Antigenic and biological diversity among transmissible gastroenteritis virus isolates of swine

Twenty-four field isolates of transmissible gastroenteritis virus (TGEV) were isolated and examined for antigenic and biological characteristics. Most TGEV isolates produced a typical cytopathic effect (CPE) in swine testis (ST) cell culture, which included a ballooning or lifting away of the infected cells from the cell monolayer with heavy granulation evident. Minor variations in CPE were observed with one isolate, IA-145. Protein profiles of the TGEV isolates as determined by SDS-PAGE were essentially identical, with the exception of the isolate IA-101. The TGEV isolate IA-101 presented a higher molecular mass M protein and lacked an N protein doublet that was present in all other TGEV isolates. The TGEV isolates were shown to be closely related antigenically by using hyperimmune sera in a virus neutralization (VN) test. Some antigenic diversity was detected by utilizing monoclonal antibodies (mAbs) in a VN test. Titers of the mAbs were highest with the homologous Miller TGEV, and one virus isolate, IA-156, was very poorly neutralized with the mAbs used in this study. Indirect immunofluorescence assay (IFA) results were similar to those obtained by the VN test. These studies show that some biologic and antigenic diversity exists among TGEV isolates.