Christine Fehlner-Gardiner

Development of a mouse monoclonal antibody cocktail for post-exposure rabies prophylaxis in humans.

As the demand for rabies post-exposure prophylaxis (PEP) treatments has increased exponentially in recent years, the limited supply of human and equine rabies immunoglobulin (HRIG and ERIG) has failed to provide the required passive immune component in PEP in countries where canine rabies is endemic. Replacement of HRIG and ERIG with a potentially cheaper and efficacious alternative biological for treatment of rabies in humans, therefore, remains a high priority. In this study, we set out to assess a mouse monoclonal antibody (MoMAb) cocktail with the ultimate goal to develop a product at the lowest possible cost that can be used in developing countries as a replacement for RIG in PEP. Five MoMAbs, E559.9.14, 1112-1, 62-71-3, M727-5-1, and M777-16-3, were selected from available panels based on stringent criteria, such as biological activity, neutralizing potency, binding specificity, spectrum of neutralization of lyssaviruses, and history of each hybridoma. Four of these MoMAbs recognize epitopes in antigenic site II and one recognizes an epitope in antigenic site III on the rabies virus (RABV) glycoprotein, as determined by nucleotide sequence analysis of the glycoprotein gene of unique MoMAb neutralization-escape mutants. The MoMAbs were produced under Good Laboratory Practice (GLP) conditions. Unique combinations (cocktails) were prepared, using different concentrations of the MoMAbs that were capable of targeting non-overlapping epitopes of antigenic sites II and III. Blind in vitro efficacy studies showed the MoMab cocktails neutralized a broad spectrum of lyssaviruses except for lyssaviruses belonging to phylogroups II and III. In vivo, MoMAb cocktails resulted in protection as a component of PEP that was comparable to HRIG. In conclusion, all three novel combinations of MoMAbs were shown to have equal efficacy to HRIG and therefore could be considered a potentially less expensive alternative biological agent for use in PEP and prevention of rabies in humans.

Fatal human rabies due to duvenhage virus from a bat in Kenya: failure of treatment with coma-induction, ketamine, and antiviral drugs.

11Department of Infectious Diseases, Tropical Medicine and AIDS, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands, 2Department ofNeurology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands, 3Department of Intensive Care, Academic Medical Center, University ofAmsterdam, Amsterdam, The Netherlands, 4Department of Clinical Virology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands,5Department of Virology, Erasmus Medical Centre, Rotterdam, The Netherlands, 6Department of Radiology, Academic Medical Center, University of Amsterdam,Amsterdam, The Netherlands, 7Department of Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands, 8Centre of Expertise forRabies, Canadian Food Inspection Agency, Ottawa Laboratory (Fallowfield), Ottawa, Ontario, Canada

ERA VACCINE-DERIVED CASES OF RABIES IN WILDLIFE AND DOMESTIC ANIMALS IN ONTARIO, CANADA, 1989–2004

A vaccination program for the control of terrestrial rabies in the province of Ontario, Canada, began in 1989. During the period between 1989 and 2004, over 13 million baits containing the live, attenuated rabies virus ERA-BHK21 were distributed across the province, with the aim of immunizing foxes by the oral route. Animals recovered from bait distribution areas were assayed by fluorescent antibody test for rabies virus infection. Immunoreactivity with a panel of monoclonal antibodies that discriminate between ERA and rabies virus variants known to circulate in Ontario, and molecular genetic analyses were used to identify animals infected with ERA. Nine cases of ERA variant rabies were identified over the 16-yr period of study; these did not appear to be stratified by species, year of discovery, or location of capture. The ERA-positive animals were found across the province in eight counties, all of which had been baited in the year of case discovery. The nine ERA-positive cases included four red foxes (Vulpes vulpes), two raccoons (Procyon lotor), two striped skunks (Mephitis mephitis), and one bovine calf (Bos taurus). Molecular phylogenetic analyses of the partial N gene sequences generated from these isolates indicated that these nine cases were due to infection with the ERA variant. The glycoprotein sequences were predicted from G gene sequencing of all nine field isolates and two laboratory stock ERA viruses. This revealed some heterogeneity at residue 120 (either arginine or histidine) in both field and laboratory stocks as well as a few other mutations in field isolates. The significance of this heterogeneity remains unclear. Our data demonstrate that the ERA vaccine distributed in Ontario carried residual pathogenicity; however, there does not appear to be any evidence of ERA establishment in wildlife populations over the 16-yr period. These results are consistent with previous reports of the rare detection of ERA vaccine–induced rabies and with laboratory studies of ERA pathogenicity.

Comparing ONRAB® AND RABORAL V-RG® oral rabies vaccine field performance in raccoons and striped skunks, New Brunswick, Canada, and Maine, USA.

Control of rabies in mesocarnivore reservoirs through oral rabies vaccination (ORV) requires an effective vaccine bait. Oral rabies vaccine performance in the field may be affected by a variety of factors, including vaccine bait density and distribution pattern, habitat, target species population density, and the availability of competing foods. A field study in which these covariates were restricted as much as possible was conducted along the international border of the state of Maine (ME), USA, and the province of New Brunswick (NB), Canada, to compare the performance of two oral rabies vaccines in raccoons (Procyon lotor) and striped skunks (Mephitis mephitis). RABORAL V-RG® (vaccinia-rabies glycoprotein recombinant oral vaccine in fishmealcoated sachet) or ONRAB® (adenovirus-rabies glycoprotein recombinant oral vaccine in Ultralite bait matrix) were distributed in ME and NB, respectively, by fixed-wing aircraft at a density of 75 baits/km2 along parallel flight lines spaced 1.0 km apart. Sera were collected from live-trapped raccoons and skunks 5–7 wk post-ORV and assayed to determine antibody prevalence in each area. Duplicate serum samples were provided blind to two different laboratories for analyses by rabies virus serum neutralization assays (at both laboratories) and a competitive enzyme-linked immunosorbent assay (at one laboratory). There was no significant difference in the proportion of antibody-positive animals determined by the three serologic methods, nor was there a significant difference between ONRAB and RABORAL V-RG in the proportion of antibody-positive striped skunks observed post-ORV. In contrast, the proportion of antibody-positive raccoons was significantly higher in the ONRAB- versus the RABORAL V-RG–baited areas (74% vs. 30%; χ2=89.977, df=5, P<0.0001). These data support that ONRAB may serve as an effective tool for raccoon rabies control.

Oral vaccination and protection of striped skunks (Mephitis mephitis) against rabies using ONRAB

Skunks are one of the most important rabies vector species in North America due to their wide geographic distribution, high susceptibility to the rabies virus, and tendency to inhabit areas around human dwellings and domestic animals. Oral vaccination is a cost-effective, socially acceptable technique often used to control rabies in terrestrial wildlife; however, control of rabies in skunks has proven especially challenging due to the lack of a vaccine effective by the oral route in this species. In this study, we examined the antibody response of captive striped skunks (Mephitis mephitis) to ONRAB(®) and tested the protection afforded by the vaccine against rabies virus. Thirty-one skunks were each offered one ONRAB(®) vaccine bait, 25 skunks were administered ONRAB(®) via direct instillation into the oral cavity (DIOC) and ten controls received no vaccine. A blood sample was collected from controls and vaccinates 6 weeks prior to treatment, and then 5 and 7 weeks post-vaccination (PV). A competitive ELISA was used to detect rabies antibody (RAb). Pre-vaccination sera for all skunks, and sera for all controls throughout the serology study, were negative for RAb. Fifty-eight percent (18/31) of skunks in the bait group and 100% (25/25) of skunks that received ONRAB(®) DIOC had detectable RAb by 7 week PV. All 10 controls succumbed to experimental rabies infection. In the group of skunks administered ONRAB(®) DIOC, 100% (23/23) survived challenge 247 days PV. Survival of skunks presented ONRAB(®) baits was 81% (25/31). In the bait group, all 18 skunks that had detectable RAb by 7 week PV survived challenge. Seven additional skunks without detectable RAb prior to week 7 PV also survived. Lack of any remarkable pathology in study animals, together with positive serology and challenge results, supports that ONRAB(®) is a safe and effective oral rabies vaccine for use in skunks.

IMMUNE RESPONSE AND PROTECTION IN RACCOONS (PROCYON LOTOR) FOLLOWING CONSUMPTION OF BAITS CONTAINING ONRAB®, A HUMAN ADENOVIRUS RABIES GLYCOPROTEIN RECOMBINANT VACCINE

We investigated the immune response and protection conferred in raccoons (Procyon lotor) following consumption of ONRAB® oral rabies vaccine baits. Forty-two wild-caught, captive raccoons were each offered an ONRAB vaccine bait; 21 controls received no vaccine baits. Blood samples collected from all raccoons before treatment, and each week posttreatment for 16 wk, were assessed for the presence of rabies virus antibody. In the bait group, an individual was considered to have responded to vaccination if serum samples from three or more consecutive weeks were antibody-positive. Using this criterion, 77% (20/26) of raccoons that consumed ONRAB baits with no observed vaccine spillage (full dose) demonstrated a humoral immune response. In the group that received a partial dose (0.05–0.90 mL vaccine recovered), 50% (8/16) of raccoons responded to vaccination. Regardless of the vaccine dose received, among the 28 raccoons that responded to vaccination 18 had antibody initially detectable at week 2 and 22 remained antibody-positive for at least 10 consecutive weeks. Kinetics of the humoral immune response suggest that the best time to conduct postbaiting surveillance for evidence of vaccination would be 6–13 wk following bait deployment, with the highest antibody prevalence expected between weeks 8–10. A sub-sample of 29 raccoons (20 ONRAB, 9 controls) was challenged with raccoon rabies virus variant 350 days posttreatment. Eight of nine controls (89%) developed rabies whereas 15/20 vaccinates (75%) survived. Survival following rabies challenge was significantly higher in raccoons presented ONRAB vaccine baits.

Oral Rabies Vaccination in Raccoons: Comparison of ONRAB® and RABORAL V-RG® Vaccine-Bait Field Performance in Québec, Canada and Vermont, USA

The control of rabies in raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) in North America has been conducted mainly through aerial distribution of oral vaccine-baits. The effectiveness of the vaccine-bait used is therefore of prime importance for disease eradication. In a previous field comparison between the ONRAB® bait in the province of New Brunswick, Canada, and RABORAL V-RG® bait in the state of Maine, USA, the ONRAB bait produced a higher percentage of antibody-positive raccoons under nearly identical bait distribution for the two vaccines. The main objective of the present study was to conduct a similar cross-border comparison of these two vaccine-baits using raccoon sera collected during post–oral rabies vaccination monitoring in Québec, Canada, and Vermont, USA, where ONRAB and V-RG, respectively, were distributed aerially at a targeted density of 150 baits/km2. A comparison of the equivalency of two serologic tests used in Canada and the USA was also conducted using sera from raccoons and striped skunks. Rabies virus neutralization assay (USA) yielded similar results to the competitive enzyme-linked immunosorbent assay (Canada), with agreement between the two tests of 92% for raccoon sera and 96% for skunk sera. With both assays, the percentage of antibody-positive raccoons was greater with ONRAB (51%, n=265) than with V-RG (38%, n=66). These new results support the conclusion from the previous study, that ONRAB vaccine-baits may be more effective for the control of rabies in raccoons.

Chapter 5 Lyssaviruses—Current Trends

Abstract Various technological developments have revitalized the approaches employed to study the disease of rabies. In particular, reverse genetics has facilitated the generation of novel viruses used to improve our understanding of the fundamental aspects of rabies virus (RABV) biology and pathogenicity and yielded novel constructs potentially useful as vaccines against rabies and other diseases. Other techniques such as high throughput methods to examine the impact of rabies virus infection on host cell gene expression and two hybrid systems to explore detailed protein–protein interactions also contribute substantially to our understanding of virus–host interactions. This review summarizes much of the increased knowledge about rabies that has resulted from such studies but acknowledges that this is still insufficient to allow rational attempts at curing those who present with clinical disease.

Oral vaccination and protection of red foxes (Vulpes vulpes) against rabies using ONRAB®, an adenovirus-rabies recombinant vaccine

Twenty-seven red foxes (Vulpes vulpes) were each offered a bait containing ONRAB, a recombinant oral rabies vaccine that uses a human adenovirus vector to express the immunogenic rabies virus glycoprotein; 10 controls received no vaccine baits. Serum samples collected from all foxes before treatment, and each week post-treatment for 16 weeks, were tested for the presence of rabies virus neutralizing antibody (RVNA). In the bait group, a fox was considered a responder to vaccination if serum samples from 3 or more consecutive weeks had RVNA ≥0.5 IU/ml. Using this criterion, 79% of adult foxes (11/14) and 46% of juveniles (6/13) responded to vaccination with ONRAB. Serum RVNA of adults first tested positive (≥0.5 IU/ml) between weeks 1 and 3, about 4 weeks earlier than in juveniles. Adults also responded with higher levels of RVNA and these levels were maintained longer. Serum samples from juveniles tested positive for 1-4 consecutive weeks; in adults the range was 2-15 weeks, with almost half of adults maintaining titres above 0.5 IU/ml for 9 or more consecutive weeks. Based on the kinetics of the antibody response to ONRAB, the best time to sample sera of wild adult foxes for evidence of vaccination is 7-11 weeks following bait distribution. Thirty-four foxes (25 ONRAB, 9 controls) were challenged with vulpine street virus 547 days post-vaccination. All controls developed rabies whereas eight of 13 adult vaccinates (62%) and four of 12 juvenile vaccinates (33%) survived. All foxes classed as non-responders to vaccination developed rabies. Of foxes considered responders to vaccination, 80% of adults (8/10) and 67% of juveniles (4/6) survived challenge. The duration of immunity conferred to foxes would appear adequate for bi-annual and annual bait distribution schedules as vaccinates were challenged 1.5 years post-vaccination.

ORAL RABIES VACCINATION OF RACCOONS AND STRIPED SKUNKS WITH ONRAB® BAITS: MULTIPLE FACTORS INFLUENCE FIELD IMMUNOGENICITY

Multiple control methods have been used in North America to manage the spread of rabies caused by the raccoon (Procyon lotor) rabies virus variant (RRVV). Recently, oral vaccination with ONRAB® vaccine baits, which contain an adenovirus rabies glycoprotein recombinant, has been made available as an additional tool for rabies control. Our objectives were to estimate rabies antibody prevalence in wild-caught raccoons and striped skunks (Mephitis mephitis), and identify factors influencing the probability of being antibody positive at the individual level in these species, following oral rabies vaccination (ORV) campaigns in which ONRAB was distributed aerially in 2007–2009 in southern Québec, Canada. Following the aerial distribution of 43–155 ONRAB baits/km2, the annual percentages of antibody-positive raccoons and skunks varied between 35% and 56% and 11% and 17%, respectively. In raccoons, the probability of being antibody positive was positively associated with age and density of ONRAB distributed, and influenced by the number of previous ORV campaigns conducted. Conversely, this probability was negatively associated with estimated abundance of raccoons in the trapping cell and proportion of residential areas near the raccoon capture location. None of the variables examined explained variation in the probability of being antibody positive in skunks. Our results indicate that the ONRAB density applied during ORV campaigns should be adjusted to account for variations in raccoon population density and presence of residential areas to increase the likelihood of creating an effective immunological barrier against RRVV. The high percentage of juvenile raccoons (annual mean =45±3 [SE]%) and skunks (66±2%) captured during post-ORV monitoring suggests that ORV campaigns should be conducted at least annually to account for the recruitment of naïve individuals into the populations. In Québec, the increasing use of ONRAB coincided with the elimination of rabies caused by RRVV. Nonetheless, our results indicate that improvements to this vaccine bait and/or the distribution techniques are required to increase its efficacy, especially in striped skunks.