Furthermore, our previous study (22) on drug-abused individuals also shows that decreased TLR9 expression and activity caused by drug abuse, accompanied by the decrease of key factors and cytokines (IRF7, IFN-α/β, etc.)of TLR-9 pathway, contribute to HIV infection/replication in macrophages in drug-abused individuals, which is strong evidence for conclusions of the present study. Here, TLR9 is linked to HIV infectious disease.