Respiratory infection in mice with sialodacryoadenitis virus, a coronavirus of rats

Sialodacryoadenitis virus (SDAV), a coronavirus of rats, evoked both serum neutralization and complement fixation antibody responses when inoculated intranasally in mice. Weanling gnotobiotic CD-1 mice inoculated intranasally with 10(3.0) mean tissue culture infective doses of SDAV remained asymptomatic. Virus was recovered from the nasopharynx, trachea, and lung from day 2 to day 7. Viral antigen was readily detected by indirect immunofluorescence in the lung but rarely in the nasopharynx. Infected mice developed interstitial pneumonia. Susceptible mice contact exposed to experimentally infected mice developed antibody to SDAV. Epizootiological studies indicated that retired breeder mice can have complement-fixing antibody to SDAV and mouse hepatitis virus (MHV) in the absence of MHV infection. These studies show that SDAV is infectious for mice and can be a pathogen for the respiratory system. Thus, SDAV infection of mice may be responsible for spurious seroconversions to MHV.