mansoniandS. treatment IL-4 cytokine levels were negatively correlated with baseline contamination status (p<0.001). The results suggest that treatment-induced immune responses are comparable for both commonantischistosome drugs praziquantel or oxamniquine having comparable and immunizing effect. == Introduction == Schistosome infections under various field and experimental settings have suggested that hosts develop some acquired immunity to the parasite15. In humans this specific acquired immunity develops gradually over several years6,7, and results of one study seem to suggest that treatment with praziquantel speeds up the development of schistosomespecific acquired immunity8. Praziquantel or oxamniquine treatment of schistosome-infected people alters parasite specific cellular and humoral responses particularly in children (810). These treatment-induced changes have been associated with resistance to re-infection1114. The main cytokines which mark each subset are IL-4 and IFN- and these have a reciprocal cross-inhibitory effect. The relative importance of these functionally distinct T cell subsets and their contribution to protective immunity has yet to be fully established for the different schistosomes affecting humans during acute contamination and post treatment. However, from recent reports, protection (against schistosome contamination??) has been associated with Th2 responses, while Th1 responses cannot be related to susceptibility but a developmental stage after exposure1517. A range of cytokines are now documented to be produced by the effector T helper cells. Furthermore, observations that this regulatory arm of the immune system develops with sustained exposure to schistosomes and their products suggest that they are likely to play R1487 Hydrochloride a role during the establishment and maintenance of the infected condition. This re-infection study showed the cytokine profiles that appear before treatment and the change in the period following treatment with either praziquantel or oxamniquine. The knowledge thus gained should be helpful in understanding how the immune response is usually modulated during contamination with S.mansoni and following treatment with either praziquantel or oxamniquine. Recently we showed that ratios of IL-4:IFN- increased in S. haematobium-infected children after treatment with praziquantel15,16. The study also showed a significant increase in cell proliferation after treatment. This suggests that treatment-induced immune changes are more complicated involving much more than just cytokine increases or decreases.16 Previous studies have examined factors, which affect the changes in immune responses following treatment and how they affect re-infection rates4,5,11,12,1519. These studies mostly dealt with praziquantel or oxamniquine and not many compared the effect of the commonly used drugs in S.mansoni and in mixed schistosome infections. However, to date, there have been no studies of the nature of treatment-induced immune changes. Characterisation of these changes is important for a better understanding of how schistosome-specific acquired immunity develops and is essential for RELA vaccine development and schistosomiasis control. We compared the cell-mediated immune changes in Zimbabwean subjects treated with two types of drugs which have different modes of action. Praziquantel acts by interfering with the Ca2+ uptake, causing R1487 Hydrochloride muscle contraction and worm paralysis20. This causes tegumental damage and eventually worm death. Oxamniquine acts by binding to worm DNA causing an irreversible inhibition of nucleic acid synthesis20,21. R1487 Hydrochloride The two drugs were used to determine if there is any drug related differences in the changes in immune responses in treated children. == Methods == == Study Ethical Approval == The Medical Research Council of Zimbabwe approved the study protocol. The Provincial and District Medical Directors and the District Health Executive Board gave permission to conduct the study. Parents and guardians of the participants agreed that this informed verbal consent obtained was sufficient. Treatment was offered to all infected participants after initial screening and to all participants at the end of the study. == Study site and sample collection == The study was conducted between 2002 and 2004 and recruited individuals attending school in Chiredzi, South Eastern Zimbabwe, where S.haematobium and S. mansoni is usually endemic. A total of 410 school going individuals aged between 6 and 18 years were surveyed after the aims of the study had been.