Comparison of intranasal and aerosol infection of mice in assessment of immunity to influenza virus infection

Abstract

A comparison was made of intranasal and aerosol routes of infection with X-31 influenza A virus in Balb/c mice. Mice were first infected with 100 MID50 by either route then challenged 42 days later with the same virus given by the same or alternative route. Three days following each infection, pulmonary virus was measured by inoculation of chick embryos. Mice initially infected under ether anesthesia by intranasal inoculation experienced higher initial mortality but proved most resistant to subsequent challenge by either method. In contrast, mice first infected by aerosol were least resistant to intranasal challenge, as indicated by increased rate of infection and pulmonary virus titers, but, like mice previously infected intranasally, were not reinfected by the aerosol route. Thus, intranasal infection appears to be more effective both in inducing and challenging immunity from infection. These results should be considered in the design of experiments utilizing influenza virus infection of mice as a model system.