A recombinant rabies virus carrying GFP between N and P affects viral transcription in vitro

A rabies virus-vectored vaccine expressing two copies of the Marburg virus glycoprotein gene induced neutralizing antibodies against Marburg virus in humanized mice

Marburg virus disease (MVD) is a lethal viral haemorrhagic fever caused by Marburg virus (MARV) with a case fatality rate as high as 88%. There is currently no vaccine or antiviral therapy approved for MVD. Due to high variation among MARV isolates, vaccines developed against one strain fail to protect against other strains. Here we report that three recombinant rabies virus (RABV) vector vaccines encoding two copies of GPs covering both MARV lineages induced pseudovirus neutralizing antibodies in BALB/c mice. Furthermore, high-affinity human neutralizing antibodies were isolated from a humanized mouse model. The three vaccines produced a Th1-biased serological response similar to that of human patients. Adequate sequential immunization enhanced the production of neutralizing antibodies. Virtual docking suggested that neutralizing antibodies induced by the Angola strain seemed to be able to hydrogen bond to the receptor-binding site (RBS) in the GP of the Ravn strain through hypervariable regions 2 (CDR2) and CDR3 of the VH region. These findings demonstrate that three inactivated vaccines are promising candidates against different strains of MARV, and a novel fully humanized neutralizing antibody against MARV was isolated.

Viral vectored vaccines: design, development, preventive and therapeutic applications in human diseases

Human diseases, particularly infectious diseases and cancers, pose unprecedented challenges to public health security and the global economy. The development and distribution of novel prophylactic and therapeutic vaccines are the prioritized countermeasures of human disease. Among all vaccine platforms, viral vector vaccines offer distinguished advantages and represent prominent choices for pathogens that have hampered control efforts based on conventional vaccine approaches. Currently, viral vector vaccines remain one of the best strategies for induction of robust humoral and cellular immunity against human diseases. Numerous viruses of different families and origins, including vesicular stomatitis virus, rabies virus, parainfluenza virus, measles virus, Newcastle disease virus, influenza virus, adenovirus and poxvirus, are deemed to be prominent viral vectors that differ in structural characteristics, design strategy, antigen presentation capability, immunogenicity and protective efficacy. This review summarized the overall profile of the design strategies, progress in advance and steps taken to address barriers to the deployment of these viral vector vaccines, simultaneously highlighting their potential for mucosal delivery, therapeutic application in cancer as well as other key aspects concerning the rational application of these viral vector vaccines. Appropriate and accurate technological advances in viral vector vaccines would consolidate their position as a leading approach to accelerate breakthroughs in novel vaccines and facilitate a rapid response to public health emergencies.

Viral Vectors in Gene Therapy: Where Do We Stand in 2023?

Viral vectors have been used for a broad spectrum of gene therapy for both acute and chronic diseases. In the context of cancer gene therapy, viral vectors expressing anti-tumor, toxic, suicide and immunostimulatory genes, such as cytokines and chemokines, have been applied. Oncolytic viruses, which specifically replicate in and kill tumor cells, have provided tumor eradication, and even cure of cancers in animal models. In a broader meaning, vaccine development against infectious diseases and various cancers has been considered as a type of gene therapy. Especially in the case of COVID-19 vaccines, adenovirus-based vaccines such as ChAdOx1 nCoV-19 and Ad26.COV2.S have demonstrated excellent safety and vaccine efficacy in clinical trials, leading to Emergency Use Authorization in many countries. Viral vectors have shown great promise in the treatment of chronic diseases such as severe combined immunodeficiency (SCID), muscular dystrophy, hemophilia, β-thalassemia, and sickle cell disease (SCD). Proof-of-concept has been established in preclinical studies in various animal models. Clinical gene therapy trials have confirmed good safety, tolerability, and therapeutic efficacy. Viral-based drugs have been approved for cancer, hematological, metabolic, neurological, and ophthalmological diseases as well as for vaccines. For example, the adenovirus-based drug Gendicine® for non-small-cell lung cancer, the reovirus-based drug Reolysin® for ovarian cancer, the oncolytic HSV T-VEC for melanoma, lentivirus-based treatment of ADA-SCID disease, and the rhabdovirus-based vaccine Ervebo against Ebola virus disease have been approved for human use.

Gene Therapy Cargoes Based on Viral Vector Delivery

Viral vectors have been proven useful in a broad spectrum of gene therapy applications due to their possibility to accommodate foreign genetic material for both local and systemic delivery. The wide range of viral vectors has enabled gene therapy applications for both acute and chronic diseases. Cancer gene therapy has been addressed by the delivery of viral vectors expressing anti-tumor, toxic, and suicide genes for the destruction of tumors. Delivery of immunostimulatory genes such as cytokines and chemokines has also been applied for cancer therapy. Moreover, oncolytic viruses specifically replicating in and killing tumor cells have been used as such for tumor eradication or in combination with tumor killing or immunostimulatory genes. In a broad meaning, vaccines against infectious diseases and various cancers can be considered gene therapy, which has been highly successful, not the least for the development of effective COVID-19 vaccines. Viral vector-based gene therapy has also demonstrated encouraging and promising results for chronic diseases such as severe combined immunodeficiency (SCID), muscular dystrophy, and hemophilia. Preclinical gene therapy studies in animal models have demonstrated proof-of-concept for a wide range of disease indications. Clinical evaluation of drugs and vaccines in humans has showed high safety levels, good tolerance, and therapeutic efficacy. Several gene therapy drugs such as the adenovirus-based drug Gendicine® for non-small-cell lung cancer, the reovirus-based drug Reolysin® for ovarian cancer, lentivirus-based treatment of SCID-X1 disease, and the rhabdovirus-based vaccine Ervebo against Ebola virus disease, and adenovirus-based vaccines against COVID-19 have been developed.

Interleukin-25 enhances humoral immune responses caused by the rabies virus

Rabies is an important zoonotic disease caused by the rabies virus (RABV). Currently, no effective treatment is available for this condition. The prevention and control of rabies mainly depend on effective vaccination. Therefore, it is crucial to enhance the immune responses induced by the rabies vaccine. Virus neutralizing antibodies (VNA) induced by rabies vaccines are important for the clearance of RABV. Interleukin-25 (IL-25) has been demonstrated to activate T helper type 2 cells that contribute to humoral immune responses. The IL-25 gene was inserted into the genome of RABV, and the immunogenicity of recombinant RABV with IL-25 gene was investigated to develop more efficient rabies vaccines. Here, we found that the expression of IL-25 did not affect RABV production in vitro and pathogenicity in vivo. However, recombinant RABV expression of IL-25 induced a better VNA level than the parental virus in mice. In addition, expression of IL-25 enhanced the IgG1 level induced by RABV. Furthermore, mice immunized with recombinant RABV showed a higher survival rate and milder clinical signs than those immunized with the parent strain after challenge with CVS-11. Thus, these results showed that IL-25 could enhance the humoral immune responses induced by RABV, suggesting that IL-25 can be used as a viral vaccine adjuvant.

Establishment of Human-Induced Pluripotent Stem Cell-Derived Neurons-A Promising In Vitro Model for a Molecular Study of Rabies Virus and Host Interaction

Rabies is a deadly viral disease caused by the rabies virus (RABV), transmitted through a bite of an infected host, resulting in irreversible neurological symptoms and a 100% fatality rate in humans. Despite many aspects describing rabies neuropathogenesis, numerous hypotheses remain unanswered and concealed. Observations obtained from infected primary neurons or mouse brain samples are more relevant to human clinical rabies than permissive cell lines; however, limitations regarding the ethical issue and sample accessibility become a hurdle for discovering new insights into virus-host interplays. To better understand RABV pathogenesis in humans, we generated human-induced pluripotent stem cell (hiPSC)-derived neurons to offer the opportunity for an inimitable study of RABV infection at a molecular level in a pathologically relevant cell type. This study describes the characteristics and detailed proteomic changes of hiPSC-derived neurons in response to RABV infection using LC-MS/MS quantitative analysis. Gene ontology (GO) enrichment of differentially expressed proteins (DEPs) reveals temporal changes of proteins related to metabolic process, immune response, neurotransmitter transport/synaptic vesicle cycle, cytoskeleton organization, and cell stress response, demonstrating fundamental underlying mechanisms of neuropathogenesis in a time-course dependence. Lastly, we highlighted plausible functions of heat shock cognate protein 70 (HSC70 or HSPA8) that might play a pivotal role in regulating RABV replication and pathogenesis. Our findings acquired from this hiPSC-derived neuron platform help to define novel cellular mechanisms during RABV infection, which could be applicable to further studies to widen views of RABV-host interaction.

Glial cell response to Epstein-Barr Virus infection: A plausible contribution to virus-associated inflammatory reactions in the brain

Epstein-Barr Virus (EBV) is clinically related to various neurological ailments. The manipulation of neural homeostasis through altered glial cells functions is enigmatic. We investigated EBV mediated nuances in glial cells through direct infection (group-1) or by supplementing them with EBV-infected lymphocytes (PBMCs) supernatant (group-3). Also, the cells were co-cultured with infected PBMCs (group-2). Upon confirmation of infection in U-87 MG through qRT-PCR, the gene expression of crucial molecules was analysed. We reported enhanced expression of IL6 in group-1 and 3 unlike group-2. PBMCs migrated and invaded the matrigel significantly when exposed to group-1 and 3 conditions. Thus, EBV may aid neuroinflammatory reactions through PBMCs infiltration. Also, the exposure of neurons to conditioned supernatant from group-2 caused reduced neuronal healing. Additionally, group-1 milieu contained chemical modulators that induced glial cells death and reduced NF-κB. Conclusively, the three modes of EBV infection can influence glial cells' functions to maneuver the microenvironment distinctly.

Artesunate and Dihydroartemisinin Inhibit Rabies Virus Replication

Rabies is caused by infection of rabies virus (RABV) and remains a serious threat to the global public health. Except for the requirement for cold chain and high cost of human rabies immune globulin, no small molecule drugs are currently available for clinical treatment of rabies. So, it is of great importance to identify novel compounds that can effectively inhibit RABV infection. Artesunate (ART) and dihydroartemisinin (DHA), two derivatives of artemisinin, are widely used for treatment of malaria in adults and children, showing high safety. In this study, we found that both ART and DHA were able to inhibit RABV replication in host cells at a low concentration (0.1 μmol/L). The antiviral effects of ART and DHA were independent of viral strains and cell lines. Pre-treatment with ART or DHA for 2 h in vitro did not affect the viral replication in host cells, implying that ART and DHA neither reduced the viability of RABV directly nor inhibited the binding and entrance of the virus to host cells. Further studies revealed that ART and DHA inhibited RABV genomic RNA synthesis and viral gene transcription. Treatment with ART or DHA (5 mg/kg) by intramuscular injection improved, to some extent, the survival rate of RABV-challenged mice. Combination treatment with derivatives of artemisinin and mannitol significantly improved the survival rate of RABV-challenged mice. The results suggest that ART and DHA have a great potential to be explored as new anti-rabies agents for treatment of rabies.

Generation of a recombinant rabies virus expressing green fluorescent protein for a virus neutralization antibody assay

BACKGROUND

Fluorescent antibody virus neutralization (FAVN) test is a standard assay for quantifying rabies virus-neutralizing antibody (VNA) in serum. However, a safer rabies virus (RABV) should be used in the FAVN assay. There is a need for a new method that is economical and time-saving by eliminating the immunostaining step.

OBJECTIVES

We aimed to improve the traditional FAVN method by rescuing and characterizing a new recombinant RABV expressing green fluorescent protein (GFP).

METHODS

A new recombinant RABV expressing GFP designated as ERAGS-GFP was rescued using a reverse genetic system. Immuno-fluorescence assay, peroxidase-linked assay, electron microscopy and reverse transcription polymerase chain reaction were performed to confirm the recombinant ERAGS-GFP virus as a RABV expressing the GFP gene. The safety of ERAGS-GFP was evaluated in 4-week-old mice. The rabies VNA titers were measured and compared with conventional FAVN and FAVN-GFP tests using VERO cells.

RESULTS

The virus propagated in VERO cells was confirmed as RABV expressing GFP. The ERAGS-GFP showed the highest titer (10^8.0 TCID₅₀/mL) in VERO cells at 5 days post-inoculation, and GFP expression persisted until passage 30. The body weight of 4-week-old mice inoculated intracranially with ERAGS-GFP continued to increase and the survival rate was 100%. In 62 dog sera, the FAVN-GFP result was significantly correlated with that of conventional FAVN (r = 0.95).

CONCLUSIONS

We constructed ERAGS-GFP, which could replace the challenge virus standard-11 strain used in FAVN test.

Rhabdovirus Infection Is Dependent on Serine/Threonine Kinase AP2-Associated Kinase 1

Rabies virus (RABV) causes a fatal neurological disease in both humans and animals. Understanding the mechanism of RABV infection is vital for prevention and therapy of virulent rabies infection. Our previous proteomics analysis based on isobaric tags for relative and absolute quantitation to identify factors revealed that RABV infection enhanced AP-2-associated protein kinase 1 (AAK1) in N2a cells. In this study, to further confirm the role of AAK1, we showed that RABV infection increased the transcription and expression of AAK1 in N2a cells. AAK1 knockdown significantly decreased RABV infection in both N2a and BHK-21 cells. AAK1 knockout inhibited RABV infection in N2a cells. Furthermore, inhibition of AAK1 kinase activity using sunitinib decreased RABV infection. However, AAK1 overexpression did not change RABV infection in vitro. Therapeutic administration of sunitinib did not significantly improve the survival rate of mice following lethal RABV challenge. In addition, AAK1 knockdown decreased infection in N2a cells by vesicular stomatitis virus, which is another rhabdovirus. These results indicate that rhabdovirus infection is dependent on AAK1 and inhibition of AAK1 is a potential strategy for the prevention and therapy of rabies.

Single amino acid change at position 255 in rabies virus glycoprotein decreases viral pathogenicity

Previous studies have indicated that the amino acid at position 333 in the glycoprotein (G) is closely related to rabies virus (RABV) pathogenicity. However, whether there are other amino acid residues in G that relate to pathogenicity remain unclear. The aim of this study is to find new amino acid residues in G that could strongly reduce RABV pathogenicity. The present study found that the pathogenicity of a virulent strain was strongly attenuated when the amino acid glycine (Gly) replaced the aspartic acid (Asp) at position 255 in G (D255G) as intracranial (i.c.) infection with this D255G mutant virus did not cause death in adult mice. The indexes of neurotropism of the D255G mutant strain and the parent GD-SH-01 are 0.72 and 10.0, respectively, which indicate that the D255G mutation decreased the neurotropism of RABV. In addition, the D255G mutation significantly decreased RABV replication in the mouse brain. Furthermore, the D255G mutation enhanced the immune response in mice, which contributed to the clearance of RABV after infection. The Asp255 → Gly255 mutation was genetically stable in vitro and in vivo. In this study, we describe a new referenced amino acid site in G that relates to the pathogenicity of RABV.

The Deoptimization of Rabies Virus Matrix Protein Impacts Viral Transcription and Replication

Rabies virus (RABV) matrix (M) protein plays several important roles during RABV infection. Although previous studies have assessed the functions of M through gene rearrangements, this interferes with the position of other viral proteins. In this study, we attenuated M expression through deoptimizing its codon usage based on codon pair bias in RABV. This strategy more objectively clarifies the role of M during virus infection. Codon-deoptimized M inhibited RABV replication during the early stages of infection, but enhanced viral titers at later stages. Codon-deoptimized M also inhibited genome synthesis at early stage of infection and increased the RABV transcription rates. Attenuated M through codon deoptimization enhanced RABV glycoprotein expression following RABV infection in neuronal cells, but had no influence on the cell-to-cell spread of RABV. In addition, codon-deoptimized M virus induced higher levels of apoptosis compared to the parental RABV. These results indicate that codon-deoptimized M increases glycoprotein expression, providing a foundation for further investigation of the role of M during RABV infection.

Phenotypic Consequence of Rearranging the N Gene of RABV HEP-Flury

Nucleoprotein (N) is a key element in rabies virus (RABV) replication. To further investigate the effect of N on RABV, we manipulated an infectious cDNA clone of the RABV HEP-Flury to rearrange the N gene from its wild-type position of 1 (N-P-M-G-L) to 2 (P-N-M-G-L), 3 (P-M-N-G-L), or 4 (P-M-G-N-L), using an approach that left the viral nucleotide sequence unaltered. Subsequently, viable viruses were recovered from each of the rearranged cDNA and examined for their gene expression levels, growth kinetics in cell culture, pathogenicity in suckling mice and protection in mice. The results showed that gene rearrangement decreased N mRNA transcription and vRNA replication. As a result, all viruses with rearranged genomes showed worse replication than that of rHEP-Flury in NA cells at a MOI of 0.01, but equivalent or slightly better replication levels at a MOI of 3. Consequently, the lethality in suckling mice infected with N4 was clearly attenuated compared with rHEP-Flury. However, the protection to mice was not enhanced. This study not only gives us insight into the understanding of the phenotype of RABV N gene rearrangement, but also helps with rabies vaccine candidate construction.

A new recombinant rabies virus expressing a green fluorescent protein: A novel and fast approach to quantify virus neutralizing antibodies

The Rapid Fluorescent Focus Inhibition Test (RFFIT) is a standard assay used to detect and assess the titers of rabies virus neutralizing antibodies (RVNA) in blood sera. To simplify the multistep RFFIT procedure by eliminating the immunostaining step, we generated a new recombinant RV expressing a green fluorescent protein (rRV-GFP) and assess its suitability for quantifying RVNA. We rescued the rRV-GFP virus from plasmid DNA carrying a full-length genome of the CVS-N2c strain of RV in which the eGFP gene was inserted between the glycoprotein and RNA-polymerase genes. The recombinant virus was genetically stable and grew efficiently in appropriate cells expressing sufficient GFP fluorescence to detect directly 20 h post infection (hpi). We evaluated the feasibility of using rRV-GFP in RFFIT by comparing RVNA titers in 27 serum samples measured by conventional RFFIT and RFFIT-GFP. A linear regression analysis of the data demonstrated a good agreement between these two methods (r = 0.9776) including results with samples having RVNA titers close to the minimally acceptable vaccine potency threshold (0.5 IU/ml). Study results showed that the rRV-GFP virus could replace the CVS-11 challenge virus currently used in the conventional RFFIT and enabling more rapid, simpler, and less expensive detection and quantitation of RVNA.

Recombinant rabies virus expressing interleukin-6 enhances the immune response in mouse brain

Rabies, which is caused by the rabies virus (RABV), is an ancient zoonosis that has a high mortality rate. Previous studies have indicated that recombinant RABV expressing canine interleukin-6 (rHEP-CaIL6), induced more virus-neutralizing antibodies than parental RABV in mice following intramuscular immunization. To investigate the immune response induced in the CNS by rHEP-CaIL6 after intranasal or intracranial administration in mice, the permeability of the blood-brain barrier (BBB), the infiltration of CD3 T cells, and innate immune response-related effector molecules in the CNS were examined. It was observed that infection of rHEP-CaIL6 led to enhanced BBB permeability following intranasal infection. More CD3 T cells infiltrated into the central nervous system (CNS) in mice infected with rHEP-CaIL6 than in those infected with the HEP-Flury strain. Furthermore, rHEP-CaIL6 induced an increased expression of innate immune response-related effector molecules, compared with the parental HEP-Flury strain, within the CNS. Taken together, these findings suggest that rHEP-CaIL6 induced stronger immune responses in mice brains, which is more beneficial for virus clearance. These results may also partly illustrate the role of IL6 in RABV infection.

Near-infrared fluorescent protein iRFP720 is optimal for in vivo fluorescence imaging of rabies virus infection

In vivo imaging is a noninvasive method that enables real-time monitoring of viral infection dynamics in a small animal, which allows a better understanding of viral pathogenesis. In vivo bioluminescence imaging of virus infection is widely used but, despite its advantage over bioluminescence that no substrate administration is required, fluorescence imaging is not used because of severe autofluorescence. Recently, several far-red and near-infrared (NIR) fluorescent proteins (FPs) have been developed and shown to be useful for whole-body fluorescence imaging. Here, we report comparative testing of far-red and NIR FPs in the imaging of rabies virus (RABV) infection. Using the highly neuroinvasive 1088 strain, we generated recombinant RABV that expressed FPs such as Katushka2S, E2-Crimson, iRFP670 or iRFP720. After intracerebral inoculation to nude mice, the 1088 strain expressing iRFP720, the most red-shifted FP, was detected the earliest with the highest signal-to-noise ratio using a filter set for >700 nm, in which the background signal level was very low. Furthermore, we could also track viral dissemination from the spinal cord to the brain in nude mice after intramuscular inoculation of iRFP720-expressing 1088 into the hind limb. Hence, we conclude that the NIR FP iRFP720 used with a filter set for >700 nm is useful for in vivo fluorescence imaging not only for RABV infection but also for other virus infections. Our findings will also be useful for developing dual-optical imaging of virus-host interaction dynamics using bioluminescence reporter mice for inflammation imaging.

Phenotypic Consequences In vivo and In vitro of Rearranging the P Gene of RABV HEP-Flury

Phosphoprotein (P) of the Rabies virus (RABV) is critically required for viral replication and pathogenicity. Here we manipulated infectious cDNA clones of the RABV HEP-Flury to translocate the P gene from its wild-type position 2 to 1, 3, or 4 in gene order, using an approach which left the viral nucleotide sequence unaltered. The recovered viruses were evaluated for the levels of gene expression, growth kinetics in cell culture, lethality in suckling mice and protection of mice. The results showed that viral replication was affected by the absolute value of N protein which was regulated by P protein. Viral lethality in suckling mice was consistent with the ratio of P mRNA in one complete transcription. The protection of mice induced by viruses was related to the antibody titer 5 weeks post-infection which might be regulated by G protein. However, the ability to induce cell apoptosis and viral spread were not only related to the viral replication but also to the ratio of related gene which affected by the gene position. These findings might not only improve the understanding of phenotype of RABV and P gene rearrangement, but also help rabies vaccine candidate construction.

Two potential recombinant rabies vaccines expressing canine parvovirus virion protein 2 induce immunogenicity to canine parvovirus and rabies virus

Both rabies virus (RABV) and canine parvovirus (CPV) cause lethal diseases in dogs. In this study, both high egg passage Flury (HEP-Flury) strains of RABV and recombinant RABV carrying double RABV glycoprotein (G) gene were used to express the CPV virion protein 2 (VP2) gene, and were designated rHEP-VP2 and, rHEP-dG-VP2 respectively. The two recombinant RABVs maintained optimal virus titration according to their viral growth kinetics assay compared with the parental strain HEP-Flury. Western blotting indicated that G protein and VP2 were expressed in vitro. The expression of VP2 in Crandell feline kidney cells post-infection by rHEP-VP2 and rHEP-dG-VP2 was confirmed by indirect immunofluorescence assay with antibody against VP2. Immunogenicity of recombinant rabies viruses was tested in Kunming mice. Both rHEP-VP2 and rHEP-dG-VP2 induced high levels of rabies antibody compared with HEP-Flury. Mice immunized with rHEP-VP2 and rHEP-dG-VP2 both had a high level of antibodies against VP2, which can protect against CPV infection. A challenge experiment indicated that more than 80% mice immunized with recombinant RABVs survived after infection of challenge virus standard 24 (CVS-24). Together, this study showed that recombinant RABVs expressing VP2 induced protective immune responses to RABV and CPV. Therefore, rHEP-VP2 and rHEP-dG-VP2 might be potential combined vaccines for RABV and CPV.