Broad anti-herpesviral activity of α-hydroxytropolones

Abstract

Herpesviruses are ubiquitous in animals and cause economic losses concomitant with many diseases. Most of the domestic animal herpesviruses are within the subfamily Alphaherpesvirinae, which includes human herpes simplex virus 1 (HSV-1). Suppression of HSV-1 replication has been reported with α-hydroxytropolones (αHTs), aromatic ring compounds that have broad bioactivity due to potent chelating activity. It is postulated that αHTs inhibit enzymes within the nucleotidyltransferase superfamily (NTS). These enzymes require divalent cations for nucleic acid cleavage activity. Potential targets include the nuclease component of the herpesvirus terminase (pUL15C), a highly conserved NTS-like enzyme that cleaves viral DNA into genomic lengths prior to packaging into capsids. Inhibition of pUL15C activity in biochemical assays by various αHTs previously revealed a spectrum of potencies. Interestingly, the most potent anti-pUL15C αHT inhibited HSV-1 replication to a limited extent in cell culture. The aim of this study was to evaluate three different αHT molecules with varying biochemical anti-pUL15C activity for a capacity to inhibit replication of veterinary herpesviruses (BoHV-1, EHV-1, and FHV-1) and HSV-1. Given the known discordant potencies between anti-pUL15C and HSV-1 replication inhibition, a second objective was to elucidate the mechanism of action of these compounds. The results show that αHTs broadly inhibit herpesviruses, with similar inhibitory effect against HSV-1, BoHV-1, EHV-1, and FHV-1. Based on immunoblotting, Southern blotting, and real-time qPCR, the compounds were found to specifically inhibit viral DNA replication. Thus, αHTs represent a new class of broadly active anti-herpesviral compounds with potential veterinary applications.

The HIV Integrase Inhibitor Raltegravir Inhibits Felid Alphaherpesvirus 1 Replication by Targeting both DNA Replication and Late Gene Expression

“…These results are consistent with our observation that raltegravir inhibited FeHV-1 replication without apparent effects on pUL15-C activity. It was also recently reported that these ␣-hydroxytropolones could inhibit the replication of a range of alphaherpesviruses, including FeHV-1 (61). They demonstrated that the compounds inhibited HHV-1 DNA replication rather than genome cleavage, similar to our observations with raltegravir.…”

RNA Polymerase II Promoter-Proximal Pausing and Release to Elongation Are Key Steps Regulating Herpes Simplex Virus 1 Transcription

“…To ensure that PAA and ACV treatments were blocking viral DNA replication, we quantified viral DNA in HEp-2 cells over a 22-h time period in the presence and absence of these drugs ( Fig. 2A), using a quantitative PCR (qPCR) approach, as performed previously (63). From time zero to 3 hpi, the amounts of viral DNA were similar for all treatments and failed to increase above input levels ( Fig.…”

“…Cells were treated and infected as described above. HSV-1 DNA copy numbers were calculated as described previously (63). In brief, DNA was isolated using the DNeasy blood and tissue kit (Qiagen).…”

Divergent synthesis of a thiolate-based α-hydroxytropolone library with a dynamic bioactivity profile

“…14 aHTs also have demonstrable activity against other herpesviruses including human cytomegalovirus 5b and Kaposi's sarcoma-associated herpesvirus, 21 as well as several animal herpesviruses. 22 For all these reasons, the continued development of aHTs as antiviral agents against HSV-1 is warranted.…”