Cyclodextrins and cyclodextrin derivatives were demonstrated to improve the antiviral potency of numerous drugs, but also to be endowed with intrinsic antiviral action. They are suitable building blocks for the synthesis of functionalized polymer structures with potential antiviral activity. Accordingly, four water-soluble hyper-branched beta cyclodextrin (βCD)-based anionic polymers were screened against herpes simplex virus (HSV-2), respiratory syncytial virus (RSV), rotavirus (HRoV), and influenza virus (FluVA). They were characterized by FTIR-ATR, TGA, elemental analyses, zeta-potential measurements, and potentiometric titrations, while the antiviral activity was investigated with specific in vitro assays. The polymer with the highest negative charge, pyromellitic dianhydride-linked polymer (P_PMDA), showed significant antiviral action against RSV and HSV-2, by inactivating RSV free particles and by altering HSV-2 binding to the cell. The polymer fraction with the highest molecular weight showed the strongest antiviral activity and both P_PMDA and its active fractions were not toxic for cells. Our results suggest that the polymer virucidal activity against RSV can be exploited to produce new antiviral materials to counteract the virus dissemination through the air or direct contact. Additionally, the strong HSV-2 binding inhibition along with the water solubility of P_PMDA and the acyclovir complexation potential of βCD are attractive features for developing new therapeutic topical options against genital HSV-2 infection.

Genital herpes, most frequently caused by herpes simplex virus 2 (HSV-2) infection, is one of the most prevalent sexually transmitted infections. The current rationale for the treatment of HSV-2 infection involves nucleoside analogs (e.g. acyclovir) to suppress reactivation. Enzymatic oxysterols are endogenous 27-carbon atoms mole-cules produced by enzymatic cholesterol oxidation, and recently emerged as a broad-spectrum host targeting antivirals. In this study, we screened selected members of an in-house synthesized library of oxysterol analogs for their activity against HSV-2, identifying three compounds, named PFM064, PFM067, and PFM069, endowed with 50% effective concentrations (EC50) in the micromolar range, without exerting any apparent cytotoxicity. Moreover, the results obtained showed the ability of the novel derivatives to inhibit both cell-to-cell fusion induced by HSV-2, and the production of an intracellular viral progeny. Further experiments performed with PFM067 (which was selected for more-in-depth studies as the most effective synthetic analog) showed that these molecules act in a late stage of HSV-2 replicative cycle, by sequestering viral glycoproteins in the Golgi compartment, and likely inhibiting the nuclear egress of neo-synthetized viral capsids.Taken together, these results point to PFM067 as a promising chemical scaffold for the development of novel herpetic antivirals.

Varicella-zoster Virus (VZV) is a relevant pathogen belonging to the herpesviridiae family. Primary VZV infection causes chickenpox, and results in latent infection of sensory ganglia. Later in life, VZV can reactivate causing herpes zoster (HZ), which can be associated with severe complications in immunocompromised individuals. Currently, the available antivirals used to treat VZV infection target the DNA replication stage; however, resistance to these drugs has been reported in both immunocompromised and immunocompetent patients. For this reason, the identification of new antiviral molecules against VZV infection is a priority. Recently our research group demonstrated that the endogenous oxysterol 25R,26-hydroxycholesterol (25R,26OHC, more commonly named 27-hydroxycholesterol) and an oxysterol synthetic analog named PFM067 inhibit herpes simplex virus (HSV) replication. In this study we explored the antiviral activity of 25-hydroxycholesterol (25OHC), 25R,26OHC, and PFM067 against VZV. We demonstrated that 25R,26OHC and PFM067 exert antiviral activity against VZV with an EC₅₀ in the low micromolar range and are able to significantly reduce the area of the viral plaques. Moreover, 25R,26OHC and PFM067 can inhibit the egress of viral glycoprotein gE from the cis-Golgi compartment, similarly to what demonstrated by our group for HSV-2. Additionally, we show that 25R,26OHC and PFM067 act synergistically when used in combination with acyclovir (ACV). The promising antiviral activity of 25R,26OHC and PFM067, along with their different mechanism of action compared to ACV, makes these molecules suitable candidates for further investigation of the molecular target of oxysterols.