Too Soon to Know if Green Tea Will Do the Same in People
May 25, 2006 -- An antioxidant in green tea may block HIV, the virus that causes AIDS, from attaching to an important molecule on immune system cells.

That finding is based on lab tests done on human blood cells, not people. The lab tests were done by Christina Nance, PhD, and colleagues. Nance works in Houston, at Texas Children's Hospital and Baylor College of Medicine.

In a nutshell, Nance's team wanted to see if epigallocatechin gallate (EGCG), a chemical found in green tea, might block HIV from attaching to the immune system's T-helper cells, thus protecting those T cells from HIV's damage. T-helper cells act as a "general" in directing and activating other immune cells in the fight against HIV.

The results show that EGCG might indeed help do that. It's not yet clear if the findings will have meaning beyond the lab. HIV has proven to be crafty against many different attempts to thwart it from latching onto immune system cells.

The test results were presented in Canada at the North American Research Conference on Complementary & Alternative Medicine, held in Edmonton, Alberta, Canada.

Lab Tests

Nance's team treated some human T cells with three doses of EGCG. For comparison, they didn't expose other T cells to EGCG.

Then they added an HIV component called gp120 to the T cells. The goal was to see if EGCG thwarted gp120 from binding to a certain molecule -- the CD4 molecule -- on T-helper cells.

When gp120 latches onto a T cell's CD4 molecule, it paves the way for HIV to enter -- and eventually disable and kill -- the T cell.

EGCG "markedly inhibited" gp120 from binding to the T cells' CD4 molecules, write Nance and colleagues. The highest EGCG dose had the strongest effect. The lowest dose had the mildest effect. The medium dose had a medium-sized effect.

However, none of the EGCG doses totally blocked gp120 from binding to the CD4 molecule, the study shows.

This isn't the first time that EGCG has been studied in HIV. In 1989, Japanese researchers reported that EGCG may help block an enzyme called reverse transcriptase that slips HIV's genetic material into the host cell's DNA.