title: Asn 362 in gp120 contributes to enhanced fusogenicity by CCR5-restricted HIV-1 envelope glycoprotein variants from patients with AIDS.
abstract: BACKGROUND
  CCR5-restricted (R5) human immunodeficiency virus type 1 (HIV-1) variants cause CD4+ T-cell loss in the majority of individuals who progress to AIDS, but mechanisms underlying the pathogenicity of R5 strains are poorly understood. To better understand envelope glycoprotein (Env) determinants contributing to pathogenicity of R5 viruses, we characterized 37 full-length R5 Envs from cross-sectional and longitudinal R5 viruses isolated from blood of patients with asymptomatic infection or AIDS, referred to as pre-AIDS (PA) and AIDS (A) R5 Envs, respectively.
  
  
  RESULTS
  Compared to PA-R5 Envs, A-R5 Envs had enhanced fusogenicity in quantitative cell-cell fusion assays, and reduced sensitivity to inhibition by the fusion inhibitor T-20. Sequence analysis identified the presence of Asn 362 (N362), a potential N-linked glycosylation site immediately N-terminal to CD4-binding site (CD4bs) residues in the C3 region of gp120, more frequently in A-R5 Envs than PA-R5 Envs. N362 was associated with enhanced fusogenicity, faster entry kinetics, and increased sensitivity of Env-pseudotyped reporter viruses to neutralization by the CD4bs-directed Env mAb IgG1b12. Mutagenesis studies showed N362 contributes to enhanced fusogenicity of most A-R5 Envs. Molecular models indicate N362 is located adjacent to the CD4 binding loop of gp120, and suggest N362 may enhance fusogenicity by promoting greater exposure of the CD4bs and/or stabilizing the CD4-bound Env structure.
  
  
  CONCLUSIONS
  Enhanced fusogenicity is a phenotype of the A-R5 Envs studied, which was associated with the presence of N362, enhanced HIV-1 entry kinetics and increased CD4bs exposure in gp120. N362 contributes to fusogenicity of R5 Envs in a strain dependent manner. Our studies suggest enhanced fusogenicity of A-R5 Envs may contribute to CD4+ T-cell loss in subjects who progress to AIDS whilst harbouring R5 HIV-1 variants. N362 may contribute to this effect in some individuals.
authors: Macfarlane Burnet Institute for Medical Research & Public Health, Melbourne, Victoria, Australia. Jasminka@burnet.edu.au
authors: Jasminka
authors: J
authors: Sterjovski
authors: Melissa J
authors: MJ
authors: Churchill
authors: Anne
authors: A
authors: Ellett
authors: Lachlan R
authors: LR
authors: Gray
authors: Michael J
authors: MJ
authors: Roche
authors: Rebecca L
authors: RL
authors: Dunfee
authors: Damian F J
authors: DF
authors: Purcell
authors: Nitin
authors: N
authors: Saksena
authors: Bin
authors: B
authors: Wang
authors: Secondo
authors: S
authors: Sonza
authors: Steven L
authors: SL
authors: Wesselingh
authors: Ingrid
authors: I
authors: Karlsson
authors: Eva-Maria
authors: EM
authors: Fenyo
authors: Dana
authors: D
authors: Gabuzda
authors: Anthony L
authors: AL
authors: Cunningham
authors: Paul R
authors: PR
authors: Gorry
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000821:virology*; D001216:Asparagine / Q000502:physiology*; D015704:CD4 Antigens / Q000378:metabolism; D002459:Cell Fusion; D002478:Cells, Cultured; D015699:HIV Envelope Protein gp120 / Q000737:chemistry*; D015497:HIV-1 / Q000737:chemistry / Q000472:pathogenicity / Q000502:physiology*; D006801:Humans; D007963:Leukocytes, Mononuclear; D008958:Models, Molecular; D019713:Receptors, CCR5 / Q000378:metabolism*; D014774:Virulence; D053585:Virus Attachment
chemical_list: D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D019713:Receptors, CCR5; D001216:Asparagine