Cytokine pattern during asymptomatic Anaplasma spp. infections and effect of co-infections by malaria and helminths in schoolchildren of Franceville, southeastern Gabon.

BACKGROUND: Asymptomatic infections by Anaplasma spp. and the basis of the immune response during these infections have not yet been established. This study investigated the inflammatory cytokine responses during Anaplasma spp. infection in school children and the effect of co-infection with Plasmodium spp. and helminths. METHODS: Blood and stool samples were taken from children aged 5 to 17 years. Parasitological diagnosis was carried out by RDT and microscopy, while microscopy and PCR were used to diagnose infection by Anaplasma spp. Plasma was used for cytokine assays using the ELISA technique. RESULTS: A total of 219 children were included in the present study, of whom 205 were infected with Anaplasma spp. and 14 were uninfected. Levels of IL-6, IL-22 and TGF-β were lower not only in children mono-infected with Anaplasma spp. but also in those co-infected with Anaplasma spp. and Plasmodium spp., Anaplasma spp. and helminths, and Anaplasma spp., Plasmodium spp. and helminths compared to controls. However, higher levels of IL-6 and IL-22 were observed in children mono-infected with Anaplasma spp. compared to those co-infected with Anaplasma spp. and helminths. The latter group also had lower levels of IL-6, IL-22, TGF-β and IL-10 than children co-infected with Anaplasma spp. and Plasmodium spp. In addition, children co-infected with Anaplasma spp. and helminths had also lower TGF-β and IL-10 levels than children co-infected with Anaplasma spp., Plasmodium spp. and helminths. An increase of IFN-γ and IL-10 were observed in children co-infected with Anaplasma spp. and Plasmodium spp. compared to those mono-infected with Anaplasma spp. Finally, the results showed that febrile children infected with Anaplasma spp. had higher levels of IFN-γ and lower levels of TGF-β than afebrile children. CONCLUSIONS: These results suggest that infection with Anaplasma spp. downregulates cytokines including IL-6, IL-22 and TGF-β and that co-infection with Plasmodium spp. might have a protective effect on the host, while co-infection with helminths might have a negative effect.