Persistent transmission of mouse hepatitis virus by transgenic mice

Variation in susceptibility to viral infection is well documented across mo use strains. Specific combinations of viral strains and murine hosts may fa vor viral infection and disease, and could potentially allow the unexpected development of chronic, persistent, or latent infections. In some genetica lly modified strains of mice, immune function and perhaps other physiologic or metabolic systems may be substantially or marginally impaired. In the c ase study reported here, we document the apparent persistent transmission o f mouse hepatitis virus (MHV) over a two-year period by MHV-seropositive tr ansgenic mice. Transmission occurred via direct contact with seropositive m ice and exposure to contaminated bedding. However, MHV was not detected at diagnostic laboratories by use of viral isolation or reverse transcriptase- polymerase chain reaction (RT-PCR) analysis of tissues from MHV-seropositiv e animals. Our observation, together with the constantly expanding varietie s of immune-impaired or poorly characterized murine hosts and the burgeonin g dissemination of these animals throughout the biomedical research communi ty, indicate that unexpected pathophysiologic presentations of common murin e viral diseases may present new challenges to the biomedical research comm unity in the future.