Tea Time Down Under: HIV
Abstract & Commentary
By Russell H. Greenfield, MD, Editor
Synopsis: In-depth laboratory analysis suggests that human semen (SE) contains a peptide that enhances HIV infectivity, but the green tea polyphenol epigallocatechin-3-gallate (EGCG) inhibits the increased infectivity associated with the peptide. This raises the possibility that topical intravaginal EGCG could be a useful adjunct in controlling the spread of HIV infection.
Source: Hauber I, et al. The main green tea polyphenol epigallocatechin-3-gallate counteracts semen-mediated enhancement of HIV infection. PNAS 2009;106:9033-9038.
The authors of this laboratory study focused on the possibility that green tea may contain constituents that reduce infectivity of the HIV virus. Prior study had shown that a peptide derived from prostatic acid phosphatase and present in high concentrations within SE enhanced HIV infectivity, apparently by creating amyloid fibrils (called semen-derived enhancer of virus infection, or SEVI). In a dose-dependent fashion, EGCG was first shown to interfere with amyloid fibrillogenesis, and a subsequent lab study showed that EGCG helped to trigger the degradation of pre-formed amyloid fibrils. In another test, the researchers employed ultrathin sectioning together with electron microscopy and found that incubation of SEVI fibrils with EGCG resulted in no damage to the fibrils after 12 hours, but extensive fibrillar degradation at 60 hours. Interestingly, EGCG exhibited little in the way of antiviral activity in the absence of SEVI. EGCG showed no untoward effects on uninfected cells. The authors conclude that EGCG targets and degrades the SEVI amyloid fibrils, thus interfering with otherwise enhanced HIV infectivity, and without toxic effects on healthy, non-infected cells.
The authors draw on prior data to show that SEVI may be an important HIV infectivity factor during sexual transmission, share new data suggesting a role for EGCG in counteracting the enhanced infectivity induced by SEVI fibrils, and suggest that the polyphenol may be an effective and inexpensive intravaginal adjunct to more standard microbicidal therapy. Previous studies have suggested a possible role for ingested green tea to help control the spread of HIV infection, but this is perhaps the first study to explore such a role for a topical green tea EGCG extract. The researchers point out that EGCG is acid-stable, and thus should be stable in the intravaginal environment.
Around the world, infection with HIV most commonly occurs through sexual transmission. Current estimates are that 33 million people are infected with HIV, many of them poor. Imaginea relatively benign and cheap intervention, developed from a readily available source (green tea), helping to lessen the infectivity of the HIV virus. Is more study needed? Yes, as the series of tests reported here were all bench research, the results compel scientists to look at EGCG's potential effects in humans in an ethically sound manner. Though the mechanism by which EGCG interferes with SEVI fibrils is yet unknown, the results of this study are exciting since, as with most illness, any advance in primary prevention trumps advances in treatment of established disease.