| |
Green tea shows promise in HIV fight
|
| |
| |
Part of drink blocks access to immune system's cells, study finds
By LEIGH HOPPER
2006 Houston Chronicle
Chalk up another one for green tea.
In test-tube experiments, a component of the ubiquitous health beverage blocks the ability of the AIDS virus to hijack and destroy immune-system cells, scientists from Houston and the United Kingdom say.
Green tea's benefits stem from a substance called epigallocatechin gallate, or EGCG. EGCG is a flavonoid, a compound that gives green tea its color, and has anti-cancer, anti-microbial and anti-inflammatory properties. EGCG-based cancer drugs already are in clinical trials.
It also holds some promise in fighting HIV - though nobody's recommending it yet for AIDS prevention or treatment.
Understanding why
For at least a decade, researchers have known the EGCG molecule inhibits the progression of HIV in lab experiments - but they didn't understand precisely why.
Now, work by Baylor College of Medicine and University of Sheffield, UK, scientists shows how the EGCG molecule binds to the exact spot HIV needs to infect a healthy T-cell, a type of white blood cell critical to fighting infections. Their report is online in the Journal of Allergy and Clinical Immunology.
Under normal circumstances, HIV does its dirty work via an "envelope" or surface protein called gp120, which locks into a special "pocket" on the surface of susceptible host cells called CD4 T-cells. After that fusion, HIV releases its genetic material into the healthy cell. The infected cell then begins churning out the next generation of viruses.
But not if the green tea-derived molecule plugs up that pocket, leaving HIV no way to get inside.
Baylor pediatrics instructor Dr. Christina Nance, research supervisor for allergy and immunology at Texas Children's Hospital, said she and her colleagues used a fairly new approach involving nuclear magnetic resonance spectroscopy. That method allowed them to "see" structures by which EGCG, gp120 and CD4 molecules bind together. Participating in the research were Dr. Theron McCormick and Dr. William Shearer from Baylor, and Mike Williamson of the University of Sheffield.
Using spectroscopy, Nance and her colleagues observed the frequencies emitted by the hydrogen, carbon and nitrogen atoms that make up the molecules they are studying. They paired the CD4 molecule with the HIV surface protein gp120, then paired the CD4 molecule with green tea's EGCG.
Frequency data fed into a computer produced a molecular model showing EGCG and HIV shared the same "binding pocket" on the CD4 T-cell.
"One of the promising factors is, that because this is a small molecule and binds to the same exact binding pocket as (HIV's) gp120, it may not inhibit the (normal) function of the CD4 molecule," Nance said.
Like two cups a day
Nance found the amount of EGCG needed to inhibit HIV progression in the laboratory was the equivalent of the amount achieved by drinking two cups of green tea.
Much more research is needed to move Nance's observation toward drug development.
In the meantime, Nance doesn't recommend that people chug large quantities of green tea in hopes of preventing infection with HIV.
"It would be part of a cocktail of drugs," Nance said. Current HIV treatment consists of multiple drugs, or "cocktails" that block different parts of the virus's life cycle.
|
|
| |
| |
|
|
|
