title: Epitope mapping of M36, a human antibody domain with potent and broad HIV-1 inhibitory activity.
abstract: M36 is the first member of a novel class of potent HIV-1 entry inhibitors based on human engineered antibody domains (eAds). It exhibits broad inhibitory activity suggesting that its CD4-induced epitope is highly conserved. Here, we describe fine mapping of its epitope by using several approaches. First, a panel of mimotopes was affinity-selected from a random peptide library and potential m36-binding residues were computationally predicted. Second, homology modeling of m36 and molecular docking of m36 onto gp120 revealed potentially important residues in gp120-m36 interactions. Third, the predicted contact residues were verified by site-directed mutagenesis. Taken together, m36 epitope comprising three discontinuous sites including six key gp120 residues (Site C1: Thr123 and Pro124; Site C3: Glu370 and Ile371; Site C4: Met426 and Trp427) were identified. In the 3D structure of gp120, the sites C1 and C4 are located in the bridging sheet and the site C3 is within the β15-α3 excursion, which play essential roles for the receptor- and coreceptor-binding and are major targets of neutralizing antibodies. Based on these results we propose a precise localization of the m36 epitope and suggest a mechanism of its broad inhibitory activity which could help in the development of novel HIV-1 therapeutics based on eAds.
authors.affiliation: MOH Key Laboratory of Systems Biology of Pathogens and AIDS Research Center, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wan
authors.forename: Jianping
authors.initials: J
authors.lastname: Sun
authors.forename: Weizao
authors.initials: W
authors.lastname: Chen
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Yuan
authors.forename: Huihui
authors.initials: H
authors.lastname: Chong
authors.forename: Ponraj
authors.initials: P
authors.lastname: Prabakaran
authors.forename: Dimiter S
authors.initials: DS
authors.lastname: Dimitrov
authors.forename: Yuxian
authors.initials: Y
authors.lastname: He
mesh_terms: D057134:Antibodies, Neutralizing / Q000378:metabolism; D018604:Epitope Mapping / Q000379:methods*; D000939:Epitopes / Q000276:immunology; D015483:HIV Antibodies / Q000276:immunology; D015699:HIV Envelope Protein gp120 / Q000276:immunology / Q000378:metabolism; D015497:HIV-1 / Q000276:immunology*; D006801:Humans
chemical_list: D057134:Antibodies, Neutralizing; D000939:Epitopes; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120