Interaction of mouse hepatitis virus (MHV) spike glycoprotein with receptor glycoprotein MHVR is required for infection with an MHV strain that expresses the hemagglutinin-esterase glycoprotein

Abstract

In addition to the spike (S) glycoprotein that binds to carcinoembryonic antigen-related receptors on the host cell membrane, some strains of mouse coronavirus (mouse hepatitis virus [MHV]) express a hemagglutinin esterase (HE) glycoprotein with hemagglutinating and acetylesterase activity. Virions of strains that do not express HE, such as MHV-A59, can infect mouse fibroblasts in vitro, showing that the HE glycoprotein is not required for infection of these cells. The present work was done to study whether interaction of the HE glycoprotein with carbohydrate moieties could lead to virus entry and infection in the absence of interaction of the S glycoprotein with its receptor glycoprotein, MHVR. The DVIM strain of MHV expresses large amounts of HE glycoprotein, as shown by hemadsorption, acetylesterase activity, and immunoreactivity with antibodies directed against the HE glycoprotein of bovine coronavirus. A monoclonal anti-MHVR antibody, MAb-CC1, blocks binding of virus S glycoprotein to MHVR and blocks infection of MHV strains that do not express HE. MAb-CC1 also prevented MHV-DVIM infection of mouse DBT cells and primary mouse glial cell cultures. Although MDCK-I cells express O-acetylated sialic acid residues on their plasma membranes, these canine cells were resistant to infection with MHV-A59 and MHV-DVIM. Transfection of MDCK-I cells with MHVRcDNA made them susceptible to infection with MHV-A59 and MHV-DVIM. Thus, the HE glycoprotein of an MHV strain did not lead to infection of cultured murine neural cells or of nonmurine cells that express the carbohydrate ligand of the HE glycoprotein. Therefore, interaction of the spike glycoprotein of MHV with its carcinoembryonic antigen-related receptor glycoprotein is required for infectivity of MHV strains whether or not they express the HE glycoprotein.

The novel hemagglutinin-esterase genes of human torovirus and Breda virus

“…Although, receptor binding and membrane fusion in coronaviruses has been shown to be mediated by the S protein (Cavanagh, 1995), it has been suggested that the coronavirus HE may serve as an additional membrane-binding protein (Vlasak et al, 1988;Parker et al, 1989). However, it has been shown from studies on mouse hepatitis virus that infection cannot be mediated by HE alone as it requires the interaction of S with its receptor (Gagneten et al, 1995). Instead, it has been postulated that the HE protein may play a role in the early stages of infection where it mediates viral adherence to the intestinal wall of the host by specifically yet reversibly binding the mucopolysaccharides in the mucus layer that protects the epithelial cells of the enteric tract.…”

Molecular Interactions in the Assembly of Coronaviruses

“…While the HE proteins of BCoV, HEV, and HCoV-OC43 hydrolyze the 9-O-acetyl group of sialic acid and therefore appear to function as receptor-destroying enzymes (Schultze et al, 1991b;Vlasak et al, 1988a), the HE proteins of MHVlike coronaviruses function as sialate-4-O-acetylesterases (Klausegger et al, 1999;Regl et al, 1999;Wurzer et al, 2002). Although inhibition of the esterase activity of BCoV resulted in a 100-to 400-fold reduction in viral infectivity (Vlasak et al, 1988a), it was shown both for BCoV and for an MHV strain expressing an HE gene that the S protein is required and sufficient for infection (Gagneten et al, 1995;Popova and Zhang, 2002). In view of these results it has been proposed that the HE protein might play a role at an even earlier step and may mediate viral adherence to the intestinal wall through the specific yet reversible binding to mucopolysaccharides.…”

Sialic Acids in Molecular and Cellular Interactions

“…The S protein of MHV has been shown to bind to a specific protein related to carcinoembryonic antigen. This binding is required for a successful infection, whereas the HE protein, containing hemagglutinin and esterase activ-ity, is not necessary for virulence at least in tissue culture cells (Gagneten et al, 1995).…”