Induction of alpha interferon by transmissible gastroenteritis coronavirus: role of transmembrane glycoprotein E1

Epithelial cells infected with the coronavirus transmissible gastroenteritis virus (TGEV) and fixed by glutaraldehyde induced a high alpha interferon (IFN-alpha) production in nonimmune porcine as well as human or bovine peripheral blood mononuclear cells (PBMC). IFN-alpha was detected as early as 3 h after exposure of PBMC to infected cells and at producer/inducer cell ratios as low as 1/1. Two of four monoclonal antibodies directed against the viral transmembrane glycoprotein E1 could block the IFN-inducing capacity of both TGEV-infected cells and viral particles. On the other hand, IFN-alpha induction was not markedly affected by monoclonal antibodies directed against other E1 epitopes, against peplomer glycoprotein E2, or against nucleocapsid protein. Thus, these findings strongly imply that IFN induction by TGEV results from interactions between an outer membrane domain of E1 and the PBMC membrane.