Epigallocatechin-3-gallate Prevents Simian/Human Immunodeficiency Virus Sexual Transmission

HIV infection is characterized by gradual CD4+ T cells depletion and immune cell dysfunction, which are driven by chronic immune activation, a process characterized by high T cell turnover, B cell and T cell activation, and increase levels of proinflammatory molecules. Chronic immune stimulation most likely creates a permissive environment for further HIV replication, while temporarily allowing successful replenishment of the T-cell pool but ultimately leading to CD4+ T cell exhaustion. While the antiretroviral therapy (ART) is able to reduce the viral load to extremely low levels and reduce HIV-driven immune activation, ART does not warrant elimination of HIV and immune activation entirely, which leads to continued immunological degradation and incomplete functional restoration of the immune system. In addition, the use of antiretroviral drugs has been associated with several toxicities that limit their success and render patients to quit the therapy, which also increases the occurrence of drug-resistance. As the mechanisms which underlie chronic immune activation during HIV infection are multifaceted and complex, suppression of the HIV replication only is not sufficient to maintain a long-term systemic homeostasis of the immune system. Therefore, to intervene chronic immune activation with herbal medicines should illuminate therapeutic options to improve outcomes from HIV-infected individuals. Among the herbal medicines that have benefits for treating HIV infection and AIDS, epigallocatechin gallate (EGCG) is an ideal candidate. As the most abundant catechin in green tea, EGCG is a potent antioxidant and has therapeutic applications in the treatment of many disorders, including HIV infection. Accumulating in vitro studies revealed that EGCG has extensively anti-viral effects on kinds of enveloped virus, as well as HIV. Nevertheless, to date, there is lack of a systemic evaluation, particularly in vivo studies to determine the effect of EGCG on HIV prevention and treatment. We propose an EGCG-based immunologic therapy for HIV disease, utilizing the established SIV infected Chinese rhesus macaque. The proposed project is comprised of in vitro and ex vivo cell models (primary cells), and in vivo animal studies (rhesus macaques). With such a systemic study we should be able to generate significant and valuable information regarding the effectiveness of EGCG on HIV prevention and treatment. A better understanding of the preventive and therapeutic potential of EGCG would illuminate a new therapeutic approach to control HIV transmission and improve the life quality of HIV-infected patients.1. Chronic immune activation in HIV/SIV infectionChronic immune activation is a hallmark of progressive HIV infection and the major factor of disease progression. To further confirm the similarity of SIV infected Chinese rhesus macaques and HIV infected subjects, we determined the lavel of immune activation in SIV chronic infected macaques. Severe CD4+ T cells depletion was found in both peripheral and gut associated lymphocyte tissues, and T cells exhaustion in IELs of intestine and colon, which was consistent with HIV infection. Extensively immune activation (CD69+ and HLA-DR) of CD8+ T cells, as well as proliferation, in the three types of lymphoid tissues in SIV infected macaques, as compared with that in uninfected macaques. In addition, SIV infected Chinese macaques live as long as 3 or 4 years with asymptomatic infection, suggested to be a more suitable model for HIV infection in human.2. EGCG suppresses inflammation and chronic immune activationMicrobial translocation has been substantially implicated to play a critical role in chronic immune activation and HIV disease progression. Bacterial lipopolysaccharide (LPS) in the circulation has been postulated a HIV-related systemic inflammation and immune activation. In light of the anti-oxidative and anti-inflammatory effects of EGCG, we next detected whether EGCG could inhibit LPS induced inflammation and immune activation in both HIV targeted cells and bystander cell. EGCG dramatically inhibits LPS induced inflammatory cytokines and ROS. In vivo study revealed that EGCG could significantly downregulate LPS induced inflammation in rats, and inhibit the expression of cytokines in PBMCs of SIV-infected macaques with daily oral administration of EGCG upto eight weeks.3. EGCG prevents SIV/SHIV mucosal transmissionIn view of the in vitro studies of anti-inflammation, we next examined the anti-HIV effects of EGCG with in vitro and in vivo studies. EGCG was the most potent inhibitor of 6 strain of viruses, including HIV-1, SHIV and SIV. In addition, EGCG dose-dependently inhibited HIV-1bai replication in primary macrophages and TNF-?, IL-1? and MCP-1 expression in HIV-lbai-infected macrophages. Furthermore, EGCG could inhibit SHIV infection of primary lymphocytes and macrophages of rhesus macaques. We first challenged rhesus macaques with different strains via intravenous injection, intravaginal or intrarectal exposure. Plasma viral loads reached to the peak level two or three weeks postinfection and then declined to a stable level, although fluctuated during the course of infection. The CD4+ T cells in whole blood had a?50% drop at the early stage of infection and subsequently recovered to a mediate level that was still lower than the original ones, following up a long phase of chronic infection, which is similar to HIV infected individuals. Based on all these studies, we next examined the protective efficiency of EGCG on SHIV intrarectal challenge. We demonstrated that the intrarectal administration of EGCG could protect rhesus macaques from repetitive, intrarectal challenges with low-dose SHIVSF162P3N. All protected animals showed no evidence of systemic and mucosal SHIV infections as demonstrated by the absence of viral RNA, DNA and antibodies. In contrast, all controls became infected after repeated SHIV challenges (a median of 2.5 times, range of 1-8 times). Statistically, the EGCG treatment afforded a protective efficacy of 91.5% [1 (hazard ratio), P=0.0009, log-rank test] reduction in the per-exposure acquisition risk as compared with control. The complete protection for animals in the EGCG group was 87.5% (P=0.001, Fisher's exact test). The critical mechanisms of the EGCG-mediated prevention of intrarectal SHIV transmission are its competition with gp120 for CD4 receptor binding and the suppression of macrophage infiltration and activation in the rectal mucosa.