Localization of swine hepatitis E virus in liver and extrahepatic tissues from naturally infected pigs by in situ hybridization

Background/Aims: The objective of this study was to detect and localize the swine hepatitis E virus (HEV) in the liver and extrahepatic tissues from 20 pigs naturally infected with swine HEV. Methods: cDNA probe 289 base pairs for swine HEV were generated by reverse transcription–polymerase chain reaction. In situ hybridization with a nonradioactive digoxigenin-labeled cDNA probe was used for the detection of swine HEV in formalin-fixed, paraffin-embedded tissues. Results: When liver tissues from the pigs naturally infected with swine HEV were hybridized with the nonradioactive digoxigenin-labeled cDNA probe, a strong signal was seen in hepatocytes and bile duct. Positive hybridization signals were also detected in small and large intestine, lymph node, tonsil, spleen, and kidney. Conclusions: Swine HEV was detected primarily in the hepatocytes. Swine HEV may also replicate in tissues other than the liver. In situ hybridization described in the present study has greatly facilitated the application of in situ hybridization procedures to the clinical setting, thus allowing for the diagnosis of swine HEV infection while preserving the morphology of the tissue.