Development of an inhalable antiviral powder formulation against respiratory syncytial virus.

Respiratory viruses including the respiratory syncytial virus (RSV) aggravate the global burden of virus-inflicted morbidity and mortality. Entry inhibitors are a promising class of antiviral drugs for combating these viruses, as they can prevent infection at the site of viral entry, i.e., the respiratory tract. Here we used a broad-spectrum entry inhibitor, composed of a ß-cyclodextrin backbone, functionalized with 11-mercapto-1-undecanesulfonate (CD-MUS) that is capable of neutralizing a variety of viruses that employ heparan sulfate proteoglycans (HSPG) to infect host cells. CD-MUS inactivates viral particles irreversibly by binding to viral attachment proteins through a multivalent binding mechanism. In the present study, we show that CD-MUS is well tolerated when administered to the respiratory tract of mice. Based on this, we developed an inhalable spray-dried powder formulation that fits the size requirements for lung deposition and disperses well upon use with the Cyclops dry powder inhaler (DPI). Using an in vitro dose-response assay, we show that the compound retained its activity against RSV after the spray drying process. Our study sets the stage for further in vivo studies, exploring the efficacy of pulmonary administered CD-MUS in animal models of RSV infection.

Potent Virustatic Polymer-Lipid Nanomimics Block Viral Entry and Inhibit Malaria Parasites In Vivo.

Infectious diseases continue to pose a substantial burden on global populations, requiring innovative broad-spectrum prophylactic and treatment alternatives. Here, we have designed modular synthetic polymer nanoparticles that mimic functional components of host cell membranes, yielding multivalent nanomimics that act by directly binding to varied pathogens. Nanomimic blood circulation time was prolonged by reformulating polymer-lipid hybrids. Femtomolar concentrations of the polymer nanomimics were sufficient to inhibit herpes simplex virus type 2 (HSV-2) entry into epithelial cells, while higher doses were needed against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Given their observed virustatic mode of action, the nanomimics were also tested with malaria parasite blood-stage merozoites, which lose their invasive capacity after a few minutes. Efficient inhibition of merozoite invasion of red blood cells was demonstrated both in vitro and in vivo using a preclinical rodent malaria model. We envision these nanomimics forming an adaptable platform for developing pathogen entry inhibitors and as immunomodulators, wherein nanomimic-inhibited pathogens can be secondarily targeted to sites of immune recognition.

Broad-Spectrum Extracellular Antiviral Properties of Cucurbit[n]urils.

Viruses are microscopic pathogens capable of causing disease and are responsible for a range of human mortalities and morbidities worldwide. They can be rendered harmless or destroyed with a range of antiviral chemical compounds. Cucurbit[n]urils (CB[n]s) are a family of macrocycle chemical compounds existing as a range of homologues; due to their structure, they can bind to biological materials, acting as supramolecular "hosts" to "guests", such as amino acids. Due to the increasing need for a nontoxic antiviral compound, we investigated whether cucurbit[n]urils could act in an antiviral manner. We have found that certain cucurbit[n]uril homologues do indeed have an antiviral effect against a range of viruses, including herpes simplex virus 2 (HSV-2), respiratory syncytial virus (RSV) and SARS-CoV-2. In particular, we demonstrate that CB[7] is the active homologue of CB[n], having an antiviral effect against enveloped and nonenveloped species. High levels of efficacy were observed with 5 min contact times across different viruses. We also demonstrate that CB[7] acts with an extracellular virucidal mode of action via host-guest supramolecular interactions between viral surface proteins and the CB[n] cavity, rather than via cell internalization or a virustatic mechanism. This finding demonstrates that CB[7] acts as a supramolecular virucidal antiviral (a mechanism distinct from other current extracellular antivirals), demonstrating the potential of supramolecular interactions for future antiviral disinfectants.

Polyanionic Amphiphilic Dendritic Polyglycerols as Broad-Spectrum Viral Inhibitors with a Virucidal Mechanism.

Heparin has been known to be a broad-spectrum inhibitor of viral infection for almost 70 years, and it has been used as a medication for almost 90 years due to its anticoagulant effect. This nontoxic biocompatible polymer efficiently binds to many types of viruses and prevents their attachment to cell membranes. However, the anticoagulant properties are limiting their use as an antiviral drug. Many heparin-like compounds have been developed throughout the years; however, the reversible nature of the virus inhibition mechanism has prevented their translation to the clinics. In vivo, such a mechanism requires the unrealistic maintenance of the concentration above the binding constant. Recently, we have shown that the addition of long hydrophobic linkers to heparin-like compounds renders the interaction irreversible while maintaining the low-toxicity and broad-spectrum activity. To date, such hydrophobic linkers have been used to create heparin-like gold nanoparticles and ß-cyclodextrins. The former achieves a nanomolar inhibition concentration on a non-biodegradable scaffold. The latter, on a fully biodegradable scaffold, shows only a micromolar inhibition concentration. Here, we report that the addition of hydrophobic linkers to a new type of multifunctional scaffold (dendritic polyglycerol, dPG) creates biocompatible compounds endowed with nanomolar activity. Furthermore, we present an in-depth analysis of the molecular design rules needed to achieve irreversible virus inhibition. The most active compound (dPG-5) showed nanomolar activity against herpes simplex virus 2 (HSV-2) and respiratory syncytial virus (RSV), giving a proof-of-principle for broad-spectrum while keeping low-toxicity. In addition, we demonstrate that the virucidal activity leads to the release of viral DNA upon the interaction between the virus and our polyanionic dendritic polymers. We believe that this paper will be a stepping stone toward the design of a new class of irreversible nontoxic broad-spectrum antivirals.

Broad-spectrum nanoparticles against bacteriophage infections.

Viral infections caused by bacteriophages, i.e., viruses that kill bacteria are one of the most dangerous and common threats for bacteria-based bioreactors. More than 70% of biotechnology companies have admitted to encountering this problem. Despite phage infections being such a dangerous and widespread risk, there are no effective methods to avoid them to date. Herein, we present a novel technology based on nanoparticles that irreversibly deactivates bacteriophages and is safe for bacteria. Our method allows for the unsupervised protection of bacterial processes in the biotechnology industry. Gold nanoparticles coated with a mixture of negatively charged 11-mercapto 1-undecanesulfonic acid (MUS) and hydrophobic 1-octanethiol (OT) ligands are effective at deactivating various types of Escherichia coli-selective phages: T1, T4, and T7. The nanoparticles can lower the titer of phages up to 2 and 5 logs in 6 and 24 h at 50 °C, respectively. A comparative analysis of nanoparticles with different ligand shells illustrates the importance of the combination of negatively charged and hydrophobic ligands that is the key to achieving a good inhibitory concentration (EC50 ≤ 1 µg mL-1) for all tested phages. We show that the nanoparticles are harmless for the commonly used bacteria in industry Escherichia coli and are effective under conditions simulating the environment of bioreactors.

Cholesterol Hinders the Passive Uptake of Amphiphilic Nanoparticles into Fluid Lipid Membranes.

Plasma membranes represent pharmacokinetic barriers for the passive transport of site-specific drugs within cells. When engineered nanoparticles (NPs) are considered as transmembrane drug carriers, the plasma membrane composition can affect passive NP internalization in many ways. Among these, cholesterol-regulated membrane fluidity is probably one of the most biologically relevant. Herein, we consider small (2-5 nm in core diameter) amphiphilic gold NPs capable of spontaneously and nondisruptively entering the lipid bilayer of plasma membranes. We study their incorporation into model 1,2-dioleoyl-sn-glycero-3-phosphocholine membranes with increasing cholesterol content. We combine dissipative quartz crystal microbalance experiments, atomic force microscopy, and molecular dynamics simulations to show that membrane cholesterol, at biologically relevant concentrations, hinders the molecular mechanism for passive NP penetration within fluid bilayers, resulting in a dramatic reduction in the amount of NP incorporated.

An antiviral trap made of protein nanofibrils and iron oxyhydroxide nanoparticles.

Minimizing the spread of viruses in the environment is the first defence line when fighting outbreaks and pandemics, but the current COVID-19 pandemic demonstrates how difficult this is on a global scale, particularly in a sustainable and environmentally friendly way. Here we introduce and develop a sustainable and biodegradable antiviral filtration membrane composed of amyloid nanofibrils made from food-grade milk proteins and iron oxyhydroxide nanoparticles synthesized in situ from iron salts by simple pH tuning. Thus, all the membrane components are made of environmentally friendly, non-toxic and widely available materials. The membrane has outstanding efficacy against a broad range of viruses, which include enveloped, non-enveloped, airborne and waterborne viruses, such as SARS-CoV-2, H1N1 (the influenza A virus strain responsible for the swine flu pandemic in 2009) and enterovirus 71 (a non-enveloped virus resistant to harsh conditions, such as highly acidic pH), which highlights a possible role in fighting the current and future viral outbreaks and pandemics.

Advances in the development of entry inhibitors for sialic-acid-targeting viruses.

Over the past decades, several antiviral drugs have been developed to treat a range of infections. Yet the number of treatable viral infections is still limited, and resistance to current drug regimens is an ever-growing problem. Therefore, additional strategies are needed to provide a rapid cure for infected individuals. An interesting target for antiviral drugs is the process of viral attachment and entry into the cell. Although most viruses use distinct host receptors for attachment to the target cell, some viruses share receptors, of which sialic acids are a common example. This review aims to give an update on entry inhibitors for a range of sialic-acid-targeting viruses and provides insight into the prospects for those with broad-spectrum potential.

SARS-CoV-2 Inhibition by Sulfonated Compounds.

Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) depends on angiotensin converting enzyme 2 (ACE2) for cellular entry, but it might also rely on attachment receptors such as heparan sulfates. Several groups have recently demonstrated an affinity of the SARS-CoV2 spike protein for heparan sulfates and a reduced binding to cells in the presence of heparin or heparinase treatment. Here, we investigated the inhibitory activity of several sulfated and sulfonated molecules, which prevent interaction with heparan sulfates, against vesicular stomatitis virus (VSV)-pseudotyped-SARS-CoV-2 and the authentic SARS-CoV-2. Sulfonated cyclodextrins and nanoparticles that have recently shown broad-spectrum non-toxic virucidal activity against many heparan sulfates binding viruses showed inhibitory activity in the micromolar and nanomolar ranges, respectively. In stark contrast with the mechanisms that these compounds present for these other viruses, the inhibition against SARS-CoV-2 was found to be simply reversible.

Sulfonated Nanomaterials with Broad-Spectrum Antiviral Activity Extending beyond Heparan Sulfate-Dependent Viruses.

Viral infections are among the main causes of death worldwide, and we lack antivirals for the majority of viruses. Heparin-like sulfated or sulfonated compounds have been known for decades for their ability to prevent infection by heparan sulfate proteoglycan (HSPG)-dependent viruses but only in a reversible way. We have previously shown that gold nanoparticles and ß-cyclodextrins coated with mercapto-undecane sulfonic acid (MUS) inhibit HSPG-dependent viruses irreversibly while retaining the low-toxicity profile of most heparin-like compounds. In this work, we show that, in stark contrast to heparin, these compounds also inhibit different strains of influenza virus and vesicular stomatitis virus (VSV), which do not bind HSPG. The antiviral action is virucidal and irreversible for influenza A virus (H1N1), while for VSV, there is a reversible inhibition of viral attachment to the cell. These results further broaden the spectrum of activity of MUS-coated gold nanoparticles and ß-cyclodextrins.

Modified cyclodextrins as broad-spectrum antivirals.

Viral infections kill millions of people and new antivirals are needed. Nontoxic drugs that irreversibly inhibit viruses (virucidal) are postulated to be ideal. Unfortunately, all virucidal molecules described to date are cytotoxic. We recently developed nontoxic, broad-spectrum virucidal gold nanoparticles. Here, we develop further the concept and describe cyclodextrins, modified with mercaptoundecane sulfonic acids, to mimic heparan sulfates and to provide the key nontoxic virucidal action. We show that the resulting macromolecules are broad-spectrum, biocompatible, and virucidal at micromolar concentrations in vitro against many viruses [including herpes simplex virus (HSV), respiratory syncytial virus (RSV), dengue virus, and Zika virus]. They are effective ex vivo against both laboratory and clinical strains of RSV and HSV-2 in respiratory and vaginal tissue culture models, respectively. Additionally, they are effective when administrated in mice before intravaginal HSV-2 inoculation. Lastly, they pass a mutation resistance test that the currently available anti-HSV drug (acyclovir) fails.

Synthesis and Characterization of Amphiphilic Gold Nanoparticles.

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.