Abstract
CCR5 and CXCR4 chemokines receptors are critical coreceptors for the binding of HIV to specific host cells. Guidelines recommend its assessment in case of virological failure or before prescription of CCR5 inhibitors. Strategies to assess viral tropism may be divided into phenotypic and genotypic assays; registrative trials of CCR5 inhibitors used phenotypic assay, but recently genotypic ones have been used in clinical practice. The presence of CXCR4 is increasing in naïve patients, with both acute and chronic HIV-1 infections; this coreceptor usage is associated with CD4 depletion. The assessment of viral tropism should be considered in every stage of HIV-1 infection.
Highlights
HIV enters target cells by interacting with specific surface receptors
Guidelines recommend its assessment in case of virological failure or before prescription of CCR5 inhibitors
Strategies to assess viral tropism may be divided into phenotypic and genotypic assays; registrative trials of CCR5 inhibitors used phenotypic assay, but recently genotypic ones have been used in clinical practice
Summary
HIV enters target cells by interacting with specific surface receptors. CCR5 (as discussed by Alkhatib et al [1]) and CXCR4 (as discussed by Feng et al [2]) chemokines receptors are critical coreceptors for the binding of HIV to specific host cells. Most HIV-1 quasispecies infect cells expressing CCR5 and are defined as CCR5or R5-tropic, while a smaller proportion of viruses bind to CXCR4 and are defined as CXCR4- or X4-tropic. Some patients harbour mixed viral populations, and some quasispecies are able to use both coreceptors: those patients are defined as carrying dual/mixed viruses (DM-tropic) (as discussed by Berger et al [3]). A CCR5 inhibitor, is the only antiretroviral agent targeting coreceptor binding currently licensed for use in HIV infection. Several techniques were developed to assess HIV tropism, and treatment guidelines from different countries are not uniform in defining which methods should be employed in clinical practice
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