Systemic murine cytomegalovirus infection of mice with retrovirus-induced immunodeficiency results in ocular infection but not retinitis.

Experiments were performed to explore the ability of murine cytomegalovirus (MCMV) to disseminate to the eye following intravenous inoculation and to cause infection of ocular tissues and necrotizing retinitis in C57BL/6 mice with retrovirus-induced immunodeficiency syndrome (MAIDS). Although infectious virus could be detected in whole eye homogenates of mice with MAIDS at 10 days after intravenous MCMV inoculation, a recombinant MCMV (RM461) that carries an MCMV IE1 promoter-LacZ insert was used as a tracer virus to confirm direct infection of ocular tissues. Evidence for MCMV replication (determined by RM461-induced expression of beta-galactosidase) was consistently observed in the nonpigmented epithelium of the ciliary body of the eyes of MAIDS animals at 14 days after infection. In sharp contrast, however, the neurosensory retina was spared and necrotizing retinitis failed to develop. These findings demonstrate that systemic MCMV infection of mice with MAIDS results in ocular MCMV infection without development of ocular MCMV disease. Conversion of occult subclinical MCMV infection of ocular tissues to overt clinical MCMV retinitis may require as yet unidentified cofactor(s). Identification of these cofactors could lead to more innovative therapeutic approaches for prevention and/or treatment of CMV retinitis in patients with AIDS.