Adenovirus endopeptidase hydrolyses human squamous cell carcinoma antigensin vitro but not ex vivo

The serpins SCCA1 and SCCA2 are highly expressed in the epithelium of the c onducting airways, a common site of infection by group C adenoviruses, such as human adenovirus type 2 (Ad2). Based on the common location we examined a possible interaction between them. in vitro experiments with recombinant proteins showed that SCCA1 inhibited the viral protease in a dose-dependen t manner. Both serpins were cleaved in a manner consistent with hydrolysis within their reactive site loop, without the formation of an SDS-resistant complex, as in the case of papain. Infection of SCCA1-expressing cells did not result in the cleavage of SCCA1, nor was the yield of infectious virus affected as compared to SCCA1-negative parental cells. This may be due to d ifferential localization, the serpin being cytoplasmic and viral protease b eing nuclear. Surprisingly, however, virus infection, which tends to inhibi t host protein synthesis, caused a significant increase in SCCA1 expression well into the late phase of infection. (C) 2000 Academic Press.