In this context, a pre-existing S. mansoni infection was shown to suppress Th1 response and to impair control of L. major (28) and L. donovani (29) infection in C57BL/6 mice. Also, co-infection with tapeworm Taenia crassiceps led to increased lesions sizes upon subsequent L. major and L. mexicana infection in BALB/c mice (30). In conclusion, the helmith/Leishmania co-infection studies demonstrating impaired control of Leishmania

(28–30) used helminths that induced long-lasting or even chronic infections while the ones including our own, reporting still intact host defence upon co-infection used either transient or semi-permissive helminth infection models (22,23,31). One study describing efficient control of L. major in BALB/c and C57BL/6 mice carrying previous S. mansoni infections used Gefitinib in vivo an extremely high L. major infection dose (4 × 107 promastigotes) that might have functioned as a very potent Th1 inducer, even in the presence of chronic helminth infection (31). The diversity of these results highlights the importance of all protagonists involved for the final outcome of co-infections that is, as pointed out above, helminth species, Leishmania infection doses and genetic background of the host mice (32). As this reflects the diversity of human population and their parasites, we argue that important knowledge YAP-TEAD Inhibitor 1 research buy is extracted from all these

different co-infection models, despite heterogeneous results. Regarding the reciprocal impact of L. major infection on the nematode infection, we did observe a suppression of the local S. ratti-specific Th2 response. To our surprise, this suppression was detectable in the mesLN after 2 days of subsequent co-infection with L. major but not if L. major infection preceded S. ratti infection by 14 days. This clearly shows that the establishment of a protective local S. ratti-specific Th2 response was not impaired if an S. ratti co-infection took place in

mice with a fully established L. major-specific Th1 response. The S. ratti-specific Th2 response in the mesLN, however, is transient and starts to decline by day 8 p.i. (10). From next this data we conclude that an L. major co-infection that was established at day 6 post-S. ratti infection accelerated the decline of the S. ratti-specific response, thus resulting in the observed reduction in Th2 cytokines in co-infected mice. Here, it is of special interest that a local infection such as L. major is usually restricted to the draining, i.e. the popLN displayed a systemic effect by changing cytokine responses in the mesLN. Interestingly, the reduced S. ratti-specific Th2 response observed upon L. major co-infection was still sufficient to allow efficient nematode expulsion, as we showed by unchanged worm burden. The artificial interference with Strongyloides-induced Th2 polarization, in contrast, has been shown to interfere with host defence.