Effect of Interleukin 4 and Receptor Gene Polymorphisms in Relation to Oxidative Stress During Uncomplicated Malaria Infection

Abstract

Parasitic infections such as malaria in host organisms often lead to oxidative stress condition resulting in the constant generation of free radicals and other reactive species in vivo that lead to extensive oxidative damage in bio-molecules such as DNA and proteins. Susceptibility of Plasmodium parasite to oxidative stress is a well- established feature and advantage has been taken of this property to design some pro- oxidant anti-malarial drugs. This study was carried out with the aim of determining single nucleotide polymorphisms in interleukin (IL) 4 gene and its receptor gene, and their relationship to the generation of free radicals by the human host during uncomplicated malaria infection. The study population were one hundred subjects, reporting for medical care at the Polyclinic of the Korle Bu Teaching Hospital, Accra with uncomplicated malaria. Apparently healthy children (n = 41) without detectable malaria parasites were used as controls. Haematological analysis was done for all the study population. The gene regions containing the +33 C/T polymorphism of IL-4, and Pro-478-Ser of the IL-4Rα were amplified by Polymerase Chain Reaction (PCR) and the various genotypes determined by Restriction Fragment Length Polymorphism (RFLP) using the restriction enzymes (BsmF I for IL-4 and Kpn I for IL-4Rα gene regions respectively). Oxidative stress situations in the human host and its effect on malaria parasites were determined using the DNA comet assay determined by a commercial kit, and levels of reactive oxygen species in the infected RBCs of cases and uninfected controls was measured using the superoxide dismutase assay. A significant mean difference in neutrophil levels was observed when the uncomplicated malaria cases were compared with the controls (p = 0.001). It was observed that the mean Hb value of the control group did not differ significantly when compared with the cases (p = 0.07). Moderate to extensive DNA damage of the malaria parasite was demonstrated in increasing levels of estimated parasitaemia among the uncomplicated malaria cases, using the DNA comet assay. Significant correlation was observed between SOD levels and IL4R (Pro-478-Ser) (p = 0.017) polymorphism as well as between neutrophils and IL4 (+33) SNP (p = 0.002), indicating a likely interaction between the gene and neutrophil in parastite clearance in malaria infection, via the genotoxic effects of the super oxide anion.