Oleszak E L, Leibowitz J L
Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston 77030.
Virology. 1990 May;176(1):70-80. doi: 10.1016/0042-6822(90)90231-f.
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.
鼠冠状病毒之间的抗原变异主要与表面纤突蛋白E2（180,000道尔顿）有关。E2负责病毒与宿主细胞的附着、MHV诱导的细胞融合以及引发中和抗体。我们在此报告E2与Fcγ受体（FcγR）之间的分子模拟。E2与FcγR之间的分子模拟可能使病毒感染的细胞通过免疫机制逃避破坏。兔IgG、大鼠单克隆IgG1和IgG2b、小鼠单克隆IgG2a和IgG2b以及大鼠抗小鼠FcγR单克隆抗体2.4G2从感染MHV-JHM的细胞中免疫沉淀出一种分子量与抗E2抗体免疫沉淀出的多肽相同的多肽。兔IgG的F(ab')2片段未从感染MHV的细胞中免疫沉淀出任何蛋白质。所有这些抗体均未从未感染的细胞中免疫沉淀出任何蛋白质。抗小鼠FcγR单克隆抗体2.4G2从感染MHV-JHM、MHV-3或MHV-A59的L-2细胞和17CL-1细胞，或感染MHV-JHM的新生BALB/c脑细胞培养物中免疫沉淀出一种分子量与MHV-JHM E2相同的蛋白质。抗FcγR单克隆抗体从未感染的细胞中免疫沉淀出任何蛋白质。此外，2.4G2单克隆抗体（mab）、无关的大鼠和小鼠单克隆抗体以及抗E2的山羊抗血清，但不是正常山羊血清，从未感染的WEHI-3细胞（一种携带FcγR的细胞系）中免疫沉淀出一种75,000至77,000道尔顿的分子。几条证据表明，抗FcγR mab从感染MHV-JHM的细胞中免疫沉淀出的蛋白质是E2糖蛋白：（1）用金黄色葡萄球菌V-8蛋白酶处理抗FcγR mab和抗E2 mab免疫沉淀出的180,000道尔顿蛋白质获得的部分蛋白水解图谱相同。（2）从感染MHV-JHM的细胞中进行的顺序免疫沉淀实验表明，抗E2 mab和抗FcγR mab 2.4G2识别同一条多肽链，（3）放线菌素D不影响抗FcγR mab免疫沉淀出的180,000道尔顿多肽链的诱导和表达，表明该蛋白质是病毒来源的。
