IN-SITU HYBRIDIZATION TECHNIQUE FOR THE DETECTION OF SWINE ENTERIC AND RESPIRATORY CORONAVIRUSES, TRANSMISSIBLE GASTROENTERITIS VIRUS (TGEV) AND PORCINE RESPIRATORY CORONAVIRUS (PRCV), IN FORMALIN-FIXED PARAFFIN-EMBEDDED TISSUES

The in situ hybridization (ISH) technique was developed to detect the swine coronaviruses, transmissible gastroenteritis virus (TGEV) and po rcine respiratory coronavirus (PRCV), in cell culture and tissue secti ons from TGEV-or PRCV-infected pigs. The S-35-labeled RNA probes were generated from two plasmids pPSP.FP1 and pPSP.FP2 containing part of t he S gene of TGEV. The procedure was first standardized in cell cultur es. The radiolabeled pPSP.FP2 probe detected both TGEV and PRCV in vir us-inoculated cell cultures, whereas pPP.FP1 probe detected TGEV but n ot PRCV. The probe was then used to detect TGEV or PRCV in tissues of pigs experimentally infected with TGEV or PRCV or naturally infected w ith TGEV. Again, the probes detected TGEV in intestines of experimenta lly and naturally infected pigs and PRCV in the lungs of experimentall y infected pigs. TGEV RNA was detected mainly within the enterocytes a t the lips of villi and, less often, within some crypt epithelial cell s. PRCV was shown to replicate mainly in the bronchiolar epithelial ce lls and in lesser amount in type II pneumocytes, type I pneumocytes, a lveolar macrophages and bronchial epithelial cells, respectively. ISH has potential applications as a diagnostic test for the detection and differentiation of TGEV and PRCV in tissues and in studies to gain a b etter understanding of the mechanism of pathogenesis of enteric and re spiratory coronavirus infections.