The 40 kDa Linear Polyethylenimine Inhibits Porcine Reproductive and Respiratory Syndrome Virus Infection by Blocking Its Attachment to Permissive Cells. Viruses. 2019;11. [PMID: 31546799 PMCID: PMC6784015 DOI: 10.3390/v11090876]

The 25-kDa linear polyethylenimine exerts specific antiviral activity against pseudorabies virus through interferencing its adsorption via electrostatic interaction

Pseudorabies virus (PRV) is the causative agent of Aujeszky's disease, which is responsible for enormous economic losses to the global pig industry. Although vaccination has been used to prevent PRV infection, the effectiveness of vaccines has been greatly diminished with the emergence of PRV variants. Therefore, there is an urgent need to develop anti-PRV drugs. Polyethylenimine (PEI) is a cationic polymer and has a wide range of antibacterial and antiviral activities. This study found that a low dose of 1 µg/mL of the 25-kDa linear PEI had significantly specific anti-PRV activity, which became more intense with increasing concentrations. Mechanistic studies revealed that the viral adsorption stage was the major target of PEI without affecting viral entry, replication stages, and direct inactivation effects. Subsequently, we found that cationic polymers PEI and Polybrene interfered with the interaction between viral proteins and cell surface receptors through electrostatic interaction to exert the antiviral function. In conclusion, cationic polymers such as PEI can be a category of options for defense against PRV. Understanding the anti-PRV mechanism also deepens host-virus interactions and reveals new drug targets for anti-PRV.IMPORTANCEPolyethylenimine (PEI) is a cationic polymer that plays an essential role in the host immune response against microbial infections. However, the specific mechanisms of PEI in interfering with pseudorabies virus (PRV) infection remain unclear. Here, we found that 25-kDa linear PEI exerted mechanisms of antiviral activity and the target of its antiviral activity was mainly in the viral adsorption stage. Correspondingly, the study demonstrated that PEI interfered with the virus adsorption stage by electrostatic adsorption. In addition, we found that cationic polymers are a promising novel agent for controlling PRV, and its antiviral mechanism may provide a strategy for the development of antiviral drugs.

Amino acid pattern reveals multi-functionality of ORF3 protein from HEV

The smallest open reading frame (ORF) encoded protein ORF3 of hepatitis E virus (HEV), recently, has been demonstrated to perform multiple functions besides accessory roles. ORF3 could act as a target for vaccine against HEV infections. The IDR (intrinsically disordered region); IDP (ID protein)/IDPR (ID protein region), plays critical role in various regulatory functions of viruses. The dark proteome of HEV-ORF3 protein including its structure and function was systematically examined by computer predictors to explicate its role in viral pathogenesis and drug resistance beyond its functions as accessory viral protein. Amino acid distribution showed ORF3 enrichment with disorder-promoting residues (Ala, Pro, Ser, Gly) while deficiency in order-promoting residues (Asn, Ile, Phe, Tyr and Trp). Initial investigation revealed ORF3 as IDP (entirely disordered protein) or IDPR (proteins consisting of IDRs with structured globular domains). Structural examination revealed preponderance of disordered regions interpreting ORF3 as moderately/highly disordered protein. Further disorder predictors categorized ORF3 as highly disordered protein/IDP. Identified sites and associated-crucial molecular functions revealed ORF3 involvement in diverse biological processes, substantiating them as targets of regulation. As ORF3 functions are yet to completely explored, thus, data on its disorderness could help in elucidating its disorder related functions.

Anti-Viral Surfaces in the Fight against the Spread of Coronaviruses

This review is conducted against the background of nanotechnology, which provides us with a chance to effectively combat the spread of coronaviruses, and which primarily concerns polyelectrolytes and their usability for obtaining protective function against viruses and as carriers for anti-viral agents, vaccine adjuvants, and, in particular, direct anti-viral activity. This review covers nanomembranes in the form of nano-coatings or nanoparticles built of natural or synthetic polyelectrolytes--either alone or else as nanocomposites for creating an interface with viruses. There are not a wide variety of polyelectrolytes with direct activity against SARS-CoV-2, but materials that are effective in virucidal evaluations against HIV, SARS-CoV, and MERS-CoV are taken into account as potentially active against SARS-CoV-2. Developing new approaches to materials as interfaces with viruses will continue to be relevant in the future.

A porcine reproductive and respiratory syndrome virus (PRRSV)-specific IgM as a novel adjuvant for an inactivated PRRSV vaccine improves protection efficiency and enhances cell-mediated immunity against heterologous PRRSV challenge

Current strategies for porcine reproductive and respiratory syndrome (PRRS) control are inadequate and mainly restricted to immunization using different PRRS virus (PPRSV) vaccines. Although there are no safety concerns, the poor performance of inactivated PRRSV vaccines has restricted their practical application. In this research, we employed the novel PRRSV-specific IgM monoclonal antibody (Mab)-PR5nf1 as a vaccine adjuvant for the formulation of a cocktail composed of inactivated PRRSV (KIV) and Mab-PR5nf1 along with a normal adjuvant to enhance PRRSV-KIV vaccine-mediated protection and further compared it with a normal KIV vaccine and modified live virus vaccine (MLV). After challenge with highly pathogenic (HP)-PRRSV, our results suggested that the overall survival rate (OSR) and cell-mediated immunity (CMI), as determined by serum IFN-γ quantification and IFN-γ ELISpot assay, were significantly improved by adding PRRSV-specific IgM to the PRRSV-KIV vaccine. It was also notable that both the OSR and CMI in the Mab-PR5nf1-adjuvanted KIV group were even higher than those in the MLV group, whereas the CMI response is normally poorly evoked by KIV vaccines or subunit vaccines. Compared with those in piglets immunized with the normal KIV vaccine, viral shedding and serum neutralizing antibody levels were also improved, and reduced viral shedding appeared to be a result of enhanced CMI caused by the inclusion of IgM as an adjuvant. In conclusion, our data provide not only a new formula for the development of an effective PRRSV-KIV vaccine for practical use but also a novel method for improving antigen-specific CMI induction by inactivated vaccines and subunit vaccines.

Reappraising host cellular factors involved in attachment and entry to develop antiviral strategies against porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRS virus (PRRSV), is a highly contagious disease that brings tremendous economic losses to the global swine industry. As an intracellular obligate pathogen, PRRSV infects specific host cells to complete its replication cycle. PRRSV attachment to and entry into host cells are the first steps to initiate the replication cycle and involve multiple host cellular factors. In this review, we recapitulated recent advances on host cellular factors involved in PRRSV attachment and entry, and reappraised their functions in these two stages, which will deepen the understanding of PRRSV infection and provide insights to develop promising antiviral strategies against the virus.

Broad-Spectrum Antiviral Peptides and Polymers

As the human cost of the pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still being witnessed worldwide, the development of broad-spectrum antiviral agents against emerging and re-emerging viruses is seen as a necessity to hamper the spread of infections. Various targets during the viral life-cycle can be considered to inhibit viral infection, from viral attachment to viral fusion or replication. Macromolecules represent a particularly attractive class of therapeutics due to their multivalency and versatility. Although several antiviral macromolecules hold great promise in clinical applications, the emergence of resistance after prolonged exposure urges the need for improved solutions. In the present article, the recent advancement in the discovery of antiviral peptides and polymers with diverse structural features and antiviral mechanisms is reviewed. Future perspectives, such as, the development of virucidal peptides/polymers and their coatings against SARS-CoV-2 infection, standardization of antiviral testing protocols, and use of artificial intelligence or machine learning as a tool to accelerate the discovery of antiviral macromolecules, are discussed.

Open reading frame 3 protein of hepatitis E virus: Multi-function protein with endless potential

Hepatitis E virus (HEV), a fecal-orally transmitted foodborne viral pathogen, causes acute hepatitis in humans and is responsible for hepatitis E outbreaks worldwide. Since the identification of HEV as a zoonotic agent, this virus has been isolated from a variety of hosts with an ever-expanding host range. HEV-open reading frame (ORF) 3, the smallest ORF in HEV genomes, initially had been perceived as an unremarkable HEV accessory protein. However, as novel HEV-ORF3 function has been discovered that is related to the existence of a putative third virion structural form, referred to as “quasi-enveloped” HEV particles, HEV is challenging the conventional virion structure-based classification scheme, which assigns all viruses to two groups, “enveloped” or “non-enveloped”. In this review, we systematically describe recent progress that has identified multiple pathogenic roles of HEV-ORF3, including roles in HEV virion release, biogenesis of quasi-enveloped virus, regulation of the host innate immune response, and interference with host signaling pathways. In addition, implications of HEV-ORF3-associated quasi-enveloped virions are discussed to guide future development of improved vaccines against zoonotic HEV infection.

Recent Advances in PRRS Virus Receptors and the Targeting of Receptor-Ligand for Control

Cellular receptors play a critical role in viral infection. At least seven cellular molecules have been identified as putative viral entry mediators for porcine reproductive and respiratory syndrome virus (PRRSV). Accumulating data indicate that among these candidates, CD163, a cysteine-rich scavenger receptor on macrophages, is the major receptor for PRRSV. This review discusses the recent advances and understanding of the entry of PRRSV into cells, viral pathogenesis in CD163 gene-edited swine, and CD163 as a potential target of receptor–ligand for the control of PRRS.

Porcine reproductive and respiratory syndrome virus infection induces endoplasmic reticulum stress, facilitates virus replication, and contributes to autophagy and apoptosis

During viral infection, the host cell synthesizes high amounts of viral proteins, which often causes stress to the endoplasmic reticulum (ER). To manage abnormal ER stress, mammalian cells trigger a response called the unfolded protein response (UPR). Previous studies have indicated that porcine reproductive and respiratory syndrome virus (PRRSV), an Arterivirus that has been devastating the swine industry worldwide, can induce ER stress and activate UPR, however, the activation pathways and the biological significance requires further investigation. In this study, we demonstrated that, among the three types of UPR pathways, PRRSV infection induced PERK and IRE1 pathways, but not the ATF6 pathway. Furthermore, the induction of UPR promoted PRRSV replication. We also found that PRRSV-induced UPR, particularly the PERK pathway, was involved in the induction of autophagy, a cellular degradation process that can alleviate cell stress. Besides, we also provided insights into the ER stress-mediated apoptosis in response to PRRSV infection. PRRSV infection induced the expression of the transcription factor CHOP, which activated caspase 3 and PARP led to ER stress-mediated apoptosis. Using 3-Methyladenine (3-MA) to inhibit autophagy, the increased ER stress and cell apoptosis were observed in the PRRSV infected cell. Taken together, our results revealed the associations of ER stress, autophagy, and apoptosis during PRRSV infection, helping us to further understand how PRRSV interacts with host cells.