Characterization of Nasal Mucosal T Cells in Horses and Their Response to Equine Herpesvirus Type 1.

Equine herpesvirus type 1 (EHV-1) enters through the upper respiratory tract (URT). Mucosal immunity at the URT is crucial in limiting viral infection and morbidity. Here, intranasal immune cells were collected from horses ( = 15) during an experimental EHV-1 infection. CD4 and CD8 T cells were the major intranasal cell populations before infection and increased significantly by day six and fourteen post-infection, respectively. Nasal mucosal T cells were further characterized in healthy horses. Compared to peripheral blood mononuclear cells (PBMC), mucosal CD8 T-cell percentages were elevated, while CD4 T-cell percentages were similar. A small population of CD4CD8 T cells was also recovered from mucosal samples. Within the URT tissue, CD4 cells predominantly accumulated in the epithelial layer, while most CD8 cells resided deeper in the mucosa or the submucosa below the basement membrane. In vitro stimulation of mucosal cells from healthy horses with ( = 5) or without ( = 5) peripheral T-cell immunity against EHV-1 induced IFN-γ production in nasal T cells upon polyclonal stimulation. However, after EHV-1 re-stimulation, mucosal T cells failed to respond with IFN-γ. This work provided the first characterization of mucosal T-cell phenotypes and functions in the URT of healthy horses and during EHV-1 infection.