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Updated: Aug 8, 2026
Conformational Evaluation of HIV-1 Trimeric Envelope Glycoproteins Using a Cell-based ELISA Assay
Published on: September 14, 2014
A simple method for improved assay demonstrates that HIV p24 antigen is present as immune complexes in most sera from
P Nishanian1, K R Huskins, S Stehn
1Center for Interdisciplinary Research in Immunology and Disease, UCLA 90024.
Insights
A new pH pretreatment method significantly improves human immunodeficiency virus (HIV) p24 antigen detection in patient sera. This enhanced assay reveals higher antigen positivity and levels, crucial for understanding HIV infection dynamics.
Area of Science:
- Virology
- Immunology
- Clinical Diagnostics
Background:
- Human immunodeficiency virus (HIV) p24 antigen is a key marker for viral load and infection stage.
- Detection of p24 antigen is often hindered by its presence in immune complexes within patient sera.
- Conventional enzyme-linked immunosorbent assays (ELISA) have limitations in detecting complexed p24 antigen.
Purpose of the Study:
- To enhance the detection and quantitation of HIV p24 antigen in sera.
- To investigate the impact of a low pH pretreatment on p24 antigen assay performance.
- To characterize p24 antigen expression patterns in seroconverting individuals.
Main Methods:
- Samples were pretreated at pH 2.5-3.0 to dissociate immune complexes.
- Standard HIV p24 antigen ELISA was performed on pretreated and conventional samples.
- A longitudinal study tracked p24 antigen levels in 29 seroconverters over one year.
Main Results:
- Pretreatment significantly increased antigen positivity from 12.4% to 50.6% in 652 HIV-positive sera.
- Pretreatment also enhanced the measured levels of p24 antigen in sera.
- Longitudinal data revealed persistent (58.6%), absent (34.5%), or episodic (6.9%) p24 antigen expression.
Conclusions:
- Low pH pretreatment effectively liberates p24 antigen from immune complexes, improving assay sensitivity.
- The majority of HIV-infected individuals exhibit persistent or absent serum p24 antigen, not episodic.
- This improved assay offers a more accurate method for monitoring HIV infection and viral dynamics.
Abstract:
Improved detection and quantitation of p24 antigen of the human immunodeficiency virus (HIV) in sera was obtained by pH 2.5-3.0 pretreatment of samples before using a standard HIV p24 antigen ELISA. Pretreatment dissociated immune complexes and denatured antibodies with little or no compromise of p24 antigen immunoreactivity. For 652 HIV antibody-positive sera, direct comparison of the pretreatment with the conventional assay demonstrated substantial increase in both antigen positivity (50.6% vs. 12.4%) and in the level of p24 antigen in sera. Serum HIV antigen is mainly in the form of immune complexes in most individuals at all stages of HIV infection. Longitudinal study of 1 year (three measurements) on 29 seroconverters demonstrated two main patterns of p24 antigen expression in sera: 34.5% of infected individuals never express any form of detectable HIV antigen and 58.6% persistently demonstrate serum p24 antigen, usually in complex with antibody. Only 6.9% show episodic p24 antigen positivity.
