title: Antibodies to an interfering epitope in hepatitis C virus E2 can mask vaccine-induced neutralizing activity.
abstract: Hepatitis C virus (HCV) neutralization occurring at the E2 region 412-426 (EP-I) could be enhanced when antibodies directed specifically to the E2 region 434-446 (EP-II) were removed from serum samples of persistently infected patients and vaccinated chimpanzees, a phenomenon of so-called antibody interference. Here, we show that this type of interference can be observed in individuals after immunization with recombinant E1E2 proteins. One hundred twelve blinded serum samples from a phase I, placebo-controlled, dose escalation trial using recombinant HCV E1E2 with MF59C.1 adjuvant in healthy HCV-negative adults were tested in enzyme-linked immunosorbent assay for binding reactivity to peptides representing the E2 regions 412-426 (EP-I) and 434-446 (EP-II). All samples were subsequently tested for neutralizing activity using cell-culture HCV 1a(H77)/2a chimera, HCV pseudotype particles (HCVpp) H77, and HCVpp HCV-1 after treatment to remove EP-II-specific antibodies or mock treatment with a control peptide. Among the 112 serum samples, we found 22 double positive (EP-I and EP-II), 6 EP-II positive only, 14 EP-I positive only, and 70 double negative. Depleting EP-II antibodies from double-positive serum samples increased 50% inhibitory dose (ID50) neutralizing antibody titers (up to 4.9-fold) in up to 72% of samples (P ≤ 0.0005), contrasting with ID50 neutralization titer increases in 2 of 70 double-negative samples (2.9%; P > 0.5). In addition, EP-I-specific antibody levels in serum samples showed a significant correlation with ID50 neutralization titers when EP-II antibodies were removed (P < 0.0003).
  
  
  CONCLUSIONS
  These data show that antibodies to the region 434-446 are induced during immunization of individuals with recombinant E1E2 proteins, and that these antibodies can mask effective neutralizing activity from EP-I-specific antibodies. Elicitation of EP-II-specific antibodies with interfering capacity should be avoided in producing an effective cross-neutralizing vaccine aimed at the HCV envelope proteins.
authors.affiliation: Division of Viral Products, CBER/FDA, Silver Spring, MD.
authors.forename: Alla
authors.initials: A
authors.lastname: Kachko
authors.affiliation: Division of Infectious Diseases, Allergy and Immunology, Saint Louis University School of Medicine, St Louis, MO.
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Frey
authors.affiliation: Division of Biostatistics, Office of Biostatistics and Epidemiology, CBER/FDA, Silver Spring, MD.
authors.forename: Lev
authors.initials: L
authors.lastname: Sirota
authors.affiliation: Division of Infectious Diseases, Allergy and Immunology, Saint Louis University School of Medicine, St Louis, MO.
authors.forename: Ranjit
authors.initials: R
authors.lastname: Ray
authors.affiliation: Division of Viral Products, CBER/FDA, Silver Spring, MD.
authors.forename: Frances
authors.initials: F
authors.lastname: Wells
authors.affiliation: Division of Viral Products, CBER/FDA, Silver Spring, MD.
authors.forename: Iryna
authors.initials: I
authors.lastname: Zubkova
authors.affiliation: Division of Hematology, CBER/FDA, Silver Spring, MD.
authors.forename: Pei
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Division of Viral Products, CBER/FDA, Silver Spring, MD.
authors.forename: Marian E
authors.initials: ME
authors.lastname: Major
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000276:immunology*; D000939:Epitopes / Q000276:immunology*; D016174:Hepacivirus / Q000276:immunology*; D018937:Hepatitis C Antibodies / Q000276:immunology*; D006801:Humans; D002679:Pan troglodytes; D014761:Viral Hepatitis Vaccines / Q000276:immunology*
chemical_list: D057134:Antibodies, Neutralizing; D000939:Epitopes; D018937:Hepatitis C Antibodies; D014761:Viral Hepatitis Vaccines