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Generation of neutralization-resistant HIV-1 in vitro due to amino acid interchanges of third hypervariable env
T Masuda1, S Matsushita, M J Kuroda
1Department of Biodefence and Medical Virology, Kumamoto University Medical School, Japan.
Abstract:
Antigenic mutants of HIV-1 were isolated from three plaque-cloned viruses by the resistance of the virus to neutralizing mAb 0.5 beta against V3 domain of viral gp120, when the viruses were passaged in the presence of the antibody. However, when chronically infected MOLT-4 cells were treated with 0.5 beta mAb, recovered viruses from the 0.5 beta-treated cells showed no antigenic changes. The extent of genomic variation among antigenically distinct isolates was examined by nucleotide sequencing, which revealed a few base substitutions in 0.5 beta-binding site of all mutants isolated. The predicted amino acid replacements within 0.5 beta reacting epitope (V3 domain) causing the altered antigenicity were also identified for each of three isolates. Particularly, in one of the mutants, the most conserved Gly-Pro-Gly-Arg region located at the center of the V3 domain was changed to Gly-Gln-Gly-Arg. The radioimmunoprecipitation and synthetic peptide analyses revealed that this Pro320----Gln substitution reduced the binding affinity with 0.5 beta, although other mutations observed in the other mutants did not affect the binding affinity in radioimmunoprecipitation. We also observed that nucleic acid substitutions in the V3 domain occurred frequently in the absence of 0.5 beta mAb during our in vitro acute infection system using MT-4 cells.
Insights
HIV-1 variants resistant to a specific antibody targeting the V3 domain of gp120 were developed. Mutations in the V3 region altered viral antigenicity and antibody binding, particularly a key conserved sequence.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Human Immunodeficiency Virus type 1 (HIV-1) envelope glycoprotein gp120 contains the V3 domain, a critical target for neutralizing antibodies.
- Development of drug resistance is a major challenge in HIV-1 therapy, necessitating understanding of viral evolution under selective pressure.
Purpose of the Study:
- To investigate the emergence and characteristics of HIV-1 antigenic mutants resistant to a specific neutralizing monoclonal antibody (mAb) targeting the V3 domain.
- To analyze the genomic and antigenic changes associated with antibody escape.
Main Methods:
- Isolation of HIV-1 antigenic mutants by passaging plaque-cloned viruses in the presence of mAb 0.5 beta.
- Nucleotide sequencing to identify genomic variations in isolated mutants.
- Radioimmunoprecipitation and synthetic peptide analysis to assess binding affinity and antigenic changes.
Main Results:
- Antigenic HIV-1 mutants resistant to mAb 0.5 beta were successfully isolated.
- Nucleotide sequencing revealed base substitutions within the V3 domain of resistant mutants, affecting the mAb 0.5 beta binding site.
- A specific mutation (Pro320 to Gln) in a conserved V3 region significantly reduced binding affinity to mAb 0.5 beta.
- Other observed mutations did not impact binding affinity in radioimmunoprecipitation assays.
- Frequent nucleic acid substitutions in the V3 domain occurred even without the selective pressure of mAb 0.5 beta in an in vitro system.
Conclusions:
- The V3 domain of HIV-1 gp120 is a key target for antibody-mediated neutralization, and mutations within this region can lead to the emergence of resistant variants.
- Specific amino acid substitutions, particularly in conserved regions like Gly-Pro-Gly-Arg, can significantly alter viral antigenicity and reduce antibody binding affinity.
- Understanding these escape mechanisms is crucial for developing effective HIV-1 vaccines and therapies.