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Cryptococcus -associated immune reconstitution inflammatory syndrome (C-IRIS) is identified upon immune reconstitution in immunocompromised patients, who have previously contracted an infection of Cryptococcus neoformans ( Cn ). C-IRIS can be lethal but how the immune system triggers life-threatening outcomes in patients is still poorly understood. Here, we establish a mouse model for C-IRIS with Cn serotype A strain H99, which is highly virulent and the most intensively studied. C-IRIS in mice is induced by the adoptive transfer of CD4 + T cells in immunocompromised Rag1 -deficient mice infected with a low inoculum of Cn. The mice with C-IRIS exhibit symptoms which mimic clinical presentations of C-IRIS. This C-IRIS model is Th1-dependent and shows host mortality. This model is characterized with minimal lung injury, but infiltration of Th1 cells in the brain. C-IRIS mice also exhibited brain swelling with resemblance to edema and upregulation of aquaporin-4, a critical protein that regulates water flux in the brain in a Th1-dependent fashion. Our C-IRIS model may be used to advance our understanding of the paradoxical inflammatory phenomenon of C-IRIS in the context of neuroinflammation.

The AP-1 factor, basic leucine zipper transcription factor, ATF-like (BATF) is important for CD4+ T-helper (Th) 17, Th9 and follicular T helper (Tfh) cell development. However, its precise role in Th2 differentiation and function remains unclear, and the necessity of BATF in non-allergic settings of type-2 immunity has not been explored. Here, we show that in response to parasitic helminths, Batf−/− mice are unable to generate both Tfh and Th2 cells. As a consequence, Batf−/− mice fail to establish productive type-2 immunity during primary and secondary infection. Batf−/− CD4+ T cells do not achieve type-2 cytokine competency, which implies that BATF plays a key role in the regulation of interleukin(IL)-4 and IL-13. In contrast to Th17 and Th9 cell subsets where BATF binds directly to promoter and enhancer regions to regulate cytokine expression, our results show that BATF is significantly enriched at Rad50 hypersensitivity sites (RHS) 6 and 7 of the locus control region (LCR) relative to AP-1 sites surrounding type-2 cytokine loci in Th2 cells. Indeed, Batf−/− CD4+ T cells do not obtain permissive epigenetic modifications within the Th2 locus, which have been linked to RHS6 and RHS7 function. In sum, these findings reveal BATF as a central modulator of peripheral and humoral hallmarks of type-2 immunity, and begin to elucidate a novel mechanism by which BATF regulates type-2 cytokine production through its modification of the Th2 LCR.

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