MAIT cell-directed therapy ofMycobacterium tuberculosisinfection

Mucosal-associated invariant T (MAIT) cells are potential targets of vaccination and host-directed therapeutics for tuberculosis, but the role of MAIT cells duringMycobacterium tuberculosis(Mtb) infection in vivo is not well understood. Here we find that following Mtb infection MAIT cells mount minimal responses, and MAIT cell-deficient MR1(-/-)mice display normal survival. Preinfection expansion of MAIT cells through 5-OP-RU vaccination fails to protect against subsequent Mtb challenge. In fact, 5-OP-RU vaccination delays Mtb-specific CD4 T cell priming in lung-draining lymph nodes, and conversely MR1 deficiency or blockade accelerates T cell priming. The MAIT cell-mediated delay in T cell priming is partly dependent on TGF-beta. Surprisingly, 5-OP-RU treatment during chronic infection drives MAIT cell expansion and an IL-17A-dependent reduction in bacterial loads. Thus, during early infection MAIT cells directly contribute to the notoriously slow priming of CD4 T cells, but later during infection MAIT cell stimulation may be an effective host-directed therapy for tuberculosis.

Automated summary

The study found that MAIT cells mount minimal responses following Mtb infection, but MAIT cell expansion during chronic infection can reduce bacterial loads. The 5-OP-RU vaccination failed to protect against Mtb challenge, but MAIT cells play a role in delaying T cell priming.