Vesicular Stomatitis Research Articles

Oncolytic viruses-modulated immunogenic cell death, apoptosis and autophagy linking to virotherapy and cancer immune response.

Recent reports have revealed that oncolytic viruses (OVs) play a significant role in cancer therapy. The infection of OVs such as oncolytic vaccinia virus (OVV), vesicular stomatitis virus (VSV), parvovirus, mammalian reovirus (MRV), human adenovirus, Newcastle disease virus (NDV), herpes simplex virus (HSV), avian reovirus (ARV), Orf virus (ORFV), inactivated Sendai virus (ISV), enterovirus, and coxsackievirus offer unique opportunities in immunotherapy through diverse and dynamic pathways. This mini-review focuses on the mechanisms of OVs-mediated virotherapy and their effects on immunogenic cell death (ICD), apoptosis, autophagy and regulation of the immune system.

Regulated control of virus replication by 4-hydroxytamoxifen-induced splicing.

Designing a modified virus that can be controlled to replicate will facilitate the study of pathogenic mechanisms of virus and virus-host interactions. Here, we report a universal switch element that enables precise control of virus replication after exposure to a small molecule. Inteins mediate a traceless protein splicing-ligation process, and we generate a series of modified vesicular stomatitis virus (VSV) with intein insertion into the nucleocapsid, phosphoprotein, or large RNA-dependent RNA polymerase of VSV. Two recombinant VSV, LC599 and LY1744, were screened for intein insertion in the large RNA-dependent RNA polymerase of VSV, and their replication was regulated in a dose-dependent manner with the small molecule 4-hydroxytamoxifen, which induces intein splicing to restore the VSV replication. Furthermore, in the presence of 4-hydroxytamoxifen, the intein-modified VSV LC599 replicated efficiently in an animal model like a prototype of VSV. Thus, we present a simple and highly adaptable tool for regulating virus replication.

Polarimetric imaging for the detection of synthetic models of SARS-CoV-2: A proof of concept

ObjectiveTo conduct a proof-of-concept study of the detection of two synthetic models of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using polarimetric imaging. ApproachTwo SARS-CoV-2 models were prepared as engineered lentiviruses pseudotyped with the G protein of the vesicular stomatitis virus, and with the characteristic Spike protein of SARS-CoV-2. Samples were prepared in two biofluids (saline solution and artificial saliva), in four concentrations, and deposited as 5-µL droplets on a supporting plate. The angles of maximal degree of linear polarization (DLP) of light diffusely scattered from dry residues were determined using Mueller polarimetry from87 samples at 405 nm and 514 nm. A polarimetric camera was used for imaging several samples under 380–420 nm illumination at angles similar to those of maximal DLP. Per-pixel image analysis included quantification and combination of polarization feature descriptors in 475 samples. Main resultsThe angles (from sample surface) of maximal DLP were 3° for 405 nm and 6° for 514 nm. Similar viral particles that differed only in the characteristic spike protein of the SARS-CoV-2, their corresponding negative controls, fluids, and the sample holder were discerned at 10-degree and 15-degree configurations. SignificancePolarimetric imaging in the visible spectrum may help improve fast, non-contact detection and identification of viral particles, and/or other microbes such as tuberculosis, in multiple dry fluid samples simultaneously, particularly when combined with other imaging modalities. Further analysis including realistic concentrations of real SARS-CoV-2 viral particles in relevant human fluids is required. Polarimetric imaging under visible light may contribute to a fast, cost-effective screening of SARS-CoV-2 and other pathogens when combined with other imaging modalities.

Multi-modal efficacy of a chimeric vesiculovirus expressing the Morreton glycoprotein in sarcoma

Vesiculoviruses are attractive oncolytic virus platforms due to their rapid replication, appreciable transgene capacity, broad tropism, limited preexisting immunity, and tumor selectivity through type I interferon response defects in malignant cells. We developed a synthetic chimeric virus (VMG) expressing the glycoprotein (G)from Morreton virus (MorV) and utilizing the remaining structural genes from vesicular stomatitis virus (VSV). VMG exhibited invitro efficacy by inducing oncolysis in a broad range of sarcoma subtypes across multiple species. Notably, all cell lines tested showed the ability of VMG to yield productive infection with rapid replication kinetics and inductionof apoptosis. Furthermore, pilot safety evaluations of VMG in immunocompetent, non-tumor-bearing mice showed an absence of toxicity with intranasal doses as high as 1e10 50% tissue culture infectious dose (TCID50)/kg. Locoregional administration of VMG invivo resulted in tumor reduction in an immunodeficient Ewing sarcoma xenograft at doses as low as 2e5 TCID50. In a murine syngeneic fibrosarcoma model, while no tumor inhibition was achieved with VMG, there was a robust induction of CD8+ Tcells within the tumor. The studies described herein establish the promising potential for VMG to be used as a novel oncolytic virotherapy platform with anticancer effects in sarcoma.

Rapid protection of nonhuman primates against Marburg virus disease using a single low-dose VSV-based vaccine.

Marburg virus (MARV) is the causative agent of Marburg virus disease (MVD) which has a case fatality rate up to ∼90% in humans. Recently, there were cases reported in Guinea and Ghana highlighting this virus as a high-consequence pathogen potentially threatening global public health. There are no licensed treatments or vaccines available today. We used a vesicular stomatitis virus (VSV)-based vaccine expressing the MARV-Angola glycoprotein (VSV-MARV) as the viral antigen. Previously, a single dose of 1×107 plaque-forming units (PFU) administered 7 days before challenge resulted in uniform protection from disease in cynomolgus macaques. As we sought to lower the vaccination dose to achieve a higher number of vaccine doses per vial, we administered 1×105 or 1×103PFU 14 days or 1×103PFU 7 days before challenge to cohorts of cynomolgus macaques and investigated immunity as well as protective efficacy. Vaccination resulted in uniform protection with no detectable viremia. Antigen-specific IgG responses were induced by both vaccine concentrations and were sustained until the study endpoint. Neutralizing antibody responses and antibody-dependent cellular phagocytosis were observed. The cellular response after vaccination was characterized by an early induction of NK cell activation. Additionally, antigen-specific memory T cell subsets were detected in all vaccination cohorts indicating that while the primary protective mechanism of VSV-MARV is the humoral response, a functional cellular response is also induced. Overall, this data highlights VSV-MARV as a viable and fast-acting MARV vaccine candidate suitable for deployment in emergency outbreak situations and supports its clinical development. This work was funded by the Intramural Research Program NIAID, NIH.

TOP-EVs: Technology of Protein delivery through Extracellular Vesicles is a versatile platform for intracellular protein delivery.

Extracellular vesicles (EVs) have emerged as biocompatible drug delivery vehicles due to their native ability to deliver bioactive cargo to recipient cells. However, the application of EVs as a therapeutic delivery vehicle is hampered by effective methods for endogenously loading target proteins inside EVs and unloading proteins after delivery to recipient cells. Most EV-based engineered loading methods have a limited delivery efficiency owing to their inefficient endosomal escape or cargo release from the intraluminal attachment from the EV membrane. Here, we describe the 'Technology Of Protein delivery through Extracellular Vesicles' (TOP-EVs) as a tool for efficient intracellular delivery of target proteins mediated via EVs. The vesicular stomatitis virus glycoprotein and the rapamycin-heterodimerization of the FKBP12/T82L mutant FRB proteins were both important for the effective protein delivery through TOP-EVs. We showed that TOP-EVs could efficiently deliver Cre recombinase and CRISPR/Cas9 ribonucleoprotein complex in vitro. Moreover, our results demonstrated that the capacity of TOP-EVs to deliver intracellular proteins in recipient cells was not an artifact of plasmid contamination or direct plasmid loading into EVs. Finally, we showed that TOP-EVs could successfully mediate intracellular protein delivery in the liver in vivo. Taken together, TOP-EVs are a versatile platform for efficient intracellular protein delivery in vitro and in vivo, which can be applied to advance the development of protein-based therapeutics.

Purification of recombinant vesicular stomatitis virus-based HIV vaccine candidate.

In this work, laboratory- and large-scale methods were tested for purification of a human immunodeficiency virus (HIV) vaccine candidate, based on recombinant vesicular stomatitis virus (rVSV). First step of the purification, the clarification of the rVSVs produced in serum-free cell culture medium, was tested by centrifugation and filtration using different filtration media and pore sizes (0.45 to 30µm). To reduce the supernatant volume and process time, the clarified sample was concentrated by ultrafiltration either using tangential flow filtration or centrifugal-based filtration units, depending on the process scale. The final purification step at laboratory-scale, was carried out by density gradient ultracentrifugation, the recovery of which was compared with chromatographic purification at large-scale. The virus preparations were analyzed using dynamic light scattering to verify the virus size and transmission electron microscopy for purity and virus morphology. Density gradient ultracentrifugation allowed the recovery of≥80% infectious particles and reduced the contaminant DNA and host cell proteins relatively to standard ultracentrifugation pelleting using a sucrose cushion. At large-scale, weak and strong anion-exchangers were tested and compared. The best columns allowed infectious virus recoveries as high as 77% and eliminated 92% of host cell proteins.

Oncolytic Effect of a Recombinant Vesicular Stomatitis Virus Encoding a Tumor-suppressor MicroRNA in an Osteosarcoma Mouse Model.

Attempts have been made to enhance treatment with vesicular stomatitis virus (VSV) for osteosarcoma. We have previously shown that VSV incorporated with miRNA143 enhanced the antitumor effect at some doses; however, the range of the doses was narrow. This has not been evaluated in vivo, and the synergistic effect of this antitumor effect in animals is unknown. The purpose of the study was to evaluate the oncolytic effect of VSV-miRNA on osteosarcoma cells in vivo. A novel oncolytic VSV was developed by incorporating the tumor-suppressor microRNA143 (rVSV-miR143). In order to compare the antitumor effects of administration methods (intravenous and intratumoral administration) of rVSV-miR143 with those of VSV, a comparative analysis of primary tumor volume, metastatic lesions and survival rate was performed in mouse models of osteosarcoma. Following intratumoral injection, rVSV-miR143 showed a significant reduction in primary tumor volume, but no significant difference was observed in metastatic lesions and survival rate compared to VSV. Following intravenous injection, rVSV-miR143 revealed no significant difference in primary tumor volume, metastatic lesion and survival rate compared to VSV. VSV incorporating tumor-suppressor miRNA143 demonstrated a slightly synergistic antitumor effect on osteosarcoma in vivo.

Evaluation of the immunogenicity and efficacy of an rVSV vaccine against Zika virus infection in macaca nemestrina.

Zika virus (ZIKV) is a mosquito-borne flavivirus that causes an acute febrile illness. ZIKV can be transmitted between sexual partners and from mother to fetus. Infection is strongly associated with neurologic complications in adults, including Guillain-Barré syndrome and myelitis, and congenital ZIKV infection can result in fetal injury and congenital Zika syndrome (CZS). Development of an effective vaccine is imperative to protect against ZIKV vertical transmission and CZS. Recombinant Vesicular Stomatitis virus (rVSV) is a highly effective and safe vector for the delivery of foreign immunogens for vaccine purposes. Here, we evaluate an rVSV vaccine expressing the full length pre-membrane (prM) and ZIKV envelope (E) proteins (VSV-ZprME), shown to be immunogenic in murine models of ZIKV infection, for its capacity to induce immune responses in nonhuman primates. Moreover, we assess the efficacy of the rVSVΔM-ZprME vaccine in the protection of pigtail macaques against ZIKV infection. Administration of the rVSVΔM-ZprME vaccine was safe, but it did not induce robust anti-ZIKV T-cell responses, IgM or IgG antibodies, or neutralizing antibodies in most animals. Post ZIKV challenge, animals that received the rVSVΔM control vaccine lacking ZIKV antigen had higher levels of plasma viremia compared to animals that received the rVSVΔM-ZprME vaccine. Anti-ZIKV neutralizing Ab titers were detected in a single animal that received the rVSVΔM-ZprME vaccine that was associated with reduced plasma viremia. The overall suboptimal ZIKV-specific cellular and humoral responses post-immunization indicates the rVSVΔM-ZprME vaccine did not elicit an immune response in this pilot study. However, recall antibody response to the rVSVΔM-ZprME vaccine indicates it may be immunogenic and further developments to the vaccine construct could enhance its potential as a vaccine candidate in a nonhuman primate pre-clinical model.

Efficient generation and characterization of chimeric dengue viral-like particles

Viral-like particles (VLPs) because of their non-infectious and high immunogenic properties have important applications in diagnostics, drug delivery, and vaccine production. They also serve as an attractive model system to study virus assembly and fusion processes. Unlike other flaviviruses, Dengue virus (DENV) is not very efficient in the production of VLPs on the expression of DENV structural proteins. On the other hand, the stem region and transmembrane region (TM) of G protein of Vesicular Stomatitis virus (VSV) alone are sufficient for budding.Here we generated chimeric VLPs replacing regions of stem and transmembrane domain (STEM) or only transmembrane domain (TM) of E protein of DENV-2 with corresponding regions of VSV G protein. Both chimeric proteins secreted VLPs at higher levels than the wild type (2–4 folds) without any significant change in the expression in the cell. Chimeric VLPs could be recognized by a conformational monoclonal antibody, 4G2. They were also found to interact with dengue-infected patient sera effectively thus implying that their antigenic determinants are preserved. In addition, they were able to bind to its putative receptor, heparin with similar affinity as the parent counterpart thus retaining its functional property. However, cell-cell fusion revealed that there is no significant increase in the fusion ability of chimeras as compared to the parent clone, whereas VSV G protein displayed high cell-cell fusion activity. Overall, this study suggests that chimeric dengue VLPs can be taken forward for their likely potential as vaccine production and serodiagnosis.

Packaging cells for lentiviral vectors generated using the cumate and coumermycin gene induction systems and nanowell single-cell cloning

Lentiviral vectors (LVs) are important for cell therapy because of their capacity to stably modify the genome after integration. This study describes a novel and relatively simple approach to generate packaging cells and producer clones for self-inactivating (SIN) LVs pseudotyped with the vesicular stomatitis virus glycoprotein (VSV-G). A novel gene regulation system, based on the combination of the cumate and coumermycin induction systems, was developed to ensure tight control for the expression of cytotoxic packaging elements. To accelerate clone isolation and ensure monoclonality, the packaging genes were transfected simultaneously into human embryonic kidney cells (293SF-3F6) previously engineered with the induction system, and clones were isolated after limiting dilution into nanowell arrays using a robotic cell picking instrument with scanning capability. The method's effectiveness to isolate colonies derived from single cells was demonstrated using mixed populations of cells labeled with two different fluorescent markers. Because the recipient cell line grew in suspension culture, and all the procedures were performed without serum, the resulting clones were readily adaptable to serum-free suspension culture. The best producer clone produced LVs expressing GFP at a titer of 2.3×108 transduction units (TU)/mL in the culture medium under batch mode without concentration.

Molecular Tracking of the Origin of Vesicular Stomatitis Outbreaks in 2004 and 2018, Ecuador

The Vesicular Stomatitis Virus (VSV) is an arbovirus causing vesicular stomatitis (VS) in livestock. There are two serotypes recognized: New Jersey (VSNJV) and Indiana (VSIV). The virus can be transmitted directly by contact or by vectors. In 2018, Ecuador experienced an outbreak of Vesicular Stomatitis (VS) in cattle, caused by VSNJV and VSVIV, with 399 cases reported distributed over 18 provinces. We determined the phylogenetic relationships among 67 strains. For the construction of phylogenetic trees, the viral phosphoprotein gene was sequenced, and trees were constructed based on the Maximum Likelihood method using 2004 outbreak strains from Ecuador (GenBank) and the 2018 sequences (this article). We built a haplotype network for VSNJV to trace the origin of the 2004 and 2018 epizootics through topology and mutation connections. These analyses suggest two different origins, one related to the 2004 outbreak and the other from a transmission source in 2018. Our analysis also suggests different transmission patterns; several small and independent outbreaks, most probably transmitted by vectors in the Amazon, and another outbreak caused by the movement of livestock in the Andean and Coastal regions. We recommend further research into vectors and vertebrate reservoirs in Ecuador to clarify the mechanisms of the reemergence of the virus.

Process intensification strategies towardcell culture-based high-yield production of a fusogenic oncolytic virus.

We present a proof-of-concept study for production of a recombinant vesicular stomatitis virus (rVSV)-based fusogenic oncolytic virus (OV), rVSV-Newcastle disease virus(NDV), at high cell densities (HCD). Based on comprehensive experiments in 1 L stirred tank reactors (STRs) in batch mode, first optimization studies at HCD were carried out in semi-perfusion in small-scale cultivations using shake flasks. Further, a perfusion process was established using an acoustic settler for cell retention. Growth, production yields, and process-related impurities were evaluated for three candidate cell lines (AGE1.CR, BHK-21, HEK293SF)infected at densities ranging from 15 to 30 × 106  cells/mL. The acoustic settler allowed continuous harvesting of rVSV-NDV with high cell retention efficiencies (above 97%) and infectious virus titers (up to 2.4 × 109  TCID50 /mL), more than 4-100 times higher than for optimized batch processes. No decrease in cell-specific virus yield (CSVY) was observed at HCD, regardless of the cell substrate. Taking into account the accumulated number of virions both from the harvest and bioreactor, a 15-30 fold increased volumetric virus productivity for AGE1.CRand HEK293SF was obtained compared to batch processes performed at the same scale. In contrast to all previous findings, formation of syncytia was observed at HCD for the suspension cells BHK 21 and HEK293SF. Oncolytic potency was not affected compared to production in batch mode. Overall, our study describes promising options for the establishment of perfusion processes for efficient large-scale manufacturing of fusogenic rVSV-NDV at HCD for all three candidate cell lines.

Vesicular stomatitis Indiana virus near-full-length genome sequences reveal low genetic diversity during the 2019 outbreak in Colorado, USA.

DATA REPORT article Front. Vet. Sci., 14 February 2023Sec. Veterinary Epidemiology and Economics Volume 10 - 2023 | https://doi.org/10.3389/fvets.2023.1110483

Heterologous prime-boost cellular vaccination induces potent antitumor immunity against triple negative breast cancer.

Triple negative breast cancer (TNBC) is the most aggressive and hard-to-treat subtype of breast cancer, affecting 10-20% of all women diagnosed with breast cancer. Surgery, chemotherapy and hormone/Her2 targeted therapies are the cornerstones of treatment for breast cancer, but women with TNBC do not benefit from these treatments. Although the prognosis is dismal, immunotherapies hold significant promise in TNBC, even in wide spread disease because TNBC is infiltrated with more immune cells. This preclinical study is proposing to optimize an oncolytic virus-infected cell vaccine (ICV) based on a prime-boost vaccination strategy to address this unmet clinical need. We used various classes of immunomodulators to improve the immunogenicity of whole tumor cells in the prime vaccine, followed by their infection with oncolytic Vesicular Stomatitis Virus (VSVd51) to deliver the boost vaccine. For in vivo studies, we compared the efficacy of a homologous prime-boost vaccination regimen to a heterologous strategy by treating 4T1 tumor bearing BALB/c mice and further by conducting re-challenge studies to evaluate immune memory responses in surviving mice. Due to the aggressive nature of 4T1 tumor spread (akin to stage IV TNBC in human patients), we also compared early surgical resection of primary tumors versus later surgical resection combined with vaccination. In vitro results demonstrated that immunogenic cell death (ICD) markers and pro-inflammatory cytokines were released at the highest levels following treatment of mouse 4T1 TNBC cells with oxaliplatin chemotherapy and influenza vaccine. These ICD inducers also contributed towards higher dendritic cell recruitment and activation. With the top ICD inducers at hand, we observed that treatment of TNBC-bearing mice with the influenza virus-modified prime vaccine followed by VSVd51 infected boost vaccine resulted in the best survival. Furthermore, higher frequencies of both effector and central memory T cells along with a complete absence of recurrent tumors were observed in re-challenged mice. Importantly, early surgical resection combined with prime-boost vaccination led to improved overall survival in mice. Taken together, this novel cancer vaccination strategy following early surgical resection could be a promising therapeutic avenue for TNBC patients.

Baculovirus displaying SARS-CoV-2 spike RBD promotes neutralizing antibody production in a mouse model

BackgroundThere is always a need for a safe and efficient vaccine platform, especially when facing a pandemic such as COVID-19. Most of the SARS-CoV-2-based vaccines are based on the full spike protein, which is presented as a trimerized protein, and many viral vector vaccines express the spike protein into the host cells and do not display it on virus surfaces. However, the spike receptor-binding domain (RBD)-based vaccines are efficient and are currently under investigation and clinical trials. MethodologyIn this study, we are testing the efficacy of the RBD displayed on a baculovirus as a mean to formulate a safe and stable carrier to induce the immune system against SARS-CoV-2. Therefore, two pseudotyped baculoviruses were constructed to display the RBD, AcRBD-sfGFP-64, and AcRBD-sfGFP-V, using two different displaying strategies based on gp64 and VSV-G envelope glycoproteins, from Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and vesicular stomatitis virus (VSV), respectively. BALB/C mice were immunized with the pseudotyped baculoviruses in a dose-optimized manner. Dot blot and Western blot were used to screen and validate the polyclonal antibodies’ specificity to the SARS-CoV-2 RBD. A plaque reduction neutralization test (PRNT) was used to measure the sera neutralization capacity against a SARS-CoV-2 wild-type isolate from Egypt. ELISA was used to quantify certain cytokines for the assessment of the immune response. ResultThe outcome of our investigation showed that the monomeric RBD proteins were properly displayed on baculovirus and efficiently triggered the mouse immune system. The produced sera efficiently neutralized about 50% of SARS-CoV-2 in more than 100-fold serum dilution. The immunized mice showed a significant increase (p<0.01) in the levels of IL-2 and IFN-γ and a significant decrease (p<0.01) and (p<0.001) in the levels of IL-4 and IL-10, respectively, which suggest that AcRBD-sfGFP-64 and AcRBD-sfGFP-V induce Th1 cellular immune response. ConclusionThe produced recombinant viruses can induce the immune response without adjuvant, which needs dose optimization and further stability tests. Neutralizing antibodies were induced without affecting the health of immunized mice. Th1 response can be attainable through the system, which is of great benefit in SARS CoV-2 infection and the system can be tested for future applications including vaccine development and polyclonal antibody production.

NSUN2-mediated m5C methylation of IRF3 mRNA negatively regulates type I interferon responses during various viral infections

ABSTRACT 5-Methylcytosine (m5C) is a widespread post-transcriptional RNA modification and is reported to be involved in manifold cellular responses and biological processes through regulating RNA metabolism. However, its regulatory role in antiviral innate immunity has not yet been elucidated. Here, we report that NSUN2, a typical m5C methyltransferase, negatively regulates type I interferon responses during various viral infections, including SARS-CoV-2. NSUN2 specifically mediates m5C methylation of IRF3 mRNA and accelerates its degradation, resulting in low levels of IRF3 and downstream IFN-β production. Knockout or knockdown of NSUN2 enhanced type I interferon and downstream ISGs during various viral infection in vitro. And in vivo, the antiviral innate response is more dramatically enhanced in Nsun2+/− mice than in Nsun2+/+ mice. The highly m5C methylated cytosines in IRF3 mRNA were identified, and their mutation enhanced cellular IRF3 mRNA levels. Moreover, infection with Sendai virus (SeV), vesicular stomatitis virus (VSV), herpes simplex virus 1 (HSV-1), or Zika virus (ZIKV) resulted in a reduction of endogenous NSUN2 levels. Especially, SARS-CoV-2 infection (WT strain and BA.1 omicron variant) also decreased endogenous levels of NSUN2 in COVID-19 patients and K18-hACE2 KI mice, further increasing type I interferon and downstream ISGs. Together, our findings reveal that NSUN2 serves as a negative regulator of interferon response by accelerating the fast turnover of IRF3 mRNA, while endogenous NSUN2 levels decrease during SARS-CoV-2 and various viral infections to boost antiviral responses for effective elimination of viruses.

Characterization of a Vesicular Stomatitis Virus-Vectored Recombinant Virus Bearing Spike Protein of SARS-CoV-2 Delta Variant.

The frequent emergence of SARS-CoV-2 variants thwarts the prophylactic and therapeutic countermeasures confronting COVID-19. Among them, the Delta variant attracts widespread attention due to its high pathogenicity and fatality rate compared with other variants. However, with the emergence of new variants, studies on Delta variants have been gradually weakened and ignored. In this study, a replication-competent recombinant virus carrying the S protein of the SARS-CoV-2 Delta variant was established based on the vesicular stomatitis virus (VSV), which presented a safe alternative model for studying the Delta variant. The recombinant virus showed a replication advantage in Vero E6 cells, and the viral titers reach 107.3 TCID50/mL at 36 h post-inoculation. In the VSV-vectored recombinant platform, the spike proteins of the Delta variant mediated higher fusion activity and syncytium formation than the wild-type strain. Notably, the recombinant virus was avirulent in BALB/c mice, Syrian hamsters, 3-day ICR suckling mice, and IFNAR/GR-/- mice. It induced protective neutralizing antibodies in rodents, and protected the Syrian hamsters against the SARS-CoV-2 Delta variant infection. Meanwhile, the eGFP reporter of recombinant virus enabled the visual assay of neutralizing antibodies. Therefore, the recombinant virus could be a safe and convenient surrogate tool for authentic SARS-CoV-2. This efficient and reliable model has significant potential for research on viral-host interactions, epidemiological investigation of serum-neutralizing antibodies, and vaccine development.

Antiviral activity and molecular modeling studies on 1H-indole-2,3-diones carrying a naphthalene moiety

We here report the synthesis, structural characterization, and evaluation of the in vitro antiviral effects of a series of 1H-indole-2,3-diones (2a-f) bearing a naphthalene moiety. All 1-(naphthalen-2-ylmethyl)-1H-indole-2,3-diones (2c-f) tested against different herpes simplex viruses (HSVs) were found to be effective at low micromolar levels (EC50=2.3–20.0 µM). Molecular dynamics and docking simulations were performed with compound 2d which exhibited the strongest activity against HSVs and the binding affinities for HSV-1 surface glycoproteins B (gB) and D (gD) were calculated. Moreover, 5-bromo-1-(naphthalen-1-ylmethyl)-1H-indole-2,3-dione (2b) and 1-(naphthalen-2-ylmethyl)-1H-indole-2,3-dione (2c) exhibited nontoxic antiviral effects (EC50=6.8–12.0 µM) against vesicular stomatitis virus (VSV) and respiratory syncytial virus (RSV). To examine the contribution of the naphthalene ring, 1-methyl or 1-ethyl substituted compounds (2g-i) were also evaluated for in vitro antiviral activity, but these derivatives showed no antiviral activity against any of the viruses tested.

Species-specific immunogenicity and protective efficacy of a vesicular stomatitis virus-based Sudan virus vaccine: a challenge study in macaques

The recent Sudan virus (SUDV) outbreak in Uganda highlights the need for rapid response capabilities, including development of vaccines against emerging viruses with high public health impact. We aimed to develop a Sudan virus-specific vaccine suitable for emergency use during outbreaks. We generated and characterised a vesicular stomatitis virus (VSV)-based vaccine, VSV- SUDV, and evaluated the protective efficacy following a single-dose vaccination against lethal SUDV infection in non-human primates (NHPs). We used male and female cynomolgus macaques (n=11) aged 6-11 years and weighing 3·8-9·0 kg. Animals received a 1 mL intramuscular injection for vaccination containing either 1 × 107 plaque forming units (PFU) VSV-SUDV or 1 × 107 PFU of a VSV-based vaccine against Marburg virus (control; five NHPs). NHPs were challenged intramuscularly 28 days after vaccination with 1 × 104 TCID50 SUDV-Gulu. We assessed anaesthetised NHPs on days 28, 21, 14, and 7 before challenge; days 0, 3, 6, 9, 14, 21, 28, and 35 after challenge; and at euthanasia (day 40 for survivors). As we repurposed NHPs from a successful VSV-Ebola virus (EBOV) vaccine efficacy study, we also investigated VSV-EBOV's cross-protective potential against SUDV challenge. Of the six NHPs given VSV-SUDV, none showed any signs of disease in response to the challenge. Four of the five NHPs in the control group developed characteristic clinical signs of Sudan virus diseases. SUDV glycoprotein-specific IgG concentrations peaked 14 days after vaccination (titre of >1:10 000) and reached their highest concentrations at 6 days after challenge (1:25 600-1:102 400). Although the NHPs developed cross-reactive humoral responses to SUDV after VSV-EBOV vaccination and EBOV challenge, there was little cross-protection. These data emphasise the need for species-specific vaccines for each human-pathogenic Ebolavirus. Furthermore, although previous VSV-EBOV immunity is boosted through VSV-SUDV vaccination, it only has a small effect on the immunogenicity and protective efficacy of VSV-SUDV vaccination against SUDV challenge. Intramural Research Program, US National Institute of Allergy and Infectious Diseases, National Institutes of Health.