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Green tea: fact or fiction.

Scientists have discovered that a substance in green tea prevents HIV from attaching to our immune system cells by getting there first. According to researchers from Baylor College of Medicine in Houston and the University of Sheffield in the England, in a report that appears in the Journal of Allergy and Clinical Immunology (1), a compound in green tea called catechin, (also known as epigallocatechin gallate [EGCG] or flavonoid) blocks the ability of HIV to enter and destroy the immune system.

The health effects of brewed green tea are attributed to numerous chemical substances that make up 30% of dried leaf extract. Of these, EGCG is the most active. Similar substances in other plants have been found to be less plentiful and have fewer medicinal properties. EGCG binds well to many molecules and affects a variety of enzyme. It is this specific aspect of green tea that researchers think is responsible for its many reported health benefits.

Animal studies have shown that drinking green tea is associated with a lower rate of cancer in humans. The major component of green tea, EGCG, is thought to be the most potent cancer-preventive component of the catechins. This protective effect of green tea has been evaluated in pancreatic, colon, rectal, skin, breast, prostate, liver, and lung cancel: Recently EGCG has emerged as a potential candidate in the fight against AIDS. Investigators have found that its antiviral effects can be targeted at HIV infection. However, this does not mean you should start drinking gallons of green tea every day. But, there is some encouraging news.

HIV infection results in damage to the immune system when the gpl20 glycoprotein (a protein that has sugar molecules attached to it) latches onto the T cell. Even though gpl20 produces antibodies that help light against the virus, HIV manages to escape, leading to infection. Ever since the discovery of the virus as the cause of AIDS, there has been an intense effort to develop methods to slow down or prevent HIV infection. Until now, scientists have spent much of their time trying to find ways to build up the immune system to prevent HIV from attaching itself to the T cells. Christina L. Nance, PhD, and William T. Shearer, MD, PhD, of Baylor College of Medicine and Texas Children's Hospital, and Mike R Williamson, PhD, of the University of Sheffield, began looking at ways to get high enough levels of EGCG into the body for it to be able to protect the body against HIV. They paired the T cell with gpl20, then paired the T cell with EGCG. By studying the physical structure of the T cell, they realized that EGCG hooks onto the same exact pocket on the T cell as gp 120. This ability to block gp 120 is its most important feature since it prevents the initial encounter of HIV with T cells.

If EGCG proves to have value as an HIV treatment, it probably will not be used alone. It would be part of a combination of drugs. The researchers do not recommend that people drink large quantities of green tea with the expectation that it will prevent infection with HIV. These studies are designed to determine whether a drug derived from green tea would have that effect. The next phase of the research will be testing EGCGin humans.

(1) Journal of Allergy and Clinical Immunology 118(6): 1369-74, Dec 2006.

Christina L. Nance, PhD, is Instructor and Research Laboratory Supervisor at Baylor College of Medicine, Department of Allergy/Immunology, Texas Children's Hospital.
COPYRIGHT 2007 The Center for AIDS: Hope & Remembrance Project
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2007 Gale, Cengage Learning. All rights reserved.

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Title Annotation:treatment news
Author:Nance, Christina L.
Publication:HIV Treatment: ALERTS!
Date:Jun 1, 2007
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