In situ characterization of human cytomegalovirus infection of bronchiolar cells in human transplanted lung.

Distal airway cell infection by human cytomegalovirus (HCMV) in transplanted lung has been occasionally reported but not systematically investigated. The present study aimed at testing the prevalence of HCMV bronchiolar infection in human transplanted lung. We identified and immunophenotyped, with double labeling, infected lung cells in 31 transbronchial biopsies with HCMV infection, containing distal airways (7 HCMV pneumonias, 7 HCMV infection without inflammation, and 17 morphologically occult, non-cytopathic HCMV infection). HCMV-infected cells in pneumonias, localizations, and occult infections were alveolar epithelia (32.8%, 42.8%, and 53.5%, respectively), endothelia (22.9%, 24.7%, and 26.4%, respectively), macrophages (0.006%, none, and none, respectively), airway epithelia (0.01%, 8.9%, and none, respectively), and bronchiolar smooth muscle cells (0.011%, 14.6%, and 16.1%, respectively). Ciliated and bronchiolar smooth muscle cells in transplanted lung only occasionally harbored viral infection and never showed viral cytopathy. On the basis of our morphological observations, HCMV infection of bronchiolar wall cells is rare, while alveolar epithelia and capillary endothelial cells are the major targets of lung infection.