Progression of cytomegalovirus in the rabbit following the intraocular injection of the virus.

There is growing recognition that cytomegalovirus (CMV) is one of the opportunistic infections in patients afflicted with AIDS. The purpose of the present study was to establish a chronic CMV infection of the central nervous system (CNS) in rabbits after intraocular inoculation, to evaluate the therapeutic value of the model for investigation of the effect of antiviral drugs. It was possible to establish a chronic human cytomegalovirus (HCMV) encephalitis after 14-day old rabbits were injected into the vitreous body of the eye with the HCMV. One control and two experimental rabbits were killed at 16 days and 1, 3, 6 and 9 months post-inoculation. HCMV was demonstrated from the retina, optic nerve and brain by electron microscopy. HCMV infection did not cause apparent clinical symptoms or signs in the injected animals. At the morphological level the virus-induced lesion revealed the following features: that the HCMV travels slowly along the optic nerve and crosses at the optic chiasma showing a few thickly myelinated and many demyelinated axons with astroglial scar tissue. There was no evidence of inflammatory response in the lesions as no lymphocytes, plasma cells or phagocytic cells with dead myelin or lipid contents were observed. Long term observations of HCMV inoculated rabbits showed that the intraocular lesions followed a defined anatomical pathway in the optic nerve, chiasma and brain, leading to progressive chronic disease. The rabbit model would be very suitable for the evaluation of the therapeutic value of the effect of antiviral drugs.