Antibody responses to P. falciparum Apical Membrane Antigen 1(AMA-1) in relation to haemoglobin S (HbS), HbC, G6PD and ABO blood groups among Fulani and Masaleit living in Western Sudan

Fulani and Masaleit are two sympatric ethnic groups in western Sudan who are characterised by marked differences in susceptibility to Plasmodium falciparum malaria. It has been demonstrated that Glucose-6-phosphate dehydrogenase (G6PD) deficiency and Sickle cell trait HbAS carriers are protected from the most severe forms of malaria. This study aimed to investigate a set of specific IgG subclasses against P. falciparum Apical Membrane Antigen 1 (AMA-1 3D7), haemoglobin variants and (G6PD) in association with malaria susceptibility among Fulani ethnic group compared to sympatric ethnic group living in Western Sudan. A total of 124 children aged 5–9 years from each tribe living in an area of hyper-endemic P. falciparum unstable malaria transmission were recruited and genotyped for the haemoglobin (Hb) genes, (G6PD) and (ABO) blood groups. Furthermore, the level of plasma IgG antibody subclasses against P. falciparum antigen (AMA-1) were measured using enzyme linked immunosorbent assays (ELISA). Higher levels of anti-malarial IgG1, IgG2 and IgG3 but not IgG4 antibody were found in Fulani when compared to Masaleit. Individuals carrying the HbCC phenotype were significantly associated with higher levels of IgG1 and IgG2. Furthermore, individuals having the HbAS phenotype were associated with higher levels of specific IgG2 and IgG4 antibodies. In addition, patients with G6PD A/A genotype were associated with higher levels of specific IgG2 antibody compared with those carrying the A/G and G/G genotypes. The results indicate that the Fulani ethnic group show lower frequency of HbAS, HbSS and HbAC compared to the Masaleit ethnic group. The inter-ethnic analysis shows no statistically significant difference in G6PD genotypes (P value = 0.791). However, the intra-ethnic analysis indicates that both ethnic groups have less A/A genotypes and (A) allele frequency of G6PD compared to G/G genotypes, while the HbSA genotype was associated with higher levels of IgG2 (AMA-1) and IgG4 antibodies. In addition, patients carrying the G6PD A/A genotype were associated with higher levels of specific IgG2 antibody compared with those carrying the A/G and G/G genotypes. The present results revealed that the Fulani ethnic group has statistically significantly lower frequency of abnormal haemoglobin resistant to malaria infection compared to the Masaleit ethnic group.