Human infection due to recombinant vaccinia-rabies glycoprotein virus

A single dose of an ALVAC vector-based RABV virus-like particle candidate vaccine induces a potent immune response in mice, cats and dogs

Rabies, caused by the Rabies virus (RABV), is a highly fatal zoonotic disease. Existing rabies vaccines have demonstrated good immune efficacy, but the complexity of immunization procedures and high cost has impeded the elimination of RABV, particularly in the post-COVID-19 era. There is a pressing need for safer and more effective rabies vaccines that streamline vaccination protocols and reduce expense. To meet this need, we have developed a potential rabies vaccine candidate called ALVAC-RABV-VLP, utilizing CRISPR/Cas9 gene editing technology. This vaccine employs a canarypox virus vector (ALVAC) to generate RABV virus-like particles (VLPs). In mice, a single dose of ALVAC-RABV-VLP effectively activated dendritic cells (DCs), follicular helper T cells (Tfh), and the germinal centre (GC)/plasma cell axis, resulting in durable and effective humoral immune responses. The survival rate of mice challenged with lethal RABV was 100%. Similarly, in dogs and cats, a single immunization with ALVAC-RABV-VLP elicited a stronger and longer-lasting antibody response. ALVAC-RABV-VLP induced superior cellular and humoral immunity in both mice and beagles compared to the commercial inactivated rabies vaccine. In conclusion, ALVAC-RABV-VLP induced robust protective immune responses in mice, dogs and cats, offering a novel, cost-effective, efficient, and promising approach for herd prevention of rabies.

A modified recombinant adenovirus vector containing dual rabies virus G expression cassettes confers robust and long-lasting humoral immunity in mice, cats, and dogs

During the COVID-19 epidemic, the incidence of rabies has increased in several countries, especially in remote and disadvantaged areas, due to inadequate surveillance and declining immunization coverage. Multiple vaccinations with inactivated rabies virus vaccines for pre- or post-exposure prophylaxis are considered inefficient, expensive and impractical in developing countries. Herein, three modified human recombinant adenoviruses type 5 designated Adv-RVG, Adv-E1-RVG, and Adv-RVDG, carrying rabies virus G (RVG) expression cassettes in various combinations within E1 or E3 genomic regions, were constructed to serve as rabies vaccine candidates. Adv-RVDG mediated greater RVG expression both in vitro and in vivo and induced a more robust and durable humoral immune response than the rabies vaccine strain SAD-L16, Adv-RVG, and Adv-E1-RVG by more effectively activating the dendritic cells (DCs) - follicular helper T (Tfh) cells - germinal centre (GC) / memory B cells (MBCs) - long-lived plasma cells (LLPCs) axis with 100% survival after a lethal RABV challenge in mice during the 24-week study period. Similarly, dogs and cats immunized with Adv-RVDG showed stronger and longer-lasting antibody responses than those vaccinated with a commercial inactivated rabies vaccine and showed good tolerance to Adv-RVDG. In conclusion, our study demonstrated that simultaneous insertion of protective antigens into the E1 and E3 genomic regions of adenovirus vector can significantly enhance the immunogenicity of adenoviral-vectored vaccines, providing a theoretical and practical basis for the subsequent development of multivalent and multi-conjugated vaccines using recombinant adenovirus platform. Meanwhile, our data suggest Adv-RVDG is a safe, efficient, and economical vaccine for mass-coverage immunization.

Safety and immunogenicity of orally administered poxvirus vectored constructs in the white-footed mouse (Peromyscus leucopus)

Globally, zoonotic spillover is becoming more frequent and represents a growing public health concern. Reservoir-targeted vaccination offers an intriguing alternative to traditional vaccine practices by establishing protection in wild populations that maintain the natural pathogen cycle. As an important pathogen reservoir, Peromyscus leucopus Rafinesque or the white-footed mouse has been the target of several experimental vaccines. However, strategies are limited by the method of administration, need for repeated dosing, or safety of constructs in the field. To address these concerns, we evaluated two highly attenuated poxviruses, raccoonpox virus (RCN) and modified vaccinia Ankara (MVA) virus as potential oral vaccine vectors in white-footed mice. Following oral administration, P. leucopus showed no adverse signs. A single oral dose elicited robust immune responses in mice to the foreign influenza hemagglutinin protein expressed by poxvirus vaccine vectors. Serum hemagglutinin inhibition antibody titers were detected by day 7 post immunization and persisted until study termination (77 days post immunization). This study establishes the safety and immunogenicity of recombinant MVA and RCN poxviruses in P. leucopus and demonstrates the suitability of these vectors as part of a reservoir-targeted vaccine strategy for white-footed mice.

An mRNA-based rabies vaccine induces strong protective immune responses in mice and dogs

Rabies is a lethal zoonotic disease that is mainly caused by the rabies virus (RABV). Although effective vaccines have long existed, current vaccines take both time and cost to produce. Messenger RNA (mRNA) technology is an emergent vaccine platform that supports rapid vaccine development on a large scale. Here, an optimized mRNA vaccine construct (LVRNA001) expressing rabies virus glycoprotein (RABV-G) was developed in vitro and then evaluated in vivo for its immunogenicity and protective capacity in mice and dogs. LVRNA001 induced neutralizing antibody production and a strong Th1 cellular immune response in mice. In both mice and dogs, LVRNA001 provided protection against challenge with 50-fold lethal dose 50 (LD50) of RABV. With regards to protective efficiency, an extended dosing interval (14 days) induced greater antibody production than 3- or 7-day intervals in mice. Finally, post-exposure immunization against RABV was performed to evaluate the survival rates of dogs receiving two 25 μg doses of LVRNA001 vs. five doses of inactivated vaccine over the course of three months. Survival rate in the LVRNA001 group was 100%, whereas survival rate in the inactivated vaccine control group was only 33.33%. In conclusion, these results demonstrated that LVRNA001 induced strong protective immune responses in mice and dogs, which provides a new and promising prophylactic strategy for rabies.

[Anti-rabies vaccines applied in the Russian Federation and perspectives for their improvement]

Rabies is almost ubiquitous (except in certain areas) and poses a significant danger to both animals and humans. Every year around 55,000 people die from this disease worldwide. In the Russian Federation alone 400,000- 450,000 patients annually apply for anti-rabies treatment. In the absolute majority of cases human infection is caused by contact with infected animals. In RF, a number of cultured inactivated anti-rabies vaccines for medical and veterinary purposes have been developed, registered and used for specific prevention of rabies. These vaccine preparations have shown high effectiveness in preventing infection in domestic and farm animals. At the same time, the main reservoir of the rabies virus (Mononegavirales: Rhabdoviridae: Lyssavirus) (RV) are wild carnivores (Mammalia: Carnivora). For the purpose of their oral immunization, live virus vaccines from attenuated (fixed) strains of RV that are little resistant in the external environment are used. In Western Europe and North America there is successful experience with recombinant anti-rabies vaccine preparations containing a viral glycoprotein gene (G-protein). Such vaccines are safe for humans and animals. In Russia also had been developed a vector anti-rabies vaccine based on adenovirus (Adenoviridae), which can be used to combat this infection. Currently, in addition to classical rabies, diseases caused by new, previously unknown lyssaviruses (Lyssavirus) are becoming increasingly important. Bats (Mammalia: Microchiroptera) are their vectors. Cases of illness and death after contact with these animals have been described. In the near future, we should expect the development of new vaccines that will provide protection not only against RV, but also against other lyssaviruses.

Review of Oral Rabies Vaccination of Dogs and Its Application in India

Oral rabies vaccines (ORVs) have been in use to successfully control rabies in wildlife since 1978 across Europe and the USA. This review focuses on the potential and need for the use of ORVs in free-roaming dogs to control dog-transmitted rabies in India. Iterative work to improve ORVs over the past four decades has resulted in vaccines that have high safety profiles whilst generating a consistent protective immune response to the rabies virus. The available evidence for safety and efficacy of modern ORVs in dogs and the broad and outspoken support from prominent global public health institutions for their use provides confidence to national authorities considering their use in rabies-endemic regions. India is estimated to have the largest rabies burden of any country and, whilst considerable progress has been made to increase access to human rabies prophylaxis, examples of high-output mass dog vaccination campaigns to eliminate the virus at the source remain limited. Efficiently accessing a large proportion of the dog population through parenteral methods is a considerable challenge due to the large, evasive stray dog population in many settings. Existing parenteral approaches require large skilled dog-catching teams to reach these dogs, which present financial, operational and logistical limitations to achieve 70% dog vaccination coverage in urban settings in a short duration. ORV presents the potential to accelerate the development of approaches to eliminate rabies across large areas of the South Asia region. Here we review the use of ORVs in wildlife and dogs, with specific consideration of the India setting. We also present the results of a risk analysis for a hypothetical campaign using ORV for the vaccination of dogs in an Indian state.

Comparative Study of Optical Markers to Assess Bait System Efficiency Concerning Vaccine Release in the Oral Cavity of Dogs

Oral vaccination of dogs against rabies has the potential to achieve mass coverage and thus deplete the virus of its most important reservoir host species. There is, however, no established non-invasive method to evaluate vaccine release in the oral cavity, following bait ingestion. In this study, two pre-selected marker methods in conjunction with their acceptance were assessed in local Thai dogs. Shelter dogs (n = 47) were offered one of four randomized bait formulations; bait type A-, containing Green S (E142) in a fructose solution; type B-, containing Patent Blue V (E131) in a fructose solution; type C-, containing the medium used for delivery of oral rabies vaccine in baits commercially produced; and type D-, containing denatonium benzoate, which was to serve as the negative control, due to its perceived bitterness. Patent Blue V was found to possess overall stronger dyeing capacities compared to Green S. Furthermore, there was no significant difference in the acceptance or bait handling of Patent Blue V baits compared to those containing the oral rabies vaccine medium alone, suggesting the potential use of this dye as a surrogate for rabies vaccine when testing newly developed bait formats.

Role of Oral Rabies Vaccines in the Elimination of Dog-Mediated Human Rabies Deaths

Domestic dogs are responsible for nearly all the »59,000 global human rabies deaths that occur annually. Numerous control measures have been successful at eliminating dog-mediated human rabies deaths in upper-income countries, including dog population management, parenteral dog vaccination programs, access to human rabies vaccines, and education programs for bite prevention and wound treatment. Implementing these techniques in resource-poor settings can be challenging; perhaps the greatest challenge is maintaining adequate herd immunity in free-roaming dog populations. Oral rabies vaccines have been a cornerstone in rabies virus elimination from wildlife populations; however, oral vaccines have never been effectively used to control dog-mediated rabies. Here, we convey the perspectives of the World Organisation for Animal Health Rabies Reference Laboratory Directors, the World Organisation for Animal Health expert committee on dog rabies control, and World Health Organization regarding the role of oral vaccines for dogs. We also issue recommendations for overcoming hesitations to expedited field use of appropriate oral vaccines.

Public Veterinary Medicine: Public Health: Rabies surveillance in the United States during 2018

OBJECTIVE

To describe rabies and rabies-related events occurring during 2018 in the United States.

ANIMALS

All animals submitted for laboratory diagnosis of rabies in the United States during 2018.

PROCEDURES

State and territorial public health departments provided data on animals submitted for rabies testing in 2018. Data were analyzed temporally and geographically to assess trends in domestic animal and wildlife rabies cases.

RESULTS

During 2018, 54 jurisdictions reported 4,951 rabid animals to the CDC, representing an 11.2% increase from the 4,454 rabid animals reported in 2017. Texas (n = 695 [14.0%]), Virginia (382 [7.7%]), Pennsylvania (356 [7.2%]), North Carolina (332 [6.7%]), Colorado (328 [6.6%]), and New York (320 [6.5%]) together accounted for almost half of all rabid animals reported in 2018. Of the total reported rabies cases, 4,589 (92.7%) involved wildlife, with bats (n = 1,635 [33.0%]), raccoons (1,499 [30.3%]), skunks (1,004 [20.3%]), and foxes (357 [7.2%]) being the major species. Rabid cats (n = 241 [4.9%]) and dogs (63 [1.3%]) accounted for > 80% of rabid domestic animals reported in 2018. There was a 4.6% increase in the number of samples submitted for testing in 2018, compared with the number submitted in 2017. Three human rabies deaths were reported in 2018, compared with 2 in 2017.

CONCLUSIONS AND CLINICAL RELEVANCE

The overall number of animal rabies cases increased from 2017 to 2018. Laboratory diagnosis of rabies in animals is critical to ensure that human rabies postexposure prophylaxis is administered judiciously.

A novel rabies vaccine based on infectious propagating particles derived from hybrid VEEV-Rabies replicon

BACKGROUND

Live attenuated vaccines (LAVs) can mimic natural infection and have advantages to stimulate a robust and sustained immune response as well as to confer long-term protection. However, safety concerns is one of the major obstacles for LAVs development. In an effort to achieve the optimal balance between immunogenicity and safety, researchers currently have taken different strategies for the development of LAVs.

METHODS

We constructed a novel infectious self-propagating hybrid replicon particle (PRP), VEEV-RABV-G, through replacing the entire structural proteins of the Venezuelan equine encephalitis virus (VEEV) with the glycoprotein of rabies virus (RABV-G) as the single structural protein. We evaluated the potential of VEEV-RABV-G as a safe live attenuated vaccine in mice model.

FINDINGS

We found that VEEV-RABV-G could self-propagate efficiently in cell culture and induce a robust humoral immunity and provide protection against virulent RABV challenge in immunized mice. Remarkably, VEEV-RABV-G is highly attenuated in both adult and sucking mice, causing much weaker inflammatory and apoptotic effects in the brains of infected adult mice and significantly lower weight loss and morbidity compared with the commonly used RABV-derived LAVs.

INTERPRETATION

This study reveals the feasibility of developing novel rabies vaccines based on the self-replicating PRPs.

FUNDING

This work was supported by the National Key Research and Development Program of China (2016YFD0500400).

Working Safely with Vaccinia Virus: Laboratory Technique and Review of Published Cases of Accidental Laboratory Infections with Poxviruses

Vaccinia virus, the prototype Orthopoxvirus, is widely used in the laboratory as a model system to study various aspects of viral biology and virus-host interactions, as a protein expression system, as a vaccine vector, and as an oncolytic agent. The ubiquitous use of vaccinia viruses in laboratories around the world raises certain safety concerns because the virus can be a pathogen in individuals with immunological and dermatological abnormalities, and on occasion can cause serious problems in normal hosts. This chapter reviews standard operating procedures when working with vaccinia virus and reviews published cases of accidental laboratory infections with poxviruses.

Field evaluation of a novel oral reservoir-targeted vaccine against Borrelia burgdorferi utilizing an inactivated whole-cell bacterial antigen expression vehicle

Blacklegged ticks (Ixodes scapularis) are the principal vector for Borrelia burgdorferi, among other infectious agents, in the northeastern, mid-Atlantic, and upper midwestern USA. White-footed mice (Peromyscus leucopus) are the primary and most competent reservoir host of B. burgdorferi in the Northeast. Live reservoir-targeted vaccines (RTVs) to limit enzootic transmission of B. burgdorferi were previously developed and successfully evaluated in laboratory and controlled field trials. A novel, inactivated RTV was developed to minimize regulatory and market challenges facing previous RTVs based on live bacterial or viral vehicles. Thirty-two residential properties in Redding, Connecticut, participated in a field trial of an orally delivered, inactivated RTV efficacy study (2015-2016). During the two-year vaccination period, a significant decrease in the percentage of B. burgdorferi-infected I. scapularis larvae parasitizing P. leucopus was observed, as was a significant reduction in the percentage of infected P. leucopus on RTV-treated properties when compared to control properties. This novel inactivated RTV was effective in reducing numbers of B. burgdorferi-infected I. scapularis and B. burgdorferi-infected P. leucopus on properties where it was distributed.

An oral bait vaccination approach for the Tasmanian devil facial tumor diseases

Introduction: The Tasmanian devil (Sarcophilus harrisii) is the largest extant carnivorous marsupial. Since 1996, its population has declined by 77% primarily due to a clonal transmissible tumor, known as devil facial tumor (DFT1) disease. In 2014, a second transmissible devil facial tumor (DFT2) was discovered. DFT1 and DFT2 are nearly 100% fatal.Areas covered: We review DFT control approaches and propose a rabies-style oral bait vaccine (OBV) platform for DFTs. This approach has an extensive safety record and was a primary tool in large-scale rabies virus elimination from wild carnivores across diverse landscapes. Like rabies virus, DFTs are transmitted by oral contact, so immunizing the oral cavity and stimulating resident memory cells could be advantageous. Additionally, exposing infected devils that already have tumors to OBVs could serve as an oncolytic virus immunotherapy. The primary challenges may be identifying appropriate DFT-specific antigens and optimization of field delivery methods.Expert opinion: DFT2 is currently found on a peninsula in southern Tasmania, so an OBV that could eliminate DFT2 should be the priority for this vaccine approach. Translation of an OBV approach to control DFTs will be challenging, but the approach is feasible for combatting ongoing and future disease threats.

New human rabies vaccines in the pipeline

Rabies remains endemic in more than 150 countries. In 99% of human cases, rabies virus is transmitted by dogs. The disease, which is nearly always fatal, is preventable by vaccines given either before and/or after exposure to a rabid animal. Numerous factors including the high cost of vaccines, the relative complexity of post-exposure vaccination protocols requiring multiple doses of vaccine, which in cases of severe exposure have to be combined with a rabies immune globulin, lack of access to health care, and insufficient surveillance contribute to the estimated 59,000 human deaths caused by rabies each year. New, less expensive and more immunogenic rabies vaccines are needed together with improved surveillance and dog rabies control to reduce the death toll of human rabies. Here, we discuss new rabies vaccines that are in clinical and pre-clinical testing and evaluate their potential to replace current vaccines.

Comparison of Reverse Transcription Loop-Mediated Isothermal Amplification Method with SYBR Green Real-Time RT-PCR and Direct Fluorescent Antibody Test for Diagnosis of Rabies

Rabies as an endemic disease in most Asian and African countries, especially in remote areas, and requires a reliable diagnostic method. This study aimed to develop a reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for rapid detection of rabies virus RNA in the brain samples, compared to SYBR Green real time RT-PCR test as a molecular technique and direct fluorescent antibody test as a serological method. In this study, RT-LAMP was developed to diagnose rabies. Six primers were designed based on the nucleoprotein (N) of rabies virus. The sensitivity and specificity of SYBR Green real-time RT-PCR and RT-LAMP methods were also determined.RT-LAMP was optimized at 58 ℃ for 60 min. The sensitivity and specificity of RT-LAMP and SYBR Green real-time RT-PCR were 91.2% and 84.2%, and 94.12% and 88.9%, respectively. The slight difference between the sensitivity and specificity of RT-LAMP and that of SYBR Green Real-Time RT-PCR demonstrated that RT-LAMP could be used as a reliable and cost-effective method for the diagnosis of rabies.

ONRAB® oral rabies vaccine is shed from, but does not persist in, captive mammals

ONRAB® is a human adenovirus rabies glycoprotein recombinant vaccine developed to control rabies in wildlife. To support licensing and widespread use of the vaccine, safety studies are needed to assess its potential residual impact on wildlife populations. We examined the persistence of the ONRAB® vaccine virus in captive rabies vector and non-target mammals. This research complements work on important rabies vector species (raccoon, striped skunk, and red fox) but also adds to previous findings with the addition of some non-target species (Virginia opossum, Norway rats, and cotton rats) and a prolonged period of post vaccination monitoring (41 days). Animals were directly inoculated orally with the vaccine and vaccine shedding was monitored using quantitative real-time PCR applied to oral and rectal swabs. ONRAB® DNA was detected in both oral and rectal swabs from 6 h to 3 days post-inoculation in most animals, followed by a resurgence of shedding between days 17 and 34 in some species. Overall, the duration over which ONRAB® DNA was detectable was shorter for non-target mammals, and by day 41, no animal had detectable DNA in either oral or rectal swabs. All target species, as well as cotton rats and laboratory-bred Norway rats, developed robust humoral immune responses as measured by competitive ELISA, with all individuals being seropositive at day 31. Similarly, opossums showed good response (89% seropositive; 8/9), whereas only one of nine wild caught Norway rats was seropositive at day 31. These results support findings of other safety studies suggesting that ONRAB® does not persist in vector and non-target mammals exposed to the vaccine. As such, we interpret these data to reflect a low risk of adverse effects to wild populations following distribution of ONRAB® to control sylvatic rabies.

New Rabies Vaccines for Use in Humans

Although vaccines are available, rabies still claims more than 55,000 human lives each year. In most cases, rabies vaccines are given to humans after their exposure to a rabid animal; pre-exposure vaccination is largely reserved for humans at high risk for contacts with the virus. Most cases of human rabies are transmitted by dogs. Dog rabies control by mass canine vaccination campaigns combined with intensive surveillance programs has led to a decline of human rabies in many countries but has been unsuccessful in others. Animal vaccination programs are also not suited to control human rabies caused by bat transmission, which is common in some Central American countries. Alternatively, or in addition, more widespread pre-exposure vaccination, especially in highly endemic remote areas, could be implemented. With the multiple dose regimens of current vaccines, pre-exposure vaccination is not cost effective for most countries and this warrants the development of new rabies vaccines, which are as safe as current vaccines, but achieve protective immunity after a single dose, and most importantly, are less costly. This chapter discusses novel rabies vaccines that are in late stage pre-clinical testing or have undergone clinical testing and their potential for replacing current vaccines.

Environmental distribution of certain modified live-virus vaccines with a high safety profile presents a low-risk, high-reward to control zoonotic diseases

Oral vaccines aid immunization of hard to reach animal populations but often contain live-attenuated viruses that pose risks of reversion to virulence or residual pathogenicity. Human risk assessment is crucial prior to vaccine field distribution but there is currently no standardized approach. We mapped exposure pathways by which distribution of oral vaccines may result in inoculation into people and applied a Markov chain to estimate the number of severe adverse events. We simulated three oral rabies vaccination (ORV) campaigns: (1) first generation ORV (SAD-B19) in foxes, (2) SAD-B19 in dogs, and (3) third generation ORV (SPBN GASGAS) in dogs. The risk of SAD-B19-associated human deaths was predicted to be low (0.18 per 10 million baits, 95% CI: 0.08, 0.36) when distributed to foxes, but, consistent with international concern, 19 times greater (3.35 per 10 million baits, 95% CI: 2.83, 3.98) when distributed to dogs. We simulated no deaths from SPBN GAS-GAS. Human deaths during dog campaigns were particularly sensitive to dog bite rate, and during wildlife campaigns to animal consumption rate and human contact rate with unconsumed baits. This model highlights the safety of third generation rabies vaccines and serves as a platform for standardized approaches to inform risk assessments.

Field Studies Evaluating Bait Acceptance and Handling by Free-Roaming Dogs in Thailand

(1) Background: As part of the ongoing endeavor to eliminate dog-mediated human rabies in Thailand, renewed interest has been shown in oral vaccination of dogs as a supplementary tool to increase vaccination coverage of the dog population. (2) Methods: Three different bait types were tested using a hand-out model on the campus of the Kasetsart University and the surrounding temples in Thailand during September 2017, consisting of two industrial manufactured baits (fish meal and egg-flavored) and one bait made from local material (boiled pig intestine placed in collagen casing). A PVC-capsule containing dyed water was inserted in the bait. (3) Results: The fishmeal bait was significantly less often accepted and consumed (50.29%) than the other two baits (intestine bait—79.19%; egg bait—78.77%). Delivery and release of the dyed water in the oral cavity was highest in the egg-flavored bait (84.50%), followed by the intestine bait (76.61%) and fishmeal (54.85%) baits. Bait acceptance was influenced by sex, age, and body size of the dog. Also, the origin of the dogs had a significant effect: temple dogs accepted the baits more often than street dogs. (4) Conclusion: A significant portion of the free-roaming dog population in this study can be vaccinated by offering vaccine baits.

MALT1 Controls Attenuated Rabies Virus by Inducing Early Inflammation and T Cell Activation in the Brain

MALT1 is involved in the activation of immune responses, as well as in the proliferation and survival of certain cancer cells. MALT1 acts as a scaffold protein for NF-κB signaling and a cysteine protease that cleaves substrates, further promoting the expression of immunoregulatory genes. Deregulated MALT1 activity has been associated with autoimmunity and cancer, implicating MALT1 as a new therapeutic target. Although MALT1 deficiency has been shown to protect against experimental autoimmune encephalomyelitis, nothing is known about the impact of MALT1 on virus infection in the central nervous system. Here, we studied infection with an attenuated rabies virus, Evelyn-Rotnycki-Abelseth (ERA) virus, and observed increased susceptibility with ERA virus in MALT1^−/− mice. Indeed, after intranasal infection with ERA virus, wild-type mice developed mild transient clinical signs with recovery at 35 days postinoculation (dpi). Interestingly, MALT1^−/− mice developed severe disease requiring euthanasia at around 17 dpi. A decreased induction of inflammatory gene expression and cell infiltration and activation was observed in MALT1^−/− mice at 10 dpi compared to MALT1^+/+ infected mice. At 17 dpi, however, the level of inflammatory cell activation was comparable to that observed in MALT1^+/+ mice. Moreover, MALT1^−/− mice failed to produce virus-neutralizing antibodies. Similar results were obtained with specific inactivation of MALT1 in T cells. Finally, treatment of wild-type mice with mepazine, a MALT1 protease inhibitor, also led to mortality upon ERA virus infection. These data emphasize the importance of early inflammation and activation of T cells through MALT1 for controlling the virulence of an attenuated rabies virus in the brain.

IMPORTANCE Rabies virus is a neurotropic virus which can infect any mammal. Annually, 59,000 people die from rabies. Effective therapy is lacking and hampered by gaps in the understanding of virus pathogenicity. MALT1 is an intracellular protein involved in innate and adaptive immunity and is an interesting therapeutic target because MALT1-deregulated activity has been associated with autoimmunity and cancers. The role of MALT1 in viral infection is, however, largely unknown. Here, we study the impact of MALT1 on virus infection in the brain, using the attenuated ERA rabies virus in different models of MALT1-deficient mice. We reveal the importance of MALT1-mediated inflammation and T cell activation to control ERA virus, providing new insights in the biology of MALT1 and rabies virus infection.

Computational design of potential siRNA molecules for silencing nucleoprotein gene of rabies virus

Aim: Rabies virus infections are a global threat to human and animal health, yet no progressive curative therapy has been developed. In this study, the nucleoprotein gene of rabies virus which is responsible for viral infection was used as a target to design our desired siRNA. Methods: The conserved regions were analyzed by doing alignment of sequences from different strains. Subsequently, different computational tools were used for designing and validation of siRNA molecules. Results: We identified four probable siRNA molecules from twelve different strains of rabies virus which may silence the nucleoprotein gene and inhibit the multiplication of the virus. Conclusion: Our study may help to take an effective therapeutic approach against rabies virus and lead to better control of rabies in humans.

An assessment of shedding with the oral rabies virus vaccine strain SPBN GASGAS in target and non-target species

A safety requirement for live vaccines is investigating possible shedding in recipients since the presence of replication competent vaccine in secretions could result in direct and indirect horizontal transmission. This is especially relevant for oral rabies vaccine baits that are deliberately distributed into the environment. In the current study, survival of an oral rabies virus vaccine, SPBN GASGAS, was examined in excretions from different target and non-target species; red fox, raccoon dog, small Indian mongoose, raccoon, striped skunk, domestic dog, domestic cat and domestic pig. Saliva - and (pooled) fecal samples collected at different time points after oral administration of the vaccine strain were examined for the presence of viral RNA (rt-PCR). All PCR-positive and a subset of PCR-negative samples were subsequently investigated for the presence of infectious virus by isolation in cell culture (RTCIT). Up to 7 days post vaccine administration viral RNA could be detected in 50 of 758 fecal samples but no infectious virus was detected in any of the examined PCR-positive fecal samples. In contrast, RNA-fragments were detected in 248 of 1053 saliva swabs for an extended period (up to 10 days) after vaccine administration, but viable virus was only present during the first hours post vaccine administration in 38 samples. No infectious vaccine virus was isolated in saliva swabs taken 24 h or more after vaccine administration. Hence, no active shedding of the vaccine virus SPBN GASGAS after oral administration occurred and the virus isolated during the initial hours was material originally administered and not a result of virus replication within the host. Thus, potential horizontal transmission of this vaccine virus is limited to a short period directly after vaccine bait uptake. It can be concluded that the environmental risks associated with shedding after distributing vaccine baits containing SPBN GASGAS are negligible.

Development of molecular confirmation tools for swift and easy rabies diagnostics

BACKGROUND

As rabies still represents a major public threat with tens of thousands of deaths per year, particularly in developing countries, adequate surveillance based on rapid and reliable rabies diagnosis for both humans and animals is essential. Rabies diagnosis relies on highly sensitive and specific laboratory tests for detection of viral antigens. Among those tests, at present the immunofluorescence antibody test is the "gold standard test" for rabies diagnosis, followed by virus isolation in either mice or cell culture. Because of the advantages of molecular assays in terms of sensitivity and applicability their approval as confirmatory diagnostic test by international organizations (OIE, WHO) is envisaged. Therefore, the objective was to develop and validate novel molecular assays and RNA extraction methods for rabies that reduce the turnaround time but remain highly sensitive and specific.

METHODS

Here, novel assays, i.e. HighSpeed RT-qPCR and isothermal recombinase polymerase amplification (RPA) were designed and tested. Furthermore, three magnetic bead-based rapid extraction methods for manual or automated extraction were validated and combined with the new downstream assays.

RESULTS

While the conventional column based RNA extraction method showed the highest intra-run variations, all magnetic bead-based rapid extraction methods delivered nearly comparable sensitivity and efficiency of RNA recovery. All newly developed molecular tests were able to detect different rabies virus strains in a markedly reduced timeframe in comparison to the standard diagnostic assays. The observed detection limit for the HighSpeed RT-qPCR was 10 genome copies per reaction, and 1000 genome copies per reaction for the RPA assay.

CONCLUSION

Magnetic bead-based rapid RNA extraction methods are highly sensitive and show a high level of reproducibility and therefore, are particularly suitable for molecular diagnostic assays including rabies. In addition, with a detection limit of 10 genome copies per reaction, the HighSpeed RT-qPCR is suitable for rapid ante mortem rabies diagnosis in humans as well as confirmatory test in integrated bite management and subsequent post-exposure prophylaxis.

Oral vaccination of wildlife using a vaccinia-rabies-glycoprotein recombinant virus vaccine (RABORAL V-RG®): a global review

RABORAL V-RG® is an oral rabies vaccine bait that contains an attenuated ("modified-live") recombinant vaccinia virus vector vaccine expressing the rabies virus glycoprotein gene (V-RG). Approximately 250 million doses have been distributed globally since 1987 without any reports of adverse reactions in wildlife or domestic animals since the first licensed recombinant oral rabies vaccine (ORV) was released into the environment to immunize wildlife populations against rabies. V-RG is genetically stable, is not detected in the oral cavity beyond 48 h after ingestion, is not shed by vaccinates into the environment, and has been tested for thermostability under a range of laboratory and field conditions. Safety of V-RG has been evaluated in over 50 vertebrate species, including non-human primates, with no adverse effects observed regardless of route or dose. Immunogenicity and efficacy have been demonstrated under laboratory and field conditions in multiple target species (including fox, raccoon, coyote, skunk, raccoon dog, and jackal). The liquid vaccine is packaged inside edible baits (i.e., RABORAL V-RG, the vaccine-bait product) which are distributed into wildlife habitats for consumption by target species. Field application of RABORAL V-RG has contributed to the elimination of wildlife rabies from three European countries (Belgium, France and Luxembourg) and of the dog/coyote rabies virus variant from the United States of America (USA). An oral rabies vaccination program in west-central Texas has essentially eliminated the gray fox rabies virus variant from Texas with the last case reported in a cow during 2009. A long-term ORV barrier program in the USA using RABORAL V-RG is preventing substantial geographic expansion of the raccoon rabies virus variant. RABORAL V-RG has also been used to control wildlife rabies in Israel for more than a decade. This paper: (1) reviews the development and historical use of RABORAL V-RG; (2) highlights wildlife rabies control programs using the vaccine in multiple species and countries; and (3) discusses current and future challenges faced by programs seeking to control or eliminate wildlife rabies.

Flagellin FljB as an adjuvant to the recombinant adenovirus rabies glycoprotein vaccine increases immune responses against rabies in mice

Rabies virus (RABV) causes an acute progressive viral encephalitis. Although currently licensed vaccines have an excellent safety and efficacy record, the development of a safer and more cost-effective vaccine is still being sought. An E1-deleted, replication-defective human adenovirus type 5 (HAd5) vector expressing RABV glycoprotein (HAd5-G) is thought to be a promising candidate vaccine for immune prophylaxis against rabies. Salmonella enterica serovar Typhimurium (S. Typhimurium) flagellin is a well-known immune adjuvant. In this work, we have researched the adjuvant effect of flagellins (FljB and FliC) for HAd5 in mice for the first time. We found that the recombinant HAd5 expressing RABV glycoprotein and FljB (HAd5-GB), if administered intramuscularly, but not orally, could induce stronger immune responses and provide better protection against rabies than HAd5-G or the recombinant HAd5 expressing glycoprotein and FliC (HAd5-GC). These results suggest that the recombinant HAd5-GB has potential for development as a promising rabies vaccine.

Rabies Control and Treatment: From Prophylaxis to Strategies with Curative Potential

Rabies is an acute, fatal, neurological disease that affects almost all kinds of mammals. Vaccination (using an inactivated rabies vaccine), combined with administration of rabies immune globulin, is the only approved, effective method for post-exposure prophylaxis against rabies in humans. In the search for novel rabies control and treatment strategies, live-attenuated viruses have recently emerged as a practical and promising approach for immunizing and controlling rabies. Unlike the conventional, inactivated rabies vaccine, live-attenuated viruses are genetically modified viruses that are able to replicate in an inoculated recipient without causing adverse effects, while still eliciting robust and effective immune responses against rabies virus infection. A number of viruses with an intrinsic capacity that could be used as putative candidates for live-attenuated rabies vaccine have been intensively evaluated for therapeutic purposes. Additional novel strategies, such as a monoclonal antibody-based approach, nucleic acid-based vaccines, or small interfering RNAs (siRNAs) interfering with virus replication, could further add to the arena of strategies to combat rabies. In this review, we highlight current advances in rabies therapy and discuss the role that they might have in the future of rabies treatment. Given the pronounced and complex impact of rabies on a patient, a combination of these novel modalities has the potential to achieve maximal anti-rabies efficacy, or may even have promising curative effects in the future. However, several hurdles regarding clinical safety considerations and public awareness should be overcome before these approaches can ultimately become clinically relevant therapies.

Recombinant rabies virus expressing dog GM-CSF is an efficacious oral rabies vaccine for dogs

Developing efficacious oral rabies vaccines is an important step to increase immunization coverage for stray dogs, which are not accessible for parenteral vaccination. Our previous studies have demonstrated that recombinant rabies virus (RABV) expressing cytokines/chemokines induces robust protective immune responses after oral immunization in mice by recruiting and activating dendritic cells (DCs) and B cells. To develop an effective oral rabies vaccine for dogs, a recombinant attenuated RABV expressing dog GM-CSF, designated as LBNSE-dGM-CSF was constructed and used for oral vaccination in a dog model. Significantly more DCs or B cells were activated in the peripheral blood of dogs vaccinated orally with LBNSE-dGM-CSF than those vaccinated with the parent virus LBNSE, particularly at 3 days post immunization (dpi). As a result, significantly higher levels of virus neutralizing antibodies (VNAs) were detected in dogs immunized with LBNSE-dGM-CSF than with the parent virus. All the immunized dogs were protected against a lethal challenge with 4500 MICLD₅₀ of wild-type RABV SXTYD01. LBNSE-dGM-CSF was found to replicate mainly in the tonsils after oral vaccination as detected by nested RT-PCR and immunohistochemistry. Taken together, our results indicate that LBNSE-dGM-CSF could be a promising oral rabies vaccine candidate for dogs.

Live-vaccinia virus encapsulation in pH-sensitive polymer increases safety of a reservoir-targeted Lyme disease vaccine by targeting gastrointestinal release

The incidence of Lyme disease has continued to rise despite attempts to control its spread. Vaccination of zoonotic reservoirs of human pathogens has been successfully used to decrease the incidence of rabies in raccoons and foxes. We have previously reported on the efficacy of a vaccinia virus vectored vaccine to reduce carriage of Borrelia burgdorferi in reservoir mice and ticks. One potential drawback to vaccinia virus vectored vaccines is the risk of accidental infection of humans. To reduce this risk, we developed a process to encapsulate vaccinia virus with a pH-sensitive polymer that inactivates the virus until it is ingested and dissolved by stomach acids. We demonstrate that the vaccine is inactive both in vitro and in vivo until it is released from the polymer. Once released from the polymer by contact with an acidic pH solution, the virus regains infectivity. Vaccination with coated vaccinia virus confers protection against B. burgdorferi infection and reduction in acquisition of the pathogen by naïve feeding ticks.

Safety and immunogenicity of recombinant rabies virus (ERAGS) in mice and raccoon dogs

Purpose

The development of a genetically modified live rabies vaccine applicable to wild raccoon dogs is necessary for the eradication of rabies in Korea. Thus, we constructed a recombinant rabies virus (RABV) called the ERAGS strain, using a reverse genetic system and evaluated its safety and efficacy in mice and its safety and immunogenicity in raccoon dogs.

Materials and Methods

ERAGS, which has Asn194Ser and Arg333Glu substitutions in the glycoprotein, was constructed using site-directed mutagenesis. Mice were inoculated with the ERAGS strain (either 10^5.0 or 10^7.0 FAID₅₀/mL) via intramuscular (IM) or intracranial injections and then challenged with a virulent RABV. Raccoon dogs were administered the ERAGS strain (10^8.0 FAID₅₀/mL) either orally or via the IM route and the immunogenicity of the strain was evaluated using fluorescent antibody virus neutralization tests.

Results

The ERAGS strain inoculated into murine neuroblastoma cells reached 10^7.8 FAID₅₀/mL at 96-hour post-inoculation. The virus was not pathogenic and induced complete protection from virulent RABV in immunized 4- and 6-week-old mice. Korean raccoon dogs immunized with the ERAGS strain via IM or oral route were also safe from the virus and developed high titer levels (26.4-32.8 IU/mL) of virus-neutralizing antibody (VNA) at 4 weeks post-inoculation.

Conclusion

The ERAGS RABV strain was effectively protective against rabies in mice and produced a high VNA titer in raccoon dogs.

Application of recombinant adenoviruses expressing glycoprotein or nucleoprotein of rabies virus to Korean raccoon dogs

Purpose

A new rabies vaccine for animals, including raccoon dogs, in Korea is needed to eradicate rabies infection. In this study, we constructed two recombinant adenoviruses expressing the glycoprotein or nucleoprotein of the rabies virus (RABV). We then investigated the safety and immunogenicity of these strains in raccoon dogs, depending on inoculation route.

Materials and Methods

Recombinant adenoviruses expressing the glycoprotein (Ad-0910G) or nucleoprotein (Ad-0910N) of rabies were constructed in 293A cells using an adenoviral system. One-year-old raccoon dogs underwent intramuscular (IM) inoculation or oral administration of the recombinant Ad-0910G and Ad-0910N. Clinical symptoms were observed and virus-neutralizing antibodies (VNA) against RABV were measured at 0, 2, 4, and 6 weeks after the immunization. Raccoons were considered positive if VNA titers were ≥ 0.1 IU/mL.

Results

Raccoon dogs inoculated with the combined Ad-0910G and Ad-0910N virus via the IM route did not exhibit any clinical sign of rabies during the observation period. All raccoon dogs (n = 7) immunized IM had high VNA titers, ranging from 0.17 to 41.6 IU/mL at 2 weeks after inoculation, but 70% (7/10) of raccoon dogs administered viruses via the oral route responded by 6 weeks after administration against RABV.

Conclusion

Raccoon dogs inoculated with Ad-0910G and Ad-0910N viruses showed no adverse effects. Immunization with the combined Ad-0910G and Ad-0910N strains may play an important role in inducing VNA against RABV in raccoon dogs.

Novel Approaches to the Prevention and Treatment of Rabies

Rabies is a highly lethal disease caused by the neurotropic rabies virus (RABV), and it remains an important public health problem globally. Effective vaccines have been developed for pre- and post-exposure prophylaxis (PEP). PEP is only effective if it is initiated promptly after recognizing exposure. Once neurological symptoms develop, however, it is widely accepted that there is no effective treatment available. Recent studies indicate that the presence of RABV-specific immunity (i.e. Virus neutralizing antibodies, VNA) and the transient enhancement of the BBB permeability are absolutely required for effective virus clearance from the CNS. In principle, it has been shown in mice using various live-attenuated RABVs or recombinant RABVs expressing three copies of the G or expressing chemokine/cytokines, which can induce high levels of VNA in the serum and also capable of transiently enhancing the BBB permeability that it is possible to clear the virus from CNS. Also, it has been demonstrated that, intravenous administration of VNA together with MCP-1 (shown to transiently open up BBB) can clear RABV from the CNS in both immunocompetent and immunocompromised mice, as late as 5 days after lethal challenge. Novel therapeutic approaches aimed at allowing the peripheral VNA to cross the BBB by administration of the VNA in combination with biological or chemical agents that can transiently open up the BBB would be useful to establish an effective therapy for rabies in humans. In this review, we focus on the some of the approaches that can be used to meet the challenges in the field of rabies treatment.

Oral immunization of mice with recombinant rabies vaccine strain (ERAG3G) induces complete protection

PURPOSE

New rabies vaccine bait for both pets and raccoon dogs residing in Korea is needed to eradicate rabies infection among animals. In this study, we constructed a recombinant rabies virus (RABV), the ERAG3G strain, using a reverse genetics system. Then we investigated the efficacy of this strain in mice after oral administration and the safety of this strain in cats after intramuscular administration.

MATERIALS AND METHODS

The ERAG3G strain was rescued in BHK/T7-9 cells using the full-length genome mutated at the amino acid position 333 of the glycoprotein gene of RABV and helper plasmids. Four-week-old mice underwent one or two oral administrations of the ERAG3G strain and were challenged with the highly virulent RABV strain CVSN2c 14 days after the second administration. Clinical symptoms were observed and body weights were measured every day after the challenge.

RESULTS

All mice showed complete protection against virulent RABV. In addition, cats intramuscularly inoculated with the ERAG3G strain showed high antibody titers ranging from 2.62 to 23.9 IU/mL at 28-day postinoculation.

CONCLUSION

The oral immunization of the ERAG3G strain plays an important role in conferring complete protection in mice, and intramuscular inoculation of the ERAG3G strain induces the formation of anti-rabies neutralizing antibody in cats.

A single immunization with recombinant rabies virus (ERAG3G) confers complete protection against rabies in mice

Purpose

New alternative bait rabies vaccines applicable to pet dogs and wild animals are needed to eradicate rabies in Korea. In this study, recombinant rabies virus, ERAG3G strain was constructed using reverse genetic system and the safety, efficacy and immunogenicity of the ERAG3G strain was evaluated in mice and dogs.

Materials and Methods

Using the full-length genome mutated amino acid at position 333 of glycoprotein of rabies virus (RABV) and helper plasmids, the ERAG3G strain was rescued in BHK/T7-9 cells successfully. Mice were inoculated with the ERAG3G strain for safety and efficacy. Safety and immunogenicity of the dog inoculated with the ERAG3G strain (1 mL, 10^8.0 FAID₅₀/mL) via intramuscular route was evaluated for 28 days after inoculation.

Results

The ERAG3G strain rescued by reverse genetic system was propagated well in the mouse neuroblastoma cells revealing titer of 10^8.5 FAID₅₀/mL and was not pathogenic to 4- or 6-week-old mice that received by intramuscular or intracranical route. Immunization with the ERAG3G strain conferred complete protection from lethal RABV in mice. Dogs inoculated with the vaccine candidate via intramuscular route showed high neutralizing antibody titer ranging from 2.62 to 23.9 IU/mL at 28 days postinoculation.

Conclusion

Our findings suggest that the ERAG3G strain plays an important role in inducing protective efficacy in mice and causes to arise anti-rabies neutralizing antibody in dogs.

Current and future trends in the prevention, treatment and control of rabies

Rabies remains a global zoonosis of major public health, agricultural and economic significance. Dogs are the major animal reservoirs in developing regions, wildlife maintain cycles of infection even in developed countries and new viral etiological agents continue to emerge. Nearly all human rabies cases are related directly to animal bite and thus, primary disease prevention requires minimization of suspected exposures. Once exposure occurs, modern prophylaxis entails immediate wound care, local infiltration of rabies immune globulin and parenteral administration of modern cell culture vaccines in multiple doses. Pre-exposure vaccination should occur in selected population groups at risk of occupational exposure. Historically, survival from fatal rabies by at least five human patients, vaccinated prior to the onset of clinical signs, signaled initial optimism as to the theoretical utility of medical intervention. Recently, the heroic recovery of an unvaccinated teenager from clinical rabies offers hope of future specific therapy. Canine rabies elimination is the key towards ultimate reduction of the disease burden, as first illustrated in developed countries. Implementation of oral vaccination in free-ranging carnivore hosts demonstrates the feasibility of disease abatement in particular wildlife populations, such as demonstrated in Europe and North America, with an enhanced need for application to developing countries in the Americas, Africa and Eurasia.

Vaccines for lyssaviruses other than rabies

Several new lyssaviruses have emerged in the past decade and it is likely that more remain to be discovered. There are six recognized genotypes of lyssavirus other than the rabies virus (genotype 1). All but one of these has been associated with human cases, with the resulting disease clinically similar to rabies. Rabies vaccines provide a means of pre- and postexposure prophylaxis against rabies and some of the other genotypes, but not all. Those that are crossprotected fall into phylogroup 1 of the genus, and those not protected in phylogroup 2. The crossprotection of phylogroup 1 viruses by rabies vaccines and the development of new, broader range or specific vaccines for phylogroup 2 viruses are reviewed.

High prevalence of antibodies against canine adenovirus (CAV) type 2 in domestic dog populations in South Africa precludes the use of CAV-based recombinant rabies vaccines

Rabies in dogs can be controlled through mass vaccination. Oral vaccination of domestic dogs would be useful in the developing world, where greater vaccination coverage is needed especially in inaccessible areas or places with large numbers of free-roaming dogs. From this perspective, recent research has focused on development of new recombinant vaccines that can be administered orally in a bait to be used as adjunct for parenteral vaccination. One such candidate, a recombinant canine adenovirus type 2 vaccine expressing the rabies virus glycoprotein (CAV2-RG), is considered a promising option for dogs, given host specificity and safety. To assess the potential use of this vaccine in domestic dog populations, we investigated the prevalence of antibodies against canine adenovirus type 2 in South African dogs. Blood was collected from 241 dogs from the Gauteng and KwaZulu-Natal provinces. Sampled dogs had not previously been vaccinated against canine adenovirus type 1 (CAV1) or canine adenovirus type 2 (CAV2). Animals from both provinces had a high percentage of seropositivity (45% and 62%), suggesting that CAV2 circulates extensively among domestic dog populations in South Africa. Given this finding, we evaluated the effect of pre-existing CAV-specific antibodies on the efficacy of the CAV2-RG vaccine delivered via the oral route in dogs. Purpose-bred Beagle dogs, which received prior vaccination against canine parvovirus, canine distemper virus and CAV, were immunized by oral administration of CAV2-RG. After rabies virus (RABV) infection all animals, except one vaccinated dog, developed rabies. This study demonstrated that pre-existing antibodies against CAV, such as naturally occurs in South African dogs, inhibits the development of neutralizing antibodies against RABV when immunized with a CAV-based rabies recombinant vaccine.

Safety study of the Bio-10-SAD Bern strain of the rabies virus on the rhesus macaque monkey species

Based on a WHO recommendation, residual pathogenicity of the Bio-10-SAD Bern rabies virus strain (component of the Lysvulpen por. ad us. vet. vaccine) was tested on rhesus macaque monkeys. Each of the ten monkeys, females, two years old, was administered orally 2 ml × 109 TCID50 of the Bio-10-SAD Bern rabies strain. The animals were monitored for 90 days. Subsequently, the animals were sacrificed and their brains were examined for presence of the vaccination rabies virus by the immunofluorescence and PCR methods. The occurrence of anti-rabies antibodies prior to and following administration of the vaccination rabies virus was also evaluated. No clinical signs of rabies were observed nor did any of the animals die of rabies following application of the virus. No rabies was detected in the study animals by post mortem examination. All of the 10 animals developed anti-rabies antibodies during the 90 days following administration of the rabies virus. It can be concluded, that Bio-10-SAD Bern virus administered at a dose equal to the tenfold maximum dose specified for field uses is safe to monkeys of the rhesus macaque species. This study is the first of its type performed in rhesus macaque monkey species.

Recombinant rabies viruses expressing GM-CSF or flagellin are effective vaccines for both intramuscular and oral immunizations

Our previous studies indicated that recombinant rabies viruses (rRABV) expressing chemokines or cytokines (including GM-CSF) could enhance the immunogenicity by recruiting and/or activating dendritic cells (DC). In this study, bacterial flagellin was cloned into the RABV genome and recombinant virus LBNSE-Flagellin was rescued. To compare the immunogenicity of LBNSE-Flagellin with recombinant virus expressing GMCSF (LBNSE-GMCSF), mice were immunized with each of these rRABVs by intramuscular (i.m.) or oral route. The parent virus (LBNSE) without expression of any foreign molecules was included for comparison. The i.m.-immunized mice were bled at three weeks after the immunization for the measurement of virus neutralizing antibody (VNA) and then challenged with 50 LD50 challenge virus standard (CVS-24). Orally immunized mice were boosted after three weeks and then bled and challenged one week after the booster immunization. It was found that both LBNSE-GMCSF and LBNSE-Flagellin recruited/activated more DCs and B cells in the periphery, stimulated higher levels of adaptive immune responses (VNA), and protected more mice against challenge infection than the parent virus LBNSE in both the i.m. and the orally immunized groups. Together, these studies suggest that recombinant RABV expressing GM-CSF or flagellin are more immunogenic than the parent virus in both i.m. and oral immunizations.

Reductions in human Lyme disease risk due to the effects of oral vaccination on tick-to-mouse and mouse-to-tick transmission

Vaccinating wildlife is becoming an increasingly popular method to reduce human disease risks from pathogens such as Borrelia burgdorferi, the causative agent of Lyme disease. To successfully limit human disease risk, vaccines targeting the wildlife reservoirs of B. burgdorferi must be easily distributable and must effectively reduce pathogen transmission from infected animals, given that many animals in nature will be infected prior to vaccination. We assessed the efficacy of an easily distributable oral bait vaccine based on the immunogenic outer surface protein A (OspA) to protect uninfected mice from infection and to reduce transmission from previously infected white-footed mice, an important reservoir host of B. burgdorferi. Oral vaccination of white-footed mice effectively reduces transmission of B. burgdorferi at both critical stages of the Lyme disease transmission cycle. First, oral vaccination of uninfected white-footed mice elicits an immune response that protects mice from B. burgdorferi infection. Second, oral vaccination of previously infected mice significantly reduces the transmission of B. burgdorferi to feeding ticks despite a statistically nonsignificant immune response. We used the estimates of pathogen transmission to and from vaccinated and unvaccinated mice to model the efficacy of an oral vaccination campaign targeting wild white-footed mice. Projection models suggest that the effects of the vaccine on both critical stages of the transmission cycle of B. burgdorferi act synergistically in a positive feedback loop to reduce the nymphal infection prevalence, and thus human Lyme disease risk, well below what would be expected from either effect alone. This study suggests that oral immunization of wildlife with an OspA-based vaccine can be a promising long-term strategy to reduce human Lyme disease risk.

A novel rabies vaccine based on a recombinant parainfluenza virus 5 expressing rabies virus glycoprotein

Untreated rabies virus (RABV) infection leads to death. Vaccine and postexposure treatment have been effective in preventing RABV infection. However, due to cost, rabies vaccination and treatment have not been widely used in developing countries. There are 55,000 human death caused by rabies annually. An efficacious and cost-effective rabies vaccine is needed. Parainfluenza virus 5 (PIV5) is thought to contribute to kennel cough, and kennel cough vaccines containing live PIV5 have been used in dogs for many years. In this work, a PIV5-vectored rabies vaccine was tested in mice. A recombinant PIV5 encoding RABV glycoprotein (G) (rPIV5-RV-G) was administered to mice via intranasal (i.n.), intramuscular (i.m.), and oral inoculation. The vaccinated mice were challenged with a 50% lethal challenge dose (LD(50)) of RABV challenge virus standard 24 (CVS-24) intracerebrally. A single dose of 10(6) PFU of rPIV5-RV-G was sufficient for 100% protection when administered via the i.n. route. The mice vaccinated with a single dose of 10(8) PFU of rPIV5-RV-G via the i.m. route showed very robust protection (90% to 100%). Intriguingly, the mice vaccinated orally with a single dose of 10(8) PFU of rPIV5-RV-G showed a 50% survival rate, which is comparable to the 60% survival rate among mice inoculated with an attenuated rabies vaccine strain, recombinant LBNSE. This is first report of an orally effective rabies vaccine candidate in animals based on PIV5 as a vector. These results indicate that rPIV5-RV-G is an excellent candidate for a new generation of recombinant rabies vaccine for humans and animals and PIV5 is a potential vector for oral vaccines.

A new rabies vaccine based on a recombinant ORF virus (parapoxvirus) expressing the rabies virus glycoprotein

The present study describes the generation of a new Orf virus (ORFV) recombinant, D1701-V-RabG, expressing the rabies virus (RABV) glycoprotein that is correctly presented on the surface of infected cells without the need of replication or production of infectious recombinant virus. One single immunization with recombinant ORFV can stimulate high RABV-specific virus-neutralizing antibody (VNA) titers in mice, cats, and dogs, representing all nonpermissive hosts for the ORFV vector. The protective immune response against severe lethal challenge infection was analyzed in detail in mice using different dosages, numbers, and routes for immunization with the ORFV recombinant. Long-term levels of VNA could be elicited that remained greater than 0.5 IU per ml serum, indicative for the protective status. Single applications of higher doses (10(7) PFU) can be sufficient to confer complete protection against intracranial (i.c.) challenge, whereas booster immunization was needed for protection by the application of lower dosages. Anamnestic immune responses were achieved by each of the seven tested routes of inoculation, including oral application. Finally, in vivo antibody-mediated depletion of CD4-positive and/or CD8-posititve T cell subpopulations during immunization and/or challenge infection attested the importance of CD4 T cells for the induction of protective immunity by D1701-V-RabG. This report demonstrates another example of the potential of the ORFV vector and also indicates the capability of the new recombinant for vaccination of animals.

Trap-vaccinate-release program to control raccoon rabies, New York, USA

In 2009, an outbreak of raccoon rabies in Central Park in New York City, New York, USA, infected 133 raccoons. Five persons and 2 dogs were exposed but did not become infected. A trap-vaccinate-release program vaccinated ≈500 raccoons and contributed to the end of the epizootic.