A new cell line-based neutralization assay for primary HIV type 1 isolates.

Area of Science:

• Virology
• Immunology
• Assay Development

Background:

• Standardized assays are crucial for HIV-1 vaccine and pathogenesis research.
• Existing peripheral blood mononuclear cell-based assays have limitations.
• A need exists for reliable detection and quantification of neutralizing antibodies to primary HIV-1 isolates.

Purpose of the Study:

• To develop and validate a novel HIV-1 neutralization assay.
• To establish a plaque formation-based method using U87.CD4 cell lines.
• To provide a high-throughput, reproducible assay for HIV-1 neutralization studies.

Main Methods:

• Utilized U87.CD4-CCR5 and U87.CD4-CXCR4 cell lines for HIV-1 plaque formation.
• Infected cells formed syncytia (plaques) stained with hematoxylin and enumerated via microscopy.
• Neutralization determined by serum's ability to reduce plaque-forming units (PFU) compared to controls.
• Established assay parameters including virus dose (10-100 PFU/well) and neutralization cutoff (30% plaque reduction).

Main Results:

• Demonstrated good intra-assay reproducibility with a standard deviation of +/- 9.1% for PFU determinations.
• Achieved high reproducibility across different days, with a mean difference of 11% in neutralization results.
• Confirmed assay specificity, with no positive neutralization signals from HIV-1-uninfected subjects' samples.
• Established a neutralization cutoff of 30% plaque reduction, corresponding to 3.3 standard deviations.

Conclusions:

• The U87.CD4 cell line-based assay is a highly reproducible and sensitive method for HIV-1 neutralization.
• This assay is suitable for large-scale HIV-1 neutralization studies and serves as an attractive alternative to PBMC-based assays.
• The assay facilitates accurate detection and quantification of neutralizing antibodies against primary HIV-1 isolates.