ATTACHMENT GLYCOPROTEINS AND RECEPTOR SPECIFICITY OF RAT CORONAVIRUSES

Murine coronavirus (MHV) and rat coronavirus (RCV) are antigenically r elated viruses that have different natural rodent hosts. Both MHV and RCV can be propagated in the La(Percy) and CMT-93 mouse cell Lines, In these cell lines MHV uses the MHV receptor (MHVR or Bgp1(a)) and seve ral related murine Bgp glycoproteins in the immunoglobulin superfamily as receptors. To determine whether RCV also uses these murine glycopr oteins as receptors, we characterized the envelope glycoproteins of tw o strains of RCV and compared the effects of anti-MHVR monoclonal anti body on susceptibility of the mouse cells to MHV and RCV, The Parker ( RCV-P) and sialodacryoadenitis (RCV-SDAV) strains of RCV expressed the spike glycoprotein S, but only RCV-P expressed a hemagglutinin-estera se glycoprotein that had acetylesterase activity. Therefore RCV-SDAV m ust bind to cellular receptors by the viral S glycoprotein, whereas RC V-P might bind to cells by its hemagglutinin-esterase glycoprotein as well as by S. Pretreatment of L2(Percy) 41.a or CMT-93 cells with anti -MHVR monoclonal antibody blocked infection with MHV-A59 but did not p revent infection of these murine cells with RCV-P or RCV-SDAV. Baby ha mster kidney cells transfected with cDNAs encoding MHVR (Bgp1(a)) or B gp2 were susceptible to MHV-A59 but not to RCV-P or RCV-SDAV, Thus the RCV strains cannot use these murine coronavirus receptors and must be infecting murine cells by another, as yet unknown, receptor.