The World Health Organization (WHO) has estimated that there were 435,000 malaria related deaths in 2017. The disease is a long-standing global health threat that currently affects more than 219 million people in a total of 100 nations. The unicellular eukaryotes Plasmodium falciparum and P. vivax obligate parasites cause malaria, with children aged under 5 years accounting for the majority of deaths due to severe malarial anemia, hemoglobinuria, and cerebral malaria.
Single-nucleotide polymorphisms (SNPs) in the tumor necrosis factor-alpha (TNFα) gene are associated with an increase in severe malarial anemia in P. falciparum infected patients. Certain evidence also points to a possible role of IL-22 in the biology of P. falciparum infections. A study led by Ahmed A. Al-Qahtani of the Alfaisal University School of Medicine, Riyadh, Saudi Arabia investigated the role of IL-22 gene variation in the severity of P. falciparum malaria. The results of the study were published in the journal Mediators of Inflammation.
The Malaria Center in the Jazan region, located in the southwest of Saudi Arabia was the collection site for blood from 250 P.falciparum infected patients. The control group was 200 randomly selected uninfected healthy individuals.
Nine SNPs of IL-22 were examined. There were significant differences in the IL-22 variants between the infected and control groups. The rs2227481 TT genotype, the T allele and the rs2227483 AT genotype was associated with the control group and thus inferred as protective against P.falciparum infection.
Limitations of the study include that only nine Il-22 SNPs were examined and that the molecular mechanism of the observations linking IL-22 polymorphisms to malaria severity were not investigated. It remains to be seen whether the results can be replicated in different populations.
“Our data shows that the IL-22 rs2227481 TT genotype and T allele and the rs2227483 AT genotype and A allele may be associated with protection against P. falciparum malaria. The IL-22 promoter polymorphism in rs2227513 G allele appears to be associated with higher expression levels of IL-22, which could play a role in the protection against the disease. These findings will increase the current understanding of the mechanisms involved in the pathogenesis of malaria infection,” concluded the authors.