Apoptosis in experimentally infected chicks with avian infectious bronchitis

This experiment was performed to investigate apoptosis during undergoing pathogenesis of avian infectious bronchitis virus(IBV)-infected chicks. Sixteen days old chicks were infected with IBV, Massachusetts-41 strain(M-41, 10$^4$-10$^{5}$ EID$^{50}$ ) experimentally, they were autopsied to remove trachea, lung, kidney and cloacal bursa at 6hr, 12hr, 1 day, 3 day and 7 day post infection(PI) respectively for H-E and TUNEL staining. Grossly, mild serous, catarrhal exudate was observed in the trachea, nasal passages and sinuses nasal from 4 day PI. The cloacal bursa was swollen from 3 day PI. Histopathologically, the trachea was seen mild cellular infiltration, edema of the mucosa and submucosa, vascular congestion and mild hyperplasia of the epithelium from 6 hr PI and the changes were seen a little more severely on 7 day PI. It was observed that the cloacal bursa was getting more and more hyperplasia through the experiment. The nuclei degeneration were shown in the kidney on 7 day PI. No specific changes were seen in the lung. In TUNEL analysis, apoptotic cells showed sharp increasing at 12 hr PI and reaching a maximum on 1 day PI in the trachea, lung, kidney and cloacal bursa. And then apoptotic cells decreased gradually returning to a level of the control by 7 day PI in all the removed organs.