title: Functional and Structural Characterization of Human V3-Specific Monoclonal Antibody 2424 with Neutralizing Activity against HIV-1 JRFL.
abstract: The V3 region of HIV-1 gp120 is important for virus-coreceptor interaction and highly immunogenic. Although most anti-V3 antibodies neutralize only the sensitive tier 1 viruses, anti-V3 antibodies effective against the more resistant viruses exist, and a better understanding of these antibodies and their epitopes would be beneficial for the development of novel vaccine immunogens against HIV. The HIV-1 isolate JRFL with its cryptic V3 is resistant to most V3-specific monoclonal antibodies (MAbs). However, the V3 MAb 2424 achieves 100% neutralization against JRFL. 2424 is encoded by IGHV3-53 and IGLV2-28 genes, a pairing rarely used by the other V3 MAbs. 2424 also has distinct binding and neutralization profiles. Studies of 2424-mediated neutralization of JRFL produced with a mannosidase inhibitor further revealed that its neutralizing activity is unaffected by the glycan composition of the virus envelope. To understand the distinct activity of 2424, we determined the crystal structure of 2424 Fab in complex with a JRFL V3 peptide and showed that the 2424 epitope is located at the tip of the V3 crown ((307)IHIGPGRAFYT(319)), dominated by interactions with His(P308), Pro(P313), and Arg(P315). The binding mode of 2424 is similar to that of the well-characterized MAb 447-52D, although 2424 is more side chain dependent. The 2424 epitope is focused on the very apex of V3, away from nearby glycans, facilitating antibody access. This feature distinguishes the 2424 epitope from the other V3 crown epitopes and indicates that the tip of V3 is a potential site to target and incorporate into HIV vaccine immunogens.
  
  
  OBJECTIVE
  HIV/AIDS vaccines are crucial for controlling the HIV epidemics that continue to afflict millions of people worldwide. However, HIV vaccine development has been hampered by significant scientific challenges, one of which is the inability of HIV vaccine candidates evaluated thus far to elicit production of potent and broadly neutralizing antibodies. The V3 loop is one of the few immunogenic targets on the virus envelope glycoprotein that can induce neutralizing antibodies, but in many viruses, parts of V3 are inaccessible for antibody recognition. This study examined a V3-specific monoclonal antibody that can completely neutralize HIV-1 JRFL, a virus isolate resistant to most V3 antibodies. Our data reveal that this antibody recognizes the most distal tip of V3, which is not as occluded as other parts of V3. Hence, the epitope of 2424 is in one of the vulnerable sites on the virus that may be exploited in designing HIV vaccine immunogens.
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA.
authors.forename: Rajnish
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York, USA.
authors.forename: Ruimin
authors.initials: R
authors.lastname: Pan
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA.
authors.forename: Chitra
authors.initials: C
authors.lastname: Upadhyay
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA.
authors.forename: Luzia
authors.initials: L
authors.lastname: Mayr
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA.
authors.forename: Sandra
authors.initials: S
authors.lastname: Cohen
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA.
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Wang
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA.
authors.forename: Preetha
authors.initials: P
authors.lastname: Balasubramanian
authors.affiliation: Department of Environment Medicine, NYU School of Medicine, New York, New York, USA.
authors.forename: Arthur
authors.initials: A
authors.lastname: Nádas
authors.affiliation: Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Seaman
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Zolla-Pazner
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA.
authors.forename: Miroslaw K
authors.initials: MK
authors.lastname: Gorny
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York, USA xiangpeng.kong@med.nyu.edu catarina.hioe@nyumc.org.
authors.forename: Xiang-Peng
authors.initials: XP
authors.lastname: Kong
authors.affiliation: Veterans Affairs New York Harbor Healthcare System, New York, New York, USA Department of Pathology, NYU School of Medicine, New York, New York, USA xiangpeng.kong@med.nyu.edu catarina.hioe@nyumc.org.
authors.forename: Catarina E
authors.initials: CE
authors.lastname: Hioe
mesh_terms: D016915:AIDS Vaccines / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000648:ultrastructure; D057134:Antibodies, Neutralizing / Q000276:immunology*; D000918:Antibody Specificity / Q000276:immunology; D002460:Cell Line; D018360:Crystallography, X-Ray; D000939:Epitopes / Q000276:immunology; D057809:HEK293 Cells; D015483:HIV Antibodies / Q000276:immunology*; D015488:HIV Antigens / Q000276:immunology; D015699:HIV Envelope Protein gp120 / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology / Q000648:ultrastructure; D008361:Mannosidases / Q000037:antagonists & inhibitors; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000276:immunology; D017434:Protein Structure, Tertiary
chemical_list: D016915:AIDS Vaccines; D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D000939:Epitopes; D015483:HIV Antibodies; D015488:HIV Antigens; D015699:HIV Envelope Protein gp120; D007140:Immunoglobulin Fab Fragments; D011134:Polysaccharides; C514793:gp120 protein, Human immunodeficiency virus 1; D008361:Mannosidases