Imperial Collage Healthcare

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HIV-1 Tropism testing

Test Background

An important subclass of drugs used in patients with HIV-1 infection have been designed to inhibit HIV-1 viral entry. These entry inhibitors are drugs which target one of the receptors that can be used (in addition to the main receptor CD4 by HIV-1), as a coreceptor to enter the cell. The most important HIV coreceptors are the chemokine receptors CCR5 and CXCR4. HIV-1 particles fall into three classes according to which of them they can use to enter a cell: some can only use CCR5, others can only use CXCR4, and some can use either of them. Before and during drug treatment with a coreceptor antagonist, it is important to find out about the coreceptor usage of the virus population in the patient.

The amino acid sequence of the V3 loop can be determined by RT-PCR of isolated RNA extracted from plasma samples and analysed using the Trugene software. The sequence can be inserted into the Geno2pheno software and the coreceptor usage predicted directly from the sequence.

Clinical Indications

Baseline and/or when failing therapy

Reference Range
Contact Laboratory

Sample Required
EDTA whole blood

Sample Volume

Turnaround Time
14 days


Must have quantifiable HIV-1 viral load.
Sequencing previously performed externally now done in-house

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