Tissue distribution of avian infectious bronchitis virus following in ovo inoculation of chicken embryos examined by in situ hybridization with antisense digoxigenin-labeled universal riboprobe.

Chicken embryos were inoculated with 8 different strains of infectious bronchitis virus (IBV) representing 7 different serotypes at 17 days of embryonation. At 2 and 5 days postinfection (dpi), tissues were collected for in situ hybridization using an antisense digoxigenin-labeled riboprobe corresponding to the se- quence of the mRNA coding for the membrane protein. Extensive antigen staining in the cytoplasm of epithelial cells in the trachea, lung, bursa, and intestine was detected at 2 dpi with all 8 strains of IBV. At 5 dpi, little or no positive staining was observed in these tissues. However, tubular cells of the kidney showed multifocal positive staining with the Wolgemuth strain-, Gray strain-, JMK strain-, and Mass41 strain-infected chickens. No viral RNA was detected in the spleen at any time point. The results demonstrated strict epitheliotropic nature and wide tissue tropism of strains of IBV in the chicken embryo and the universality of our riboprobe. In situ hybridization with this probe will be useful for understanding the tissue tropism and the pathogenesis of IBV in vivo. Infectious bronchitis (IB) is a worldwide disease of poultry caused by infectious bronchitis virus (IBV), a member of the genus coronavirus, in the new order Nidovirales. 5 Coronaviruses are a common cause of enteric infection, respiratory infection, or both in ani-