Respiratory tract infection induced experimentally by Ornithobacterium rhinotracheale in quails: effects on heat shock proteins and apoptosis

Ornithobacterium rhinotracheale (ORT), a Gram-negative pathogen microorganism, causes respiratory tract diseases (RTD) in poultry. The objective of this experiment was to determine how RTD caused by ORT was associated with heat shock protein 70 (HSP-70) and apoptosis in quails. A total of 60 male quails, 10-week old, were equally divided into 2 groups: control (non-infected) and ORT (infected with 1 mL of a pure culture of ORT strain B3263/91, serotype A, 3.8 x10(8) CFU/mL by aerosol route). Then, 10 quails in both groups were sacrificed on days 10, 21, and 42 post-inoculation and organs (nasal sinuses, larynx, trachea, lungs and air sacs) were collected for bacteriological, serological and histopathological (conventional histology, HSP 70 immunohistochemistry and apoptotic index determined with the TUNEL method) evaluations. No ORT was isolated from the control and infected birds. However, 46.7% of infected birds were seropositive. The ORT infected birds exhibited inappetence and RTD symptoms, including nasal discharge and sneezing a week after inoculation. The protein HSP-70 showed immunoreactivity in epithelial cells of the secondary and tertiary bronchi and air vesicles of the lungs and the epithelium of the air sacs, trachea, larynx, and sinuses but significantly declined when histopathological lesions and the apoptotic index increased since the 10th day. On day 42, inflammatory lesions and apoptosis were maximal whereas the HSP-70 expression was markedly depressed in lungs, air sacs and in trachea. As a conclusion, HSP-70 production was inversely correlated with apoptotic cells in ORT infected quails.