Human genetic polymorphisms and asymptomatic Plasmodium falciparum malaria in Gabonese schoolchildren

Several studies have focused their attention on the relationship between host genetic factors and susceptibility/resistance to severe malaria. However, there is a paucity of information concerning the role of host genetic factors in asymptomatic malaria, a form of low-grade Plasmodium falciparum infection without clinical symptoms. We investigated in this study the potential relationship between the host (human) genetic polymorphisms (glucose-6-phosphate dehydrogenase [G6PD], mannose binding lectin [MBL], tumor necrosis factor α [TNFα]-308 and -238, and nitric oxide synthase 2 [NOS2]-954) and the prevalence and profile of asymptomatic P. falciparum infection in 158 Gabonese schoolchildren. We found that G6PD A- heterozygous females (18 of 74) have a low prevalence of asymptomatic malaria (38.9% versus 67.3%; P = 0.03, by chi-square test). Children heterozygous for TNFα-238 (25 of 156) carry high number of diverse infecting parasite genotypes (2.5 versus 1.99; variance F = 3.05). No statistically significant association was found between MBL, TNFα-308, or NOS2 polymorphisms and asymptomatic malaria. Upon combining our data on asymptomatic forms with those from the literature for others forms, we conclude that G6PD A- heterozygous females are protected against all forms of P. falciparum malaria, and that the TNFα-238A allele confers protection against clinical malaria.