Multicenter comparative study of a new ELISA, PLATELIA™ RABIES II, for the detection and titration of anti-rabies glycoprotein antibodies and comparison with the rapid fluorescent focus inhibition test (RFFIT) on human samples from vaccinated and non-vaccinated people

Comparing Intradermal (ID) Rabies Vaccination with Conventional IM Regimen on Humoral Response of New Zealand White Rabbits for the Production of Animal-Derived Polyclonal Antibodies

In developing countries, it is imperative to implement cost-effective strategies for animal humoral response development in the production of antiserum. This study compared the effect of immunization regimens on the humoral immune response of New Zealand White (NZW) rabbits (N = 24) using cell culture rabies vaccine (CCRV) through intradermal (ID) and traditional intramuscular (IM) routes. The rabbits were divided into three experimental groups: (a) IPC-R2 with a two-site one-week regimen; (b) TRC-R3 with a two-site twenty-eight-day regimen; and (c) Alternate-R4 with a four-site one-week regimen. These regimens were then compared to the standard IM schedule of five doses of rabies vaccine administered at days 0, 3, 7, 14, and 28 in control group R-1. The results were evaluated at days 14 and 35 postvaccination using rabies-specific Platelia II™ ELISA kit method. The results showed a better response to the ID regimen than the IM route regarding immunogenicity and volume consumption of the vaccine. The three selected ID regimes showed significantly higher mean titer values than the control IM regimen group R-1 (p < 0.001). The study aims to explore simple immunization strategies to enhance the RV-specific antibody titers for immunization donor animals. This method would produce polyclonal antibodies and strengthen local production of polyclonal antibodies in Pakistan to deal with vaccine and rabies immunoglobulin (RIG) shortage, thus providing effective postexposure prophylaxis (PEP) for better control of rabies in developing countries.

Evaluation of an iELISA for detection and quantification of rabies antibodies in domestic dog sera

Many rabies endemic-countries have recognized rabies as a public health problem that can be eliminated. As a result, some countries have started implementing small-scale vaccination programs with the aim of scaling them up. Post-vaccination serological monitoring is crucial to assess the efficacy of these programs. The recommended serological tests, the rapid fluorescent focus inhibition test, and the fluorescent antibody virus neutralization (FAVN) are accurate; however, the procedures require considerable expertise and must be carried out in high containment facilities, which are often not available in rabies endemic countries. Given these constraints, enzyme linked immunosorbent assays (ELISAs) have been considered as alternative methods to neutralization tests. This is the first study to evaluate, under field conditions, the performance of the commercial rabies indirect-ELISA (iELISA), the PlateliaTM Rabies II kit ad usum Veterinarium kit, using sera from domestic dogs. Serum samples were collected from two groups of community dogs in northern Tanzania: i) dogs with no history of vaccination against rabies (n = 100) and ii) dogs vaccinated with the Nobivac Canine Rabies® vaccine (n = 101) four weeks previously. When compared to the gold standard FAVN test, the iELISA was found to be 99% specific and 98% sensitive and there was a significant correlation between the two tests (p < 0.001, r = 0.92). Given these findings, we conclude that the PlateliaTM Rabies II kit ad usum Veterinarium can be considered a valuable tool for the rapid assessment of vaccination status of animals in vaccination programs.

Development and Evaluation of an Enzyme-Linked Immunosorbent Assay Targeting Rabies-Specific IgM and IgG in Human Sera

Immunity from rabies depends on rabies virus neutralizing antibodies (RVNA) induced after immunization; however, the influence of antibody isotype switching has not been extensively investigated. This has become particularly relevant with changes in World Health Organization (WHO) recommended rabies vaccine regimens that may influence RVNA isotype kinetics, potentially affecting the peak, and longevity, of RVNA immunoglobulin (IgG) levels. We developed rapid and reliable assays for quantifying the anti-rabies IgM/IgG class switch in human serum based on an indirect ELISA technique. The immune response was tracked in ten individuals naïve to the rabies vaccine by quantifying serum titers weekly, from day seven to day 42 post-immunization, using a serum neutralization assay and the ELISA IgM/IgG assays. The average RVNA IU/mL levels were at D0 ≤ 0.1, D7 0.24, D14 8.36, D21 12.84, D28 25.74 and D42 28.68. Levels of specific IgM antibodies to rabies glycoprotein (EU/mL) were higher, on average, at D7, 1.37, and from D14, 5.49, to D21, 6.59. In contrast, average IgG antibodies (EU/mL) predominated from D28, 10.03, to D42, 14.45. We conclude that levels of anti-rabies IgM/IgG at D28 characterize the isotype class switch. These assays, combined with serum neutralization assays, distinguished the RVNA levels in terms of the IgM/IgG responses and are expected to add to the diagnostic repertoire, provide additional information in establishing rabies vaccine regimens, both post- and pre-exposure prophylaxis, and contribute to research efforts.

Intravitam Diagnosis of Rabies in Patients with Acute Encephalitis: A Study of Two Cases

Rabies is one of the oldest known zoonotic diseases. Rhabdovirus, an RNA virus belonging to the genus Lyssavirus and family Rhabdoviridae, causes rabies. Rabies diagnosis is challenging as the rabies virus remains confined to neurons after the initial animal bite. It largely remains immune-evasive until the infection reaches the central nervous system. The bottleneck in rabies diagnosis remains the non-availability of technical expertise and failure to collect an appropriate sample. The laboratory confirmation of rabies in both antemortem and postmortem samples is important. The samples were tested for anti-rabies antibodies using quantitative ELISA. In this report, two case studies are presented to demonstrate the suitability of ELISA for the intra vitam diagnosis of rabies using cerebrospinal fluid (CSF) as a diagnostic sample. The interpretation of serology results for both vaccinated and unvaccinated individuals has been discussed in detail, which has helped to confirm the antemortem diagnosis of rabies. In this report, we observed that ELISA can be a viable alternative for anti-rabies antibody detection in CSF and can be used as a viable alternative to more technically challenging tests, such as Rapid Fluorescent Focus Inhibition Test (RFFFIT) and Immunofluorescence Assays (IFA).

[Competitive ELISA test system for the detection of antibodies to the rabies virus in animals (Rhabdoviridae: <I>Lyssavirus</I>)]

INTRODUCTION

The main approach to the rabies prevention is the vaccination of domestic and wild carnivores. For the routine evaluation the anti-rabies vaccination effectiveness, World Organization for Animal Health (OIE) recommends various enzyme-linked immunosorbent assays (ELISA).The aim of the study was to design and validate a competitive ELISA (cELISA) test system for the detection of antibodies to the rabies virus (RABV).

MATERIALS AND METHODS

The development of the cELISA was carried out following the OIE recommendations.

RESULTS

The repeatability of the cELISA results within one laboratory was satisfactory (coefficient of variation 7.95-13.61%). The coefficient of determination (CD) between the results of the virus neutralization reaction (FAVN) and cELISA was 0.988, p &lt; 0.001. The lower threshold for antibody detection was less than 0.02 IU/ml. The cELISA did not demonstrate cross-reactivity against antibodies to canine distemper virus, parainfluenza virus, parvovirus, coronavirus, and canine adenovirus (types I and II). During the study of 137 dog blood sera, diagnostic specificity (DSp) and diagnostic sensitivity (DSe) for the cELISA were 83.1% and 94.9%, respectively, and CD between the cELISA and FAVN results was 0.968, p &lt; 0.001.

DISCUSSION

Indirect ELISA test systems for determining the level of antibodies to RABV are not sensitive enough compared to reference tests, unlike cELISA. The developed test system is not inferior for its DSp and DSe to the commercial cELISA BioPro ELISA Rabies Ab (DSp 66.7%, DSe 94.4%).

CONCLUSION

The developed cELISA test system can be used to detect antibodies to RABV in the blood serum of dogs for evaluating the effectiveness of mass vaccination programs.

Establishment and clinical validation of an in-cell-ELISA-based assay for the rapid quantification of Rabies lyssavirus neutralizing antibodies

Neutralizing antibodies (nAbs) prevent the entry of viruses into permissive cells. Since nAbs represent correlates of protection against the Rabies lyssavirus, the presence of sufficient nAbs indicates effective vaccination. Accordingly, Rabies lyssavirus-specific nAb titers need to be determined in routine diagnostics to identify individuals being at risk of Rabies lyssavirus infections due to insufficient immunity. The current gold standard for the quantification of Rabies lyssavirus-specific nAbs is the rapid fluorescent focus inhibition test (RFFIT). However, RFFITs are expensive and labor-intensive since multiple microplate wells must be evaluated one-by-one by trained personnel through microscopic inspection, which limits the number of samples that can be processed. To overcome this disadvantage, we established a novel assay for Rabies lyssavirus-specific nAbs relying on an in-cell-ELISA (icELISA)-based neutralization test (icNT). The icNT differs from the RFFIT in the readout phase, and can be automatically quantified in minutes using broadly available microplate readers. During the establishment, icNT parameters such as antibody concentrations, permeabilization procedures, blocking reagents, infectious doses, and the duration of infection were optimized. Afterwards, a dose-dependent detection of Rabies lyssavirus neutralization was demonstrated using the WHO Standard Rabies Immunoglobulin reference. A panel of 200 sera with known RFFIT titers revealed very good sensitivity and specificity of the icNT. Furthermore, the icNT showed very good intra- and inter-assay precision. By recognizing Rabies lyssavirus-specific antigens, the assay can be applied immediately to automatically quantify the concentration of Rabies lyssavirus nAbs in routine diagnostics or for various basic research questions such as screening for antiviral compounds.

A Comparative Evaluation of the Estimation of Rabies Virus Antibodies among Free-Roaming, Vaccinated Dogs in Bengaluru, India

Vaccination is the practical solution for the prevention of rabies in dogs. Assessment of the immunogenicity of vaccination includes estimation of specific rabies virus neutralizing antibodies (VNA) in the target species. We undertook a study to estimate the levels of VNA in free-roaming dogs with a history of rabies vaccination in Bengaluru city, India. We compared the rapid fluorescent focus inhibition test (RFFIT) and an in-house quantitative indirect ELISA (iELISA). The study area comprised the jurisdiction of Bruhat Bengaluru Mahanagara Palike (BBMP), the Bengaluru civic body. The BBMP, along with several non-government organizations (NGO), were conducting a trap- neuter- vaccinate- release program for the prevention of dog rabies. Serum samples were collected from 250 free-roaming dogs from representative regions of BBMP, of which 125 had a VNA titre of 0.5 IU or more by the RFFIT. Furthermore, 126 dogs showed percent positivity values (PP values) more than the cut off PP value of 57.1 by the iELISA, accounting for 50.4% of satisfactory post-vaccinal serum conversion. The sensitivity and specificity of the iELISA was 94.4% and 95.2%, respectively. Based on these data, a quantitative iELISA may be a complementary tool for sero-monitoring immune responses of free-ranging animals after rabies vaccination.

A comparative review of serological assays for the detection of rabies virus-specific antibodies

Rabies is a major public health problem with a fatality rate close to 100%, caused by a virus of the Lyssavirus genus, of which rabies virus (RABV) is the prototype. Nonetheless, the complete prevention can be achieved by the induction of neutralizing antibodies by pre- or post-exposure prophylaxis. According to the world health organization (WHO) and World Organization for animal health (OIE), serum titers of rabies virus neutralizing antibodies (RVNA) that are higher or equal to 0.5 international units (IU)/ml indicate adequate immune response after vaccination against rabies. Currently, RFFIT and FAVN are the gold standard tests recommended by both WHO and OIE for detecting and quantitating RVNA in biological samples from individuals or animals previously vaccinated and/or subjects suspected of having been infected by RABV. Although the tests RFFIT and FAVN are efficient, they are time-consuming, labor-intensive manual tests and not cost-effective for routine use. Following the previously mentioned, approaches with alternative methods have been developed to detect RVNA or rabies-specific antibodies in human or animal serum, but with variable success. This work summarizes the advances in the serological assays for the detection of neutralizing antibodies or rabies antibodies and assesses the individual immune status after vaccination against rabies, as well as the mechanisms of RABV neutralization mediated by antibodies. Therefore, the main alternative methods for the determination of RABV or rabies-specific antibodies are exposed, with promising results, besides being easy to execute, of low cost, and representing a possibility of being applied, according to the proposal of each test to the network of Rabies Surveillance Laboratories.

The role of nanoparticle format and route of administration on self-amplifying mRNA vaccine potency

The efficacy of RNA-based vaccines has been recently demonstrated, leading to the use of mRNA-based COVID-19 vaccines. The application of self-amplifying mRNA within these formulations may offer further enhancement to these vaccines, as self-amplifying mRNA replicons enable longer expression kinetics and more potent immune responses compared to non-amplifying mRNAs. To investigate the impact of administration route on RNA-vaccine potency, we investigated the immunogenicity of a self-amplifying mRNA encoding the rabies virus glycoprotein encapsulated in different nanoparticle platforms (solid lipid nanoparticles (SLNs), polymeric nanoparticles (PNPs) and lipid nanoparticles (LNPs)). These were administered via three different routes: intramuscular, intradermal and intranasal. Our studies in a mouse model show that the immunogenicity of our 4 different saRNA vaccine formulations after intramuscular or intradermal administration was initially comparable; however, ionizable LNPs gave higher long-term IgG responses. The clearance of all 4 of the nanoparticle formulations from the intramuscular or intradermal administration site was similar. In contrast, immune responses generated after intranasal was low and coupled with rapid clearance for the administration site, irrespective of the formulation. These results demonstrate that both the administration route and delivery system format dictate self-amplifying RNA vaccine efficacy.

Review of Detection and Quantification of Rabies Virus Antibodies

Rabies is an almost invariably fatal disease. According to the World Health Organization (WHO), rabies virus neutralizing antibody (RVNA) titers of ≥0.5 IU/mL are considered adequate for rabies protection. Therefore, detection and quantification of RABV antibodies are important. Many methods have been developed for detecting RABV antibodies. In the present study, we reviewed several methods of detecting RABV antibodies in human and animal samples and evaluated and compared their performance. Of 34 methods, 5 demonstrated unsatisfactory sensitivity or specificity. The others exhibited sensitivity and specificity of ≥75%. The correlation coefficient for five of eight methods was >0.8. The Bland-Altman mean bias of five of five methods was <±2.0. The kappa values of 25 of 28 methods were higher than 0.4, demonstrating at least moderate agreement. Analysis of the performance of these methods emphasized that any new technology should be considered carefully and objectively before being used as an appropriate and applicable alternative.

Detection and quantification of anti-rabies glycoprotein antibodies: current state and perspectives

Abstract

Rabies is an ancient fatal disease with no other available treatment than post-exposure vaccination, where the bite of infected animals, mainly dogs, is the leading cause of its transmission to human beings. In this context, global vaccination campaigns of companion animals, as well as wildlife reservoirs vaccination, are key factors to achieve the “Zero by 30” plan that pursues the eradication of dog-mediated human rabies by 2030. Rabies virus-neutralizing antibodies (VNAs) play an essential role in the disease protection, as it correlates with an adequate immune response and allows evaluating pre- or post-exposure prophylaxis efficacy. Hence, counting with reliable, accurate, and robust serological tests is of paramount importance. Currently, RFFIT and FAVN are the gold standard VNAs tests recommended by both the WHO and the OIE. Despite these methodologies are efficient and widely used, they present several drawbacks, as they are less easily to standardize and require the use of live rabies virus, containment facilities, and skilled professionals. Thus, in this review, we describe the state-of-the-art of alternative analytical methodologies currently available for rabies serology, with novel approaches based on pseudotyped recombinant viruses and emphasizing in the antigen binding methodologies that detect and quantify antibodies against the rabies glycoprotein. We discussed the wide range of assays that are interesting tools for a faster measurement of anti-rabies glycoprotein antibodies and, in some cases, less complex and more versatile than the gold standard methods. Finally, we discussed the key issues during the design and optimization steps of ELISA assays, highlighting the importance of validation and standardization procedures to improve rabies serology tests and, as a consequence, their results.

Key points

• An exhaustive revision of rabies serology testing was made.

• No rabies serology assay can be thought as better than others for all intents and purposes.

• The validation procedure guarantees reliable and consistent results among the globe.

Challenges of Rabies Serology: Defining Context of Interpretation

The case fatality rate of rabies, nearly 100%, is one of the most unique characteristic of this ancient virus infection. The crucial role rabies virus neutralizing antibody plays in protection is both well established and explanation of why rabies serology is important. Various laboratory methods can and have been used but serum neutralization methods have long been the gold standard due to the ability to measure function (neutralization), however these methods can be difficult to perform for several reasons. Assays such as enzyme linked absorbance assays (ELISA), indirect fluorescence antibody (IFA) and more recently lateral flow methods are in use. Interpretation of results can be problematic, not only between methods but also due to modifications of the same method that can lead to misinterpretations. A common assumption in review of laboratory test results is that different methods for the same component produce comparable results under all conditions or circumstances. Assumptions and misinterpretations provide the potential for detrimental decisions, ranging from regulatory to clinically related, and most importantly what ‘level’ is protective. Review of the common challenges in performance and interpretation of rabies serology and specific examples illuminate critical issues to consider when reviewing and applying results of rabies serological testing.

Serosurveillance of rabies antibodies in dogs in Mumbai region by using indirect ELISA

Rabies is a highly fatal viral infection of the central nervous system affecting all warm-blooded animals including humans. To implement the preventive and control measures, it is important to decide the status of anti-rabies antibodies in dogs. Out of 120 serum samples, 47 (39.2 %) serum samples, showed an antibody titre equal to or above the cut off value of 0.5 IU/ml. The maximum number of dogs showed anti-rabies antibody titres equal to or above the cut-off value of 0.5 IU/ml after <1 month pre-exposure to the rabies vaccine. In 15 serum samples of pet dogs, we observed 13 (86.66 %) dogs with protective anti-rabies antibody titre. Statistical analysis suggests that the age of the animal had no significant effect on anti-rabies antibody titre in vaccinated pet dogs. The overall low seroprevalence of anti-rabies antibody in stray dogs indicates their susceptibility to rabies infection and thus posing a risk of rabies to other animals and humans.

Systematic Booster after Rabies Pre-Exposure Prophylaxis to Alleviate Rabies Antibody Monitoring in Individuals at Risk of Occupational Exposure

Pre-exposure rabies prophylaxis (PrEP) is recommended for people at frequent or increased risk of professional exposure to lyssavirus (including rabies virus). PrEP provides protection against unrecognized exposure. After the primary vaccination, one's immune response against rabies may decline over time. We aimed to evaluate the immune response to rabies in individuals immunized for occupational reasons before and after a booster dose of the rabies vaccine. With this aim, we retrospectively documented factors associated with an inadequate response in individuals vaccinated for occupational purposes. Our findings analyzed data from 498 vaccinated individuals and found that 17.2% of participants had an inadequate antibody titration documented after their primary vaccination without the booster, while inadequate response after an additional booster of the vaccine was evidenced in 0.5% of tested participants. This study showed that a single booster dose of vaccine after PrEP conferred a high and long-term immune response in nearly all individuals except for rare, low responders. A systematic rabies booster after primary vaccination may result in alleviating the monitoring strategy of post-PrEP antibody titers among exposed professionals.

Immune response to rabies post-exposure prophylaxis in patients with non-HIV secondary immunodeficiencies

BACKGROUND

This study sought to determine the proportion of individuals with non-HIV secondary immunodeficiencies presenting inadequate antibody titers after rabies post-exposure prophylaxis (PEP) and to identify variables associated with inadequate response.

METHODS

A retrospective review of the records of immunocompromised patients having received a full course of PEP after a rabies exposure and having been tested for post-PPE antibody titers in two French Antirabies Clinics, between 2013 and 2018, was conducted. Antibody titers < 0.5 EU/ml (ELISA) were classified as inadequate.

RESULTS

A total of 28 individuals were included, 6 had inadequate post-PPE titers. None of the tested variable was independently associated with inadequate titers.

CONCLUSIONS

Inadequate response was unpredictable and not explained either by the characteristics of patients or by the PEP regimen they received. These findings support the WHO recommendation to systematically assess post-PEP response in immunocompromised patients to detect non-responders, who might require an additional dose.

Delivery of self-amplifying mRNA vaccines by cationic lipid nanoparticles: The impact of cationic lipid selection

Self-amplifying RNA (SAM) represents a versatile tool that can be used to develop potent vaccines, potentially able to elicit strong antigen-specific humoral and cellular-mediated immune responses to virtually any infectious disease. To protect the SAM from degradation and achieve efficient delivery, lipid nanoparticles (LNPs), particularly those based on ionizable amino-lipids, are commonly adopted. Herein, we compared commonly available cationic lipids, which have been broadly used in clinical investigations, as an alternative to ionizable lipids. To this end, a SAM vaccine encoding the rabies virus glycoprotein (RVG) was used. The cationic lipids investigated included 3ß-[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol), dimethyldioctadecylammonium (DDA), 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), 1,2-dimyristoyl-3-trimethylammonium-propane (DMTAP), 1,2-stearoyl-3-trimethylammonium-propane (DSTAP) and N-(4-carboxybenzyl)-N,N-dimethyl-2,3-bis(oleoyloxy)propan-1-aminium (DOBAQ). Whilst all cationic LNP (cLNP) formulations promoted high association with cells in vitro, those formulations containing the fusogenic lipid 1,2-dioleoyl-sn-3-phosphoethanolamine (DOPE) in combination with DOTAP or DDA were the most efficient at inducing antigen expression. Therefore, DOTAP and DDA formulations were selected for further in vivo studies and were compared to benchmark ionizable LNPs (iLNPs). Biodistribution studies revealed that DDA-cLNPs remained longer at the injection site compared to DOTAP-cLNPs and iLNPs when administered intramuscularly in mice. Both the cLNP formulations and the iLNPs induced strong humoral and cellular-mediated immune responses in mice that were not significantly different at a 1.5 µg SAM dose. In summary, cLNPs based on DOTAP and DDA are an efficient alternative to iLNPs to deliver SAM vaccines.

Investigating the Impact of Delivery System Design on the Efficacy of Self-Amplifying RNA Vaccines

messenger RNA (mRNA)-based vaccines combine the positive attributes of both live-attenuated and subunit vaccines. In order for these to be applied for clinical use, they require to be formulated with delivery systems. However, there are limited in vivo studies which compare different delivery platforms. Therefore, we have compared four different cationic platforms: (1) liposomes, (2) solid lipid nanoparticles (SLNs), (3) polymeric nanoparticles (NPs) and (4) emulsions, to deliver a self-amplifying mRNA (SAM) vaccine. All formulations contained either the non-ionizable cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or dimethyldioctadecylammonium bromide (DDA) and they were characterized in terms of physico-chemical attributes, in vitro transfection efficiency and in vivo vaccine potency. Our results showed that SAM encapsulating DOTAP polymeric nanoparticles, DOTAP liposomes and DDA liposomes induced the highest antigen expression in vitro and, from these, DOTAP polymeric nanoparticles were the most potent in triggering humoral and cellular immunity among candidates in vivo.

Optimization and validation of a blocking ELISA for quantitation of anti-rabies immunoglobulins in multispecies sera

We developed a fast, rabies virus-free, in vitro method, based on a blocking ELISA (bELISA), to detect and accurately quantify anti-rabies glycoprotein antibodies in serum of several animal species. In this method, purified rabies virus-like particles (VLPs) are used as antigen to coat the plates, while the presence of specific rabies immunoglobulins is revealed through blocking the recognition of these VLPs by a biotinylated monoclonal antibody. A quality by design approach was carried out in order to optimize the method performance, improving the sensitivity and, thereby, reducing the limit of detection of this assay. After the method validation, we confirmed that the bELISA method is able to detect a concentration of 0.06 IU/mL rabies immunoglobulins, titer lower than the 0.5 IU/mL cutoff value established as indication for correct vaccination. Further, we assessed the correlation between bELISA, the MNT, and the Platelia methods, confirming the accuracy of this new assay. On the other hand, precision was evaluated, obtaining acceptable repeatability and intermediate precision values, showing that this bELISA could be proposed as a potential alternative method, replacing the gold standard techniques in vaccination schemes and becoming a routine control technique within regional rabies surveillance programs.

Antibody Response Following Pre-Exposure Immunization Against Rabies in High-Risk Professionals

Vaccination against rabies and routine antibody testing of subjects participating in programs for the surveillance and control of rabies in animals is strongly recommended. The scope of this study is to describe the antibody level as measured by a commercial enzyme-linked immunosorbent assay (ELISA) after primary and booster intramuscular vaccination with a purified vero-cell rabies vaccine (PVRV) in high-risk professionals and to determine the influence of an array of factors on antibody level, that is, time elapsed since primary immunization series and booster dose, sex, age, pathologic conditions, high-risk occupation, and peak antibody level after initial scheme and booster dose. A primary series of three doses of PVRV was administered and a commercial ELISA was recommended 14 days postimmunization with continuous repetition at 6 months and yearly intervals for the laboratory personnel and the rest of the professionals, respectively. The protective antibody titer was defined as a minimum of 0.5 equivalent units/mL (EU/mL) (seroconvertion) and a booster dose was applied if the titer was determined nonprotective. The seroconversion rate (SCR) after primary vaccination was 100%, with a geometric mean titer (GMT) of 2.90 EU/mL (interquartile range [IQR]: 1.85-3.45). After booster vaccination due to nonprotective titer, the SCR was 100% and the GMT increased by 678% (95% confidence interval [CI]: 514-887) reaching 4.25 EU/mL (IQR: 4.00-4.60), 2.5 times higher than the GMT elicited by the primary vaccine scheme in the respective recipients. The titer dropped by 1.20% per month (95% CI: 0.52-1.89) regardless of booster administration or any other factor. Women had 51% higher titer compared with men (95% CI: 6-116). High-risk professionals should be verified for adequate antibody titers, but routine administration of a single booster dose of PVRV 1 year after the primary series could be considered; more evidence is needed to support the benefit in terms of immunity and logistics.

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

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

Rabies virus glycoprotein serology ELISA for measurement of neutralizing antibodies in sera of vaccinated human subjects

BACKGROUND

Vaccination provides protection against infection by inducing VNAs mainly against RABV surface GP. The measurement of VNAs to RABV is commonly used to assess the level of immunity in humans and animals after vaccination. A VNA titer of  ≥ 0.5 IU/mL of sera indicates adequate response to vaccination. Here, we report the development and validation of a RABV GP serology ELISA kit for semi-quantitative measurement of VNA titers in sera of vaccinated human subjects.

METHODS

Using a recombinant RABV GP expressed in mammalian cells as the capture antigen, the ELISA method was established using HuMAb NM57 reference initially and HRIG reference subsequently. The limit of detection (LOD), linear range, reproducibility, and precision of the method were examined. Specificity and sensitivity were established to assess the diagnostic accuracy.

RESULTS

RABV GP for ELISA plate coating and optimal dilution of human serum sample was 1 µg/mL and 1:20, respectively. Multiple assays were carried out by different technicians at different laboratories for assay standardization. Using the HRIG reference, the LOD was found to be 0.02-0.06 IU/mL and the linear range was 0.2-10.0 IU/ mL. The inter-assay CVs were in the range of 6.60-10.79%, indicating the reproducibility. None of the 12 known negative human sera, tested positive by ELISA, highlighting the specificity. A total of 415 unknown positive human sera were double-blind tested by the RFFIT and ELISA. The VNA titer cut-off value of ELISA was set at 1.5 IU/mL to ensure no false-positive. The diagnostic specificity and sensitivity were 100% and 91.1%, respectively.

CONCLUSIONS

The validation data characterize this ELISA as a suitable method for semi-quantitative measurement of VNA titers in human serum samples to assess vaccination status. The ELISA kit can offer simplicity, speed, low cost and high throughput, making it a practical tool for monitoring the immune response following vaccination.

Vaccine-associated rabies in red fox, Hungary

Rabies vaccine strain was isolated from a red fox (Vulpes vulpes) with signs of neurological disorder during an oral vaccination campaign in 2015, Hungary. The whole genome sequence of the isolated strain shared >99.9% nucleotide sequence identity to the whole genomes of vaccines strains recently used in Hungarian oral vaccination campaigns. The neuroinvasive potential of rabies vaccines that leads to development of clinical manifestations is rarely seen among wild animals; however, the observed residual pathogenicity needs awareness of field experts and requires close monitoring of rabies cases in areas where elimination programs are implemented.

Rabies: Current Preventive Strategies

Desensitization to rabies is a result of successfully eliminating canine rabies in the United States, which occurred in 2007; however, the need for mandatory rabies vaccination in pets remains. Rabies cases are rare in comparison with other vaccine-preventable diseases in companion animals; however, because it is a zoonotic disease with the highest case fatality rate of any infectious disease demands the establishment of strict laws for disease prevention. Preventive strategies include addressing current concerns in consideration of disease surveillance, appropriate vaccination recommendations, and local regulations protecting public health.

Utility of rabies neutralizing antibody detection in cerebrospinal fluid and serum for ante-mortem diagnosis of human rabies

Background

Early ante-mortem laboratory confirmation of human rabies is essential to aid patient management and institute public health measures. Few studies have highlighted the diagnostic value of antibody detection in CSF/serum in rabies, and its utility is usually undermined owing to the late seroconversion and short survival in infected patients. This study was undertaken to examine the ante-mortem diagnostic utility and prognostic value of antibody detection by rapid fluorescent focus inhibition test (RFFIT) in cerebrospinal fluid (CSF)/serum samples received from clinically suspected human rabies cases from January 2015 to December 2017.

Methodology/Principal findings

Samples collected ante-mortem and post-mortem from 130 and 6 patients with clinically suspected rabies respectively, were received in the laboratory during the study period. Ante-mortem laboratory confirmation was achieved in 55/130 (42.3%) cases. Real time PCR for detection of viral nucleic acid performed on saliva, nuchal skin, brain tissue and CSF samples could confirm the diagnosis in 15 (27.2%) of the 55 laboratory confirmed cases. Ante-mortem diagnosis could be achieved by RFFIT (in CSF and/or serum) in 45 (34.6%) of the 130 clinically suspected cases, accounting for 81.8% of the total 55 laboratory confirmed cases. The sensitivity of CSF RFFIT increased with the day of sample collection (post-onset of symptoms) and was found to be 100% after 12 days of illness. Patients who had received prior vaccination had an increased probability of a positive RFFIT and negative PCR result. Patients who were positive by RFFIT alone at initial diagnosis had longer survival (albeit with neurological sequelae) than patients who were positive by PCR alone or both RFFIT and PCR.

Conclusions/Significance

Detection of antibodies in the CSF/serum is a valuable ante-mortem diagnostic tool in human rabies, especially in patients who survive beyond a week. It was also found to have a limited role as a prognostic marker to predict outcomes in patients.

Ante-mortem diagnosis of human rabies is essential for patient management and public health measures. The detection of virus specific antibodies in the CSF/serum of patients with suspected rabies is thought to have a limited diagnostic role owing to late seroconversion and short survival in rabies. We examined the diagnostic and prognostic utility of antibody detection by rapid fluorescent focus inhibition test (RFFIT) in CSF/serum samples received from clinically suspected human rabies cases (2015–2017). RFFIT (in CSF and/or serum) could confirm ante-mortem diagnosis in 45 (34.6%) of the 130 clinically suspected cases, accounting for 81.8% of the total 55 laboratory confirmed cases. The sensitivity of CSF RFFIT increased with the day of sample collection (post-onset of symptoms) and was found to be 100% after 12 days of illness. Patients who had received prior vaccination had an increased likelihood of a positive RFFIT and negative PCR result. Patients who were positive by RFFIT alone at initial diagnosis had longer duration of survival, although with poor functional outcomes. Antibody detection by RFFIT in CSF/serum was found to have a diagnostic utility especially in patients who survived beyond a week and a limited prognostic role in human rabies.

Serological profiling of rabies antibodies by enzyme-linked immunosorbent assay and its comparative analysis with rapid fluorescent focus inhibition test in mouse model

Aim:

In this study, we have used enzyme-linked immunosorbent assay (ELISA) as an alternative test to replace the cumbersome rapid fluorescent focus inhibition test (RFFIT) to ascertain the immune status of immunized mice against rabies virus.

Materials and Methods:

Rabies is a devastating disease worldwide caused by rabies virus. Proper usage of pre- or post-exposure rabies vaccine can prevent the disease transmission. In this study, mice were immunized with Vero cell-adapted inactivated rabies vaccine. RFFIT was used as a test to determine the serum neutralizing titers in infected/vaccinated mice. Seroprofiling of mice sera was done in vitro by ELISA.

Results:

Twenty-one days post-immunization, both ELISA and RFFIT assays indicated similar antibody levels in mice sera that were immunized with Vero cell-adapted inactivated rabies vaccine. Both the tests were correlated, and the linearity was verified by the regression line (R²=0.979).

Conclusion:

In this study, we profiled the serological status of Vero cell-adapted inactivated rabies vaccine through ELISA in mice model that correlated well with the OIE gold standard test RFFIT.

An ELISA-based method for detection of rabies virus nucleoprotein-specific antibodies in human antemortem samples

Rabies is a fatal encephalitic disease in humans and animals caused by lyssaviruses, most commonly rabies virus (RABV). Human antemortem diagnosis of rabies is a complex process involving multiple sample types and tests for the detection of antibodies, antigen (protein), and nucleic acids (genomic RNA). Serological diagnosis of human rabies includes the detection of either neutralizing or binding antibodies in the cerebrospinal fluid (CSF) or serum samples from unimmunized individuals without prior rabies vaccination or passive immunization with purified immunoglobulins. While neutralizing antibodies are targeted against the surface-expressed glycoprotein (G protein), binding antibodies to viral antigens are predominantly against the nucleoprotein (N protein), although there can be antibodies against all RABV-expressed proteins. To determine N protein-specific antibody responses in the CSF and serum during RABV infection, we developed an enzyme-linked immunosorbent assay (ELISA) with purified recombinant N protein expressed in E. coli. N protein-specific immunoglobulin (Ig) subtypes IgG and IgM were detected in the CSF or serum of previously diagnosed human rabies cases. In addition, anti-N protein seroconversion was demonstrated over the course of illness in individual rabies cases. We compared the N protein ELISA results to those of an indirect fluorescent antibody (IFA) test, the current binding antibody assay used in diagnosis, and show that our ELISA is consistent with the IFA test. Sensitivity and specificity of the N protein ELISA ranged from 78.38-100% and 75.76-96.77% with respect to the IFA results. Our data provide evidence for the use of an N protein ELISA as an additional option for the detection of RABV-specific IgG or IgM antibodies in human CSF or serum specimens.

The shift in rabies epidemiology in France: time to adjust rabies post-exposure risk assessment

The epidemiology of rabies in France and western Europe has changed during the past 22 years. In France, rabies in non-flying terrestrial mammals was declared to be eliminated in 2001, and the risk of rabies is now limited to contact with bats, rabid animals illegally imported from rabies-enzootic countries and traveller exposure in enzootic areas. We analysed the epidemiology of rabies in France from 1995 to 2016, describing and analysing data on human rabies surveillance as well as data on post-exposure prophylaxis (PEP) collected from the network of French antirabies clinics. Over the study period, seven individuals were diagnosed with rabies in France, all of whom were infected outside mainland France. PEP data analysis revealed an expected overall decrease in PEP administration for individuals exposed in mainland France, but there was still overuse of anti-rabies drugs, given the very low epidemiological risk. On the other hand, a significant increase in PEP delivered to individuals exposed abroad was evidenced. These epidemiological trends indicate that clear guidelines should be provided to support physicians' efforts to adjust rabies risk assessment to the evolution of the epidemiological situation.

Rabies Virus Antibodies from Oral Vaccination as a Correlate of Protection against Lethal Infection in Wildlife

Both cell-mediated and humoral immune effectors are important in combating rabies infection, although the humoral response receives greater attention regarding rabies prevention. The principle of preventive vaccination has been adopted for strategies of oral rabies vaccination (ORV) of wildlife reservoir populations for decades to control circulation of rabies virus in free-ranging hosts. There remains much debate about the levels of rabies antibodies (and the assays to measure them) that confer resistance to rabies virus. In this paper, data from published literature and our own unpublished animal studies on the induction of rabies binding and neutralizing antibodies following oral immunization of animals with live attenuated or recombinant rabies vaccines, are examined as correlates of protection against lethal rabies infection in captive challenge settings. Analysis of our studies suggests that, though serum neutralization test results are expected to reflect in vivo protection, the blocking enzyme linked immunosorbent assay (ELISA) result at Day 28 was a better predictor of survival. ELISA kits may have an advantage of greater precision and ability to compare results among different studies and laboratories based on the inherent standardization of the kit format. This paper examines current knowledge and study findings to guide meaningful interpretation of serology results in oral baiting monitoring.

Sero-prevalence of virus neutralizing antibodies for rabies in different groups of dogs following vaccination

BACKGROUND

Mass vaccination of dogs is considered fundamental for national rabies control programmes in Sri Lanka, as dog is the main reservoir and transmitter of the disease.

METHODS

Dogs were followed to determine the sero-prevalence of antibodies to the rabies virus. Altogether 510 previously vaccinated and unvaccinated dogs with owners (domestic dogs) and dogs without owners (stray dogs) of the local guard dog breed in different age groups recruited from Kalutara District, Sri Lanka. The dogs were vaccinated with a monovalent inactivated vaccine intramuscularly and serum antibody titres on days 0, 30, 180 and 360 were determined by the Rapid Fluorescent Focus Inhibition Test (RFFIT).

RESULTS

The results indicated, a single dose of anti-rabies vaccination fails to generate a protective level of immunity (0.5 IU/ml) which lasts until 1 year in 40.42% of dogs without owners and 57.14% of previously unvaccinated juvenile (age: 3 months to 1 year) dogs with owners. More than one vaccination would help to maintain antibody titres above the protective level in the majority of dogs. The pattern of antibody titre development in annually vaccinated and irregularly vaccinated (not annual) adult dogs with owners is closely similar irrespective of regularity in vaccination. Previously vaccinated animals have higher (2 IU/ml) antibody titres to begin with and have a higher antibody titre on day 360 too. They show a very good antibody titre by day 180. Unvaccinated animals start with low antibody titre and return to low titres by day 360, but have a satisfactory antibody titre by day 180.

CONCLUSIONS

A single dose of anti-rabies vaccination is not sufficient for the maintenance of antibody titres for a period of 1 year in puppies, juvenile dogs with owners and in dogs without owners. Maternal antibodies do not provide adequate protection to puppies of previously vaccinated dams and puppies of previously unvaccinated dams. Immunity development after vaccination seems to be closely similar in both the groups of puppies.

The Recently Discovered Bokeloh Bat Lyssavirus: Insights Into Its Genetic Heterogeneity and Spatial Distribution in Europe and the Population Genetics of Its Primary Host

In 2010, a novel lyssavirus named Bokeloh bat lyssavirus (BBLV) was isolated from a Natterer's bat (Myotis nattereri) in Germany. Two further viruses were isolated in the same country and in France in recent years, all from the same bat species and all found in moribund or dead bats. Here we report the description and the full-length genome sequence of five additional BBLV isolates from Germany (n=4) and France (n=1). Interestingly, all of them were isolated from the Natterer's bat, except one from Germany, which was found in a common Pipistrelle bat (Pipistrellus pipistrellus), a widespread and abundant bat species in Europe. The latter represents the first case of transmission of BBLV to another bat species. Phylogenetic analysis clearly demonstrated the presence of two different lineages among this lyssavirus species: lineages A and B. The spatial distribution of these two lineages remains puzzling, as both of them comprised isolates from France and Germany; although clustering of isolates was observed on a regional scale, especially in Germany. Phylogenetic analysis based on the mitochondrial cytochrome b (CYTB) gene from positive Natterer's bat did not suggest a circulation of the respective BBLV sublineages in specific Natterer's bat subspecies, as all of them were shown to belong to the M. nattereri sensu stricto clade/subspecies and were closely related (German and French positive bats). At the bat host level, we demonstrated that the distribution of BBLV at the late stage of the disease seems large and massive, as viral RNA was detected in many different organs.

Public Health Responses to Reemergence of Animal Rabies, Taiwan, July 16-December 28, 2013

Taiwan had been free of indigenous human and animal rabies case since canine rabies was eliminated in 1961. In July 2013, rabies was confirmed among three wild ferret-badgers, prompting public health response to prevent human rabies cases. This descriptive study reports the immediate response to the reemergence of rabies in Taiwan. Response included enhanced surveillance for human rabies cases by testing stored cerebrospinal fluids (CSF) from patients with encephalitides of unknown cause by RT-PCR, prioritizing vaccine use for postexposure prophylaxis (PEP) during periods of vaccine shortage and subsequent expansion of PEP, surveillance of animal bites using information obtained from vaccine application, roll out of preexposure prophylaxis (PrEP) with vaccine stock restoration, surveillance for adverse events following immunization (AEFI), and ensuring surge capacity to respond to general public inquiries by phone and training for healthcare professionals. Enhanced surveillance for human rabies found no cases after testing 205 stored CSF specimens collected during January 2010-July 2013. During July 16 to December 28, 2013, we received 8,241 rabies PEP application; 6,634 (80.5%) were consistent with recommendations. Among the 6,501 persons who received at least one dose of rabies vaccine postexposure, 4,953 (76.2%) persons who were bitten by dogs; only 59 (0.9%) persons were bitten by ferret-badgers. During the study period, 6,247 persons received preexposure prophylaxis. There were 23 reports of AEFI; but no anaphylaxis, Guillain-Barré syndrome, or acute disseminated encephalomyelitis were found. During the study period, there were 40,312 calls to the Taiwan Centers for Disease Control hotline, of which, 8,692 (22%) were related to rabies. Recent identification of rabies among ferret-badgers in a previously rabies-free country prompted rapid response. To date, no human rabies has been identified. Continued multifaceted surveillance and interministerial collaboration are crucial to achieve the goal of rabies-free status in Taiwan.

Virology, immunology and pathology of human rabies during treatment

BACKGROUND

Rabies is an acute fatal encephalitis caused by all members of the Lyssavirus genus. The first human rabies survivor without benefit of prior vaccination was reported from Milwaukee in 2005. We report a second unvaccinated patient who showed early recovery from rabies and then died accidentally during convalescence, providing an unparalleled opportunity to examine the histopathology as well as immune and virological correlates of early recovery from human rabies.

METHODS

Case report, rapid fluorescent focus inhibition test, enzyme-linked immunosorbent assay, indirect and direct fluorescent antibody assays, reverse-transcriptase polymerase chain reaction, phylogenetic reconstruction, isolation in tissue culture, pathology and immunohistochemistry.

RESULTS

The 9 year old died 76 days after presenting with rabies of vampire bat phylogeny transmitted by cat bite. Antibody response in serum and cerebrospinal fluid was robust and associated with severe cerebral edema. No rabies virus was cultured at autopsy. Rabies virus antigen was atypical in size and distribution. Rabies virus genome was present in neocortex but absent in brainstem.

CONCLUSIONS

Clinical recovery was associated with detection of neutralizing antibody and clearance of infectious rabies virus in the central nervous system by 76 days but not clearance of detectable viral subcomponents such as nucleoprotein antigen or RNA in brain.

Laboratory diagnosis of human rabies: recent advances

Rabies, an acute progressive, fatal encephalomyelitis, transmitted most commonly through the bite of a rabid animal, is responsible for an estimated 61,000 human deaths worldwide. The true disease burden and public health impact due to rabies remain underestimated due to lack of sensitive laboratory diagnostic methods. Rapid diagnosis of rabies can help initiate prompt infection control and public health measures, obviate the need for unnecessary treatment/medical tests, and assist in timely administration of pre- or postexposure prophylactic vaccination to family members and medical staff. Antemortem diagnosis of human rabies provides an impetus for clinicians to attempt experimental therapeutic approaches in some patients, especially after the reported survival of a few cases of human rabies. Traditional methods for antemortem and postmortem rabies diagnosis have several limitations. Recent advances in technology have led to the improvement or development of several diagnostic assays which include methods for rabies viral antigen and antibody detection and assays for viral nucleic acid detection and identification of specific biomarkers. These assays which complement traditional methods have the potential to revolutionize rabies diagnosis in future.

Evaluation of a rabies ELISA as an alternative method to seroneutralisation tests in the context of international trade of domestic carnivores

For several years, international movements with pets have greatly increased. Most countries have relaxed their quarantine measures and adopted a scheme combining vaccination of pets against rabies followed by a serological test to check the efficacy of vaccination. This new scheme has been strongly supported by the OIE, WHO and the European Commission to facilitate the free movement of people and pets around the world. Currently, only two reference methods are recognised and prescribed (the FAVN test and the RFFIT) to measure rabies antibody levels in serum samples for international trade. They are reliable and valuable methods of assessing the efficacy of rabies vaccination but they are time-consuming and require well-trained people and specialised laboratory facilities. A few years ago, an ELISA (Platelia™ Rabies II kit ad usum Veterinarium) was developed for domestic carnivores and wildlife. To our knowledge, this ELISA is the only one certified and prescribed by the OIE. Following its marketing, one task of the EURL for rabies serology was to evaluate the performance of laboratories using this new kit. The results revealed that 26% of the participants, which were already approved laboratories for rabies serology, failed the inter-laboratory trial. Such unsatisfactory results have never been observed during any of the previous proficiency tests organised annually since 2000 by the EURL for rabies serology using reference methods. More investigations were undertaken through internal and collaborative studies to assess the performance of this newly marketed ELISA kit. The results of the internal study revealed that even with a specificity of 100%, the sensitivity evaluated on 593 samples of domestic carnivores came to 78.2%. An issue regarding the underestimation of serum titres was also revealed during the study. The results of a collaborative study involving 23 international laboratories reinforced the preliminary conclusions regarding lack of sensitivity. Indeed, only 5 laboratories out of the 23 obtained satisfactory results. We therefore suggest adopting a threshold of 0.3 EU/mL instead of 0.5 EU/mL to increase the sensitivity of the test.

Rabies Risk: Difficulties Encountered during Management of Grouped Cases of Bat Bites in 2 Isolated Villages in French Guiana

In French Guiana, from 1984 to 2011, 14 animal rabies cases and 1 human rabies case (2008) were diagnosed. In January 2011, vampire-bat attacks occurred in 2 isolated villages. In mid-January, a medical team from the Cayenne Centre for Anti-Rabies Treatment visited the sites to manage individuals potentially exposed to rabies and, in April, an anti-rabies vaccination campaign for dogs was conducted. Twenty individuals were bitten by bats in 1 month, most frequently on the feet. The median time to start management was 15 days. The complete Zagreb vaccination protocol (2 doses on day 0 and 1 dose on days 7 and 21) was administered to 16 patients, 12 also received specific immunoglobulins. The antibody titration was obtained for 12 patients (different from those who received immunoglobulins). The antibody titers were ≥0.5 EU/mL for all of them. The serology has not been implemented for the 12 patients who received immunoglobulins. Accidental destruction of a vampire-bat colony could be responsible for the attacks. The isolation and absence of sensitization of the populations were the main explanations for the management difficulties encountered. Sensitization programs should be conducted regularly.

Rabies is a disease almost invariably fatal in humans once the first clinical signs appear. In French Guiana bats represent the virus reservoir, especially vampire bats. From 1984 to 2011, 14 animal rabies cases and 1 human rabies case (2008) were diagnosed. In case of bat bite, anti-rabies immunoglobulins (RIG) and rabies vaccine must be rapidly administrated. The specific rabies management is exclusively performed by Centre for Anti-Rabies Treatment (CART), located at the Institut Pasteur in Cayenne, the prefecture of French Guiana, and 6 Anti-Rabies Treatment Outposts distributed along the coastal edge and along the two main rivers. Only a CART physician can administer RIG. In January 2011, vampire-bat attacks occurred in 2 isolated villages. In mid-January, a medical team from the CART visited the sites to manage individuals potentially exposed to rabies and, in April, an anti-rabies vaccination campaign for dogs was conducted. The most relevant contribution of this study is to underline difficulties to provide rabies post-exposure prophylaxis to remote populations exposed to bat rabies in the Amazonian region and to show the lack of awareness of these rural populations concerning rabies and the risk associated to vampire bats.

Biotechnology advances: a perspective on the diagnosis and research of Rabies Virus

Rabies is a widespread zoonotic disease responsible for approximately 55,000 human deaths/year. The direct fluorescent antibody test (DFAT) and the mouse inoculation test (MIT) used for rabies diagnosis, have high sensitivity and specificity, but are expensive and time-consuming. These disadvantages and the identification of new strains of the virus encourage the use of new techniques that are rapid, sensitive, specific and economical for the detection and research of the Rabies Virus (RABV). Real-time RT-PCR, phylogeographic analysis, proteomic assays and DNA recombinant technology have been used in research laboratories. Together, these techniques are effective on samples with low virus titers in the study of molecular epidemiology or in the identification of new disease markers, thus improving the performance of biological assays. In this context, modern advances in molecular technology are now beginning to complement more traditional approaches and promise to revolutionize the diagnosis of rabies. This brief review presents some of the recent molecular tools used for RABV analysis, with emphasis on rabies diagnosis and research.