Tropism by Genotype

To predict viral co-receptor tropism The HIV-1 virus enters cells via binding to two receptors: the CD4 receptor and a co-receptor. HIV-1 co-receptors include the chemokine receptors CCR5 (R5) and CXCR4 (X4). Some HIV-1 viruses can only use CCR5 (R5), others can only use CXCR4 (X4), and some can use either of them.

Several anti-HIV-1 co-receptor antagonists that prevent the viral entry into the cell by blocking the co-receptor are in the pipeline. One such drug, Maraviroc (Celsentri® or Selzentry®, Pfizer), which targets the CCR5 (R5) receptor has already been approved. Before and during drug treatment with a co-receptor antagonist it is important to determine which co-receptors are used by the patient’s HIV-1 virus(es).

HIV-1 Tropism by Genotype gives a prediction of the co-receptor used by the patient’s HIV-1 virus. The prediction is created by the geno2pheno algorithm (Sing et al, 2007) (Max Planck Institute) based on the HIV-1 gp120 V3 genotype.

Lab 21 provides both RNA and DNA-based analysis:

  1. RNA analysis (plasma) when HIV-1 Viral Load is >500 cp/ml
  2. Pro-Viral DNA analysis (whole blood) when HIV-1 Viral Load is <500 cp/ml

HIV-1 Tropism by Genotype can be easily combined with HIV-1 Drug Resistance testing. Lab 21 is committed to providing the highest quality services to our customers, and test turnaround time is only 14 working days from the receipt of sample at Lab 21.

Find out more

Please contact us to discuss your needs with our clinical team.

Provided under our UKAS accreditation.

Please see our Accreditation page for full scope of accredited testing.


Sing T et al. Predicting HIV co-receptor usage based on genetic and clinical covariates. Antivir Ther, 2007; 12(7):1097-106.