Batf3-Dependent Dendritic Cells Promote Optimal CD8 T Cell Responses against Respiratory Poxvirus Infection

Respiratory infection with vaccinia virus (VacV) elicits robust CD8⁺ T cell responses that play an important role in host resistance. In the lung, VacV encounters multiple tissue-resident antigen-presenting cell (APC) populations, but which cell plays a dominant role in priming of virus-specific CD8⁺ effector T cell responses remains poorly defined. We used Batf3^-/- mice to investigate the impact of CD103⁺ and CD8α⁺ dendritic cell (DC) deficiency on anti-VacV CD8⁺ T cell responses. We found that Batf3^-/- mice were more susceptible to VacV infection, exhibiting profound weight loss, which correlated with impaired accumulation of gamma interferon (IFN-γ)-producing CD8⁺ T cells in the lungs. This was largely due to defective priming since early in the response, antigen-specific CD8⁺ T cells in the draining lymph nodes of Batf3^-/- mice expressed significantly reduced levels of Ki67, CD25, and T-bet. These results underscore a specific role for Batf3-dependent DCs in regulating priming and expansion of effector CD8⁺ T cells necessary for host resistance against acute respiratory VacV infection.IMPORTANCE During respiratory infection with vaccinia virus (VacV), a member of Poxviridae family, CD8⁺ T cells play important role in resolving the primary infection. Effector CD8⁺ T cells clear the virus by accumulating in the infected lungs in large numbers and secreting molecules such as IFN-γ that kill virally infected cells. However, precise cell types that regulate the generation of effector CD8⁺ T cells in the lungs are not well defined. Dendritic cells (DCs) are a heterogeneous population of immune cells that are recognized as key initiators and regulators of T-cell-mediated immunity. In this study, we reveal that a specific subset of DCs that are dependent on the transcription factor Batf3 for their development regulate the magnitude of CD8⁺ T cell effector responses in the lungs, thereby providing protection during pulmonary VacV infection.