In vivo imaging of ocular MCMV infection

To develop a technique by which murine cytomegalovirus (MCMV) infection can be confirmed and monitored in vivo in various ocular compartments and to investigate the dynamics and time course of primary ocular CMV infection.

The ability of recombinant MCMV-expressing enhanced green fluorescent protein (eGFP) to serve as a tool to monitor the in vivo dynamics of experimental intraocular CMV infection was examined. Immunocompetent BALB/c mice were infected subretinally with eGFP-MCMV. Confocal scanning laser ophthalmoscopy (SLO) was used to visualize viral spread in vivo on sequential days after infection. Eyes were processed for histology and immunofluorescence microscopy to confirm viral infection and replication by means of GFP signal.

Retina was readily permissive to primary infection with eGFP-mCMV, and fluorescent signal was detected by SLO 24 hours after subretinal injection, with scattered foci around the posterior pole of the retina. GFP levels in the retina reached a maximum on day 6. Signal in the iris developed from day 4 and lasted until day 25. Examinations of retinal and iris tissue wholemounts by immunofluorescence revealed signal localized to the outer retina, iris stroma, and anterior lens capsule.

The ability to noninvasively monitor infectious agents in the eye may improve current knowledge of the course and pathogenesis of intraocular infections and could lead to further clarification of the mechanisms by which the immune system responds to intraocular pathogens.