NR4A1 Limits CD8+ T-Cell Effector Responses and Protection in Tuberculosis

Keywords

NR4A1

NKG7

CD8+ T Effector Cells

Mycobacterium tuberculosis

Granuloma

Main Findings

Mycobacterium tuberculosis (Mtb) remains the leading cause of death from a single infectious agent, with more than 10 million new cases estimated in 2024. While most individuals contain Mtb within pulmonary granulomas (latent tuberculosis), immune stressors (e.g., physiological stress, immunosuppression, or aging) can precipitate progression to active disease, increasing infectiousness and the risk of transmission.

The emergence of multidrug-resistant Mtb underscores the need for new therapeutic strategies. Host-directed therapies have gained prominence, largely emphasizing alveolar macrophages—the primary cellular niche for Mtb replication—yet other immune populations, including CD8+effector T cells, also contribute to protective immunity.

In this preprint (not peer reviewed), Fatima et al. evaluate the impact of NR4A1 inhibition in CD8+ T cells during active tuberculosis in a murine model. Their findings expand our understanding of NR4A1-dependent transcriptional regulation, including suppression of NKG7 expression. Upon immune synapse formation, NKG7 facilitates the fusion of cytotoxic granules with the plasma membrane. Notably, genetic ablation or pharmacologic inhibition of NR4A1 inhibition improved Mtb control and reduced disease burden, supporting NR4A1 as a potential host-directed therapeutic target.

More specifically, the authors report prolonged survival in Nr4a1knockout mice following challenge with the Mtb Erdman strain. Knockout animals exhibited reduced granuloma burden in the lung and spleen and, consistent with this, lower bacterial loads as measured by colony-forming units (CFUs) from tissue homogenates. Relative to wild-type controls, Nr4a1-/-CD8+ T cells displayed a distinct transcriptional profile enriched for cytokine-mediated signaling and leukocyte migration pathways.

Single-cell RNA sequencing of Nr4a1-/-mice indicated an increased frequency of cytotoxic T-cell subsets. In both infected and uninfected conditions, Nr4a1-/- CD8+T cells expressed higher levels of Gzma and Nkg7. ChIP-qPCR further supported direct NR4A1 binding at the Nkg7 promoter, suggesting a previously underappreciated regulatory mechanism.

Pharmacologic NR4A1 inhibition using the small molecule DIM-C in Mtb-infected wild-type mice reduced lesion formation, as assessed by histopathology and CFU quantification. DIM-C treatment was also associated with altered intragranulomatous localization of CD8+ T cells and increased cytolytic potential, consistent with NKG7 upregulation.

Limitations

The study provides a detailed assessment of NR4A1 function in CD8+ T cells during tuberculosis. The following additional experiments could further strengthen the conclusions and translational relevance.

The reliance on C57BL/6 mice is understandable given the availability of immunologic tools and knockout strains. However, inclusion of C3H mice—whose granulomatous pathology more closely reflects human disease (e.g., increased hypoxia and necrosis)—could strengthen the case for clinical translation, particularly for the DIM-C intervention studies.

It would also be informative to quantify and phenotype CD8+T-cell populations in the hilar or mediastinal lymph nodes, analyzed separately from lung homogenates. Incorporating Mtb-specific tetramers could further clarify antigen specificity and trafficking dynamics.

Because Nr4a1 is an immediate-early gene induced upon T-cell activation and can influence immunometabolic reprogramming downstream of TCR stimulation, metabolic profiling (e.g., Seahorse assays) comparing activated wild-type and Nr4a1-/- CD8+ T cells would provide additional mechanistic support and inform expectations regarding durability of effector function.

Knockout of Nr4a1, performed under a CD8+ T cell specific promoter, would also help reinforce the overall knockout and adoptive T cell transfer findings. Conversely, overexpression of Nr4a1 also specifically assessed in CD8+ T cells, would be a nice comparison to the wildtype control groups.

Finally, although beyond the primary scope of the study, assessing the impact of Nr4a1 inhibition in additional immune compartments (e.g., dendritic cells) could clarify whether altered antigen presentation contributes to the observed CD8+ T-cell phenotypes. Evaluating cross-presentation capacity and costimulatory molecule expression (CD80/CD86) would be particularly informative.

Significance/Novelty

Overall, this study highlights a role for NR4A1 in constraining effector CD8+ T-cell positioning within Mtb granulomas and limiting cytotoxic potential. The authors link NR4A1 to NKG7 regulation through ChIP-qPCR evidence of NR4A1 binding at the Nkg7 promoter, consistent with transcriptional repression. In addition, pharmacologic NR4A1 inhibition using the repurposed small molecule DIM-C improved granuloma-associated CD8+ T-cell infiltration and reduced disease burden in preclinical models, supporting the potential of NR4A1-targeted host-directed therapy for active tuberculosis.

Scientific Quality: 4 stars

Novelty: 5 stars

Significance: 5 stars

Credit

Reviewed by Guillaume Trusz as part of a cross-institutional journal club between the University of Oxford, the Karolinska Institute, the Icahn School of Medicine at Mount Sinai, the University of Toronto, and the UT MD Anderson Cancer Center James P Allison Institute.

The author declares no conflict of interests in relation to their involvement in the review.