The Pathogenesis and Pathology of Experimental Air-Borne Influenza Virus A Infections in Mice

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Abstract
The pathogenesis and pathology of exptl. air-borne Influenza A infection in mice were studied from its earliest inception through recovery. The mice were infected by exposing them in chambers to lethal concns. of nebulized influenza, PR 8 strain, virus. This technic of inoculation has the advantage of preventing nonspecific respiratory tract changes which may result from the anesthetic and the introduction of the virus in a fluid menstruum. The pathogenesis and pathology of exptl. air-borne influenza infections in mice is a dynamic one and is best studied in relation to the age of the lesions. The pathological changes are similar to those descr. by others employing mice as the exptl. animal. There was evidence in this study that the bronchial epithelial cells are not completely destroyed by the virus. After invasion by the virus, these cells shed that portion of the cytoplasm in which the virus grows, leaving only the nucleus surrounded by a small amt. of cytoplasm. These surviving cells then undergo marked proliferation, obstruct the terminal bronchioles, and grow peripherally into the collapsed alveolar ducts and alveoli. As they do so, metaplastic changes giving rise to stratified squamous epithelium occur. This membrane eventually degenerates, leaving cystic spaces lined by low cuboidal epithelial cells. Such spaces have no structural resemblance to alveolar ducts and alveoli but may persist in the lungs as non-respiratory functioning areas for the life of the animals.