Anatomically Restricted Synergistic Antiviral Activities of Innate and Adaptive Immune Cells in the Skin

Despite extensive ex vivo investigation, the spatiotemporal organization of immune cells interacting with virus-infected cells in tissues remains uncertain. To address this, we used intravital multiphoton microscopy to visualize immune cell interactions with virus-infected cells following epicutaneous vaccinia virus (VV) infection of mice. VV infects keratinocytes in epidermal foci and numerous migratory dermal inflammatory monocytes that outlie the foci. We observed Ly6G+ innate immune cells infiltrating and controlling foci, while CD8+ T cells remained on the periphery killing infected monocytes. Most antigen-specific CD8+ T cells in the skin did not interact with virus-infected cells. Blocking the generation of reactive nitrogen species relocated CD8+ T cells into foci, modestly reducing viral titers. Depletion of Ly6G+ and CD8+ cells dramatically increased viral titers, consistent with their synergistic but spatially segregated viral clearance activities. These findings highlight previously unappreciated differences in the anatomic specialization of antiviral immune cell subsets. º Vaccinia virus infects keratinocytes in epidermal foci and monocytes that outlie foci º CD8+ T cells remain peripheral to foci and mainly kill infected monocytes º Ly6G+ innate immune cells infiltrate and control virus-infected cells within foci º CD8+ T cells and Ly6G+ innate immune cells synergize to control infection