Novel amphiphilic compounds effectively inactivate the vaccinia virus

An Overview of Antivirals against Monkeypox Virus and Other Orthopoxviruses

The current monkeypox outbreaks during the COVID-19 pandemic have reignited interest in orthopoxvirus antivirals. Monkeypox belongs to the Orthopoxvirus genus of the Poxviridae family, which also includes the variola virus, vaccinia virus, and cowpox virus. Two orally bioavailable drugs, tecovirimat and brincidofovir, have been approved for treating smallpox infections. Given their human safety profiles and in vivo antiviral efficacy in animal models, both drugs have also been recommended to treat monkeypox infection. To facilitate the development of additional orthopoxvirus antivirals, we summarize the antiviral activity, mechanism of action, and mechanism of resistance of orthopoxvirus antivirals. This perspective covers both direct-acting and host-targeting antivirals with an emphasis on drug candidates showing in vivo antiviral efficacy in animal models. We hope to speed the orthopoxvirus antiviral drug discovery by providing medicinal chemists with insights into prioritizing proper drug targets and hits for further development.

Glutaraldehyde inactivation of enveloped DNA viruses in the preparation of haemoglobin-based oxygen carriers

Glutaraldehyde (GA), used medically as a disinfectant and as a crosslinker for haemoglobin (Hb)-based oxygen carriers (HBOCs), was investigated for its ability to inactivate viruses during the preparation of these artificial blood substitutes. Porcine parvovirus (PPV; a non-enveloped DNA virus) and porcine pseudorabies virus (PRV; an enveloped DNA virus) were used as the virus indicators. Upon treatment with 0.1 mM GA, the titer of PRV decreased from 9.62 log₁₀ to 2.62 log₁₀ within 0.5 h, whereas that of PPV decreased from 7.00 log₁₀ to 2.30 log₁₀ in 5 h. Following treatment with 1.0 mM GA, the titer of PRV decreased from 11.00 log₁₀ to 1.97 log₁₀ within 0.5 h, whereas that of PPV decreased from 7.50 log₁₀ to 3.43 log₁₀ in 4.5 h. During the polymerization of Hb with GA, the GA concentration decreased to 1.0 and 0.1 mM within 30 and 50 min, respectively, at a GA:Hb molar ratio of 10:1, whereas at a GA:Hb molar ratio of 30:1, GA decreased to those same concentrations in 1.5 and 2.5 h, respectively. This rapid decrease in GA concentration during its polymerization with Hb indicates that GA must be added into the Hb solution in a short time in order to get as high a initial concentration as possible. In this study, the GA can only inactivate PRV effectively, given that a longer time (4.5 h) was required for it to inactivate the PPV titer. This study therefore demonstrates that GA inactivates the enveloped DNA virus only during the preparation of HBOCs.

Artificial ribonucleases inactivate a wide range of viruses using their ribonuclease, membranolytic, and chaotropic-like activities

Artificial ribonucleases (aRNases) are small compounds catalysing RNA cleavage. Recently we demonstrated that aRNases readily inactivate various viruses in vitro. Here, for three series of aRNases (1,4-diazabicyclo [2.2.2]octane-based and peptide-like compounds) we show that apart from ribonuclease activity the aRNases display chaotropic-like and membranolytic activities. The levels of membranolytic and chaotropic-like activities correlate well with the efficiency of various viruses inactivation (enveloped, non-enveloped, RNA-, DNA-containing). We evaluated the impact of these activities on the efficiency of virus inactivation and found: i) the synergism between membranolytic and chaotropic-like activities is sufficient for the inactivation of enveloped viruses (influenza A, encephalitis, vaccinia viruses) for 1,4-diazabicyclo [2.2.2]octane based aRNases, ii) the inactivation of non-enveloped viruses (encephalomyocarditis, acute bee paralysis viruses) is totally dependent on the synergism of chaotropic-like and ribonuclease activities, iii) ribonuclease activity plays a leading role in the inactivation of RNA viruses by aRNases Dp12F6, Dtr12 and K-D-1, iv) peptide-like aRNases (L2-3, K-2) being effective virus killers have a more specific mode of action. Obtained results clearly demonstrate that aRNases represent a new class of broad-spectrum virus-inactivating agents.

Ribonucleases as antiviral agents

Many ribonucleases (RNases) are able to inhibit the reproduction of viruses in infected cell cultures and laboratory animals, but the molecular mechanisms of their antiviral activity remain unclear. The review discusses the well-known RNases that possess established antiviral effects, including both intracellular RNases (RNase L, MCPIP1 protein, and eosinophil-associated RNases) and exogenous RNases (RNase A, BS-RNase, onconase, binase, and synthetic RNases). Attention is paid to two important, but not always obligatory, aspects of molecules of RNases that have antiviral properties, i.e., catalytic activity and ability to dimerize. The hypothetic scheme of virus elimination by exogenous RNases that reflects possible types of interaction of viruses and RNases with a cell is proposed. The evidence for RNases as classical components of immune defense and thus perspective agents for the development of new antiviral therapeutics is proposed.