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Green Tea Compound in a Microbicide May Help Prevent HIV Entry into Cells

Since the start of the AIDS epidemic, researchers have sought women-controlled HIV prevention methods such as microbicide gels to reduce the risk of infection during sex. A wide variety of natural and manufactured chemicals have been tested as potential microbicides. Now, scientists report that a compound in green tea may help prevent HIV from attacking cells via semen.

Ilona Hauber from the University of Heidelberg in Germany and colleagues conducted a study to determine whether the major active component of green tea, known as epigallocatechin-3-gallate (EGCG), would inhibit HIV infection of new cells. Results were published in the June 2, 2009 Proceedings of the National Academy of Sciences USA.

Peptide fragments derived from prostatic acidic phosphatase (an enzyme produced by the prostate gland) are released in human semen, where they form amyloid fibrils or fibers, the researchers explained. These structures -- called semen-derived enhancer of virus infection, or SEVI -- capture HIV virus particles and direct them to target cells. Thus, the authors wrote, "SEVI appears to be an important infectivity factor of HIV during sexual transmission."

In a laboratory study, the researchers showed that EGCG degrades SEVI fibers and prevents new ones from forming. By doing so, the green tea polyphenol inhibits SEVI activity and stops it from transporting HIV to cells. Because EGCG does not disrupt host cells, it appears to have little or no cellular toxicity.

Based on these findings, the study authors concluded, "EGCG appears to be a promising supplement to antiretroviral microbicides to reduce sexual transmission of HIV-1."

Real world use of a green tea-based microbicide is years in the future. Promising compounds must first be formulated into a gel, cream, or similar product that can be inserted in the vagina, tested for safety in a small number of women, and then tested for efficacy in trials with large numbers of participants. An effective microbicide could potentially also be suitable for rectal use to prevent HIV transmission during anal sex, but would require additional testing to ensure that it does not harm the more delicate rectal lining.

Heinrich-Pette-Institute for Experimental Virology and Immunology, Hamburg, Germany; University of Heidelberg, Heidelberg, Germany

6/16/09

Reference

I Hauber, H Hohenberg, B Holstermann, and others. The main green tea polyphenol epigallocatechin-3-gallate counteracts semen-mediated enhancement of HIV infection. Proceedings of the National Academy of Sciences USA 106(22): 9033-9038. June 2, 2009.