Morphological, histochemical and histoenzymatic investigations on the lungs of mice chronically infected with influenza virus type A.

The lungs of mice having survived three inoculations with influenza virus A/PR8/34 (H1N1) repeated at 7-day intervals (an experimentally induced "chronic" influenza infection) were subjected to histological, electron optic, histochemical and histoenzymatic investigations. Hyperemia, edema and infiltration of the alveolar walls with lymphoid and monocytic elements could be observed. Electron microscopy revealed changes at the level of different ultrastructures of both lung and infiltration cells. A decrease in the levels of alkaline phosphatase, lactate, malate, succinate dehydrogenases and monoaminoxidase, an elevated amount of lipids and of mucopolysaccharides were made evident in the lung cells of mice chronically infected with influenza virus type A.