title: Functional Contacts between MPER and the Anti-HIV-1 Broadly Neutralizing Antibody 4E10 Extend into the Core of the Membrane.
abstract: The exceptional breadth of broadly neutralizing antibodies (bNAbs) against the membrane-proximal external region (MPER) of the transmembrane protein gp41 makes this class of antibodies an ideal model to design HIV vaccines. From a practical point of view, however, the preparation of vaccines eliciting bNAbs is still a major roadblock that limits their clinical application. Fresh mechanistic insights are necessary to develop more effective strategies. In particular, the function of the unusually long complementarity-determining region three of the heavy chain (CDRH3) of 4E10, an anti-MPER bNAb, is an open question that fascinates researchers in the field. Residues comprising the apex region are dispensable for engagement of the epitope in solution; still, their single mutation profoundly impairs the neutralization capabilities of the antibody. Since this region is very hydrophobic, it has been proposed that the apex is essential for anchoring the antibody to the viral membrane where MPER resides. Herein, we have critically examined this idea using structural, biophysical, biochemical, and cell-based approaches. Our results demonstrate that the apex region is not just a "greasy" spot merely increasing the affinity of the antibody for the membrane. We demonstrate the three-dimensional engagement of the apex region of the CDRH3 with the conglomerate of gp41 epitope and membrane lipids as a means of effective binding and neutralization of the virus. This mechanism of recognition suggests a standard route of antibody ontogeny. Therefore, we need to focus our efforts on recreating a more realistic MPER/lipid immunogen in order to generate more effective anti-HIV-1 vaccines.
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, Bilbao 48080, Spain; Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Edurne
authors.initials: E
authors.lastname: Rujas
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, Bilbao 48080, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Insausti
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, Bilbao 48080, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: García-Porras
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, Bilbao 48080, Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: Sánchez-Eugenia
authors.affiliation: Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Tsumoto
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, Bilbao 48080, Spain. Electronic address: gbpniesj@lg.ehu.es.
authors.forename: José L
authors.initials: JL
authors.lastname: Nieva
authors.affiliation: Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan; Laboratory of Global Healthcare, School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-Ku, Fukuoka 812-8582, Japan. Electronic address: jose@phar.kyushu-u.ac.jp.
authors.forename: Jose M M
authors.initials: JM
authors.lastname: Caaveiro
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000080908:Broadly Neutralizing Antibodies; D002462:Cell Membrane / Q000378:metabolism; D018360:Crystallography, X-Ray; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D057809:HEK293 Cells; D015483:HIV Antibodies / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000378:metabolism*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D008051:Lipid Bilayers; D014364:Tryptophan
chemical_list: C558559:4E10 monoclonal antibody; D000911:Antibodies, Monoclonal; D000080908:Broadly Neutralizing Antibodies; D000939:Epitopes; D015483:HIV Antibodies; D015700:HIV Envelope Protein gp41; D008051:Lipid Bilayers; D014364:Tryptophan
keywords: 4E10 antibody; antigen–antibody binding; biomolecular recognition; complementarity-determining region; protein–membrane interaction; vaccine development