Rabies Virus Neutralizing Antibody Titers Research Articles

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.

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.

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.

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.

Safety and efficacy results of simulated post-exposure prophylaxis with human immune globulin (HRIG; KEDRAB) co-administered with active vaccine in healthy subjects: a comparative phase 2/3 trial

ABSTRACTWe conducted a clinical trial to assess the safety and putative efficacy of an additional human rabies immune globulin (HRIG; KEDRAB) versus an older product (Comparator, HyperRAB S/D® [Grifols]) and determine whether HRIG interferes with development of endogenous antibodies versus Comparator, when each is given with an active rabies vaccine. This was a prospective, double-blind, single-period, non-inferiority study in which subjects were randomized (1:1) to a single dose (20 IU/kg) of HRIG or Comparator on day 0 and rabies vaccine (RabAvert® [GlaxoSmithKline]; 1 mL of ≥2.5 IU/mL) on days 0, 3, 7, 14, and 28. Anti-rabies antibodies were measured by rapid fluorescent focus inhibition test on day 14, and subjects were followed until day 185. Rabies virus neutralizing antibody (RVNA) titers ≥0.5 IU/mL were considered seroconversion putatively indicative of protection. The non-inferiority criterion was the lower limit of the 90% confidence interval (CI) >–10%, for the between-group difference in the proportion of subjects achieving RVNA ≥0.5 IU/mL. On day 14, 98.3% of 59 subjects in the HRIG group and 100% of 59 in the Comparator group had RVNA ≥0.5 IU/mL (difference between proportions – 1.8%; 90% CI, – 8.2, 3.1; non-inferiority criterion met). One subject in the HRIG group did not meet the seroconversion criteria for anti-rabies antibody, and one subject in the Comparator group showed an anamnestic response, with much higher than expected anti-rabies antibody levels at both baseline and on day 14. Thus, HRIG allows for prophylactic anti-rabies antibody titers and is non-inferior to Comparator, when administered with rabies vaccine.

A randomized open-label trial of 2-dose or 3-dose pre-exposure rabies prophylaxis among Thai children

BackgroundWorld Health Organization changed the recommendation for pre-exposure rabies prophylaxis from 3-dose to 2-dose regimen in 2018. Given limited data of 2-dose regimens in pediatric population, this study aimed to compare the immunogenicity between 2-dose and 3-dose pre-exposure rabies immunization. MethodsThis study was conducted among healthy children aged 2–12 years. They were randomized to 2-dose vaccination (2D) on days 0 and 28 or 3-dose vaccination (3D) on days 0, 7, and 28. Purified Vero cell rabies vaccine (PVRV-Verorab™) was administered intramuscularly. Rabies virus neutralizing antibody (RVNA) titers were measured at 3 time points: 14-day after complete vaccination, 1-year pre-booster vaccination, and 7-day post-booster dose to mimic scenario of rabies exposure. RVNA titers ≥0.5 IU/ml were considered adequate antibody. T cell specific response to rabies vaccine antigen was measured using the interferon-gamma enzyme linked immunospot assay. ResultsFrom September to October 2017, 107 participants (51% males), 78 in 2D group and 29 in 3D group were enrolled. Median age was 5.8 years (IQR 4.4–7.3). All participants had RVNA titers ≥0.5 IU/ml after primary vaccination [GMT 2D: 18.6 (95%CI 15.9–21.8) and 3D: 16.3 (95%CI 13.2–20.1 IU/ml), p = 0.35]. At 1-year prior to receiving the booster, only 80% of the children in 2D group maintained RVNA titers ≥0.5 IU/ml compared to 100% of the children in 3D group (p = 0.01). However, all participants in both groups had RVNA ≥0.5 IU/ml at 7-day post booster vaccination [GMT 2D: 20.9 (95%CI 17.4–25.3) and 3D: 22.2 (95%CI 15.8–31.4) IU/ml (P = 0.75)]. The median number of IFN-γ secreting cells at 7-day post-booster dose was 98 and 128 SFCs per 106 PBMCs in the 2D and 3D groups, respectively (P = 0.30). ConclusionsTwo-dose primary rabies immunization provided adequate antibody at post primary vaccination and post booster. The results support 2-dose regimen of pre-exposure rabies immunization in the pediatric population.

A new recombinant rabies virus expressing a green fluorescent protein: A novel and fast approach to quantify virus neutralizing antibodies

The Rapid Fluorescent Focus Inhibition Test (RFFIT) is a standard assay used to detect and assess the titers of rabies virus neutralizing antibodies (RVNA) in blood sera. To simplify the multistep RFFIT procedure by eliminating the immunostaining step, we generated a new recombinant RV expressing a green fluorescent protein (rRV-GFP) and assess its suitability for quantifying RVNA. We rescued the rRV-GFP virus from plasmid DNA carrying a full-length genome of the CVS-N2c strain of RV in which the eGFP gene was inserted between the glycoprotein and RNA-polymerase genes. The recombinant virus was genetically stable and grew efficiently in appropriate cells expressing sufficient GFP fluorescence to detect directly 20 h post infection (hpi). We evaluated the feasibility of using rRV-GFP in RFFIT by comparing RVNA titers in 27 serum samples measured by conventional RFFIT and RFFIT-GFP. A linear regression analysis of the data demonstrated a good agreement between these two methods (r = 0.9776) including results with samples having RVNA titers close to the minimally acceptable vaccine potency threshold (0.5 IU/ml).Study results showed that the rRV-GFP virus could replace the CVS-11 challenge virus currently used in the conventional RFFIT and enabling more rapid, simpler, and less expensive detection and quantitation of RVNA.

Intradermal post-exposure rabies vaccination with purified Vero cell rabies vaccine: Comparison of a one-week, 4-site regimen versus updated Thai Red Cross regimen in a randomized non-inferiority trial in the Philippines

BackgroundRabies post-exposure prophylaxis (PEP) via intradermal (ID) administration is standard practice in Asia. Accumulating evidence suggests that PEP shortened to 3 visits in one week does not adversely affect seroconversion rates or immune memory. ObjectiveTo determine whether the seroconversion rate at Day14 with a 1-week, 4-site (4-4-4-0-0) ID vaccination regimen with or without rabies immunoglobulin (RIG) was non-inferior to the updated Thai Red Cross (TRC) 28-day, 2-site (2-2-2-0-2) ID regimen with RIG during rabies PEP. We also assessed one-year antibody persistence. MethodsThis phase III, mono-center, open-label, randomized-controlled trial assigned participants aged ≤50 years (n = 600) exposed to suspected rabid animals and sustaining WHO Category II injuries (automatic allocation to G1) or Category III injuries (randomized to G2 or G3) to the following groups (1:1:1 ratio): G1 (n = 200), 1-week 4-site ID regimen with the purified Vero cell rabies vaccine (PVRV; Verorab®) without RIG; G2 (n = 201), 1-week 4-site ID regimen with PVRV, and purified equine rabies immunoglobulin (pERIG); G3 (n = 199), TRC 28-day, 2-site ID regimen with PVRV, and pERIG. Non-inferiority tests compared G1 vs. G3 and G2 vs. G3. Seroconversion rate was the proportion (%) of vaccinees with rabies virus neutralizing antibodies (RVNA) titers ≥0.5 IU/mL measured by rapid fluorescent focus inhibition test. ResultsOn Day14, after the third vaccine administration, seroconversion rates were non-inferior in both comparisons and were, respectively, 100%, 99.4%, 98.8% in G1, G2, G3 with a decrease to 97.6%, 89%, 79.8% at Year 1. At Day14, RVNA geometric mean titers were 11.3 IU/mL; 9.89 IU/mL; 6.15 IU/mL, respectively, decreasing to 2.96 IU/mL, 1.37 IU/mL, 0.97 IU/mL at Year1. Safety and tolerability were similar between the three groups. ConclusionThe seroconversion rate at Day 14 with the 1-week 4-site ID regimen, both with and without pERIG, was non-inferior to the reference TRC 28-day 2-site ID regimen with pERIG during rabies PEP with PVRV.ClinicalTrials.gov ID: NCT01622062.

2279. A Randomized Open-Label Trial of 2-Dose or 3-Dose Primary Rabies Immunization Among Thai Children

BackgroundThe World Health Organization (WHO) recently recommended 2-dose primary rabies immunization instead of the 3-dose standard regimen. Given limited data of 2-dose regimens in pediatric population, this study was conducted. The objective was to compare the immunogenicity between 2-dose and 3-dose primary rabies immunization.MethodsThis study was an open-label clinical trial. Inclusion criteria were children aged 2–12 years with rabies virus neutralizing antibody (RVNA) titers < 0.5 IU/ml at baseline. The participants were divided into 2-dose vaccination (2D) on days 0 and 28 and 3-dose vaccination (3D) on days 0, 7, and 28 with a 2:1 ratio. A dose of 0.5 ml purified vero cell rabies vaccine (PVRV) was administered intramuscularly. RVNA titers were measured at 14-day post primary immunization. RVNA titers ≥ 0.5 IU/ml were considered seroprotective against rabies. Geometric mean titers (GMT) were calculated. T cell specific response to rabies vaccine antigen were measured from peripheral blood mononuclear cells (PBMCs) using the interferon-gamma enzyme-linked immunospot (IFN-gamma ELISpot) assay.ResultsFrom September to October 2017, 105 participants (52% male), 76 in 2D group and 29 in 3D group were enrolled. Median age and body weight was 70 months (IQR 53–88) and 19.2 kilograms (IQR 15.9–24.3), respectively. All participants had seroprotection at 14-day post primary immunization with GMT of 18.6 (95% CI 15.8-21.9) and 16.3 (95% CI 13.1–20.0) in 2D and 3D groups, respectively (P = 0.35). Median IFN-gamma level at 14-day post primary immunization was 60 spot forming cells (SFC) per 106PBMCs and 132 SFC per 106PBMCs in the 2D and 3D groups, respectively (P = 0.15).ConclusionThe immunogenicity of 2-dose primary rabies immunization at 14-day post primary vaccination is comparable to the 3-dose regimen. Participants are currently being followed for 1-year results.Disclosures All authors: No reported disclosures.

Clinical evaluation of purified chick embryo cell rabies vaccine administered intradermally in animal exposures

Background: In India, presently there are two purified chick embryo cell culture vaccines (PCECV) viz., Rabipur (Flury LEP strain) and Vaxirab – N (Pitman Moore strain) which are commonly used both in public as well as private sectors. The present study was conducted to assess the clinical efficacy in terms of safety, immunogenicity and survival status of both the PCECV administered animal exposures taking complete PEP at the anti-rabies clinic.Methods: A longitudinal study was conducted at the anti-rabies clinic, Kempegowda Institute of Medical Sciences (KIMS), Bangalore, India. 86 suspect rabid dog bite cases attending clinic were enrolled and followed up for 1year. All the animal bite cases were given post exposure prophylaxis of full course of PCECV i.e. Rabipur or Vaxirab - N as per schedule intradermally using updated Thai Red Cross regimen. The rabies virus neutralizing antibody (RVNA) concentrations on days 14, 28, 90, and 180 were tested by modified rapid fluores­cent focus inhibition test.Results: Out of 86 study subjects, 43 subjects received Rabipur and another 43 subjects received Vaxirab –N vaccines. The incidence of adverse drug events (ADEs) was found to be 9.3%. All subjects had protective RVNA titers of ³0.5 IU/ml from day 14 till day 180. All the study subjects were healthy and alive after 6 months of completing PEP.Conclusions: The currently available purified chick embryo cell culture rabies vaccines are safe, immunogenic and clinically effective for post exposure prophylaxis in animal bite cases, which will help in eliminating human rabies by 2020.

Adjuvant activity of ethanol extract of Hippophae rhamnoides leaves with inactivated rabies virus antigen

Context: Hippophae rhamnoides L. (Elaeagnaceae), commonly known as seabuckthorn (SBT), is known for its medicinal and nutritional properties.Objective: Evaluation of in vivo adjuvant activity of SBT leaf extract (SBTE) with inactivated rabies virus antigen (Rb).Materials and methods: Swiss albino mice were immunized with aqueous-alcoholic SBTE (100 mg/kg body weight) or algel (aluminium hydroxide gel) with or without Rb (5% v/v). After priming, booster was administered on day 14. Rabies virus neutralizing antibody (RVNA) titers were estimated by rapid fluorescent focus inhibition test in sera samples collected on days 7, 14, 21, 28 and 35. Effect of adjuvant administration on cytotoxic T lymphocytes (CTLs), memory T cells, plasma and CD11c+ cells was studied by flow cytometry. In vitro hemolysis was assayed in human RBC.Results: RVNA titers were significantly enhanced (p < 0.05) after booster administration in mice immunized with SBTE + Rb as compared to the controls. In combination, SBTE, algel and Rb, enhanced the RVNA titers. CTLs significantly increased (p < 0.05) in SBTE + Rb immunized mice. Memory T cells and plasma cells were 27.9 and 15.9%, respectively, in SBTE + Rb immunized mice as compared to that of 20.3 and 11.3%, respectively, in Rb immunized group. SBTE + Rb enhanced peritoneal CD11c+ cells (25.8%) as compared to 9.4% cells in Rb immunized mice, showed 3.2-fold increment in LPS induced IL-1β. No RBC hemolysis was observed with SBTE.Conclusions: This study demonstrates the potential adjuvant activity of SBTE with Rb by increasing RVNA titers and CTL response.

Immunogenic response in obese patients undergoing rabies post-exposure prophylaxis with combined equine rabies immunoglobulin and rabies vaccination

BackgroundObesity is a risk factor for increased morbidity and mortality associated with many vaccine preventable infectious diseases such as influenza. Moreover, higher volume of passive rabies immunoglobulin (RIG) due to weight based dosing might suppress vaccine-induced immune responses in obese patients. This study aimed to evaluate the effect of obesity on humoral immune responses to combined equine RIG and rabies vaccine treatment among patients with WHO category III exposure to a rabies suspected animal. MethodsA single centre, prospective, open-labelled study among WHO category III rabies exposed patients was conducted to compare serum rabies virus neutralizing antibody (RVNA) responses measured by rapid fluorescent focus inhibition test between obese (body mass index, BMI > 30 kg/m2) and control (BMI < 25 kg/m2) patients after combined immunization with equine rabies immunoglobulin and purified chick-embryo cell rabies vaccine for post exposure prophylaxis treatment. ResultsPost-vaccination geometric mean titer (GMT) of RVNA concentrations between two groups at day 7 were 0.33 (95% CI: 0.23, 0.46) vs 0.39 (95% CI: 0.27, 0.55), 4.61 (95% CI: 3.20, 6.63) vs 3.78 (95% CI: 2.77, 5.16) at day 14, and 7.45 (95% CI: 5.86, 9.49) vs 5.93 (95%CI: 4.46–7.90) at day 28 for obese and control patients, respectively. There was no statistically significant difference of RVNA GMT between two groups. Seroconversion to at least adequate concentration (RVNA titer ≥0.5 IU/mL) rates were 34% at day 7 and 100% at days 14 and 28 in both groups. There were no immediate hypersensitivity reaction and no serious adverse events observed during the study period. ConclusionsThere was no evidence of immunosuppression of antibodies’ responses in obese patients. Combined ERIG and rabies virus vaccination for post exposure treatment is safe.

Comparison of a Micro-Neutralization Test with the Rapid Fluorescent Focus Inhibition Test for Measuring Rabies Virus Neutralizing Antibodies.

The rapid fluorescent focus inhibition test (RFFIT) is routinely used in the United States to measure rabies virus neutralizing antibodies (rVNA). RFFIT has a long history of reproducible and reliable results. The test has been modified over the years to use smaller volumes of reagents and samples, but requires a 50 μL minimum volume of test serum. To conduct pathogenesis studies, small laboratory animals such as mice are regularly tested for rVNA, but the minimum volume for a standard RFFIT may be impossible to obtain, particularly in scenarios of repeated sampling. To address this problem, a micro-neutralization test was developed previously. In the current study, the micro-neutralization test was compared to the RFFIT using 129 mouse serum samples from rabies vaccine studies. Using a cut-off value of 0.1 IU/mL, the sensitivity, specificity, and concordance of the micro-neutralization test were 100%, 97.5%, and 98%, respectively. The geometric mean titer of all samples above the cut-off was 2.0 IU/mL using RFFIT and 3.4 IU/mL using the micro-neutralization test, indicating that titers determined using the micro-neutralization test are not equivalent to RFFIT titers. Based on four rVNA-positive hamster serum samples, the intra-assay coefficient of variability was 24% and inter-assay coefficient of variability was 30.4%. These results support continued use of the micro-neutralization test to determine rabies virus neutralizing antibody titers for low-volume serum samples.

Alum adjuvanted rabies DNA vaccine confers 80% protection against lethal 50 LD50 rabies challenge virus standard strain.

Rabies is a serious concern world-wide. Despite availability of rabies vaccines for long; their efficacy, safety, availability and cost effectiveness has been a tremendous issue. This calls for improvement of rabies vaccination strategies. DNA vaccination has immense potential in this regard. The DNA vaccine pgp.LAMP-1 conferred 60% protection to BALB/c mice against 20 LD50 rabies challenge virus standard (CVS) strain challenge. Upon supplementation with Emulsigen-D, the vaccine formulation conferred complete protection against lethal challenge. To assess the feasibility of this vaccine formulation for human use, it was tested along with other FDA approved adjuvants, namely, Alum, Immuvac, Montanide ISA720 VG. Enhanced immune response correlated with high IgG antibody titer, Th2 biased response with a high level of rabies virus neutralizing antibodies (RVNAs) and IgG1/IgG2a ratio >1, observed upon alum supplementation of the rabies DNA vaccine. The total IgG antibody titer was 2IU/ml and total RVNA titer was observed to be 4IU/ml which is eight times higher than the minimum protective titer recommended by WHO. Furthermore, it conferred 80% protection against challenge with 50 LD50 of the rabies CVS strain, conducted in compliance with the potency test for rabies recommended by the National Institutes of Health (NIH), USA. Previously, we have established pre-clinical safety of this vaccine as per the guidelines of Schedule Y, FDA as well as The European Agency for evaluation of Medicinal Products. The vaccine showed no observable toxicity at the site of injection as well as at systemic level in Wistar rats when administered with 10X recommended dose. Therefore, supplementation of rabies DNA vaccine, pgp.LAMP-1 with alum would lead to development of a non-toxic, efficacious, stable and affordable vaccine that can be used to combat high numbers of fatal rabies infections tormenting developing countries.

Safety, tolerability and efficacy of intradermal rabies immunization with DebioJect™

In a single-center study, 66 healthy volunteers aged between 18 and 50years were randomized to be immunized against rabies with three different injection routes: intradermal with DebioJect™ (IDJ), standard intradermal with classical needle (IDS), also called Mantoux method, and intramuscular with classical needle (IM). “Vaccin rabique Pasteur®” and saline solution (NaCl 0.9%) were administered at D0, D7 and D28. Antigen doses for both intradermal routes were 1/5 of the dose for IM. Tolerability, safety and induced immunogenicity of IDJ were compared to IDS and IM routes. Pain was evaluated at needle insertion and at product injection for all vaccination visits. Solicited Adverse Event (SolAE) and local reactogenicity symptoms including pain, redness and pruritus were recorded daily following each vaccination visit. Adverse events (AE) were recorded over the whole duration of the study. Humoral immune response was measured by assessing the rabies virus neutralizing antibody (VNA) titers using Rapid Fluorescent Focus Inhibition Test (RFFIT). Results demonstrated that the DebioJect™ is a safe, reliable and efficient device. Significant decreases of pain at needle insertion and at vaccine injection were reported with IDJ compared to IDS and IM. All local reactogenicity symptoms (pain, redness and pruritus) after injection with either vaccine or saline solution, were similar for IDJ and IDS, except that IDJ injection induced more redness 30min after saline solution.No systemic SolAE was deemed related to DebioJect™ and classical needles. No AE was deemed related to DebioJect™. No Serious Adverse Event (SAE) was reported during the study.At the end of the study all participants were considered immunized against rabies and no significant difference in humoral response was observed between the 3 studied routes.

HEALTH SURVEY OF FREE-RANGING RACCOONS (PROCYON LOTOR) IN CENTRAL PARK, NEW YORK, NEW YORK, USA: IMPLICATIONS FOR HUMAN AND DOMESTIC ANIMAL HEALTH.

We conducted health assessments on 113 free-ranging raccoons ( Procyon lotor ) in Central Park, New York City, US, in February 2010, September 2010, and November 2011 in conjunction with a trap-vaccinate-release program to control a raccoon rabies epizootic. Five individuals were sampled at two time points for 118 raccoon examinations in total. We tested 13 of 13 and 8 of 13 euthanized raccoons for rabies and canine distemper virus (CDV), respectively, by antigen testing on brain tissue; all were negative for both viruses. Endoparasitism was the most common necropsy finding, with definitive identification of Baylisascaris procyonis in six of eight (75%) necropsied raccoons. Multiple intestinal parasites were detected in feces of living raccoons, including ascarid-type ova in 25 of 80 (31%) raccoons, with B. procyonis confirmed in one sample. Median blood lead level was 7.3 μg/dL (n=104). Rabies virus neutralizing antibody titer was ≥0.5 IU/mL in 9 of 88 (10%) raccoons naive to rabies vaccination and in 13 of 20 (65%) previously vaccinated raccoons. The majority of raccoons we tested were seropositive for canine parvovirus-2 (54/59, 92%) and Toxoplasma gondii (39/60, 65%). Fewer were seropositive for Rickettsia rickettsii (3/30, 10%). None were seropositive for CDV (n=108), canine adenovirus-1 (n=60), or Borrelia burgdorferi (n=30). Ectoparasites found during 16 of 118 (13.6%) physical examinations included Ixodes texanus ticks (15/118, 12.7%) and Trichodectes octomaculatus lice (1/118, 0.8%). We detected Campylobacter jejuni in 5 of 79 (6%) fecal samples. We detected 11 Salmonella enterica serotypes in 70 of 111 (63.1%) enteric cultures, the most common of which were Salmonella Newport (20/70, 29%) and Salmonella Oranienburg (20/70, 29%). These results indicate that raccoons in Central Park likely are involved in the environmental occurrence and potential disease transmission of a variety of infectious and noninfectious diseases of concern for human, wildlife, and domestic animal health.

An accelerated rabies vaccine schedule based on toll-like receptor 3 (TLR3) agonist PIKA adjuvant augments rabies virus specific antibody and T cell response in healthy adult volunteers

BackgroundRabies is a fatal disease where post-exposure prophylaxis (PEP) is crucial in preventing infection. However, deaths even after appropriate PEP, have been reported. The PIKA Rabies vaccine adjuvant is a TLR3 agonist that activates B and T cells leading to a robust immune response. MethodsWe conducted a phase I, open label, randomized study in healthy adults to assess the safety and immunogenicity of the PIKA Rabies vaccine and an accelerated vaccine regimen. Thirty-seven subjects were randomized into 3 groups: control vaccine classic regimen, PIKA vaccine classic regimen and PIKA vaccine accelerated regimen. Subjects were followed up for safety, rabies virus neutralizing antibodies (RVNA) and T cell responses. ResultsBoth the control and PIKA Rabies vaccine were well tolerated. All adverse events (AEs) were mild and self-limiting. Seventy-five percent of subjects in the PIKA accelerated regimen achieved a RVNA titer ⩾0.5IU/mL on day 7, compared to 53.9% in the PIKA classic regimen (p=0.411) and 16.7% in control vaccine classic regimen (p=0.012). The PIKA rabies vaccine elicited multi-specific rabies CD4 mediated T cell response already detectable ex vivo at day 7 after vaccination and that was maintained at day 42. ConclusionThe investigational PIKA rabies vaccine was well tolerated and more immunogenic than the commercially available vaccine in healthy adults.Clinical trial registry: The study was registered with clinicaltrials.gov NCT02657161.

Persistence of Rabies Virus-Neutralizing Antibodies after Vaccination of Rural Population following Vampire Bat Rabies Outbreak in Brazil.

BackgroundAnimal control measures in Latin America have decreased the incidence of urban human rabies transmitted by dogs and cats; currently most cases of human rabies are transmitted by bats. In 2004–2005, rabies outbreaks in populations living in rural Brazil prompted widespread vaccination of exposed and at-risk populations. More than 3,500 inhabitants of Augusto Correa (Pará State) received either post-exposure (PEP) or pre-exposure (PrEP) prophylaxis. This study evaluated the persistence of rabies virus-neutralizing antibodies (RVNA) annually for 4 years post-vaccination. The aim was to evaluate the impact of rabies PrEP and PEP in a population at risk living in a rural setting to help improve management of vampire bat exposure and provide additional data on the need for booster vaccination against rabies.Methodology/Principal FindingsThis prospective study was conducted in 2007 through 2009 in a population previously vaccinated in 2005; study participants were followed-up annually. An RVNA titer >0.5 International Units (IU)/mL was chosen as the threshold of seroconversion. Participants with titers ≤0.5 IU/mL or Equivalent Units (EU)/mL at enrollment or at subsequent annual visits received booster doses of purified Vero cell rabies vaccine (PVRV). Adherence of the participants from this Amazonian community to the study protocol was excellent, with 428 of the 509 (84%) who attended the first interview in 2007 returning for the final visit in 2009. The long-term RVNA persistence was good, with 85–88.0% of the non-boosted participants evaluated at each yearly follow-up visit remaining seroconverted. Similar RVNA persistence profiles were observed in participants originally given PEP or PrEP in 2005, and the GMT of the study population remained >1 IU/mL 4 years after vaccination. At the end of the study, 51 subjects (11.9% of the interviewed population) had received at least one dose of booster since their vaccination in 2005.Conclusions/SignificanceThis study and the events preceding it underscore the need for the health authorities in rabies enzootic countries to decide on the best strategies and timing for the introduction of routine rabies PrEP vaccination in affected areas.

Bait flavor preference and immunogenicity of ONRAB baits in domestic dogs on the Navajo Nation, Arizona

Abstract Rabies is responsible for an estimated 59,000 human deaths worldwide, and domestic dogs are the primary reservoir and vector of the disease. Among some nations, widespread vaccination has led to elimination of rabies in domestic dogs, yet dogs are still susceptible to rabies infection from interactions with wildlife reservoirs. On Tribal lands in the United States, less than 20% of domestic dogs are vaccinated for rabies, and parenteral vaccination is often unfeasible. Oral rabies vaccination may provide a solution, but a suitable bait flavor and vaccine must be identified. We evaluated 5 bait flavors (bacon, cheese, egg, fish, and sweet) in pairwise flavor-preference trials using placebo Ultralite baits in 26 domestic dogs on the Navajo Nation, Arizona. Each bait flavor was offered a total of 104 times. In all paired comparisons, bacon was more frequently preferred to the alternative. The sweet flavor (the flavor used operationally for oral rabies vaccine (ORV) distribution in Canada) was least preferred. Forty domestic dogs were offered baits containing ONRAB ORV: 14 received the sweet-flavored bait packet and 26 received bacon-flavored baits. Serum was collected from dogs before vaccination and at day 14 and 30 or 37 days after vaccination. Thirty-seven dogs consumed the baits, 2 baits (both sweet flavored) were chewed and spit out, and 1 (sweet flavored) was swallowed without apparent chewing (gulped). Eight dogs had preexisting rabies virus neutralizing antibody (RVNA) titers and 13 naive dogs failed to seroconvert during the study period. Overall, 27 dogs (67.5%) showed increased RVNA titers after vaccination, including 1 dog who chewed and spit out the bait and all dogs with positive baseline RVNA titers. Geometric mean titers for all dogs that seroconverted during the study period peaked at day 14 (1.2 IU/mL; n = 24) and decreased slightly by the final sampling day (0.8 IU/mL; n = 27). We conclude that bacon flavor may be a suitable bait flavor for ORV distribution in loosely kept or free-roaming domestic dogs. Seroconversion among dogs who ingested ONRAB-filled baits was variable. Why 13 dogs who consumed ORV baits failed to seroconvert remains unknown. Additional research to improve seroconversion rates in domestic dogs after vaccination with ONRAB is recommended.

A Serological Study in Response to People at Occupational Risk of Rabies Virus Exposure in Nepal

A serological study to know the antibody titer against rabies virus in human beings, who are at occupational risk, was conducted in Nepal in 2014. A total 44 serum samples were collected out of which 21 samples were collected from medical professionals (working at Sukraraj Tropical Hospital) and 23 were collected from veterinary professionals (working at Central Veterinary Hospital, Central Veterinary Laboratory and Rabies Vaccine Production Laboratory) in Kathmandu. Among the 44 samples, 4 were collected from unvaccinated persons. The other 40 people sampled were vaccinated with inactivated rabies vaccine. All samples were subjected to the Rabies Fluorescent Focus Inhibition Test (RFFIT) test at Centre for Disease Control and Prevention, Atlanta, USA. The antibody level of 7 persons was found to be less than the WHO recommended titer of 0.5 IU/ml. Six medical professionals and one veterinary professional had a low rabies virus neutralizing antibody titer. The 4 samples collected from unvaccinated persons, and 3 collected from vaccinated persons had a titer below 0.5 IU/ml. This study shows that medical and veterinary professionals who are responsible to nurse or handle rabies patients, rabid animals or rabies virus are still at high risk. This underscores the importance of recommendations for regular serological testing of occupationally exposed individuals and vaccinating booster dose when necessary.