title: Complement-mediated enhancement of antibody function for neutralization of pseudotype virus containing hepatitis C virus E2 chimeric glycoprotein.
abstract: We previously reported a number of features of hepatitis C virus (HCV) chimeric glycoproteins related to pseudotype virus entry into mammalian cells. In this study, pseudotype virus was neutralized by HCV E2 glycoprotein-specific antibodies and infected human sera. Neutralization (50% reduction of pseudotype virus plaque formation) was observed with two human immunoglobulin G1 monoclonal antibodies (MAbs) at concentrations of between 2.5 and 10 microg/ml. A hyperimmune rabbit antiserum to an E2 hypervariable region 1 (HVR1) mimotope also exhibited an HCV E2 pseudotype virus neutralization titer of approximately 1/50. An E1 pseudotype virus used as a negative control was not neutralized to a significant level (<1/10) by these MAbs or rabbit antiserum to E2 HVR1. Since HCV probably has a lipid envelope, the role of complement in antibody-mediated virus neutralization was examined. Significant increases in the neutralization titers of the human MAbs (approximately 60- to 160-fold higher) and rabbit antiserum to HVR1 mimotopes (approximately 10-fold higher) were observed upon addition of guinea pig complement. Further, these studies suggested that complement activation occurred primarily by the classical pathway, since a deficiency in the C4 component led to a significant decrease in the level of virus neutralization. This same decrease was not observed with factor B-deficient complement. We also determined that 9 of 56 HCV-infected patient sera (16%) had detectable pseudotype virus neutralization activity at serum dilutions of between 1/20 and 1/50 and that complement addition enhanced the neutralization activity of some of the HCV-infected human sera. Taken together, these results suggest that during infection, HCV E2 glycoprotein induces a weak neutralizing antibody response, that those antibodies can be measured in vitro by the surrogate pseudotype virus plaque reduction assay, and that neutralization function can be augmented by complement.
authors.affiliation: Department of Internal Medicine, Saint Louis University, 3635 Vista Ave., St. Louis, Missouri 63110, USA.
authors.forename: Keith
authors.initials: K
authors.lastname: Meyer
authors.forename: Arnab
authors.initials: A
authors.lastname: Basu
authors.forename: Craig T
authors.initials: CT
authors.lastname: Przysiecki
authors.forename: L Martin
authors.initials: LM
authors.lastname: Lagging
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Di Bisceglie
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Conley
authors.forename: Ranjit
authors.initials: R
authors.lastname: Ray
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D019067:Antibody-Dependent Enhancement; D003165:Complement System Proteins / Q000378:metabolism*; D016174:Hepacivirus / Q000235:genetics / Q000276:immunology*; D006526:Hepatitis C / Q000276:immunology; D018937:Hepatitis C Antibodies / Q000097:blood / Q000276:immunology*; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D009500:Neutralization Tests; D011993:Recombinant Fusion Proteins / Q000276:immunology; D014759:Viral Envelope Proteins / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D018937:Hepatitis C Antibodies; D007106:Immune Sera; D011993:Recombinant Fusion Proteins; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus; D003165:Complement System Proteins