Sendai viral pneumonia in aged BALB/c mice

Sendai virus (SV) infection in aged BALB/c mice was evaluated as a natural model for age-associated susceptibility to viral pneumonia. Young (2 month-old) and aged (22-24 month-old) BALB/c mice were inoculated intranasally with 100 median pneumonia doses (PD50) of SV and examined at 6, 10, and 20 days by virus titration, immunohistochemistry, histopathology, and serology. The aged mice had significantly higher virus titers in lung, prolonged infection, delayed development, and resolution of pneumonia and significantly lower serum antibody titers. In a second experiment, the responses of young mice were compared to intermediate-aged mice (11-13 and 17-18 months old). The intermediate-aged mice had some characteristics of young mice and others of aged mice. The results indicate that SV infection can be used to study aging-associated susceptibility to a pneumotropic virus in a natural host, and that susceptibility of mice to viral pneumonia increases gradually during aging.