Rabies virus (RABV) maintenance in bats is not well understood. Big brown bats (Eptesicus fuscus), little brown bats (Myotis lucifugus), and Mexican free-tailed bats (Tadarida brasiliensis) are the most common bats species in the United States. These colonial bat species also have the most frequent contact with humans and domestic animals. However, the silver-haired bat (Lasionycteris noctivagans) RABV is associated with the majority of human rabies virus infections in the United States and Canada. This is of interest because silver-haired bats are more solitary bats with infrequent human interaction. Our goal was to determine the likelihood of a colonial bat species becoming infected with and transmitting a heterologous RABV. To ascertain the potential of heterologous RABV infection in colonial bat species, little brown bats were inoculated with a homologous RABV or one of two heterologous RABVs. Additionally, to determine if the route of exposure influenced the disease process, bats were inoculated either intramuscularly (i.m.) or subcutaneously (s.c.) with a homologous or heterologous RABV. Our results demonstrate that intramuscular inoculation results in a more rapid progression of disease onset, whereas the incubation time in bats inoculated s.c. is significantly longer. Additionally, cross protection was not consistently achieved in bats previously inoculated with a heterologous RABV following a challenge with a homologous RABV 6 months later. Finally, bats that developed rabies following s.c. inoculation were significantly more likely to shed virus in their saliva and demonstrated increased viral dissemination. In summary, bats inoculated via the s.c. route are more likely to shed virus, thus increasing the likelihood of transmission.
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.
rabies; molecular epidemiology; bats; Peru; viruses; zoonoses; vampire bats
Rabies is a fatal infection of the central nervous system primarily transmitted by rabid animal bites. Rabies virus (RABV) circulates through two different epidemiological cycles: terrestrial and aerial, where dogs, foxes or skunks and bats, respectively, act as the most relevant reservoirs and/or vectors. It is widely accepted that insectivorous bats are not important vectors of RABV in Argentina despite the great diversity of bat species and the extensive Argentinean territory.
We studied the positivity rate of RABV detection in different areas of the country, and the antigenic and genetic diversity of 99 rabies virus (RABV) strains obtained from 14 species of insectivorous bats collected in Argentina between 1991 and 2008.
Based on the analysis of bats received for RABV analysis by the National Rabies system of surveillance, the positivity rate of RABV in insectivorous bats ranged from 3.1 to 5.4%, depending on the geographic location. The findings were distributed among an extensive area of the Argentinean territory. The 99 strains of insectivorous bat-related sequences were divided into six distinct lineages associated with Tadarida brasiliensis, Myotis spp, Eptesicus spp, Histiotus montanus, Lasiurus blosseviilli and Lasiurus cinereus. Comparison with RABV sequences obtained from insectivorous bats of the Americas revealed co-circulation of similar genetic variants in several countries. Finally, inter-species transmission, mostly related with Lasiurus species, was demonstrated in 11.8% of the samples.
This study demonstrates the presence of several independent enzootics of rabies in insectivorous bats of Argentina. This information is relevant to identify potential areas at risk for human and animal infection.
In Argentina, successful vaccination and control of terrestrial rabies in the 1980s revealed the importance of the aerial route in RABV transmission. Current distribution of cases shows a predominance of rabies by hematophagous bats in the Northern regions where rabies is a major public health concern; in contrast, in Central and Southern regions where rabies is not a major public health concern, little surveillance is performed. Based on the analysis of insectivorous bats received for RABV analysis by the National Rabies system of surveillance, the positivity rate of RABV in insectivorous bats in these regions ranged from 3.1 to 5.4%. This rate is comparable to other nations such as the United States (9–10%) where insectivorous bats are an important cause of concern for RABV surveillance systems. Antigenic and genetic analysis of a wide collection of rabies strains shows the presence of multiple endemic cycles associated with six bat insectivorous species distributed among an extensive area of the Argentinean territory and several countries of the Americas. Finally, inter-species transmission, mostly related with Lasiurus species, was demonstrated in 11.8% of the samples. Increased public education about the relationship between insectivorous bats and rabies are essential to avoid human cases and potential spread to terrestrial mammals.
The study of rabies virus infection in bats can be challenging due to quarantine requirements, husbandry concerns, genetic differences among animals, and lack of medical history. To date, all rabies virus (RABV) studies in bats have been performed in wild caught animals. Determining the RABV exposure history of a wild caught bat based on the presence or absence of viral neutralizing antibodies (VNA) may be misleading. Previous studies have demonstrated that the presence of VNA following natural or experimental inoculation is often ephemeral. With this knowledge, it is difficult to determine if a seronegative, wild caught bat has been previously exposed to RABV. The influence of prior rabies exposure in healthy, wild caught bats is unknown. To investigate the pathogenesis of RABV infection in bats born in captivity (naïve bats), naïve bats were inoculated intramuscularly with one of two Eptesicus fuscus rabies virus variants, EfV1 or EfV2. To determine the host response to a heterologous RABV, a separate group of naïve bats were inoculated with a Lasionycteris noctivagans RABV (LnV1). Six months following the first inoculation, all bats were challenged with EfV2. Our results indicate that naïve bats may have some level of innate resistance to intramuscular RABV inoculation. Additionally, naïve bats inoculated with the LnV demonstrated the lowest clinical infection rate of all groups. However, primary inoculation with EfV1 or LnV did not appear to be protective against a challenge with the more pathogenic EfV2.
In nature, rabies virus (RABV; genus Lyssavirus, family Rhabdoviridae) represents an assemblage of phylogenetic lineages, associated with specific mammalian host species. Although it is generally accepted that RABV evolved originally in bats and further shifted to carnivores, mechanisms of such host shifts are poorly understood, and examples are rarely present in surveillance data. Outbreaks in carnivores caused by a RABV variant, associated with big brown bats, occurred repeatedly during 2001–2009 in the Flagstaff area of Arizona. After each outbreak, extensive control campaigns were undertaken, with no reports of further rabies cases in carnivores for the next several years. However, questions remained whether all outbreaks were caused by a single introduction and further perpetuation of bat RABV in carnivore populations, or each outbreak was caused by an independent introduction of a bat virus. Another question of concern was related to adaptive changes in the RABV genome associated with host shifts. To address these questions, we sequenced and analyzed 66 complete and 20 nearly complete RABV genomes, including those from the Flagstaff area and other similar outbreaks in carnivores, caused by bat RABVs, and representatives of the major RABV lineages circulating in North America and worldwide. Phylogenetic analysis demonstrated that each Flagstaff outbreak was caused by an independent introduction of bat RABV into populations of carnivores. Positive selection analysis confirmed the absence of post-shift changes in RABV genes. In contrast, convergent evolution analysis demonstrated several amino acids in the N, P, G and L proteins, which might be significant for pre-adaptation of bat viruses to cause effective infection in carnivores. The substitution S/T242 in the viral glycoprotein is of particular merit, as a similar substitution was suggested for pathogenicity of Nishigahara RABV strain. Roles of the amino acid changes, detected in our study, require additional investigations, using reverse genetics and other approaches.
Host shifts of the rabies virus (RABV) from bats to carnivores are important for our understanding of viral evolution and emergence, and have significant public health implications, particularly for the areas where “terrestrial” rabies has been eliminated. In this study we addressed several rabies outbreaks in carnivores that occurred in the Flagstaff area of Arizona during 2001–2009, and caused by the RABV variant associated with big brown bats (Eptesicus fuscus). Based on phylogenetic analysis we demonstrated that each outbreak resulted from a separate introduction of bat RABV into populations of carnivores. No post-shift changes in viral genomes were detected under the positive selection analysis. Trying to answer the question why certain bat RABV variants are capable for host shifts to carnivores and other variants are not, we developed a convergent evolution analysis, and implemented it for multiple RABV lineages circulating worldwide. This analysis identified several amino acids in RABV proteins which may facilitate host shifts from bats to carnivores. Precise roles of these amino acids require additional investigations, using reverse genetics and animal experimentation. In general, our approach and the results obtained can be used for prediction of host shifts and emergence of other zoonotic pathogens.
Rabies is a fatal zoonosis caused by a nonsegmented negative-strand RNA virus, namely, rabies virus (RABV). Apart from RABV, at least 10 additional species are known as rabies-related lyssaviruses (RRVs), and some of them are responsible for occasional spillovers into humans. More lyssaviruses have also been detected recently in different bat ecosystems, thanks to the application of molecular diagnostic methods. Due to the variety of the members of the genus Lyssavirus, there is the necessity to develop a reliable molecular assay for rabies diagnosis able to detect and differentiate among the existing rabies and rabies-related viruses. In the present study, a pyrosequencing protocol targeting the 3′ terminus of the nucleoprotein (N) gene was applied for the rapid characterization of lyssaviruses. Correct identification of species was achieved for each sample tested. Results from the pyrosequencing assay were also confirmed by those obtained using the Sanger sequencing method. A pan-lyssavirus one-step reverse transcription (RT)-PCR was developed within the framework of the pyrosequencing procedure. The sensitivity (Se) of the one-step RT-PCR assay was determined by using in vitro-transcribed RNA and serial dilutions of titrated viruses. The assay demonstrated high analytical and relative specificity (Sp) (98.94%) and sensitivity (99.71%). To date, this is the first case in which pyrosequencing has been applied for lyssavirus identification using a cheaper diagnostic approach than the one for all the other protocols for rapid typing that we are acquainted with. Results from this study indicate that this procedure is suitable for lyssavirus detection in samples of both human and animal origin.
The nucleoprotein (N) and glycoprotein (G) of 11 Korean rabies virus (RABV) isolates collected from animals diagnosed with rabies between 2008 and 2009 were subjected to molecular and phylogenetic analyses. Six isolates originated from domestic animals (cattle and dogs) and five were obtained from wild free-ranging raccoon dogs. The similarities in the nucleotide sequences of the N gene among all Korean isolates ranged from 98.1 to 99.8%, while those of the G gene ranged from 97.9 to 99.3%. Based on the nucleotide analysis of the N and G genes, the Korean RABV isolates were confirmed as genotype I of Lyssavirus and classified into four distinct subgroups with high similarity. Phylogenetic analysis showed that the Korean isolates were most closely related to the non-Korean NeiMeng1025B and 857r strains, which were isolated from rabid raccoon dogs in Eastern China and Russia, respectively. These findings suggest that the Korean RABV isolates originated from a rabid raccoon dog in Northeastern Asia. Genetic analysis of the Korean RABV isolates revealed no substitutions at several antigenic sites, indicating that the isolates circulating in Korea may be pathogenic in several hosts.
characterization; genotype I; molecular epidemiology; rabies virus
Rabies is a lethal and notifiable zoonotic disease for which diagnostics have to meet the highest standards. In recent years, an evolution was especially seen in molecular diagnostics with a wide variety of different detection methods published. Therefore, a first international ring trial specifically designed on the use of reverse transcription polymerase chain reaction (RT-PCR) for detection of lyssavirus genomic RNA was organized. The trial focussed on assessment and comparison of the performance of conventional and real-time assays. In total, 16 European laboratories participated. All participants were asked to investigate a panel of defined lyssavirus RNAs, consisting of Rabies virus (RABV) and European bat lyssavirus 1 and 2 (EBLV-1 and -2) RNA samples, with systems available in their laboratory.
The ring trial allowed the important conclusion that conventional RT-PCR assays were really robust assays tested with a high concordance between different laboratories and assays. The real-time RT-PCR system by Wakeley et al. (2005) in combination with an intercalating dye, and the combined version by Hoffmann and co-workers (2010) showed good sensitivity for the detection of all RABV samples included in this test panel. Furthermore, all used EBLV-specific assays, real-time RT-PCRs as well as conventional RT-PCR systems, were shown to be suitable for a reliable detection of EBLVs. It has to be mentioned that differences were seen in the performance between both the individual RT-PCR systems and the laboratories. Laboratories which used more than one molecular assay for testing the sample panel always concluded a correct sample result.
Due to the markedly high genetic diversity of lyssaviruses, the application of different assays in diagnostics is needed to achieve a maximum of diagnostic accuracy. To improve the knowledge about the diagnostic performance proficiency testing at an international level is recommended before using lyssavirus molecular diagnostics e.g. for confirmatory testing.
Rabies virus (RABV) is enzootic throughout Africa, with the domestic dog (Canis familiaris) being the principal vector. Dog rabies is estimated to cause 24,000 human deaths per year in Africa, however, this estimate is still considered to be conservative. Two sub-Saharan African RABV lineages have been detected in West Africa. Lineage 2 is present throughout West Africa, whereas Africa 1a dominates in northern and eastern Africa, but has been detected in Nigeria and Gabon, and Africa 1b was previously absent from West Africa. We confirmed the presence of RABV in a cohort of 76 brain samples obtained from rabid animals in Ghana collected over an eighteen-month period (2007–2009). Phylogenetic analysis of the sequences obtained confirmed all viruses to be RABV, belonging to lineages previously detected in sub-Saharan Africa. However, unlike earlier reported studies that suggested a single lineage (Africa 2) circulates in West Africa, we identified viruses belonging to the Africa 2 lineage and both Africa 1 (a and b) sub-lineages. Phylogeographic Bayesian Markov chain Monte Carlo analysis of a 405 bp fragment of the RABV nucleoprotein gene from the 76 new sequences derived from Ghanaian animals suggest that within the Africa 2 lineage three clades co-circulate with their origins in other West African countries. Africa 1a is probably a western extension of a clade circulating in central Africa and the Africa 1b virus a probable recent introduction from eastern Africa. We also developed and tested a novel reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay for the detection of RABV in African laboratories. This RT-LAMP was shown to detect both Africa 1 and 2 viruses, including its adaptation to a lateral flow device format for product visualization. These data suggest that RABV epidemiology is more complex than previously thought in West Africa and that there have been repeated introductions of RABV into Ghana. This analysis highlights the potential problems of individual developing nations implementing rabies control programmes in the absence of a regional programme.
Rabies virus (RABV) is widespread throughout Africa, with the domestic dog being the principal vector. Dog rabies is estimated to cause 24,000 human deaths per year in Africa, however, this estimate is still considered to be conservative. Two sub-Saharan African RABV lineages (Africa 1 and 2) are thought to circulate in western and central Africa. We confirmed the presence of RABV in a cohort of 76 brain samples obtained from rabid animals in Ghana collected from 2007 to 2009. In addition we developed and tested a novel molecular diagnostic assay for the detection of RABV, which offers an alternative RABV diagnostic tool for African laboratories. Our analysis of the genetic sequences obtained confirmed all viruses to be RABV, however, unlike previous studies we detected two sub-Saharan African RABV viruses (Africa 1 and 2) in this cohort, which included a single virus previously undetected in West Africa. We suggest that there has been repeated introduction of new RABVs into Ghana over a prolonged period from other West African countries and more recently from eastern Africa. These observations further highlight the problems of individual developing nations implementing rabies control programmes at a local, rather than regional level.
A single intramuscular application of the live but not UV-inactivated recombinant rabies virus (RABV) variant TriGAS in mice induces the robust and sustained production of RABV-neutralizing antibodies that correlate with long-term protection against challenge with an otherwise lethal dose of the wild-type RABV. To obtain insight into the mechanism by which live TriGAS induces long-lasting protective immunity, quantitative PCR (qPCR) analysis of muscle tissue, draining lymph nodes, spleen, spinal cord, and brain at different times after TriGAS inoculation revealed the presence of significant copy numbers of RABV-specific RNA in muscle, lymph node, and to a lesser extent, spleen for several days postinfection. Notably, no significant amounts of RABV RNA were detected in brain or spinal cord at any time after TriGAS inoculation. Differential qPCR analysis revealed that the RABV-specific RNA detected in muscle is predominantly genomic RNA, whereas RABV RNA detected in draining lymph nodes is predominantly mRNA. Comparison of genomic RNA and mRNA obtained from isolated lymph node cells showed the highest mRNA-to-genomic-RNA ratios in B cells and dendritic cells (DCs), suggesting that these cells represent the major cell population that is infected in the lymph node. Since RABV RNA declined to undetectable levels by 14 days postinoculation of TriGAS, we speculate that a transient infection of DCs with TriGAS may be highly immunostimulatory through mechanisms that enhance antigen presentation. Our results support the superior efficacy and safety of TriGAS and advocate for its utility as a vaccine.
Rabies virus (RABV) can infect many different species of warm-blooded animals. Glycoprotein G plays a key role in viral pathogenicity and neurotropism, and includes antigenic domains that are responsible for membrane fusion and host cell receptor recognition.
A case of buffalo rabies in China was diagnosed by direct fluorescent antibody test, G gene reverse-transcriptase polymerase chain reaction, and RABV mouse inoculation test. Molecular characterization of the RABV was performed using DNA sequencing, phylogenetic analysis and amino acid sequence comparison based on the G gene from different species of animals.
The results confirmed that the buffalo with suspected rabies was infected by RABV, which was genetically closely related to HNC (FJ602451) that was isolated from cattle in China in 2007. Comparison of the G gene among different species of animal showed that there were almost no amino acid changes among RABVs isolated from the same species of animals that distributed in a near region. However, there were many changes among RABVs that were isolated from different species of animal, or the same species from different geographic regions. This is believed to be the first case report of buffalo rabies in China, and the results may provide further information to understand the mechanism by which RABV breaks through the species barrier.
Bat rabies is an emerging disease of public health significance in the Americas. The Caribbean island of Trinidad experiences periodic outbreaks within the livestock population. We performed molecular characterisation of Trinidad rabies virus (RABV) and used a Bayesian phylogeographic approach to investigate the extent to which outbreaks are a result of in situ evolution versus importation of virus from the nearby South American mainland. Trinidadian RABV sequences were confirmed as bat variant and clustered with Desmodus rotundus (vampire bat) related sequences. They fell into two largely temporally defined lineages designated Trinidad I and II. The Trinidad I lineage which included sequences from 1997–2000 (all but two of which were from the northeast of the island) was most closely related to RABV from Ecuador (2005, 2007), French Guiana (1990) and Venezuela (1993, 1994). Trinidad II comprised sequences from the southwest of the island, which clustered into two groups: Trinidad IIa, which included one sequence each from 2000 and 2007, and Trinidad IIb including all 2010 sequences. The Trinidad II sequences were most closely related to sequences from Brazil (1999, 2004) and Uruguay (2007, 2008). Phylogeographic analyses support three separate RABV introductions from the mainland from which each of the three Trinidadian lineages arose. The estimated dates for the introductions and subsequent lineage expansions suggest periods of in situ evolution within Trinidad following each introduction. These data also indicate co-circulation of Trinidad lineage I and IIa during 2000. In light of these findings and the likely vampire bat origin of Trinidadian RABV, further studies should be conducted to investigate the relationship between RABV spatiotemporal dynamics and vampire bat population ecology, in particular any movement between the mainland and Trinidad.
The Caribbean island of Trinidad experiences periodic rabies virus (RABV) outbreaks within the livestock population. In this study, we inferred the evolutionary history of RABV in the Americas and reconstructed past patterns of RABV geographic spread in order to address the question of whether Trinidadian outbreaks arise from locally maintained RABV or are the result of virus importation from the mainland (presumably via infected bats). Our results provide statistical support for three importation events that gave rise to each of three Trinidadian vampire bat-associated lineages identified in the study. They also indicate limited periods of in situ evolution within Trinidad following each of these introductions. The results also support Mexico and Brazil as major epicenters for the expansion of RABV associated with vampire bats throughout the Americas and consequently to Trinidad. The findings of our study are particularly relevant to local RABV monitoring and control. In addition to justifying vampire bats as the main target for active rabies surveillance and control activities in Trinidad, they suggest that more intense surveillance of regions that lie close to the mainland may be warranted. Finally, in light of these findings, further studies should be conducted to investigate the relationship between RABV spatiotemporal dynamics and vampire bat population ecology.
Control of rabies requires a consistent supply of dependable resources, constructive cooperation between veterinary and public health authorities, and systematic surveillance. These are challenging in any circumstances, but particularly during conflict. Here we describe available human rabies surveillance data from Iraq, results of renewed sampling for rabies in animals, and the first genetic characterisation of circulating rabies strains from Iraq. Human rabies is notifiable, with reported cases increasing since 2003, and a marked increase in Baghdad between 2009 and 2010. These changes coincide with increasing numbers of reported dog bites. There is no laboratory confirmation of disease or virus characterisation and no systematic surveillance for rabies in animals. To address these issues, brain samples were collected from domestic animals in the greater Baghdad region and tested for rabies. Three of 40 brain samples were positive using the fluorescent antibody test and hemi-nested RT-PCR for rabies virus (RABV). Bayesian phylogenetic analysis using partial nucleoprotein gene sequences derived from the samples demonstrated the viruses belong to a single virus variant and share a common ancestor with viruses from neighbouring countries, 22 (95% HPD 14–32) years ago. These include countries lying to the west, north and east of Iraq, some of which also have other virus variants circulating concurrently. These results suggest possible multiple introductions of rabies into the Middle East, and regular trans-boundary movement of disease. Although 4000 years have passed since the original description of disease consistent with rabies, animals and humans are still dying of this preventable and neglected zoonosis.
Control of rabies requires cooperation between government departments, consistent funding, and an understanding of the epidemiology of the disease obtained through surveillance. Here we describe human rabies surveillance data from Iraq and the results of renewed sampling for rabies in animals. In Iraq, it is obligatory by law to report cases of human rabies. These reports were collated and analysed. Reported cases have increased since 2003, with a marked increase in Baghdad 2009–2010. There is no system for detecting rabies in animals and the strains circulating in Iraq have not previously been characterized. To address this, samples were collected from domestic animals in Baghdad and tested for rabies. Three out of 40 were positive for rabies virus. Comparison of part of the viral genetic sequence with other viruses from the region demonstrated that the viruses from Iraq are more closely related to each other than those from surrounding countries, but diverged from viruses isolated in neighbouring countries approximately 22 (95% HPD 14–32) years ago. Although 4000 years have passed since the original description of disease consistent with rabies, animals and humans are still dying of this preventable and neglected zoonosis.
► Universal real-time PCR primer pair demonstrated to hybridize to and detect each of the known Lyssaviruses (including Rabies virus) with greater sensitivity than a standard pan-Lyssavirus hemi-nested RT-PCR typically used. ► Target sequences of bat derived virus species unavailable for analysis (Aravan-, Khujand-, Irkut-, West Caucasian bat- and Shimoni bat virus) were synthesized to produce oligonucleotides and the synthetic DNA was used as a target for primer hybridization.
Rabies virus (RABV) is enzootic throughout most of the world. It is now widely accepted that RABV had its origins in bats. Ten of the 11 Lyssavirus species recognised, including RABV, have been isolated from bats. There is, however, a lack of understanding regarding both the ecology and host reservoirs of Lyssaviruses. A real-time PCR assay for the detection of all Lyssaviruses using universal primers would be beneficial for Lyssavirus surveillance. It was shown that using SYBR® Green, a universal real-time PCR primer pair previously demonstrated to detect European bat Lyssaviruses 1 and 2, and RABV, was able to detect reverse transcribed RNA for each of the seven virus species available to us. Target sequences of bat derived virus species unavailable for analysis were synthesized to produce oligonucleotides. Lagos Bat-, Duvenhage- and Mokola virus full nucleoprotein gene clones enabled a limit of 5–50 plasmid copies to be detected. Five copies of each of the synthetic DNA oligonucleotides of Aravan-, Khujand-, Irkut-, West Caucasian bat- and Shimoni bat virus were detected. The single universal primer pair was therefore able to detect each of the most divergent known Lyssaviruses with great sensitivity.
Lyssavirus; Rabies; Bat; SYBR Green; Real-time PCR; Synthetic DNA
We previously showed that rabies virus (RABV) virions are excellent vehicles for antigen presentation. Here, a reverse genetic approach was applied to generate recombinant RABV that express a chimeric protein composed of the heavy chain carboxyterminal half (HC50) of botulinum neurotoxin type A (BoNT/A) and RABV glycoprotein (G). To promote surface expression and incorporation of HC50/A into RABV virions, the RABV glycoprotein (G) ER translocation sequence, various fragments of RABV ectodomain (ED) and cytoplasmic domain were fused to HC50/A. The HC50/A chimeric proteins were expressed on the surface of cells infected with all of the recombinant RABVs, however, the highest level of surface expression was detected by utilizing 30 amino acids of the RABV G ED (HV50/A-E30). Our results also indicated that this chimeric protein was effectively incorporated into RABV virions. Immunization of mice with inactivated RABV-HC50/A-E30 virions induced a robust anti-HC50/A IgG antibody response that efficiently neutralized circulating BoNT/A in vivo, and protected mice against 1000 fold the lethal dose of BoNT/A.
Previous studies have investigated rabies virus (RABV) epizootiology in Brazilian free-tailed bats (Tadarida brasiliensis) in natural cave roosts. However, little is known about geographic variation in RABV exposure, or if the use of man-made roosts by this species affects enzootic RABV infection dynamics within colonies. We sampled rabies viral neutralizing antibodies in bats at three bridge and three cave roosts at multiple time points during the reproductive season to investigate temporal and roost variation in RABV exposure. We report seropositive bats in all age and sex classes with minimal geographic variation in RABV seroprevalence among Brazilian free-tailed bat colonies in south-central Texas. While roost type was not a significant predictor of RABV seroprevalence, it was significantly associated with seasonal fluctuations, suggesting patterns of exposure that differ between roosts. Temporal patterns suggest increased RABV seroprevalence after parturition in cave colonies, potentially related to an influx of susceptible young, in contrast to more uniform seroprevalence in bridge colonies. This study highlights the importance of life history and roost ecology in understanding patterns of RABV seroprevalence in colonies of the Brazilian free-tailed bat.
Brazilian free-tailed bat; Epizootiology; Rabies virus; Roost ecology
The predominant role of Eptesicus serotinus in the epizootic of bat rabies in Europe was further outlined by the first isolation of the rabies virus from this species in France. The distribution of the virus was studied in naturally infected E. serotinus bats at the time of death and suggested that the papillae of the tongue and the respiratory mucosa may play a role in virus production and excretion. The analysis of 501 French rabies virus isolates from various animal species by antinucleocapsid monoclonal antibodies indicated that transmission of the disease from bats to terrestrial animals is unlikely. The antigenic profile of two isolates from French bats corresponded to that of European bat lyssavirus type 1 (EBL1). Comparisons of 12 different isolates from bats with antinucleocapsid and antiglycoprotein monoclonal antibodies and by direct sequencing of the polymerase chain reaction amplification product of the N gene indicated that EBL1, EBL2, Duvenhage virus (serotype 4 of lyssavirus), and the European fox rabies virus (serotype 1) are phylogenetically distant. They formed four tight genetic clusters named genotypes. EBL1 was shown to be antigenically and genetically more closely related to Duvenhage virus than to EBL2. We propose that EBL1 and EBL2 constitute two distinct genotypes which further serologic characterization will probably classify as new serotypes. We also report a simple method for the rapid characterization of EBL based on the digestion of the polymerase chain reaction product of the N gene by three restriction endonucleases.
The rabies virus (RABV) glycoprotein (G) is the principal antigen responsible for the induction of virus neutralizing antibodies (VNA) and is the major modality of protective immunity in animals. A recombinant RABV HEP-Flury strain was generated by reverse genetics to encode two copies of the G-gene (referred to as HEP-dG). The biological properties of HEP-dG were compared to those of the parental virus (HEP-Flury strain). The HEP-dG recombinant virus grew 100 times more efficiently in BHK-21 cell than the parental virus, yet the virulence of the dG recombinant virus in suckling mice was lower than the parental virus. The HEP-dG virus can improve the expression of G-gene mRNA and the G protein and produce more offspring viruses in cells. The amount of G protein revealed a positive relationship with immunogenicity in mice and dogs. The inactivated HEP-dG recombinant virus induced higher levels of VNA and conferred better protection against virulent RABV in mice and dogs than the inactivated parental virus and a commercial vaccine. The protective antibody persisted for at least 12 months. These data demonstrate that the HEP-dG is stable, induces a strong VNA response and confers protective immunity more effectively than the RABV HEP-Flury strain. HEP-dG could be a potential candidate in the development of novel inactivated rabies vaccines
Until 2008, human rabies had never been reported in French Guiana. On 28 May 2008, the French National Reference Center for Rabies (Institut Pasteur, Paris) confirmed the rabies diagnosis, based on hemi-nested polymerase chain reaction on skin biopsy and saliva specimens from a Guianan, who had never travelled overseas and died in Cayenne after presenting clinically typical meningoencephalitis.
Molecular typing of the virus identified a Lyssavirus (Rabies virus species), closely related to those circulating in hematophagous bats (mainly Desmodus rotundus) in Latin America. A multidisciplinary Crisis Unit was activated. Its objectives were to implement an epidemiological investigation and a veterinary survey, to provide control measures and establish a communications program. The origin of the contamination was not formally established, but was probably linked to a bat bite based on the virus type isolated. After confirming exposure of 90 persons, they were vaccinated against rabies: 42 from the case's entourage and 48 healthcare workers. To handle that emergence and the local population's increased demand to be vaccinated, a specific communications program was established using several media: television, newspaper, radio.
This episode, occurring in the context of a Department far from continental France, strongly affected the local population, healthcare workers and authorities, and the management team faced intense pressure. This observation confirms that the risk of contracting rabies in French Guiana is real, with consequences for population educational program, control measures, medical diagnosis and post-exposure prophylaxis.
Until 2008, rabies had never been described within the French Guianan human population. Emergence of the first case in May 2008 in this French Overseas Department represented a public health event that markedly affected the local population, healthcare workers and public health authorities. The antirabies clinic of French Guiana, located at Institut Pasteur de la Guyane, had to reorganize its functioning to handle the dramatically increased demand for vaccination. A rigorous epidemiological investigation and a veterinary study were conducted to identify the contamination source, probably linked to a bat bite, and the exposed population. Communication was a key factor to controlling this episode and changing the local perception of this formerly neglected disease. Because similar clinical cases had previously been described, without having been diagnosed, medical practices must be adapted and the rabies virus should be sought more systematically in similarly presenting cases. Sharing this experience could be useful for other countries that might someday have to manage such an emergence.
The mechanisms that differentiate rabies infections into furious and paralytic forms remain undetermined. There are no neuropathological features in human brains that distinguish furious and paralytic rabies. This could be due to methodology and/or examination of specimens late in the disease course.
In this study, postmortem examination of brain (5 furious and 5 paralytic) and spinal cord (3 furious and 3 paralytic) specimens was performed in 10 rabies-infected dogs, sacrificed shortly after developing the illness. Rabies virus (RABV) antigen (percentage of positive neurons, average antigen area in positive neurons and average antigen area per neuron) and RNA were quantified at 15 different central nervous system (CNS) regions. The distribution and degree of inflammation were also studied.
More RABV antigen was detected in furious rabies than paralytic in many of the CNS regions studied. Caudal-rostral polarity of viral antigen distribution was found in both clinical forms in order from greatest to least: spinal cord, brainstem, cerebellum, midline structures (caudate, thalamus), hippocampus, and cerebrum. In contrast, RABV RNA was most abundant in the cerebral midline structures. Viral RNA was found at significantly higher levels in the cerebral cortex, thalamus, midbrain and medulla of dogs with the furious subtype. The RNA levels in the spinal cord were comparable in both clinical forms. A striking inflammatory response was found in paralytic rabies in the brainstem.
These observations provide preliminary evidence that RABV antigen and RNA levels are higher in the cerebrum in furious rabies compared to the paralytic form. In addition, brainstem inflammation, more pronounced in paralytic rabies, may impede viral propagation towards the cerebral hemispheres.
Rabies; Furious rabies; Paralytic rabies; Rabies viral antigen; Inflammation
In May of 2010, two communities (Truenococha and Santa Marta) reported to be at risk of vampire bat depredation were surveyed in the Province Datem del Marañón in the Loreto Department of Perú. Risk factors for bat exposure included age less than or equal to 25 years and owning animals that had been bitten by bats. Rabies virus neutralizing antibodies (rVNAs) were detected in 11% (7 of 63) of human sera tested. Rabies virus ribonucleoprotein (RNP) immunoglobulin G (IgG) antibodies were detected in the sera of three individuals, two of whom were also seropositive for rVNA. Rabies virus RNP IgM antibodies were detected in one respondent with no evidence of rVNA or RNP IgG antibodies. Because one respondent with positive rVNA results reported prior vaccination and 86% (six of seven) of rVNA-positive respondents reported being bitten by bats, these data suggest nonfatal exposure of persons to rabies virus, which is likely associated with vampire bat depredation.
Rabies is a zoonotic disease that affects all mammals and leads to more than 55,000 human deaths every year, caused by rabies virus (RABV) (Mononegavirales: Rhabdoviridae: Lyssavirus). Currently, human rabies treatment is based on the Milwaukee Protocol which consists on the induction of coma and massive antiviral therapy. The aim of this study was to assess the decrease in the titer of rabies virus both in vitro and in vivo using short-interfering RNAs. To this end, three siRNAs were used with antisense strands complementary to rabies virus nucleoprotein (N) mRNA. BHK-21 cells monolayers were infected with 1000 to 0.1 TCID50 of PV and after 2 hours the cells were transfected with each of tree RNAs in separate using Lipofectamine-2000. All three siRNAs reduced the titer of PV strain in a least 0.72 logTCID50/mL and no cytotoxic effect was observed in the monolayers treated with Lipofectamine-2000. Swiss albino mice infected with 10.000 to 1 LD of PV strain by the intracerebral route were also transfected after two hours of infection with a pool 3 siRNAs with Lipofectamine-2000 by the intracerebral route, resulting in a survival rate of 30% in mice inoculated with 100 LD50, while the same dose led to 100% mortality in untreated animals. Lipofectamine-2000 showed no toxic effect in control mice. These results suggest that intracerebral administration of siRNAs might be an effective antiviral strategy for rabies.
rabies; RNA interference; siRNAs; antiviral; treatment
Ebolaviruses (EBOV) (family Filoviridae) cause viral hemorrhagic fevers in humans and non-human primates when they spill over from their wildlife reservoir hosts with case fatality rates of up to 90%. Fruit bats may act as reservoirs of the Filoviridae. The migratory fruit bat, Eidolon helvum, is common across sub-Saharan Africa and lives in large colonies, often situated in cities. We screened sera from 262 E. helvum using indirect fluorescent tests for antibodies against EBOV subtype Zaire. We detected a seropositive bat from Accra, Ghana, and confirmed this using western blot analysis. The bat was also seropositive for Lagos bat virus, a Lyssavirus, by virus neutralization test. The bat was fitted with a radio transmitter and was last detected in Accra 13 months after release post-sampling, demonstrating long-term survival. Antibodies to filoviruses have not been previously demonstrated in E. helvum. Radio-telemetry data demonstrates long-term survival of an individual bat following exposure to viruses of families that can be highly pathogenic to other mammal species. Because E. helvum typically lives in large urban colonies and is a source of bushmeat in some regions, further studies should determine if this species forms a reservoir for EBOV from which spillover infections into the human population may occur.
Daubenton bats may roost infrequently in human dwellings, so risk for human contact is low.
We report the first seroprevalence study of the occurrence of specific antibodies to European bat lyssavirus type 2 (EBLV-2) in Daubenton's bats. Bats were captured from 19 sites across eastern and southern Scotland. Samples from 198 Daubenton's bats, 20 Natterer's bats, and 6 Pipistrelle's bats were tested for EBLV-2. Blood samples (N = 94) were subjected to a modified fluorescent antibody virus neutralization test to determine antibody titer. From 0.05% to 3.8% (95% confidence interval) of Daubenton's bats were seropositive. Antibodies to EBLV-2 were not detected in the 2 other species tested. Mouth swabs (N = 218) were obtained, and RNA was extracted for a reverse transcription–polymerase chain reaction (RT-PCR). The RT-PCR included pan lyssavirus-primers (N gene) and internal PCR control primers for ribosomal RNA. EBLV-2 RNA was not detected in any of the saliva samples tested, and live virus was not detected in virus isolation tests.
Lyssavirus; EBLV-2; seroprevalence; Daubenton bats; Scotland; research
Rabies virus (RABV) causes a fatal infection of the central nervous systems (CNS) of warm-blooded animals. Once the clinical symptoms develop, rabies is almost invariably fatal. The mechanism of RABV pathogenesis remains poorly understood. Recent studies have shown that microRNA (miRNA) plays an important role in the pathogenesis of viral infections. Our recent findings have revealed that infection with laboratory-fixed rabies virus strain can induce modulation of the microRNA profile of mouse brains. However, no previous report has evaluated the miRNA expression profile of mouse brains infected with RABV street strain.
The results of microarray analysis show that miRNA expression becomes modulated in the brains of mice infected with street RABV. Quantitative real-time PCR assay of the differentially expressed miRNAs confirmed the results of microarray assay. Functional analysis showed the differentially expressed miRNAs to be involved in many immune-related signaling pathways, such as the Jak-STAT signaling pathway, the MAPK signaling pathway, cytokine-cytokine receptor interactions, and Fc gamma R-mediated phagocytosis. The predicted expression levels of the target genes of these modulated miRNAs were found to be correlated with gene expression as measured by DNA microarray and qRT-PCR.
RABV causes significant changes in the miRNA expression profiles of infected mouse brains. Predicted target genes of the differentially expression miRNAs are associated with host immune response, which may provide important information for investigation of RABV pathogenesis and therapeutic method.
Street strain rabies virus; Brain infection; MicroRNA profiling; Gene profiling; Target prediction; Functional enrichment