title: Differential role of V3-specific antibodies in neutralization assays involving primary and laboratory-adapted isolates of HIV type 1.
abstract: To identify epitopes important in neutralizing primary HIV-1 isolates, we have selectively depleted HIV-1 sera of antibodies specific for the third hypervariable region (V3) of the HIV-1 envelope glycoprotein gp120, and then assessed the functional consequences of such depletion in neutralization assays. The nucleotide sequence of the V3 loop region from HIV-1 PBMC DNA was determined for three HIV-1-infected patients, corresponding peptides were synthesized, and then subsequently used for V3 depletion of the patient sera. Depletion using a single clade B V3 peptide was capable of depleting > 98% of binding antibodies to multiple clade B V3 peptides, including those with changes within the GPGX tip of the loop. Depleted and undepleted sera were studied for their ability to neutralize both laboratory-adapted HIV-1MN and two primary HIV-1 isolates with known V3 sequences, using a viral infectivity reduction assay. While the majority of HIV-1MN neutralization was lost on V3 depletion, the loss in neutralization capacity against primary isolates by these same V3-depleted sera was substantially less pronounced. This suggests that V3 peptide-specific antibodies within HIV-1 serum play a fundamentally different role in mediating neutralization in assays involving laboratory-adapted and primary isolates and implicates antibodies with epitope specificities outside of V3 as major determinants in neutralization assays involving primary isolates.
authors.affiliation: Division of Retrovirology, Walter Reed Army Institute of Research, Rockville, Maryland 20850, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: Vancott
authors.forename: V R
authors.initials: VR
authors.lastname: Polonis
authors.forename: L D
authors.initials: LD
authors.lastname: Loomis
authors.forename: N L
authors.initials: NL
authors.lastname: Michael
authors.forename: P L
authors.initials: PL
authors.lastname: Nara
authors.forename: D L
authors.initials: DL
authors.lastname: Birx
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D004279:DNA, Viral / Q000235:genetics; D000939:Epitopes / Q000276:immunology; D015483:HIV Antibodies / Q000276:immunology*; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D015658:HIV Infections / Q000276:immunology* / Q000821:virology; D015497:HIV-1 / Q000276:immunology* / Q000302:isolation & purification; D006801:Humans; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D011487:Protein Conformation
chemical_list: D004279:DNA, Viral; D000939:Epitopes; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; C059762:HIV envelope protein gp120 (305-321); D010446:Peptide Fragments