Autoreactivity and Exceptional CDR Plasticity (but Not Unusual Polyspecificity) Hinder Elicitation of the Anti-HIV Antibody 4E10

• DOI: 10.1371/journal.ppat.1003639
• Publication Date: 2013-09-26T21:12:46Z
• Authors: Kathryn A. K. Finton; Kevin Larimore; H. Benjamin Larman; Della Friend; Colin Correnti; Peter B. Rupert; Stephen J. Elledge; Philip D. Greenberg; Roland K. Strong
• Keywords: 0301 basic medicine; 570; Proteome; QH301-705.5; Cardiolipins; 610; Mice, Transgenic; HIV Antibodies; Autoantigens; Epitopes; Mice; 03 medical and health sciences; Animals; Humans; Inositol 1,4,5-Trisphosphate Receptors; Biology (General); Autoantibodies; Antibodies, Monoclonal; RC581-607; Complementarity Determining Regions; 3. Good health; HIV-1; Immunologic diseases. Allergy; Immunoglobulin Heavy Chains; Broadly Neutralizing Antibodies; Research Article

The broadly-neutralizing anti-HIV antibody 4E10 recognizes an epitope in the membrane-proximal external region of HIV envelope protein gp41. Previous attempts to elicit by vaccination with envelope-derived or reverse-engineered immunogens have failed. It was presumed that ontogeny 4E10-equivalent responses blocked inherent autoreactivity and exceptional polyreactivity. We generated heavy-chain knock-in mice, which displayed significant B cell dysregulation, consistent recognition autoantigen/s presumption tolerance mechanisms may hinder elicitation responses. Previously proposed candidate autoantigens include mitochondrial lipid cardiolipin a nuclear splicing factor, 3B3. However, using carefully-controlled assays, bound only weakly cardiolipin-containing liposomes, but also negatively-charged, non-cardiolipin-containing liposomes comparably poorly. 4E10/liposome binding predominantly mediated electrostatic interactions rather than hydrophobic interactions. crystal structure free ligands showed dramatic restructuring combining site, occluding site revealing profound flexibility, creating electropositive pocket non-specific phospholipid headgroups. These results strongly suggested antigens other mediate autoreactivity. Using synthetic peptide library spanning human proteome, we determined displays limited focused, unexceptional, polyspecificity. identified novel autoepitope shared three ER-resident inositol trisphosphate receptors, validated through studies immunohistochemistry. Tissue staining demonstrated reactivity type 1 receptor as most likely autoantigen, is inconsistent factor demonstrate competes MPER antigen be distinct enough permit eliciting 4E10-like antibodies, evading autoimmunity directed engineering. for highly-matured antibody, preclude conventional immunization strategies.