Progressive Descending Influenza Infection in Mice Determined by Immunofluorescence

Abstract

Summary

A specific immunofluorescent (IF) technique was developed for swine influenza virus using fluorescein conjugated immune globulins. IF technique was employed to study the progressive pathogenesis of S-15 virus in mice. IF was detected in bronchial epithelium 8 hours after inoculation. Fluorescence, at this stage, was mostly cytoplasmic, however both cytoplasmic and nuclear fluorescence occurred in a few cells. IF reached a peak on the second and third day in the bronchi and usually spread to alveoli by the second day post inoculation. After the fourth day post inoculation, IF diminished in the alveoli and bronchi and disappeared after the 7th day. IF indicated that both cytoplasm and nuclei of infected cells are involved in the synthesis of viral antigens. IF was limited to macrophages and epithelial cells of bronchi, alveoli, and turbinates. It was concluded that influenza virus progressively infects bronchi, bronchioles, alveolar ducts, and alveoli during the course of infection.