Targets of herpes simplex virus type 1 infection in a mouse corneal model.

In animal models, spread of herpes simplex virus type 1 (HSV-1) from epithelial replication sites to the peripheral and central nervous system is known from analysis of individually dissected tissues. To examine virus spread in undissociated tissues, corneas of adult mice were inoculated with HSV-1. After 1 to 13 days groups of mice were perfused with formalin, and decalcified blocks of head and neck were embedded in paraffin. At intervals, serial sections were screened for HSV antigen. On days 1 and 2, viral antigen was restricted to cornea and conjunctiva but by days 3 and 4 was also seen in autonomic ganglia and the trigeminal system. On day 6, HSV antigen reached its maximum extent; infected sites included the trigeminal complex (ganglion, root, peripheral ophthalmic and maxillary branches and spinal nucleus and tract), ethmoid sinus and olfactory bulb, visual system, and autonomic ganglia (ciliary, pterygopalatine and superior cervical). Antigen progressively diminished on days 8 and 10, and was not detected on day 13. This method demonstrates a broader range of infected tissues and suggests a more complex pattern of HSV spread than has been previously recognized. Virus appears to reach the intracranial compartment by four different neural routes. When effects of higher and lower corneal inoculation doses were compared, a lower dose resulted in lower peak HSV titers in trigeminal ganglion and brain stem and later virus appearance in these tissues. Thus, dose may influence the kinetics of HSV spread from the peripheral inoculation site to the CNS.