Cytokine expression during acute plasmodium falciparum infections of children resident in an endemic region of Western Kenya

Abstract

The brunt of malaria -related mortality is borne by children. One to two million children under the age 5 die of malaria annually in Africa, with between 2 to 5 million deaths occurring, worldwide. Many studies, both in rodent models and in humans, have documented the association of a variety of cytokines with malaria infections. To elucidate the relationship between cytokines and clinical forms of Plasmodium falciparum infections in children, plasma cytokine levels of TNF-, IFN-, IL-4 and IL-10 were compared in 150 children aged between 3-11 years, in a region of western Kenya, holoendemic for malaria. The results were categorized according to the clinical status of each child: aparasitaemic (healthy individuals with no detectable parasitaemia and no symptoms of malaria), asymptomatic (children with a sexual stage parasites, in their blood, but having no clinical symptoms of malaria) and symptomatic (children admitted to the local hospital with fever and parasitaemia but with no other concurrent infection). Parasite levels in symptomatic individuals were significantly higher than those of children in the asymptomatic group. Plasma concentrations of TNF-IL-10, of which substantial amounts were detected, were significantly higher (p<0.05) in symptomatic individuals compared to the other two groups. A positive correlation was also evident between the plasma levels of both cytokines (r=0.4316, p<0.0001). Overall, only low levels of IFN- and IL-4 were detected, and there were no differences evident in the plasma concentrations of these cytokines, between the three groups. Thus, in a holoendemic area of malaria, TNF- and IL-10 levels correlate with symptomatic malaria infections of children. In contrast, IFN- and IL-4, do not seem to be useful predictors of clinical infection.