Study Shows Green Tea's Potential Against HIV 29482

Study Shows Green Tea's Potential Against HIV

TOKYO--Epigallocatechin gallate (EGCG), the primaryantioxidant polyphenol found in green tea, may have potential against HIVinfection, according to a study published in the November issue of The Journalof Allergy and Clinical Immunology (112, 5:951-7, 2003) (www.mosby.com/jaci).Researchers from the University of Tokyo reported EGCG prevents HIV from bindingto T-helper cells--immune cells that target antigens by secreting proteinscalled cytokines to activate T cells and B cells, which then seek out anddestroy the antigen. HIV is known to attack T-helper cells (also known as CD4cells), which effectively prevents the immune system from protecting the bodyagainst infection.

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

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

Nance and Shearer noted the effects observed in this study would potentiallyrequire developing a "capsular alternative to green tea or EGCG" inorder to attain physiologically relevant EGCG concentrations in the body."This provocative investigation raises again the question of using naturalproducts in the treatments of serious disease," they concluded. "By nomeans should the findings of this study ... be seen as an endorsement of theconsumption of green tea (gallons of it, presumably) to counter HIV-1 infection,or, worse, as an alternative therapy to the wonderful life-restoringantiretroviral agents that we now have. ... Nevertheless, it is not improbablethat green tea or its extracts will be involved in the future treatment of HIV-1infection."