Human BST2 inhibits rabies virus release independently of cysteine-linked dimerization and asparagine-linked glycosylation.

The innate immune response is a first-line defense mechanism triggered by rabies virus (RABV). Interferon (IFN) signaling and ISG products have been shown to confer resistance to RABV at various stages of the virus's life cycle. Human tetherin, also known as bone marrow stromal cell antigen 2 (hBST2), is a multifunctional transmembrane glycoprotein induced by IFN that has been shown to effectively counteract many viruses through diverse mechanisms. Here, we demonstrate that hBST2 inhibits RABV budding by tethering new virions to the cell surface. It was observed that release of virus-like particles (VLPs) formed by RABV G (RABV-G VLPs), but not RABV M (RABV-G VLPs), were suppressed by hBST2, indicating that RABV-G has a specific effect on the hBST2-mediated restriction of RABV. The ability of hBST2 to prevent the release of RABV-G VLPs and impede RABV growth kinetics is retained even when hBST2 has mutations at dimerization and/or glycosylation sites, making hBST2 an antagonist to RABV, with multiple mechanisms possibly contributing to the hBST2-mediated suppression of RABV. Our findings expand the knowledge of host antiviral mechanisms that control RABV infection.

Manipulative neuroparasites: uncovering the intricacies of neurological host control.

Manipulative neuroparasites are a fascinating group of organisms that possess the ability to hijack the nervous systems of their hosts, manipulating their behavior in order to enhance their own survival and reproductive success. This review provides an overview of the different strategies employed by manipulative neuroparasites, ranging from viruses to parasitic worms and fungi. By examining specific examples, such as Toxoplasma gondii, Leucochloridium paradoxum, and Ophiocordyceps unilateralis, we highlight the complex mechanisms employed by these parasites to manipulate their hosts' behavior. We explore the mechanisms through which these parasites alter the neural processes and behavior of their hosts, including the modulation of neurotransmitters, hormonal pathways, and neural circuits. This review focuses less on the diseases that neuroparasites induce and more on the process of their neurological manipulation. We also investigate the fundamental mechanisms of host manipulation in the developing field of neuroparasitology, which blends neuroscience and parasitology. Finally, understanding the complex interaction between manipulative neuroparasites and their hosts may help us to better understand the fundamentals of behavior, neurology, and host-parasite relationships.

A Novel Mouse Model for Polysynaptic Retrograde Tracing and Rabies Pathological Research.

Retrograde tracing is an important method for dissecting neuronal connections and mapping neural circuits. Over the past decades, several virus-based retrograde tracers have been developed and have contributed to display multiple neural circuits in the brain. However, most of the previously widely used viral tools have focused on mono-transsynaptic neural tracing within the central nervous system, with very limited options for achieving polysynaptic tracing between the central and peripheral nervous systems. In this study, we generated a novel mouse line, GT mice, in which both glycoprotein (G) and ASLV-A receptor (TVA) were expressed throughout the body. Using this mouse model, in combination with the well-developed rabies virus tools (RABV-EnvA-ΔG) for monosynaptic retrograde tracing, polysynaptic retrograde tracing can be achieved. This allows functional forward mapping and long-term tracing. Furthermore, since the G-deleted rabies virus can travel upstream against the nervous system as the original strain, this mouse model can also be used for rabies pathological studies. Schematic illustrations about the application principles of GT mice in polysynaptic retrograde tracing and rabies pathological research.

Canine rabies: An epidemiological significance, pathogenesis, diagnosis, prevention, and public health issues.

Rabies is a zoonotic disease caused by rabies virus of the genus Lyssa virus and family Rhabdoviridae. It affects all mammals and is prevalent throughout the world and endemic in many countries except in Islands like Australia and Antarctica. It is highly fatal, but preventable. Disease causes threat to public health because rabid dogs bite humans, resulting in thousands of deaths every year. Around 59,000 people die every year from rabies in the world. Dogs play a vital role in most of the human exposure in rabies endemic areas. Transmission of virus occurs through the bite of an infected dog. Disease is manifested by fatal nervous symptoms leading to paralysis and death. Direct fluorescent antibody technique is the gold standard for the diagnosis of the disease in animals and humans. Prevention of rabies involves the vaccination of dogs and humans before or after an exposure. This review describes the etiology, pathogenesis, diagnosis, its prevention and control strategies.

RVG Peptide-Functionalized Favipiravir Nanoparticle Delivery System Facilitates Antiviral Therapy of Neurotropic Virus Infection in a Mouse Model.

Neurotropic viruses severely damage the central nervous system (CNS) and human health. Common neurotropic viruses include rabies virus (RABV), Zika virus, and poliovirus. When treating neurotropic virus infection, obstruction of the blood-brain barrier (BBB) reduces the efficiency of drug delivery to the CNS. An efficient intracerebral delivery system can significantly increase intracerebral delivery efficiency and facilitate antiviral therapy. In this study, a rabies virus glycopeptide (RVG) functionalized mesoporous silica nanoparticle (MSN) packaging favipiravir (T-705) was developed to generate T-705@MSN-RVG. It was further evaluated for drug delivery and antiviral treatment in a VSV-infected mouse model. The RVG, a polypeptide consisting of 29 amino acids, was conjugated on the nanoparticle to enhance CNS delivery. The T-705@MSN-RVG caused a significant decrease in virus titers and virus proliferation without inducing substantial cell damage in vitro. By releasing T-705, the nanoparticle promoted viral inhibition in the brain during infection. At 21 days post-infection (dpi), a significantly enhanced survival ratio (77%) was observed in the group inoculated with nanoparticle compared with the non-treated group (23%). The viral RNA levels were also decreased in the therapy group at 4 and 6 dpi compared with that of the control group. The T-705@MSN-RVG could be considered a promising system for CNS delivery for treating neurotropic virus infection.

Transferrin Receptor Protein 1 Cooperates with mGluR2 To Mediate the Internalization of Rabies Virus and SARS-CoV-2.

Identification of bona fide functional receptors and elucidation of the mechanism of receptor-mediated virus entry are important to reveal targets for developing therapeutics against rabies virus (RABV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Our previous studies suggest that metabotropic glutamate receptor subtype 2 (mGluR2) functions as an entry receptor for RABV in vitro, and is an important internalization factor for SARS-CoV-2 in vitro and in vivo. Here, we demonstrate that mGluR2 facilitates RABV internalization in vitro and infection in vivo. We found that transferrin receptor 1 (TfR1) interacts with mGluR2 and internalizes with mGluR2 and RABV in the same clathrin-coated pit. Knockdown of TfR1 blocks agonist-triggered internalization of mGluR2. Importantly, TfR1 also interacts with the SARS-CoV-2 spike protein and is important for SARS-CoV-2 internalization. Our findings identify a novel axis (mGluR2-TfR1 axis) used by RABV and SARS-CoV-2 for entry, and reveal TfR1 as a potential target for therapeutics against RABV and SARS-CoV-2. IMPORTANCE We previously found that metabotropic glutamate receptor subtype 2 (mGluR2) is an entry receptor for RABV in vitro, and an important internalization factor for SARS-CoV-2 in vitro and in vivo. However, whether mGluR2 is required for RABV infection in vivo was unknown. In addition, how mGluR2 mediates the internalization of RABV and SARS-CoV-2 needed to be resolved. Here, we found that mGluR2 gene knockout mice survived a lethal challenge with RABV. To our knowledge, mGluR2 is the first host factor to be definitively shown to play an important role in RABV street virus infection in vivo. We further found that transferrin receptor protein 1 (TfR1) directly interacts and cooperates with mGluR2 to regulate the endocytosis of RABV and SARS-CoV-2. Our study identifies a novel axis (mGluR2-TfR1 axis) used by RABV and SARS-CoV-2 for entry and opens a new door for the development of therapeutics against RABV and SARS-CoV-2.

Treat the "Untreatable" by a Photothermal Agent: Triggering Heat and Immunological Responses for Rabies Virus Inactivation.

Rabies is a fatal neurological zoonotic disease caused by the rabies virus (RABV), and the approved post-exposure prophylaxis (PEP) procedure remains unavailable in areas with inadequate medical systems. Although strategies have been proposed for PEP and postinfection treatment (PIT), because of the complexity of the treatment procedures and the limited curative outcome, developing an effective treatment strategy remains a holy grail in rabies research. Herein, a facile approach is proposed involving photothermal therapy (PTT) and photothermally triggered immunological effects to realize effective PEP and PIT simultaneously. The designed photothermal agent (N+ TT-mCB nanoparticles) featured positively charged functional groups and high photo-to-heat efficiency, which are favorable for virus targeting and inactivation. The level of the virus at the site of infection in mice is significantly decreased upon treatment with orthotopic PTT, and the transfer of the virus to the brain is significantly inhibited. Furthermore, the survival ratio of the mice three days postinfection is increased by intracranial injection of N+ TT-mCB and laser irradiation. Overall, this work provides a platform for the effective treatment of RABV and opens a new avenue for future antiviral studies.

Mitochondrial Dysfunction in Rabies Virus-Infected Human and Canine Brains.

Rabies is a fatal encephalitis caused by the Rabies lyssavirus (RABV). The presence of minimal neuropathological changes observed in rabies indicates that neuronal dysfunction, rather than neuronal death contributes to the fatal outcome. The role of mitochondrial changes has been suggested as a possible mechanism for neuronal dysfunction in rabies. However, these findings are mostly based on studies that have employed experimental models and laboratory-adapted virus. Studies on brain tissues from naturally infected human and animal hosts are lacking. The current study investigated the role of mitochondrial changes in rabies by morphological, biochemical and proteomic analysis of RABV-infected human and canine brains. Morphological analysis showed minimal inflammation with preserved neuronal and disrupted mitochondrial structure in both human and canine brains. Proteomic analysis revealed involvement of mitochondrial processes (oxidative phosphorylation, cristae formation, homeostasis and transport), synaptic proteins and autophagic pathways, with over-expression of subunits of mitochondrial respiratory complexes. Consistent with these findings, human and canine brains displayed elevated activities of complexes I (p < 0.05), IV (p < 0.05) and V (p < 0.05). However, this did not result in elevated ATP production (p < 0.0001), probably due to lowered mitochondrial membrane potential as noted in RABV-infected cells in culture. These could lead to mitochondrial dysfunction and mitophagy as indicated by expression of FKBP8 (p < 0.05) and PINK1 (p < 0.001)/PARKIN (p > 0.05) and ensuing autophagy, as shown by the status of LCIII (p < 0.05), LAMP1 (p < 0.001) and pertinent ultrastructural markers. We propose that altered mitochondrial bioenergetics and cristae architecture probably induce mitophagy, leading to autophagy and consequent neuronal dysfunction in rabies.

G protein-coupled receptor 17 restricts rabies virus replication via BAK-mediated apoptosis.

Rabies, caused by rabies virus (RABV), is an ancient zoonotic disease that significantly affects human and animal health throughout the world. RABV causes acute encephalitis in mammals with a high fatality rate in developing countries. G protein-coupled receptor 17 (GPR17) is a vital gene in the central nervous system (CNS) that plays important roles in demyelinating diseases and ischemia brain. However, it is still unclear whether GPR17 participates in the regulation of RABV infection. Here, we found that upregulation or activation of GPR17 can reduce the virus titer; conversely, the inactivation or silence of GPR17 led to increased RABV replication in N2a cells. The recombinant RABV expressing GPR17 (rRABV-GPR17) showed reduced replication capacity compared to the parent virus rRABV. Moreover, overexpression of GPR17 can attenuate RABV pathogenicity in mice. Further study demonstrated that GPR17 suppressed RABV replication via BAK-mediated apoptosis. Our findings uncover an unappreciated role of GPR17 in suppressing RABV infection, where GPR17 mediates cell apoptosis to limit RABV replication and may be an attractive candidate for new therapeutic interventions in the treatment of rabies.

Delineation of altered brain proteins associated with furious rabies virus infection in dogs by quantitative proteomics.

Rabies is a fatal zoonotic disease caused by rabies virus (RABV). Despite the existence of control measures, dog-transmitted human rabies accounts for ˃95% reported cases due to unavailability of sensitive diagnostic methods, inadequate understanding of disease progression and absence of therapeutics. In addition, host factors and their role in RABV infection are poorly understood. In this study, we used 8-plex iTRAQ coupled with HRMS approach to identify differentially abundant proteins (DAPs) of dog brain associated with furious rabies virus infection. Total 40 DAPs including 26 down-regulated and 14 up-regulated proteins were statistically significant in infected samples. GO annotation and IPA showed that calcium signaling and calcium transport, efficient neuronal function, metabolic pathway associated proteins were mostly altered during this infection. Total 34 proteins including 10 down-regulated proteins pertaining to calcium signaling and calcium transport pathways were successfully verified by qRT-PCR and two proteins were verified by western blot, thereby suggesting these pathways may play an important role in this infection. This study provides the map of altered brain proteins and some insights into the molecular pathophysiology associated with furious rabies virus infection. However, further investigations are required to understand their role in disease mechanism. SIGNIFICANCE: Transmission of rabies by dogs poses the greatest hazard world-wide and the rare survival of post-symptomatic patients as well as severe neurological and immunological problems pose a question to understand the molecular mechanism involved in rabies pathogenesis. However, information regarding host factors and their function in RABV infection is still inadequate. Our study has used an advanced quantitative proteomics approach i.e. 8-plex iTRAQ coupled with HRMS and identified 40 DAPs in furious rabies infected dog brain tissues compared to the controls. Further analysis showed that calcium signaling and transport pathway, efficient neuronal functions and metabolic pathway associated brain proteins were most altered during furious rabies virus infection. This data provides a map of altered brain proteins which may have role in furious rabies virus infection. Hence, this will improve our understanding of the molecular pathogenesis of RABV infection.

Lipid Droplets Are Beneficial for Rabies Virus Replication by Facilitating Viral Budding.

Rabies is an old zoonotic disease caused by rabies virus (RABV), but the pathogenic mechanism of RABV is still not completely understood. Lipid droplets (LDs) have been reported to play a role in pathogenesis of several viruses. However, their role in RABV infection remains unclear. Here, we initially found that RABV infection upregulated LD production in multiple cells and mouse brains. After treatment with atorvastatin, a specific inhibitor of LDs, RABV replication in N2a cells decreased. Then we found that RABV infection could upregulate N-myc downstream regulated gene-1 (NDRG1), which in turn enhanced the expression of diacylglycerol acyltransferase 1/2 (DGAT1/2). DGAT1/2 could elevate cellular triglyceride synthesis and ultimately promote intracellular LD formation. Furthermore, we found that RABV-M and RABV-G, which were mainly involved in the viral budding process, could colocalize with LDs, indicating that RABV might utilize LDs as a carrier to facilitate viral budding and eventually increase virus production. Taken together, our study reveals that lipid droplets are beneficial for RABV replication, and their biogenesis is regulated via the NDRG1-DGAT1/2 pathway, which provides novel potential targets for developing anti-RABV drugs. IMPORTANCE Lipid droplets have been proven to play an important role in viral infections, but their role in RABV infection has not yet been elaborated. Here, we find that RABV infection upregulates the generation of LDs by enhancing the expression of N-myc downstream regulated gene-1 (NDRG1). Then NDRG1 elevated cellular triglycerides synthesis by increasing the activity of diacylglycerol acyltransferase 1/2 (DGAT1/2), which promotes the biogenesis of LDs. RABV-M and RABV-G, which are the major proteins involved in viral budding, could utilize LDs as a carrier for transport to cell membrane, resulting in enhanced virus budding. Our findings will extend the knowledge of lipid metabolism in RABV infection and help to explore potential therapeutic targets for RABV.

Evaluating Surveillance for and Estimating Administration of Rabies Postexposure Prophylaxis in the United States, 2012-2018.

BACKGROUND: An evaluation of postexposure prophylaxis (PEP) surveillance has not been conducted in over 10 years in the United States. An accurate assessment would be important to understand current rabies trends and inform public health preparedness and response to human rabies. METHODOLOGY/PRINCIPLE FINDINGS: To understand PEP surveillance, we sent a survey to public health leads for rabies in 50 U.S. states, Puerto Rico, Washington DC, Philadelphia, and New York City. Of leads from 54 jurisdictions, 39 (72%) responded to the survey; 12 reported having PEP-specific surveillance, five had animal bite surveillance that included data about PEP, four had animal bite surveillance without data about PEP, and 18 (46%) had neither. Although 12 jurisdictions provided data about PEP use, poor data quality and lack of national representativeness prevented use of this data to derive a national-level PEP estimate. We used national-level and state specific data from the Healthcare Cost & Utilization Project (HCUP) to estimate the number of people who received PEP based on emergency department (ED) visits. The estimated annual average of initial ED visits for PEP administration during 2012-2017 in the United States was 46,814 (SE: 1,697), costing upwards of 165 million USD. State-level ED data for initial visits for administration of PEP for rabies exposure using HCUP data was compared to state-level surveillance data from Maryland, Vermont, and Georgia between 2012-2017. In all states, state-level surveillance data was consistently lower than estimates of initial ED visits, suggesting even states with robust PEP surveillance may not adequately capture individuals who receive PEP. CONCLUSIONS: Our findings suggest that making PEP a nationally reportable condition may not be feasible. Other methods of tracking administration of PEP such as syndromic surveillance or identification of sentinel states should be considered to obtain an accurate assessment.

Function of Host Protein Staufen1 in Rabies Virus Replication.

Rabies virus is a highly neurophilic negative-strand RNA virus with high lethality and remains a huge public health problem in developing countries to date. The double-stranded RNA-binding protein Staufen1 (STAU1) has multiple functions in RNA virus replication, transcription, and translation. However, its function in RABV infection and its mechanism of action are not clear. In this study, we investigated the role of host factor STAU1 in RABV infection of SH-SY-5Y cells. Immunofluorescence, TCID50 titers, confocal microscopy, quantitative real-time PCR and Western blotting were carried out to determine the molecular function and subcellular distribution of STAU1 in these cell lines. Expression of STAU1 in SH-SY-5Y cells was down-regulated by RNA interference or up-regulated by transfection of eukaryotic expression vectors. The results showed that N proficiently colocalized with STAU1 in SH-SY-5Y at 36 h post-infection, and the expression level of STAU1 was also proportional to the time of infection. Down-regulation of STAU1 expression increased the number of Negri body-like structures, enhanced viral replication, and a caused 10-fold increase in viral titers. Meanwhile, N protein and G protein mRNA levels also accumulated gradually with increasing infection time, which implied that STAU1 inhibited rabies virus infection of SH-SY-5Y cells in vitro. In conclusion, our results provide important clues for the detailed replication mechanism of rabies virus and the discovery of therapeutic targets.

Expression Profiling and Bioinformatics Analysis of CircRNA in Mice Brain Infected with Rabies Virus.

Rabies virus (RABV) induces acute, fatal encephalitis in mammals including humans. The circRNAs are important in virus infection process, but whether circRNAs regulated RABV infection remains largely unknown. Here, mice brain with or without the RABV CVS-11 strain were subjected to RNA sequencing and a total of 30,985 circRNAs were obtained. Among these, 9021 candidates were shared in both groups, and 14,610 and 7354 circRNAs were expressed specifically to the control and experimental groups, indicating that certain circRNAs were specifically inhibited or induced on RABV infection. The circRNAs mainly derived from coding exons. In total, 636 circRNAs were differentially expressed in RABV infection, of which 426 significantly upregulated and 210 significantly downregulated (p < 0.05 and fold change ≥2). The expression of randomly selected 6 upregulated and 6 downregulated circRNAs was tested by RT-qPCR, and the expression trend of the 11 out of 12 circRNAs was consistent in RT- qPCR and RNA-seq analysis. Rnase R-resistant assay and Sanger sequencing were conducted to verify the circularity of circRNAs. GO analysis demonstrated that source genes of all differentially regulated circRNAs were mainly related to cell plasticity and synapse function. Both KEGG and GSEA analysis revealed that these source genes were engaged in the cGMP-PKG and MAPK signaling pathway, and HTLV-I infection. Also, pathways related to glucose metabolism and synaptic functions were enriched in KEGG analysis. The circRNA-miRNA-mRNA network was built with 25 of 636 differentially expressed circRNAs, 264 mRNAs involved in RABV infection, and 29 miRNAs. Several miRNAs and many mRNAs in the network were reported to be related to viral infection and the immune response, suggesting that circRNAs could regulate RABV infection via interacting with miRNAs and mRNAs. Taken together, this study first characterized the transcriptomic pattern of circRNAs, and signaling pathways and function that circRNAs are involved in, which may indicate directions for further research to understand mechanisms of RABV pathogenesis.

Murine Ifit3 restricts the replication of Rabies virus both in vitro and in vivo.

Rabies virus (RABV) infection can initiate the host immune defence response and induce an antiviral state characterized by the expression of interferon (IFN)-stimulated genes (ISGs), among which the family of genes of IFN-induced protein with tetratricopeptide repeats (Ifits) are prominent representatives. Herein, we demonstrated that the mRNA and protein levels of Ifit1, Ifit2 and Ifit3 were highly increased in cultured cells and mouse brains after RABV infection. Recombinant RABV expressing Ifit3, designated rRABV-Ifit3, displayed a lower pathogenicity than the parent RABV in C57BL/6 mice after intramuscular administration, and Ifit3-deficient mice exhibited higher susceptibility to RABV infection and higher mortality during RABV infection. Moreover, compared with their individual expressions, co-expression of Ifit2 and Ifit3 could more effectively inhibit RABV replication in vitro. These results indicate that murine Ifit3 plays an essential role in restricting the replication and reducing the pathogenicity of RABV. Ifit3 acts synergistically with Ifit2 to inhibit RABV replication, providing further insight into the function and complexity of the Ifit family.

Rabies post-exposure healthcare-seeking behaviors and perceptions: Results from a knowledge, attitudes, and practices survey, Uganda, 2013.

BACKGROUND: Rabies is a viral disease of animals and people causing fatal encephalomyelitis if left untreated. Although effective pre- and post-exposure vaccines exist, they are not widely available in many endemic countries within Africa. Since many individuals in these countries remain at risk of infection, post-exposure healthcare-seeking behaviors are crucial in preventing infection and warrant examination. METHODOLOGY: A rabies knowledge, attitudes, and practices survey was conducted at 24 geographically diverse sites in Uganda during 2013 to capture information on knowledge concerning the disease, response to potential exposure events, and vaccination practices. Characteristics of the surveyed population and of the canine-bite victim sub-population were described. Post-exposure healthcare-seeking behaviors of canine-bite victims were examined and compared to the related healthcare-seeking attitudes of non-bite victim respondents. Wealth scores were calculated for each household, rabies knowledge was scored for each non-bitten survey respondent, and rabies exposure risk was scored for each bite victim. Logistic regression was used to determine the independent associations between different variables and healthcare-seeking behaviors among canine-bite victims as well as attitudes of non-bitten study respondents. RESULTS: A total of 798 households were interviewed, capturing 100 canine-bite victims and a bite incidence of 2.3 per 100 person-years. Over half of bite victims actively sought medical treatment (56%), though very few received rabies post-exposure prophylaxis (3%). Bite victims who did not know or report the closest location where PEP could be received were less likely to seek medical care (p = 0.05). Respondents who did not report having been bitten by a dog with higher knowledge scores were more likely to respond that they would both seek medical care (p = 0.00) and receive PEP (p = 0.06) after a potential rabies exposure event. CONCLUSIONS: There was varying discordance between what respondents who did not report having been bitten by a dog said they would do if bitten by a dog when compared to the behaviors exhibited by canine-bite victims captured in the KAP survey. Bite victims seldom elected to wash their wound or receive PEP. Having lower rabies knowledge was a barrier to theoretically seeking care and receiving PEP among not bitten respondents, indicating a need for effective and robust educational programs in the country.

A novel oral rabies vaccine enhances the immunogenicity through increasing dendritic cells activation and germinal center formation by expressing U-OMP19 in a mouse model.

Rabies remains a public health threat in most parts of the world. Dogs, especially stray dogs, are the main sources of rabies transmission in developing countries, while wild animals are primarily responsible for the spread of rabies in developed countries and play an emerging role in rabies transmission in developing countries. Oral vaccination is the most practical method for rabies control in these animals, and the greatest challenge for oral vaccination is the hostile environment and large quantity of proteases in the gastrointestinal tract. In the present study, a promising adjuvant with potential protease inhibitory activity, unlipidated outer membrane protein 19 (U-OMP19), was inserted into the genome of the recombinant rabies virus (rRABV) strain LBNSE, designated LBNSE-U-OMP19, and the immunogenicity of LBNSE-U-OMP19 was investigated. LBNSE-U-OMP19 could potentially protect viral glycoprotein from digestion by gastrointestinal fluids in vitro. The expression of U-OMP19 attenuated viral pathogenicity by restricting viral replication in the central nervous system (CNS) and repressing the production of inflammatory chemokines and cytokines. After oral vaccination, LBNSE-U-OMP19 recruited dendritic cells (DCs), follicular helper T (TFH) cells and germinal center (GC) B cells, promoted the formation of GCs, and increased the population of plasma cells in immunized mice, resulting in higher levels of RABV-neutralizing antibodies and better protection in mice immunized with LBNSE-U-OMP19 than in those immunized with the parent virus LBNSE. Together, our data suggest that LBNSE-U-OMP19 is a promising candidate for oral rabies vaccines.

Genome-based local dynamics of canine rabies virus epidemiology, transmission, and evolution in Davao City, Philippines, 2018-2019.

Rabies is a fatal zoonotic and neglected tropical disease caused by the rabies virus (RABV) and is associated with neuronal dysfunction and death, with dogs as the predominant carrier. The Philippines plans to eradicate rabies by 2022, but this is challenged with sub-optimal coverage of vaccination programs coupled with sustained transmission chains, making it unable to eradicate the disease. We investigated the dynamics of canine rabies in the highly urbanized Davao City of the Philippines and its neighboring localities by assessing genetic relationships, transmission patterns, selection pressure, and recombination events using the whole genome sequence of 49 RABV cases from June 2018 to May 2019, majority of which (46%) were from the district of Talomo, Davao City. Although phylogeographic clustering was observed, local variants also exhibited genetic sub-lineages. Phylogenetic and spatial transmission analysis provided evidence for intra- and inter-city transmission predominantly through the Talomo district of Davao City. Around 84% of the cases were owned dogs, but the genetic similiarity of RABVs from stray and owned dogs further alluded to the role of the former as transmission vectors. The high rate of improper vaccination among the affected dogs (80%) was also a likely contributor to transmission. The RABV population under Investigation is generally under strong purifying selection with no evidence of vaccine evasion due to the genetic homogeneity of viruses from vaccinated and improperly vaccinated dogs. However, some homologous recombination (HR) events were identified along the G and L genes, also predominantly associated with viruses from Talomo. The complementary findings on epidemiology, transmission, and recombination for Talomo suggest that high incidence areas can be seeds for virus dispersal and evolution. We recommend further Investigations on the possibility of HR in future large-scale genome studies. Finally, districts associated with these phenomena can be targeted for evidence-based local strategies that can help break RABV transmission chains and prevent emergence of novel strains in Davao City.

Modeling Mongoose Rabies in the Caribbean: A Model-Guided Fieldwork Approach to Identify Research Priorities.

We applied the model-guided fieldwork framework to the Caribbean mongoose rabies system by parametrizing a spatially-explicit, individual-based model, and by performing an uncertainty analysis designed to identify parameters for which additional empirical data are most needed. Our analysis revealed important variation in output variables characterizing rabies dynamics, namely rabies persistence, exposure level, spatiotemporal distribution, and prevalence. Among epidemiological parameters, rabies transmission rate was the most influential, followed by rabies mortality and location, and size of the initial infection. The most influential landscape parameters included habitat-specific carrying capacities, landscape heterogeneity, and the level of resistance to dispersal associated with topography. Movement variables, including juvenile dispersal, adult fine-scale movement distances, and home range size, as well as life history traits such as age of independence, birth seasonality, and age- and sex-specific mortality were other important drivers of rabies dynamics. We discuss results in the context of mongoose ecology and its influence on disease transmission dynamics. Finally, we suggest empirical approaches and study design specificities that would provide optimal contributing data addressing the knowledge gaps identified by our approach, and would increase our potential to use epidemiological models to guide mongoose rabies control and management in the Caribbean.

Street RABV Induces the Cholinergic Anti-inflammatory Pathway in Human Monocyte-Derived Macrophages by Binding to nAChr α7.

Rabies virus (RABV) is able to reach the central nervous system (CNS) without triggering a strong immune response, using multiple mechanisms to evade and suppress the host immune system. After infection via a bite or scratch from a rabid animal, RABV comes into contact with macrophages, which are the first antigen-presenting cells (APCs) that are recruited to the area and play an essential role in the onset of a specific immune response. It is poorly understood how RABV affects macrophages, and if the interaction contributes to the observed immune suppression. This study was undertaken to characterize the interactions between RABV and human monocyte-derived macrophages (MDMs). We showed that street RABV does not replicate in human MDMs. Using a recombinant trimeric RABV glycoprotein (rRABV-tG) we showed binding to the nicotinic acetylcholine receptor alpha 7 (nAChr α7) on MDMs, and confirmed the specificity using the nAChr α7 antagonist alpha-bungarotoxin (α-BTX). We found that this binding induced the cholinergic anti-inflammatory pathway (CAP), characterized by a significant decrease in tumor necrosis factor α (TNF-α) upon LPS challenge. Using confocal microscopy we found that induction of the CAP is associated with significant cytoplasmic retention of nuclear factor κB (NF-κB). Co-cultures of human MDMs exposed to street RABV and autologous T cells further revealed that the observed suppression of MDMs might affect their function as T cell activators as well, as we found a significant decrease in proliferation of CD8+ T cells and an increased production of the anti-inflammatory cytokine IL-10. Lastly, using flow cytometric analysis we observed a significant increase in expression of the M2-c surface marker CD163, hinting that street RABV might be able to affect macrophage polarization. Taken together, these results show that street RABV is capable of inducing an anti-inflammatory state in human macrophages, possibly affecting T cell functioning.