Herpes Simplex Virus type 1 inhibits autophagy in glial cells but requires ATG5 for the success of viral replication.

Herpes Simplex Virus type 1 (HSV-1) 1 is a neurotropic virus that has been associated with neurodegenerative disorders. The dysregulation of autophagy by HSV-1 has been proposed as a potential cause of neurodegeneration. While studies have extensively tackled the interaction between autophagy and HSV-1 in neurons, research in glial cells is currently limited. Our studies demonstrate that HSV-1 inhibits, but not completely blocks, the formation of autophagosomes in human oligodendroglioma- and astrocytoma- derived cell lines. These findings have been confirmed in murine oligodendrocyte precursor cells (OPCs). Finally, this study investigates the impact of autophagy on HSV-1 infection in glial cells. While the lack of basal autophagy in LC3B knockout glial cells does not have a significant effect on viral infection, cells without the autophagy-related protein ATG5 exhibit reduced viral production. The absence of ATG5 leads to a decrease in the transcription and replication of viral genes, as well as a delay in the initial stages of the formation of HSV-1 replication compartments. These findings indicate that while autophagy may not play a significant role in antiviral defense in glial cells, HSV-1 may be inhibiting autophagy to exploit non-canonical functions of certain components of the autophagic machinery, such as ATG5, to benefit its lifecycle.

Pseudorabies virus uses clathrin mediated endocytosis to enter PK15 swine cell line.

Pseudorabies virus (PRV), a herpesvirus responsible for Aujeszky's disease, causes high mortality in swine populations. To develop effective and novel antiviral strategies, it is essential to understand the mechanism of entry used by PRV to infect its host. Viruses have different ways of entering host cells. Among others, they can use endocytosis, a fundamental cellular process by which substances from the external environment are internalized into the cell. This process is classified into clathrin-mediated endocytosis (CME) and clathrin-independent endocytosis (CIE), depending on the role of clathrin. Although the involvement of cholesterol-rich lipid rafts in the entry of PRV has already been described, the importance of other endocytic pathways involving clathrin remains unexplored to date. Here, we characterize the role of CME in PRV entry into the PK15 swine cell line. By using CME inhibitory drugs, we report a decrease in PRV infection when the CME pathway is blocked. We also perform the shRNA knockdown of the µ-subunit of the adaptor protein AP-2 (AP2M1), which plays an important role in the maturation of clathrin-coated vesicles, and the infection is greatly reduced when this subunit is knocked down. Furthermore, transmission electron microscopy images report PRV virions inside clathrin-coated vesicles. Overall, this study suggests for the first time that CME is a mechanism used by PRV to enter PK15 cells and provides valuable insights into its possible routes of entry.

Dextran sulfate from Leuconostoc mesenteroides B512F exerts potent antiviral activity against SARS-CoV-2 in vitro and in vivo.

The emergent human coronavirus SARS-CoV-2 and its resistance to current drugs makes the need for new potent treatments for COVID-19 patients strongly necessary. Dextran sulfate (DS) polysaccharides have long demonstrated antiviral activity against different enveloped viruses in vitro. However, their poor bioavailability has led to their abandonment as antiviral candidates. Here, we report for the first time the broad-spectrum antiviral activity of a DS-based extrapolymeric substance produced by the lactic acid bacterium Leuconostoc mesenteroides B512F. Time of addition assays with SARS-CoV-2 pseudoviruses in in vitro models confirm the inhibitory activity of DSs in the early stages of viral infection (viral entry). In addition, this exopolysaccharide substance also reports broad-spectrum antiviral activity against several enveloped viruses such as SARS-CoV-2, HCoV229E, HSV-1, in in vitro models and in human lung tissue. The toxicity and antiviral capacity of DS from L. mesenteroides was tested in vivo in mouse models which are susceptible to SARS-CoV-2 infection. The described DS, administered by inhalation, a new route of administration for these types of polymers, shows strong inhibition of SARS-CoV-2 infection in vivo, significantly reducing animal mortality and morbidity at non-toxic doses. Therefore, we suggest that it may be considered as a potential candidate for antiviral therapy against SARS-CoV-2.

Liposomal Lactoferrin Exerts Antiviral Activity against HCoV-229E and SARS-CoV-2 Pseudoviruses In Vitro.

A limited number of effective therapies are currently available to treat human coronavirus SARS-CoV-2 and other human coronaviruses, which are responsible for nearly a third of global cases of the common cold. The possibility of new emerging coronaviruses demands powerful new antiviral strategies. Lactoferrin is a well-known protein that possesses anti-inflammatory and immunomodulatory activities, and it has previously shown antiviral activity against several viruses, including SARS-CoV-2. To increase this antiviral activity, here we present bovine liposomal lactoferrin. Liposomal encapsulation of the compound was proven to increase permeability, bioavailability, and time release. In the present work, we compare the antiviral activity of free and liposomal bovine lactoferrin against HCoV229E and SARS-CoV-2 in vitro and in human primary bronchial epithelial cells, and we demonstrated that the liposomal form exerts a more potent antiviral activity than its free form at non-cytotoxic doses.

Interplay between Autophagy and Herpes Simplex Virus Type 1: ICP34.5, One of the Main Actors.

Herpes simplex virus type 1 (HSV-1) is a neurotropic virus that occasionally may spread to the central nervous system (CNS), being the most common cause of sporadic encephalitis. One of the main neurovirulence factors of HSV-1 is the protein ICP34.5, which although it initially seems to be relevant only in neuronal infections, it can also promote viral replication in non-neuronal cells. New ICP34.5 functions have been discovered during recent years, and some of them have been questioned. This review describes the mechanisms of ICP34.5 to control cellular antiviral responses and debates its most controversial functions. One of the most discussed roles of ICP34.5 is autophagy inhibition. Although autophagy is considered a defense mechanism against viral infections, current evidence suggests that this antiviral function is only one side of the coin. Different types of autophagic pathways interact with HSV-1 impairing or enhancing the infection, and both the virus and the host cell modulate these pathways to tip the scales in its favor. In this review, we summarize the recent progress on the interplay between autophagy and HSV-1, focusing on the intricate role of ICP34.5 in the modulation of this pathway to fight the battle against cellular defenses.

Potent Virucidal Activity In Vitro of Photodynamic Therapy with Hypericum Extract as Photosensitizer and White Light against Human Coronavirus HCoV-229E.

The emergent human coronavirus SARS-CoV-2 and its high infectivity rate has highlighted the strong need for new virucidal treatments. In this sense, the use of photodynamic therapy (PDT) with white light, to take advantage of the sunlight, is a potent strategy for decreasing the virulence and pathogenicity of the virus. Here, we report the virucidal effect of PDT based on Hypericum extract (HE) in combination with white light, which exhibits an inhibitory activity of the human coronavirus HCoV-229E on hepatocarcinoma Huh-7 cells. Moreover, despite continuous exposure to white light, HE has long durability, being able to maintain the prevention of viral infection. Given its potent in vitro virucidal capacity, we propose HE in combination with white light as a promising candidate to fight against SARS-CoV-2 as a virucidal compound.

Extracellular Polymeric Substances: Still Promising Antivirals.

Sulfated polysaccharides and other polyanions have been promising candidates in antiviral research for decades. These substances gained attention as antivirals when they demonstrated a high inhibitory effect in vitro against human immunodeficiency virus (HIV) and other enveloped viruses. However, that initial interest was followed by wide skepticism when in vivo assays refuted the initial results. In this paper we review the use of sulfated polysaccharides, and other polyanions, in antiviral therapy, focusing on extracellular polymeric substances (EPSs). We maintain that, in spite of those early difficulties, the use of polyanions and, specifically, the use of EPSs, in antiviral therapy should be reconsidered. We base our claim in several points. First, early studies showed that the main disadvantage of sulfated polysaccharides and polyanions is their low bioavailability, but this difficulty can be overcome by the use of adequate administration strategies, such as nebulization of aerosols to gain access to respiratory airways. Second, several sulfated polysaccharides and EPSs have demonstrated to be non-toxic in animals. Finally, these macromolecules are non-specific and therefore they might be used against different variants or even different viruses.

The Valproic Acid Derivative Valpromide Inhibits Pseudorabies Virus Infection in Swine Epithelial and Mouse Neuroblastoma Cell Lines.

Pseudorabies virus (PRV) infection of swine can produce Aujeszky's disease, which causes neurological, respiratory, and reproductive symptoms, leading to significant economic losses in the swine industry. Although humans are not the natural hosts of PRV, cases of human encephalitis and endophthalmitis caused by PRV infection have been reported between animals and workers. Currently, a lack of specific treatments and the emergence of new PRV strains against which existing vaccines do not protect makes the search for effective antiviral drugs essential. As an alternative to traditional nucleoside analogues such as acyclovir (ACV), we studied the antiviral effect of valpromide (VPD), a compound derived from valproic acid, against PRV infection in the PK15 swine cell line and the neuroblastoma cell line Neuro-2a. First, the cytotoxicity of ACV and VPD in cells was compared, demonstrating that neither compound was cytotoxic at a specific concentration range after 24 h exposure. Furthermore, the lack of direct virucidal effect of VPD outside of an infected cell environment was demonstrated. Finally, VPD was shown to have an antiviral effect on the viral production of two strains of pseudorabies virus (wild type NIA-3 and recombinant PRV-XGF) at the concentrations ranging from 0.5 to 1.5 mM, suggesting that VPD could be a suitable alternative to nucleoside analogues as an antiherpetic drug against Aujeszky's disease.

HSV-1 and Endogenous Retroviruses as Risk Factors in Demyelination.

Herpes simplex virus type 1 (HSV-1) is a neurotropic alphaherpesvirus that can infect the peripheral and central nervous systems, and it has been implicated in demyelinating and neurodegenerative processes. Transposable elements (TEs) are DNA sequences that can move from one genomic location to another. TEs have been linked to several diseases affecting the central nervous system (CNS), including multiple sclerosis (MS), a demyelinating disease of unknown etiology influenced by genetic and environmental factors. Exogenous viral transactivators may activate certain retrotransposons or class I TEs. In this context, several herpesviruses have been linked to MS, and one of them, HSV-1, might act as a risk factor by mediating processes such as molecular mimicry, remyelination, and activity of endogenous retroviruses (ERVs). Several herpesviruses have been involved in the regulation of human ERVs (HERVs), and HSV-1 in particular can modulate HERVs in cells involved in MS pathogenesis. This review exposes current knowledge about the relationship between HSV-1 and human ERVs, focusing on their contribution as a risk factor for MS.

Nebulized CLODOS Technology Shows Clear Virucidal Properties against the Human Coronavirus HCoV-229E at Non-Cytotoxic Doses.

The emergent human coronavirus SARS-CoV-2 and its high infectivity rate has highlighted the strong need for new disinfection systems. Evidence has proven that airborne transmission is an important route of spreading for this virus. Therefore, this short communication introduces CLODOS Technology®, a novel strategy to disinfect contaminated surfaces. It is a product based on stable and 99% pure chlorine dioxide, already certified as a bactericide, fungicide and virucide against different pathogens. In this study, CLODOS Technology®, by direct contact or thermonebulization, showed virucidal activity against the human coronavirus HCoV-229E at non-cytotoxic doses. Different conditions such as nebulization, exposure time and product concentration have been tested to standardize and optimize this new feasible method for disinfection.

Membrane Rafts: Portals for Viral Entry.

Membrane rafts are dynamic, small (10-200 nm) domains enriched with cholesterol and sphingolipids that compartmentalize cellular processes. Rafts participate in roles essential to the lifecycle of different viral families including virus entry, assembly and/or budding events. Rafts seem to participate in virus attachment and recruitment to the cell surface, as well as the endocytic and non-endocytic mechanisms some viruses use to enter host cells. In this review, we will introduce the specific role of rafts in viral entry and define cellular factors implied in the choice of one entry pathway over the others. Finally, we will summarize the most relevant information about raft participation in the entry process of enveloped and non-enveloped viruses.

The Role of Extracellular Vesicles in Demyelination of the Central Nervous System.

It is being increasingly demonstrated that extracellular vesicles (EVs) are deeply involved in the physiology of the central nervous system (CNS). Processes such as synaptic activity, neuron-glia communication, myelination and immune response are modulated by EVs. Likewise, these vesicles may participate in many pathological processes, both as triggers of disease or, on the contrary, as mechanisms of repair. EVs play relevant roles in neurodegenerative disorders such as Alzheimer's or Parkinson's diseases, in viral infections of the CNS and in demyelinating pathologies such as multiple sclerosis (MS). This review describes the involvement of these membrane vesicles in major demyelinating diseases, including MS, neuromyelitis optica, progressive multifocal leukoencephalopathy and demyelination associated to herpesviruses.

Valproic Acid and Its Amidic Derivatives as New Antivirals against Alphaherpesviruses.

Herpes simplex viruses (HSVs) are neurotropic viruses with broad host range whose infections cause considerable health problems in both animals and humans. In fact, 67% of the global population under the age of 50 are infected with HSV-1 and 13% have clinically recurrent HSV-2 infections. The most prescribed antiherpetics are nucleoside analogues such as acyclovir, but the emergence of mutants resistant to these drugs and the lack of available vaccines against human HSVs has led to an imminent need for new antivirals. Valproic acid (VPA) is a branched short-chain fatty acid clinically used as a broad-spectrum antiepileptic drug in the treatment of neurological disorders, which has shown promising antiviral activity against some herpesviruses. Moreover, its amidic derivatives valpromide and valnoctamide also share this antiherpetic activity. This review summarizes the current research on the use of VPA and its amidic derivatives as alternatives to traditional antiherpetics in the fight against HSV infections.

The Role of Herpes Simplex Virus Type 1 Infection in Demyelination of the Central Nervous System.

Herpes simplex type 1 (HSV-1) is a neurotropic virus that infects the peripheral and central nervous systems. After primary infection in epithelial cells, HSV-1 spreads retrogradely to the peripheral nervous system (PNS), where it establishes a latent infection in the trigeminal ganglia (TG). The virus can reactivate from the latent state, traveling anterogradely along the axon and replicating in the local surrounding tissue. Occasionally, HSV-1 may spread trans-synaptically from the TG to the brainstem, from where it may disseminate to higher areas of the central nervous system (CNS). It is not completely understood how HSV-1 reaches the CNS, although the most accepted idea is retrograde transport through the trigeminal or olfactory tracts. Once in the CNS, HSV-1 may induce demyelination, either as a direct trigger or as a risk factor, modulating processes such as remyelination, regulation of endogenous retroviruses, or molecular mimicry. In this review, we describe the current knowledge about the involvement of HSV-1 in demyelination, describing the pathways used by this herpesvirus to spread throughout the CNS and discussing the data that suggest its implication in demyelinating processes.