Gallic Acid Is an Antagonist of Semen Amyloid Fibrils That Enhance HIV-1 Infection

Abstract

Recent in vitro studies have demonstrated that amyloid fibrils found in semen from healthy and HIV-infected men, as well as semen itself, can markedly enhance HIV infection rates. Semen fibrils are made up of multiple naturally occurring peptide fragments derived from semen. The best characterized of these fibrils are SEVI (semen-derived enhancer of viral infection), made up of residues 248 -286 of prostatic acidic phosphatase, and the SEM1 fibrils, made up of residues 86 -107 of semenogelin 1. A small molecule screen for antagonists of semen fibrils identified four compounds that lowered semen-mediated enhancement of HIV-1 infectivity. One of the four, gallic acid, was previously reported to antagonize other amyloids and to exert anti-inflammatory effects. To better understand the mechanism by which gallic acid modifies the properties of semen amyloids, we performed biophysical measurements (atomic force microscopy, electron microscopy, confocal microscopy, thioflavin T and Congo Red fluorescence assays, zeta potential measurements) and quantitative assays on the effects of gallic acid on semen-mediated enhancement of HIV infection and inflammation. Our results demonstrate that gallic acid binds to both SEVI and SEM1 fibrils and modifies their surface electrostatics to render them less cationic. In addition, gallic acid decreased semen-mediated enhancement of HIV infection but did not decrease the inflammatory response induced by semen. Together, these observations identify gallic acid as a non-polyanionic compound that inhibits semen-mediated enhancement of HIV infection and suggest the potential utility of incorporating gallic acid into a multicomponent microbicide targeting both the HIV virus and host components that promote viral infection.Amyloid fibrils are ordered protein aggregates associated with a large number of human diseases, many of which are neurodegenerative in nature, such as Alzheimer disease and Parkinson disease (1-3). They are characterized by their cross-␤ structure, with ␤ sheets running perpendicular to the fibril axis, and by their ability to bind to certain fluorescent dyes, such as thioflavin T (ThT), 4 whose fluorescence intensity increases considerably upon binding to amyloid fibrils.Amyloid fibrils are also found in semen from young, healthy men (4). Whether these fibrils serve a physiological function is not known, but they have been shown to markedly increase infection by a variety of sexually transmitted viruses, most notably HIV-1 (5-7). Under limiting dilution conditions, semen fibrils can increase HIV infection rates by up to 5 orders of magnitude (6). These fibrils are made up of naturally occurring peptide fragments in semen (6, 8 -10). The best characterized semen fibril is made up of a 39-residue fragment from human prostatic acid phosphatase (PAPf39) and has been termed SEVI (semen-derived enhancer of viral infection) (6). More recently, a second set of semen fibrils was identified from prostate-specific antigen-generated fragments of semenogelin (referred to collectivel...

Myricetin antagonizes semen-derived enhancer of viral infection (SEVI) formation and influences its infection-enhancing activity

“…For example, based on its ability to abrogate SEVI-mediated enhancement of HIV-1 infection, the natural ingredient of green tea EGCG appears to be a promising supplement to antiretroviral microbicides [ 12 , 13 ]. A component of EGCG, gallic acid, is able to directly abrogate the viral enhancement of seminal fibrils and might be able to prevent HIV infection via sexual transmission [ 35 ]. Unfortunately, EGCG has poor solubility and poor oral bioavailability and easily undergoes oxidation in vivo, complicating its use in clinical trials [ 36 , 37 ].…”

Semen‐derived amyloidogenic peptides—Key players of HIV infection

“…BTA‐EG6 and its oligovalent derivatives prevented SEVI‐mediated enhancement of HIV infection. Gallic acid showed binding ability to SEVI amyloid fibrils and decreased semen‐mediated enhancement of HIV infection . Perturbation of surface electrostatics between cationic SEVI amyloids and HIV virions resulted in a decrease of HIV infectivity although the details on the physicochemical intermolecular interactions are unknown.…”

“…Gallic acid showed binding ability to SEVI amyloid fibrils and decreased semen-mediated enhancement of HIV infection. 48 Perturbation of surface electrostatics between cationic SEVI amyloids and HIV virions resulted in a decrease of HIV infectivity although the details on the physicochemical intermolecular interactions are unknown. Meanwhile, a D-enantiomeric peptide (RPRTRLHTHRNR), an inhibitor of Ab(1-42) amyloid formation, also attenuated SEVI amyloid-boosting infection of HIV.…”

Natural Seminal Amyloids as Targets for Development of Synthetic Inhibitors of HIV Transmission

“…23 Interestingly, a recent study has found that a segment of EGCG, gallic acid ( Figure 2B), is a potent binder of SEVI fibrils and purportedly inhibits SEVI-mediated interactions with HIV and target cell surfaces by decreasing the positive charge potential on the surface of mature SEVI amyloids. 27 The small molecule surfen is another example of a SEVI-binding molecule that inhibits the interaction between SEVI and cellular and viral surfaces. 28 Prior to reports on the effects of EGCG and its derivatives as aggregation inhibitors of SEVI, we reported an initial study of a hexa(ethylene glycol) derivative of benzothiazole aniline (BTA-EG 6 , Figure 3B) as a small molecule inhibitor of SEVI-mediated HIV infection.…”