CD39 expression by regulatory T cells participates in CD8+ T cell suppression during experimental Trypanosoma cruzi infection.

An imbalance between suppressor and effector immune responses may preclude cure in chronic parasitic diseases. In the case of Trypanosoma cruzi infection, specialized regulatory Foxp3+ T (Treg) cells suppress protective type-1 effector responses. Herein, we investigated the kinetics and underlying mechanisms behind the regulation of protective parasite-specific CD8+ T cell immunity during acute T. cruzi infection. Using the DEREG mouse model, we found that Treg cells play a role during the initial stages after T. cruzi infection, restraining the magnitude of CD8+ T cell responses and parasite control. Early Treg cell depletion increased the frequencies of polyfunctional short-lived, effector T cell subsets, without affecting memory precursor cell formation or the expression of activation, exhaustion and functional markers. In addition, Treg cell depletion during early infection minimally affected the antigen-presenting cell response but it boosted CD4+ T cell responses before the development of anti-parasite effector CD8+ T cell immunity. Crucially, the absence of CD39 expression on Treg cells significantly bolstered effector parasite-specific CD8+ T cell responses, preventing increased parasite replication in T. cruzi infected mice adoptively transferred with Treg cells. Our work underscores the crucial role of Treg cells in regulating protective anti-parasite immunity and provides evidence that CD39 expression by Treg cells represents a key immunomodulatory mechanism in this infection model. Author summary: Chagas disease, caused by Trypanosoma cruzi, can result in severe health complications. While the exact mechanisms underlying the disease's pathogenesis remain incompletely understood, the host's inflammatory immune response is believed to play a critical role. To shed light on disease mechanisms and potential treatments, we investigated the impact of regulatory T (Treg) cells on the development of effector immune responses against T. cruzi. Our findings reveal that Treg cells dampen parasite-specific CD8+ T cells, a crucial arm of the immune response in counteracting the parasite. Notably, this regulatory influence occurs primarily during the early stages of T. cruzi infection. Furthermore, we observed that while Treg cells have minimal effects on antigen-presenting cells, they modulate the magnitude and phenotype of conventional CD4+ T cells. Importantly, we identified CD39, a molecule involved in the purinergic pathway, as essential for the suppressive functions of Treg cells during T. cruzi infection. Our findings enhance the understanding of the regulatory response during the acute phase of T. cruzi infection and may have implications for the development of novel therapeutic strategies. [ABSTRACT FROM AUTHOR]