In this study, we found CMV, VZV and HSV-2 IgG levels to positively correlate with K/T ratio which remained significant even after excluding participants with chronic hepatitis B and C co-infections (data not shown) implying that HHV was an important and persistent modulator of the IDO pathway in participants receiving long-term suppressive antiretroviral therapy. The gene discussed is IDO1; the disease is chronic hepatitis B virus infection.