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

Isolation, structural determination, and antiviral activities of a novel alanine-conjugated polyketide from Talaromyces sp

Antiviral agents are highly sought after. In this study, a novel alkylated decalin-type polyketide, alaspelunin, was isolated from the culture broth of the fungus Talaromyces speluncarum FMR 16671, and its structure was determined using spectroscopic analyses (1D/2D NMR and MS). The compound was condensed with alanine, and its absolute configuration was determined using Marfey's method. Furthermore, the antiviral activity of alaspelunin against various viruses was evaluated, and it was found to be effective against both severe acute respiratory syndrome coronavirus 2 and pseudorabies (Aujeszky's disease) virus, a pathogen affecting pigs. Our results suggest that this compound is a potential broad-spectrum antiviral agent.

Brincidofovir Effectively Inhibits Proliferation of Pseudorabies Virus by Disrupting Viral Replication

Pseudorabies is an acute and febrile infectious disease caused by pseudorabies virus (PRV), a member of the family Herpesviridae. Currently, PRV is predominantly endemoepidemic and has caused significant economic losses among domestic pigs. Other animals have been proven to be susceptible to PRV, with a mortality rate of 100%. In addition, 30 human cases of PRV infection have been reported in China since 2017, and all patients have shown severe neurological symptoms and eventually died or developed various neurological sequelae. In these cases, broad-spectrum anti-herpesvirus drugs and integrated treatments were mostly applied. However, the inhibitory effect of the commonly used anti-herpesvirus drugs (e.g., acyclovir, etc.) against PRV were evaluated and found to be limited in this study. It is therefore urgent and important to develop drugs that are clinically effective against PRV infection. Here, we constructed a high-throughput method for screening antiviral drugs based on fluorescence-tagged PRV strains and multi-modal microplate readers that detect fluorescence intensity to account for virus proliferation. A total of 2104 small molecule drugs approved by the U.S. Food and Drug Administration (FDA) were studied and validated by applying this screening model, and 104 drugs providing more than 75% inhibition of fluorescence intensity were selected. Furthermore, 10 drugs that could significantly inhibit PRV proliferation in vitro were strictly identified based on their cytopathic effects, virus titer, and viral gene expression, etc. Based on the determined 50% cytotoxic concentration (CC50) and 50% inhibitory concentration (IC50), the selectivity index (SI) was calculated to be 26.3-3937.2 for these 10 drugs, indicating excellent drugability. The antiviral effects of the 10 drugs were then assessed in a mouse model. It was found that 10 mg/kg brincidofovir administered continuously for 5 days provided 100% protection in mice challenged with lethal doses of the human-origin PRV strain hSD-1/2019. Brincidofovir significantly attenuated symptoms and pathological changes in infected mice. Additionally, time-of-addition experiments confirmed that brincidofovir inhibited the proliferation of PRV mainly by interfering with the viral replication stage. Therefore, this study confirms that brincidofovir can significantly inhibit PRV both in vitro and in vivo and is expected to be an effective drug candidate for the clinical treatment of PRV infections.

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.

Secondary metabolites of Bacillus subtilis L2 show antiviral activity against pseudorabies virus

Bacillus subtilis (B. subtilis) is a commercially important probiotic known to produce secondary metabolites with antibacterial, antifungal and anti-inflammatory activities. However, the potential ability of B. subtilis to combat viruses, especially DNA viruses, has not been extensively investigated. In this study, we identified two distinct B. subtilis strains and examined the efficiency of their secondary metabolites against pseudorabies virus (PRV), a swine herpesvirus resulting in economic losses worldwide. We found that treatment with the secondary metabolites of B. subtilis L2, but not the metabolites of B. subtilis V11, significantly inhibited PRV replication in multiple cells. Notably, the antiviral activity of the metabolites of B. subtilis L2 was thermal stable, resistant to protease digestion. Moreover, these metabolites effectively impeded PRV binding, entry and replication. Importantly, oral administration of the metabolites of B. subtilis L2 protected mice from lethal PRV infection, rescuing weight loss and reducing the viral load in vivo. In summary, our results reveal that the metabolites of B. subtilis L2 exhibit anti-PRV activity both in vitro and in vivo, providing a potential candidate for novel antiviral drugs.

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.

Antiviral Activity of Benzoheterocyclic Compounds from Soil-Derived Streptomyces jiujiangensis NBERC-24992

Pseudorabies virus (PRV) is a pathogen that causes Aujeszky's disease (AD) in animals, leading to huge economic losses to swine farms. In order to discover anti-PRV compounds, we studied the extracts of the strain Streptomyces jiujiangensis NBERC-24992, which showed significant anti-PRV activity. Eight benzoheterocyclic secondary metabolites, including three new compounds (1-3, virantmycins D-G) and five known compounds (4-8, virantmycin, A-503451 D, A-503451 D acetylate, A-503451 A, and A-503451 B), were isolated from the broth of NBERC-24992. The structures of the new compounds were identified by using extensive spectroscopic data, including mass spectrometry (MS), nuclear magnetic resonance (NMR), and electronic circular dichroism (ECD). Compound 1 was found to be a novel heterocyclic compound with a tricyclic skeleton from natural product. All compounds were tested for antiviral activity, and 4 (virantmycin) showed an excellent effect against PRV and was better than ribavirin and acyclovir. Our study revealed that chlorine atom and tetrahydroquinoline skeleton were important active moiety for antiviral activity. Virantmycin could be a suitable leading compound for an antiviral drug against PRV.

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.

Progress of Research into Novel Drugs and Potential Drug Targets against Porcine Pseudorabies Virus

Pseudorabies virus (PRV) is the causative agent of pseudorabies (PR), infecting most mammals and some birds. It has been prevalent around the world and caused huge economic losses to the swine industry since its discovery. At present, the prevention of PRV is mainly through vaccination; there are few specific antivirals against PRV, but it is possible to treat PRV infection effectively with drugs. In recent years, some drugs have been reported to treat PR; however, the variety of anti-pseudorabies drugs is limited, and the underlying mechanism of the antiviral effect of some drugs is unclear. Therefore, it is necessary to explore new drug targets for PRV and develop economic and efficient drug resources for prevention and control of PRV. This review will focus on the research progress in drugs and drug targets against PRV in recent years, and discuss the future research prospects of anti-PRV drugs.

Characterization of B cell receptor H-CDR3 repertoire of spleen in PRV-infected mice

Pseudorabies virus (PRV), also known as suid Alphaherpesvirus 1 (SuHV-1), which is one of the most devastating infectious pathogen of swine industry worldwide. Vaccination is the safest and most effective PRV prevention and control strategy. B cell receptor (BCR) is membrane-bound immunoglobulin located on the surface of B cells capable of specifically binding foreign antigens, which is one of the most important molecules regulating the proliferation and function of B cells. Here, to assess the molecular diversity of BCR H-CDR3 repertoire after different PRV strains infection, we detected the IGHV, IGHD, IGHJ genes usage and CDR3 sequence changes of mice spleen with PRV vaccine strain (Bartha-K61), variant strain (XJ) and mock infection by high-throughput sequencing. We found that PRV-infected groups shared partial BCR sequences, which are most likely to be PRV-specific BCR candidates. However, there were still differences in the IGHV genes usage as well as the combined usage of IGHV and IGHJ genes between the Bartha-K61 strain and XJ strain infection groups. In addition, the CDR3 sequences exhibited large differences in the types and lengths in PRV infection groups. Our study contributes to a better understanding of the host adaptive immune response to PRV infection and provides a theoretical basis for further research on novel and efficient PRV vaccines in the future.