Joint selection for two malaria resistance mutations in a south-west Colombian population

In regions with an Afro-descendant population and where malaria is endemic, high frequencies of polymorphisms have been found that confer resistance to this disease, such as the haemoglobin S (HbS) and Duffy genes, which provide resistance to P. falciparum and P. vivax infection, respectively. The objective of this study was to evaluate the individual and joint selection actions of these two genes in an Afro-descendant Colombian population. A total of 819 individuals were analysed using stratified random sampling. PCR-RFLP and Hardy-Weinberg equilibrium deviation analysis (H-W eq.), linkage disequilibrium (LD), D'_IS² and D'_ST² indexes, neutrality tests, correlations and fitness were performed using Arlequin 3.5.2.2 and R 3.4.1 software. In general, the population showed neutrality and H-W eq. for the HbS gene but not for the Duffy gene (FYA/FYB, FYA/FYB^ES and FYB/FYB^ES genotypes were responsible for this deviation). LD between the HbS locus and the promoter region of the Duffy gene, a value D'_IS² = 0.001 and D'_ST² = 0.020 was found, an increase in fitness of the AS*FYB^ES/FYB^ES genotype combination (marked in adolescents and adults), and a strong correlation between these genotypes (Rho = 90%, p = .001) were found, evidencing a possible joint selection action for these two alleles. This work presents evidence of the action of natural selection, both individually and jointly, on malaria resistance genes, HbS and Duffy, in the Buenaventura population.