USE OF POLYMERASE-CHAIN-REACTION AND IMMUNOHISTOCHEMISTRY FOR DETECTION OF CANINE ADENOVIRUS TYPE-1 IN FORMALIN-FIXED, PARAFFIN-EMBEDDED LIVER OF DOGS WITH CHRONIC HEPATITIS OR CIRRHOSIS

To assess the possible involvement of canine adenovirus type 1 (CAV-1) in naturally occurring cases of canine chronic liver disease, a polym erase chain reaction (PCR)-based assay was developed to detect a conse rved region of the major core protein gene (pVII) of CAV-1 in formalin -fixed, paraffin-embedded liver sections. Results were compared with a standard avidin-biotin immunoperoxidase complex technique that detect ed CAV-1 antigens using a commercial monoclonal anti-adenovirus antibo dy. Seventeen cases of cirrhosis and 28 cases of chronic hepatitis wit h piecemeal necrosis and progressive fibrosis were selected for the st udy. Formalin-fixed, paraffin-embedded liver sections of 2 cases of in fectious canine hepatitis (ICH) and crude DNA extract from CAV-1 (ATCC VR 293 Utrecht strain) served as positive controls. A 411-base-pair v iral region was amplified and sequenced as CAV-1 pVII in both cases of infectious canine hepatitis and in the CAV-1 crude DNA extract. The 2 ICH cases were positive for CAV-1 antigens by the immunoperoxidase me thod. CAV-1 DNA or antigens were not detected by either technique in a ny of the 45 cases of chronic liver disease selected for the study. Th ese results indicate that both PCR and immunohistochemistry are reliab le and rapid techniques for detecting CAV-1 in formalin-fixed, paraffi n-embedded liver sections of dogs with ICH. Several possibilities may explain the negative results obtained with both techniques in this stu dy, including the noninvolvement of CAV-1 in canine chronic hepatitis and cirrhosis and the possibility that the virus causes initial damage , provokes a self-perpetuating chronic liver disease, and disappears.