Diazadispiroalkane Derivatives Are New Viral Entry Inhibitors.

Herpesviruses are widespread and can cause serious illness. Many currently available antiviral drugs have limited effects, result in rapid development of resistance, and often exhibit dose-dependent toxicity. Especially for human cytomegalovirus (HCMV), new well-tolerated compounds with novel mechanisms of action are urgently needed. In this study, we characterized the antiviral activity of two new diazadispiroalkane derivatives, 11826091 and 11826236. These two small molecules exhibited strong activity against low-passage-number HCMV. Pretreatment of cell-free virus with these compounds greatly reduced infection. Time-of-addition assays where 11826091 or 11826236 was added to cells before infection, before and during infection, or during or after infection demonstrated an inhibitory effect on early steps of infection. Interestingly, 11826236 had an effect by addition to cells after infection. Results from entry assays showed the major effect to be on attachment. Only 11826236 had a minimal effect on penetration comparable to heparin. Further, no effect on virus infection was found for cell lines with a defect in heparan sulfate expression or lacking all surface glycosaminoglycans, indicating that these small molecules bind to heparan sulfate on the cell surface. To test this further, we extended our analyses to pseudorabies virus (PrV), a member of the Alphaherpesvirinae, which is known to use cell surface heparan sulfate for initial attachment via nonessential glycoprotein C (gC). While infection with PrV wild type was strongly impaired by 11826091 or 11826236, as with heparin, a mutant lacking gC was unaffected by either treatment, demonstrating that primary attachment to heparan sulfate via gC is targeted by these small molecules.

Tetrahalogenated benzimidazole D-ribonucleosides are active against rat cytomegalovirus.

BACKGROUND: Benzimidazole D-ribonucleosides are potent and selective inhibitors of CMV infection that have been shown to target the viral terminase, the enzyme complex responsible for viral DNA cleavage into single unit-length genomes and subsequent DNA packaging into procapsids. Here, we evaluated the viral inhibition by benzimidazole D-ribonucleosides against rat cytomegalovirus (RCMV). METHODS: Antiviral activity of compounds Cl4RB and BTCRB against RCMV was quantified by measurement of plaque formation. Yield assays and electron microscopy of thin sections was performed using RCMV-infected cells in the presence or absence of the compounds. The effects of Cl4RB and BTCRB on cleavage of concatemers was analyzed by pulsed-field gel electrophoresis. To characterize the behaviour of the antiviral compounds in a more physiological environment, a 3D cell culture model was employed where cells are embedded in an extracellular matrix using rat-tail collagen I. RESULTS: Both compounds had an inhibitory effect against RCMV-E. Electron microscopy revealed that only few virions were formed in RCMV-E infected cells in the presence of the compounds. Pulsed-field gel electrophoresis showed that DNA concatemers failed to be processed in the presence of the compounds. Yield Assays showed a comparable viral growth in the 3D vs. 2D cell culture as well as inhibition in the presence of Cl4RB or BTCRB for RCMV-E/GFP. CONCLUSIONS: These results demonstrate that the tetrahalogenated benzimidazole D-ribonucleosides are effective against RCMV-E by preventing cleavage of concatemeric DNA and nuclear egress of mature capsids.