SENDAI VIRUS-INFECTION CHANGES THE SUBCELLULAR-LOCALIZATION OF TRYPTASE CLARA IN RAT BRONCHIOLAR EPITHELIAL-CELLS

Tryptase Clara activates the infectivity of Sendai and influenza virus es proteolytically. In this study, we investigated changes in the subc ellular localization of tryptase Clara in rat bronchioles with progres sion of Sendai virus infection. Tryptase Clara and Sendai virus F2 ant igen were localized by light and electron immunohistochemical studies. In the uninfected rat lung, tryptase Clara was specifically localized in the secretory granules of respiratory bronchiolar epithelial nonci liated cells, but not in bronchiolar ciliated, or alveolar cells. In t he initial stage of Sendai virus infection with slight pathological ch anges, however, anti-tryptase Clara was highly reactive in luminal per ipheral membranes of both nonciliated and ciliated epithelial cells of the bronchioles together with some Sendai virus envelope glycoprotein , F2 antigen. In the progressed stage, tryptase Clara was hard to dete ct, with heavy accumulation of F2 antigen in the epithelial cells. The se immunohistochemical results support our previous findings that in t he bronchial lavage fluid tryptase Clara is significantly increased bo th in amount and activity after viral infection. These results suggest that Sendai virus stimulates the secretion of tryptase Clara from non ciliated bronchiolar epithelial cells to the airway lumen. Accumulatio n of tryptase Clara on the luminal surface of the bronchiolar epitheli al cells and/or in the airway lumen may produce favourable conditions for proteolytic viral activation and multiplication.