Plasmodium falciparum IgG antibody responses, the total antibody concentrations against two P. falciparum asexual stage vaccine candidate antigens, circumsporozoite protein (CSP) and glutamate-rich protein R2 (GLURP-R2), in children aged 3 to 59 months across the three areas were compared. Antibody concentrations are quantified using an enzyme-linked immunosorbent assay on the elution extracted from positive and negative malaria Rapid Diagnostic Test cassettes.ResultsThe analysis concerns two hundred and twenty-nine children aged from 3 to 59 months: 71 in Zinder, 77 in Dosso, and 81 in Gaya. In Zinder (CSP = 17.5 µg/ml and GLURP-R2 = 14.3 µg/ml) median antibody concentration observed are higher than in Gaya (CSP = 7.7 µg/ml and GLURP-R2 = 6.5 µg/ml) and Dosso (CSP = 4.5 µg/ml and GLURP-R2 = 3.6 µg/ml) (p < 0.0001).ConclusionThe research reveals some evidences which show that seasonal malaria chemoprevention with SPAQ has an effect on blood stage antibody responses and pre-erythrocytic stage of P. falciparum infections in Niger. Increased antibody titres with increased SMC/SPAQ implementation. This contradicts hypothesis that SMC/SPAQ could reduce immunity to erythrocyte and liver-stage antigens. Further studies are necessary to provide better understanding of the SMC effect on malaria immunity.
Highlights
In endemic areas, children develop slowly and naturally anti-Plasmodium antibodies and become semi-immune
This study demonstrates that seasonal malaria chemoprevention with sulfadoxine-pyrimethamine + amodiaquine (SPAQ) has an effect on blood stage antibody responses and pre-erythrocytic stage of P. falciparum infections in Niger
The total IgG antibodies to liver-stage vaccine candidate antigen circumsporozoite protein (CSP) and blood stage antigen GLURP-R2 are significantly higher in Zinder where Seasonal Malaria Chemoprevention (SMC) has been implemented for 3 years, as opposed to Gaya, where SMC has been implemented for a year, and Dosso, as well, which has never benefitted from SMC
Summary
Children develop slowly and naturally anti-Plasmodium antibodies and become semi-immune. Seasonal Malaria Chemoprevention (SMC) with sulfadoxine-pyrimethamine + amodiaquine (SPAQ) is a new strategy to reduce malaria morbidity in West African young children. Without SMC interventions, children slowly develop anti-malarial antibodies, naturally becoming semi-immune [7, 8]. Sulfadoxine is an antibacterial and anti-malarial drug of the chemical class of sulfonamides. It is a dihydropteroate synthetase (dhps) inhibitor, a key enzyme in the biosynthesis of folate. It acts by competitive inhibition of para amino benzoic acid (PABA) to block the synthesis of folic acid and Plasmodium nucleotides (purines and pyrimidines). SP acts on the asexual forms of the hepatic and erythrocytic stage of Plasmodium
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