CD8A and viral infectious disease: For example, only 30–40% of CD8 bTRM become CD103+ during persistent MuPyV infection, but close to 90% of CD8 T cells will express CD103 following brain infection with VSV, an acutely resolving infection, which suggested that the chronicity of the viral infection may affect the frequency of CD8 CD103+ bTRM [53,55,60].