Histopathology and immunohistochemistry of renal lesions due to infectious bronchitis virus in chicks.

Two-day-old specific-pathogen-free chicks were inoculated intranasally with the MA-87 strain of infectious bronchitis virus, and trachea and kidney lesions studied histologically and immunohistochemically. Lesions and viral antigen were first detected in the trachea; severe damage was then observed in the kidney. Viral antigen appeared prior to the development of renal lesions and was detected in the cytoplasm of epithelial cells by 4 days post-inoculation (p.i.). The epithelial cells of the collecting ducts, collecting tubules and distal convoluted tubules were first affected, followed by involvement of Henle's loops, whereas the proximal convoluted tubules were only minimally affected. Antigen-positive cells of ducts and tubules were degenerated and desquamated. The severe epithelial cell damage resulted in infiltration of heterophils and macrophages in the interstitium, ducts and tubules. The detection of viral antigen was consistent with the distribution of histological lesions at 6 to 8 days p.i. At a later stage, antigen-positive cells disappeared and repair of epithelial cells was seen, accompanied by interstitial lymphoplasmacytic infiltration and lymphoid nodular formation.