In vivo imaging assay for the convenient evaluation of antiviral compounds against cytomegalovirus in mice

Evaluation of newly identified antiviral compounds against cytomegalovirus (CMV) in vivo still requires laborious and time-consuming experiments using a large number of animals. In this study, we examined an in vivo imaging assay for the evaluation of antiviral compounds using a recombinant murine CMV expressing EGFP (MCMV-GFP). We found the followings: (1) Fluorescent signals were detectable from 1 day after subcutaneous inoculation of the viruses into the backs of mice, and reached to the peak within 2–4 days. (2) Incubation period required for the signal appearance and peak signal intensities depended on the inoculated dose. (3) Not only BALB/c but also a hairless mouse strain, HR1, can be used for the assay, and no need to shave the HR1 mice added to the convenience of the assay. (4) However, BALB/c mice showed better sensitivity and dose–response to the inoculated virus, and inoculation with 200 PFUs of MCMV-GFP still yielded the signals. (5) Demonstration of the antiviral effect of ganciclovir provided a proof-of-concept. Thus, the in vivo imaging assay can allow the fast and convenient initial evaluation of anti-CMV candidate compounds in animals prior to comprehensive analyses.