Rabies Virus Neutralizing Antibody Research Articles

Humoral Immune Response of Thai Dogs after Oral Vaccination against Rabies with the SPBN GASGAS Vaccine Strain.

Applied research is crucial in pushing the boundaries and finding a solution to the age-old problem of dog-mediated rabies. Although oral vaccination of dogs is considered to have great potential in mass dog vaccination campaigns and could have far-reaching benefits, it is perhaps the most ignored of all available tools in efforts to eliminate dog-mediated rabies, not least because of limited data on immunogenicity, efficacy, and safety of potential oral rabies vaccine candidates. In this study, the long-term immunogenicity in local Thai dogs after oral administration of the highly attenuated 3rd generation rabies virus vaccine strain SPBN GASGAS was assessed. The oral rabies vaccine was administered to dogs by either direct oral administration (n = 10) or by offering a vaccine loaded intestine bait (n = 15). The humoral immune response was then compared to three groups of dogs; a group that received a parenteral delivered inactivated rabies vaccine (n = 10), a group offered a placebo intestine bait (n = 7), and a control group (n = 4) for an observation period of 365 days. There was no significant difference in the immune response of dogs that received oral and parenteral vaccine in terms of magnitude, kinetics, and persistence of both rabies virus (RABV) neutralizing (RFFIT) and binding (ELISA) antibodies. Although the single parenteral injection of an inactivated rabies vaccine mounted a slightly higher humoral immune response than the orally delivered live vaccine, RABV specific antibodies of both types were still detectable after one year in most animals for all treatment groups and resulted in no difference in seropositivity. Characterization of rabies specific antibodies revealed two main classes of antibodies involved in the immune response of dogs vaccinated. While IgM antibodies were the first to appear, the succeeding IgG response was mainly IgG2 dominated independent of the vaccine type used. The results support the view that SPBN GASGAS induces a sustained detectable immune response in local dogs both after direct oral administration and via bait application.

VIRUS NEUTRALIZING ANTIBODY FOLLOWING ORAL RABIES VACCINATION OF RACCOONS (PROCYON LOTOR ) ON SUBURBAN LONG ISLAND, NEW YORK, USA

Vaccine-laden baits were distributed to interrupt and halt raccoon (Procyon lotor) rabies transmission in suburban Nassau and Suffolk counties on Long Island, New York, US. Fishmeal polymer baits containing the RABORAL V-RG® vaccine were deployed with helicopters, bait stations, and vehicles at a target density of 250 baits/km2 during annual September campaigns (2006-10). Semiannual campaigns (500 baits/km2) were also initiated in a portion of the treatment zone (2007-09) in response to a persistent focus of rabid raccoons. The last enzootic case was reported in January 2009. The final vaccination campaign was completed in 2010. The raccoon variant of rabies virus is no longer circulating in Nassau or Suffolk counties. Significantly greater probabilities of raccoon seroconversion were observed in helicopter-deployed bait zones. The lowest probabilities of seroconversion were identified in vehicle and bait station-deployment bait zones, with a marginal advantage associated with bait-station deployment. Seroconversion was negatively associated with developed, medium-intensity areas and increasing human population density. Significantly higher rabies virus neutralizing antibody endpoint titrations were detected in helicopter and bait station-deployment zones.

Predicting the presence and titre of rabies virus-neutralizing antibodies from low-volume serum samples in low-containment facilities.

Serology is a core component of the surveillance and management of viral zoonoses. Virus neutralization tests are a gold standard serological diagnostic, but requirements for large volumes of serum and high biosafety containment can limit widespread use. Here, focusing on Rabies lyssavirus, a globally important zoonosis, we developed a pseudotype micro-neutralization rapid fluorescent focus inhibition test (pmRFFIT) that overcomes these limitations. Specifically, we adapted an existing micro-neutralization test to use a green fluorescent protein-tagged murine leukaemia virus pseudotype in lieu of pathogenic rabies virus, reducing the need for specialized reagents for antigen detection and enabling use in low-containment laboratories. We further used statistical models to generate rapid, quantitative predictions of the probability and titre of rabies virus-neutralizing antibodies from microscopic imaging of neutralization outcomes. Using 47 serum samples from domestic dogs with neutralizing antibody titres estimated using the fluorescent antibody virus neutralization test (FAVN), pmRFFIT showed moderate sensitivity (78.79%) and high specificity (84.62%). Despite small conflicts, titre predictions were correlated across tests repeated on different dates both for dog samples (r=0.93) and in a second data set of sera from wild common vampire bats (r=0.72, N=41), indicating repeatability. Our test uses a starting volume of 3.5 µl of serum, estimates titres from a single dilution of serum rather than requiring multiple dilutions and end point titration, and may be adapted to target neutralizing antibodies against alternative lyssavirus species. The pmRFFIT enables high-throughput detection of rabies virus-neutralizing antibodies in low-biocontainment settings and is suited to studies in wild or captive animals where large serum volumes cannot be obtained.

Factors influencing the immune response after a single-dose 3-visit pre-exposure rabies intradermal vaccination schedule: A retrospective multivariate analysis

BackgroundThe World Health Organization (WHO) recommends intradermal (ID) rabies vaccination as a safe and immunogenic alternative to intramuscular administration. The aim of this study is to determine which factors influence the levels of rabies virus neutralizing antibodies (RVNA) after a 3-visit ID rabies vaccination. MethodsThis is a retrospective secondary data analysis study based on electronic health record vaccination data of Belgian military subjects who received ID rabies Pre-exposure prophylaxis (PrEP) with a single-dose 3-visit regimen during the period 2014–2017. Logistic regression was performed to identify predictive factors of RVNA level ≥3.0 IU/mL and >10 IU/mL. ResultsThe second analysis performed on the 2025 subjects (100% seroconverted with a RVNA ≥ 0.5 IU/mL) shows a significantly better immune response in subjects younger than 30 years compared to all other age-groups, a gender-difference to predict RVNA ≥ 3.0 IU/mL (OR 2.30 [1.26–4.22] comparing “female” to “male”) and the influence of the vaccination schedule (OR 2.28 [1.15–4.53] comparing “late - very variable” to “correct” schedule) to predict > 10 IU/ml. Multivariate analysis also demonstrates that a postponed serology control significantly influences the Rapid Fluorescent Focus Inhibition Test (RFFIT). ConclusionGender and age significantly influence the response to ID rabies vaccine. Timing of RVNA determination is important to correctly assess the response to vaccination. A single-dose 3-visit ID rabies PrEP schedule is a dose-sparing effective alternative to the double-dose 2-visit ID schedule. When the minimum time interval between doses is respected, RVNA determination is not necessary.

Immunogenicity and safety of purified vero cell-cultured rabies vaccine under Zagreb 2-1-1 or 5-dose Essen regimen in the healthy Chinese subjects: a randomized, double-blind, positive controlled phase 3 clinical trial

ABSTRACT Aim: The aims of the study were to evaluate the non-inferiority of the safety and immunogenicity of a new trial purified vero cell-cultured rabies vaccine (trial vaccine) in healthy subjects comparing with the control purified vero cell-cultured rabies vaccine (control vaccine) following Essen regimen and to evaluate the non-inferiority of the safety and immunogenicity of the trial vaccine following two intramuscular regimens, between Zagreb and Essen regimen. Methods: Serum samples were collected before vaccination and on d 7, 14, 35/42 post vaccination. Adverse events (AEs) were recorded for 30 d following each vaccination. This study was registered in the Chinese Clinical Trial Registry (ChiCTR-PPR-15007057). Results: There was no significant difference in the incidence of AEs, local and systemic reactions, among Zagreb group, Essen group, and control group. But the incidence of solicited AEs was a significant difference among the three groups (p = 0.0498). The incidence of solicited AEs was higher in Essen group than that in control group and Zagreb group (p = 0.0278, p = 0.0248). In the subjects whose antibodies were seronegative before vaccination, the seroconversion rates of antibodies among three groups were all 100.0% on d 14 and d 35/42. The Essen group was not inferior to the control group, and the Zagreb group was not inferior to the Essen group on d 14. On d 14 and d 35/42, the geometric mean concentration of the three groups was much higher than the immune protection level of 0.5 IU/ml. Conclusions: The trial vaccine had good safety and immunogenicity, and the trial vaccine is not inferior to the control vaccine. Abbreviations: PVRV: purified vero cell-cultured rabies vaccine; AE: adverse event; CI: confidence interval; GMC: geometric mean concentration; IM: intramuscular; NIFDC: National Institutes for Food and Drug Control; PPS: per-protocol set; SS: safety set; REFIT: Rapid Fluorescent Focus Inhibition Test; RVNA: rabies virus neutralizing antibody; WHO: World Health Organization.

The Presence of Rabies Virus-Neutralizing Antibody in Wild Boars (Sus scrofa), a Non-Target Bait Vaccine Animal in Korea.

Oral vaccination with bait is an effective method to prevent rabies in wildlife, but non-target wild animals may also ingest the bait vaccine. In Korea, the target animal of the rabies bait vaccine is the raccoon dog (Nyctereutes procyonoides). Bait vaccines have been distributed in Korea for 20 years; although wild raccoon dogs have been tested for antibodies, rabies antibodies have never been investigated in non-target wild animals. Therefore, this study investigated rabies antibody formation in wild boars (Sus scrofa), which is likely the main competitor for the bait vaccine in Korea. In bait areas, 20 of 109 wild boars (18.3%) were seropositive, and 39 of 470 wild boars (8.3%) in non-bait areas were also seropositive. These results provide insights regarding bait uptake or vaccination in non-target wild boars.

Abortive vampire bat rabies infections in Peruvian peridomestic livestock.

Rabies virus infections normally cause universally lethal encephalitis across mammals. However, ‘abortive infections’ which are resolved prior to the onset of lethal disease have been described in bats and a variety of non-reservoir species. Here, we surveyed rabies virus neutralizing antibody titers in 332 unvaccinated livestock of 5 species from a vampire bat rabies endemic region of southern Peru where livestock are the main food source for bats. We detected rabies virus neutralizing antibody titers in 11, 5 and 3.6% of cows, goats and sheep respectively and seropositive animals did not die from rabies within two years after sampling. Seroprevalence was correlated with the number of local livestock rabies mortalities reported one year prior but also one year after sample collection. This suggests that serological status of livestock can indicate the past and future levels of rabies risk to non-reservoir hosts. To our knowledge, this is the first report of anti-rabies antibodies among goats and sheep, suggesting widespread abortive infections among livestock in vampire bat rabies endemic areas. Future research should resolve the within-host biology underlying clearance of rabies infections. Cost-effectiveness analyses are also needed to evaluate whether serological monitoring of livestock can be a viable complement to current monitoring of vampire bat rabies risk based on animal mortalities alone.

A Phase 3, Randomized, Open-label, Noninferiority Trial Evaluating Anti-Rabies Monoclonal Antibody Cocktail (TwinrabTM) Against Human Rabies Immunoglobulin (HRIG).

Limited supply, cost and potential for severe adverse effects observed with the blood derived rabies immunoglobulin products has led to search for alternative therapies. This issue has been addressed by developing an anti-rabies monoclonal antibody cocktail. This is a phase 3, randomized, open-label, noninferiority trial conducted in patients with World Health Organization (WHO) category III exposure with suspected rabid animal. Eligible patients were assigned to either the test arm, TwinrabTM (docaravimab and miromavimab) or the reference arm, human rabies immunoglobulin (HRIG; Imogam® Rabies-HT), in a ratio of 1:1. The primary endpoint was the comparison of responder rates between the 2 arms assessed as percentage of those with rabies virus neutralizing antibodies titers ≥0.5 IU/mL on day 14. A total of 308 patients were equally randomized into the 2 arms. In the per-protocol (PP) population, there were 90.21% responders in the TwinrabTM arm and 94.37% in the HRIG arm. The geometric mean of rapid fluorescent foci inhibition test titers in the PP on day 14 were 4.38 and 4.85 IU/mL, for the TwinrabTM and HRIG arms, respectively. There were no deaths or serious adverse events reported. This study confirmed that TwinrabTM is noninferior to HRIG in terms of providing an unbroken window of protection up to day 84. This trial in healthy adults with WHO category III exposure from suspected rabid animal also establishes the safety of TwinrabTM in patients with 1 WHO approved vaccine regimen (Essen). CTRI/2017/07/009038.

Immunogenicity and safety of two-visit, intradermal pre-exposure rabies prophylaxis simultaneously administrated with chimeric live-attenuated Japanese encephalitis vaccine in children living in rabies and Japanese encephalitis endemic country

BackgroundReducing the number of doses required for pre-exposure prophylaxis (PrEP) would make it more feasible and cost-effective to implement in children at the highest risk of rabies exposure in Asia. We studied immune response of 2-site intradermal (ID) injection of rabies vaccine on days 0 and 28 for rabies PrEP simultaneously administrated with live-attenuated Japanese encephalitis chimeric virus vaccine (JE-CV) for children living in endemic area. Research design and methodsSeronegative children (n = 49) aged 12–16 months were randomized 2:1 into two groups: Group A subjects were vaccinated with 0.1-mL ID injection of purified Vero cell rabies vaccine (PVRV), each at two sites on day (D) 0 and D28; Group B subjects were vaccinated with conventional 0.5-mL intramuscular PVRV on D0, D7 and D28. Both groups received one dose of JE-CV subcutaneously on D0 and D365. Rabies virus neutralizing antibody (RVNA) titers were measured on D0, D42 and D365 after vaccination; Japanese Encephalitis (JE) neutralizing antibody titers were determined on D0, D42, D365 and D379. ResultsAll children had RVNA ≥ 0.5 IU/mL on D42 (geometric mean titers [GMTs] of RVNA 14.35 IU/mL [Group A] and 14.83 IU/mL [Group B], p > 0.05]). On D365, RVNA GMTs of subjects in group A and B were 1.50 IU/mL and 2.00 IU/mL (p > 0.05), respectively. All children had seroprotection following booster dose of JE-CV. There were no vaccine-related SAEs observed. ConclusionThe 2-site ID PrEP with PVRV on days 0 and 28 co-administrated with JE-CV are safe and immunogenic.

Meta-analysis of immunogenicity and safety of human rabies vaccination under Zagreb and Essen regimens.

Aim: To assess the immunogenicity and safety of rabies vaccination under the Zagreb and Essen regimens by performing a meta-analysis. Methods: Electronic databases were searched for eligible studies. Risk ratios and weighted mean differences with 95% CIs were used to calculate estimates. Results:A total of18 studies were included. Rabies virus neutralizing antibody concentration was comparable between the two regimens at D7 and 14. No significant differences were observed in seroconversion rates from D14 and 42. Incidence of fever was higher in Zagreb group (risk ratio: 1.55 [1.37-1.76]); but no significant differences were present for other common adverse events. Conclusion: Rabies vaccination under the Zagreb regimen was noninferior to the Essen regimen in immunogenicity and had an acceptable safety profile.

Testing of Ferarabivac anti-rabies live vaccine for wild carnivores for its immunogenicity and protectivity

Rabies is one of the most important human and animal viral diseases, being one of the most dangerous zoonoses, causing damage to the central nervous system with an inevitable fatal outcome. This disease is of global concern, and it attracts special attention of international organizations (WHO, OIE, FAO, GARC) and of veterinary services in many countries around the world. A variety of anti-rabies vaccines have been used for specific rabies prevention in wild carnivores, however, the safety and effectiveness of some of them is doubtful. New, more advanced products are being developed, one of which is Ferarabivac, a live oral vaccine. The vaccine was tested for its immunogenicity and protectivity in wild carnivores. The optimal immunizing dose was 2.0 cm3, with the infectivity titre of RV-97 strain of at least 6.00 lg KKID50/cm3. Anti-rabies antibody titres detected in the blood sera of foxes and raccoon dogs 14 days post vaccination, were 0.70 ± 0.18 and 0.73 ± 0.19 IU/cm3, respectively, which provided protection against rabies virus infection (≥ 0.50 IU/cm3). Rabies virus neutralizing antibodies in foxes reached their maximum level of 4.30 ± 0.32 IU/cm3 50 days post vaccination. Antibody titres in vaccinated raccoon dogs also reached their maximum level of 4.53 ± 0.27 IU/cm3 50 days post vaccination. The minimum protective threshold levels of serum neutralizing antibodies was determined 12 months after the vaccination, and it was 0.62 ± 0.28 and 0.71 ± 0.17 IU/cm3 in foxes and raccoon dogs, respectively, which proves the necessity to perform booster vaccination one year later. No animals vaccinated against rabies with Ferarabivac live vaccine showed any clinical signs of the disease during the entire observation period following the challenge test carried out 30 days post vaccination.

Studies on humoral immunity in dogs after use of rabies inactivated vaccines formulated with Montanide ISA 70 VG and GEL 01 adjuvants

Despite all the efforts made, the issue of rabies in the world does not lose its relevance. As an acute endemic infection, it poses a considerable danger to both animals and humans. The leading role in the transmission of rabies to humans belongs to diseased dogs; stray animals can be potential sources of rabies agent, which increases the risk of transmitting a deadly virus to humans. Rabies prevention in dogs around the world is carried out by counting the number of these animals, their mandatory routine immunization and evaluating the effectiveness of vaccination against the accumulation of rabies virus-neutralizing antibodies. Inactivated vaccines based on different viral strains formulated with a wide range of adjuvants are used to induce a protective level of humoral immunity against rabies in dogs (≥ 0.5 IU/cm3), which allows vaccines with high safety and effectiveness for the target animal species to be obtained. The article presents the results of the study of humoral immunity in 20 non-pedigree dogs 21 days after the administration of rabies inactivated vaccines based on culture rabies virus from ARRIAH strain formulated with various adjuvants. The presented rabies vaccines formulated with oil adjuvant Montanide ISA 70 VG and gel adjuvant Montanide GEL 01 were innocuous and safe and induced strong immunity in all vaccinated animals. The vaccine formulated with Montanide ISA 70 VG adjuvant in case of a single administration in the dose of 1.0 cm3 induces formation of rabies virus-neutralizing antibodies in the level of 2.4 times higher than the vaccine formulated with Montanide GEL 01 adjuvant. The highest levels of rabies antibodies in dogs were 48.1 ± 3.7 and 28.3 ± 1.5 IU/cm3 and were observed with the use of rabies inactivated emulsion vaccine in the doses of 3.0 and 1.0 cm3 respectively.

Purified Vero Cell Rabies Vaccine (PVRV, Verorab®): A Systematic Review of Intradermal Use Between 1985 and 2019.

The purified Vero cell rabies vaccine (PVRV; Verorab®, Sanofi Pasteur) has been used in rabies prevention since 1985. Evolving rabies vaccination trends, including shorter intradermal (ID) regimens with reduced volume, along with WHO recommendation for ID administration has driven recent ID PVRV regimen assessments. Thus, a consolidated review comparing immunogenicity of PVRV ID regimens during pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) is timely and beneficial in identifying gaps in current research. A search of seven databases for studies published from 1985 to November 2019 identified 35 studies. PrEP was assessed in 10 studies (n = 926) with 1–3-site, 1–3-visit regimens of up to 3-months duration. Seroconversion (rabies virus neutralizing antibodies [RVNA] ≥ 0.5 IU/mL) rates of 90–100% were reported within weeks, irrespective of regimen, with robust booster responses at 1 year (100% seroconversion rates by day 14 post-booster). However, data are lacking for the current WHO-recommended, 2-site, 1-week ID PrEP regimen. PEP was assessed in 25 studies (n = 2136) across regimens of 1-week to 90-day duration. All ID PEP regimens assessed induced ≥ 99% seroconversion rates (except in HIV participants) by day 14–28. This review confirms ID PVRV suitability for rabies prophylaxis and highlights the heterogeneity of use in the field.

The Serological Prevalence of Rabies Virus-Neutralizing Antibodies in the Bat Population on the Caribbean Island of Trinidad.

Rabies virus (RABV) is the only lyssavirus known to be present within the Caribbean. The island of Trinidad, is richly diverse in chiropteran fauna and endemic for bat-transmitted rabies with low RABV isolation rates observed in this population. We aimed to determine the seroprevalence of rabies virus neutralizing antibodies (RVNA) in light of spatio-temporal and bat demographic factors to infer the extent of natural exposure to RABV in the Trinidadian bat population. RVNA titers were determined by the RABV micro-neutralization test on 383 bat samples representing 21 species, comprising 30.9% of local bat diversity, from 31 locations across the island over 5 years. RVNA was positively detected in 33 samples (8.6%) representing 6 bat species (mainly frugivorous) with titers ranging from 0.1 to 19 IU/mL (mean 1.66 IU/mL). The analyses based on a multivariable binomial generalised linear mixed-effects model showed that bat age and year of capture were significant predictors of seropositivity. Thus, juvenile bats were more likely to be seropositive when compared to adults (estimate 1.13; p = 0.04) which may suggest early exposure to the RABV with possible implications for viral amplification in this population. Temporal variation in rabies seropositivity, 2012–2014 versus 2015–2017 (estimate 1.07; p = 0.03) may have been related to the prevailing rabies epizootic situation. Regarding other factors investigated, RVNA was found in bats from both rural and non-rural areas, as well as in both hematophagous and non-hematophagous bat species. The most common seropositive species, Artibeus jamaicensis planirostris is ubiquitous throughout the island which may potentially facilitate human exposure. The findings of this study should be factored into public health assessments on the potential for rabies transmission by non-hematophagous bats in Trinidad.

Novel strategy for expression and characterization of rabies virus glycoprotein

Rabies is a fatal zoonosis which could affect all mammals. Glycoprotein (G protein) from the rabies virus plays an important role in the binding of virus to target cells. However, expression of the G protein with native conformation has been a great challenge for many years. In this study, we solved this problem by replacing the original signal peptide of rabies virus G protein with the one from the heavy chain of human IgG. The expression levels of recombinant G protein dramatically increased from a few μg/L to 50 mg/L in the culture supernatants. The identity of the recombinant G protein was confirmed by western blotting using both 6XHis mAb 6E2 and rabies G protein mAb 7G3. The correct conformation of the recombinant G protein was shown by using rabies virus neutralizing antibodies. In addition, the recombinant G protein had immune-reactivities with mice sera raised against rabies vaccines and vice versa. Taken together, our data suggested that by replacing the signal peptide, the expression level of the G protein with native conformation could be significantly improved. This would help the development of a rabies subunit vaccine, structural studies of rabies G protein, elucidation of the signal pathway of RABV infection.

Analysis of determination of rabies virus neutralizing antibody titres in the sera of vaccinated humans.

Rabies is an infectious disease that is always fatal following the onset of clinical symptoms. The only way to prevent the cases of rabies in humans is timely carried out the rabies post-exposure prophylaxis in accordance with the recommended schedule. The aim of the study was to characterize the level of immune response in persons that received a post-exposure prophylaxis against rabies, to consider the role of the factors of the formation immune responses to rabies vaccines. In the laboratory of viral vaccines of the Scientific Centre for Expert Evaluation of Medicinal Products, the 48 sera of patients that received the post-exposure prophylaxis of rabies after wounds from a rabid or suspected rabid animal has been studied. The titer of virus neutralizing antibodies (VNA) to the rabies virus in the sera of the vaccinated not less than 1:64 (corresponding to a level of VNA at least 0,5 IU /ml) in the mouse neutralization test indicates the effective vaccination. Our data confirm the absence of statistically significant differences in the level of VNA in the vaccinated persons that received a complete and incomplete (5 doses) course of post-exposure vaccination against rabies. Depending on the level of VNA, all patients are divided into groups with conditionally low, medium and high content of antibodies in sera. It has been shown that in most cases properly administered vaccination contributed to the formation of effective immune response. The lack of a protective level of BHA requires additional administration of the vaccine and analysis of the factors that influenced the ineffectiveness of vaccination. In some patients the determination of rabies virus neutralizing antibody titres is necessary.

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

BackgroundDomestic 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 findingsThe 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/SignificanceSince 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.

Rabies surveillance in wild mammals in South of Brazil.

The sylvatic cycle of rabies, caused by the Rabies lyssavirus (RABV), is maintained in the American Continent by aerial and terrestrial wild mammals. In this study, we combined passive surveillance of rescued wild animals with active serological surveillance in targeting areas at Rio Grande do Sul State and Santa Catarina State, south of Brazil, where bites of humans by wild animals have been reported. Circulation of RABV in Brazilian bats has been extensively demonstrated; however, the observation of such infections in unvaccinated terrestrial mammals is restricted to some regions of the Brazilian territory. The occurrence of rabies infection in unvaccinated animals has been identified by the detection of RABV antigens in brain tissues of dead animals or anti-rabies antibodies in live animals. Such strategies allow the surveillance of rabies and the assessment of spillover risks from infected animals to humans. Our aim included the identification of species of wild mammals that are involved in the sylvatic cycle of rabies virus in Southern Brazil and to assess the risk of rabies infection in patients bitten by wild animals in the state. To assess the anti-rabies seropositivity, sera were submitted to the Rapid Fluorescent Focus Inhibition Test (RFFIT). Among the 100 mammals tested, five animals were seropositive (5%) including three (one primate and two wild canids) with rabies virus neutralizing antibodies titres >0.5IU/ml. Our results highlight the exposure to RABV of both primates and wild canids in Southern Brazil and suggest the occurrence of RABV exposure without the development of further symptoms. Further research should clarify the dynamics of rabies in wild canids and whether primates are accidental hosts or reservoirs for RABV at this region.

Immunogenicity of Ontario Rabies Vaccine for Small Indian Mongooses (Herpestes auropunctatus)

Oral rabies vaccination is the principal strategy used to control rabies in wildlife. No oral rabies vaccine is licensed for small Indian mongooses (Herpestes auropunctatus). The Ontario Rabies Vaccine Bait (ONRAB) is a human adenovirus type-5 rabies glycoprotein recombinant vaccine licensed for rabies control in striped skunks (Mephitis mephitis) in Canada and is under experimental evaluation in the US. We evaluated varying doses of ONRAB vaccine by direct instillation into the oral cavity with three groups of 10 mongooses: Group 1 received 109.5 TCID50, group 2 received 108.8 TCID50, and group 3 received 108.5 TCID50 of vaccine. Six control mongooses were sham-vaccinated with culture media. We collected a serum sample prior to vaccination and on days 14 and 30 postvaccination (PV). We quantified the level of rabies virus neutralizing antibodies (RVNA) from mongoose sera and compared titers among vaccinated groups and time points PV, where values greater than or equal to 0.1 IU/mL were considered positive. On day 14 PV, 87% (26 of 30, 95% confidence interval 70-95%) of vaccinates had seroconverted, whereas all vaccinates demonstrated RVNA by day 30 PV. There was a marginal effect of vaccine dose on group means of log-transformed RVNA titers at day 14 PV (F=2.5, P=0.099), but not day 30 PV. Sham-vaccinated animals were seronegative during all time points.

Artesunate enhances the immune response of rabies vaccine as an adjuvant

Rabies is an ancient zoonosis that continues to be an important health problem worldwide. Vaccination with rabies vaccine is the most important strategy to prevent rabies. Adjuvants contribute to the immune response of viral vaccine. The aim of this study was to investigate whether artemisinin derivatives artesunate and dihydroartemisinin could enhance the immunogenicity of inactivated rabies virus in mice. Administration of artesunate or dihydroartemisinin by intramuscular injection at a dose of 5 mg/kg did not cause body weight loss and unusual symptoms in mice. Mice were immunized with inactivated CVS-11 or inactivated rHEP-dG together with either artesunate or dihydroartemisinin through intramuscular injection. Blood samples were collected to investigate the virus-neutralizing antibody (VNA) titers, and challenge assays were then conducted. The results showed that the rabies VNA titers in mice co-treated with artesunate rather than dihydroartemisinin were significantly higher than in the control animals treated with the phosphate buffered saline (PBS). In addition, mice co-treated with artesunate survived from lethal rabies virus challenge compared with those treated with PBS. In contrast, co-treatment with dihydroartemisinin did not improve the survival rate of the challenged mice. The findings indicate that artesunate could be used as a new candidate adjuvant for rabies vaccination.