Reactivation of latent herpes simplex virus-1 (HSV) from mouse footpad cells demonstrated by in situ hybridization.

HSV-1 specific RNA sequences became detectable by in situ hybridization 5-6 days after culture of footpads (FP) explanted from latently infected mice. HSV-specific RNA first appeared in basal cells of hair follicles and cells of the hair root sheath, in epithelial cells of sebaceous glands and in cells within the epidermis. When first detected graining was light and usually present over individual cells, subsequently graining became heavy and present over large groups of cells. HSV reactivation from latency could be demonstrated in individual cells and therefore identified those cells in which the virus has been latent. The heavy graining over clumps of cells characteristic of a lytic infection was seen at later times after explantation; we infer that the infection had spread progressively from the initial foci of reactivation from latency.