Green Tea Shows Promise in HIV Fight

In a new study, scientists report that test-tube experiments show a component in green tea blocks the ability of HIV to invade and destroy cells of the immune system.

That component is epigallocatechin gallate (EGCG). The flavonoid has anti-inflammatory and anti-microbial properties, and cancer drugs based on it are now in clinical trials.

Researchers have known for some time that EGCG inhibits HIV in lab experiments; the new research suggests how. Scientists from Baylor College of Medicine and the University of Sheffield have found that the EGCG molecule binds to the T-cell receptor site at which HIV seeks to attach to the cell.

Dr. Christina Nance of Baylor and Texas Children's Hospital said she and colleagues used nuclear magnetic resonance spectroscopy to examine the structures by which EGCG, the HIV surface protein gp120 and CD4 molecules bind together. They noted the frequencies emitted by the hydrogen, carbon and nitrogen atoms that make up the molecules and fed the data into a computer, which produced a molecular model showing that EGCG and HIV shared the same "binding pocket" on the CD4 cells. "One of the promising factors is that because this is a small molecule and binds to the same exact binding pocket as gp120, it may not inhibit the [normal] function of the CD4 molecule," Nance said.

In the laboratory, Nance said the amount of EGCG needed to inhibit HIV was about the same as that in two cups of green tea. She stressed, however, that any EGCG-based drug "would be part of a cocktail of drugs," and she said she does not recommend that people drink large amounts of green tea in the hope of preventing HIV infection.

The full report, "Epigallocatechin Gallate, the Main Polyphenol in Green Tea, Binds to the T-Cell Receptor, CD4: Potential for HIV-1 Therapy," was published online in the Journal of Allergy and Clinical Immunology (doi: 10.1016/j.jaci.2006.08.016).