Determination of HIV tropism and its use in the clinical practice.

Assessment of HIV coreceptor tropism assay is recommended before starting therapy with CCR5 coreceptor antagonists. So far, only maraviroc (MVC) has been approved for clinical use and a tropism assay is mandatory for patients with virological failure or patients in which MVC is considered into future treatment options. Viral tropism can be assessed with either genotypic or phenotypic methods and to this aim different techniques have been developed. However, it is unclear which assay is more appropriate for routine testing. In fact, although phenotypic assays are considered the gold standard as they directly measure the viral tropism and current versions allow detection of a lower threshold of minor CXCR4-dependent variants, the genotypic assays present major practical advantages for their use in the clinical setting.