RECONSTITUTED CORONAVIRUS TGEV VIROSOMES LOSE THE VIRUS ABILITY TO INDUCE PORCINE INTERFERON-ALPHA PRODUCTION

The transmissible gastroenteritis virus (TGEV) is a coronavirus which induces a strong interferon-alpha (IFN-alpha) production in vivo and i n vitro. Previous studies have shown that the TGEV external protein M plays a major role in IFN-alpha induction by a non-infectious virus, w hereas protein S is not involved. The present study extended these res ults by showing that monoclonal antibodies (MAbs) directed at the exte rnal viral protein sM could not block IFN-alpha induction, which argue s against a direct role for this protein. In the same type of blocking experiment, MAbs to the TGEV receptor aminopeptidase N did not inhibi t IFN-alpha induction, which strongly indicates that viral replication or entry through the receptor is not needed for TGEV induction of IFN -alpha in leukocytes. In an attempt to isolate functional envelope pro teins, TGEV virions were detergent-solubilized and reconstituted in vi rosomes. Although BIAcore antigenic analysis revealed that the three e xternal viral proteins were present on the virosomes, these proteins w ere unable to induce IFN-alpha in porcine leukocytes, and seemed to co mpete with the native virus for IFN-alpha induction. These data indica ted that IFN-alpha inducing interactions between TGEV external protein s and leukocytes required a complex native envelope protein structure which has been lost in the virosomes.