Transforming growth factor-beta expression induced by rhinovirus infection in respiratory epithelial cells

Rhinovirus infection of the lower airways is now a recognized disease, associated with bronchiolitis and asthma. The bronchial epithelial cells are the host cells when rhinovirus infection occurs in the airway. It was hypothesized that a pro-fibrotic growth factor response may occur in these infected cells, leading to production of a key transforming growth factor, TGF-beta-1. Bronchial epithelial cells were inoculated with human rhinovirus and compared at day 1, 3 and 5 to control non-infected cells. Cell culture supernatant fluid and cellular RNA were isolated. The amount of released TGF-beta protein was measured by enzyme-linked immunosorbent assay (ELISA). Expression of TGF-beta at the level of transcription was measured by polymerase chain reaction (PCR) and gel electrophoresis. The results show that at all time points studied, TGF-beta production is greater in the infected cells, as demonstrated by ELISA (P<0.05) and by semi-quantitative PCR analysis. It was concluded that bronchial epithelial cells infected with common cold virus and rhinovirus, showed higher levels of TGF-beta. The production of TGF-beta may be indicative of a normal repair mechanism to counter inflammation, or in the setting of persistent asthma, could potentially lead to increased fibrosis and collagen deposition.