The molecular biology of rabies viruses

Analysis of the antigenic and immunogenic properties of the native rabies virus glycoprotein purified by Lens culinaris lectin affinity chromatography

Rabies virus glycoprotein (RABV-G) is responsible for the recognition of specific cell surface receptors and induces the production of neutralizing antibodies (VNA). Since RABV-G is a glycoprotein, this work aimed to evaluate Lens culinaris (LCA) chromatography as a simple and effective purification method. The purity and identification of the protein obtained were analyzed by SDS-PAGE, ELISA and lectin-binding assay. The antigenic properties of the purified RABV-G were evaluated by direct ELISA using human serum samples from individuals who had received rabies pre-exposure vaccination. For the immunogenicity study, Swiss Webster mice were immunized with purified RABV-G and the specific antibodies were measured by direct ELISA and RFFIT. As results, it was observed that the purified protein reveled a molecular mass of 55 kDa and the presence of carbohydrate; additionally, it was recognized by anti-rabies virus glycoprotein monoclonal antibody. Purified RABV-G induced high VNA titers (>50.0 IU/ml) in vivo, as detected by RFFIT, as well as RABV-G specific IgG1 (0.8 mean OD±SD) and IgG2a (0.3 mean OD±SD) antibodies, with a predominance of IgG1 (p< 0.001). In addition, it was observed that RABV-G was efficient in selectively detecting anti- RABV-G IgG in the sera of vaccinated individuals compared to the negative control. Therefore, LCA chromatography was efficient in preserving the native properties of RABV-G that are essential in inducing an adequate humoral immune response. In addition, the purified RABV-G presented analytical potential as an ELISA reagent.

The roles of rabies virus structural proteins in immune evasion and implications for vaccine development

Rabies is a zoonotic infectious disease that targets the nervous system of human and animals and has about 100% fatality rate without treatment. Rabies virus is a bullet-like viral particle composed of five structural proteins, including nucleoprotein (N), phosphorylated protein (P), matrix protein (M), glycoprotein (G), and large subunit (L) of RNA-dependent RNA polymerase. These multifunctional viral proteins also play critical roles in the immune escape by inhibiting specific immune responses in the host, resulting in massive replication of the virus in the nervous system and abnormal behaviors of patients such as brain dysfunction and hydrophobia, which ultimately lead to the death of patients. Herein, the role of five structural proteins of rabies virus in the viral replication and immune escape and its implication for the development of vaccines were systemically reviewed, so as to shed light on the understanding of pathogenic mechanism of rabies virus.

Apolipoprotein D facilitates rabies virus propagation by interacting with G protein and upregulating cholesterol

Rabies virus (RABV) causes a fatal neurological disease, consisting of unsegmented negative-strand RNA, which encodes five structural proteins (3'-N-P-M-G-L-5'). Apolipoprotein D (ApoD), a lipocalin, is upregulated in the nervous system after injury or pathological changes. Few studies have focused on the role of ApoD during virus infection so far. This study demonstrated that ApoD is upregulated in the mouse brain (in vivo) and C8-D1A cells (in vitro) after RABV infection. By upregulating ApoD expression in C8-D1A cells, we found that ApoD facilitated RABV replication. Additionally, Co-immunoprecipitation demonstrated that ApoD interacted with RABV glycoprotein (G protein). The interaction could promote RABV replication by upregulating the cholesterol level. These findings revealed a novel role of ApoD in promoting RABV replication and provided a potential therapeutic target for rabies.

Genetic characteristics and geographic distribution of rabies virus in China

China is one of the largest countries with endemic rabies. In this study, we examined the full-length genome sequences of 87 rabies virus (RABV) strains identified in China from 1931 to 2019. Chinese RABV isolates were divided into two major clades, GI and GII. Clade GI consisted of viruses from the Asian clade, which was further divided into three subclades: Asian1, Asian2, and Asian3. Clade GII consisted of viruses from the Cosmopolitan, Arctic-related, and Indian clades. A phylogeographic network showed that the variation of rabies virus was more closely associated with geographic location than with the host species. Recombination appears to be one of the factors driving the emergence of new viral strains.

Comparing the genetic typing methods for effective surveillance and rabies control in Georgia

A full nucleoprotein gene sequencing of 68 isolates collected from passive rabies surveillance system in Georgia between 2015 and 2016 identified two distinct dog rabies phylogroups, GEO_V1 and GEO_V2, which both belonged to the cosmopolitan dog clade. GEO_V1 was found throughout the country and was further divided into four sub-phylogroups that overlapped geographically; GEO_V2 was found in the southeast region and was closely related to dog rabies in Azerbaijan. A sequence analysis of the full N gene, partial nucleoprotein gene of N-terminal and C-terminal, and the amplicon sequences of pan-lyssavirus RT-qPCR LN34 showed that all four sequencing approaches provided clear genetic typing results of canine rabies and could further differentiate GEO_V1 and GEO_V2. The phylogenetic analysis results vary and were affected by the length of the sequences used. Amplicon sequencing of the LN34 assay positive samples provided a rapid and cost-effective method for rabies genetic typing, which is important for improving rabies surveillance and canine rabies eradication globally.

Retrospective phylogenetic analysis of rabies virus G and N genes from Serbia

Rabies is a viral disease of the central nervous system of all warm-blooded animals and one of the oldest and most important zoonoses. In the Republic of Serbia, rabies is controlled by compulsory vaccination of dogs and cats and oral vaccination of wild carnivores, which has been implemented since 2010. In the period 2009-2018, 367 rabies cases were recorded. The last rabies case in Serbia was recorded in 2018 in a red fox (Vulpes vulpes), while the last case in dogs was diagnosed in 2011. This study aimed to perform a retrospective phylogenetic analysis of G and N genes of the rabies virus from Serbia from 2009 to 2018 to understand sources and pathways of infection better and to enable molecular virus tracing in the future based on the association of rabies virus genetic lineages with the geographic distribution. For the phylogenetic analysis of the rabies virus, 14 historically positive brain samples of red foxes from 2009 to 2018, collected in central Serbia, were used. All field strains from Serbia were identified as classic rabies virus and grouped within the Cosmopolitan lineage. Phylogenetic analysis of N gene sequences revealed that 13 rabies virus strains (92.9%) from Serbia belonged to the EE sub-lineage of isolates, while one virus (7.1%) ON988027 from 2011 clustered together with isolates from the WE sub-lineage.

Genomic Surveillance of Rabies Virus in Georgian Canines

Rabies is a fatal zoonosis that is considered a re-emerging infectious disease. Although rabies remains endemic in canines throughout much of the world, vaccination programs have essentially eliminated dog rabies in the Americas and much of Europe. However, despite the goal of eliminating dog rabies in the European Union by 2020, sporadic cases of dog rabies still occur in Eastern Europe, including Georgia. To assess the genetic diversity of the strains recently circulating in Georgia, we sequenced seventy-eight RABV-positive samples from the brain tissues of rabid dogs and jackals using Illumina short-read sequencing of total RNA shotgun libraries. Seventy-seven RABV genomes were successfully assembled and annotated, with seventy-four of them reaching the coding-complete status. Phylogenetic analyses of the nucleoprotein (N) and attachment glycoprotein (G) genes placed all the assembled genomes into the Cosmopolitan clade, consistent with the Georgian origin of the samples. An amino acid alignment of the G glycoprotein ectodomain identified twelve different sequences for this domain among the samples. Only one of the ectodomain groups contained a residue change in an antigenic site, an R264H change in the G5 antigenic site. Three isolates were cultured, and these were found to be efficiently neutralized by the human monoclonal antibody A6. Overall, our data show that recently circulating RABV isolates from Georgian canines are predominantly closely related phylogroup I viruses of the Cosmopolitan clade. Current human rabies vaccines should offer protection against infection by Georgian canine RABVs. The genomes have been deposited in GenBank (accessions: OQ603609-OQ603685).

lncRNA EDAL restricts rabies lyssavirus replication in a cell-specific and infection route-dependent manner

Rabies, caused by rabies lyssavirus (RABV), is a fatal disease among humans and almost all warm-blooded animals. Our previous study showed that the long non-coding RNA (lncRNA) EZH2 degradation-associated lncRNA (EDAL) effectively inhibits RABV infection both in vitro and in vivo by degrading EZH2 and promoting the transcription of an antiviral gene, Pcp4l1. Herein, we found that recombinant RABV expressing EDAL (rRABV-EDAL) restricts RABV replication in primary granule neurons but not in primary cortical neurons or astrocytes. Further study revealed that EDAL induced EZH2 protein degradation and thereby decreased trimethylation of lysine 27 on the histone 3 (H3K27me3) level in granule neuron cells but not in cortical neurons or astrocytes. Furthermore, rRABV-EDAL infection induces more Pcp4l1 mRNA transcription in granule neurons, while there are almost no obvious changes in cortical neurons or astrocytes. Consistently, compared with the parent virus RABV, reduced pathogenicity of rRABV-EDAL was observed in mice post-intranasal infection but not intramuscular infection. These results suggest that the lncRNA EDAL restricts RABV replication in a cell-specific and infection route-dependent manner.

Quantitative characterization of the T cell receptor repertoires of human immunized by rabies virus vaccine

Cellular immunity is crucial for an efficient host immune response against rabies virus (RABV) infection. But the T cell receptor (TCR) repertoire in human after RABV vaccine immunization remained unclear. In this study, we conducted high-throughput sequencing of TCR β chain complementarity determining region 3(CDR3) repertoires in 4 healthy volunteers before and after immunization with RABV vaccine. Our data showed that RABV vaccination changed the TCR diversity and the usage of V/J gene segments, as well as V-J pairing. The high-frequency clonotypes that altered after vaccination were identified. These results may provide us with new insights into T cell receptor condition after RABV vaccination.

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.

Development of Monoclonal Antibodies for Detection of Conserved and Variable Epitopes of Large Protein of Rabies Virus

Rabies virus (RABV) causes fatal neurological encephalitis and results in approximately 6000 human death cases worldwide every year. The large (L) protein of RABV, possessing conserved domains, is considered as the target for detection. In this study, three monoclonal antibodies (mAbs), designated as 3F3, 3A6 and L-C, against L protein were generated by using the recombinant truncated L protein (aa 1431-1754) and the epitopes were also identified using a series of overlapping truncated polypeptides for testing the reactivity of mAbs with different RABV strains. The ¹⁴⁷⁹EIFSIP¹⁴⁸⁴, ¹⁶⁵⁹RALSK¹⁶⁶³ and ¹⁷²⁴VFNSL¹⁷²⁸ were identified as the minimal linear epitopes recognized by mAbs 3F3, 3A6 and L-C, respectively. Amino acid alignment showed epitope ¹⁷²⁴VFNSL¹⁷²⁸ recognized by mAb L-C is completely conserved among RABV strains, indicating that mAb L-C could be used to detect all of the RABV strains. Epitope ¹⁴⁷⁹EIFSIP¹⁴⁸⁴ is highly conserved among RABV strains except for a P1484S substitution in a China I sub-lineage strain of Asian lineage, which eliminated the reactivity of the epitope with mAb 3F3. However, the epitope ¹⁶⁵⁹RALSK¹⁶⁶³ was only completely conserved in the Africa-2 and Indian lineages, and a single A1660T substitution, mainly appeared in strains of the China I belonging to Asian lineage and a Cosmopolitan lineage strain, still retained the reactivity of the epitope with mAb 3A6. While both A1660T and K1663R substitutions in a China I lineage strain, single K1663R/Q substitution in some China II strains of Asian lineage and some Arctic-like lineage strains and R1659Q mutation in a strain of Africa-3 lineage eliminated the reactivity of the epitope with mAb 3A6, suggesting mAb 3A6 could be used for differentiation of variable epitopes of some strains in different lineages. Thus, variability and conservation of the three epitopes of L protein showed the reactive difference of mAbs among RABV strains of different lineages. These results may facilitate future studies in development of detection methods for RABV infection, the structure and function of RABV L protein.

Comparison of lncRNA and mRNA expression in mouse brains infected by a wild-type and a lab-attenuated Rabies lyssavirus

Rabies is a lethal disease caused by Rabies lyssavirus, commonly known as rabies virus (RABV), and results in nearly 100 % death once clinical symptoms occur in human and animals. Long non-coding RNAs (lncRNAs) have been reported to be associated with viral infection. But the role of lncRNAs involved in RABV infection is still elusive. In this study, we performed global transcriptome analysis of both of lncRNA and mRNA expression profiles in wild-type (WT) and lab-attenuated RABV-infected mouse brains by using next-generation sequencing. The differentially expressed lncRNAs and mRNAs were analysed by using the edgeR package. We identified 1422 differentially expressed lncRNAs and 4475 differentially expressed mRNAs by comparing WT and lab-attenuated RABV-infected brains. Then we predicted the enriched biological pathways by the Gene Ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) database based on the differentially expressed lncRNAs and mRNAs. Our analysis revealed the relationships between lncRNAs and RABV-infection-associated immune response and ion transport-related pathways, which provide a fresh insight into the potential role of lncRNA in immune evasion and neuron injury induced by WT RABV.

Efficient distribution of oral vaccines examined by infrared triggered camera for advancing the control of raccoon dog rabies in South Korea

The field distribution of the oral rabies vaccine is effective in controlling the spread of rabies. The present study aimed to investigate efficient distribution locations based on the environment, contact rate, and consumption by target wildlife species in South Korea. The target species (Korean raccoon dogs, domestic dogs, and feral cats) accounted for 945 contacts (52.2%), in total 1,808 contacts. There were 863 (47.8%) contacts by non-target species. Raccoon dogs, a main reservoir of rabies in South Korea, had the highest contact rate (34.1%) among all species. The contact rate by target species was highest at riparian sites and bushy mountainous vegetation, where raccoon dogs are abundant. There was remarkable contact by raccoon dogs in mountainous areas below 150 m with bushy vegetation. Our results indicate that these locations are efficient areas for vaccine distribution, especially targeting the raccoon dog. Vaccines were continuously contacted with intervals ranging from one hour to one day. Vaccines at 94.4% of the distribution points were completely consumed within two weeks. The mean consumption rate was 95.2 ± 1.93% during the overall study period. These findings suggest that the oral rabies vaccine attracts wildlife including domestic dogs and feral cats. Our results suggest that low sections of mountainous areas with bushy vegetation and/or neighboring riparian areas are rich in target wildlife species (especially raccoon dogs) and are efficient locations for vaccine distribution to control rabies in South Korea.

Phylogeny of Hungarian EBLV-1 strains using whole-genome sequence data

European bat lyssavirus 1 (EBLV-1) is a widespread lyssavirus across Europe, whose epizootic cycle is linked to a few bat species. Occasionally, EBLV-1 infection may occur in domestic animals and humans. EBLV-1 can be classified into two subtypes, where subtype EBLV-1a shows a wide geographic distribution between France and Russia whereas subtype EBLV-1b is distributed between Spain and Poland. In this study, we determined the genome sequence of two recent EBLV-1a strains detected in Hungary and analysed their adaptive evolution and phylodynamics. The data set that included 100 EBLV-1 genome sequences identified positive selection at selected sites in genes coding for viral proteins (N, codon 18; P, 141 and 155; G, 244 and 488; L, 168, 980, 1597 and 1754). A major genetic clade containing EBLV-1a isolates from Hungary, Slovakia, Denmark and Poland was estimated to have diverged during the 19th century whereas the divergence of the most recent ancestor of Hungarian and Slovakian isolates dates back to 1950 (time span, 1930 to 1970). Phylogeographic analysis of the EBLV-1a genomic sequences demonstrated strong evidence of viral dispersal from Poland to Hungary. This new information indicates that additional migratory flyways may help the virus spread, a finding that supplements the general theory on a west-to-east dispersal of EBLV-1a strains. Long-distance migrant bats may mediate the dispersal of EBLV-1 strains across Europe; however, structured surveillance and extended genome sequencing would be needed to better understand the epizootiology of EBLV-1 infections in Europe.

Molecular study of rabies virus in slaughtered dogs in Billiri and Kaltungo local government areas of Gombe state, Nigeria

Rabies is one of the most dreadful diseases and a major viral zoonosis which has been shown to cause an almost 100% fatality rate in infected victims. It is characterized by acute progressive encephalitis in mammals. This study determined the genotypic characteristics of rabies virus in dogs slaughtered for human consumption based on sequence of a fragment of nucleoprotein gene. Brain tissues were collected from 50 dogs slaughtered in Billiri and Kaltungo Local Government Areas of Gombe State, Nigeria. Direct fluorescent antibody test (DFAT) was used to screen for the presence of rabies virus antigen. Viral RNA isolated from DFAT positive brain tissues were subjected to the reverse transcription polymerase chain reaction (RT-PCR) followed by sequencing of the amplicons. Maximum Likelihood (ML) was used to construct a phylogenetic tree for sequences obtained with 1000 bootstrap replicates. The DFAT detected rabies antigen in 3 (6%) of the 50 dog brain tissues, from which 1 (2%) was positive by RT-PCR. ML phylogeny approach of the nucleotide sequences inferred members as originating lyssavirus genus and dog species. Essentially, MK234794 in this study displayed 99.3% sequence similarity with other related rabies viruses in the Africa 2 cluster (Nigeria, Cameroon, Chad and Niger). Interestingly, MK234794 showed no cluster relation with the Africa 1a, 1b, 3 and Africa 4 clades, respectively. This indicates there is in-country and trans-boundary circulation of the rabies viruses with no co-circulation between the Africa lineages, especially as dogs are continuously being traded due to consumption of dog meat in West Africa. This finding has given additional insight into the molecular epidemiology of rabies virus in Nigeria, therefore providing more baseline information for future design of rabies control programs in the country.

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.

Amino Acid Mutation in Position 349 of Glycoprotein Affect the Pathogenicity of Rabies Virus

Rabies, caused by rabies virus (RABV), is a zoonotic disease infecting mammals including humans. Studies have confirmed that glycoprotein (G) is most related to RABV pathogenicity. In the present study, to discover more amino acid sites related to viral pathogenicity, artificial mutants have been constructed in G of virulent strain GD-SH-01 backbone. Results showed that pathogenicity of GD-SH-01 significantly decreased when Gly₃₄₉ was replaced by Glu₃₄₉ through in vivo assays. Gly₃₄₉→Glu₃₄₉ of G did not significantly influence viral growth and spread in NA cells. Gly₃₄₉→Glu₃₄₉ of G increased the immunogenicity of GD-SH-01 in periphery and induced more expression of interferon alpha (IFN-α) in the brain in mice. It was observed that Gly₃₄₉→Glu₃₄₉ of G led to enhanced blood–brain barrier (BBB) permeability at day 5 postinfection. All together, these data revealed that Gly₃₄₉→Glu₃₄₉ of G mutation decreased RABV pathogenicity through enhanced immune response and increased BBB permeability. This study provides a new referenced site G349 that could attenuate pathogenicity of RABV.

Rabies in the African Civet: An Incidental Host for Lyssaviruses?

In South Africa, canid rabies virus (RABV) infection is maintained in domestic and wildlife species. The identification of rabies in African civets raised the question of whether this wildlife carnivore is a potential reservoir host of RABVs of direct and ancestral dog origin (dog-maintained and dog-derived origins) with an independent cycle of transmission. Genetic analyses of African civet nucleoprotein sequences for 23 African civet RABVs and historically published sequences demonstrated that RABVs from African civets have two origins related to dog and mongoose rabies enzootics. The data support observations of the interaction of civets with domestic dogs and wildlife mongooses, mostly in Northern South Africa and North-East Zimbabwe. Within each host species clade, African civet RABVs group exclusively together, implying intra-species virus transfer occurs readily. The canid RABV clade appears to support virus transfer more readily between hosts than mongoose RABVs. Furthermore, these data probably indicate short transmission chains with conspecifics that may be related to transient rabies maintenance in African civets. Hence, it is important to continue monitoring the emergence of lyssaviruses in this host. Observations from this study are supported by ongoing and independent similar cases, in which bat-eared foxes and black-backed jackal species maintain independent rabies cycles of what were once dog-maintained RABVs.

AAV-expressed G protein induces robust humoral and cellular immune response and provides durable protection from rabies virus challenges in mice

Rabies is a highly lethal infectious zoonosis caused by rabies virus (RABV), and the mortality rate is almost 100 % once clinical symptoms appear, which poses a huge threat to public health security across the many parts of the word. Vaccination is reported to be the most effective approach to prevent the disease. G protein is the only protein present on the surface of RABV, it also could induce humoral immunity to produce virus neutralizing antibodies (VNA) and stimulate T cells to produce cellular immunity. Adeno-associated viruses (AAVs) have been used as vectors for gene therapy of different human diseases for its low immunogenicity, high safety and long-term stable expression. To develop a safe and effective vaccine, recombinant AAVs containing different kind of G gene were constructed. After intramuscular (i.m.) immunization in mice, all of these rAAV-G vaccines could induce the production of high levels of VNA and effective cellular immune response. Consistently, all of the rAAV-G vaccines could provide protection against lethal RABV challenge. Our results shown that the rAAV-G vaccines could be potential candidates used in the control of RABV infection. In addition, rAAV-G as a vaccine has many advantages of low preparation cost, simple storage and transportation conditions (4 °C storage and transportation), simple immunization program (only one immunization) and so on. Thence, the rAAV-G vaccines could be potential candidates used in the control of RABV infection.

Highly efficient production of rabies virus glycoprotein G ectodomain in Sf9 insect cells

In the present study, we developed a complete process to produce in insect cells a high amount of the ectodomain of rabies virus glycoprotein G (G_E) as suitable antigen for detecting anti-rabies antibodies. Using the baculovirus expression vector system in Sf9 insect cells combined with a novel chimeric promoter (polh-pSeL), the expression level reached a yield of 4.1 ± 0.3 mg/L culture, which was significantly higher than that achieved with the standard polh promoter alone. The protein was recovered from the cell lysates and easily purified in only one step by metal ion affinity chromatography, with a yield of 95% and a purity of 87%. Finally, G_E was successfully used in an assay to detect specific antibodies in serum samples derived from rabies-vaccinated animals. The efficient strategy developed in this work is an interesting method to produce high amounts of this glycoprotein.

Feline herpesvirus vectored-rabies vaccine in cats: A dual protection

In China, cats cause about 5% of human rabies cases. Rabies control in cats plays a role in achieving the ultimate goal of elimination of dog rabies-mediated human deaths. However, there is no cat-specific rabies vaccine in China yet. In this study, we constructed a recombinant rabies vaccine by using a felid herpesvirus 1 (FHV-1) isolate, and deleted the gI/E in the FHV-1 and replaced the region with a glycoprotein (G) of rabies virus (RABV) strain BD06 through homologous recombination. The recombinant virus FHV-RVG was recovered and purified, and the expression of RABV glycoprotein was verified by indirect immunofluorescent assay. For potency in cats, each animal was inoculated intranasally with 1 ml FHV-RVG at 10^6.5 TCID₅₀. Blood samples were collected at defined intervals for antibody titration. The animals were challenged by herpes and rabies after completion of vaccination on day 180 and day 194, respectively. Our results demonstrated all vaccinated cats generated antibodies against both FHV-1 and RABV, and reached an arbitrary protective titer > 0.5 IU/ml for rabies viral neutralizing antibody (VNA) by day 14 post inoculation (dpi) and titer peaked on 30 dpi with VNA at 24.5 ± 10.23 IU/ml. All vaccinated cats presented no clinical signs of FHV-1 infection and survived rabies challenge, while the control cats had severe rhinotracheitis and died from rabies after challenge. All this demonstrated that the FHV-based recombinant vaccine is effective in protection against both FHV-1 and RABV infections.

Addicted to sugar: roles of glycans in the order Mononegavirales

Glycosylation is a biologically important protein modification process by which a carbohydrate chain is enzymatically added to a protein at a specific amino acid residue. This process plays roles in many cellular functions, including intracellular trafficking, cell-cell signaling, protein folding and receptor binding. While glycosylation is a common host cell process, it is utilized by many pathogens as well. Protein glycosylation is widely employed by viruses for both host invasion and evasion of host immune responses. Thus better understanding of viral glycosylation functions has potential applications for improved antiviral therapeutic and vaccine development. Here, we summarize our current knowledge on the broad biological functions of glycans for the Mononegavirales, an order of enveloped negative-sense single-stranded RNA viruses of high medical importance that includes Ebola, rabies, measles and Nipah viruses. We discuss glycobiological findings by genera in alphabetical order within each of eight Mononegavirales families, namely, the bornaviruses, filoviruses, mymonaviruses, nyamiviruses, paramyxoviruses, pneumoviruses, rhabdoviruses and sunviruses.

Analysis of expression profiles of long noncoding RNAs and mRNAs in brains of mice infected by rabies virus by RNA sequencing

Rabies, caused by rabies virus (RABV), is still the deadliest infectious disease. Mechanism of host immune response upon RABV infection is not yet fully understood. Accumulating evidences suggest that long noncoding RNAs (lncRNAs) plays key roles in host antiviral responses. However, expression profile and function of lncRNAs in RABV infection remain unclear. In the present study, expression profile of lncRNAs and mRNAs profiles were investigated in RABV-infected brain tissues of mice by RNA sequencing. A total of 140 lncRNAs and 3,807 mRNAs were differentially expressed in RABV-infected animals. The functional annotation and enrichment analysis using Gene Oncology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that differentially expressed transcripts were predominantly involved in signaling pathways related to host immune response. The expression profiles of the selected lncRNAs in brains of mice during RABV infections were verified by quantitative real time polymerase chain reaction (qRT-PCR). To our knowledge, this is the first report to profile the lncRNA expression in RABV infected mice. Our findings provide insights into understanding the role of lncRNAs in host immune response against RABV infection.

Molecular epidemiology of rabies virus circulating in domestic animals in India

Rabies is a neglected viral zoonotic disease affecting humans, domestic and wild animals and is endemic in most parts of the India. Dog mediated rabies is more predominant than other forms of rabies and molecular epidemiology is poorly understood in both reservoir and susceptible hosts. In the present study, a total of 140 rabies suspected brain samples from different species of animals from different geographical regions of India were used. The samples were parallelly tested by direct fluorescent antibody test, reverse transcriptase PCR and real-time PCR. Thirty positive samples were subjected for partial nucleoprotein gene sequencing and phylogenetic analysis. On sequence and phylogenetic analysis, it was observed that all Indian rabies viruses belonged to classical rabies virus of genotype 1 of Lyssavirus and formed two distinct groups. The majority of isolates were in group-1 and are closely related to arctic/arctic like lineage, whereas group-II isolated are closely related to cosmopolitan lineage. These results indicated there is simultaneous existence of two distinct lineages of rabies viruses in Indian subcontinent. Further whole genome studies are needed for better understanding of molecular epidemiology of rabies virus circulating in animals for control and prevention of rabies in India.

Rabies viruses leader RNA interacts with host Hsc70 and inhibits virus replication

Viruses have been shown to be equipped with regulatory RNAs to evade host defense system. It has long been known that rabies virus (RABV) transcribes a small regulatory RNA, leader RNA (leRNA), which mediates the transition from viral RNA transcription to replication. However, the detailed molecular mechanism remains enigmatic. In the present study, we determined the genetic architecture of RABV leRNA and demonstrated its inhibitory effect on replication of wild-type rabies, DRV-AH08. The RNA immunoprecipitation results suggest that leRNA inhibits RABV replication via interfering the binding of RABV nucleoprotein with genomic RNA. Furthermore, we identified heat shock cognate 70 kDa protein (Hsc70) as a leRNA host cellular interacting protein, of which the expression level was dynamically regulated by RABV infection. Notably, our data suggest that Hsc70 was involved in suppressing RABV replication by leader RNA. Finally, our experiments imply that leRNA might be potentially useful as a novel drug in rabies post-exposure prophylaxis. Together, this study suggested leRNA in concert with its host interacting protein Hsc70, dynamically down-regulate RABV replication.

Sequencing and sequence analysis of partial nucleoprotein (N) gene and phylogenetic analysis of rabies virus field isolates from Gujarat state, India

The present study was undertaken with an aim of characterization of rabies virus (genus Lyssavirus of the family Rhabdoviridae under the order Mononegavirales) by sequencing of partial nucleoprotein (N) gene of rabies virus and phylogenetic analysis to know the genotype and lineage of rabies virus present in Gujarat state of India. A total of 32 samples (18 brain samples and 14 saliva samples) were aseptically collected from live and dead animals (viz. dog, buffalo, cow, goat, donkey and hyena) for rabies virus detection. Out of 32 samples, 24 samples were found positive by Reverse Transcriptase Polymerase Chain Reactions and from these 24 positive samples, 20 samples were selected for sequencing having good concentration of gene product. ClustalW alignment of nucleotide sequences and amino acid sequences of field rabies isolates revealed 95.20-100 and 97.95-100% similarity among themselves, respectively. Multiple sequence alignment of field rabies isolates and reference vaccine strains [Pasteur strain and Challenge Virus Strain (CVS)] indicated single nucleotide mutations at total 91 positions and amino acid mutations at total 17 different positions. Phylogenetic analysis of N gene sequences using our 20 field rabies isolates and 21 other reported isolates in Genbank resulted in 3 phylogenetic clusters. All the field rabies isolates showed same genetic lineage among themselves and with other earlier reported Indian rabies isolates placing them in Arctic like lineage of Genotype 1 Rabies virus. However, they were at genetic distance with reference Pasteur and CVS strains, which grouped in different phylogenetic cluster.

Molecular characterization and phylogenetic relatedness of dog-derived Rabies Viruses circulating in Cameroon between 2010 and 2016

Rabies is enzootic among dog populations in some parts of Cameroon and the risk of human rabies is thought to be steadily high in these regions. However, the molecular epidemiology of circulating Rabies Virus (RABV) has been hardly considered in Cameroon as well as in most neighboring central African countries. To address this fundamental gap, 76 nucleoprotein (N) gene sequences of dog-derived RABV were obtained from 100 brain specimens sampled in Cameroon from 2010 to 2016. Studied sequences were subjected to molecular and phylogenetic analyses with reference strains retrieved from databases. The 71 studied Africa-1 isolates displayed 93.5–100% nucleotide (nt) and 98.3–100% amino-acid (aa) identities to each other while, the 5 studied Africa-2 isolates shared 99.4–99.7% sequence similarities at nt and aa levels. Maximum Likelihood based phylogenies inferred from nucleotide sequences confirmed all studied RABV isolates as members of the dog-related species 1 of the Lyssavirus genus. Individual isolates could be unambiguously assigned as either the Africa-1 subclade of the Cosmopolitan clade or the Africa 2 clade. The Africa-1 subclade appeared to be more prevalent and diversified. Indeed, 70 studied isolates segregated into 3 distinct circulating variants within Africa-1a lineage while a unique isolate was strikingly related to the Africa-1b lineage known to be prevalent in the neighboring Central African Republic and eastern Africa. Interestingly, all five Africa-2 isolates fell into the group-E lineage even though they appeared to be loosely related to databases available reference RABV; including those previously documented in Cameroon. This study uncovered the co-circulation of several Africa-1 and Africa-2 lineages in the southern regions of Cameroon. Striking phylogenetic outcasts to the geographic differentiation of RABV variants indicated that importation from close regions or neighboring countries apparently contributes to the sustainment of the enzootic cycle of domestic rabies in Cameroon.

Rabies has been repeatedly reported among dog populations in Cameroon, especially in Yaounde, its capital city. However, the relative rates and genetic variability of Rabies Virus (RABV) variants circulating among dog populations in Cameroon are still to be documented. This study aimed to estimate the frequency and genetic diversity of RABV isolates originating from rabid dogs in the southern regions of Cameroon from 2010 to 2016. Overall, 76 of the 100 dog-derived RABV isolates sampled in Cameroon from 2010 to 2016 were successfully characterized. Our findings revealed that studied isolates belonged to the dog-related species 1 of the Lyssavirus genus, specifically 70 Africa-1a, 1 Africa-1b and 5 Africa-2 group-E lineages. The general phylogenetic pattern suggested an in-country geographic differentiation of the circulating RABV variants. This apparent geographic differentiation was contradicted by striking outcasts indicating importation from close or distant regions. Overall, this study uncovered the co-circulation of several Africa-1 and Africa-2 lineages in some southern regions of Cameroon, thus providing base-line molecular data that would be of interest for future stages of implementation of the rabies surveillance and control plan that is being setup in Cameroon.

A time-resolved fluoroimmunoassay to assay the rabies virus glycoprotein: application for estimation of human rabies vaccine potency

Replacement of the in vivo rabies vaccine potency test (NIH test) by in vitro methods had been discussed by several researcher including WHO expert working groups. In this paper, a time-resolved fluoroimmunoassay (TRFIA) for the assay of rabies virus glycoprotein in rabies vaccine was first established to estimate the rabies vaccine potency by using specific monoclonal antibody that only recognized the native, trimeric and immunogenic form of rabies virus glycoprotein. Potency of the rabies virus glycoprotein was assayed with satisfactory performance under optimal conditions, and the method demonstrated satisfactory results when applied in practical samples. The correlation coefficient of potency values obtained from the present TRFIA and ELISA was 0.912, and 0.903 for those from the present TRFIA and NIH test. These preliminary results confirmed that this TRFIA can replace ELISA with higher performance, and could be a promising replacement of the NIH test. Based upon these results, the present TRFIA seemed to be a convenient tool for evaluating rabies vaccine potency and its products at different stages accordingly.

Mass vaccination has led to the elimination of rabies since 2014 in South Korea

PURPOSE

Rabies is one of the most fatal diseases, but it is 100% preventable in animals by vaccination. In this study, we present the epidemiological features of, and national preventive measures against, rabies in Korea.

MATERIALS AND METHODS

Data related to rabies and the population density of raccoon dogs in Korea were collected from the Animal and Plant Quarantine Agency, the Korean Centers for Disease Control and Prevention, and the National Institute of Environmental Research. Rabies diagnosis was confirmed with a fluorescent antibody test using brain samples of animals in accordance with the procedures described by the World Organization for Animal Health. Serological assays for dogs and cattle were conducted using the fluorescent antibody virus neutralization test.

RESULTS

From 1993 to 2016, a total of seven human rabies cases and 437 animal rabies cases in five different species were reported. An increase in the distribution of bait vaccine seemed to be related to a dramatic decrease in rabies prevalence in endemic rabies regions. Two Korean provinces and the capital city, Seoul, were involved in rabies outbreaks. Korean rabies strains are most closely related to the eastern Chinese strain belonging to the Arctic-like lineage. The yearly seropositive rates ranged from 50.4% to 81.2% in dogs and from 25% to 60.5% in cattle residing in endemic rabies regions.

CONCLUSION

This study indicates that national preventive measures, including mass vaccination and distribution of bait vaccines, have contributed to a substantial decrease in the number of rabies cases in Korea.

Critical Role of K1685 and K1829 in the Large Protein of Rabies Virus in Viral Pathogenicity and Immune Evasion

Rabies, one of the oldest infectious diseases, still presents a public health threat in most parts of the world today. Its pathogen, rabies virus (RABV), can utilize its viral proteins, such as the nucleoprotein and phosphorylation protein, to subvert the host innate immune system. For a long time, the large (L) protein was believed to be essential for RABV transcription and replication, but its role in viral pathogenicity and immune evasion was not known. Recent studies have found that the conserved K-D-K-E tetrad motif in the L protein is related to the methyltransferase (MTase) activity in the viral mRNA process. In the present study, a series of RABV mutations in this motif was constructed with the recombinant CVS-B2c (rB2c) virus. Two of these mutants, rB2c-K1685A and rB2c-K1829A, were found to be stable and displayed an attenuated phenotype in both in vitro growth and in vivo pathogenicity in adult and suckling mice. Further studies demonstrated that these two mutants were more sensitive to the expression of the interferon-stimulated gene product IFIT2 than the parent virus. Taken together, our results suggest that K1685 and K1829 in the L protein play important roles in pathogenicity and immune evasion during RABV infection.

IMPORTANCE

Rabies continues to present a public health threat in most areas of the world, especially in the developing countries of Asia and Africa. The pathogenic mechanisms for rabies are not well understood. In the present study, it was found that the recombinant rabies viruses rB2c-K1685A and rB2c-K1829A, carrying mutations at the predicted MTase catalytic sites in the L protein, were highly attenuated both in vitro and in vivo. Further studies showed that these mutants were more sensitive to the expression of the interferon-stimulated gene product IFIT2 than the parent virus. These findings improve our understanding of rabies pathogenesis, which may help in developing potential therapeutics and an avirulent rabies vaccine.

The inability of wild-type rabies virus to activate dendritic cells is dependent on the glycoprotein and correlates with its low level of the de novo-synthesized leader RNA

Dendritic cells (DCs) are the most efficient antigen-presenting cells, playing a key role in the adaptive immune responses to viral infections. Our studies demonstrate that wild-type (wt) rabies virus (RABV) does not activate DCs. Adoptive transfer of DCs primed with wt RABV did not activate DCs, stimulate virus neutralizing antibodies (VNA), or protect recipients against challenge. However, adoptive transfer of DCs primed with laboratory-attenuated RABV resulted in DC activation, production of VNA, and protection against challenge. In vitro studies with recombinant RABV (laboratory-attenuated RABV expressing the glycoprotein or the phosphoprotein from wt RABV) demonstrate that DC activation is dependent on the glycoprotein and involves the IPS-1 pathway. Furthermore, binding to and entry into DCs by wt RABV is severely blocked, and the copy number of de novo-synthesized leader RNA was two logs lower in DCs infected with the wt than in DCs treated with laboratory-attenuated RABV. However, transient transfection of DCs with synthesized leader RNA from either wt or attenuated RABV is capable of activating DCs in a dose-dependent manner. Thus, the inability of wt RABV to activate DCs correlates with its low level of the de novo-synthesized leader RNA.

IMPORTANCE

Rabies remains a public health threat, with more than 55,000 fatalities each year around the world. Since DCs play a key role in the adaptive immune responses to viral infections, we investigated the ability of rabies virus (RABV) to activate DCs. It was found that the adoptive transfer of DCs primed with wt RABV did not activate DCs, stimulate VNA, or protect mice against lethal challenge. However, laboratory-attenuated RABV mediates the activation of DCs via the IPS-1 pathway and is glycoprotein dependent. We further show that wt RABV evades DC-mediated immune activation by inefficient binding/entry into DCs and as a result of a reduced level of de novo-synthesized leader RNA. These findings may have important implications in the development of efficient rabies vaccines.

Rabies vaccines: where do we stand, where are we heading?

Rabies being the most lethal zoonotic, vaccine-preventable viral disease with worldwide distribution of reservoir wild animals presents unique challenges for its diagnosis, management and control. Although vaccines available are highly effective, which had played the key role in controlling rabies in North America, western Europe and in a number of Asian and Latin American countries, the requirement of multiple doses along with boosters, associated cost to reduce the incidence in wild animals and prophylactic human vaccination has remained a major impediment towards achieving the same goals in poorer parts of the world such as sub-Saharan Africa and southeast Asia. Current efforts to contain rabies worldwide are directed towards the development of more safe, cheaper and efficacious vaccines along with anti-rabies antibodies for post-exposure prophylaxis. The work presented here provides an overview of the advances made towards controlling the human rabies, particularly in last 10 years, and future perspective.

The phylogeography of rabies in Grenada, West Indies, and implications for control

In Grenada, West Indies, rabies is endemic, and is thought to be maintained in a wildlife host, the small Indian mongoose (Herpestes auropunctatus) with occasional spillover into other hosts. Therefore, the present study was undertaken to improve understanding of rabies epidemiology in Grenada and to inform rabies control policy. Mongooses were trapped island-wide between April 2011 and March 2013 and examined for the presence of Rabies virus (RABV) antigen using the direct fluorescent antibody test (dFAT) and PCR, and for serum neutralizing antibodies (SNA) using the fluorescent antibody virus neutralization test (FAVN). An additional cohort of brain samples from clinical rabies suspects submitted between April 2011 and March 2014 were also investigated for the presence of virus. Two of the 171 (1.7%) live-trapped mongooses were RABV positive by FAT and PCR, and 20 (11.7%) had SNAs. Rabies was diagnosed in 31 of the submitted animals with suspicious clinical signs: 16 mongooses, 12 dogs, 2 cats and 1 goat. Our investigation has revealed that rabies infection spread from the northeast to the southwest of Grenada within the study period. Phylogenetic analysis revealed that the viruses from Grenada formed a monophyletic clade within the cosmopolitan lineage with a common ancestor predicted to have occurred recently (6-23 years ago), and are distinct from those found in Cuba and Puerto Rico, where mongoose rabies is also endemic. These data suggest that it is likely that this specific strain of RABV was imported from European regions rather than the Americas. These data contribute essential information for any potential rabies control program in Grenada and demonstrate the importance of a sound evidence base for planning interventions.

Rabies virus isolates of India - simultaneous existence of two distinct evolutionary lineages

Rabies is a fatal viral disease of serious public health implication. The disease is enzootic in India. In the present study, thirty six rabies virus isolates were obtained from terrestrial mammals of India during 2002-2012. Ecto-domain coding region of the glycoprotein gene from all the isolates were sequenced and the phylogenetic analysis was performed in relation to the global rabies and rabies related virus isolates. The Indian isolates grouped into two distinctly separate lineages with majority of the Indian isolates in Arctic like 1 lineage and the remaining isolates in sub-continental lineage. Isolates of the two distinct lineages were identified simultaneously from the same geographical region. Time scaled phylogenetic tree indicated that the sub-continental lineage of the virus is one of the earliest clade of rabies virus that diverged from bat rabies virus. On the contrary, the Arctic-like 1 lineage of India appeared to be a more recent divergence event. The amino acid sequence comparison revealed that all the major antigenic sites were almost conserved among the Indian isolates whereas few amino acid variations could be identified around site IIa, minor site I and IV. The dN/dS study based on G ecto-domain is in support of the earlier reports of strong purifying selection. In conclusion, it is evident that the Indian rabies virus isolates are of two major distinct lineages with distant phylogenetic and evolutionary relationship.

Reemergence of rabies in the southern Han river region, Korea

Recently, 11 cases of animal rabies were reported in the southern region (Suwon and Hwaseong cities) of Gyeonggi Province, South Korea. The cases were temporally separated into two cases in dogs (Canis lupus familiaris) in spring 2012 and nine cases in domestic animals and wildlife in winter 2012-13. All carcasses were submitted for histopathologic examination and viral antigen identification. Sequences of the glycoprotein, nucleoprotein, and glycoprotein-large polymerase protein intergenic noncoding loci of the 11 strains were determined and compared with published reference sequences. All rabies strains were closely related to the Gangwon strains isolated in 2008-09, suggesting that the rabies virus strains isolated in Gyeonggi were introduced from Gangwon Province.

Enzootic and epizootic rabies associated with vampire bats, peru

During the past decade, incidence of human infection with rabies virus (RABV) spread by the common vampire bat (Desmodus rotundus) increased considerably in South America, especially in remote areas of the Amazon rainforest, where these bats commonly feed on humans. To better understand the epizootiology of rabies associated with vampire bats, we used complete sequences of the nucleoprotein gene to infer phylogenetic relationships among 157 RABV isolates collected from humans, domestic animals, and wildlife, including bats, in Peru during 2002-2007. This analysis revealed distinct geographic structuring that indicates that RABVs spread gradually and involve different vampire bat subpopulations with different transmission cycles. Three putative new RABV lineages were found in 3 non-vampire bat species that may represent new virus reservoirs. Detection of novel RABV variants and accurate identification of reservoir hosts are critically important for the prevention and control of potential virus transmission, especially to humans.

Enzootic and epizootic rabies associated with vampire bats, peru

During the past decade, incidence of human infection with rabies virus (RABV) spread by the common vampire bat (Desmodus rotundus) increased considerably in South America, especially in remote areas of the Amazon rainforest, where these bats commonly feed on humans. To better understand the epizootiology of rabies associated with vampire bats, we used complete sequences of the nucleoprotein gene to infer phylogenetic relationships among 157 RABV isolates collected from humans, domestic animals, and wildlife, including bats, in Peru during 2002-2007. This analysis revealed distinct geographic structuring that indicates that RABVs spread gradually and involve different vampire bat subpopulations with different transmission cycles. Three putative new RABV lineages were found in 3 non-vampire bat species that may represent new virus reservoirs. Detection of novel RABV variants and accurate identification of reservoir hosts are critically important for the prevention and control of potential virus transmission, especially to humans.

Negative effects of a disulfide bond mismatch in anti-rabies G protein single-chain antibody variable fragment FV57

Rabies virus (RV) causes a fatal infectious disease requiring efficient post-exposure prophylaxis (PEP), which includes a rabies vaccine and rabies immunoglobulin (RIG). The single-chain antibody variable fragment (scFv), a small engineered antibody fragment derived from an antibody variable heavy chain and light chain, has the potential to replace the current application of RIG. In previous studies, we constructed and evaluated an anti-rabies virus G protein scFv (FV57) based on the monoclonal antibody CR57. Of the five cysteines in FV57, four are linked in intra-chain disulfide bonds (Cys-VH28/Cys-VH98 and Cys-VL16/Cys-VL84), and one is free (Cys-VL85). However, the thiol in Cys-VL85 neighboring Cys-VL84 in the CDR3 of the light chain is likely to mismatch with the thiol in Cys-VL16 during the renaturing process. In order to study effects of the mismatched disulfide bond, Cys-VL85 and Cys-VL84 of FV57 were mutated to serine to construct mutants FV57(VL85S) and FV57(VL84S). Furthermore, the disulfide bonds in the light chain of FV57, FV57(VL85S) and FV57(VL84S) were deleted by mutating Cys-VL16 to serine. All mutants were prepared and evaluated along with the original FV57. The results indicated that the mismatched disulfide bond of FV57 linking the light chain FR1 and CDR3 would confer deleterious negative effects on its activity against RV, likely due to spatial hindrance in the light chain CDR3. Moreover, avoidance of the disulfide bond mismatch provided an additional 30% protective efficacy against RV infection in the mouse RV challenge model. Thus, modifications of FV57 to eliminate the disulfide bond mismatch may provide a candidate therapeutic agent for effective PEP against rabies.

Comparison of complete genome sequences of dog rabies viruses isolated from China and Mexico reveals key amino acid changes that may be associated with virus replication and virulence

Rabies is a global problem, but its impact and prevalence vary across different regions. In some areas, such as parts of Africa and Asia, the virus is prevalent in the domestic dog population, leading to epidemic waves and large numbers of human fatalities. In other regions, such as the Americas, the virus predominates in wildlife and bat populations, with sporadic spillover into domestic animals. In this work, we attempted to investigate whether these distinct environments led to selective pressures that result in measurable changes within the genome at the amino acid level. To this end, we collected and sequenced the full genome of two isolates from divergent environments. The first isolate (DRV-AH08) was from China, where the virus is present in the dog population and the country is experiencing a serious epidemic. The second isolate (DRV-Mexico) was taken from Mexico, where the virus is present in both wildlife and domestic dog populations, but at low levels as a consequence of an effective vaccination program. We then combined and compared these with other full genome sequences to identify distinct amino acid changes that might be associated with environment. Phylogenetic analysis identified strain DRV-AH08 as belonging to the China-I lineage, which has emerged to become the dominant lineage in the current epidemic. The Mexico strain was placed in the D11 Mexico lineage, associated with the West USA-Mexico border clade. Amino acid sequence analysis identified only 17 amino acid differences in the N, G and L proteins. These differences may be associated with virus replication and virulence-for example, the short incubation period observed in the current epidemic in China.

Molecular Epidemiology of Rabies in Vietnam

The present study was done to determine the molecular epidemiology of rabies virus (RV) in Vietnam. The nucleoprotein (N) and glycoprotein (G) genes of RVs were amplified from the brains of ten rabid dogs of Ho Chi Minh City, Vietnam. The nucleotide sequences of these genes were compared with those of other Asian strains to find the possible relationship among them. Phylogenetic analysis revealed that the Asian N gene segregated into three main branches, namely South-East Asia 1 (SEA 1), South-East Asia 2 (SEA 2) and Indian subcontinent (ISC) genotypes. The SEA 1 genotype comprised RVs from Malaysia, Vietnam and Thailand. The SEA 2 genotype contained strains from the Philippines, and the ISC genotype comprised strains from Sri Lanka and India. Phylogenetically G genes of RVs from Vietnam and Thailand were clustered together. Our study suggests that Vietnamese and Thai RVs are closely related and might have originated from a common ancestor.

Characterization of a Slow-Migrating Component of the Rabies Virus Matrix Protein Strongly Associated with the Viral Glycoprotein

We investigated multiple forms of rabies virus matrix (M) protein. Under non-reducing electrophoretic conditions, we detected, in addition to major bands of monomer forms (23- and 24-kDa) of M protein, an M antigen-positive slow-migrating minor band (about 54 kDa) in both the virion and infected cells. Relative contents of the 54-kDa and monomer components in the virion were about 20-30% and 70-80% of the whole M protein, respectively, while the content of the 54-kDa component was smaller (about 10-20% of the total M protein) in the cell than in the virion. The 54-kDa components could be extracted from the infected cells with sodium deoxycholate, but they were quite resistant to extraction with 1% nonionic detergents by which most monomer components were solubilized. The 54-kDa component was precipitated more efficiently than the monomer by a monoclonal antibody (mAb; #3-9-16), which recognized a linear epitope located at the N-terminal of the M protein. The mAb #3-9-16 coprecipitated the viral glycoprotein (G), which was demonstrated to be due to strong association between the G and 54-kDa component of the M protein. Monomers and the 54-kDa polypeptide migrated to the same isoelectric point (pI) in twodimensional (2-D) gel electrophoresis, implicating that the 54-kDa component was composed of component(s) of the same pI as that of the M protein monomers. From these results, we conclude that the M antigen-positive 54-kDa polypeptide is a homodimer of M protein, taking an N-terminal-exposed conformation, and is strongly associated with the viral glycoprotein. Possible association with a membrane microdomain of the cell will be discussed.

Monoclonal Antibody #3-9-16 Recognizes One of the Two Isoforms of Rabies Virus Matrix Protein That Exposes Its N-Terminus on the Virion Surface

We investigated behaviors of the rabies virus matrix (M) protein using a monoclonal antibody (mAb), #3-9-16, that recognized a linear epitope located at the N-terminus of the protein. Based on the reactivity with this mAb, M proteins could be divided into at least two isoforms; an ordinary major form (Malpha) whose 3-9-16 epitope is hidden, and an N-terminal-exposed epitope-positive form (Mbeta). The Mbeta protein accounted for about 25-30% of the total M proteins in the virion, while its content in the cell ranged from 10 to 15% of total M protein. Fluorescent antibody (FA) staining showed that the Mbeta antigen distributed in the Golgi area where the colocalized viral glycoprotein antigen was also detected. Mbeta antigen was shown to be exposed on the surface of infected cells by both immunoprecipitation and FA staining with the mAb, whereby the cells might have become sensitive to the mAb-dependent complement-mediated cytolysis. Similarly, the Mbeta antigen was shown to be exposed on the virion surface, and the infectivity of the virus was destroyed by the mAb in the presence of a complement. Together with these results, we think that the M protein molecule takes either of two conformations, one (Mbeta) of which exposes the 3-9-16 epitope located in the N-terminal region of the M protein, that are also exposed on the surface of the virion and infected cells, whereby it might play a certain important role(s) in the virus replication process differently from the other form (Malpha), probably through its intimate association with the Golgi area and/or the cell membrane.

Complete genome sequences of three rabies viruses isolated from rabid raccoon dogs and a cow in Korea

The complete genomes of three rabies viruses (BD0406CC, BV9901PJ, and 08F40) of two raccoon dogs (Nyctereutes procyonoides koreensis) and a cow were determined. The genomic organization is typical of rabies viruses, and the open reading frames of the N, P, M, G, and L genes are 1,353, 894, 609, 1,575, and 6,384 bases in length, respectively. The full genome length of the three strains was 11,928 nucleotides, and the sequence similarity between the rabies viruses at the nucleotide level was 98.5-99.5%. Sequence comparisons indicated that these rabies viruses belong to the "Arctic and Arctic-like" group, with high homology to the Eurasian cluster. All Korean strains were clustered with the Mongolia strains, which belong to Arctic-like 1 clade. The 08F40 and BD0406CC strains were constructed with rabies virus strains isolated in Gangwon province. The BV9901PJ strain was closely related to strains isolated in Gyeonggi province in Korea. Three strains were more dependent upon geographical distribution and time period than host species. Complete genome sequencing of different host-origin rabies viruses will provide information that should contribute to understanding the transmission cycle and genetic variability of rabies from different hosts.

In vivo differential susceptibility of sensory neurons to rabies virus infection

There is controversy with regard to the entry pathway of the rabies virus (RABV) into the central nervous system (CNS). Some authors have suggested that the virus inoculated at the periphery is captured and transported to CNS only by motor neurons; however, it has been reported that dorsal root ganglia (DRG) sensory neurons capture and transport the virus to the spinal cord (SC) and then to the brain. It is probable that preferences for one pathway or another depend on the site of inoculation and the post-infection time. Therefore, in the present study, we evaluated different vertebral segments and post-infection times, along with the location, number, and subpopulation of sensory neurons susceptible to infection after inoculating RABV in the footpads of adult mice. It was noted that the virus inoculated in the footpad preferentially entered the CNS through the large-sized DRG sensory neurons, while infection of the motor neurons occurred later. Further, it was found that the virus was dispersed in spinal cord trans-synaptically through the interneurons, arriving at both sensory neurons and contralateral motor neurons. In conclusion, we observed that RABV inoculated in the plantar footpad is captured preferentially by large sensory neurons and is transported to the DRG, where it replicates and is spread to the SC using transynaptic jumps, infecting sensory and motor neurons at the same level before ascending to the brain.