HIV Tropism
HIV coreceptor tropism is defined as the ability of a particular HIV-1 virus to infect a target cell using a specific coreceptor. HIV requires two binding events to enter into a cell. It must first bind to CD4 and then to a chemokine receptor. Tropism is a label given to the virus that describes which chemokine receptor the virus is using.
The HIV-1 viruses can be subdivided into four categories based on the chemokine coreceptor that they use to infect CD4+ lymphocytes:
- R5-tropic viruses use only the CCR5 chemokine coreceptor
- X4-tropic viruses use only the CXCR4 chemokine coreceptor
- Dual D-tropic viruses use either CCR5 or CXCR4 coreceptors
- Mixed M-tropic viruses use various combinations of R5, X4 and dual coreceptors
Current guidelines from the US Department of Health and Human Services (DHHS) and the Infectious Diseases Society of America (IDSA) recommend that coreceptor tropism testing be performed whenever the use of a CCR5 inhibitor is being considered. One such drug, maraviroc, is available for clinical use. Coreceptor tropism testing might also be helpful for patients for patients no longer responding to a CCR5 inhibitor. This testing is available at Monogram Diagnostics (https://www.monogrambio.com/hiv-tests/tropism).
References
- Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. Department of Health and Human Services. Available at https://aidsinfo.nih.gov/contentfiles/lvguidelines/adultandadolescentgl.pdf. Table 3.
- Aberg JA, et al. Primary care guidelines for the management of persons infected with HIV: 2013 update by the HIV Medicine Association of the Infectious Diseases Society of America. Clin Infect Dis 2014;58(1):e1–34.
