Induction of Viral Interference in Mice by Aerosols of Inactivated Influenza Virus.

Inactivated influenza viruses administered to mice intranasally or by aerosol induced transient heterologous immunity to infective influenza viruses. This immunity was reflected by reduction of pulmonary viral titers and by a reduced occurrence of gross lesions. This effect is considered to be an example of viral interference in that it required time to develop and persisted for at least 3 days; and because protective activity of inactivated viruses in mice could be correlated with interfering activity in the chick embryo. Interference modified but did not completely inhibit infection, and strain specific immunity of lessened degree developed to the challenge virus following the modified infection.