Airborne Influenza PR8-A Virus Infections in Actively Immunized Mice

Abstract

Young adult white mice, immunized subcutaneously with formalized mouse-lung suspensions of influenza PR8-A virus (test mice), along with corresponding unimmunized (control) mice, were exposed to sublethal and highly lethal nebulized clouds of freshly harvested homologous virus. The control mice developed rapid and fatal pulmonary infections following exposure to the lethal cloud of virus and extensive and persisting pulmonary changes following exposure to sublethal clouds of virus. The test mice became only mildly ill and survived the lethal airborne infections, although the virus grew to high titer in the lungs. Pneumonic involvement was focal and confined to the bronchial air passages and adjacent alveoli. Resolution occurred and residual lung scarring was not seen in recovered mice. Circulating antibody, therefore, was highly effective not only in preventing death but residual lung pathology.