Whole genome sequencing and phylogenetic characterisation of rabies virus strains from Moldova and north-eastern Romania

BACKGROUND

Rabies is the oldest fatal zoonotic disease recognised as a neglected tropical disease and is caused by an RNA virus belonging to the genus Lyssavirus, family Rhabdoviridae.

METHODOLOGY/PRINCIPAL FINDINGS

A deep molecular analysis was conducted on full-length nucleoprotein (N) gene and whole genome sequences of rabies virus from 37 animal brain samples collected between 2012 and 2017 to study the circulation of rabies virus (RABV) variants. The overall aim was to better understand their distribution in Moldova and north-eastern Romania. Both Sanger and high throughput sequencing on Ion Torrent and Illumina platforms were performed. Phylogenetic analysis of the RABV sequences from both Moldova and Romania revealed that all the samples (irrespective of the year of isolation and the species) belonged to a single phylogenetic group: north-eastern Europe (NEE), clustering into three assigned lineages: RO#5, RO#6 and RO#7.

CONCLUSIONS/SIGNIFICANCE

High throughput sequencing of RABV samples from domestic and wild animals was performed for the first time for both countries, providing new insights into virus evolution and epidemiology in this less studied region, expanding our understanding of the disease.

OVX033, a nucleocapsid-based vaccine candidate, provides broad-spectrum protection against SARS-CoV-2 variants in a hamster challenge model

Spike-based COVID-19 vaccines induce potent neutralizing antibodies but their efficacy against SARS-CoV-2 variants decreases. OVX033 is a recombinant protein composed of the full-length nucleocapsid (N) protein of SARS-CoV-2 genetically fused to oligoDOM^®, a self-assembling domain which improves antigen immunogenicity. OVX033 including N as an antigenic target is proposed as new vaccine candidate providing broad-spectrum protection against sarbecoviruses. OVX033 demonstrated its ability to trigger cross-reactive T cell responses and cross-protection against three variants of SARS-CoV-2 (B.1 Europe, Delta B.1.617.2, and Omicron B.1.1.529) in a hamster challenge model, as evidenced by lower weight loss, lower lung viral loads, and reduced lung histopathological lesions.

Potency of Veterinary Rabies Vaccines Marketed in Sri Lanka

Seven brands of veterinary rabies vaccines are commercially available in Sri Lanka, but there is no established procedure to test the potency of the vaccines at the local level, especially prior to their release. The aim of this study was to test the potency of these vaccines using a mouse challenge test in collaboration with the EU/WOAH/WHO Reference Laboratory for Rabies, ANSES-Nancy, France. Based on the European Pharmacopoeia, the inactivated rabies vaccines complied with the mouse potency test if the estimated potency is ≥1.0 IU in the smallest prescribed dose. Among the eight tested vaccines, four single-dose preparations (Rabisin™, Raksharab™, Nobivac™ RL, and Nobivac™ Rabies) were compliant, with potencies of 12 IU/dose, 7.2 IU/dose, 4.4 IU/dose, and 3.4 IU/dose, respectively. Three of the single-dose preparations (Canvac™ R, Defensor™ 3, and Rabies killed vaccine) were not compliant, with potency values <1.0 IU/dose. One multidose preparation (Raksharab™ multidose) had a potency of 1.3 IU/dose, even though the test was not validated. Based on these results, it appears that some rabies vaccine batches that are currently available in the local market do not comply with the mouse potency test. Testing the vaccines' potency before registration and release to the market appears to be an important step to allow good immunization to animals during pre-exposure vaccination programs.

EPAC1 Pharmacological Inhibition with AM-001 Prevents SARS-CoV-2 and Influenza A Virus Replication in Cells

The exceptional impact of the COVID-19 pandemic has stimulated an intense search for antiviral molecules. Host-targeted antiviral molecules have the potential of presenting broad-spectrum antiviral activity and are also considered as less likely to select for resistant viruses. In this study, we investigated the antiviral activity exerted by AM-001, a specific pharmacological inhibitor of EPAC1, a host exchange protein directly activated by cyclic AMP (cAMP). The cAMP-sensitive protein, EPAC1 regulates various physiological and pathological processes but its role in SARS-CoV-2 and influenza A virus infection has not yet been studied. Here, we provide evidence that the EPAC1 specific inhibitor AM-001 exerts potent antiviral activity against SARS-CoV-2 in the human lung Calu-3 cell line and the African green monkey Vero cell line. We observed a concentration-dependent inhibition of SARS-CoV-2 infectious viral particles and viral RNA release in the supernatants of AM-001 treated cells that was not associated with a significant impact on cellular viability. Furthermore, we identified AM-001 as an inhibitor of influenza A virus in Calu-3 cells. Altogether these results identify EPAC1 inhibition as a promising therapeutic target against viral infections.

Intranasal type I interferon treatment is beneficial only when administered before clinical signs onset in the SARS-CoV-2 hamster model

Impaired type I interferons (IFNs) production or signaling have been associated with severe COVID-19, further promoting the evaluation of recombinant type I IFNs as therapeutics against SARS-CoV-2 infection. In the Syrian hamster model, we show that intranasal administration of IFN-α starting one day pre-infection or one day post-infection limited weight loss and decreased viral lung titers. By contrast, intranasal administration of IFN-α starting at the onset of symptoms three days post-infection had no impact on the clinical course of SARS-CoV-2 infection. Our results provide evidence that early type I IFN treatment is beneficial, while late interventions are ineffective, although not associated with signs of enhanced disease.

Type I interferons are major antiviral effectors produced by the host in response to viral infections. Importantly, delayed or impaired type I IFN signalling response has been shown to correlate with severe COVID-19. These observations provided further impetus to test the administration of exogenous type I IFN as a treatment against SARS-CoV-2 infection in patients. However, studies using MERS-CoV or SARS-CoV infected mice demonstrated that type I interferon treatment was beneficial when administered early, but was ineffective and even caused deleterious immunopathology when administered at later stages of infection. It is therefore crucial to understand how the timing of the type I IFN treatments modulates their efficacy and safety against SARS-CoV-2. In this preclinical study using the SARS-CoV-2-infected Syrian hamster model, we showed that intranasal type I IFN treatment was beneficial only when administered before the onset of symptoms. Importantly, late treatment was ineffective but was not associated with deleterious effects. This study provides important information to interpret clinical trials showing no to modest effects of type I IFNs in COVID-19 patients.

Hamster and ferret experimental infection with intranasal low dose of a single strain of SARS-CoV-2

Understanding the pathogenesis of the SARS-CoV-2 infection is key to developing preventive and therapeutic strategies against COVID-19, in the case of severe illness but also when the disease is mild. The use of appropriate experimental animal models remains central in the in vivo exploration of the physiopathology of infection and antiviral strategies. This study describes SARS-CoV-2 intranasal infection in ferrets and hamsters with low doses of low-passage SARS-CoV-2 clinical French isolate UCN19, describing infection levels, excretion, immune responses and pathological patterns in both animal species. Individual infection with 103 p.f.u. SARS-CoV-2 induced a more severe disease in hamsters than in ferrets. Viral RNA was detected in the lungs of hamsters but not of ferrets and in the brain (olfactory bulb and/or medulla oblongata) of both species. Overall, the clinical disease remained mild, with serological responses detected from 7 days and 10 days post-inoculation in hamsters and ferrets respectively. The virus became undetectable and pathology resolved within 14 days. The kinetics and levels of infection can be used in ferrets and hamsters as experimental models for understanding the pathogenicity of SARS-CoV-2, and testing the protective effect of drugs.

Multi-annual performance evaluation of laboratories in post-mortem diagnosis of animal rabies: Which techniques lead to the most reliable results in practice?

Rabies diagnosis proficiency tests on animal specimens using four techniques (FAT, RTCIT, conventional RT-PCR and real-time RT-PCR) were organised over 10 years (2009–2019). Seventy-three laboratories, of which 59% were from Europe, took part. As the panels were prepared with experimentally-infected samples, the error rate of laboratories on positive and negative samples was accurately estimated. Based on fitted values produced by mixed modelling including the variable “laboratory” as a random variable to take into account the longitudinal design of our dataset, the technique that provided the most concordant results was conventional RT-PCR (99.3%; 95% CI 99.0–99.6), closely followed by FAT (99.1%; 95% CI 98.7–99.4), real-time RT-PCR (98.7%; 95% CI 98.1–99.3) and then RTCIT (96.8%; 95% CI 95.8–97.7). We also found that conventional RT-PCR provided a better diagnostic sensitivity level (99.3% ±4.4%) than FAT (98.7% ±1.6%), real-time RT-PCR (97.9% ±0.8%) and RTCIT (95.3% ±5.1%). Regarding diagnostic specificity, RTCIT was the most specific technique (96.4% ±3.9%) followed closely by FAT (95.6% ±3.8%), real-time RT-PCR (95.0% ±1.8%) and conventional RT-PCR (92.9% ±0.5%). Due to multiple testing of the samples with different techniques, the overall diagnostic conclusion was also evaluated, and found to reach an inter-laboratory concordance level of 99.3%. The concordance for diagnostic sensitivity was 99.6% ±2.0% and for diagnostic specificity, 98.0% ±8.5%. Molecular biology techniques were, however, found to be less specific than expected. The potential reasons for such findings are discussed herein. The regular organisation of performance tests has contributed to an increase in the performance of participating laboratories over time, demonstrating the benefits of such testing. Maintaining a high-quality rabies diagnosis capability on a global scale is key to achieving the goal of eliminating dog-mediated human rabies deaths. The regular organisation of exercises on each continent using selected local strains to be tested according to the local epidemiological situation is one factor that could help increase reliable diagnosis worldwide. Rabies diagnosis capabilities could indeed be enhanced by providing adequate and sustainable proficiency testing on a large scale and in the long term

This study shares the rabies diagnosis proficiency test results of 73 laboratories on animal specimens using four techniques (FAT, RTCIT, conventional RT-PCR and real-time RT-PCR) organised over a 10-year period. This long-term exercise allowed us to compute accurate sensitivity and specificity values for the rabies diagnosis test for a large panel of laboratories. Conventional RT-PCR provided a better diagnostic sensitivity level than FAT, real-time RT-PCR and RTCIT. Regarding diagnostic specificity, RTCIT was the most specific technique followed closely by FAT, real-time RT-PCR and conventional RT-PCR. The specificity of molecular biology techniques was found to be lower than expected. The potential reasons for such findings are discussed herein. The regular organisation of performance tests has contributed to an increase in the performance of participating laboratories over time, demonstrating the likely benefits of such testing.

Massive transient damage of the olfactory epithelium associated with infection of sustentacular cells by SARS-CoV-2 in golden Syrian hamsters

Anosmia is one of the most prevalent symptoms of SARS-CoV-2 infection during the COVID-19 pandemic. However, the cellular mechanism behind the sudden loss of smell has not yet been investigated. The initial step of odour detection takes place in the pseudostratified olfactory epithelium (OE) mainly composed of olfactory sensory neurons surrounded by supporting cells known as sustentacular cells. The olfactory neurons project their axons to the olfactory bulb in the central nervous system offering a potential pathway for pathogens to enter the central nervous system by bypassing the blood brain barrier. In the present study, we explored the impact of SARS-CoV-2 infection on the olfactory system in golden Syrian hamsters. We observed massive damage of the OE as early as 2 days post nasal instillation of SARS-CoV-2, resulting in a major loss of cilia necessary for odour detection. These damages were associated with infection of a large proportion of sustentacular cells but not of olfactory neurons, and we did not detect any presence of the virus in the olfactory bulbs. We observed massive infiltration of immune cells in the OE and lamina propria of infected animals, which may contribute to the desquamation of the OE. The OE was partially restored 14 days post infection. Anosmia observed in COVID-19 patient is therefore likely to be linked to a massive and fast desquamation of the OE following sustentacular cells infection with SARS-CoV-2 and subsequent recruitment of immune cells in the OE and lamina propria.

Further Evidence of Inadequate Quality in Lateral Flow Devices Commercially Offered for the Diagnosis of Rabies

As a neglected zoonotic disease, rabies causes approximately 5.9 × 10⁴ human deaths annually, primarily affecting low- and middle-income countries in Asia and Africa. In those regions, insufficient surveillance is hampering adequate medical intervention and is driving the vicious cycle of neglect. Where resources to provide laboratory disease confirmation are limited, there is a need for user-friendly and low-cost reliable diagnostic tools that do not rely on specialized laboratory facilities. Lateral flow devices (LFD) offer an alternative to conventional diagnostic methods and may strengthen control efforts in low-resource settings. Five different commercially available LFDs were compared in a multi-centered study with respect to their diagnostic sensitivity and their agreement with standard rabies diagnostic techniques. Our evaluation was conducted by several international reference laboratories using a broad panel of samples. The overall sensitivities ranged from 0% up to 62%, depending on the LFD manufacturer, with substantial variation between the different laboratories. Samples with high antigen content and high relative viral load tended to test positive more often in the Anigen/Bionote test, the latter being the one with the best performance. Still, the overall unsatisfactory findings corroborate a previous study and indicate a persistent lack of appropriate test validation and quality control. At present, the tested kits are not suitable for in-field use for rabies diagnosis, especially not for suspect animals where human contact has been identified, as an incorrect negative diagnosis may result in human casualties. This study points out the discrepancy between the enormous need for such a diagnostic tool on the one hand, and on the other hand, a number of already existing tests that are not yet ready for use.

Detection of rabies antibodies in wild boars in north-east Romania by a rabies ELISA test

Background

In the last few decades, Romania has been considered one of the European countries most affected by animal rabies, but a combination of oral rabies vaccination (ORV) campaigns in foxes alongside mandatory vaccination of pets has substantially decreased the number of rabies cases in recent years.

The objective of this study was to detect rabies antibodies in wild boar serum and thoracic fluid samples collected during the hunting season after ORV campaigns in north-eastern Romania in order to identify if wild boars are substantial competitors to foxes for ORV baits.

Results

When the 312 wild boar samples were tested by ELISA (BioPro ELISA, Czech Republic), 42.31% (132/312) demonstrated rabies antibodies. In order to compare these wild boar results in terms of the percentage of immunisation, fox samples were also included in the study, and in this case only 28.40% (98/345) demonstrated rabies antibodies by ELISA. To check the diagnostic sensitivity and specificity of this ELISA, those samples with a sufficient volume from both species that had tested either negative or positive with an initial ELISA were then tested with the Fluorescent Antibody Virus Neutralisation (FAVN) assay. The overall concordance between the BioPro ELISA and FAVN test was 74.26% (75/101) in wild boar samples and 65.66% (65/99) in fox samples, 140 out of 200 samples being correlated with the two methods, although no significant statistical difference (p = 0.218) between the two species was registered. We found a good agreement by both tests for the ELISA-positive samples (91.30%), however the situation was different for the ELISA-negative samples, where a low agreement was demonstrated (41.18%).

Conclusions

This study reports for the first time the presence of rabies antibodies in wild boar samples collected during the hunting season in Romania after ORV campaigns in rabies endemic areas. It is also the first study to demonstrate that ELISA BioPro can be used on wild boar samples with satisfactory results compared to the FAVN test for this species.

Proficiency test for rabies serology: A design complying with international standards for a reliable assessment of participating laboratories

BACKGROUND

Domestic carnivores can introduce rabies into disease-free countries or areas if they are incubating the disease and transported during the pre-symptomatic period. For pets moved into the European Union, the European Commission decided to establish a system of community approval of laboratories willing to carry out the rabies serological controls to guarantee an effective control system. As the specific institute to coordinate the approval of the laboratories, designated by the European Commission in 2000, our laboratory organizes annual proficiency tests (PT) for laboratories already agreed or willing to be agreed to perform rabies serological controls (by detecting rabies virus neutralizing antibodies only) in the frame of international trade.

METHODOLOGY/PRINCIPAL FINDINGS

The assessment criteria of this PT rely on the analysis of the specificity and the intra-laboratory consistency. The approach used to evaluate the degree of laboratory consistency is based on the use of compiled data obtained from previous PT campaigns, and is measured by the quality of a regression model. By using historical data for calculating assigned values and associated standard deviations, instead of values obtained from only one campaign, they became robust without any additional statistical treatment. In the present paper, more than 800 historical values were compiled for each of the regression parameters.

CONCLUSIONS/SIGNIFICANCE

Since the beginning of these PT schemes in 1999, the overall percentage of failing laboratories remained stable over the years (4.1%) while the number of participants increased to 79 in 2018. This highlighted the robustness and the consistency of the statistical analyses used to assess the laboratory's performance over the years. The improvements carried out and the consistency of our statistical analyses have resulted in the compliance of the rabies serology PT with the ISO/IEC 17043 and ISO 13528:2015 International Standards.

Cross-Protection of Inactivated Rabies Vaccines for Veterinary Use against Bat Lyssaviruses Occurring in Europe

Human rabies vaccines have been shown to induce partial protection against members of phylogroup I bat lyssaviruses. Here, we investigated the capacity of a widely used rabies inactivated vaccine (Rabisin, Boehringer-Ingelheim) for veterinary use to cross-protect mice experimentally infected with European bat lyssavirus 1 (EBLV-1b), European bat lyssavirus 2 (EBLV-2), and Bokeloh bat lyssavirus (BBLV) occurring in Europe. For each lyssavirus, we investigated the efficacy of two different doses of vaccine against two viral doses administrated by either central or peripheral routes. In parallel, seroconversion following pre-exposure vaccination was investigated. In this study, we demonstrated that the three investigated bat isolates were pathogenic, even at low dose, when inoculated by the central route but were not/less pathogenic when administrated peripherally. The Rabisin vaccine was capable of significantly cross-protecting mice inoculated intramuscularly with EBLV-1b and EBLV-2 and intracerebrally with BBLV. The level of rabies neutralizing antibodies induced by the Rabisin was quite high against the bat lyssaviruses, but with no significant differences between immunization with 1 and 5 IU/dose. The study emphasizes that the quality of rabies-inactivated vaccines for veterinary use is of utmost importance to optimize the cross-protection of pets against phylogroup I bat lyssaviruses occurring in Europe.

An inter-laboratory comparison to evaluate the technical performance of rabies diagnosis lateral flow assays

As in previous years, the European Union Reference Laboratory (EURL) for rabies organised in 2018 an Inter-laboratory trial (ILT) on rabies diagnosis. Contrarily to past years, the 2018 ILT did not aim to evaluate the performance of participating laboratories, but the technical performance of new rapid tests. Two lateral Flow Assays (LFA), namely the Anigen® and the CDIA™ Rabies Virus Antigen Rapid Test" (commercialized by Bionote and Creative Diagnostics Cie respectively), were evaluated together with the Fluorescent Antibody Test (FAT). One panel of virus samples (including RABV as well as EBLV1a, EBLV-1b, and EBLV2 strains) was sent to participating laboratories to compare results obtained with these different techniques. The study revealed that the FAT provided a good agreement toward expected results for both negative/positive samples (99.1%). The Anigen® test produced similar results to the FAT, with only one false negative result (0.5%) reported by all participants and a concordance of 100% for all but one sample demonstrating a good inter-laboratory reproducibility of the Anigen® batch. The CDIA™ test produced reproducible results for Rabies Virus (RABV) samples only. However, it hardly detected the Bokeloh Bat Lyssavirus (BBLV) and the European Bat Lyssaviruses types 1b and 2 (EBLV-1b and EBLV-2) in most laboratories resulting in a moderate inter-laboratory concordance (58.4%-82.7%) for these lyssaviruses. The two LFAs provided reliable and reproducible results on all RABV samples (100%) but lead to heterogeneous performances with other lyssaviruses leading to different levels of diagnostic/analytical sensitivity, specificity. The study confirmed that LFAs should be used with caution and that their validation are of upmost importance before any use in laboratories.

Lleida Bat Lyssavirus isolation in Miniopterus schreibersii in France

Bat rabies cases are attributed in Europe to five different Lyssavirus species of 16 recognized Lyssavirus species causing rabies. One of the most genetically divergent Lyssavirus spp. has been detected in a dead Miniopterus schreibersii bat in France. Brain samples were found positive for the presence of antigen, infectious virus and viral RNA by classical virological methods and molecular methods respectively. The complete genome sequence was determined by next-generation sequencing. The analysis of the complete genome sequence confirmed the presence of Lleida bat lyssavirus (LLEBV) in bats in France with 99.7% of nucleotide identity with the Spanish LLEBV strain (KY006983).

Additional Progress in the Development and Application of a Direct, Rapid Immunohistochemical Test for Rabies Diagnosis

Laboratory-based surveillance is fundamental to effective rabies prevention and control. The direct fluorescent antibody (AB) test (FAT) is the gold standard for rabies diagnosis. Recently, additional tests besides the FAT have been developed, such as the direct rapid immunohistochemical test (DRIT). In this study, our objective was to further refine technical aspects of the DRIT using a combination of two monoclonal ABs (MABs), 502 and 802, conduct additional testing among rabies reference laboratories using a diversity of animal species and rabies virus (RV) variants and compare the potential utility of the DRIT for end users via proficiency testing (PT) against the FAT. Considering the ideal molar ratios of biotin to AB in formulation of the DRIT conjugate, 3.9 was found to be superior to 7.4, for detection of RV antigens in the brain of a naturally infected raccoon. Optimization of the DRIT conjugate may also be dependent upon the apparent choice of specific viral antigens for testing, as a gray fox RV variant reacted less strongly than a raccoon RV variant in determining the working dilution of the MAB cocktail. Using the same MABs and protocol, the DRIT was compared to the FAT using more than 800 samples of mammalian brains, representative of more than 25 taxa, including in excess of 250 animal rabies cases from Europe and North America. Sensitivity was determined at 98% (96⁻100%, 95% CI) and specificity was calculated at 95% (92⁻96%, 95% CI). In a comparison among end users, PT of laboratory personnel resulted in values of 77⁻100% sensitivity and 86-100% specificity. Based upon these and previously reported results, the DRIT appears to be a suitable alternative to the FAT for use in lyssavirus diagnosis.

Potentially Zoonotic Bartonella in Bats from France and Spain

We detected Bartonella in 11 of 109 insectivorous bats from France and 1 of 26 bats from Spain. These genetic variants are closely related to bat-associated Bartonella described in Finland and the United Kingdom and to B. mayotimonensis, the agent of a human endocarditis case in the United States.

Bat rabies surveillance in France: first report of unusual mortality among serotine bats

BACKGROUND

Rabies is a fatal viral encephalitic disease that is caused by lyssaviruses which can affect all mammals, including human and bats. In Europe, bat rabies cases are attributed to five different lyssavirus species, the majority of rabid bats being attributed to European bat 1 lyssavirus (EBLV-1), circulating mainly in serotine bats (Eptesicus serotinus). In France, rabies in bats is under surveillance since 1989, with 77 positive cases reported between 1989 and 2016.

CASE PRESENTATION

In the frame of the bat rabies surveillance, an unusual mortality of serotine bats was reported in 2009 in a village in North-East France. Six juvenile bats from an E. serotinus maternity colony counting ~200 individuals were found to be infected with EBLV-1. The active surveillance of the colony by capture sessions of bats from July to September 2009 showed a high detection rate of neutralising EBLV-1 antibodies (≈ 50%) in the colony. Moreover, one out of 111 animals tested was found to shed viable virus in saliva, while lyssavirus RNA was detected by RT-PCR for five individuals.

CONCLUSION

This study demonstrated that the lyssavirus infection in the serotine maternity colony was followed by a high rate of bat rabies immunity after circulation of the virus in the colony. The ratio of seropositive bats is probably indicative of an efficient virus transmission coupled to a rapid circulation of EBLV-1 in the colony.

Comparison of G protein sequences of South African street rabies viruses showing distinct progression of the disease in a mouse model of experimental rabies

Rabies is a fatal zoonotic disease and infections generally lead to a fatal encephalomyelitis in both humans and animals. In South Africa, domestic (dogs) and the wildlife (yellow mongoose) host species maintain the canid and mongoose rabies variants respectively. In this study, pathogenicity differences of South African canid and mongoose rabies viruses were investigated in a murine model, by assessing the progression of clinical signs and survivorship. Comparison of glycoprotein gene sequences revealed amino acid differences that may underpin the observed pathogenicity differences. Cumulatively, our results suggest that the canid rabies virus may be more neurovirulent in mice than the mongoose rabies variant.

A step forward in the quality control testing of inactivated rabies vaccines - extensive evaluation of European vaccines by using alternative methods to the in vivo potency tests

The mouse challenge test still remains the reference method for the potency determination of human and animal inactivated rabies vaccines, and it is still widely used throughout the world. This test suffers from many disadvantages - it is expensive and time consuming, uses a large number of mice, causes significant animal distress, and suffers from high variability. Recently, the European Pharmacopoeia has recognised the use of a serological potency assay (SPA) as an alternative method to the challenge test. This new test is based on the determination of rabies neutralising antibody titres in vaccinated mice, by using the modified Rapid Fluorescent Focus Inhibition Test (mRFFIT). With the objective of adopting this new method for the batch release of inactivated rabies vaccines, we evaluated its performance on a large collection of rabies vaccines currently assessed in our laboratory. The Fluorescent Antibody Virus Neutralisation test (FAVNt) was used in parallel with the mRFFIT, and the results were compared to the mouse challenge test. Our results demonstrate that the SPA is capable of estimating the potency of vaccines formulated with a potency margin well above the minimum of 1IU/dose. For low potency vaccines, this new method demonstrated some limitations, due to the recurrent invalidation of the assay. We have also demonstrated the superior sensitivity of the FAVNt when compared to the mRFFIT, and the importance of minimising the risk of detecting non-responders in vaccinated mice.

Bat rabies in France: a 24-year retrospective epidemiological study

Since bat rabies surveillance was first implemented in France in 1989, 48 autochthonous rabies cases without human contamination have been reported using routine diagnosis methods. In this retrospective study, data on bats submitted for rabies testing were analysed in order to better understand the epidemiology of EBLV-1 in bats in France and to investigate some epidemiological trends. Of the 3176 bats submitted for rabies diagnosis from 1989 to 2013, 1.96% (48/2447 analysed) were diagnosed positive. Among the twelve recognised virus species within the Lyssavirus genus, two species were isolated in France. 47 positive bats were morphologically identified as Eptesicus serotinus and were shown to be infected by both the EBLV-1a and the EBLV-1b lineages. Isolation of BBLV in Myotis nattereri was reported once in the north-east of France in 2012. The phylogenetic characterisation of all 47 French EBLV-1 isolates sampled between 1989 and 2013 and the French BBLV sample against 21 referenced partial nucleoprotein sequences confirmed the low genetic diversity of EBLV-1 despite its extensive geographical range. Statistical analysis performed on the serotine bat data collected from 1989 to 2013 showed seasonal variation of rabies occurrence with a significantly higher proportion of positive samples detected during the autumn compared to the spring and the summer period (34% of positive bats detected in autumn, 15% in summer, 13% in spring and 12% in winter). In this study, we have provided the details of the geographical distribution of EBLV-1a in the south-west of France and the north-south division of EBLV-1b with its subdivisions into three phylogenetic groups: group B1 in the north-west, group B2 in the centre and group B3 in the north-east of France.

First isolation of a rabid bat infected with European bat lyssavirus in Luxembourg

Rabid bats are regularly reported in Europe, especially in countries that have implemented a bat surveillance network. In May 2013, bat rabies was evidenced for the first time in Luxembourg (southern city of Differdange). The rabies virus, an EBLV-1b strain, was diagnosed in a serotine bat that bit a 29-year-old male person while he was asleep. The man received rapidly a post-exposure RABV treatment and was put under strict medical supervision.

Isolation of Bokeloh bat lyssavirus in Myotis nattereri in France

Bokeloh bat lyssavirus (BBLV) was found in Myotis nattereri for the first time in northeastern France in July 2012. The complete genome sequence of the virus from the infected Natterer's bat was determined by whole-genome sequencing and compared to that of the first BBLV strain isolated in 2010 in Germany and with those of all currently identified lyssaviruses. The French isolate [KC169985] showed 98.7 % nucleotide sequence identity to the German BBLV strain [JF311903]. Several organs of the infected French bat were examined by classical rabies diagnostic methods: fluorescent antibody test, cell culture inoculation test and RT-qPCR. Antigen, infectious virus and high viral RNA levels were found in both the brain and salivary glands. Traces of genomic RNA were detected in the bladder, kidney and lung tissue. The results of an investigation of the distribution of lyssaviruses with the detection of infectious virus in the salivary glands suggest a possible mode of transmission of the virus.

Official batch control of rabies veterinary vaccines: current situation and perspectives in the European Union

The use of seroneutralisation techniques is the first concrete step toward the replacement of the mouse challenge test and its derivatives for the batch testing of rabies vaccines

Comparative assay of fluorescent antibody test results among twelve European National Reference Laboratories using various anti-rabies conjugates

Twelve National Reference Laboratories (NRLs) for rabies have undertaken a comparative assay to assess the comparison of fluorescent antibody test (FAT) results using five coded commercial anti-rabies conjugates (Biorad, Bioveta, Fujirebio, Millipore, and SIFIN conjugates). Homogenized positive brain tissues infected with various lyssavirus species as well as negative samples were analyzed blindly using a standardized FAT procedure. Conjugates B, C, D, and E were found to be significantly more effective than conjugate A for GS7 (French RABV) diluted samples (1/8 and 1/100) while the frequency of concordant results of conjugates C and D differ significantly from conjugates A, B and E for CVS 27. For detection of EBLV-1 strains, conjugates C and D also presented a significantly lower frequency of discordant results compared to conjugates A, B and E. Conjugates B, C and D were found to be significantly more effective than conjugates E and A for EBLV-2 and ABLV samples. In view of these results, conjugates C and D set themselves apart from the others and appeared as the most effective of this 5-panel conjugates. This study clearly demonstrates that the variability of conjugates used by National Reference Laboratories can potentially lead to discordant results and influence assay sensitivity. In case of false negative results this could have a dramatic impact if the animal under investigation is responsible for human exposure. To avoid such situations, confirmatory tests should be implemented.

Evaluation of a Rapid Immunochromatographic Diagnostic Test for the detection of rabies from brain material of European mammals

The surveillance of rabies relies on investigations conducted on dead suspected animals or animals showing clinical signs suggestive of rabies. An immunochromatographic method based on lateral flow principle has been evaluated against a collection of brain samples mainly of European mammals including bats. The performance of this new test has been compared to the conventional gold standard methods: the fluorescent Antibody Test (FAT) and the Rapid Tissue Culture Infection Test (RTCIT). This test enabled the detection of various rabies strains belonging to rabies species 1, 5, 6 and 7 and demonstrated an overall specificity of 100% and a sensitivity of more than 88% when compared to FAT and RTCIT. A total agreement between the Rapid Immunochromatographic Diagnostic Test and conventional technique results have been obtained for European bat samples.

A quantitative indirect ELISA to monitor the effectiveness of rabies vaccination in domestic and wild carnivores

This paper reports a new ELISA to measure the level of rabies anti-glycoprotein G antibodies after vaccination. The Platelia Rabies II kit was evaluated on different populations of dogs, cats and foxes. For each target species, sera from naive, unvaccinated and vaccinated animals were tested. Platelia Rabies II results were compared to the reference fluorescent antibody virus neutralisation test (for dogs and cats) and to a published in house ELISA test (for foxes). The Platelia Rabies II test was found to be highly specific whatever the species (more than 98%) using a cut-off value of 0.5 EU/ml. The index of sensitivity was between 92.4% and 94.5% for fox samples, and reached 83% for domestic carnivores. Data collected by testing field samples revealed that the rate of false negative results ranged between 8.9% and 11.1% and the rate of false positive results ranged between 1% and 2% for the dog/cat population. Therefore, the Platelia Rabies II test described here would be a good candidate for routine detection of rabies antibodies not only in domestic carnivores (within the framework of international trade) but also in foxes for the follow up of rabies oral vaccination programs.

Collaborative study to evaluate a new ELISA test to monitor the effectiveness of rabies vaccination in domestic carnivores

To prevent any introduction of rabies, many rabies-free countries have adopted a scheme requiring the rabies vaccination of pets associated with a serological test. FAVN test and RFFIT are the current OIE prescribed techniques to perform this assay. A qualitative indirect ELISA (Serelisa) test has been recently described as a screening test to monitor the effectiveness of rabies vaccination of pets. A lack of sensitivity requires ELISA negative samples to be retested using an OIE confirmatory test. This raised the question whether this new test could be reasonably proposed as an alternative tool in the context of international trades of pets. The Community Reference Institute of Nancy organized a short trial to answer this question. In this study, 16 laboratories tested a panel of their own samples with FAVN test/RFFIT and the Serelisa. The comparison of results revealed that the performance of the Serelisa is highly heterogeneous. A lack of sensitivity was detected in 50% of participants, when 25% of laboratories obtained a significant rate of false positive results. This last point questions the pertinence of using the Serelisa in the context of international trades by preventing any movements of insufficiently or non-protected animals.

Tools for rabies serology to monitor the effectiveness of rabies vaccination in domestic and wild carnivores

Serology remains the only way to monitor the effectiveness of vaccination of humans and animals against rabies. Many techniques for determining the level of rabies antibodies have been described, including seroneutralisation techniques such as tests for fluorescent antibody virus neutralisation (FAVN) and rapid fluorescent focus inhibition (RFFIT), enzyme-linked immunosorbent assay (ELISA), and in-vivo tests (the mouse neutralisation test, MNT). The need to verify the effectiveness of rabies vaccination has become widespread, particularly in the context of international trading of domestic carnivores from infected to rabies-free territories. The standardisation of serological techniques, approval of laboratories and proficiency tests are key concepts to ensure the practicability of such systems. Serological tests for rabies are also often used by laboratories in infected territories to assess the efficacy of campaigns aimed at the eradication of the disease via oral vaccination of wildlife. The adaptation of these methods should provide the means to titrate specific antibodies in dogs during mass parenteral vaccination in countries infected by canine rabies. However, in most cases these serological tests are carried without any standardised procedure. On the basis of our experience in rabies serology and its harmonisation throughout laboratories worldwide, we propose here an adapted standard technique for the serological monitoring for rabies in wildlife at the European level. Such harmonisation would allow the monitoring of vaccination campaigns to be enhanced by increasing the exchange of epidemiological data, with the ultimate goal being the eradication of rabies in Europe.

Neutralising antibody titration in 25,000 sera of dogs and cats vaccinated against rabies in France, in the framework of the new regulations that offer an alternative to quarantine

Regulations governing international movements of domestic carnivores from rabies-infected to rabies-free countries have recently been loosened, with the adoption of a system that combines vaccination against rabies and serological surveillance (neutralising antibody titration test with a threshold of 0.5 UI/ml). Since 1993, the Research Laboratory for Rabies and Wild Animal Pathology in Nancy, France, has analysed over 25,000 sera from dogs and cats using a viral seroneutralisation technique. The statistical analyses performed during this time show that cats respond better than dogs. Although no significant difference in titres was observed between primovaccinated and repeat-vaccinated cats, repeat-vaccinated dogs had titres above 0.5 IU/ml more frequently. In primovaccinated dogs, monovalent vaccines offered a better serological conversion rate than multivalent ones. Finally, the results of these analyses showed a strong correlation between antibody counts and the time that elapsed between the last vaccination and the blood sampling.

Development of a qualitative indirect ELISA for the measurement of rabies virus-specific antibodies from vaccinated dogs and cats

A protocol suitable for the detection of rabies virus-specific antibodies in serum samples from companion animals using an enzyme linked immunosorbent assay (ELISA) is described. This method has been used successfully for the qualitative assessment of rabies virus-specific antibodies in serum samples from a cohort of vaccinated dogs and cats. In two initial field studies, a variable population of field samples from the Veterinary Laboratories Agency (VLA), United Kingdom were tested. In the first study (n = 1000), the number of false-positive and false-negative results was 11 samples (1.1%) and 67 samples (6.7%), respectively. In the second study (n = 920), the number of false-positive and false-negative results was 7 samples (0.8%) and 52 samples (5.7%). In a third study, undertaken at l'Agence Française de Sécurité Sanitaire des Aliments (AFSSA), Nancy, France (n = 440), 1 false-positive sample (0.23%) and 91 (20.7%) false-negative samples were identified. Data generated using this prototype ELISA indicate a strong correlation for specificity when compared to the gold standard fluorescent antibody virus neutralisation (FAVN) test. Although the ELISA has a lower sensitivity than the FAVN test, it is a useful tool for rapidly screening serum samples from vaccinated companion animals. Using a cut-off value of 0.6 EU/ml, the sensitivity (R = % from VLA and 79% from AFSSA) and specificity (R = 97.3%) indices between the ELISA compared favourably with data generated using the FAVN test. The major advantages of the ELISA test are that it is a qualitative tool that can be completed in four hours, does not require the use of live virus and can be performed without the need for specialised laboratory containment. This contrasts with 4 days using conventional rabies antibody virus neutralisation assays. Using the current format, the ELISA assay described would be a valuable screening tool for the detection of rabies antibodies from vaccinated domestic animals in combination with other Office International des Epizooties (OIE) accepted serological tests.

Efficacy of rabies immunoglobulins in an experimental post-exposure prophylaxis rodent model

In a recently published Syrian hamster animal challenge study [Vaccine 19 (2001) 2273], a highly purified, heat-treated equine rabies immunoglobulin (pERIG HT, Favirab) did not elicit satisfactory protection. The efficacies of this batch, a second stage pERIG HT batch and reference RIG preparations (Imorab, Imogam Rage pasteurised, Berna antiserum) were compared in mice challenged with either Ariana canine field strain or CVS strain. Survival rates against Ariana challenge with the second pERIG HT batch were indistinguishable from those of other licensed preparations (83-90% survival), but the deficient batch did not provide satisfactory protection (53%). These data confirm the inadequate response to a first stage pERIG HT batch, but a current batch provides equivalent protection to that afforded by licensed HRIG and ERIG preparations.

Immunolabeling of CD3-positive lymphocytes with a recombinant single-chain antibody/alkaline phosphatase conjugate

G3(3) is a novel murine monoclonal antibody directed against the CD3 antigen of human T lymphocytes which could be used to analyze lymphoid malignancies. We have produced and characterized a recombinant colorimetric immunoconjugate with the antigen-binding specificity of antibody G3(3). A gene encoding a single-chain antibody variable fragment (scFv) was assembled using the original hybridoma cells as a source of antibody variable heavy (VH) and variable light (VL) chain genes. The chimeric gene was introduced into a prokaryotic expression vector in order to produce a soluble scFv fused to bacterial alkaline phosphatase. DNA sequencing and Western blotting analyses demonstrated the integrity of the soluble immunoconjugate recovered from induced recombinant bacteria. The scFv/AP protein was bifunctional and similar in immunoreactivity to the parent G3(3) antibody. Flow cytometry and immunostaining experiments confirmed that the activity of the scFv/AP protein compares favourably with that of the parent antibody. The scFv/AP conjugate was bound to CD3 antigen at the surface of T cells and was directly detected by its enzymatic activity. Thus this novel fusion protein has potential applications as an immunodiagnostic reagent.