Bat Bites and Rabies PEP in the Croatian Reference Centre for Rabies 1995-2020.

Seroprevalence of lyssaviruses in certain bat species has been proven in the Republic of Croatia, but there have been no confirmed positive bat brain isolates or human fatalities associated with bat injuries/bites. The study included a retrospective analysis of bat injuries/bites, post-exposure prophylaxis (PEP) and geographic distribution of bat injuries in persons examined at the Zagreb Antirabies Clinic, the Croatian Reference Centre for Rabies. In the period 1995-2020, we examined a total of 21,910 patients due to animal injuries, of which 71 cases were bat-related (0.32%). Of the above number of patients, 4574 received rabies PEP (20.87%). However, for bat injuries, the proportion of patients receiving PEP was significantly higher: 66 out of 71 patients (92.95%). Of these, 33 received only the rabies vaccine, while the other 33 patients received the vaccine with human rabies immunoglobulin (HRIG). In five cases, PEP was not administered, as there was no indication for treatment. Thirty-five of the injured patients were biologists or biology students (49.29%). The bat species was confirmed in only one of the exposure cases. This was a serotine bat (Eptesicus serotinus), a known carrier of Lyssavirus hamburg. The results showed that the bat bites were rather sporadic compared to other human injuries caused by animal bites. All bat injuries should be treated as if they were caused by a rabid animal, and according to WHO recommendations. People who come into contact with bats should be strongly advised to be vaccinated against rabies. Entering bat habitats should be done with caution and in accordance with current recommendations, and nationwide surveillance should be carried out by competent institutions and in close collaboration between bat experts, epidemiologists and rabies experts.

Single Amino Acid Substitution in the Matrix Protein of Rabies Virus Is Associated with Neurovirulence in Mice.

Rabies is a fatal encephalitic infectious disease caused by the rabies virus (RABV). RABV is highly neurotropic and replicates in neuronal cell lines in vitro. The RABV fixed strain, HEP-Flury, was produced via passaging in primary chicken embryonic fibroblast cells. HEP-Flury showed rapid adaptation when propagated in mouse neuroblastoma (MNA) cells. In this study, we compared the growth of our previously constructed recombinant HEP (rHEP) strain-based on the sequence of the HEP (HEP-Flury) strain-with that of the original HEP strain. The original HEP strain exhibited higher titer than rHEP and a single substitution at position 80 in the matrix (M) protein M(D80N) after incubation in MNA cells, which was absent in rHEP. In vivo, intracerebral inoculation of the rHEP-M(D80N) strain with this substitution resulted in enhanced viral growth in the mouse brain and a significant loss of body weight in the adult mice. The number of viral antigen-positive cells in the brains of adult mice inoculated with the rHEP-M(D80N) strain was significantly higher than that with the rHEP strain at 5 days post-inoculation. Our findings demonstrate that a single amino acid substitution in the M protein M(D80N) is associated with neurovirulence in mice owing to adaptation to mouse neuronal cells.

Evaluation of LN34 Pan-Lyssavirus RT-qPCR assay for rabies diagnosis in Brazil.

Rabies, a fatal zoonotic viral disease affecting mammals, including humans, remains a significant global health concern, particularly in low-income countries. The disease, primarily transmitted through infected animal saliva, prompts urgent diagnosis for timely post-exposure prophylaxis (PEP). The gold standard diagnostic test, direct fluorescent antibody test (dFAT), while sensitive, suffers from limitations such as subjective interpretation and high costs. As a confirmatory technique, the LN34 Pan-Lyssavirus RT-qPCR assay has emerged as a promising tool for universal Lyssavirus detection. This study evaluated its performance using 130 rabies virus isolates representing eleven Brazilian variants and 303 clinical samples from surveillance operations. The LN34 assay demonstrated 100% sensitivity and 98% specificity compared to dFAT. Additionally, it detected all samples, including those missed by dFAT, indicating superior sensitivity. The assay's specificity was confirmed through Sanger nucleotide sequencing, with only a minimal false-positive rate. Comparative analysis revealed higher accuracy and concordance with dFAT than traditional rabies tissue culture infection tests (RTCIT). False-negative RTCIT results were attributed to low viral load or suboptimal sampling. These findings underscore the LN34 assay's utility as a confirmatory technique, enhancing rabies surveillance and control in Brazil. Its widespread adoption could significantly improve diagnostic sensitivity, crucial for effective PEP and public health interventions.

Construction of Vero cell-adapted rabies vaccine strain by five amino acid substitutions in HEP-Flury strain.

Rabies virus (RABV) causes fatal neurological disease. Pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) using inactivated-virus vaccines are the most effective measures to prevent rabies. In Japan, HEP-Flury, the viral strain, used as a human rabies vaccine, has historically been propagated in primary fibroblast cells derived from chicken embryos. In the present study, to reduce the cost and labor of vaccine production, we sought to adapt the original HEP-Flury (HEP) to Vero cells. HEP was repeatedly passaged in Vero cells to generate ten- (HEP-10V) and thirty-passaged (HEP-30V) strains. Both HEP-10V and HEP-30V grew significantly better than HEP in Vero cells, with virulence and antigenicity similar to HEP. Comparison of the complete genomes with HEP revealed three non-synonymous mutations in HEP-10V and four additional non-synonymous mutations in HEP-30V. Comparison among 18 recombinant HEP strains constructed by reverse genetics and vesicular stomatitis viruses pseudotyped with RABV glycoproteins indicated that the substitution P(L115H) in the phosphoprotein and G(S15R) in the glycoprotein improved viral propagation in HEP-10V, while in HEP-30V, G(V164E), G(L183P), and G(A286V) in the glycoprotein enhanced entry into Vero cells. The obtained recombinant RABV strain, rHEP-PG4 strain, with these five substitutions, is a strong candidate for production of human rabies vaccine.

Three in one: An effective and universal vaccine expressing heterologous tandem RBD trimer by rabies virus vector protects mice against SARS-CoV-2.

The rapid emergence of Severe Acute Respiratory Syndrome Coronavirus type 2 (SARS-CoV-2) variants, coupled with severe immune evasion and imprinting, has jeopardized the vaccine efficacy, necessitating urgent development of broad protective vaccines. Here, we propose a strategy employing recombinant rabies viruses (RABV) to create a universal SARS-CoV-2 vaccine expressing heterologous tandem receptor-binding domain (RBD) trimer from the SARS-CoV-2 Prototype, Delta, and Omicron strains (SRV-PDO). The results of mouse immunization indicated that SRV-PDO effectively induced cellular and humoral immune responses, and demonstrated higher immunogenicity and broader SARS-CoV-2 neutralization compared to the recombinant RABVs that only expressed RBD monomers. Moreover, SRV-PDO exhibited full protection against SARS-CoV-2 in the challenge assay. This study demonstrates that recombinant RABV expressing tandem RBD-heterotrimer as a multivalent immunogen could elicit a broad-spectrum immune response and potent protection against SARS-CoV-2, making it a promising candidate for future human or veterinary vaccines and offering a novel perspective in other vaccine design.

TRIM44 Promotes Rabies Virus Replication by Autophagy-Dependent Mechanism.

Tripartite motif (TRIM) proteins are a multifunctional E3 ubiquitin ligase family that participates in various cellular processes. Recent studies have shown that TRIM proteins play important roles in regulating host-virus interactions through specific pathways, but their involvement in response to rabies virus (RABV) infection remains poorly understood. Here, we identified that several TRIM proteins are upregulated in mouse neuroblastoma cells (NA) after infection with the rabies virus using RNA-seq sequencing. Among them, TRIM44 was found to regulate RABV replication. This is supported by the observations that downregulation of TRIM44 inhibits RABV replication, while overexpression of TRIM44 promotes RABV replication. Mechanistically, TRIM44-induced RABV replication is brought about by activating autophagy, as inhibition of autophagy with 3-MA attenuates TRIM44-induced RABV replication. Additionally, we found that inhibition of autophagy with rapamycin reverses the TRIM44-knockdown-induced decrease in LC3B expression and autophagosome formation as well as RABV replication. The results suggest that TRIM44 promotes RABV replication by an autophagy-dependent mechanism. Our work identifies TRIM44 as a key host factor for RABV replication, and targeting TRIM44 expression may represent an effective therapeutic strategy.

Comparison of 4 laboratory tests for the detection of bovine rabies viral infection in Paraguay: fluorescent antibody test, rapid detection test, histologic lesions, and RT-PCR.

Rabies virus (RABV; Lyssavirus rabies) is a neurotropic virus that can be transmitted to mammals by the hematophagous bat Desmodus rotundus. An accurate, accessible method for the detection of RABV in cattle is necessary in Paraguay; thus, we evaluated the detection of RABV using 4 techniques: fluorescent antibody test (FAT), immunochromatography rapid detection test (RDT; Anigen Rapid Rabies Ag test kit; Bionote), a reverse-transcription PCR (RT-PCR) assay, and histologic lesions in different portions of the CNS of 49 Paraguayan cattle to determine the most sensitive and specific technique. By FAT and RDT, 15 of 49 (31%) samples were positive. By RT-PCR amplification of N and G genes, 13 of 49 (27%) and 12 of 49 (25%) were positive, respectively. RDT had high agreement with FAT (kappa = 1); sensitivity was 100% (95% CI: 97-100%) and specificity was 100% (95% CI: 99-100%). The amplification of the N and G genes resulted in substantial agreement (kappa of 0.9 and 0.8, respectively) compared with FAT, and the sensitivity and specificity of the N gene were 87% (95% CI: 66-100%) and 100% (95% CI: 98-100%), respectively, and those of the G gene were 80% (95% CI: 56-100%) and 100% (95% CI: 98-100%), respectively. Histologic lesions observed were lymphoplasmacytic meningoencephalitis, gliosis, and neuronophagia. The agreement observed between the FAT and RDT tests suggests that RDT is an accurate tool for the detection of RABV. Histopathology can be used to confirm lesions caused by RABV and to rule out other conditions; the RT-PCR assay is useful for molecular epidemiology studies.

Immunogenicity evaluation of a bivalent vaccine based on a recombinant rabies virus expressing gB protein of FHV-1 in mice and cats.

Feline viral rhinotracheitis (FVR) is caused by the feline herpesvirus-1 (FHV-1), which commonly results in upper respiratory symptoms, and can result in death in the kittens and weak cats. Rabies is an infectious disease with zoonotic characteristics highly relevant to public health and also poses a serious threat to cats. Vaccines are the most effective method to control the spread of both FHV-1 and RABV and have the advantage that they produce long-term specific immune responses. In this study, we constructed a bivalent vaccine against FHV-1 and rabies virus (RABV) simultaneously. The vaccine was constructed by cloning FHV-1 gB into a RABV based vector, and the recombinant RABV (SRV9-FHV-gB) expressing the FHV-1 gB protein was rescued. The growth characteristics of SRV9-FHV-gB were analyzed on NA and BSR cells. To assess the immunogenicity of the vaccine, mice and cats were immunized with SRV9-FHV-gB supplemented with Gel02 adjuvant. The SRV9-FHV-gB exhibited the same growth characteristics as the parent virus SRV9 in both BSR cells and NA cells. The safety of SRV9-FHV-gB was evaluated using 5-day-old and 14-day-old suckling mice. The results showed that mice infected with the SRV9-FHV-gB survived for longer than those in the SRV9 group. Mice immunized with inactivated SRV9-FHV-gB produced high titers of specific antibodies against FHV-1 and neutralizing antibodies against RABV. Cats that received three immunizations with SRV9-FHV-gB also produced neutralizing antibodies against both FHV-1 and RABV. This study represents the first time that a bivalent vaccine targeting FHV-1 and RABV has been constructed, laying the foundations and providing inspiration for the development of other multivalent vaccines.

Comparative analysis of rabies pathogenic and vaccine strains detection by RIG-I-like receptors.

Rabies virus (RABV) is a lethal neurotropic virus that causes 60,000 human deaths every year globally. RABV infection is characterized by the suppression of the interferon (IFN)-mediated antiviral response. However, molecular mechanisms leading to RABV sensing by RIG-I-like receptors (RLR) that initiates IFN signaling currently remain elusive. Here, we showed that RABV RNAs are primarily recognized by the RIG-I RLR, resulting in an IFN response in the infected cells, but this response varied according to the type of RABV used. Pathogenic RABV strain RNAs, Tha, were poorly detected in the cytosol by RIG-I and therefore caused a weak antiviral response. However, we revealed a strong IFN activity triggered by the attenuated RABV vaccine strain RNAs, SAD, mediated by RIG-I. We characterized two major 5' copy-back defective interfering (5'cb DI) genomes generated during SAD replication. Furthermore, we identified an interaction between 5'cb DI genomes, and RIG-I correlated with a high stimulation of the type I IFN signaling. This study indicates that wild-type RABV RNAs poorly activate the RIG-I pathway, while the presence of 5'cb DIs in the live-attenuated vaccine strain serves as an intrinsic adjuvant that strengthens its efficiency by enhancing RIG-I detection thus strongly stimulates the IFN response.

Targeted Repair of Spinal Cord Injury Based on miRNA-124-3p-Loaded Mesoporous Silica Camouflaged by Stem Cell Membrane Modified with Rabies Virus Glycoprotein.

Spinal cord injury (SCI) has no effective treatment modalities. It faces a significant global therapeutical challenge, given its features of poor axon regeneration, progressive local inflammation, and inefficient systemic drug delivery due to the blood-spinal cord barrier (BSCB). To address these challenges, a new nano complex that achieves targeted drug delivery to the damaged spinal cord is proposed, which contains a mesoporous silica nanoparticle core loaded with microRNA and a cloaking layer of human umbilical cord mesenchymal stem cell membrane modified with rabies virus glycoprotein (RVG). The nano complex more readily crosses the damaged BSCB with its exosome-resembling properties, including appropriate size and a low-immunogenic cell membrane disguise and accumulates in the injury center because of RVG, where it releases abundant microRNAs to elicit axon sprouting and rehabilitate the inflammatory microenvironment. Culturing with nano complexes promotes axonal growth in neurons and M2 polarization in microglia. Furthermore, it showed that SCI mice treated with this nano complex by tail vein injection display significant improvement in axon regrowth, microenvironment regulation, and functional restoration. The efficacy and biocompatibility of the targeted delivery of microRNA by nano complexes demonstrate their immense potential as a noninvasive treatment for SCI.

A flowchart for adequate controls in virus-based monosynaptic tracing experiments identified Cre-independent leakage of the TVA receptor in RΦGT mice.

BACKGROUND: A pseudotyped modified rabies virus lacking the rabies glycoprotein (G-protein), which is crucial for transsynaptic spread, can be used for monosynaptic retrograde tracing. By coupling the pseudotyped virus with transgene expression of the G-protein and the avian leukosis and sarcoma virus subgroup A receptor (TVA), which is necessary for cell entry of the virus, researchers can investigate specific neuronal populations. Responder mouse lines, like the RΦGT mouse line, carry the genes encoding the G-protein and TVA under Cre-dependent expression. These mouse lines are valuable tools because they reduce the number of viral injections needed compared to when using helper viruses. Since RΦGT mice do not express Cre themselves, introducing the pseudotyped rabies virus into their brain should not result in viral cell entry or spread. RESULTS: We present a straightforward flowchart for adequate controls in tracing experiments, which we employed to demonstrate Cre-independent expression of TVA in RΦGT mice. CONCLUSIONS: Our observations revealed TVA leakage, indicating that RΦGT mice should be used with caution for transgene expression of TVA. Inaccurate tracing outcomes may occur if TVA is expressed in the absence of Cre since background leakage leads to nonspecific cell entry. Moreover, conducting appropriate control experiments can identify the source of potential caveats in virus-based neuronal tracing experiments.

Lyssavirus M protein degrades neuronal microtubules by reprogramming mitochondrial metabolism.

Infection with neurotropic viruses may result in changes in host behavior, which are closely associated with degenerative changes in neurons. The lyssavirus genus comprises highly neurotropic viruses, including the rabies virus (RABV), which has been shown to induce degenerative changes in neurons, marked by the self-destruction of axons. The underlying mechanism by which the RABV degrades neuronal cytoskeletal proteins remains incomplete. In this study, we show that infection with RABV or overexpression of its M protein can disrupt mitochondrial metabolism by binding to Slc25a4. This leads to a reduction in NAD+ production and a subsequent influx of Ca2+ from the endoplasmic reticulum and mitochondria into the cytoplasm of neuronal cell lines, activating Ca2+-dependent proteinase calpains that degrade α-tubulin. We further screened the M proteins of different lyssaviruses and discovered that the M protein of the dog-derived RABV strain (DRV) does not degrade α-tubulin. Sequence analysis of the DRV M protein and that of the lab-attenuated RABV strain CVS revealed that the 57th amino acid is vital for M-induced microtubule degradation. We generated a recombinant RABV with a mutation at the 57th amino acid position in its M protein and showed that this mutation reduces α-tubulin degradation in vitro and axonal degeneration in vivo. This study elucidates the mechanism by which lyssavirus induces neuron degeneration.IMPORTANCEPrevious studies have suggested that RABV (rabies virus, the representative of lyssavirus) infection induces structural abnormalities in neurons. But there are few articles on the mechanism of lyssavirus' effect on neurons, and the mechanism of how RABV infection induces neurological dysfunction remains incomplete. The M protein of lyssavirus can downregulate cellular ATP levels by interacting with Slc25a4, and this decrease in ATP leads to a decrease in the level of NAD+ in the cytosol, which results in the release of Ca2+ from the intracellular calcium pool, the endoplasmic reticulum, and mitochondria. The presence of large amounts of Ca2+ in the cytoplasm activates Ca2+-dependent proteases and degrades microtubule proteins. The amino acid 57 of M protein is the key site determining its disruption of mitochondrial metabolism and subsequent neuron degeneration.

Rabies virus-based barcoded neuroanatomy resolved by single-cell RNA and in situ sequencing.

Mapping the connectivity of diverse neuronal types provides the foundation for understanding the structure and function of neural circuits. High-throughput and low-cost neuroanatomical techniques based on RNA barcode sequencing have the potential to map circuits at cellular resolution and a brain-wide scale, but existing Sindbis virus-based techniques can only map long-range projections using anterograde tracing approaches. Rabies virus can complement anterograde tracing approaches by enabling either retrograde labeling of projection neurons or monosynaptic tracing of direct inputs to genetically targeted postsynaptic neurons. However, barcoded rabies virus has so far been only used to map non-neuronal cellular interactions in vivo and synaptic connectivity of cultured neurons. Here we combine barcoded rabies virus with single-cell and in situ sequencing to perform retrograde labeling and transsynaptic labeling in the mouse brain. We sequenced 96 retrogradely labeled cells and 295 transsynaptically labeled cells using single-cell RNA-seq, and 4130 retrogradely labeled cells and 2914 transsynaptically labeled cells in situ. We found that the transcriptomic identities of rabies virus-infected cells can be robustly identified using both single-cell RNA-seq and in situ sequencing. By associating gene expression with connectivity inferred from barcode sequencing, we distinguished long-range projecting cortical cell types from multiple cortical areas and identified cell types with converging or diverging synaptic connectivity. Combining in situ sequencing with barcoded rabies virus complements existing sequencing-based neuroanatomical techniques and provides a potential path for mapping synaptic connectivity of neuronal types at scale.

In the brain, messages are relayed from one cell to the next through intricate networks of axons and dendrites that physically interact at junctions known as synapses. Mapping out this synaptic connectivity ­ that is, exactly which neurons are connected via synapses ­ remains a major challenge. Monosynaptic tracing is a powerful approach that allows neuroscientists to explore neural networks by harnessing viruses which spread between neurons via synapses, in particular the rabies virus. This pathogen travels exclusively from 'postsynaptic' to 'presynaptic' neurons ­ from the cell that receives a message at a synapse, back to the one that sends it. A modified variant of the rabies virus can therefore be used to reveal the presynaptic cells connecting to a population of neurons in which it has been originally introduced. However, this method does not allow scientists to identify the exact postsynaptic neuron that each presynaptic cell is connected to. One way to bypass this issue is to combine monosynaptic tracing with RNA barcoding to create distinct versions of the modified rabies virus, which are then introduced into separate populations of neurons. Tracking the spread of each version allows neuroscientists to spot exactly which presynaptic cells signal to each postsynaptic neuron. So far, this approach has been used to examine synaptic connectivity in neurons grown in the laboratory, but it remains difficult to apply it to neurons in the brain. In response, Zhang, Jin et al. aimed to demonstrate how monosynaptic tracing that relies on barcoded rabies viruses could be used to dissect neural networks in the mouse brain. First, they confirmed that it was possible to accurately detect which version of the virus had spread to presynaptic neurons using both in situ and single-cell RNA sequencing. Next, they described how this information could be analysed to build models of potential neural networks, and what type of additional experiments are required for this work. Finally, they used the approach to identify neurons that tend to connect to the same postsynaptic cells and then investigated what these have in common, showing how the technique enables a finer understanding of neural circuits. Overall, the work by Zhang, Jin et al. provides a comprehensive review of the requirements and limitations associated with monosynaptic tracing experiments based on barcoded rabies viruses, as well as how the approach could be optimized in the future. This information will be of broad interest to scientists interested in mapping neural networks in the brain.

A modified recombinant adenovirus vector containing dual rabies virus G expression cassettes confers robust and long-lasting humoral immunity in mice, cats, and dogs.

During the COVID-19 epidemic, the incidence of rabies has increased in several countries, especially in remote and disadvantaged areas, due to inadequate surveillance and declining immunization coverage. Multiple vaccinations with inactivated rabies virus vaccines for pre- or post-exposure prophylaxis are considered inefficient, expensive and impractical in developing countries. Herein, three modified human recombinant adenoviruses type 5 designated Adv-RVG, Adv-E1-RVG, and Adv-RVDG, carrying rabies virus G (RVG) expression cassettes in various combinations within E1 or E3 genomic regions, were constructed to serve as rabies vaccine candidates. Adv-RVDG mediated greater RVG expression both in vitro and in vivo and induced a more robust and durable humoral immune response than the rabies vaccine strain SAD-L16, Adv-RVG, and Adv-E1-RVG by more effectively activating the dendritic cells (DCs) - follicular helper T (Tfh) cells - germinal centre (GC) / memory B cells (MBCs) - long-lived plasma cells (LLPCs) axis with 100% survival after a lethal RABV challenge in mice during the 24-week study period. Similarly, dogs and cats immunized with Adv-RVDG showed stronger and longer-lasting antibody responses than those vaccinated with a commercial inactivated rabies vaccine and showed good tolerance to Adv-RVDG. In conclusion, our study demonstrated that simultaneous insertion of protective antigens into the E1 and E3 genomic regions of adenovirus vector can significantly enhance the immunogenicity of adenoviral-vectored vaccines, providing a theoretical and practical basis for the subsequent development of multivalent and multi-conjugated vaccines using recombinant adenovirus platform. Meanwhile, our data suggest Adv-RVDG is a safe, efficient, and economical vaccine for mass-coverage immunization.

Long-term labeling and imaging of synaptically connected neuronal networks in vivo using double-deletion-mutant rabies viruses.

Rabies-virus-based monosynaptic tracing is a widely used technique for mapping neural circuitry, but its cytotoxicity has confined it primarily to anatomical applications. Here we present a second-generation system for labeling direct inputs to targeted neuronal populations with minimal toxicity, using double-deletion-mutant rabies viruses. Viral spread requires expression of both deleted viral genes in trans in postsynaptic source cells. Suppressing this expression with doxycycline following an initial period of viral replication reduces toxicity to postsynaptic cells. Longitudinal two-photon imaging in vivo indicated that over 90% of both presynaptic and source cells survived for the full 12-week course of imaging. Ex vivo whole-cell recordings at 5 weeks postinfection showed that the second-generation system perturbs input and source cells much less than the first-generation system. Finally, two-photon calcium imaging of labeled networks of visual cortex neurons showed that their visual response properties appeared normal for 10 weeks, the longest we followed them.

Sf9 Cell Metabolism Throughout the Recombinant Baculovirus and Rabies Virus-Like Particles Production in Two Culture Systems.

This work aimed to assess the Sf9 cell metabolism during growth, and infection steps with recombinant baculovirus bearing rabies virus proteins, to finally obtain rabies VLP in two culture systems: Schott flask (SF) and stirred tank reactor (STR). Eight assays were performed in SF and STR (four assays in each system) using serum-free SF900 III culture medium. Two non-infection growth kinetics assays and six recombinant baculovirus infection assays. The infection runs were carried out at 0.1 pfu/cell multiplicity of infection (MOI) for single baculovirus bearing rabies glycoprotein (BVG) and matrix protein (BVM) and a coinfection with both baculoviruses at MOI of 3 and 2 pfu/cell for BVG and BVM, respectively. The SF assays were done in triplicate. The glucose, glutamine, glutamate, lactate, and ammonium uptake or release specific rates were quantified over the exponential growth phase and infection stage. The highest uptake specific rate was observed for glucose (42.5 × 10-12 mmol cell/h) in SF and for glutamine (30.8 × 10-12 mmol/cell/h) in STR, in the exponential growth phases. A wave pattern was observed for assessed analytes throughout the infection phase and the glucose had the highest wave amplitude within the 10-10 mmol cell/h order. This alternative uptake and release behavior is in harmony with the lytic cycle of baculovirus in insect cells. The virus propagation and VLP generation were not limited by glucose, glutamine, and glutamate, neither by the toxicity of lactate nor ammonium under the conditions appraised in this work. The findings from this work can be useful to set baculovirus infection processes at high cell density to improve rabies VLP yield, purity, and productivity.

Development of a novel multi-epitope oral DNA vaccine for rabies based on a food-borne microbial vector.

Rabies has been with humans for a long time, and its special transmission route and almost 100 % lethality rate made it once a nightmare for humans. In this study, by predicting the rabies virus glycoprotein outer membrane region and nucleoprotein B-cell antigenic epitopes, the coding sequence of the predicted highly antigenic polypeptide region obtained was assembled using the eukaryotic expression vector pcDNA3.1(-), and then E. coli was used as the delivery vector. The immunogenicity and protective properties of the vaccine were verified by in vivo and in vitro experiments, which demonstrated that the vaccine could produce antibodies in mice and prolong the survival time of mice exposed to the strong virus without any side effects. This study demonstrated that the preparation of an oral rabies DNA vaccine using food-borne microorganisms as a transport vehicle is feasible and could be a new strategy to eradicate rabies starting with wild animals.

Phylogenetic relationship between rabies virus (Lyssavirus rabies) variants from two different species / Relações filogenéticas do vírus da raiva (Lyssavirus rabies) em duas diferentes espécies / Relaciones filogenéticas del virus de la rabia (Lyssavirus rabies) en dos especies diferentes

Rabies is a fatal zoonotic disease that affects several mammals. Hematophagous bats are recognized hosts of the rabies virus, and their main food source is the blood of other mammals, particularly cattle. During feeding, bats transmit the virus to cattle, which are victims of the disease, contributing to economic losses and increasing the risk of infection for humans. Based on this affinity in the rabies cycle between bats and cattle, the objective of this study was to analyze the phylogenetic relationships of rabies virus samples in cattle and bats. The G gene of the rabies virus was chosen for this study because it is directly related to the infection process. Nucleotide sequences of the viral G gene were selected from GenBank for samples obtained from infected cattle and bats. Maximum parsimony analyses were conducted using the Molecular Evolutionary Genetics Analysis software. The Maxima Parsimony tree indicated a phylogenetic relationship between the G genes of both hosts, indicating that the virus evolved from bats to cattle. Analysis of parsimoniously informative sites revealed that the viral G gene carried specific mutations in each host. Knowledge of the evolutionary relationships between the rabies virus and its hosts is critical for identifying potential new hosts and the possible routes of infection for humans.

A Raiva é uma zoonose fatal que infecta várias espécies de mamíferos. Os morcegos hematófagos são reconhecidos como hospedeiros do vírus da Raiva e sua principal fonte de alimento é o sangue de outros mamíferos, especialmente os bovinos. Quando se alimentam, os morcegos transmitem o vírus para o bovino os quais são vítimas da doença, contribuindo para perdas econômicas e riscos de infecção para humanos. Baseado nesta afinidade do ciclo da Raiva entre morcegos e bovinos, o objetivo deste estudo foi analisar as relações filogenéticas de amostras do vírus da Raiva em ambos os hospedeiros, bovinos e morcegos. O gene G do vírus da Raiva foi escolhido para esta pesquisa porque ele está diretamente relacionado ao processo de infecção. Sequências de nucleotídeos do gene G viral foram selecionadas no GenBank a partir de amostras obtidas de bovinos e morcegos infectados. Análises de Máxima Parcimônia foram conduzidas utilizando o software Molecular Evolutionary Genetics Analysis. A árvore de Máxima Parcimônia indicou uma relação filogenética entre o gene G de ambos os hospedeiros, indicando que o vírus evoluiu dos morcegos para os bovinos. A análise dos sítios parcimoniosamente informativos revelou que o gene G viral apresentou mutações específicas em cada hospedeiro. O conhecimento sobre as relações evolutivas do vírus da Raiva e seus hospedeiros é crucial para identificar nos hospedeiros potenciais e novas rotas possíveis de infecção para humanos.

La rabia es una zoonosis fatal que infecta a varias especies de mamíferos. Los murciélagos hematófagos son reconocidos como huéspedes del virus de la rabia y su principal fuente de alimentación es la sangre de otros mamíferos, especialmente del ganado. Al alimentarse, los murciélagos transmiten el virus al ganado que es víctima de la enfermedad, contribuyendo a pérdidas económicas y riesgos de infección para los humanos. Basado en esta afinidad del ciclo de la rabia entre murciélagos y ganado, el objetivo de este estudio fue analizar las relaciones filogenéticas de las muestras de virus de la rabia tanto en huéspedes, ganado y murciélagos. El gen G del virus de la rabia fue elegido para esta investigación porque está directamente relacionado con el proceso de infección. Las secuencias de nucleótidos del gen G viral se seleccionaron en GenBank a partir de muestras obtenidas de bovinos y murciélagos infectados. Los análisis de parsimonia máxima se realizaron utilizando el software Molecular Evolutionary Genetics Analysis. El árbol de Máxima Parsimônia indicó una relación filogenética entre el gen G de ambos huéspedes, indicando que el virus evolucionó de murciélagos a bovinos. El análisis de los sitios parsimoniosamente informativos reveló que el gen G viral presentaba mutaciones específicas en cada huésped. El conocimiento sobre las relaciones evolutivas del virus de la rabia y sus huéspedes es crucial para identificar huéspedes potenciales y nuevas posibles rutas de infección para humanos.

High risk of bat bites in an indigenous village in Brazil: Warning of the re-emergence of rabies among the Maxakali People.

Bat-mediated human rabies is a viral zoonotic disease that poses a serious threat to the public health of traditional peoples, especially indigenous populations that maintain primitive cultural and social habits, such as the Maxakali ethnic group, located in the southeastern region of Brazil. The sociocultural habit of this population led to the emergence between April and May 2022 of the viral spillover of rabies transmitted by bats, which decimated the lives of four children from this population who maintained contact with this animal as a recreational practice. Because the vampire bats Desmodus rotundus have exceptional ecology and social characteristics that can have important effects on the dynamics of viral dispersion in this indigenous population, I present the dynamics of contact between native children and the bat and the meaning of this relationship, which involves ritualistic and recreational significance. As important as knowing the reasons for this practice is discussing some intrinsic and extrinsic factors that imply risks that intensify the vulnerability of this population to the transmission of the rabies virus at any time. In view of this, I warn of the need to adopt efficient strategies to mitigate the risks of a new emergency in this region. Although emergency containment measures were carried out during the critical period of the outbreak, such animal and environmental control actions must become routine programmatic and structuring interventions. Essential for rabies surveillance in this population is to develop culturally adapted interethnic health education campaigns to guarantee the accessibility of the Maxakali indigenous people to the content taught, so that any attempt at domestication, captivity and recreational practices with bats of any species is discouraged, thus avoiding a possible re-emergence of this anthropozoonosis that has impacted not only the epidemiological scenario in this region, but throughout Brazil, and also throughout Latin America.

Genomic stability of self-inactivating rabies.

Transsynaptic viral vectors provide means to gain genetic access to neurons based on synaptic connectivity and are essential tools for the dissection of neural circuit function. Among them, the retrograde monosynaptic ΔG-Rabies has been widely used in neuroscience research. A recently developed engineered version of the ΔG-Rabies, the non-toxic self-inactivating (SiR) virus, allows the long term genetic manipulation of neural circuits. However, the high mutational rate of the rabies virus poses a risk that mutations targeting the key genetic regulatory element in the SiR genome could emerge and revert it to a canonical ΔG-Rabies. Such revertant mutations have recently been identified in a SiR batch. To address the origin, incidence and relevance of these mutations, we investigated the genomic stability of SiR in vitro and in vivo. We found that "revertant" mutations are rare and accumulate only when SiR is extensively amplified in vitro, particularly in suboptimal production cell lines that have insufficient levels of TEV protease activity. Moreover, we confirmed that SiR-CRE, unlike canonical ΔG-Rab-CRE or revertant-SiR-CRE, is non-toxic and that revertant mutations do not emerge in vivo during long-term experiments.