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81 Characteristics of Anti-HIV-1 Antibody Binding and HIV-1 Envelope Glycoprotein on Infected Lymphocytes
G. Gorse*1,2, G. Patel2, R. Belshe2, and the NIAID HIV Vaccine Trials Network
1VA Med. Ctr. and 2St. Louis Univ., MO, USA
Background: Certain recombinant (r) HIV-1 envelope glycoprotein vaccines can induce antibodies that bind to lab-adapted strains of HIV-1 and primary isolate R5 strains of HIV-1 on infected cells, but do not neutralize R5 strains. We asked whether this represents binding to native envelope or monomeric gp120.
Methods: Using a flow cytometric indirect immunofluorescence assay, we measured binding of antibodies to a panel of R5 primary isolates of HIV-1 on peripheral blood mononuclear cells (PBL). PBL were either CD8+ cell-depleted, infected, and maintained in culture for 7 days prior to CD19+ cell depletion and staining or after both cell depletions were incubated for up to 90 min. with high titer R5 virus with and without added monomeric HIV-1MN rgp160, and then washed and stained immediately thereafter. HIV-1-treated and control cells were reacted with anti-HIV-1 antibody and stained with anti-CD3 PE and anti-IgG FITC, and the lymphocyte population was analyzed by 2-color flow cytometry.
Results: Sera from 5 selected recipients of recombinant canarypox virus vaccine expressing MN gp120 (Aventis Pasteur) who were boosted with SF-2 rgp120 subunit vaccine (Chiron Vaccines), and from HIV-1-infected patient controls that exhibited antibody binding to R5 HIV-1-infected cells were further tested. Antibody binding to uninfected cells treated with virus for up to 90 min. prior to staining, was absent or detected only at lower levels compared with HIV-1-infected cells. Addition of monomeric rgp160 to the R5 virus used to prepare cells did not increase antibody binding to the uninfected cells. Antibodies to gp120 with known neutralizing activity against R5 viruses were also tested. The human monoclonal antibodies 2G12 and F105 bound to R5 HIV-1-infected cells. In addition, binding of goat antiserum to gp120 MN peptide T1-SP10MN(A) was detected against infected cells.
Conclusions: Antibodies to native envelope on HIV-1-infected cells, including those that were vaccine-induced, were present. Although binding to monomeric gp120 may also have been detected, it appears to be at lower levels than to native envelope glycoprotein in this assay, and it may be HIV-1 strain dependent.
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