Modulation of Roquin Function in Myeloid Cells Reduces Mycobacterium tuberculosis-Induced Inflammation

Damaging inflammation is a hallmark of Mycobacterium tuberculosis infection, and understanding how this is regulated is important for the development of new therapies to limit excessive inflammation. The E3 ubiquitin ligase, Roquin, is involved in immune regulation; however, its role in immunity to M. tuberculosis is unknown. To address this, we infected mice with a point mutation in Roquin1/Rc3h1 (sanroque). Aerosol-infected sanroque mice showed enhanced control of M. tuberculosis infection associated with delayed bacterial dissemination and upregulated TNF production in the lungs after 2 wk. However, this early control of infection was not maintained, and by 8 wk postinfection sanroque mice demonstrated an increased bacterial burden and dysregulated inflammation in the lungs. As the inflammation in the lungs of the sanroque mice could have been influenced by emerging autoimmune conditions that are characteristic of the mice aging, the function of Roquin was examined in immune cell subsets in the absence of autoimmune complications. M. bovis bacillus Calmette-Guérin-primed sanroque T cells transferred into Rag1^-/- mice provided equivalent protection in the spleen and liver. Interestingly, the transfer of mycobacteria-specific (P25 CD4⁺ TCR transgenic) wild-type spleen cells into sanroqueRag1^-/- mice actually led to enhanced protection with reduced bacterial load, decreased chemokine expression, and reduced inflammation in the lungs compared with transfers into Rag1^-/- mice expressing intact Roquin. These studies suggest that modulation of Roquin in myeloid cells may reduce both inflammation and bacterial growth during the chronic phase of M. tuberculosis infection.