title: Regulation of the susceptibility of HIV-1 to a neutralizing antibody KD-247 by nonepitope mutations distant from its epitope.
abstract: OBJECTIVE
  A humanized neutralizing antibody, KD-247, targets the V3 loop of HIV-1 Env. HIV-1 bearing the GPGR sequence at the V3 loop is potentially susceptible to KD-247. However, not all GPGR-positive HIV-1 isolates are neutralized by KD-247. We examined the potential mechanism by which the susceptibility of HIV-1 to KD-247-mediated neutralization is regulated.
  
  
  METHODS
  We searched for nonepitope neutralization regulatory (NNR) mutations that sensitize GPGR-bearing HIV-1AD8 to KD-247 and mapped the locations of such mutations relative to the V3 loop.
  
  
  METHODS
  : We generated a functional HIV-1AD8 Env library, and evaluated the viral susceptibility to KD-247 by measuring the half-inhibitory concentration (IC50) to KD-247 on TZM-bl cell assay.
  
  
  RESULTS
  We identified nine KD-247-sensitizing NNR mutations from 30 mutations in various regions of gp120, including the V1/V2 loop, C2, V3 loop, C4, and C5. They specifically affected KD-247-mediated neutralization, as they did not affect the b12-mediated neutralization. When combined, the KD-247-sensitizing NNR mutations additively sensitized the virus to KD-247 by up to 10 000 folds. The KD-247-sensitizing NNR mutations increased KD-247 binding to the virion. Notably, the NNR mutation in C4 coincides with the CD4-binding site of gp120.
  
  
  CONCLUSIONS
  Given that most of the KD-247-sensitizing NNR mutations are remote from V3 loop, it is reasonable to hypothesize that the steady-state, local conformation of the V3 loop is regulated by the interdomain contact of gp120. Our mutational analysis complements crystallographic studies by helping provide a better understanding of the steady-state conformation and the functional geometry of Env.
authors.affiliation: AIDS Research Center, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Takizawa
authors.forename: Kosuke
authors.initials: K
authors.lastname: Miyauchi
authors.forename: Emiko
authors.initials: E
authors.lastname: Urano
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kusagawa
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kitamura
authors.forename: Satoshi
authors.initials: S
authors.lastname: Naganawa
authors.forename: Toshio
authors.initials: T
authors.lastname: Murakami
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Honda
authors.forename: Naoki
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Jun
authors.initials: J
authors.lastname: Komano
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000276:immunology*; D057134:Antibodies, Neutralizing / Q000276:immunology*; D002874:Chromosome Mapping; D004252:DNA Mutational Analysis; D000939:Epitopes / Q000235:genetics*; D015483:HIV Antibodies / Q000276:immunology*; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D015497:HIV-1 / Q000235:genetics / Q000276:immunology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D009154:Mutation; D009500:Neutralization Tests; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D011487:Protein Conformation; D014771:Virion
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D057134:Antibodies, Neutralizing; D000939:Epitopes; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; C059762:HIV envelope protein gp120 (305-321); D010446:Peptide Fragments