Abstract
In semen, proteolytic peptide fragments from prostatic acid phosphatase can form amyloid fibrils termed SEVI (semen-derived enhancer of viral infection). These fibrils greatly enhance human immunodeficiency virus (HIV) infectivity by increasing the attachment of virions to target cells. Therefore, SEVI may have a significant impact on whether HIV is successfully transmitted during sexual contact. Here, we demonstrate that surfen, a small molecule heparan sulfate proteoglycan antagonist, inhibits both SEVI- and semen-mediated enhancement of HIV type 1 infection. Surfen interferes with the binding of SEVI to both target cells and HIV type 1 virions but does not deaggregate SEVI fibrils. Because SEVI can increase HIV infectivity by several orders of magnitude, supplementing current HIV microbicide candidates with SEVI inhibitors, such as surfen, might greatly increase their potency.
Highlights
Semen has been reported to enhance human immunodeficiency virus (HIV) infection [1]
This led us to hypothesize that the fibrils may bind target cells by interacting with cell-surface heparan sulfate proteoglycans (HSPG), naturally occurring anionic carbohydrate polymers that are closely related in structure to heparin sulfate
Target Cells—We have previously demonstrated that pretreatment of target cells with SEVI enhances their fusion to HIV-1 virions [3]
Summary
Cell Culture—293T and TZM-bl cells were cultured in Dulbecco’s modified Eagle’s medium supplemented with 10% fetal bovine serum, L-glutamine, penicillin (50 units/ml), and streptomycin (50 g/ml). Infectivity Assays—For infection of TZM-bl cells, CCR5tropic HIV-1 (20 ng/ml p24Gag) was pretreated for 5 min with diluted SEVI or semen in the presence or absence of surfen. For infection of CHO and pgs-A745 cells, luciferase-expressing HIV-1 (10 ng/ml p24Gag) was pretreated for 5 min with the indicated concentration of SEVI. As a positive control for cytotoxicity, cells were treated with the same concentration of semen for 3 days without medium replacement and assayed for viability. Fluorescence Microscopy—FITC-labeled SEVI (20 g/ml) was pretreated with the indicated concentration of surfen or chloroquine for 30 min and incubated for 1 h at 37 °C with 2.5 ϫ 104 TZM-bl cells seeded in an 8-well LabTek chamber (Nunc). Samples were prepared for imaging as described [3]
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