Study Shows Green Tea's Potential Against HIV

TOKYO--Epigallocatechin gallate (EGCG), the primary antioxidant polyphenol found in green tea, may have potential against HIV infection, according to a study published in the November issue of The Journal of Allergy and Clinical Immunology (112, 5:951-7, 2003) (www.mosby.com/jaci). Researchers from the University of Tokyo reported EGCG prevents HIV from binding to T-helper cells--immune cells that target antigens by secreting proteins called cytokines to activate T cells and B cells, which then seek out and destroy the antigen. HIV is known to attack T-helper cells (also known as CD4 cells), which effectively prevents the immune system from protecting the body against infection.

To investigate the effects of EGCG on HIV infection, researchers incubated peripheral blood CD4 T cells with EGCG. The polyphenol was seen to directly bind to CD4 cells, thereby preventing an HIV envelope protein (called gp120) from binding to the CD4 receptors. EGCG also prevented the anti-CD4 antibody from binding to its corresponding antigen, leading researchers to conclude EGCG modulates binding to CD4, thereby protecting against HIV infection.

Even though gp120 elicits antibodies to HIV, the virus is still able to elude the human immune system, according to Christina L. Nance, M.S., of the Houston-based Texas Children's Hospital, and William T. Shearer, M.D., Ph.D., of the Baylor College of Medicine in Houston, who published an accompanying editorial in The Journal of Allergy and Clinical Immunology (112, 5:851-3, 2003). HIV infection depends on a sequential interaction between gp120 and receptors on CD4 cells, according to Nance and Shearer. They added the recent study showed EGCG prevents the HIV protein from attaching to CD4 molecules and down-regulates cell surface expression of CD4 by binding itself to the molecule.

Nance and Shearer noted the effects observed in this study would potentially require developing a "capsular alternative to green tea or EGCG" in order to attain physiologically relevant EGCG concentrations in the body. "This provocative investigation raises again the question of using natural products in the treatments of serious disease," they concluded. "By no means should the findings of this study ... be seen as an endorsement of the consumption of green tea (gallons of it, presumably) to counter HIV-1 infection, or, worse, as an alternative therapy to the wonderful life-restoring antiretroviral agents that we now have. ... Nevertheless, it is not improbable that green tea or its extracts will be involved in the future treatment of HIV-1 infection."