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Crystal structure of a human immunodeficiency virus type 1 neutralizing antibody, 50.1, in complex with its V3 loop peptide antigen.

ABSTRACT: The crystal structure of the Fab fragment of a human immunodeficiency virus type 1 (HIV-1) neutralizing monoclonal antibody Fab has been determined at 2.8 A resolution in complex with a linear 16-residue peptide from the third hypervariable region (V3) of gp120. The first 9 residues of the peptide are ordered in the electron density maps, and their conformation is in partial agreement with the beta-strand-type II beta-turn structure predicted for this portion of the V3 loop. Notably, several of the peptide residues that are well conserved among different HIV-1 isolates contact a nonpolar 25-A-long groove in the antibody-combining site. The largely extended structure of the peptide differs from the beta-turns seen as the primary determinants in other published anti-peptide Fab structures. Analysis of the specific Fab-peptide interactions only partially explains the MN isolate specificity shown by this antibody.

SUBMITTER: Rini JM

PROVIDER: S-EPMC46921 | biostudies-other | 1993 Jul

REPOSITORIES: biostudies-other

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Crystal structure of a human immunodeficiency virus type 1 neutralizing antibody, 50.1, in complex with its V3 loop peptide antigen.

Rini J M JM Stanfield R L RL Stura E A EA Salinas P A PA Profy A T AT Wilson I A IA

Proceedings of the National Academy of Sciences of the United States of America 19930701 13

The crystal structure of the Fab fragment of a human immunodeficiency virus type 1 (HIV-1) neutralizing monoclonal antibody Fab has been determined at 2.8 A resolution in complex with a linear 16-residue peptide from the third hypervariable region (V3) of gp120. The first 9 residues of the peptide are ordered in the electron density maps, and their conformation is in partial agreement with the beta-strand-type II beta-turn structure predicted for this portion of the V3 loop. Notably, several of ...[more]

PMID: 8327513

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Project description:In clinical trials, HIV-1 broadly neutralizing antibodies (bnAbs) effectively lower plasma viremia and delay virus reemergence. The presence of less neutralization-susceptible strains prior to treatment decreases the efficacy of these antibody-based treatments, but neutralization sensitivity often cannot be predicted by sequence analysis alone. We found that phenotypically confirmed CXCR4-utilizing strains are less neutralization sensitive, especially to variable loop 3 (V3 loop)-directed bnAbs, than exclusively CCR5-utilizing strains in some, but not all, cases. Homology modeling suggested that the primary V3 loop bnAb epitope is equally accessible among CCR5- and CXCR4-using strains, although variants that exclusively use CXCR4 have V3 loop protrusions that interfere with CCR5 receptor interactions. Homology modeling also showed that among some, but not all, envelopes with decreased neutralization sensitivity, V1 loop orientation interfered with V3 loop-directed bnAb binding. Thus, there are likely different structural reasons for the coreceptor usage restriction and the different bnAb susceptibilities. Importantly, we show that individuals harboring envelopes with higher likelihood of using CXCR4 or greater predicted V1 loop interference have faster virus rebound and a lower maximum decrease in plasma viremia, respectively, after treatment with a V3 loop bnAb. Knowledge of receptor usage and homology models may be useful in developing future algorithms that predict treatment efficacy with V3 loop bnAbs.IMPORTANCE The efficacy of HIV-1 broadly neutralizing antibody (bnAb) therapies may be compromised by the preexistence of less susceptible variants. Sequence-based methods are needed to predict pretreatment variants' neutralization sensitivities. HIV-1 strains that exclusively use the CXCR4 receptor rather than the CCR5 receptor are less neutralization susceptible, especially to variable loop 3 (V3 loop) bnAbs in some, but not all, instances. While the inability to utilize the CCR5 receptor maps to a predicted protrusion in the envelope V3 loop, this viral determinant does not directly influence V3 loop bnAb sensitivity. Homology modeling predicts that contact between the envelope V1 loop and the antibody impacts V3 loop bnAb susceptibility in some cases. Among pretreatment envelopes, increased probability of using CXCR4 and greater predicted V1 interference are associated with faster virus rebound and a smaller decrease in the plasma virus level, respectively, after V3 loop bnAb treatment. Receptor usage information and homology models may be useful for predicting V3 loop bnAb therapy efficacy.

Dataset Information

Crystal structure of a human immunodeficiency virus type 1 neutralizing antibody, 50.1, in complex with its V3 loop peptide antigen.

Publications

Crystal structure of a human immunodeficiency virus type 1 neutralizing antibody, 50.1, in complex with its V3 loop peptide antigen.

Similar Datasets

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