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 wellestablished

feature and advantage has been taken of this property to design some prooxidant

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.

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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.