Immunological Mechanisms of CD4+T Lymphocyte Exhaustion in Disseminated Cryptococcal Infection

This study aims to investigate the role of CD4+T lymphocyte exhaustion in disseminated Cryptococcal infection among HIV-negative hosts. Results showed peripheral blood CD4+T lymphocytes in Cryptococcal infetion patients exhibited significantly higher expression levels of multiple exhaustion markers (PD-1, CTLA-4, Tim-3, Lag-3) compared to the healthy control group (P<0.05). Furthermore, patients with cryptococcal meningitis demonstrated higher expression of CD4+ T lymphocyte exhaustion markers compared to those with pulmonary cryptococcal infection (P<0.05). Furthermore, in the murine model, compared to the normal group, infected mice exhibited significantly elevated levels of exhaustion markers PD-1 and Tim-3 on CD4+ T lymphocytes, accompanied by a decline in cytokine secretion ability starting from day 42. Single-cell sequencing analysis revealed that among the reported exhaustion-associated genes, only NR4A exhibited significantly higher expression in CD4+ T lymphocytes compared to the control group. Further analysis of NR4A expression in lung CD4+ T lymphocytes of mice demonstrated an increase over time post-infection. NR4A expression positively correlated with exhaustion markers (Tim-3 and PD-1) (p<0.05), as well as the severity of pulmonary lesions (lung index, fungal burden in the lungs), the occurrence of Cryptococcal brain infection, and the development of CD4+ T cell exhaustion. These suggest that CD4+ T lymphocyte exhaustion has been implicated in the development of disseminated cryptococcal Infection, and it is possibly associated with the transcription factor NR4A.