title: Immunoglobulin Fc binding activity is associated with the mouse hepatitis virus E2 peplomer protein.
abstract: Antigenic variation among murine coronaviruses is associated primarily with the surface peplomer protein E2 (180,000 Da). E2 is responsible for attachment of the virus to the host cell, MHV-induced cell fusion, and eliciting neutralizing antibody. We report here the molecular mimicry between E2 and Fc gamma receptor (Fc gamma R). Molecular mimicry between E2 and Fc gamma R may allow the escape of virus-infected cells from destruction by immunological mechanisms. Rabbit IgG, monoclonal rat IgG1 and IgG2b, monoclonal mouse IgG2a and IgG2b, and the rat anti-mouse Fc gamma R monoclonal antibody 2.4G2 immunoprecipitated from MHV-JHM-infected cells a polypeptide with a molecular mass identical to that immunoprecipitated by anti-E2 antibodies. F(ab')2 fragments of rabbit IgG did not immunoprecipitate any proteins from MHV-infected cells. All of these antibodies did not immunoprecipitate any proteins from uninfected cells. The anti-mouse Fc gamma R monoclonal antibody 2.4G2 immunoprecipitated from MHV-JHM-, MHV-3-, or MHV-A59-infected L-2 cells and 17CL-1 cells, or MHV-JHM-infected cultures of neonatal BALB/c brain cells, a protein with a molecular weight identical to that of MHV-JHM E2. The anti-Fc gamma R monoclonal antibody did not immunoprecipitate any proteins from uninfected cells. Furthermore, the 2.4G2 monoclonal antibody (mab), unrelated rat and mouse monoclonal antibodies, and a goat antiserum against E2, but not normal goat serum, immunoprecipitated a 75,000- to 77,000-Da molecule from uninfected WEHI-3 cells, a Fc gamma R bearing cell line. Several lines of evidence demonstrated that the protein immunoprecipitated by the anti-Fc gamma R mab from MHV-JHM-infected cells is the E2 glycoprotein: (1) Partial proteolytic maps obtained by Staphylococcus aureus V-8 protease treatment of the 180,000-Da proteins immunoprecipitated by the anti Fc gamma R mab and the anti-E2 mab were identical. (2) Sequential immunoprecipitation experiments from MHV-JHM-infected cells revealed that the same polypeptide chain was recognized by the anti-E2 mab and by the anti-Fc gamma R mab 2.4G2, (3) Actinomycin D did not influence the induction and expression of the 180,000-Da polypeptide chain that was immunoprecipitated by the anti-Fc gamma R mab, demonstrating that this protein is of viral origin.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston 77030.
authors.forename: E L
authors.initials: EL
authors.lastname: Oleszak
authors.forename: J L
authors.initials: JL
authors.lastname: Leibowitz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D002460:Cell Line; D006023:Glycoproteins / Q000276:immunology / Q000648:ultrastructure*; D007141:Immunoglobulin Fc Fragments / Q000276:immunology*; D007074:Immunoglobulin G / Q000032:analysis; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000276:immunology* / Q000648:ultrastructure; D010449:Peptide Mapping; D011817:Rabbits; D012697:Serine Endopeptidases; D014764:Viral Proteins / Q000276:immunology / Q000648:ultrastructure*
chemical_list: D000911:Antibodies, Monoclonal; D006023:Glycoproteins; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D014764:Viral Proteins; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase