Persistence of porcine Coronavirus, transmissible gastroenteritis virus, in swine testicle cells

Porcine transmissible gastroenteritis virus (TGEV) readily and reproducibly established persistent infection in swine testicle (ST) cells.Swine testicle cells persistently infected with TGEV resisted plaque formation by homologous virus and vesicular stomatitis virus infection, apparently by producing interferon.In most cultures in our study, approximately 10 4-6 plaque forming units of TGEV per milliliter were produced throughout the five year culture period.One cell line, 2B-S2, produced virus only intermittently.In most persistently infected cultures, 20-30% of the cells were positive for viral antigens by fluorescence.No temperature sensitive virus was produced.The persistent infection could not be cured by neutralizing polyclonal antibody or by cloning.Interference with plaque formation on naive ST cells by homologous TGEV Miller strain was demonstrated.Defective interfering virus was a possible explanation.Transmissible gastroenteritis virus proteins were found in quantities comparable to those seen in acutely infected ST cells.With the exception of the membrane (M) protein, which appeared to form multimers the proteins migrated normally during denaturing polyacrylamide gel electrophoresis.Persistently infected ST cells produced few TGEV specific RNA containing nucleocapsid (N) gene sequences.Anti-sense RNAs containing the nucleocapsid gene region were not found in persistently infected cells, although they could be detected in acutely infected cells, The subgenomic message that codes for N protein was the predominant TGEV specific RNA in persistently infected ST cells.E. Cutler, Dr. J. M.