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.

[Humoral immune anti-Plasmodium falciparum AMA1 and MSP1 response in two ethnic groups living in sympatry in Mali]. / Réponse humorale anti-Plasmodium falciparum AMA1 et MSP1 dans deux groupes ethniques vivant en sympatrie au Mali.

Fulani of Mali are known for their lower susceptibility to Plasmodium falciparum malaria than their neighbours, the Dogon, despite similar transmission conditions. However, the mechanisms underlying these differences are poorly understood, particularly those concerning antigenspecific immune responses. The Apical Membrane Antigen 1 (AMA1) and the Merozoite Surface Antigen 1 (MSP1) are two malaria vaccine candidates, which play a pivotal role during the invasion of parasites into erythrocytes, and in the case of AMA1, of hepatocytes. Therefore, we analyzed the level of anti-AMA1 and anti-MSP1 antibodies (FVO and 3D7 alleles), by using ELISA (Enzyme Linked Immuno Sorbent Assay) to investigate whether there are differences between the two ethnic groups. Our results show that the splenic rate, the level of anti-AMA1 and anti-MSP1 were significantly higher in Fulani compared to Dogon; while the parasite rate was lower in Fulani group compared to Dogon. Our results suggest that the lower susceptibility of Fulani to malaria could be due to the higher specific humoral responses against AMA1 and MSP 1 in Fulani's ethnic group compared to Dogon.