More than a decade ago, researchers found that AHR activation stimulated by ligand of TCDD or by TCDD chemical homologue 3-methylcholanthrene 3-MC was shown to reactivate HIV-1 from latency [68, 69]. In recent years, through further exploration, researchers demonstrated that AHR was activated by Trp metabolites to promote HIV-1 infection and reactivation [70]. The gene discussed is AHR; the disease is HIV-1 infection.