title: Low frequency of broadly neutralizing HIV antibodies during chronic infection even in quaternary epitope targeting antibodies containing large numbers of somatic mutations.
abstract: Neutralizing antibodies (Abs) are thought to be a critical component of an appropriate HIV vaccine response. It has been proposed that Abs recognizing conformationally dependent quaternary epitopes on the HIV envelope (Env) trimer may be necessary to neutralize diverse HIV strains. A number of recently described broadly neutralizing monoclonal Abs (mAbs) recognize complex and quaternary epitopes. Generally, many such Abs exhibit extensive numbers of somatic mutations and unique structural characteristics. We sought to characterize the native antibody (Ab) response against circulating HIV focusing on such conformational responses, without a prior selection based on neutralization. Using a capture system based on VLPs incorporating cleaved envelope protein, we identified a selection of B cells that produce quaternary epitope targeting Abs (QtAbs). Similar to a number of broadly neutralizing Abs, the Ab genes encoding these QtAbs showed extensive numbers of somatic mutations. However, when expressed as recombinant molecules, these Abs failed to neutralize virus or mediate ADCVI activity. Molecular analysis showed unusually high numbers of mutations in the Ab heavy chain framework 3 region of the variable genes. The analysis suggests that large numbers of somatic mutations occur in Ab genes encoding HIV Abs in chronically infected individuals in a non-directed, stochastic, manner.
authors.affiliation: Department of Pediatrics, University at Buffalo, Buffalo, NY 14222, United States; Department of Microbiology and Immunology, University at Buffalo, Buffalo, NY 14222, United States.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Hicar
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, United States; Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, United States.
authors.forename: Xuemin
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Pathology, Microbiology and Immunology Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Medicine, Vanderbilt, University Medical Center, Nashville, TN 37232, United States.
authors.forename: Spyros A
authors.initials: SA
authors.lastname: Kalams
authors.affiliation: Department of Pediatrics, University at Buffalo, Buffalo, NY 14222, United States.
authors.forename: Hakimuddin
authors.initials: H
authors.lastname: Sojar
authors.affiliation: Department of Medicine, University of California, Irvine, CA 92668, United States.
authors.forename: Gary
authors.initials: G
authors.lastname: Landucci
authors.affiliation: Department of Medicine, University of California, Irvine, CA 92668, United States.
authors.forename: Donald N
authors.initials: DN
authors.lastname: Forthal
authors.affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, United States; Department of Pathology, Microbiology and Immunology Vanderbilt University Medical Center, Nashville, TN 37232, United States; Children's Healthcare of Atlanta, Atlanta, GA 30329, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Spearman
authors.affiliation: Department of Pathology, Microbiology and Immunology Vanderbilt University Medical Center, Nashville, TN 37232, United States; The Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Nashville, TN 37232, United States. Electronic address: james.crowe@vanderbilt.edu.
authors.forename: James E
authors.initials: JE
authors.lastname: Crowe
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D057134:Antibodies, Neutralizing / Q000235:genetics* / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D002469:Cell Separation; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D005434:Flow Cytometry; D005803:Genes, Immunoglobulin / Q000502:physiology; D015483:HIV Antibodies / Q000235:genetics* / Q000276:immunology*; D015658:HIV Infections / Q000276:immunology*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics; D009154:Mutation; D054299:env Gene Products, Human Immunodeficiency Virus / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D000939:Epitopes; D015483:HIV Antibodies; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D054299:env Gene Products, Human Immunodeficiency Virus
keywords: Antibodies; B cells; HIV; Human; Monoclonal antibodies; Neutralization