Evaluation of human CYP2C8 genetic variation related to amodiaquine/chloroquine metabolism in children of two areas of Uganda exposed to Plasmodium falciparum malaria

Objectives. Aim of this study was to investigate cytochrome P450 2C8 (CYP2C8) poor metaboliser allele frequency in two areas of Uganda with endemic Plasmodium falciparum malaria. CYP2C8, a polymorphic enzyme that mainly contributes to the hepatic metabolism of amodiaquine (AQ) and chloroquine (CQ), shows two important genetic variants in African populations: CYP2C8*2 (rs11572103, 805A/T) is the allele most common in East and West Africans and associated to a poor metaboliser phenotype in subjects carrying at least one copy of the defective allele, and CYP2C8*3 (rs11572080, 416G>A and rs10509681, 1196A>G), a very defective allele only found in Zanzibar islands (Tanzania).Human genetic variation affecting pharmacokinetic could represent a further cofactor in the spread of drug resistant P. falciparum malaria. Methods. A total of 261 children and adolescents had been enrolled and genotyped for the single nucleotide polymorphisms rs11572103, rs11572080 and rs10509681. Samples were collected during cross-sectional surveys performed in Uganda (Karamoja and Kampala regions). Fingerpick blood samples were spotted on Whatman grade 1 filter papers at the time of the field survey and then air dried before being separately stored in sealed plastic containers. The PCR-RFLP technique was used to discriminate the wildtype from the defective alleles. Results. The CYP2C8*2 allele frequency (± SE) in rural sites of Karamoja region (North-Eastern Uganda) was 0.10 ± 0.02, while was 0.13 ± 0.03 in the Kampala suburbs (central Uganda). Both the genotype distributions are in Hardy-Weinberg equilibrium, and the allele frequencies are not statistically different (Yates corrected χ2=0.89, P=0.346). The overall CYP2C8*2 frequency in all sites was 0.10 ± 0.02. The allele CYP2C8*3 was absent for all the populations studied. Conclusion. Our study confirms that CYP2C8*2 allele is widespread in Africa and is present at an appreciable frequency also in Uganda, an area of meso-endemic malaria transmission. Moreover, the absence of the CYP2C8*3 allele is a confirmation that it is a marker of genetic admixture of the Zanzibar population with a Caucasoid component. Antimalarial treatment in Uganda is based on artemisinin combination therapies (ACTs) with artesunate (AS) plus AQ being used as second line ACT. Consequently, the presence of the CYP2C8*2 allele may be a potential co-factor in the onset of adverse side effects associated with AQ administration. Furthermore, we emphasize the risk related to the presence of CYP2C8*2 in selecting AQ-resistant strains, since the interplay between host and parasite genetic variation could act as selective co-factor for drugresistant parasite strains.