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Updated: Jun 17, 2026
Prediction of HIV-1 Coreceptor Usage (Tropism) by Sequence Analysis using a Genotypic Approach
Published on: December 1, 2011
Development and performance of a new recombinant virus phenotypic entry assay to determine HIV-1 coreceptor usage
Stéphanie Raymond1, Pierre Delobel, Maud Mavigner
1INSERM, U563, Toulouse, F-31300, France.
Background:
Clinical trials of CCR5 antagonists have relied on the phenotypic determination of HIV-1 coreceptor usage. Few phenotypic assays are available, with few data on their concordance, and none has been designed to determine tropism from cell-associated HIV-1 DNA.
Objectives:
To assess the performance of the new Toulouse Tropism Test (TTT) phenotypic assay to characterize HIV-1 tropism using blood plasma and peripheral blood mononuclear cells (PBMC).
Study Design:
434 plasma and 168 PBMC samples were tested with the TTT assay. We determined the correlation between our assay results on plasma samples and those of the commercial Trofile assay.
Results:
The TTT assay determined the tropism of 97% of samples after successful amplification of the env gene. It performed well on both cell samples and plasma samples with various HIV-1 loads and subtypes. It detected 0.5% of minor CXCR4-using variants in the virus population. The TTT and the Trofile assays were >90% concordant for predicting HIV-1 tropism.
Conclusion:
We have validated a new recombinant virus phenotypic assay for determining HIV-1 tropism using both plasma and cell samples from patients who are candidates for treatment with CCR5 antagonists.
Insights
A new Toulouse Tropism Test (TTT) accurately determines HIV-1 tropism from plasma and cell samples. This phenotypic assay shows high concordance with existing methods, aiding CCR5 antagonist treatment decisions.
Area of Science:
- Virology
- Immunology
- Clinical Diagnostics
Background:
- Phenotypic determination of HIV-1 coreceptor usage is crucial for CCR5 antagonist therapy.
- Limited availability and concordance data exist for current phenotypic tropism assays.
- No assays are designed to determine tropism from cell-associated HIV-1 DNA.
Purpose of the Study:
- To evaluate the performance of the novel Toulouse Tropism Test (TTT) phenotypic assay.
- To characterize HIV-1 tropism in both plasma and peripheral blood mononuclear cells (PBMCs).
Main Methods:
- The TTT assay was used to test 434 plasma and 168 PBMC samples.
- Correlation between TTT plasma results and the commercial Trofile assay was assessed.
Main Results:
- The TTT assay successfully determined tropism in 97% of samples with env gene amplification.
- The assay demonstrated robust performance across various HIV-1 loads and subtypes in both plasma and cell samples.
- High concordance (>90%) was observed between the TTT and Trofile assays for predicting HIV-1 tropism.
- Minor CXCR4-using variants were detected in 0.5% of the virus population.
Conclusions:
- A new recombinant virus phenotypic assay, the TTT, has been validated for HIV-1 tropism determination.
- The TTT assay is effective for both plasma and cell samples from patients considered for CCR5 antagonist treatment.
