Antibody Responses Generated Against P. Falciparum and A. Gambiae Antigens in Suspected Malaria Patients with Variant Haemoglobin Genotypes

Abstract

HbAS and HbAC are known to be protective against P. falciparum infection, but it is unclear how this protection is conferred in malaria symptomatic patients in Ghana. Theoretically, HbAS and HbAC protect against P. falciparum malaria by improving naturally acquired immunity to the parasite. Also, Immunoglobulin G (IgG) has played a significant role in blood parasite clearance in individuals infected with P. falciparum, suggesting the protective mechanism of the acquired immunity. This study investigated haemoglobin genotypes and their effects on IgG levels in symptomatic malaria. This research was a nested archival cross-sectional study that enrolled 600 symptomatic malaria patients aged between 2 to 89 from the ten regions in Ghana. Parasite species and density were determined, followed by haemoglobin phenotyping for malaria microscopy-positive patients. An indirect enzyme-linked immunosorbent assay (ELISA) was performed on all the samples to examine the differential effects of exposure to Anopheles mosquitoes (gSG6-P1), sexual stage malaria parasites (Pfs230), and asexual stage malaria parasites (EBA 175 3R). The haemoglobin variants observed among malaria microscopy-positive patients in eight regions of Ghana were HbAA, HbAC, HbSC, HbAS, HbSS, HbCC, and HbAF. In conclusion, there were significant differences in the total concentration of anti-EBA 175 3R and anti-gSG6-P1 antibodies in malaria negative and positive microscopy samples. Although a significant association was established between the concentrations of IgGs measured against the various antigens in different haemoglobin variants in malaria microscopy positive samples, it was clear that the number of participants with IgG against gSG6-P1 antigen was significantly greater in HbAA participants than in the other haemoglobin variants. Yet the same assessment could not be made for the sexual stage antigen (Pfs230) and the erythrocyte binding antigen (EBA 175 3R). In general, no significant relationships were established between the influence of age, gender, and haemoglobin variants on the anti-Pfs230, anti-EBA 175 3R, and anti-gSG6- P1 antibodies.