Schistosomiasis co-infection in humans influences inflammatory markers in uncomplicated Plasmodium falciparum malaria

Malaria and schistosomiasis are the two major parasite diseases present in developing countries. The epidemiological co-infection with schistosomiasis could influence the development of the physiological reaction associated with Plasmodium falciparum infection in human. Most studies have demonstrated the association of circulating levels of interferon-γ (IFN-γ), tumour necrosis factor-a (TNF-α), interleukin-10 (IL-10), transforming growth factor (TGF-β) and soluble Tumour Necrosis Factor Receptors (sTNF-RI and sTNF-RII) with the morbidity of malaria. In the present study, we showed that Schistosoma haematobium co-infection influences, in an age-dependent manner, the unbalance between pro- and anti-inflammatory circulating cytokines that play a key role during malaria infection. Indeed, children co-infected by S. haematobium have higher levels of IFN-γ and sTNF-RII than children infected only by P. falciparum. In contrast, co-infected adults presented a significant increase of IFN-γ, IL-10, TGF-β, sTNF-RI and sTNF-RII rates and IL-10/TNF-α ratio. Taken together, this study indicates that schistosomiasis co-infection can unbalance the regulation of inflammatory factors in uncomplicated P. falciparum malaria. The possible consequences of the schistosomiasis co-infection for age-dependent malaria morbidity are discussed.