Vaccines as alternatives to antibiotics for food producing animals. Part 1: challenges and needs.

Vaccines and other alternative products can help minimize the need for antibiotics by preventing and controlling infectious diseases in animal populations, and are central to the future success of animal agriculture. To assess scientific advancements related to alternatives to antibiotics and provide actionable strategies to support their development, the United States Department of Agriculture, with support from the World Organisation for Animal Health, organized the second International Symposium on Alternatives to Antibiotics. It focused on six key areas: vaccines; microbial-derived products; non-nutritive phytochemicals; immune-related products; chemicals, enzymes, and innovative drugs; and regulatory pathways to enable the development and licensure of alternatives to antibiotics. This article, part of a two-part series, synthesizes and expands on the expert panel discussions regarding opportunities, challenges and needs for the development of vaccines that may reduce the need for use of antibiotics in animals; new approaches and potential solutions will be discussed in part 2 of this series. Vaccines are widely used to prevent infections in food animals. Various studies have demonstrated that their animal agricultural use can lead to significant reductions in antibiotic consumption, making them promising alternatives to antibiotics. To be widely used in food producing animals, vaccines have to be safe, effective, easy to use, and cost-effective. Many current vaccines fall short in one or more of these respects. Scientific advancements may allow many of these limitations to be overcome, but progress is funding-dependent. Research will have to be prioritized to ensure scarce public resources are dedicated to areas of potentially greatest impact first, and private investments into vaccine development constantly compete with other investment opportunities. Although vaccines have the potential to improve animal health, safeguard agricultural productivity, and reduce antibiotic consumption and resulting resistance risks, targeted research and development investments and concerted efforts by all affected are needed to realize that potential.

Vaccines as alternatives to antibiotics for food producing animals. Part 2: new approaches and potential solutions.

Vaccines and other alternative products are central to the future success of animal agriculture because they can help minimize the need for antibiotics by preventing and controlling infectious diseases in animal populations. To assess scientific advancements related to alternatives to antibiotics and provide actionable strategies to support their development, the United States Department of Agriculture, with support from the World Organisation for Animal Health, organized the second International Symposium on Alternatives to Antibiotics. It focused on six key areas: vaccines; microbial-derived products; non-nutritive phytochemicals; immune-related products; chemicals, enzymes, and innovative drugs; and regulatory pathways to enable the development and licensure of alternatives to antibiotics. This article, the second part in a two-part series, highlights new approaches and potential solutions for the development of vaccines as alternatives to antibiotics in food producing animals; opportunities, challenges and needs for the development of such vaccines are discussed in the first part of this series. As discussed in part 1 of this manuscript, many current vaccines fall short of ideal vaccines in one or more respects. Promising breakthroughs to overcome these limitations include new biotechnology techniques, new oral vaccine approaches, novel adjuvants, new delivery strategies based on bacterial spores, and live recombinant vectors; they also include new vaccination strategies in-ovo, and strategies that simultaneously protect against multiple pathogens. However, translating this research into commercial vaccines that effectively reduce the need for antibiotics will require close collaboration among stakeholders, for instance through public-private partnerships. Targeted research and development investments and concerted efforts by all affected are needed to realize the potential of vaccines to improve animal health, safeguard agricultural productivity, and reduce antibiotic consumption and resulting resistance risks.

The Effect of Carnitine on Peripheral Nerve Regeneration.

INTRODUCTION: Proximal and distal axons of the nerve body are subject to varying degrees of traumatic degeneration after an incision. The histologic structure of rat peripheral nerves cannot be distinguished from the human. Studies on systemic carnitine treatment following peripheral nerve injury and its positive results are available in the literature. There are no reported results of local administration. METHODS: The authors used 50 rats. A total of 5 groups were created by randomly assigning the rats. In the first study group, the nerve was repaired following the incision. NaCl was locally administered to the repair region. In the second study group, the nerve was repaired following the incision. Carnitine was administered systemically. In the third study group, the nerve was repaired following the incision. The rats were administered Carnitine locally and additionally Carnitine was administered systemically. In the fourth study group, the nerve was repaired following the incision. Carnitine was administered locally. The fifth control group did not undergo any procedure. RESULTS: Although Sciatic function index of the groups that received carnitine was better than the group that received NaCl, no statistically significant difference was present. Nerve action potential amplitude values were calculated from the electrophysiological recordings obtained. All groups were compared among themselves, a statistically significant difference was found. A significant difference was found between first, second, third, fourth, control groups. The total nerve area and number of axons per mm was lower in the control group than all other groups. CONCLUSION: Local administration of carnitine was found to be as effective as systemic administration. The authors therefore conclude that carnitine can be used locally, systemically or systemically + locally to increase regeneration following peripheral nerve damage.

Evaluation of protective efficacy of live attenuated Salmonella enterica serovar Gallinarum vaccine strains against fowl typhoid in chickens.

Salmonella enterica serovar Gallinarum is the etiological agent of fowl typhoid, which constitutes a considerable economic problem for poultry growers in developing countries. The vaccination of chickens seems to be the most effective strategy to control the disease in those areas. We constructed S. Gallinarum strains with a deletion of the global regulatory gene fur and evaluated their virulence and protective efficacy in Rhode Island Red chicks and Brown Leghorn layers. The fur deletion mutant was avirulent and, when delivered orally to chicks, elicited excellent protection against lethal S. Gallinarum challenge. It was not as effective when given orally to older birds, although it was highly immunogenic when delivered by intramuscular injection. We also examined the effect of a pmi mutant and a combination of fur deletions with mutations in the pmi and rfaH genes, which affect O-antigen synthesis, and ansB, whose product inhibits host T-cell responses. The S. Gallinarum Δpmi mutant was only partially attenuated, and the ΔansB mutant was fully virulent. The Δfur Δpmi and Δfur ΔansB double mutants were attenuated but not protective when delivered orally to the chicks. However, a Δpmi Δfur strain was highly immunogenic when administered intramuscularly. All together, our results show that the fur gene is essential for the virulence of S. Gallinarum, and the fur mutant is effective as a live recombinant vaccine against fowl typhoid.

Non-Hodgkin lymphoma originating from the frontal sinus.

Primary lymphoma of the paranasal sinuses is a rare entity. Most cases are reported to occur in the maxillary and ethmoid sinuses as well as the nasal cavity. Primary involvement of the frontal sinus is very rare. We report a 68-year-old man with a diagnosis of B-cell lymphoma (non-Hodgkin lymphoma) originating from his frontal sinus.

Safety and efficacy of an aroA-deleted live vaccine against avian colibacillosis in a multicentre field trial in broilers in Morocco.

The safety and efficacy of an aroA-deleted live vaccine against avian colibacillosis (Poulvac(®) E. coli) was evaluated in broilers in a multicentre field trial. The trial sites consisted of 18 paired bird houses (randomly assigned to either the vaccination or the control treatment groups) located in 15 farms in three different regions of Morocco. A field dose of vaccine was administered on day of hatch by the spray route. Both clinical and performance parameters were compared between vaccinated and control groups, in which the experimental unit was defined as the individual bird house. No adverse reactions attributable to the vaccine were observed throughout the study. Non-inferiority of the vaccinated bird houses versus the control houses during a 2-week period post vaccination was statistically demonstrated for mortality and average daily weight gain. Vaccine efficacy was confirmed based on significant differences between vaccinated and unvaccinated groups measured for the full duration of the trial, including colibacillosis-like lesions observed at slaughter (1.7 versus 3.5%; P = 0.0054), total mortality (9.3 versus 10.3%; P = 0.0203), average daily weight gain (47.8 versus 46.2 g/day; P = 0.0006), average number of antibiotic treatment days (0.5 versus 2.0; P = 0.0008) and percentage of the birds that was marketed (90.0 versus 89.0%; P = 0.0309). In conclusion, the vaccine was demonstrated to be both safe and efficacious under field conditions.

Domestic goose as a model for West Nile virus vaccine efficacy.

West Nile virus (WNV) is an emergent pathogen in the Americas, first reported in New York during 1999, and has since spread across the USA, Central and South America causing neurological disease in humans, horses and some bird species, including domestic geese. No WNV vaccines are licensed in the USA for use in geese. This study reports the development of a domestic goose vaccine efficacy model, based on utilizing multiple parameters to determine protection. To test the model, 47 geese were divided in two experiments, testing five different vaccine groups and two sham groups (challenged and unchallenged). Based on the broad range of results for individual metrics between the Challenged-Sham and Unchallenged-Sham groups, the best parameters to measure protection were Clinical Pathogenicity Index (CPI), plasma virus positive geese on days 1-4 post-inoculation and plasma virus titers, and brain histological lesion rates and severity scores. Compared to the Challenged-Sham group, the fowlpox virus vectored vaccine with inserts of WNV prM and E proteins (vFP2000) provided the best protection with significant differences in all five metrics, followed by the canarypox virus vectored vaccine with inserts of WNV prM and E proteins (vCP2018) with four metrics of protection, recombinant vCP2017 with three metrics and WNV E protein with one. These data indicate that domestic geese can be used in an efficacy model for vaccine protection studies using clinical, plasma virological and brain histopathological parameters to evaluate protection against WNV challenge.

Evaluation of the ability of canarypox-vectored equine influenza virus vaccines to induce humoral immune responses against canine influenza viruses in dogs.

OBJECTIVE: To evaluate canarypox-vectored equine influenza virus (EIV) vaccines expressing hemagglutinins of A/equine/Kentucky/94 (vCP1529) and A2/equine/Ohio /03 (vCP2242) for induction of antibody responses against canine influenza virus (CIV) in dogs. ANIMALS: 35 dogs. PROCEDURES: Dogs were randomly allocated into 4 groups; group 1 (n = 8) and group 2 (9) were inoculated SC on days 0 and 28 with 1.0 mL (approx 10(5.7) TCID(50)) of vCP1529 and vCP2242, respectively. Dogs in group 3 (n = 9) were inoculated twice with 0.25 mL (approx 10(5.7) TCID(50)) of vCP2242 via the transdermal route. The 9 dogs of group 4 were control animals. All dogs were examined for adverse reactions. Sera, collected on days -1, 7, 13, 21, 28, 35, and 42, were tested by hemagglutination inhibition (HI) and virus neutralization (VN) assays for antibodies against CIV antigens A/Canine/FL/43/04-PR and A/Canine/NY/115809/05, respectively. RESULTS: Inoculations were tolerated well. The HI and VN antibodies were detected by 7 days after primary inoculation. Most dogs of groups 1 and 2 and all dogs of group 3 had detectable antibodies by 14 days after initial inoculation. The second inoculation induced an anamnestic response, yielding geometric mean HI titers of 139, 276, and 1,505 and VN titers of 335, 937, and 3,288 by day 42 (14 days after booster inoculation) in groups 1, 2, and 3, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Canarypox-vectored EIV vaccines induce biologically important antibodies and may substantially impact CIV transmission within a community and be of great value in protecting dogs against CIV-induced disease.

Recombinant canarypox virus vaccine co-expressing genes encoding the VP2 and VP5 outer capsid proteins of bluetongue virus induces high level protection in sheep.

We describe the development and preliminary characterization of a recombinant canarypox virus vectored vaccine for protective immunization of ruminants against bluetongue virus (BTV) infection. Sheep (n=6) immunized with recombinant canarypox virus vector (BTV-CP) co-expressing synthetic genes encoding the two outer capsid proteins (VP2 and VP5) of BTV serotype 17 (BTV-17) developed high titers (40-160) of virus-specific neutralizing antibodies and were resistant to challenge with a field strain of BTV-17. In contrast, sheep (n=5) immunized with a commercial recombinant canarypox virus vector expressing the E and preM genes of West Nile virus were seronegative to BTV and developed pyrexia, lymphopenia, and extended, high-titered viremias following challenge exposure to the field strain of BTV-17. These data confirm that the BTV-CP vaccine may be useful for the protective immunization of ruminants against bluetongue, and it may avoid the problems inherent to live-attenuated (LA) BTV vaccines.

Development and use of fowlpox vectored vaccines for avian influenza.

The avian influenza (AI) vaccine designated TROVAC-AIV H5 (TROVAC-H5) contains a live recombinant fowlpox rec. (FP) recombinant (recFP), expressing the hemagglutinin (HA) gene of an AI H5 subtype isolate. This recombinant vaccine was granted a license in the United States for emergency use in 1998 and full registration in Mexico, Guatemala, and El Salvador where over 2 billion doses have been administered. One injection of TROVAC-H5 protects chickens against AI-induced mortality and morbidity for at least 20 weeks, and significantly decreases shedding after challenge with a wide panel of H5-subtype AI strains, regardless of neuraminidase subtype. Recently, excellent protection was demonstrated against 2003 and 2004 Asian highly pathogenic H5N1 isolates. Whereas TROVAC-H5 AI H5 efficacy was not inhibited by anti-AI or anti-fowlpox maternal antibodies (passive immunity), protection to AI was significantly decreased in chickens previously vaccinated or infected with FP (active immunity). Advantages of the TROVAC-H5 vaccine over inactivated AI vaccines are: (a) single administration at 1 day of age and early onset (1 week) of protection, (b) easy monitoring of AI infection in vaccinated flocks with agar gel precipitation (AGP) and enzyme-linked immunosorbent assay (ELISA) used as tests to differentiate infected from vaccinated animals (DIVA tests), and (c) no residue problem due to adjuvant. These features make TROVAC-H5 an ideal AI vaccine for routine administration of day-of-age chicks in hatcheries. RecFP expressing HA from three lineages of H7 subtype (Eurasian, American, and Australian) were also tested for efficacy against a highly pathogenic avian influenza (HPAI) Eurasian HPAI H7N1. Only the recFP expressing the Eurasian H7 gene provided sufficient protection indicating that the breadth of protection induced by recFP is apparently restricted for H7 isolates. The fowlpox vector technology can also be used for the production of an emergency vaccine: once the HA sequence of an emerging AI virus is known, recFP can be rapidly generated. TROVAC-H5 has recently been shown to be immunogenic in cats and could therefore also be considered for use in mammals.

Evaluation of the efficacy provided by a Recombinant Canarypox-Vectored Equine West Nile Virus vaccine against an experimental West Nile Virus intrathecal challenge in horses.

Efficacy of the Recombitek Equine West Nile Virus (WNV) vaccine was evaluated against a WNV intrathecal challenge model that results in WNV-induced clinical disease. Ten vaccinated (twice at days 0 and 35) and 10 control horses were challenged 2 weeks after administration of the second vaccine with a virulent WNV by intrathecal administration. After the challenge, eight of 10 controls developed clinical signs of encephalomyelitis whereas one vaccinate exhibited muscle fasciculation only once. Nine controls and one vaccinate developed a fever. Histopathology revealed mild to moderate nonsuppurative encephalitis in eight controls and one vaccinate. None of the vaccinates and all of the controls developed WNV viremia after challenge. All vaccinated horses developed antibodies to WNV after vaccination. These and results of previous studies demonstrate efficacy of the Recombitek WNV vaccine against WNV-induced clinical disease and natural challenge with WNV-infected mosquitoes.

Pathogenesis of West Nile virus infection in dogs treated with glucocorticoids.

Control and glucocorticoid-treated dogs were infected with West Nile virus (WNV) through the bites of infected mosquitoes to study the effect of a commonly used immunomodulator on the magnitude and duration of viremia and on development of clinical disease. All dogs became viremic after challenge. The peak viremia and integrated magnitude of viremia were approximately 40 and 50 times higher, respectively, in the five dogs treated with methyl-prednisolone for 1 month compared with untreated dogs. None of the five control or treated dogs developed signs of clinical disease, nor was histopathologic evidence of neuroinvasion observed in any case. Neutralizing antibodies to WNV were produced in all dogs, with no apparent effect of glucocorticoid treatment. Considering the dramatic effect of glucocorticoid treatment on magnitude of viremia, it is likely that this therapy had suppressive effects on some aspect of innate immunity or T cell function.

Immunogenicity of fowlpox virus expressing the avian influenza virus H5 gene (TROVAC AIV-H5) in cats.

Vaccination of cats with fowlpox virus expressing the avian influenza (AI) virus H5 hemagglutinin gene (TROVAC AI) resulted in detectable hemagglutination inhibition (HI) antibody responses to the homologous A/Turkey/Ireland/1378/83 (H5N8) (A/tky/Ire/83) AI virus antigen. The HI antibody responses to heterologous A/Chicken/Indonesia/7/03 (H5N1) (A/ck/Indonesia/03) AI virus antigen were also detected in all vaccinated cats, but only after booster vaccinations. The vaccine described in this study and other poxvirus-vectored vaccines may be of value for the prophylaxis of AI virus-associated morbidity and mortality in mammals.

Milking technique for reimplanted digits with insufficient venous drainage.

The most common problem after finger replantation is congestion because of insufficient venous drainage. A simple method--milking technique--is described as an additional method for the treatment of venous congestion.

End-to-side nerve coaptation: is an additional proximal coaptation useful when available?

The aim of this experimental study was to evaluate the effects of end-to-side coaptation of the proximal end of a severed nerve to the same intact nerve, in addition to traditional end-to-side coaptation of the distal end, with an aim to use the intact nerve as a nerve conduit in a rat model and to compare the functional and histologic results of this modality to those obtained after nerve grafting and traditional end-to-side nerve coaptation. In group A, a peroneal nerve defect measuring 1 cm was created in the left hind limb, and a nerve graft 1 cm long was used to bridge the defect. In group B, only the distal stump of the peroneal nerve was coapted to the intact tibial nerve. In group C, both ends of the peroneal nerve defect were coapted to the intact tibial nerve in an end-to-side fashion 1.5 cm apart from each other, and in group D, the peroneal nerve defect was left unrepaired. Group E was consisted of nonoperated peroneal nerves that were used to obtain normative data. Although significantly higher myelinated axon densities were observed in groups B and C compared with group A and group E, total number of the myelinated axons was significantly higher only in group C. Peroneal functional index assessments demonstrated that nerve recovery in the peroneal nerve was similar in groups A and C, and both were better than those observed in groups B and D. Collectively, these results suggest that end-to-side coaptation of both ends of a severed nerve to an intact nerve, in case of a nerve defect in this length, may serve as an alternative for nerve grafting.

Assessment of the efficacy of a single dose of a recombinant vaccine against West Nile virus in response to natural challenge with West Nile virus-infected mosquitoes in horses.

OBJECTIVE: To determine the onset of immunity after IM administration of a single dose of a recombinant canarypox virus vaccine against West Nile virus (WNV) in horses in a blind challenge trial. ANIMALS: 20 mixed-breed horses. PROCEDURE: Horses with no prior exposure to WNV were randomly assigned to 1 of 2 groups (10 horses/group). In 1 group, a recombinant canarypox virus vaccine against WNV was administered to each horse once (day 0). The other 10 control horses were untreated. On day 26, 9 treated and 10 control horses were challenged via the bites of mosquitoes (Aedes albopictus) infected with WNV. Clinical responses and WNV isolation were monitored for 14 days after challenge exposure; antibody responses against WNV after administration of the vaccine and challenge were also assessed in both groups. RESULTS: Following challenge via WNV-infected mosquitoes, 1 of 9 treated horses developed viremia. In contrast, 8 of 10 control horses developed viremia after challenge exposure to WNV-infected mosquitoes. All horses seroconverted after WNV challenge; compared with control horses, antibody responses in the horses that received the vaccine were detected earlier. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, a single dose of the recombinant canarypox virus-WNV vaccine appears to provide early protection against development of viremia after challenge with WNV-infected mosquitoes, even in the absence of measurable antibody titers in some horses. This vaccine may provide veterinarians with an important tool in controlling WNV infection during a natural outbreak or under conditions in which a rapid onset of protection is required.

Expression of Escherichia coli antigens in Salmonella typhimurium as a vaccine to prevent airsacculitis in chickens.

Avian pathogenic Escherichia coli strains are associated with a variety of extraintestinal poultry diseases, including airsacculitis, colisepticemia, and cellulitis. A number of E. coli serotypes are associated with these diseases, although the most prevalent serotype is O78. Fimbrial proteins expressed by these strains appear to be important virulence factors, including type 1 fimbriae, P fimbriae, and curli. We have been working to develop an effective vaccine to protect chickens against these diseases. We have previously shown that an attenuated Salmonella typhimurium strain expressing O78 lipopolysaccharide provides protection against challenge with an O78 avian pathogenic E. coli strain. In this work, we have constructed an attenuated S. typhimurium that expresses both the O78 lipopolysaccharide and E. coli-derived type 1 fimbriae. In these studies, chickens were vaccinated at day of hatch and again at 2 wk of age. Birds were challenged at 4 wk of age. We found that the vaccine candidate provided significant protection against airsacculitis as compared to untreated controls or birds vaccinated with an attenuated S. typhimurium that did not express any E. coli antigens. In a separate experiment, challenged vaccinates showed significant weight gain compared to challenged nonvaccinates. We were not able to demonstrate protection against E. coli O1 or O2 serotype challenge, nor against challenge with wild-type S. typhimurium.