A coreceptor tropism test determines whether a patient exclusively harbors R5-tropic virus or has X4-tropic or D/M virus. Patients who exclusively harbor R5-tropic virus can be treated with CCR5 antagonists such as maraviroc (Selzentry®). CCR5 antagonists block R5 viruses from binding to the CCR5 coreceptor and infecting cells. CCR5 antagonists are ineffective in patients with X4 or D/M virus. Thus, coreceptor tropism testing can help determine patient eligibility for CCR5 antagonist therapy.
A coreceptor tropism test should be performed when the use of a CCR5 antagonist is being considered.3,4 Coreceptor tropism testing might also be considered for patients who exhibit virologic failure while taking a CCR5 inhibitor.3,4 See also Question 6.