BCG vaccination drives accumulation and effector function of innate lymphoid cells in murine lungs

Abstract The tuberculosis ( TB ) vaccine bacille Calmette–Guérin ( BCG ) prevents disseminated childhood TB ; however, it fails to protect against the more prevalent pulmonary TB . Limited understanding of the immune response to Mycobacterium tuberculosis, the causative agent of TB , has hindered development of improved vaccines. Although memory CD 4 T cells are considered the main mediators of protection against TB , recent studies suggest there are other key subsets that contribute to antimycobacterial immunity. To that end, innate cells may be involved in the protective response. In this study, we investigated the primary response of innate lymphoid cells ( ILC s) to BCG exposure. Using a murine model, we showed that ILC s increased in number in the lungs and lymph nodes in response to BCG vaccination. Additionally, there was significant production of the antimycobacterial cytokine IFN ‐γ by ILC s. As ILC s are located at mucosal sites, it was investigated whether mucosal vaccination (intranasal) stimulated an enhanced response compared to the traditional vaccination approach (intradermal or subcutaneous). Indeed, in response to intranasal vaccination, the number of ILC s, and IFN ‐γ production in NK cells and ILC 1s in the lungs and lymph nodes, were higher than that provoked through intradermal or subcutaneous vaccination. This work provides the first evidence that BCG vaccination activates ILC s, paving the way for future research to elucidate the protective potential of ILC s against mycobacterial infection. Additionally, the finding that lung ILC s respond rigorously to mucosal vaccination may have implications for the delivery of novel TB vaccines.