Overexpression of the MHV receptor. Effect on progeny virus secretion.

The intracellular interaction of the coronavirus mouse hepatitis virus (MHV) with its cellular receptor (MHVR) was investigated. Overexpression of MHVR from vaccinia vectors during an ongoing MHV infection resulted in dramatic inhibition of virus production. Infectivity in both cytoplasmic extracts and supernatants was reduced by over three orders of magnitude relative to control cultures in which a truncated MHVR lacking virus binding activity was expressed. Complete MHV virions were not detectable in supernatants of MHVR expressing cells. In the presence of overexpressed MHVR, the coronavirus spike protein was not cleaved into posttranslation products S1 and S2, nor was it fully processed into a form resistant to endoglycosidase H digestion, indicating that intracellular engagement of spike with receptor prevented spike transport and consequent association with virions.