Reduced Virus Replication Research Articles

Robust and Long-Lasting Immunity and Protection in Mice Induced by Lipopolyplex-Delivered mRNA Vaccines Expressing the Prefusion Protein of Respiratory Syncytial Virus.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infants and children. mRNA vaccines based on the lipopolyplex (LPP) platform have been previously reported, but they remain unapplied in RSV vaccine development. In this study, we developed a novel LPP-delivered mRNA vaccine that expresses the respiratory syncytial virus prefusion protein (RSV pre-F) to evaluate its immunogenicity and protective effect in a mouse model. We synthesized mRNAs with gene modification for RSV pre-F and prepared mRNA vaccines using the LPP delivery platform, referred to as RSV pre-F LPP-mRNA. RSV pre-F protein expression in mRNA vaccines was characterized in vitro. Then, we evaluated the effects of the immune response and protection of this mRNA vaccine in mice up to 24 weeks post-vaccination. Following booster immunization, robust and long-lasting RSV pre-F-specific IgG antibodies were detected in the serum of mice, which exhibited Th1/Th2 balanced IgG response and cross-neutralizing antibodies against different subtypes (RSV A2, B18537, and clinical isolate hRSV/C-Tan/BJ 202301), with a clear dose-response relationship observed. RSV pre-F-specific IgG antibodies were maintained in the mice for an extended period, lasting up to 18 weeks post-immunization. Concurrently, multifunctional RSV F-specific CD8+ T cells (IFN-γ, IL-2, and TNF-α) were detected in the mice. After RSV A2 challenge, the RSV pre-F LPP-mRNA vaccine led to a significant reduction in viral replication, while reduced pathological damage was observed in lung tissue. The LPP-delivered mRNA vaccine expressing RSV pre-F induces a robust and long-lasting immune response and protection, indicating good prospects for further development and application.

GGCX promotes Eurasian avian-like H1N1 swine influenza virus adaption to interspecies receptor binding

The Eurasian avian-like (EA) H1N1 swine influenza virus (SIV) possesses the capacity to instigate the next influenza pandemic, owing to its heightened affinity for the human-type α-2,6 sialic acid (SA) receptor. Nevertheless, the molecular mechanisms underlying the switch in receptor binding preferences of EA H1N1 SIV remain elusive. In this study, we conduct a comprehensive genome-wide CRISPR/Cas9 knockout screen utilizing EA H1N1 SIV in porcine kidney cells. Knocking out the enzyme gamma glutamyl carboxylase (GGCX) reduces virus replication in vitro and in vivo by inhibiting the carboxylation modification of viral haemagglutinin (HA) and the adhesion of progeny viruses, ultimately impeding the replication of EA H1N1 SIV. Furthermore, GGCX is revealed to be the determinant of the D225E substitution of EA H1N1 SIV, and GGCX-medicated carboxylation modification of HA 225E contributes to the receptor binding adaption of EA H1N1 SIV to the α-2,6 SA receptor. Taken together, our CRISPR screen has elucidated a novel function of GGCX in the support of EA H1N1 SIV adaption for binding to α-2,6 SA receptor. Consequently, GGCX emerges as a prospective antiviral target against the infection and transmission of EA H1N1 SIV.

Selective suppression of influenza A/H5N1 virus replication <i>in vitro</i> using nanocomplexes consisting of siRNA and aminopropylsilanol nanoparticles

Relevance. Studies on model systems have confirmed the effectiveness of antisense oligonucleotides, including those that contain photoactive groups, for the modification of nucleic acids. However, this strategy has not yet found wide application due to the lack of successful methods for the intracellular delivery. The development of effective preparations capable of acting on target nucleic acids in cells is an urgent task. The aim of the study is to create nanocomplexes consisting of aminopropylsilanol nanoparticles and short interfering RNA (siRNA) to study their effect on target nucleic acids by the example of inhibition of influenza A virus replication in vitro. Materials and methods. MDCK cells, influenza virus A/chicken/Kurgan/05/2005 (A/H5N1), aminopropylsilanol nanoparticles, and native and modified siRNA molecules. Results and discussion. We have prepared unique Si~NH2/siRNA nanocomplexes, which consist of aminopropylsilanol nanoparticles and siRNA molecules, which enable cell penetration and selective interaction with target nucleic acids, respectively. The antiviral activity of the proposed nanocomplexes has been studied on MDCK cells infected with the influenza A/H5N1 virus. It has been shown that the double-stranded siRNA molecules in the nanocomplexes, which act by the RNA interference mechanism, are more efficient in inhibiting the replication of the influenza virus than the corresponding single-stranded RNA fragments. The most effective nanocomplex that contained siRNA targeted at the chosen region of mRNA segment 5 of the viral genome reduced virus replication in the culture by a factor of 630. We have shown that non-agglomerated and water-soluble aminopropylsilanol nanoparticles are low-toxic, capable of delivering siRNA into cells and protecting siRNA in the Si~NH2/siRNA nanocomplexes from hydrolysis by cellular nucleases. Conclusion. The biological activity of the created nanocomplexes has been demonstrated by the example of highly effective selective suppression of influenza A/chicken/Kurgan/05/2005 virus replication in the cellular system.

Effect of eicosapentaenoic acid on innate immune responses in Atlantic salmon cells infected with infectious salmon anemia virus

Aquaculture is one of the world's fastest-growing sectors in food production but with multiple challenges related to animal handling and infections. The disease caused by infectious salmon anemia virus (ISAV) leads to outbreaks of local epidemics, reducing animal welfare, and causing significant economic losses. The composition of feed has shifted from marine ingredients such as fish oil and fish meal towards a more plant-based diet causing reduced levels of eicosapentaenoic acid (EPA). The aim of this study was to investigate whether low or high levels of EPA affect the expression of genes related to the innate immune response 48 h after infection with ISAV. The study includes seven experimental groups: ± ISAV and various levels of EPA up to 200 µM. Analysis of RNA sequencing data showed that more than 3000 genes were affected by ISAV alone (without additional EPA). In cells with increasing levels of EPA, more than 2500 additional genes were differentially expressed. This indicates that high levels of EPA concentration have an independent effect on gene expression in virus-infected cells, not observed at lower levels of EPA. Analyses of enriched biological processes and molecular functions (GO and KEGG analysis) revealed that EPA had a limited impact on the innate immune system alone, but that many processes were affected by EPA when cells were virus infected. Several biological pathways were affected, including protein synthesis (ribosomal transcripts), peroxisome proliferator activated receptor (PPAR) signaling, and ferroptosis. Cells exposed to both increasing concentrations of EPA and virus displayed gene expression patterns indicating increased formation of oxygen radicals and that cell death via ferroptosis was activated. This gene expression pattern was not observed during infection at low EPA levels or when Atlantic salmon kidney (ASK) cells were exposed to the highest EPA level (200 μM) without virus infection. Cell death via ferroptosis may therefore be a mechanism for controlled cell death and thus reduction of virus replication when there are enough polyunsaturated fatty acids (PUFAs) in the membrane.

Exploiting the Achilles' Heel of Viral RNA Processing to Develop Novel Antivirals.

Treatment options for viral infections are limited and viruses have proven adept at evolving resistance to many existing therapies, highlighting a significant vulnerability in our defenses. In response to this challenge, we explored the modulation of cellular RNA metabolic processes as an alternative paradigm to antiviral development. Previously, the small molecule 5342191 was identified as a potent inhibitor of HIV-1 replication by altering viral RNA accumulation at doses that minimally affect host gene expression. In this report, we document 5342191 as a potent inhibitor of adenovirus, coronavirus, and influenza replication. In each case, 5342191-mediated reduction in virus replication was associated with altered viral RNA accumulation and loss of viral structural protein expression. Interestingly, while resistant viruses were rapidly isolated for compounds targeting either virus-encoded proteases or polymerases, we have not yet isolated 5342191-resistant variants of coronavirus or influenza. As with HIV-1, 5342191's inhibition of coronaviruses and influenza is mediated through the activation of specific cell signaling networks, including GPCR and/or MAPK signaling pathways that ultimately affect SR kinase expression. Together, these studies highlight the therapeutic potential of compounds that target cellular processes essential for the replication of multiple viruses. Not only do these compounds hold promise as broad-spectrum antivirals, but they also offer the potential of greater resilience in combating viral infections.

Role of Vigilin and RACK1 in dengue virus-Aedes aegypti-Wolbachia interactions.

Vigilin is a large and evolutionary conserved RNA-binding protein (RBP), which can interact with RNA through its KH domain. Vigilin is, therefore, a multifunctional protein reported to be associated with RNA transport and metabolism, sterol metabolism, chromosome segregation, carcinogenesis, and heterochromatin-mediated gene silencing. The receptor for activated C kinase 1 (RACK1) is another highly conserved protein involved in many cellular pathways. Functional studies in human cells indicated that RACK1 interacts with Vigilin to promote dengue virus (DENV) replication. Both proteins are associated with the endoplasmic reticulum. Here, we investigated the significance of Vigilin and RACK1 homologs in Aedes aegypti mosquitoes concerning DENV replication and Wolbachia infection. We identified the homologs of the two genes in Ae. aegypti (AeVigilin and AeRACK1), which were upregulated in DENV-infected Aag2 cells and mosquitoes, and silencing them in Aag2 cells resulted in reduced DENV replication. Co-immunoprecipitation showed that AeRACK1 and AeVigilin interact in mosquito cells. Interestingly, we also found upregulation of both genes in a Wolbachia-infected cell line (Aag2.wAlbB). Furthermore, silencing AeVigilin and AeRACK1 in Aag2.wAlbB cells reduced DENV replication but increased Wolbachia density. However, we did not find a significant effect on DENV replication after silencing both genes in Ae. aegypti mosquitoes. Overall, our results support the involvement and significance of AeVigilin and AeRACK1 in DENV replication in Ae. aegypti.IMPORTANCEDengue virus (DENV), transmitted mainly by Aedes aegypti mosquitoes, poses significant health risks. Identifying factors involved in the virus replication in mosquitoes and human hosts is essential for devising control measures. In this study, we show that Vigilin and the receptor for activated C kinase 1 (RACK1), two proteins shown to play a role in the replication of DENV in human cells, are induced in mosquitoes and cell lines following DENV replication. Both proteins reside in the cytoplasm, where they interact similarly to human cells. Silencing the genes in mosquito cells significantly reduced virus replication. Furthermore, we found that both genes are induced in mosquito cells transinfected with Wolbachia, a bacterium that blocks DENV replication. The results help better understand the role of the common factors supporting DENV replication in mosquitoes and human cells.

Newly Proposed Dose of Daclatasvir to Prevent Lethal SARS-CoV-2 Infection in Human Transgenic ACE-2 Mice.

Coronavirus disease 2019 (COVID-19) still causes death in elderly and immunocompromised individuals, for whom the sustainability of the vaccine response may be limited. Antiviral treatments, such as remdesivir or molnupiravir, have demonstrated limited clinical efficacy. Nirmatrelvir, an acute respiratory syndrome coronavirus 2 (SARS-CoV-2) major protease inhibitor, is clinically effective but has been associated with viral rebound and antiviral resistance. It is thus necessary to study novel and repurposed antivirals for the treatment of COVID-19. We previously demonstrated that daclatasvir (DCV), an inhibitor of the hepatitis C virus (HCV) NS5A protein, impairs SARS-CoV-2 replication by targeting viral RNA polymerase and exonuclease, but the doses of DCV used to inhibit the new coronavirus are greater than the standard human plasma exposure for hepatitis C. Because any potential use of DCV against SARS-CoV-2 would be shorter than that reported here and short-term toxicological studies on DCV show that higher doses are tolerable, we searched for doses of DCV that could protect transgenic mice expressing the human ACE2 receptor (K18-hACE-2) from lethal challenge with SARS-CoV-2. We found that a dose of 60 mg/kg/day provides this protection by reducing virus replication and virus-induced lung insult. This dose is tolerable in different animal models. Taken together, our data provide preclinical evidence that can support phase I clinical trials to confirm the safety, tolerability, and pharmacokinetics of new doses of daclatasvir for a short duration in humans to further advance this compound's utility against COVID-19.

Sirtuin 1 Dynamic Interplay of IFI16 and STING Interferon-Stimulated Gene Regulate Hepatitis B Virus Replication

Background: Hepatitis B virus (HBV) infection remains a significant global health concern, affecting millions worldwide and often leading to severe liver diseases. Chronic conditions associated with HBV contribute to the development of liver fibrosis, a crucial prognostic factor necessitating urgent therapeutic strategies. Objectives: This study aims to elucidate the interplay between interferon (IFN)-inducible protein 16 (IFI16), Sirtuin 1 (Sirt1) (NAD-dependent deacetylase), and STING (Stimulator of Interferon Genes) in the context of HBV infection, focusing on understanding their roles in viral replication and innate immune responses. Methods: This study investigates the interaction between Sirt1 and IFI16 during active HBV replication using siRNA-mediated knockdown and co-transfection techniques. HBV replication is assessed following IFI16 silencing, and the synergistic inhibition of IFI16 and Sirt1 is evaluated. Western blotting, electrophoresis, and immunoprecipitation methods are employed to explore STING's role in DNA-mediated innate immunity and interferon-stimulated gene activation during viral infection. Results: While individual knockdown of IFI16 has minimal impact on HBV replication, with a reduction of less than 10%, dual inhibition of IFI16 and Sirt1 resulted in a significant reduction in viral replication by approximately 70%. This underscores the synergistic role of these proteins in the context of HBV infection. Furthermore, the study implicates STING as a promising therapeutic target for viral infections, shedding light on its regulatory role in innate immune responses and interferon-stimulated genes (ISGs). Conclusions: Our study reveals the complex interplay between IFI16, Sirt1, and STING in HBV infection, highlighting potential therapeutic targets. While in vitro findings offer valuable insights, in vivo validation and further exploration of broader pathway interactions are essential. Future efforts should prioritize translating these findings into clinical applications for HBV treatment.

Role of RNA G-Quadruplexes in the Japanese Encephalitis Virus Genome and Their Recognition as Prospective Antiviral Targets.

G-quadruplexes (GQs) have been primarily studied in the context of cancer and neurodegenerative pathologies. However, recent research has shifted focus to their existence and functional roles in viral genomes, revealing GQ-regulated key pathways in various human pathogenic viruses. While GQ structures have been reported in the genomes of emerging and re-emerging viruses, RNA viruses have been understudied compared to DNA viruses, including notable examples such as human immunodeficiency virus-1, hepatitis C virus, Ebola virus, Nipah virus, Zika virus, and SARS-CoV-2. The flavivirus family, comprising the Japanese encephalitis virus (JEV), poses a significant global threat due to recurring outbreaks yet lacks approved antivirals. In this study, we identified and characterized eight putative G-quadruplex-forming motifs within essential genes involved in genome replication, assembly, and internalization in the host cell, conserved across different JEV isolates. The formation and stability of these motifs were validated through a multitude of biophysical and cell-based assays. The interaction and binding affinity of these motifs with the known GQ-binding ligand BRACO-19 were supported by biophysical assays, confirming the capability of these motifs to form GQ structures. Notably, BRACO-19 also exerted antiviral properties through reduction of viral replication and infectious virus titers as well as inhibition of viral protein expression, as evaluated by the cell-based assays. This comprehensive molecular characterization of G-quadruplex structures within the JEV genome highlights their potential as promising antiviral targets for intervention strategies against JEV infection through GQ-specific ligands.

Phosphorylation of Ser711 residue in the hypervariable region of zoonotic genotype 3 hepatitis E virus is important for virus replication.

Hepatitis E virus (HEV) is distinct from other hepatotropic viruses because it is zoonotic. HEV-1 and HEV-2 exclusively infect humans, whereas HEV-3 and HEV-4 are zoonotic. However, the viral and/or host factors responsible for cross-species HEV transmission remain elusive. The hypervariable region (HVR) in HEV is extremely heterogenetic and is implicated in HEV adaptation. Here, we investigated the potential role of Serine phosphorylation in the HVR in HEV replication. We first analyzed HVR sequences across different HEV genotypes and identified a unique region at the N-terminus of the HVR, which is variable in the human-exclusive HEV genotypes but relatively conserved in zoonotic HEV genotypes. Using predictive tools, we identified four potential phosphorylation sites that are highly conserved in zoonotic HEV-3 and HEV-4 genomes but absent in human-exclusive HEV-1 strains. To explore the functional significance of these putative phosphorylation sites, we introduced mutations into the HEV-3 infectious clone and indicator replicon, replacing each Serine residue individually with alanine or aspartic acid, and assessed the impact of these substitutions on HEV-3 replication. We found that the phospho-blatant S711A mutant significantly reduced virus replication, whereas the phospho-mimetic S711D mutant modestly reduced virus replication. Conversely, mutations in the other three Serine residues did not significantly affect HEV-3 replication. Furthermore, we demonstrated that Ser711 phosphorylation did not alter host cell tropism of zoonotic HEV-3. In conclusion, our results showed that potential phosphorylation of the Ser711 residue significantly affects HEV-3 replication in vitro, providing new insights into the potential mechanisms of zoonotic HEV transmission.IMPORTANCEHEV is an important zoonotic pathogen, causing both acute and chronic hepatitis E and extrahepatic manifestation of diseases, such as neurological sequelae. The zoonotic HEV-3 is linked to chronic infection and neurological diseases. The specific viral and/or host factors facilitating cross-species HEV infection are unknown. The intrinsically disordered HVR in ORF1 is crucial for viral fitness and adaptation, both in vitro and in vivo. We hypothesized that phosphorylation of Serine residues in the HVR of zoonotic HEV by unknown host cellular kinases is associated with cross-species HEV transmission. In this study, we identified a conserved region within the HVR of zoonotic HEV strains but absent in the human-exclusive HEV-1 and HEV-2. We elucidated the important role of phosphorylation at the Ser711 residue in zoonotic HEV-3 replication, without altering the host cell tropism. These findings contribute to our understanding the mechanisms of cross-species HEV transmission.

CRISPR-Cas Innovative Strategies for Combating Viral Infections and Enhancing Diagnostic Technologies

Background: CRISPR-Cas technology has transformed molecular diagnostics and therapeutic strategies for viral infections, particularly COVID-19. Its ability to precisely edit viral genomes and detect viral RNA/DNA offers a novel approach to combating persistent viral infections.Objective: This study aimed to evaluate the diagnostic accuracy and therapeutic potential of CRISPR-Cas systems in viral infections, with a focus on COVID-19.Methods: A systematic review and meta-analysis of 25 peer-reviewed studies were conducted, including clinical trials and experimental research. Data collection involved searching PubMed, Scopus, and Google Scholar using keywords such as "CRISPR-Cas," "viral diagnostics," and "COVID-19." Statistical analysis was performed using SPSS version 25, with pooled sensitivity and specificity estimates calculated for CRISPR-based diagnostics.Results: CRISPR-based diagnostics, including SHERLOCK and DETECTR, achieved pooled sensitivity of 94% (95% CI: 92%-96%) and specificity of 97% (95% CI: 95%-99%) for SARS-CoV-2 detection. Therapeutic interventions using CRISPR-Cas9 showed an 84% reduction in viral replication across HIV and Hepatitis B studies (95% CI: 80%-88%).Conclusion: CRISPR-Cas technologies demonstrate high diagnostic accuracy and therapeutic potential, particularly in resource-limited settings. Further clinical validation is needed to enhance global healthcare applications.

Mpox mRNA-1769 Vaccine Inhibits Orthopoxvirus Replication at Intranasal, Intrarectal, and Cutaneous Sites of Inoculation.

The increasing incidence of mpox in Africa and the recent global outbreak with evidence of sexual transmission have stimulated interest in new vaccines and therapeutics. Our previous study demonstrated that mice immunized twice with a quadrivalent lipid nanoparticle vaccine comprising four monkeypox virus mRNAs raised neutralizing antibodies and antigen-specific T cells and were protected against a lethal intranasal challenge with vaccinia virus. Here we extended these findings by using live animal imaging to demonstrate that the mRNA vaccine greatly reduced virus replication and spread from an intranasal site of inoculation and prevented detectable replication at intrarectal and cutaneous inoculation sites. Moreover, considerable protection was achieved with a single vaccination and a booster vaccination enhanced protection for at least 4 months. Protection was related to the amount of mRNA inoculated, which correlated with neutralizing antibody levels. The role of antibody in protection was demonstrated by passive transfer of immune serum pre- or post-challenge to immunocompetent and immunodeficient mice lacking mature B and T cells and therefore unable to mount an adaptive response. These findings provide insights into the mechanism and extent of mRNA vaccine induced protection of orthopoxviruses and support clinical testing.

ESCRT Protein VPS4A Is Required for the Formation of Replication Centers and Replication of Human Coronavirus 229E (HCoV-229E)

Human coronavirus 229E (HCoV-229E) is an alpha coronavirus that infects humans and bats. In common with all positive-strand RNA viruses, 229E infection causes rearrangements of the host’s intracellular membranes to form replication organelles, a highly conserved and vital step in the viral replication cycle. Here, we investigated the role of the ESCRT protein VPS4A in 229E infection. We found that functional VPS4A was required for the formation of replication organelles and localizing viral RNA to these structures in host cells to facilitate viral genome replication. We validated this effect using small molecule inhibitors to VPS4A, significantly reducing virus replication. We also showed that other ESCRTS, like CHMP4B, were required for the virus replication step, whereas VPS37A was involved in the post-replication stages. The absence of a functional VPS4A prevented the remodeling of membranes to form viral replication centers and, therefore, exposed the viral RNA, triggering an inflammatory immune response as indicated by elevated levels of IL-6. Interestingly, we observed the role of VPS4A to be similar for the OC43 coronavirus, indicating it could be conserved across all four coronavirus genera, including SARS-CoV-2. Understanding more about the replication of coronaviruses is imperative to finding more effective ways to control them.

A prM mutation that attenuates dengue virus replication in human cells enhances midgut infection in mosquitoes.

Dengue viruses (DENVs), like all viruses, evolve to perpetuate transmission of their species in their hosts. However, how DENV genetics influences dengue disease outbreaks remains poorly understood. Here, we examined isolates of the South Pacific dengue virus type 2 (DENV-2) that emerged in the 1970s and caused major dengue outbreaks in islands in this region until it reached Tonga, where only a few mild cases were reported. Phylogenetically, the DENV-2 strain isolated in Tonga segregated into a clade different from those clades infecting populations in other South Pacific islands. We found that this epidemiological observation could be explained by a single histidine-to-arginine substitution in position 86 of the premembrane (prM) protein of the Tonga DENV-2 strain. This mutation attenuated viral protein translation in mammalian cells but not in midgut cells of the mosquito vector Aedes aegypti. In mammalian cells, the prM mutation resulted in reduced translation of the viral genome and subsequent reduced virus replication. In contrast, in mosquito midgut cells, the prM mutation conferred a selective infection advantage, possibly because of the positively charged arginine residue introduced by the mutation. These findings provide molecular insights into the year-long silent transmission of attenuated DENV-2 in Tonga during the 1970s dengue outbreak in the South Pacific.

Cystatin F Depletion in Mycobacterium tuberculosis-Infected Macrophages Improves Cathepsin C/Granzyme B-Driven Cytotoxic Effects on HIV-Infected Cells during Coinfection.

Cystatin F (CstF) is a protease inhibitor of cysteine cathepsins, including those involved in activating the perforin/granzyme cytotoxic pathways. It is targeted at the endolysosomal pathway but can also be secreted to the extracellular milieu or endocytosed by bystander cells. CstF was shown to be significantly increased in tuberculous pleurisy, and during HIV coinfection, pleural fluids display high viral loads. In human macrophages, our previous results revealed a strong upregulation of CstF in phagocytes activated by interferon γ or after infection with Mycobacterium tuberculosis (Mtb). CstF manipulation using RNA silencing led to increased proteolytic activity of lysosomal cathepsins, improving Mtb intracellular killing. In the present work, we investigate the impact of CstF depletion in macrophages during the coinfection of Mtb-infected phagocytes with lymphocytes infected with HIV. The results indicate that decreasing the CstF released by phagocytes increases the major pro-granzyme convertase cathepsin C of cytotoxic immune cells from peripheral blood-derived lymphocytes. Consequently, an observed augmentation of the granzyme B cytolytic activity leads to a significant reduction in viral replication in HIV-infected CD4+ T-lymphocytes. Ultimately, this knowledge can be crucial for developing new therapeutic approaches to control both pathogens based on manipulating CstF.

Reassortment incompetent live attenuated and replicon influenza vaccines provide improved protection against influenza in piglets

Swine influenza A viruses (swIAV) cause an economically important respiratory disease in modern pig production. Continuous virus transmission and antigenic drift are difficult to control in enzootically infected pig herds. Here, antibody-positive piglets from a herd enzootically infected with swIAV H1N2 (clade 1 A.3.3.2) were immunized using a homologous prime-boost vaccination strategy with novel live attenuated influenza virus (LAIV) based on a reassortment-incompetent bat influenza-swIAV chimera or a vesicular stomatitis virus-based replicon vaccine. Challenge infection of vaccinated piglets by exposure to H1N2 swIAV-infected unvaccinated seeder pigs showed that both LAIV and replicon vaccine markedly reduced virus replication in the upper and lower respiratory tract, respectively, compared to piglets immunized with commercial heterologous or autologous adjuvanted whole-inactivated virus vaccines. Our novel vaccines may aid in interrupting continuous IAV transmission chains in large enzootically infected pig herds, improve the health status of the animals, and reduce the risk of zoonotic swIAV transmission.

Exploring Barmah Forest virus pathogenesis: molecular tools to investigate non-structural protein 3 nuclear localization and viral genomic determinants of replication.

Barmah Forest virus (BFV) is a mosquito-borne virus that causes arthralgia with accompanying rash, fever, and myalgia in humans. The virus is mainly found in Australia and has caused outbreaks associated with significant health concerns. As the sole representative of the Barmah Forest complex within the genus Alphavirus, BFV is not closely related genetically to other alphaviruses. Notably, basic knowledge of BFV molecular virology has not been well studied due to a lack of critical investigative tools such as an infectious clone. Here we describe the construction of an infectious BFV cDNA clone based on Genbank sequence and demonstrate that the clone-derived virus has in vitro and in vivo properties similar to naturally occurring virus, BFV field isolate 2193 (BFV2193-FI). A substitution in nsP4, V1911D, which was identified in the Genbank reference sequence, was found to inhibit virus rescue and replication. T1325P substitution in nsP2 selected during virus passaging was shown to be an adaptive mutation, compensating for the inhibitory effect of nsP4-V1911D. The two mutations were associated with changes in viral non-structural polyprotein processing and type I interferon (IFN) induction. Interestingly, a nuclear localization signal, active in mammalian but not mosquito cells, was identified in nsP3. A point mutation abolishing nsP3 nuclear localization attenuated BFV replication. This effect was more prominent in the presence of type I interferon signaling, suggesting nsP3 nuclear localization might be associated with IFN antagonism. Furthermore, abolishing nsP3 nuclear localization reduced virus replication in mice but did not significantly affect disease.IMPORTANCEBarmah Forest virus (BFV) is Australia's second most prevalent arbovirus, with approximately 1,000 cases reported annually. The clinical symptoms of BFV infection include rash, polyarthritis, arthralgia, and myalgia. As BFV is not closely related to other pathogenic alphaviruses or well-studied model viruses, our understanding of its molecular virology and mechanisms of pathogenesis is limited. There is also a lack of molecular tools essential for corresponding studies. Here we describe the construction of an infectious clone of BFV, variants harboring point mutations, and sequences encoding marker protein. In infected mammalian cells, nsP3 of BFV was located in the nuclei. This finding extends our understanding of the diverse mechanisms used by alphavirus replicase proteins to interact with host cells. Our novel observations highlight the complex synergy through which the viral replication machinery evolves to correct mutation errors within the viral genome.

Development of novel antivrial agents that induce the degradation of the main protease of human-infecting coronaviruses

The family of human-infecting coronaviruses (HCoVs) poses a serious threat to global health and includes several highly pathogenic strains that cause severe respiratory illnesses. It is essential that we develop effective broad-spectrum anti-HCoV agents to prepare for future outbreaks. In this study, we used PROteolysis TArgeting Chimera (PROTAC) technology focused on degradation of the HCoV main protease (Mpro), a conserved enzyme essential for viral replication and pathogenicity. By adapting the Mpro inhibitor GC376, we produced two novel PROTACs, P2 and P3, which showed relatively broad-spectrum activity against the human-infecting CoVs HCoV-229E, HCoV-OC43, and SARS-CoV-2. The concentrations of these PROTACs that reduced virus replication by 50 % ranged from 0.71 to 4.6 μM, and neither showed cytotoxicity at 100 μM. Furthermore, mechanistic binding studies demonstrated that P2 and P3 effectively targeted HCoV-229E, HCoV-OC43, and SARS-CoV-2 by degrading Mpro within cells in vitro. This study highlights the potential of PROTAC technology in the development of broad-spectrum anti-HCoVs agents, presenting a novel approach for dealing with future viral outbreaks, particularly those stemming from CoVs.

Antiviral activity of temporin-1CEb analogues against gingival infection with herpes simplex virus type 1.

Oral herpes infections caused by herpes simplex virus type 1 (HSV-1) are one of the most common in the human population. Recently, they have been classified as an increasing problem in immunocompromised patients and those suffering from chronic inflammation of the oral mucosa and gums. Treatment mainly involves nucleoside analogues, such as acyclovir and its derivatives, which reduce virus replication and shedding. As drug-resistant strains of herpes emerge rapidly, there is a need for the development of novel anti-herpes agents. The aim of the study was to design an antiviral peptide, based on natural compounds, non-toxic to the host, and efficient against drug-resistant HSV-1. Here, we designed a lysine-rich derivative of amphibian temporin-1CEb conjugated to peptides penetrating the host cell membrane and examined their activity against HSV-1 infection of oral mucosa. We assessed the antiviral efficiency of the tested compound in simple 2D cell models (VeroE6 and TIGKs cells) and a 3D organotypic model of human gingiva (OTG) using titration assay, qPCR, and confocal imaging. To identify the molecular mechanism of antiviral activity, we applied the Azure A metachromatic test, and attachment assays techniques. Toxicity of the conjugates was examined using XTT and LDH assays. Our results showed that temporin-1CEb analogues significantly reduce viral replication in oral mucosa. The mechanism of peptide analogues is based on the interaction with heparan sulfate, leading to the reduce attachment of HSV-1 to the cell membrane. Moreover, temporin-1CEb conjugates effectively penetrate the gingival tissue being effective against acyclovir-resistant strains. Collectively, we showed that temporin-1CEb can be regarded as a novel, naturally derived antiviral compound for HSV-1 treatment.

Hexestrol, an estrogen receptor agonist, inhibits Lassa virus entry.

Lassa virus (LASV) is the causative agent of human Lassa fever which in severe cases manifests as hemorrhagic fever leading to thousands of deaths annually. However, no approved vaccines or antiviral drugs are currently available. Recently, we screened approximately 2,500 compounds using a recombinant vesicular stomatitis virus (VSV) expressing LASV glycoprotein GP (VSV-LASVGP) and identified a P-glycoprotein inhibitor as a potential LASV entry inhibitor. Here, we show that another identified candidate, hexestrol (HES), an estrogen receptor agonist, is also a LASV entry inhibitor. HES inhibited VSV-LASVGP replication with a 50% inhibitory concentration (IC50) of 0.63 µM. Importantly, HES also inhibited authentic LASV replication with IC50 values of 0.31 µM-0.61 µM. Time-of-addition and cell-based membrane fusion assays suggested that HES inhibits the membrane fusion step during virus entry. Alternative estrogen receptor agonists did not inhibit VSV-LASVGP replication, suggesting that the estrogen receptor itself is unlikely to be involved in the antiviral activity of HES. Generation of a HES-resistant mutant revealed that the phenylalanine at amino acid position 446 (F446) of LASVGP, which is located in the transmembrane region, conferred resistance to HES. Although mutation of F446 enhanced the membrane fusion activity of LASVGP, it exhibited reduced VSV-LASVGP replication, most likely due to the instability of the pre-fusion state of LASVGP. Collectively, our results demonstrated that HES is a promising anti-LASV drug that acts by inhibiting the membrane fusion step of LASV entry. This study also highlights the importance of the LASVGP transmembrane region as a target for anti-LASV drugs.IMPORTANCELassa virus (LASV), the causative agent of Lassa fever, is the most devastating mammarenavirus with respect to its impact on public health in West Africa. However, no approved antiviral drugs or vaccines are currently available. Here, we identified hexestrol (HES), an estrogen receptor agonist, as the potential antiviral candidate drug. We showed that the estrogen receptor itself is not involved in the antiviral activity. HES directly bound to LASVGP and blocked membrane fusion, thereby inhibiting LASV infection. Through the generation of a HES-resistant virus, we found that phenylalanine at position 446 (F446) within the LASVGP transmembrane region plays a crucial role in the antiviral activity of HES. The mutation at F446 caused reduced virus replication, likely due to the instability of the pre-fusion state of LASVGP. These findings highlight the potential of HES as a promising candidate for the development of antiviral compounds targeting LASV.