Antibody responses and Fc gamma receptor IIa polymorphism in relation to Plasmodium falciparum malaria

Abstract: Immunity to asexual blood-stage of Plasmodium falciparum malaria is believed to be associated with protective antibodies of certain immunoglobulin classes and subclasses. This thesis addressed the importance of antibodies in relation to malaria infection and their effective interactions with Fc gamma receptor IIa (FcyRIIa) polymorphisms. Our data indicate that the frequency of FcyRIIa-R/R131 genotype was statistically significantly higher in Sudanese patients with severe malaria, while the FcyRIIa-H/H131 genotype showed a significant association with mild malaria. The levels of IgG1 and IgG3 subclass antibodies were statistically higher in the mild malaria patients.The Fulani ethnic group in West Africa has been shown to be relatively resistant to malaria. We investigated the possible impact of FcyRIIa polymorphisms in the Fulani and non-Fulani in Mali and Sudan, and analysed their malaria-reactive IgG subclass profiles. The FcyRIIa-H/H131 genotype and H131-allele were found to be prevalent in the Fulani while R131-allele was prevalent in non-Fulani. The Fulani had higher serum levels of IgG1-3, with higher proportion of IgG2 than the non-Fulani.Most clinico-epidemiology studies have been in areas with holo- and hyper-malaria endemicity. We have analysed antibody responses to a panel of six blood-stage antigens in relation to clinical malaria outcome in mesoendemic Sudan. Our results revealed a linear association with anti-AMA-1 IgG1 antibodies and reduced risk of severe malaria while a non-linear relationship with IgG3 antibodies was observed for MSP-2, MSP-3 and GLURP. In the combined final model, the highest levels of IgG1 subclass antibodies to AMA-1, GLURP-R0, and the highest levels of IgG3 subclass antibodies reactive to 3D7 MSP-2 were independently associated with a reduced risk of clinical malaria.Taken together, these data suggest a possible association between FcyRIIa-R/H131 and anti-malarial antibody responses in the clinical outcome of malaria.