Rabies Virus Neutralizing Antibody Titers Research Articles

Does Perioperative Administration of Rabies Vaccine in Dogs Undergoing Surgical Sterilization Induce an Adequate Antibody Response?

High-volume spay/neuter events may facilitate access to free-roaming dogs to admi-nister rabies vaccination, but important questions remain regarding the effect of surgery and anesthesia on the immune response to a vaccine administered in the perioperative period. This study evaluated the immunogenicity of primary rabies vaccination in dogs when administered during the immediate perioperative period at the time of surgical sterilization (ovariohysterectomy/orchidectomy). Healthy dogs of both sexes presenting for surgical sterilization who had never been vaccinated against rabies virus were eligible for enrollment in the study. Fifty dogs ranging in age from 5 to 96 months were enrolled and were vaccinated against rabies virus during the recovery period following anesthesia and surgery. Rabies virus neutralizing antibody (RVNA) titers were measured preoperatively and 28 days postoperatively. This cohort was compared to a historical control cohort of 57 dogs who received primary rabies vaccination for travel purposes and had RVNA titers measured at the same laboratory as the study group 28-35 days post-vaccination. After controlling for age and sex, there was no statistically significant difference in immunogenicity of a rabies vaccine administered to dogs during the perioperative period in comparison to dogs that received the rabies vaccine for travel alone in the absence of surgery. Perioperative administration of a rabies vaccine in dogs under-going surgical sterilization induces an adequate antibody response. We recommend that rabies vaccine be administered perioperatively during spay/neuter campaigns in canine rabies endemic areas if other opportunities to ac-cess veterinary care and rabies vaccination are limited.

Safety and immunogenicity of three dose levels of an investigational, highly purified Vero cell rabies vaccine: A randomized, controlled, observer-blinded, Phase II study with a simulated post-exposure regimen in healthy adults

ABSTRACT A serum-free, highly purified rabies vaccine produced in Vero cells is under development. The initial formulation, PVRV-NG, was evaluated in five Phase II studies and subsequently reformulated (PVRV-NG2). This multicenter, observer-blinded Phase II study investigated the safety and immune response of three different doses (antigen content) of PVRV-NG2 versus a licensed human diploid cell rabies vaccine (HDCV; Imovax rabies®). Healthy adults (N = 320) were randomized to receive PVRV-NG2 (low, medium, or high dose), PVRV-NG, or HDCV (2:2:2:1:1 ratio), according to a five-dose Essen simulated post-exposure regimen (Days [D] 0, 3, 7, 14, and 28). All participants received human rabies immunoglobulin intramuscularly on D0. Immunogenicity was assessed at D0, 14, 28, 42, and 6 months after the final injection using the rapid fluorescent focus inhibition test. Seroconversion rates were calculated as the percentage of participants achieving rabies virus neutralizing antibody titers ≥0.5 IU/mL. All analyses were descriptive. At each timepoint, geometric mean titers (GMTs) increased with antigen content (measured using an enzyme-linked immunosorbent assay). High-dose PVRV-NG2 GMTs were the highest at all timepoints, medium-dose PVRV-NG2 GMTs were similar to those with HDCV, and low-dose PVRV-NG2 GMTs were similar to PVRV-NG. The safety profile of PVRV-NG2 was comparable to PVRV-NG; however, fewer injection site reactions were reported with PVRV-NG2 or PVRV-NG (range 36.7–47.5%) than with HDCV (61.5%). This study demonstrated a dose–effect of antigen content at all timepoints. As post-exposure prophylaxis, the safety and immunogenicity profiles of the high-dose PVRV-NG2 group compared favorably with HDCV. Clinicaltrials.gov number: NCT03145766.

RABIES VIRUS SEROSURVEY OF THE SMALL INDIAN MONGOOSE (URVA AUROPUNCTATA) ACROSS MULTIPLE HABITATS IN PUERTO RICO, 2014-21.

The small Indian mongoose (Urva auropuncata) is a rabies reservoir in Puerto Rico and accounts for over 70% of reported animal rabies cases annually. The presence of rabies virus-neutralizing antibodies (RVNA) is often used as a tool to measure exposure to rabies virus in wildlife populations. We conducted a serosurvey of mongooses at 11 sites representing six habitat types across Puerto Rico. We collected a serum sample from 464 individual mongooses during 2014-21. Overall, 80/464 (17.0%; 95% confidence interval, 14.1-20.9%; 55 male, 23 female, and two sexes not recorded) of individual mongooses sampled across all habitats were RVNA positive. The geometric mean (SD) RVNA titer for 80 unique seropositive animals was 0.58 (2.92) IU/mL. Our models indicated that the probability of mongooses being RVNA seropositive mostly varied by habitat, with some influence of sex in the individual-level analyses. Population-level RVNA seroprevalence is dynamic in mongoose populations, but these data may shed light on rabies virus transmission across regions to help inform rabies management activities in Puerto Rico.

Does Perioperative Administration of Rabies Vaccine in Dogs Undergoing Surgical Sterilization Induce an Adequate Antibody Response?

High-volume spay/neuter events may facilitate access to free-roaming dogs to administer rabies vaccination, but important questions remain regarding the effect of surgery and anesthesia on the immune response to a vaccine administered in the perioperative period. This study evaluated the immunogenicity of primary rabies vaccination in dogs when administered during the immediate perioperative period at the time of surgical sterilization (ovariohysterectomy/orchidectomy). Healthy dogs of both sexes presenting for surgical sterilization who had never been vaccinated against rabies virus were eligible for enrollment in the study. Fifty dogs ranging in age from 5 to 96 months were enrolled and were vaccinated against rabies virus during the recovery period following anesthesia and surgery. Rabies virus neutralizing antibody (RVNA) titers were measured preoperatively and 28 days postoperatively. This cohort was compared to a historical control cohort of 57 dogs who received primary rabies vaccination for travel purposes and had RVNA titers measured at the same laboratory as the study group 28-35 days post-vaccination. After controlling for age and sex, there was no statistically significant difference in immunogenicity of a rabies vaccine administered to dogs during the perioperative period in comparison to dogs that received the rabies vaccine for travel alone in the absence of surgery. Perioperative administration of a rabies vaccine in dogs undergoing surgical sterilization induces an adequate antibody response. We recommend that rabies vaccine be administered perioperatively during spay/neuter campaigns in canine rabies endemic areas if other opportunities to access veterinary care and rabies vaccination are limited.

Improved Transdermal Delivery of Rabies Vaccine using Iontophoresis Coupled Microneedle Approach.

This study was aimed to develop rabies vaccine incorporated microneedle (MN) patches and evaluate the immunogenicity of prepared formulations in combination with iontophoresis. Patches comprising of polyvinyl pyrrolidone, hyaluronic acid and polyethylene glycol 400 were engineered by vacuum micromolding technique. Physical evaluation of patches included determination of folding endurance, % swelling and morphological features. In vitro release study was performed in skin simulant agarose gel using model drug (methylene blue) loaded patches. In vitro insertion ability was assessed using stratum corneum simulant parafilm. In vivo insertion study was performed in rats. Immunogenicity was evaluated in dogs by determining immunoglobulin G (IgG) and rabies virus neutralizing antibodies (RVNA) titer. Patches displayed uniformly distributed microprojections with pointed tips and smooth surface, ~ 70% swelling, remained intact for ~ 200 foldings and successfully penetrated the parafilm. The area covered by model drug across agarose gel was almost double following treatment with MN-iontophoresis combination (MNdi) compared to MN alone (MNdo). Histological examination of rat skin treated with vaccine laden MN (MNvo) and MN-iontophoresis combination (MNvi) confirmed the formation of grooves in epidermis without any damage to the deep vasculature. A ~ 73% and ~ 206% increase (compared to untreated counterpart) was observed in the IgG titer of MNvo and MNvi treated dogs, respectively. The RVNA titer was increased by ~ 1.2 and ~ 2.2 times (compared to threshold value) after MNvo and MNvi treatment, respectively. MN-iontophoresis combination provided relatively potent immunogenic response over the conventional intramuscular injection, hence, can be used for administering vaccines transcutaneously.

Comparative Evaluation of Intradermal vis-à-vis Intramuscular Pre-Exposure Prophylactic Vaccination against Rabies in Cattle.

Rabies is a progressively fatal viral disease affecting a wide variety of warm-blooded animals and human beings. With cattle being major part of Indian livestock population, rabies can result in significant financial losses. Immunization of livestock vulnerable to exposure is the best way to control rabies. The present study was undertaken to investigate the efficacy of a rabies pre-exposure prophylactic vaccine administered through different routes and to sequentially monitor the levels of rabies virus-neutralizing antibody (RVNA) titers in cattle. Thirty cattle were divided into five groups of six animals each. Group I and III animals were immunized with 1 mL and 0.2 mL of rabies vaccine through intramuscular (IM) and intradermal (ID) routes, respectively, on day 0, with a booster dose on day 21; Group II and IV animals were immunized with 1 mL and 0.2 mL of rabies vaccine, respectively, without the booster dose; unvaccinated animals served as a control (Group V). Serum samples were collected on days 0, 14, 28, and 90 to estimate RVNA titers using the rapid fluorescent focus inhibition test (RFFIT). The titers were above an adequate level (≥0.5 IU/mL) on day 14 and maintained up to 90 days in all animals administered the rabies vaccine through the IM and ID route with or without a booster dose. The study indicated that both routes of vaccination are safe and effective in providing protection against rabies. Hence, both routes can be considered for pre-exposure prophylaxis. However, the ID route proved to be more economical due to its dose-sparing effect.

One-week intramuscular or intradermal pre-exposure prophylaxis with human diploid cell vaccine or Vero cell rabies vaccine, followed by simulated post-exposure prophylaxis at one year: A phase III, open-label, randomized, controlled trial to assess immunogenicity and safety

Shorter rabies pre-exposure prophylaxis (PrEP) regimens may offer improved convenience and feasibility over classic 3-week regimens, for example in regions with poor access to vaccines or for travelers to rabies-endemic regions. In this multicenter, open-label, controlled trial, 570 healthy participants aged 2–64 years were randomized to receive: 1-week PrEP (vaccination days [D]0 and 7; Group 1) or classic 3-week PrEP regimen (D0, D7, and D21; Group 2) with one 1.0 mL intramuscular [IM] dose of human diploid cell culture rabies vaccine (HDCV) at each visit; 1-week PrEP with two 0.1 mL intradermal (ID) HDCV doses at each visit (Group 3); or 1-week PrEP with one 0.5 mL IM dose (Group 4) or two 0.1 mL ID doses (Group 5) of Vero cell rabies vaccine (PVRV) at each visit. Participants received simulated post-exposure prophylactic (PEP) vaccination (two IM or ID doses of HDCV or PVRV three days apart) one year later. Rabies virus neutralizing antibody titers and seroconversion (titers ≥ 0.5 IU/mL) rates were assessed 14 days and up to 1 year post-PrEP, and pre- and post-PEP. Safety was assessed throughout the study. Seroconversion rates were high 14 days post-last PrEP injection (ranging from 96.7 % to 97.2 % across groups 1, 3–5; 1-week PrEP) and reached 100 % in Group 2 (3-week PrEP). Non-inferiority of Group 1 versus Group 2 in terms of seroconversion rates 14 days post-last PrEP injection (primary objective) was not demonstrated. After simulated PEP, all groups showed rapid and robust immune responses, with all but one participant achieving seroconversion (titers ≥ 0.5 IU/mL). There were no safety concerns, and the tolerability profiles of the vaccines were similar across the groups.A 1-week, IM or ID PrEP regimen with HDCV or PVRV provided efficacious priming, enabling rapid robust anamnestic responses to simulated PEP 1 year later across age groups.ClinicalTrials.gov number: NCT03700242.WHO Universal Trial Number (UTN): U1111-1183-5743.

Serum-free purified Vero rabies vaccine is safe and immunogenic in children: Results of a randomized phase II pre-exposure prophylaxis regimen study

BackgroundA serum-free, highly purified Vero rabies vaccine (PVRV-NG) has been developed with no animal or human components and low residual DNA content. A phaseII randomized clinical study aimed to demonstrate the non-inferiority of the immune response and assess the safety profile of PVRV-NG versus a licensed human diploid cell culture rabies vaccine (HDCV) in a pre-exposure regimen in healthy children and adolescents in the Philippines. MethodologyChildren aged 2–11 years and adolescents aged 12–17 years were randomized (2:1) to receive three injections of either PVRV-NG or HDCV (on day [D] 0, D7 and D28). Rabies virus-neutralizing antibodies (RVNA) were measured at D0, D42 and 6 months after the first injection (month [M] 6). Safety was assessed during the vaccination period and up to 28 days after the last vaccination. Serious adverse events were followed until 6 months after last vaccination. Principal findings342 healthy participants (171 children and 171 adolescents) were randomized and followed for 6 months after the last dose. All participants in both groups had an RVNA titer ≥ 0.5 IU/ml at D42, demonstrating non-inferiority in seroconversion rate for PVRV-NG versus HDCV. Over 90% of participants had RVNA titer ≥ 0.5 IU/ml at M6. PVRV-NG was well tolerated after each vaccination and up to 6 months following the last dose. There were no major safety concerns during the study, and the type and severity of solicited adverse events was similar for both treatment groups. ConclusionsThis study demonstrated the non-inferior immune profile of PVRV-NG compared with HDCV in a pre-exposure setting within a pediatric population. PVRV-NG was well tolerated with no safety concerns. This study is registered at ClinicalTrials.gov (NCT01930357) and EU Clinical Trials Register (2015–003203-30).

Immunogenicity and safety of human diploid cell vaccine (HDCV) vs. purified Vero cell vaccine (PVRV) vs. purified chick embryo cell vaccine (PCECV) used in post-exposure prophylaxis: a systematic review and meta-analysis

ABSTRACT This study comprehensively evaluated and compared three human rabies vaccines. Seven electronic databases were systematically searched. The Cochrane Handbook v5.1.0 was used to assess the risk of bias. A random-effects model was used to combine individual rates, and network meta-analysis was used for pairwise comparisons. Twenty-seven articles were included, with a total of 18,630 participants. The pooled incidence of the total adverse reaction to HDCV was significantly lower than that of PCECV. HDCV administration resulted in a lower incidence of local pain, fever, and weakness than purified Vero cell vaccine. HDCV caused a lower incidence of local pain and fever than PCECV. No significant difference was observed in terms of the seroconversion rate on day 7 or the rabies virus-neutralizing antibody titer on day 14. HDCV demonstrated superiority in terms of safety compared with the other two rabies vaccines, while the same was not observed in terms of immunogenicity.

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.

Immunogenicity of 2-dose pre-exposure rabies vaccine co-administered with quadrivalent influenza vaccine in children

ObjectivesThe World Health Organization recommends a 2-dose rabies pre-exposure prophylaxis (PrEP) regimen. This study aimed to compare the immunogenicity of rabies PrEP regimens co-administered with inactivated quadrivalent influenza vaccine (IIV4). MethodsChildren aged 3 to 9 years were randomly assigned (2:2:1) to receive 0.25 mL of chromatographically purified Vero cell rabies vaccine intramuscularly: Group A at day 0, 7 with IIV4; Group B at day 0, 28 with IIV4; Group C at day 0, 7. A booster-dose of CPRV was given on day 365. Primary outcome was the proportion of children with protective rabies virus neutralizing antibody (RVNA) ≥ 0.5 IU/mL, on day 42 and 7 days post-booster. ResultsFrom November 2019 to January 2020; 100 children with a median age (IQR) of 5.4 years (4.8-7.3) were enrolled. All participants achieved protective RVNA titers on day 42 and 7-days post booster. Geometric mean titers (GMT) at day 42 were Group A, 8.98(95%CI 7.06-11.42); Group B, 23.89(95%CI 19.33-29.51); Group C, 9.94(95%CI 7.03-14.06). Likewise, RVNA GMT at 7 days post-booster were Group A, 42.53(95%CI 18.41-66.64); Group B, 23.19(95%CI 17.28-29.10); Group C, 57.75 (95%CI 35.86-79.67). ConclusionsThe 2-dose PrEP regimen of rabies vaccine produces adequate immune response either 0,7 or 0, 28 regimens.

Safety and efficacy of rabies immunoglobulin in pediatric patients with suspected exposure

ABSTRACT Rabies is a deadly viral zoonosis with global disease burden. Following exposure to a rabid animal, post-exposure prophylaxis (PEP) is the standard of care for unvaccinated persons. Despite the large proportion of pediatric cases, limited safety and efficacy data exist for use in pediatric patients. We report the safety, efficacy, and immunogenicity of a phase 4, prospective, 2-center, open-label, single-arm clinical trial evaluating human rabies immunoglobulin (HRIG150; KEDRAB 150 IU/mL) as part of PEP in patients (aged <17) with suspected or confirmed rabies exposure, where PEP was indicated. Thirty participants received 20 IU/kg HRIG150 infiltrated into the detectable wound site(s), with any remainder injected intramuscularly, concomitantly with the first of a 4-dose series (days 0, 3, 7, and 14) of rabies vaccine. Rabies virus neutralizing antibody (RVNA) titers and tolerability were assessed on day 14 following administration. Participant safety was monitored for 84 days. No serious adverse events, rabies infections, or deaths were recorded. Twenty-one participants (70.0%) experienced a total of 57 treatment-emergent adverse events (TEAEs) within 14 days following administration. Twelve participants (40.0%) experienced a total of 13 adverse events deemed treatment related. All TEAEs were mild in severity. On day 14, 28 participants (93.3%) had RVNA levels of ≥0.5 IU/mL (mean±standard deviation: 18.89 ± 31.61). These results demonstrate that HRIG150 is well tolerated and effective in pediatric patients as a component of PEP. To the authors’ knowledge, this study is the first to establish pediatric safety and efficacy of HRIG in the US.

Generation of a recombinant rabies virus expressing green fluorescent protein for a virus neutralization antibody assay.

BackgroundFluorescent antibody virus neutralization (FAVN) test is a standard assay for quantifying rabies virus-neutralizing antibody (VNA) in serum. However, a safer rabies virus (RABV) should be used in the FAVN assay. There is a need for a new method that is economical and time-saving by eliminating the immunostaining step.ObjectivesWe aimed to improve the traditional FAVN method by rescuing and characterizing a new recombinant RABV expressing green fluorescent protein (GFP).MethodsA new recombinant RABV expressing GFP designated as ERAGS-GFP was rescued using a reverse genetic system. Immuno-fluorescence assay, peroxidase-linked assay, electron microscopy and reverse transcription polymerase chain reaction were performed to confirm the recombinant ERAGS-GFP virus as a RABV expressing the GFP gene. The safety of ERAGS-GFP was evaluated in 4-week-old mice. The rabies VNA titers were measured and compared with conventional FAVN and FAVN-GFP tests using VERO cells.ResultsThe virus propagated in VERO cells was confirmed as RABV expressing GFP. The ERAGS-GFP showed the highest titer (108.0 TCID50/mL) in VERO cells at 5 days post-inoculation, and GFP expression persisted until passage 30. The body weight of 4-week-old mice inoculated intracranially with ERAGS-GFP continued to increase and the survival rate was 100%. In 62 dog sera, the FAVN-GFP result was significantly correlated with that of conventional FAVN (r = 0.95).ConclusionsWe constructed ERAGS-GFP, which could replace the challenge virus standard-11 strain used in FAVN test.

Redefining Non-Inferiority in Anamnestic Antibody Responses Using the Mean Increase of Log-Transformed Antibody Titers after Revaccination: Secondary Analysis of a Randomized Controlled Rabies Vaccination Trial.

Non-inferiority in the anamnestic antibody response is conventionally determined by comparing seroconversion rates after revaccination. However, this approach is inadequate in the case of high pre-booster antibody titers. Therefore, we propose an alternative method to determine non-inferiority of booster responses. We used anonymized data from a randomized controlled trial (NCT01388985; EudraCT 2011-001612-62) in 500 adults, comparing a two-visit primary vaccination schedule (two intradermal 0.1 mL rabies vaccine doses on day 0 and 7) with a three-visit schedule (single intradermal 0.1 mL dose on day 0, 7, and 28). Participants were revaccinated intradermally (single dose) 1 to 3 years later. Rabies virus neutralizing antibody titers were measured on day 0 and 7 after revaccination. After log3-transformation of antibody titers, the mean increase in titers after revaccination was compared between schedules. Non-inferiority was defined as the lower bound of the two-sided 95% confidence interval not exceeding −0.369. Four hundred and ten participants fulfilled the inclusion criteria. The mean increase in log3 titer was 2.21 and 2.31 for the two-visit and three-visit schedule, respectively. The difference between these increases was −0.10 [−0.28, 0.08], meeting the non-inferiority criterion. In conclusion, comparing mean increases in log-transformed titers after revaccination appears to be a feasible and more informative method of studying non-inferiority regarding the anamnestic antibody response.

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.

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.