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/FYBES and FYB/FYBES 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*FYBES/FYBES 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. •Evidence of the action of natural selection on HbS and Duffy genes is presented.•The highest fitness value occurs for the AS*FYBES/FYBES genotypic combination, and this present linkage disequilibrium.•There is a positive and significant correlation between the AS and FYBES/FYBES genotypes and their alleles.•D'ST2 > D'IS2 was found, indicating that DL found is mostly caused by natural selection, rather than local differentiation.