1 to 12.8%; p=0.008), an effect that was not observed in the equivalent samples from geohelminth-uninfected children (geomeans 15.0 and 12.8%, p=0.83; Fig. 2B). Significantly enhanced proliferation in response
to pRBC after Treg depletion was also seen in samples from helminth-infected (geomeans 8.8 to 12.7%; p=0.038) but not in those from helminth-uninfected children (geomeans 17.9 and 18.7%, p=0.87; Fig. 2B). No such differences were seen in response to uRBC (Fig. 2B). In geohelminth-infected subjects, proliferative responses to BCG and pRBC in depleted PBMC were equivalent to levels found in uninfected children. Interestingly, enhanced IFN-γ production in response to either BCG stimulation or pRBC stimulation after depletion was also only observed in samples from the geohelminth-infected children (geomeans for BCG 46.7 to 66.8 pg/mL and Torin 1 GPCR Compound Library order for pRBC 313.8 to 574.3 pg/mL; Fig. 2C), while IL-5 or IL-13 production was unchanged (data not shown). Geohelminth infections are usually found in areas co-endemic for multiple infectious agents and may increase susceptibility to other important tropical diseases such as malaria, HIV and tuberculosis 5. Furthermore the presence of geohelminths may impair responses to vaccines 11. These issues have recently lead to priority recommendations for the research agenda in Europe 12. To explore cellular immune mechanisms
underlying helminth-induced hyporesponsiveness, we have performed in vitro Treg depletion experiments with PBMC isolated from groups of geohelminth-infected and geohelminth-uninfected school children living in a rural area of Flores Island, Indonesia. The data presented here show lower proliferative responses to BCG and to pRBC in geohelminth-infected compared to uninfected children.
These effects were not associated with a concomitant higher number of FOXP3+Treg in those infected; however, T-cell proliferative responses to both BCG and pRBC were restored after Treg depletion. Depletion also enhanced IFN-γ responses to both stimuli, demonstrating a generalized suppression of Th1 cells by geohelminth-induced Fossariinae Treg. Although the observed suppression of immune responses in helminth infection was not associated with higher Treg numbers, our data do indicate increased functional Treg activity as a result of geohelminth infection. CD4+CD25hi T-cell depletion significantly enhanced specific immune responses to BCG and Plasmodium-infected RBC in infected individuals only, implying a specific immunomodulatory effect during persistent geohelminth infections. Proliferative and IFN-γ responses were not correlated, which indicates that increased cytokine production is not associated with higher cell numbers. This observation would suggest that Treg are indeed able to influence the capacity of individual cells to produce effector cytokines.