CD4 and hepatitis C virus infection: Various factors have been shown to be associated with suboptimal CD4+ cell count recovery, including low nadir/baseline CD4+ cell count, old age, male gender, prolonged duration between HIV-1 infection and the initiation of ART, hepatitis C virus infection, hepatitis B virus infection, comorbidities, injection drug use, up-regulation of surface markers of lymphocyte activation, and gene polymorphisms of IL-10 and IL7RA [18–37].