An effective inactivant based on singlet oxygen-mediated lipid oxidation implicates a new paradigm for broad-spectrum antivirals

Membrane-Active Singlet Oxygen Photogenerators as a Paradigm for Broad-Spectrum Antivirals: The Case of Halogenated (BOron)-DIPYrromethenes

Enveloped viruses, such as flaviviruses and coronaviruses, are pathogens of significant medical concern that cause severe infections in humans. Some photosensitizers are known to possess virucidal activity against enveloped viruses, targeting their lipid bilayer. Here we report a series of halogenated difluoroboron-dipyrromethene (BODIPYs) photosensitizers with strong virus-inactivating activity. Our structure-activity relationship analysis revealed that BODIPY scaffolds with a heavy halogen atom demonstrate significant efficacy against both tick-borne encephalitis virus (TBEV; Flaviviridae family) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; Coronaviridae family) along with high singlet oxygen quantum yields. Moreover, select compounds also inactivated other enveloped viruses, such as herpes simplex virus type 1 and monkeypox virus. The nature and length of the alkyl side chain notably influenced the virus-inactivating activity of BODIPY molecules. Furthermore, molecular dynamics studies highlighted the critical importance of the positioning of the chromophore moiety within the lipid bilayer. As membrane-targeting photosensitizers, BODIPYs interact directly with virus particles, causing damage to the viral envelope membranes. Thus, TBEV pretreated with BODIPY was completely noninfective for lab mice. Consequently, BODIPY-based photosensitizers hold potential either as broad-spectrum virus-inactivating antivirals against a variety of phylogenetically unrelated enveloped viruses or as potent inactivators of viruses for the development of vaccines for preventing life-threatening emerging viral diseases.

Photodynamic Inactivation of Human Herpes Virus In Vitro with Ga(III) and Zn(II) Phthalocyanines

Photodynamic inactivation (PDI) has been revealed as a valuable approach against viral infections because of the fast therapeutic effect and low possibility of resistance development. The photodynamic inhibition of the infectivity of human herpes simplex virus type 1 (HSV-1) strain Victoria at different stages of its reproduction was studied. PDI activity was determined on extracellular virions, on the stage of their adsorption to the Madin-Darby bovine kidney (MDBK) cell line and inhibition of the viral replication stage by application of two tetra-methylpyridiloxy substituted gallium and zinc phthalocyanines (ZnPcMe and GaPcMe) upon 660 nm light exposure with a light-emitting diode (LED 660 nm). The PDI effect was evaluated on extracellular virions and virus adsorption by the terminal dilution method and the change in viral infectivity, which was compared to the untreated control group. The decrease in viral titer (Δlgs) was determined. The effect on the replicative cycle of the virus was determined using the cytopathic effect inhibition (CPE) assay. The direct influence on the virions showed a remarkable effect with a decrease in the viral titer more than 4 (Δlg > 4). The influence of the virus to the cell on the stage of adsorption was also significantly affected by the exposure time and the concentration of applied photosensitizers. A distinct inhibition was evaluated for ZnPcMe at the viral replication stage, which demonstrated a high photoinactivation index (PII = 33.0). This study suggested the high efficacy of PDI with phthalocyanines on HSV-1 virus, with full inhibition caused by the mechanism of singlet oxygen generation. These promising data are a good basis for further investigations on the PDI application against pathogenic viruses.

Salvianolic acid A inhibits pseudorabies virus infection by directly inactivating the virus particle

BACKGROUND

Pseudorabies virus (PRV), a member of the family Herpesviridae, is responsible for significant economic losses in the pig industry and has recently been associated with human viral encephalitis, leading to severe neurological symptoms post-recovery. Despite the widespread impact of PRV, there are currently no approved effective drugs for treating PRV-related diseases in humans or pigs. Therefore, the exploration and discovery of safe and effective drugs for the prevention and treatment of PRV infection is of paramount importance.

PURPOSE

The objective of this study is to screen and identify natural compounds with antiviral activity against PRV.

METHODS

First, we used a strain of PRV with green fluorescent protein (PRV-GFP) to screen a natural product chemical library to identify potential antiviral drugs. Next, we assessed the antiviral abilities of salvianolic acid A (SAA) in vitro using virus titer assay, qPCR, and IFA. We investigated the mechanisms of SAA's antiviral activity through viral attachment, internalization, inactivation, and nuclease digestion assay. Finally, we evaluated the efficacy of SAA in inactivating PRV using mice as the experimental subjects.

RESULTS

This study screened 206 natural compounds for anti-PRV activity in vitro, resulting in the identification of seven potential antiviral agents. Notably, SAA emerged as a promising candidate with significant anti-PRV activity. The mechanism of action may be that SAA can directly inactivate the virus by disrupting viral envelope. In vivo experiments have shown that pre-incubation of SAA and PRV can effectively inhibit the infectivity and pathogenicity of PRV in mice.

CONCLUSION

This study offers valuable insights into the antiviral properties of SAA, potentially informing strategies for controlling PRV epidemics and treating related diseases in both humans and animals.

The synergistic bactericidal effect of simultaneous 222 nm krypton-chlorine excilamp and 307 nm UVB light treatment on sliced cheese and its mechanisms

In this study, we investigated the combined effect of 222 nm krypton-chlorine excilamp (EX) and 307 nm ultraviolet-B (UVB) light on the inactivation of Salmonella Typhimurium and Listeria monocytogenes on sliced cheese. The data confirmed that simultaneous exposure to EX and UVB irradiation for 80 s reduced S. Typhimurium and L. monocytogenes population by 3.50 and 3.20 log CFU/g, respectively, on sliced cheese. The synergistic cell count reductions in S. Typhimurium and L. monocytogenes in the combined treatment group were 0.88 and 0.59 log units, respectively. The inactivation mechanism underlying the EX and UVB combination treatment was evaluated using fluorescent staining. The combination of EX and UVB light induced the inactivation of reactive oxygen species (ROS) defense enzymes (superoxide dismutase) and synergistic ROS generation, resulting in synergistic lipid peroxidation and destruction of the cell membrane. There were no significant (P > 0.05) differences in the color, texture, or sensory attributes of sliced cheese between the combination treatment and control groups. These results demonstrate that combined treatment with EX and UVB light is a potential alternative strategy for inactivating foodborne pathogens in dairy products without affecting their quality.

Effect of different inactivants and preservatives on the stability of 146S fraction of foot-and-mouth diseases virus

Foot-and-mouth disease virus (FMDV) cripples livestock by imparting devastating effects to economy. A good vaccine is the key to stopping it, but due to instability of 146S of FMDV, it is becoming difficult. This is bad because only 146S can fight against disease and its dissociation ultimately leads to decreased potency of vaccine. This study aimed to preserve the integrity of 146S in vaccine using different inactivators and preservatives. Foot-and-mouth Disease virus type 'O' was propagated on baby hamster kidney 21 cell lines and inactivated using formalin or binary ethylenimine (BEI). Size exclusion high performance liquid chromatography analysis revealed minimal 146S loss after double inactivation with formalin and BEI. This inactivated virus was further formulated into oil-based vaccine with sodium thiomersal or chloroform as a preservative. Our findings demonstrated that chloroform outperformed thiomersal in maintaining shelf life of vaccine. This claims that the combined approach of double inactivation with formalin and BEI followed by chloroform as preservative offered a promising strategy for developing efficacious FMDV.

Antiviral activity of the host defense peptide piscidin 1: investigating a membrane-mediated mode of action

Outbreaks of viral diseases are on the rise, fueling the search for antiviral therapeutics that act on a broad range of viruses while remaining safe to human host cells. In this research, we leverage the finding that the plasma membranes of host cells and the lipid bilayers surrounding enveloped viruses differ in lipid composition. We feature Piscidin 1 (P1), a cationic host defense peptide (HDP) that has antimicrobial effects and membrane activity associated with its N-terminal region where a cluster of aromatic residues and copper-binding motif reside. While few HDPs have demonstrated antiviral activity, P1 acts in the micromolar range against several enveloped viruses that vary in envelope lipid composition. Notably, it inhibits HIV-1, a virus that has an envelope enriched in cholesterol, a lipid associated with higher membrane order and stability. Here, we first document through plaque assays that P1 boasts strong activity against SARS-CoV-2, which has an envelope low in cholesterol. Second, we extend previous studies done with homogeneous bilayers and devise cholesterol-containing zwitterionic membranes that contain the liquid disordered (Ld; low in cholesterol) and ordered (Lo, rich in cholesterol) phases. Using dye leakage assays and cryo-electron microscopy on vesicles, we show that P1 has dramatic permeabilizing capability on the Lo/Ld, an effect matched by a strong ability to aggregate, fuse, and thin the membranes. Differential scanning calorimetry and NMR experiments demonstrate that P1 mixes the lipid content of vesicles and alters the stability of the Lo. Structural studies by NMR indicate that P1 interacts with the Lo/Ld by folding into an α-helix that lies parallel to the membrane surface. Altogether, these results show that P1 is more disruptive to phase-separated than homogenous cholesterol-containing bilayers, suggesting an ability to target domain boundaries. Overall, this multi-faceted research highlights how a peptide that interacts strongly with membranes through an aromatic-rich N-terminal motif disrupt viral envelope mimics. This represents an important step towards the development of novel peptides with broad-spectrum antiviral activity.

Layered Double Hydroxide-Based PdCux@LDH Alloy Nanozyme for a Singlet Oxygen-Boosted Sonodynamic Therapy

Redox nanozymes have demonstrated tremendous promise in disrupting cellular homeostasis toward cancer therapy, but a dysfunctional competition of diverse activities makes it normally restricted by the complex tumor microenvironment (TME). As palladium nanocrystals can achieve the precise regulation of the enzyme-like activity by regulating exposed crystal planes, noble metal nanoalloys can enhance the enzyme-like activity by promoting electron transfer and enhanced active sites. Herein, bimetallic nanoalloys with optimized enzymatic activity were intelligently designed via the interaction between the Pd and layered double hydroxide, denoted as PdCux@LDH. This PdCux@LDH is able to produce long-lived singlet oxygen (1O2) with high efficiency and selectivity for ultrasound-improved cancer therapy. In addition, this PdCux@LDH nanozyme demonstrated unique surface-dependent multienzyme-mimicking activities for catalyzing cascade reactions: oxidase (OXD)- and catalase (CAT)-mimicking activities. Interestingly, ultrasound (US) stimulation can further improve the dual-enzyme-mimicking activities and impart superior reactive oxygen species (ROS) generation activity, thereby further consuming nicotinamide adenine dinucleotide (NADH) to cause mitochondrial dysfunction, resulting in a highly efficient alloy nanozyme-mediated cancer therapy. This work opens a new research avenue to apply nanozymes for effective sonodynamic therapies (SDT).

Spin-state Conversion by Asymmetrical Orbital Hybridization in Ni-doped Co3 O4 to Boost Singlet Oxygen Generation for Microbial Disinfection

Singlet oxygen (1 O2 ) plays a significant role in environmental and biomedical disinfection fields. Electrocatalytic processes hold great potential for 1 O2 generation, but remain challenging. Herein, a facile Ni doping converted spin-state transition approach is reported for boosting 1 O2 production. Magnetic analysis and theoretical calculations reveal that Ni occupied at the octahedral site of Co3 O4 can effectively induce a low-to-high spin-state transition. The high-spin Ni-Co3 O4 generate appropriate binding strength and enhance electron transfer between the Co centers with oxygen intermediates, thereby improving the catalytic activity of Ni-Co3 O4 for effective generating 1 O2 . In neutral conditions, 1×106  CFU mL-1 Gram-negative ESBL-producing Escherichia coli (E. coli) could be inactivated by Ni-Co3 O4 system within 5 min. Further antibacterial mechanisms indicate that 1 O2 can lead to cell membrane damage and DNA degradation so as to irreversible cell death. Additionally, the developed Ni-Co3 O4 system can effectively inactivate bacteria from wastewater and bioaerosols. This work provides an effective strategy for designing high-spin electrocatalysis to boost 1 O2 generation for disinfection process.

Antiviral activity of porphyrins and porphyrin-like compounds against tick-borne encephalitis virus: Blockage of the viral entry/fusion machinery by photosensitization-mediated destruction of the viral envelope

Tick-borne encephalitis virus (TBEV), the causative agent of tick-borne encephalitis (TBE), is a medically important flavivirus endemic to the European-Asian continent. Although more than 12,000 clinical cases are reported annually worldwide, there is no anti-TBEV therapy available to treat patients with TBE. Porphyrins are macrocyclic molecules consisting of a planar tetrapyrrolic ring that can coordinate a metal cation. In this study, we investigated the cytotoxicity and anti-TBEV activity of a large series of alkyl- or (het)aryl-substituted porphyrins, metalloporphyrins, and chlorins and characterized their molecular interactions with the viral envelope in detail. Our structure-activity relationship study showed that the tetrapyrrole ring is an essential structural element for anti-TBEV activity, but that the presence of different structurally distinct side chains with different lengths, charges, and rigidity or metal cation coordination can significantly alter the antiviral potency of porphyrin scaffolds. Porphyrins were demonstrated to interact with the TBEV lipid membrane and envelope protein E, disrupt the TBEV envelope and inhibit the TBEV entry/fusion machinery. The crucial mechanism of the anti-TBEV activity of porphyrins is based on photosensitization and the formation of highly reactive singlet oxygen. In addition to blocking viral entry and fusion, porphyrins were also observed to interact with RNA oligonucleotides derived from TBEV genomic RNA, indicating that these compounds could target multiple viral/cellular structures. Furthermore, immunization of mice with porphyrin-inactivated TBEV resulted in the formation of TBEV-neutralizing antibodies and protected the mice from TBEV infection. Porphyrins can thus be used to inactivate TBEV while retaining the immunogenic properties of the virus and could be useful for producing new inactivated TBEV vaccines.

Alkyl Derivatives of Perylene Photosensitizing Antivirals: Towards Understanding the Influence of Lipophilicity

Amphipathic perylene derivatives are broad-spectrum antivirals against enveloped viruses that act as fusion inhibitors in a light-dependent manner. The compounds target the lipid bilayer of the viral envelope using the lipophilic perylene moiety and photogenerating singlet oxygen, thereby causing damage to unsaturated lipids. Previous studies show that variation of the polar part of the molecule is important for antiviral activity. Here, we report modification of the lipophilic part of the molecule, perylene, by the introduction of 4-, 8-, and 12-carbon alkyls into position 9(10) of the perylene residue. Using Friedel-Crafts acylation and Wolff-Kishner reduction, three 3-acetyl-9(10)-alkylperylenes were synthesized from perylene and used to prepare 9 nucleoside and 12 non-nucleoside amphipathic derivatives. These compounds were characterized as fluorophores and singlet oxygen generators, as well as tested as antivirals against herpes virus-1 (HSV-1) and vesicular stomatitis virus (VSV), both known for causing superficial skin/mucosa lesions and thus serving as suitable candidates for photodynamic therapy. The results suggest that derivatives with a short alkyl chain (butyl) have strong antiviral activity, whereas the introduction of longer alkyl substituents (n = 8 and 12) to the perylenyethynyl scaffold results in a dramatic reduction of antiviral activity. This phenomenon is likely attributable to the increased lipophilicity of the compounds and their ability to form insoluble aggregates. Moreover, molecular dynamic studies revealed that alkylated perylene derivatives are predominately located closer to the middle of the bilayer compared to non-alkylated derivatives. The predicted probability of superficial positioning correlated with antiviral activity, suggesting that singlet oxygen generation is achieved in the subsurface layer of the membrane, where the perylene group is more accessible to dissolved oxygen.

Antiviral activity of singlet oxygen-photogenerating perylene compounds against SARS-CoV-2: Interaction with the viral envelope and photodynamic virion inactivation

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has prompted great interest in novel broad-spectrum antivirals, including perylene-related compounds. In the present study, we performed a structure-activity relationship analysis of a series of perylene derivatives, which comprised a large planar perylene residue, and structurally divergent polar groups connected to the perylene core by a rigid ethynyl or thiophene linker. Most of the tested compounds did not exhibit significant cytotoxicity towards multiple cell types susceptible to SARS-CoV-2 infection, and did not change the expressions of cellular stress-related genes under normal light conditions. These compounds showed nanomolar or sub-micromolar dose-dependent anti-SARS-CoV-2 activity, and also suppressed the in vitro replication of feline coronavirus (FCoV), also termed feline infectious peritonitis virus (FIPV). Perylene compounds exhibited high affinity for liposomal and cellular membranes, and efficiently intercalated into the envelopes of SARS-CoV-2 virions, thereby blocking the viral-cell fusion machinery. Furthermore, the studied compounds were demonstrated to be potent photosensitizers, generating reactive oxygen species (ROS), and their anti-SARS-CoV-2 activities were considerably enhanced after irradiation with blue light. Our results indicated that photosensitization is the major mechanism underlying the anti-SARS-CoV-2 activity of perylene derivatives, with these compounds completely losing their antiviral potency under red light. Overall, perylene-based compounds are broad-spectrum antivirals against multiple enveloped viruses, with antiviral action based on light-induced photochemical damage (ROS-mediated, likely singlet oxygen-mediated), causing impairment of viral membrane rheology.

Membrane-Targeting Perylenylethynylphenols Inactivate Medically Important Coronaviruses via the Singlet Oxygen Photogeneration Mechanism

Perylenylethynyl derivatives have been recognized as broad-spectrum antivirals that target the lipid envelope of enveloped viruses. In this study, we present novel perylenylethynylphenols that exhibit nanomolar or submicromolar antiviral activity against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and feline infectious peritonitis virus (FIPV) in vitro. Perylenylethynylphenols incorporate into viral and cellular membranes and block the entry of the virus into the host cell. Furthermore, these compounds demonstrate an ability to generate singlet oxygen when exposed to visible light. The rate of singlet oxygen production is positively correlated with antiviral activity, confirming that the inhibition of fusion is primarily due to singlet-oxygen-induced damage to the viral envelope. The unique combination of a shape that affords affinity to the lipid bilayer and the capacity to generate singlet oxygen makes perylenylethynylphenols highly effective scaffolds against enveloped viruses. The anticoronaviral activity of perylenylethynylphenols is strictly light-dependent and disappears in the absence of daylight (under red light). Moreover, these compounds exhibit negligible cytotoxicity, highlighting their significant potential for further exploration of the precise antiviral mechanism and the broader scope and limitations of this compound class.

Manipulation of Oxidative Stress Responses by Non-Thermal Plasma to Treat Herpes Simplex Virus Type 1 Infection and Disease

Herpes simplex virus type 1 (HSV-1) is a contagious pathogen with a large global footprint, due to its ability to cause lifelong infection in patients. Current antiviral therapies are effective in limiting viral replication in the epithelial cells to alleviate clinical symptoms, but ineffective in eliminating latent viral reservoirs in neurons. Much of HSV-1 pathogenesis is dependent on its ability to manipulate oxidative stress responses to craft a cellular environment that favors HSV-1 replication. However, to maintain redox homeostasis and to promote antiviral immune responses, the infected cell can upregulate reactive oxygen and nitrogen species (RONS) while having a tight control on antioxidant concentrations to prevent cellular damage. Non-thermal plasma (NTP), which we propose as a potential therapy alternative directed against HSV-1 infection, is a means to deliver RONS that affect redox homeostasis in the infected cell. This review emphasizes how NTP can be an effective therapy for HSV-1 infections through the direct antiviral activity of RONS and via immunomodulatory changes in the infected cells that will stimulate anti-HSV-1 adaptive immune responses. Overall, NTP application can control HSV-1 replication and address the challenges of latency by decreasing the size of the viral reservoir in the nervous system.

5-(Perylen-3-ylethynyl)uracil as an antiviral scaffold: Potent suppression of enveloped virus reproduction by 3-methyl derivatives in vitro

Amphipathic nucleoside and non-nucleoside derivatives of pentacyclic aromatic hydrocarbon perylene are known as potent non-cytotoxic broad-spectrum antivirals. Here we report 3-methyl-5-(perylen-3-ylethynyl)-uracil-1-acetic acid and its amides, a new series of compounds based on a 5-(perylen-3-ylethynyl)-uracil scaffold. The compounds demonstrate pronounced in vitro activity against arthropod-borne viruses, namely tick-borne encephalitis virus (TBEV) and yellow fever virus (YFV), in plaque reduction assays with EC₅₀ values below 1.9 and 1.3 nM, respectively, and Chikungunya virus (CHIKV) in cytopathic effect inhibition test with EC₅₀ values below 3.2 μM. The compounds are active against respiratory viruses as well: severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) in cytopathic effect inhibition test and influenza A virus (IAV) in virus titer reduction experiments are inhibited - EC₅₀ values below 51 nM and 2.2 μM, respectively. The activity stems from the presence of a hydrophobic perylene core, and all of the synthesized compounds exhibit comparable ¹O₂ generation rates. Nonetheless, activity can vary by orders of magnitude depending on the hydrophilic part of the molecule, suggesting a complex mode of action. A time-of-addition experiment and fluorescent imaging indicate that the compounds inhibit viral fusion in a dose-dependent manner. The localization of the compound in the lipid bilayers and visible damage to the viral envelope suggest the membrane as the primary target. Dramatic reduction of antiviral activity with limited irradiation or under treatment with antioxidants further cements the idea of photoinduced ROS-mediated viral envelope damage being the mode of antiviral action.

Emerging roles of ferroptosis in infectious diseases

In living organisms, lipid peroxidation is a continuously occurring cellular process and therefore involved in various physiological and pathological contexts. Among the broad variety of lipids, polyunsaturated fatty acids (PUFA) constitute a major target of oxygenation either when released as mediators by phospholipases or when present in membranous phospholipids. The last decade has seen the characterization of an iron- and lipid peroxidation-dependent cell necrosis, namely, ferroptosis, that involves the accumulation of peroxidized PUFA-containing phospholipids. Further studies could link ferroptosis in a very large body of (physio)-pathological processes, including cancer, neurodegenerative, and metabolic diseases. In this review, we mostly focus on the emerging involvement of lipid peroxidation-driven ferroptosis in infectious diseases, and the immune consequences. We also discuss the putative ability of microbial virulence factors to exploit or to dampen ferroptosis regulatory pathways to their own benefit.

Hydrophobic Rose Bengal Derivatives Exhibit Submicromolar-to-Subnanomolar Activity against Enveloped Viruses

Rose Bengal (RB) is an anionic xanthene dye with multiple useful biological features, including photosensitization properties. RB was studied extensively as a photosensitizer, mostly for antibacterial and antitumor photodynamic therapy (PDT). The application of RB to virus inactivation is rather understudied, and no RB derivatives have been developed as antivirals. In this work, we used a synthetic approach based on a successful design of photosensitizing antivirals to produce RB derivatives for virus photoinactivation. A series of n-alkyl-substituted RB derivatives was synthesized and evaluated as antiviral photosensitizers. The compounds exhibited similar 1O2 generation rate and efficiency, but drastically different activities against SARS-CoV-2, CHIKV, and HIV; with comparable cytotoxicity for different cell lines. Submicromolar-to-subnanomolar activities and high selectivity indices were detected for compounds with C4-6 alkyl (SARS-CoV-2) and C6-8 alkyl (CHIKV) chains. Spectrophotometric assessment demonstrates low aqueous solubility for C8-10 congeners and a significant aggregation tendency for the C12 derivative, possibly influencing its antiviral efficacy. Initial evaluation of the synthesized compounds makes them promising for further study as viral inactivators for vaccine preparations.

On the Sensitivity of the Virion Envelope to Lipid Peroxidation

Emerging viruses are a public health threat best managed with broad spectrum antivirals. Common viral structures, like capsids or virion envelopes, have been proposed as targets for broadly active antiviral drugs. For example, a number of lipoperoxidators have been proposed to preferentially affect viral infectivity by targeting metabolically inactive enveloped virions while sparing metabolically active cells. However, this presumed preferential virion sensitivity to lipoperoxidation remains untested. To test whether virions are indeed more sensitive to lipoperoxidation than are cells, we analyzed the effects of two classic generic lipoperoxidators: lipophilic 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) and hydrophilic 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) on Vero and human foreskin fibroblasts (HFF) cell viability, HSV-1 plaquing efficiency, and virion and cell lipoperoxidation. Cells or virions were incubated with the lipoperoxidators at 37°C for 2 h or incubated in atmospheric O₂, and dose responses (half maximal cytotoxic and effective concentration [CC₅₀ and EC₅₀]) were evaluated by three or four parameter regression. The HSV-1 virions were slightly more sensitive to lipoperoxidators than were the cells (selectivity index [SI], 3.3 to 7.4). The effects of the lipophilic AMVN on both cell and virion viability directly correlated with the extent of membrane lipoperoxidation as evaluated by two different probes, C11-Bodipy and liperfluo. Moreover, the hydrophilic AAPH-induced virion inactivation at lower concentrations than did lipoperoxidation. Known lipoperoxidators inhibit infectivity via lipoperoxidation-independent mechanisms. Antioxidants protected against a loss of viral infectivity by less than 5-fold. Carrier bovine serum albumin (BSA) protected against both peroxidators to a similar extent when present together with the lipoperoxidating agents, suggesting that BSA quenches them as expected. Virions incubated in atmospheric oxidative conditions suffered losses of infectivity that were similar to those of chemically peroxidated virions, and they were protected by water soluble vitamin C and BSA with no evident lipoperoxidation, indicating predominant peroxidative damage to nonlipid virion components. Thus, lipoperoxidation is not a mechanism by which to specifically inhibit the infectivity of enveloped viruses, and the effects of known lipoperoxidators on virion infectivity are not solely mediated by lipoperoxidation. IMPORTANCE Small molecules that induce lipoperoxidation have been proposed repeatedly as potential antiviral drugs based on a presumed unique sensitivity of virions to this type of damage. Several small molecules that inactivate virions without affecting cells have been proposed to act primarily by inducing lipoperoxidation. However, the preferential sensitivity of virions to lipoperoxidators had not been experimentally evaluated. Using two of the best characterized small molecule lipoperoxidators, which are widely considered to be the prototypical water soluble and liposoluble lipoperoxidators, we show that lipoperoxidators have no preference for virions over cells. Moreover, they also inactivate virions by mechanisms other than the induction of lipoperoxidation. Therefore, the general induction of lipoperoxidation is not a path by which to develop antivirals. Moreover, molecules with specific antiviral activity which are not cytotoxic and have no preference to localize to virions over cells are unlikely to act primarily by inducing lipoperoxidation.

Exploring inactivation of SARS-CoV-2, MERS-CoV, Ebola, Lassa, and Nipah viruses on N95 and KN95 respirator material using photoactivated methylene blue to enable reuse

Background

The COVID-19 pandemic resulted in a worldwide shortage of N95 respirators, prompting the development of decontamination methods to enable limited reuse. Countries lacking reliable supply chains would also benefit from the ability to safely reuse PPE. Methylene blue (MB) is a light-activated dye with demonstrated antimicrobial activity used to sterilize blood plasma. Decontamination of respirators using photoactivated MB requires no specialized equipment, making it attractive for use in the field during outbreaks.

Methods

We examined decontamination of N95 and KN95 respirators using photoactivated MB and 3 variants of SARS-CoV-2, the virus that causes COVID-19; and 4 World Health Organization priority pathogens: Ebola virus, Middle East respiratory syndrome coronavirus, Nipah virus, and Lassa virus. Virus inactivation by pretreating respirator material was also tested.

Results

Photoactivated MB inactivated all tested viruses on respirator material, albeit with varying efficiency. Virus applied to respirator material pre-treated with MB was also inactivated, thus MB pretreatment may potentially protect respirator wearers from virus exposure in real-time.

Conclusions

These results demonstrate that photoactivated MB represents a cost-effective, rapid, and widely deployable method to decontaminate N95 respirators for reuse during supply shortages.

Inactivation strategies for SARS-CoV-2 on surgical masks using light-activated chemical dyes

Background

Methylene blue (MB) and riboflavin (RB) are light-activated dyes with demonstrated antimicrobial activity. They require no specialized equipment, making them attractive for widespread use. Due to COVID-19-related worldwide shortages of surgical masks, simple, safe, and effective decontamination methods for reusing masks have become desirable in clinical and public settings.

Material and methods

We examined the decontamination of SARS-CoV-2 Beta variant on surgical masks and Revolution-Zero Environmentally Sustainable (RZES) reusable masks using these photoactivated dyes. We pre-treated surgical masks with 2 MB concentrations, 2 RB concentrations, and 2 combinations of MB and RB. We also tested 7 MB concentrations on RZES masks.

Results

Photoactivated MB consistently inactivated SARS-CoV-2 at >99.9% for concentrations of 2.6 µM or higher within 30 min on RZES masks and 5 µM or higher within 5 min on disposable surgical masks. RB alone showed a lower, yet still significant inactivation (∼93-99%) in these conditions.

Discussion

MB represents a cost-effective, rapid, and widely deployable decontamination method for SARS-CoV-2. The simplicity of MB formulation makes it ideal for mask pre-treatment in low-resource settings.

Conclusions

The results demonstrate that MB effectively decontaminates SARS-CoV-2 at concentrations above 5 µM on surgical masks and above 10 µM on RZES masks.

Laser-Induced Graphene (LIG) as a Smart and Sustainable Material to Restrain Pandemics and Endemics: A Perspective

A healthy environment is necessary for a human being to survive. The contagious COVID-19 virus has disastrously contaminated the environment, leading to direct or indirect transmission. Therefore, the environment demands adequate prevention and control strategies at the beginning of the viral spread. Laser-induced graphene (LIG) is a three-dimensional carbon-based nanomaterial fabricated in a single step on a wide variety of low-cost to high-quality carbonaceous materials without using any additional chemicals potentially used for antiviral, antibacterial, and sensing applications. LIG has extraordinary properties, including high surface area, electrical and thermal conductivity, environmental-friendliness, easy fabrication, and patterning, making it a sustainable material for controlling SARS-CoV-2 or similar pandemic transmission through different sources. LIG's antiviral, antibacterial, and antibiofouling properties were mainly due to the thermal and electrical properties and texture derived from nanofibers and micropores. This perspective will highlight the conducted research and the future possibilities on LIG for its antimicrobial, antiviral, antibiofouling, and sensing applications. It will also manifest the idea of incorporating this sustainable material into different technologies like air purifiers, antiviral surfaces, wearable sensors, water filters, sludge treatment, and biosensing. It will pave a roadmap to explore this single-step fabrication technique of graphene to deal with pandemics and endemics in the coming future.

Photodynamic and Contact Killing Polymeric Fabric Coating for Bacteria and SARS-CoV-2

The development of low-cost, non-toxic, scalable antimicrobial textiles is needed to address the spread of deadly pathogens. Here, we report a polysiloxane textile coating that possesses two modes of antimicrobial inactivation, passive contact inactivation through amine/imine functionalities and active photodynamic inactivation through the generation of reactive oxygen species (ROS). This material can be coated and cross-linked onto natural and synthetic textiles through a simple soak procedure, followed by UV cure to afford materials exhibiting no aqueous leaching and only minimal leaching in organic solvents. This coating minimally impacts the mechanical properties of the fabric while also imparting hydrophobicity. Passive inactivation of Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) is achieved with >98% inactivation after 24 h, with a 23× and 3× inactivation rate increase against E. coli and MRSA, respectively, when green light is used to generate ROS. Up to 90% decrease in the infectivity of SARS-CoV-2 after 2 h of irradiated incubation with the material is demonstrated. These results show that modifying textiles with dual-functional polymers results in robust and highly antimicrobial materials that are expected to find widespread use in combating the spread of deadly pathogens.

Photosensitizing Antivirals

Antiviral action of various photosensitizers is already summarized in several comprehensive reviews, and various mechanisms have been proposed for it. However, a critical consideration of the matter of the area is complicated, since the exact mechanisms are very difficult to explore and clarify, and most publications are of an empirical and "phenomenological" nature, reporting a dependence of the antiviral action on illumination, or a correlation of activity with the photophysical properties of the substances. Of particular interest is substance-assisted photogeneration of highly reactive singlet oxygen (1O2). The damaging action of 1O2 on the lipids of the viral envelope can probably lead to a loss of the ability of the lipid bilayer of enveloped viruses to fuse with the lipid membrane of the host cell. Thus, lipid bilayer-affine 1O2 photosensitizers have prospects as broad-spectrum antivirals against enveloped viruses. In this short review, we want to point out the main types of antiviral photosensitizers with potential affinity to the lipid bilayer and summarize the data on new compounds over the past three years. Further understanding of the data in the field will spur a targeted search for substances with antiviral activity against enveloped viruses among photosensitizers able to bind to the lipid membranes.

NPC1-regulated dynamic of clathrin-coated pits is essential for viral entry

Viruses utilize cellular lipids and manipulate host lipid metabolism to ensure their replication and spread. Therefore, the identification of lipids and metabolic pathways that are suitable targets for antiviral development is crucial. Using a library of compounds targeting host lipid metabolic factors and testing them for their ability to block pseudorabies virus (PRV) and vesicular stomatitis virus (VSV) infection, we found that U18666A, a specific inhibitor of Niemann-Pick C1 (NPC1), is highly potent in suppressing the entry of diverse viruses including pseudotyped severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). NPC1 deficiency markedly attenuates viral growth by decreasing cholesterol abundance in the plasma membrane, thereby inhibiting the dynamics of clathrin-coated pits (CCPs), which are indispensable for clathrin-mediated endocytosis. Significantly, exogenous cholesterol can complement the dynamics of CCPs, leading to efficient viral entry and infectivity. Administration of U18666A improves the survival and pathology of PRV- and influenza A virus-infected mice. Thus, our studies demonstrate a unique mechanism by which NPC1 inhibition achieves broad antiviral activity, indicating a potential new therapeutic strategy against SARS-CoV-2, as well as other emerging viruses.

Stopping Membrane-Enveloped Viruses with Nanotechnology Strategies: Toward Antiviral Drug Development and Pandemic Preparedness

Membrane-enveloped viruses are a leading cause of viral epidemics, and there is an outstanding need to develop broad-spectrum antiviral strategies to treat and prevent enveloped virus infections. In this review, we critically discuss why the lipid membrane surrounding enveloped virus particles is a promising antiviral target and cover the latest progress in nanotechnology research to design and evaluate membrane-targeting virus inhibition strategies. These efforts span diverse topics such as nanomaterials, self-assembly, biosensors, nanomedicine, drug delivery, and medical devices and have excellent potential to support the development of next-generation antiviral drug candidates and technologies. Application examples in the areas of human medicine and agricultural biosecurity are also presented. Looking forward, research in this direction is poised to strengthen capabilities for virus pandemic preparedness and demonstrates how nanotechnology strategies can help to solve global health challenges related to infectious diseases.