Mucosal delivery of vaccines in domestic animals

Development of a spore-based mucosal vaccine against the bovine respiratory pathogen Mannheimia haemolytica

Bovine respiratory disease (BRD) is a significant health issue in the North American feedlot industry, causing substantial financial losses due to morbidity and mortality. A lack of effective vaccines against BRD pathogens has resulted in antibiotics primarily being used for BRD prevention. The aim of this study was to develop a mucosal vaccine against the BRD pathogen, Mannheimia haemolytica, using Bacillus subtilis spores as an adjuvant. A chimeric protein (MhCP) containing a tandem repeat of neutralizing epitopes from M. haemolytica leukotoxin A (NLKT) and outer membrane protein PlpE was expressed to produce antigen for adsorption to B. subtilis spores. Adsorption was optimized by comparing varying amounts of antigen and spores, as well as different buffer pH and reaction temperatures. Using the optimal adsorption parameters, spore-bound antigen (Spore-MhCP) was prepared and administered to mice via two mucosal routes (intranasal and intragastric), while intramuscular administration of free MhCP and unvaccinated mice were used as positive and negative control treatments, respectively. Intramuscular administration of MhCP elicited the strongest serum IgG response. However, intranasal immunization of Spore-MhCP generated the best secretory IgA-specific response against both PlpE and NLKT in all samples evaluated (bronchoalveolar lavage, saliva, and feces). Since proliferation of M. haemolytica in the respiratory tract is a prerequisite to lung infection, this spore-based vaccine may offer protection in cattle by limiting colonization and subsequent infection, and Spore-MhCP warrants further evaluation in cattle as a mucosal vaccine against M. haemolytica.

Intranasal COVID-19 vaccine induces respiratory memory T cells and protects K18-hACE mice against SARS-CoV-2 infection

Current COVID-19 vaccines prevent severe disease, but do not induce mucosal immunity or prevent infection with SARS-CoV-2, especially with recent variants. Furthermore, serum antibody responses wane soon after immunization. We assessed the immunogenicity and protective efficacy of an experimental COVID-19 vaccine based on the SARS-CoV-2 Spike trimer formulated with a novel adjuvant LP-GMP, comprising TLR2 and STING agonists. We demonstrated that immunization of mice twice by the intranasal (i.n.) route or by heterologous intramuscular (i.m.) prime and i.n. boost with the Spike-LP-GMP vaccine generated potent Spike-specific IgG, IgA and tissue-resident memory (T_RM) T cells in the lungs and nasal mucosa that persisted for at least 3 months. Furthermore, Spike-LP-GMP vaccine delivered by i.n./i.n., i.m./i.n., or i.m./i.m. routes protected human ACE-2 transgenic mice against respiratory infection and COVID-19-like disease following lethal challenge with ancestral or Delta strains of SARS-CoV-2. Our findings underscore the potential for nasal vaccines in preventing infection with SARS-CoV-2 and other respiratory pathogen.

The unfulfilled potential of mucosal immunization

Recent events involving the global coronavirus pandemic have focused attention on vaccination strategies. Although tremendous advances have been made in subcutaneous and intramuscular vaccines during this time, one area that has lagged in implementation is mucosal immunization. Mucosal immunization provides several potential advantages over subcutaneous and intramuscular routes, including protection from localized infection at the site of entry, clearance of organisms on mucosal surfaces, induction of long-term immunity through establishment of central and tissue-resident memory cells, and the ability to shape regulatory responses. Despite these advantages, significant barriers remain to achieving effective mucosal immunization. The epithelium itself provides many obstacles to immunization, and the activation of immune recognition and effector pathways that leads to mucosal immunity has been difficult to achieve. This review will highlight the potential advantages of mucosal immunity, define the barriers to mucosal immunization, examine the immune mechanisms that need to be activated on mucosal surfaces, and finally address recent developments in methods for mucosal vaccination that have shown promise in generating immunity on mucosal surfaces in human trials.

Intrauterine immunizations trigger antigen-specific mucosal and systemic immunity in pigs and passive protection in suckling piglets

We assessed whether vaccines administered to the uterus at breeding can lead to sufficient colostral antibodies to protect suckling piglets against Porcine Endemic Diarrhea Virus (PEDV). An antigen from Lawsonia intracellularis, a disease that impacts weanling intestinal health, was also included because we have extensive knowledge on the pig immune response to this antigen. Gilts were mock-bred at 2nd estrus with killed sperm including an intrauterine (i.u.) vaccine comprised of recombinant (r) PEDV Spike protein (rPEDVS1) and L. intracellularis flagellin (rFliC) formulated with poly I:C, host defense peptide, and polyphosphazene (TriAdj). Gilts returned to estrus within 3 weeks and they were inseminated with killed sperm (3rd estrus) or live sperm (4th estrus) with rPEDVS1-TriAdj vaccine. They also received an i.m. injection of rFliC-TriAdj at 3rd and 4th estrus to establish whether i.u. vaccination primes systemic immunity without inducing mucosal tolerance. Control gilts were administered semen alone at 2nd estrus which allowed us to compare litter weights and sizes to industry standards. Colostrum from gilts challenged with low dose PEDV plus alum was used as positive reference samples for neutralizing antibodies and passive protection. Thirteen weeks later, the i.u.-vaccinated gilts showed significant PEDVS1-specific serum, colostral, and uterine antibody titers and colostral PEDVS1-neutralizing antibodies but poor cell-mediated immunity. Piglets born to i.u. vaccinated gilts received partial passive protection from PEDV infection 3 days after birth but eventually succumbed to the disease. Immunization by the i.u./i.m. route triggered significant anti-FliC cell-mediated immunity and colostral FliC antibodies that remained high in weaned piglet serum. This trial and a repeat trial wherein gilts were immunized at 1st estrus without semen and at 2nd estrus with live semen showed that intrauterine immunization did not impact fertility, number of live births or piglet growth kinetics. Further optimization is needed to promote robust passive protection in suckling offspring.

High-Throughput Synthesis of Liposome Using an Injection-Molded Plastic Micro-Fluidic Device

For mass production of liposomes, we designed a plastic micro-channel device on the basis of 5 μm of micro-nozzle array forming T-junction with 100 μm depth of micro-channel. A micro-channel unit for synthesizing liposomes consisted of two micro-nozzle arrays for mixing two solutions as well as delivery and recovery channels for supplying solutions and collecting liposome suspension. The number of micro-nozzles was approximately 2400 for a micro-channel unit, and seven units were applied independently on a micro-channel plate. The plastic micro-channel plate was injection-molded for mass production using a micro-channel stamper previously fabricated by UV lithography and nickel electroforming process. A plastic cover plate with seven pairs of inlet and outlet ports was machined by mechanical milling and drilling and was assembled with a micro-channel plate using a holder to form a liposome synthesizing device. Flow and mixing of solutions in the micro-channels were tested using colored water to check the micro-fluidic characteristics of the device. Finally, a L-α-phosphatidylcholine (SOY PC) liposome was synthesized using EtOH solution of SOY PC (95%) and saline (0.85% NaOH solution) to find that the liposomes were around 230 and 260 nm in diameter, depending on the flow rate of the lipid solution.

Nanotechnology and Animal Health

Nanotechnology has been a rapidly expanding area of research with huge potential in many sectors, including animal healthcare. It promises to revolutionize drug and vaccine delivery, diagnostics, and theranostics, which has become an important tool in personalized medicine by integrating therapeutics and diagnostics. Nanotechnology has also been used successfully in animal nutrition. In this review, the application of nanotechnology in animal health will be reviewed with its pros and cons.

Development of Salmonella Enteritidis vaccine candidate based on streptomycin independent suppressor and metabolic drift rifampicin resistance-attenuating markers

Salmonella is one of the most frequent food-borne pathogens and remains public health threat globally. The control of Salmonella in poultry, the main reservoir of non-typhoidal salmonellae, is a fundamental approach to ensure the safety of poultry products for human consumption. In the present study, a new live attenuated Salmonella enterica serovar Enteritidis vaccine candidate containing three attenuating markers based on streptomycin-independent (Sm-id) suppressor, and metabolic drift antibiotic resistance (MD- “res”) was developed. The streptomycin dependent (Smd) mutants were derived from Salmonella Enteritidis wild-type strain using streptomycin. Then the Sm-id mutants were derived from the isolated Smd mutants and designated “Smd→Sm-id”. A third MD- “res” marker was generated from Smd→Sm-id using rifampicin (Rif) and designated “Smd→Sm-id→Rif”. The colony sizes of these mutants were stable after more than 50 serial passages on blood agar; reversion to virulence can be almost excluded. The safety and efficacy of Smd→Sm-id and Smd→Sm-id→Rif were evaluated in one-day-old commercial layer chicks. Both mutants proved to be safe in terms of clinical signs, mortalities, lesion scores of visceral organs and rapid clearance when administered orally at a dose of 10⁸ colony forming unit (CFU), whereas birds inoculated with 10⁸ CFU Salmonella Enteritidis wild-type strain showed diarrhea, mortalities (3/40) and necrosis in liver and spleen. Chickens vaccinated with the developed mutants showed no seroconversion; however, wild-type strain induced a significant seroconversion at 3-week-postvaccination (wpv). The developed mutants protected chickens against challenge with 10⁸ CFU of Salmonella Enteritidis wild-type strain at 3-wpv. Vaccinated birds showed neither clinical signs nor mortalities during two-week post-challenge. In addition, the challenge strain could not be detected in pooled liver and spleen samples (0/5) at 7^th day post-inoculation (dpi). However, non-vaccinated challenged birds showed diarrhea and the challenge strain was re-isolated from pooled liver and spleen samples (3/5) at 7^th dpi. In conclusion, the developed mutants are safe and fully protected immunized chickens following heterologous challenge. It is obvious that the genetic characterization of these mutants and evaluation of different vaccination regimes are still in demand.

Assessment of Immunological Response and Impacts on Fertility Following Intrauterine Vaccination Delivered to Swine in an Artificial Insemination Dose

To protect the health of sows and gilts, significant investments are directed toward the development of vaccines against infectious agents that impact reproduction. We developed an intrauterine vaccine that can be delivered with semen during artificial insemination to induce mucosal immunity in the reproductive tract. An in vitro culture of uterine epithelial cells was used to select an adjuvant combination capable of recruiting antigen-presenting cells into the uterus. Adjuvant polyinosinic:polycytidylic acid (poly I:C), alone or in combination, induced expression of interferon gamma, tumor necrosis factor alpha, and select chemokines. A combination adjuvant consisting of poly I:C, host defense peptide and polyphosphazene (Triple Adjuvant; TriAdj), which previously was shown to induce robust mucosal and systemic humoral immunity when administered to the uterus in rabbits, was combined with boar semen to evaluate changes in localized gene expression and cellular recruitment, in vivo. Sows bred with semen plus TriAdj had decreased γδ T cells and monocytes in blood, however, no corresponding increase in the number of monocytes and macrophages was detected in the endometrium. Compared to sows bred with semen alone, sows bred with semen plus TriAdj showed increased CCL2 gene expression in the epithelial layer. These data suggest that the adjuvants may further augment a local immune response and, therefore, may be suitable for use in an intrauterine vaccine. When inactivated porcine parvovirus (PPV) formulated with the TriAdj was administered to the pig uterus during estrus along with semen, we observed induction of PPV antibodies in serum but only when the pigs were already primed with parenteral PPV vaccines. Recombinant protein vaccines and inactivated PPV vaccines administered to the pig uterus during breeding as a primary vaccine alone failed to induce significant humoral immunity. More trials need to be performed to clarify whether repeated intrauterine vaccination can trigger strong humoral immunity or whether the primary vaccine needs to be administered via a systemic route to promote a mucosal and systemic immune response.

Bacterial Endotoxins and Their Role in Periparturient Diseases of Dairy Cows: Mucosal Vaccine Perspectives

During the periparturient period there is a significant increase in the incidence of multiple metabolic and infectious diseases in dairy cows. Dairy cows are fed high-grain diets immediately after calving to support production of large amounts of milk. Mounting evidence indicates these types of diets are associated with the release of high amounts of endotoxins in the rumen fluid. If infected, the udder and uterus additionally become important sources of endotoxins during the postpartum period. There is increasing evidence that endotoxins translocate from rumen, uterus, or udder into the systemic circulation and trigger chronic low-grade inflammatory conditions associated with multiple diseases including fatty liver, mastitis, retained placenta, metritis, laminitis, displaced abomasum, milk fever, and downer cow syndrome. Interestingly, endotoxin-related diseases are triggered by a bacterial component and not by a specific bacterium. This makes prevention of these type of diseases different from classical infectious diseases. Prevention of translocation of endotoxins into the host systemic circulation needs to take priority and this could be achieved with a new approach: mucosal vaccination. In this review article, we discuss all the aforementioned issues in detail and also report some of our trials with regards to mucosal vaccination of periparturient dairy cows.

Mucosal and systemic immune responses to Aujeszky's disease virus (ADV) in early vaccinated piglets

Newborn humans and animals are highly susceptible to viral infections. The Aujeszky´s disease virus (ADV) is a porcine herpes virus 1 which infects the respiratory tract and is lethal during the first weeks of life. Current intramuscular vaccines, applied at weaning, induce poor mucosal immunity and frequently fail to prevent and control the disease. Additionally, early vaccination has not been studied thoroughly. Therefore, we studied a systemic/mucosal route of immunization using an inactivated ADV vaccine in two-and fourteen-day-old groups of unweaned SPF miniature Vietnamese pigs, measuring the anti ADV antibody (ELISA) and cytokine (qPCR) responses in systemic and mucosal samples. The results showed that the serum ADV-specific IgG response was higher in the 14-day groups. However, the nasal IgA responses were similar in immunized groups, although the response in saliva was higher in the 2-day old group. Moreover, in vitro ADV stimulated peripheral blood mononuclear cells and lung cells from immunized pigs showed higher IFN-γ mRNA production in the 14-day old group than in younger animals and similar levels of IL-4 and IL-10 transcripts. Our data suggest that early mucosal immunization induce humoral and cellular systemic and mucosal immune responses against ADV in young pigs and younger animals may have compensatory mechanisms to overcome early immaturity and maternal-driven immune interference. Therefore, early protection in susceptible animals could be induced using this immunization protocol, opening the possibility for its application against other viral pathogens of pigs and for traslational studies in humans.

Genome-Wide Identification of Virulence Genes in Erysipelothrix rhusiopathiae: Use of a Mutant Deficient in a tagF Homolog as a Safe Oral Vaccine against Swine Erysipelas

Swine erysipelas is caused by the Gram-positive pathogen Erysipelothrix rhusiopathiae The swine erysipelas live vaccine in Japan, the E. rhusiopathiae Koganei 65-0.15 strain (Koganei), has been reported to cause arthritis and endocarditis. To develop a vaccine with increased safety, we used a virulent Fujisawa strain to construct transposon mutants for a total of 651 genes, which covered 38% of the coding sequence of the genome. We screened the mutants for attenuation by inoculating mice with 10⁸ CFU of each mutant and subsequently assessed protective capability by challenging the surviving mice with 10³ CFU (10² times the 50% lethal dose) of the Fujisawa strain. Of the 23 attenuated mutants obtained, 6 mutants were selected and evaluated for protective capability in pigs by comparison to that of the Koganei strain. A mutant in the ERH_0432 (tagF) gene encoding a putative CDP-glycerol glycerophosphotransferase was found to be highly attenuated and to induce humoral and cell-mediated immune responses in conventional pigs. An in-frame deletion mutant of the gene, the Δ432 mutant, was constructed, and attenuation was further confirmed in germfree piglets; three of four piglets subcutaneously inoculated with 10⁹ CFU of the Δ432 mutant showed no apparent clinical symptoms, whereas all four of the Koganei-inoculated piglets died 3 days after inoculation. It was confirmed that conventional pigs inoculated orally or subcutaneously with the Δ432 strain were almost completely protected against lethal challenge infection. Thus, the tagF homolog mutant of E. rhusiopathiae represents a safe vaccine candidate that can be administered via the oral and subcutaneous routes.

Primary Human B Cells at Different Differentiation and Maturation Stages Exhibit Distinct Susceptibilities to Vaccinia Virus Binding and Infection

Vaccinia virus (VACV), the prototypical member of the poxvirus family, was used as a live-virus vaccine to eradicate smallpox worldwide and has recently received considerable attention because of its potential as a prominent vector for the development of vaccines against infectious diseases and as an oncolytic virus for cancer therapy. Studies have demonstrated that VACV exhibits an extremely strong bias for binding to and infection of primary human antigen-presenting cells (APCs), including monocytes, macrophages, and dendritic cells. However, very few studies have assessed the interactions of VACV with primary human B cells, a main type of professional APCs. In this study, we evaluated the susceptibility of primary human peripheral B cells at various differentiation and maturation stages to VACV binding, infection, and replication. We found that plasmablasts were resistant to VACV binding, while other B subsets, including transitional, mature naive, memory, and plasma cells, were highly susceptible to VACV binding. VACV binding preference was likely associated with differential expression of chemokine receptors, particularly CXCR5. Infection studies showed that plasmablast, plasma, transitional, and mature naive B cells were resistant to VACV infection, while memory B cells were preferentially infected. VACV infection in ex vivo B cells was abortive, which occurred at the stage of late viral gene expression. In contrast, activated B cells were permissive to productive VACV infection. Thus, primary human B cells at different differentiation stages exhibit distinct susceptibilities to VACV binding and infection, and the infections are abortive and productive in ex vivo and activated B cells, respectively.IMPORTANCE Our results provide critical information to the field of poxvirus binding and infection tropism. We demonstrate that VACV preferentially infects memory B cells that play an important role in a rapid and vigorous antibody-mediated immune response upon reinfection by a pathogen. Additionally, this work highlights the potential of B cells as natural cellular models to identify VACV receptors or dissect the molecular mechanisms underlying key steps of the VACV life cycle, such as binding, penetration, entry, and replication in primary human cells. The understanding of VACV biology in human primary cells is essential for the development of a safe and effective live-virus vector for oncolytic virus therapy and vaccines against smallpox, other pathogens, and cancer.

Veterinary vaccine nanotechnology: pulmonary and nasal delivery in livestock animals

Veterinary vaccine development has several similarities with human vaccine development to improve the overall health and well-being of species. However, veterinary goals lean more toward feasible large-scale administration methods and low cost to high benefit immunization. Since the respiratory mucosa is easily accessible and most infectious agents begin their infection cycle at the mucosa, immunization through the respiratory route has been a highly attractive vaccine delivery strategy against infectious diseases. Additionally, vaccines administered via the respiratory mucosa could lower costs by removing the need of trained medical personnel, and lowering doses yet achieving similar or increased immune stimulation. The respiratory route often brings challenges in antigen delivery efficiency with enough potency to induce immunity. Nanoparticle (NP) technology has been shown to enhance immune activation by producing higher antibody titers and protection. Although specific mechanisms between NPs and biological membranes are still under investigation, physical parameters such as particle size and shape, as well as biological tissue distribution including mucociliary clearance influence the protection and delivery of antigens to the site of action and uptake by target cells. For respiratory delivery, various biomaterials such as mucoadhesive polymers, lipids, and polysaccharides have shown enhanced antibody production or protection in comparison to antigen alone. This review presents promising NPs administered via the nasal or pulmonary routes for veterinary applications specifically focusing on livestock animals including poultry.

A Promising Recombinant Herpesvirus of Turkeys Vaccine Expressing PmpD-N of Chlamydia psittaci Based on Elongation Factor-1 Alpha Promoter

The obligate intracellular Gram-negative bacterium Chlamydia psittaci often causes avian chlamydiosis and influenza-like symptoms in humans. However, the commercial subunit C. psittaci vaccine could only provide a partial protection against avian chlamydiosis due to poor cellular immune response. In our previous study, a recombinant herpesvirus of turkeys (HVT)-delivered vaccine against C. psittaci and Marek’s disease based on human cytomegalovirus (CMV) promoter (rHVT-CMV-pmpD) was developed and provided an effective protection against C. psittaci disease with less lesions and reduced chlamydial loads. In this study, we developed another recombinant HVT vaccine expressing the N-terminal fragment of PmpD (PmpD-N) based on human elongation factor-1 alpha (EF-1α) promoter (rHVT-EF-pmpD) by modifying the HVT genome within a bacterial artificial chromosome. The related characterization of rHVT-EF-pmpD was evaluated in vitro in comparison with that of rHVT-CMV-pmpD. The expression of PmpD-N was determined by western blot. Under immunofluorescence microscopy, PmpD-N protein of both two recombinant viruses was located in the cytoplasm and on the cell surface. Growth kinetics of rHVT-EF-pmpD was comparable to that of rHVT-CMV-pmpD, and the growth rate of rHVT-EF-pmpD was apparently higher than that of rHVT-CMV-pmpD on 48, 72, and 120 h postinfection. Macrophages activated by rHVT-EF-pmpD could produce more nitric oxide and IL-6 than that activated by rHVT-CMV-pmpD. In this study, a recombinant HVT vaccine expressing PmpD-N based on EF-1α promoter was constructed successfully, and a further research in vivo was needed to analyze the vaccine efficacy.

Gut-Associated Lymphoid Tissue: A Key Tissue Inside the Mucosal Immune System of Hens Immunized with Escherichia coli F4

Immunoglobulin Y (IgY) is the predominant antibody found in hen's (Gallus domesticus) egg yolk. This antibody, developed against several microorganisms in hen egg yolk, has been successfully used as an alternative to immunoglobulins from mammals for use in immunodiagnostics and immunotherapy. Enteropathogenic Escherichia coli (E.coli) F4 is the main etiological agent associated with swine neonatal diarrhea, and it causes notable economic losses in swine production. The aim of the present study was to evaluate the relationship between humoral immune response and the activation of gut-associated lymphoid tissue (GALT) in laying hens intramuscularly immunized with E. coli F4. Adult laying Shaver hens were immunized with a bacterin based on an inactivated lysate E. coli F4 strain that was originally isolated from neonatal piglet diarrhea, following a recommended schedule. The percentage of B lymphocytes in blood and spleen homogenates was determined by flow cytometry. Villi histomorphometry and the size of germinal centers (GC) activated in GALT and the spleen were measured in histological samples either stained with hematoxylin/eosin or through immunofluorescence. Antibody and isotype-specific antibodies in serum and egg yolk were measured using indirect enzyme-linked immunosorbent assay (ELISA). Secretory and serum immunoglobulin A (IgA) were measured by ELISA tests. Laying hen with intramuscular immunization with E. coli F4 lysate, activated both mucosal and systemic protection. Mucosal protection was provided through B lymphocytes, and most of them were activated on Peyer's patches and esophageal tonsils, in GALT. Furthermore, increased B lymphocyte number in the lamina propria of the gut, and increased intraepithelial plasmatic cell number, produced high levels of mucosal IgA. Activated B lymphocytes interacted with absorptive cells, immune cells, and microbiota in the gut, producing signals that were translated into a powerful physical defense by producing a greater volume of mucin from an increased number of goblet cells. Systemic protection was provided through B lymphocyte activation of spleen GC, which produced hugely specific IgY serum levels. One week later, this specific IgY was deposited in the yolk. This suggests that GALT is a key immunologic tissue inside the mucosal immune system, acting as the "command center" for humoral reaction.

Oral vaccination of fish: Lessons from humans and veterinary species

The limited number of oral vaccines currently approved for use in humans and veterinary species clearly illustrates that development of efficacious and safe oral vaccines has been a challenge not only for fish immunologists. The insufficient efficacy of oral vaccines is partly due to antigen breakdown in the harsh gastric environment, but also to the high tolerogenic gut environment and to inadequate vaccine design. In this review we discuss current approaches used to develop oral vaccines for mass vaccination of farmed fish species. Furthermore, using various examples from the human and veterinary vaccine development, we propose additional approaches to fish vaccine design also considering recent advances in fish mucosal immunology and novel molecular tools. Finally, we discuss the pros and cons of using the zebrafish as a pre-screening animal model to potentially speed up vaccine design and testing for aquaculture fish species.

Delivery of an inactivated avian influenza virus vaccine adjuvanted with poly(D,L-lactic-co-glycolic acid) encapsulated CpG ODN induces protective immune responses in chickens

In poultry, systemic administration of commercial vaccines consisting of inactivated avian influenza virus (AIV) requires the simultaneous delivery of an adjuvant (water-in-oil emulsion). These vaccines are often limited in their ability to induce quantitatively better local (mucosal) antibody responses capable of curtailing virus shedding. Therefore, more efficacious adjuvants with the ability to provide enhanced immunogenicity and protective anti-AIV immunity in chickens are needed. While the Toll-like receptor (TLR) 21 agonist, CpG oligodeoxynucleotides (ODNs) has been recognized as a potential vaccine adjuvant in chickens, poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles, successfully tested as vaccine delivery systems in other species, have not been extensively explored. The present study, therefore, assessed both systemic and mucosal antibody-mediated responses following intramuscular vaccination (administered at 7 and 21days post-hatch) of chickens with PLGA encapsulated H9N2 AIV plus encapsulated CpG ODN 2007 (CpG 2007), and nonencapsulated AIV plus PLGA encapsulated CpG 2007 vaccine formulations. Virus challenge was performed at 2weeks post-secondary vaccination using the oculo-nasal route. Our results showed that chickens vaccinated with the nonencapsulated AIV vaccine plus PLGA encapsulated CpG 2007 developed significantly higher systemic IgY and local (mucosal) IgY antibodies as well as haemagglutination inhibition antibody titres compared to PLGA encapsulated AIV plus encapsulated CpG 2007 vaccinated chickens. Furthermore, chickens that received CpG 2007 as an adjuvant in the vaccine formulation had antibodies exhibiting higher avidity indicating that the TLR21-mediated pathway may enhance antibody affinity maturation qualitatively. Collectively, our data indicate that vaccination of chickens with nonencapsulated AIV plus PLGA encapsulated CpG 2007 results in qualitatively and quantitatively augmented antibody responses leading to a reduction in virus shedding compared to the encapsulated AIV plus PLGA encapsulated CpG 2007 formulation.

Live-Attenuated Bacterial Vectors: Tools for Vaccine and Therapeutic Agent Delivery

Genetically attenuated microorganisms, including pathogenic and commensal bacteria, can be engineered to carry and deliver heterologous antigens to elicit host immunity against both the vector as well as the pathogen from which the donor gene is derived. These live attenuated bacterial vectors have been given much attention due to their capacity to induce a broad range of immune responses including localized mucosal, as well as systemic humoral and/or cell-mediated immunity. In addition, the unique tumor-homing characteristics of these bacterial vectors has also been exploited for alternative anti-tumor vaccines and therapies. In such approach, tumor-associated antigen, immunostimulatory molecules, anti-tumor drugs, or nucleotides (DNA or RNA) are delivered. Different potential vectors are appropriate for specific applications, depending on their pathogenic routes. In this review, we survey and summarize the main features of the different types of live bacterial vectors and discussed the clinical applications in the field of vaccinology. In addition, different approaches for using live attenuated bacterial vectors for anti-cancer therapy is discussed, and some promising pre-clinical and clinical studies in this field are outlined.

Construction of Recombinant HVT Expressing PmpD, and Immunological Evaluation against Chlamydia psittaci and Marek's Disease Virus

Chlamydia psittaci (C. psittaci) is an obligate intracellular zoonotic pathogen that can be transmitted to humans from birds. No efficacious commercial vaccine is available for clearing chlamydial infection due to lack of potential vaccine candidates and effective delivery vehicles. Herpesvirus of turkeys (HVT) is an efficacious commercially available vaccine against Marek’s Disease virus (MDV). In this study, a recombinant HVT-delivered vaccine against C. psittaci and Marek’s disease was developed and examined. The 5'-terminus of pmpD gene (pmpD-N) encoding the N-terminal fragment of polymorphic membrane protein D of C. psittaci was inserted into a nonessential region of HVT genome using reverse genetics based on an infectious bacterial artificial chromosome (BAC) clone of HVT. The recombinant virus (rHVT-pmpD-N) was recovered from primary chicken embryo fibroblast (CEF) cells by transfection of modified HVT BAC DNA containing the pmpD-N gene. The rHVT-pmpD-N construct was confirmed to express PmpD-N by immunoblot and immunofluorescence. The rHVT-pmpD-N was stable during 20 passages in vitro. The growth kinetics of rHVT-pmpD-N was comparable to that of parental HVT in vitro and in vivo. One-day-old SPF chickens inoculated subcutaneously with rHVT-pmpD-N displayed increased PmpD-specific antibody levels and a vigorous PmpD-specific lymphocyte proliferation response using HVT vector or CEF cells as control. Furthermore, the percentage of CD4+ cells was significantly elevated in rHVT-pmpD-N-immunized birds as compared to the parental HVT. All chickens vaccinated with rHVT-pmpD-N or parental HVT were protected completely against challenge with a very virulent strain of Marek’s Disease virus (MDV) RB-1B. Post challenge with C. psittaci CB7 strain, a significant decrease in respiratory distress, lesions and Chlamydia load was found in the rHVT-pmpD-N-vaccinated group compared to the parental HVT. In conclusion, our study suggests that the rHVT-pmpD-N live vaccine may be viable as a candidate dual vaccine that provides protection against both very virulent MDV and C. psittaci.

The challenges in developing effective canine infectious respiratory disease vaccines

Objectives

Canine infectious respiratory disease (CIRD) is a disease of multifactorial aetiology, where multiple pathogens act sequentially or synergistically to cause disease. It is common within large dog populations, such as those in re‐homing or training kennels. Vaccines are vital in its management of CIRD, but they often fail to prevent disease. Recently, a number of novel pathogens have been identified in CIRD outbreaks and represent new targets for vaccination.

Key findings

Innate immune responses provide a vital first line of defence against the infectious agents involved in the development of CIRD. Once breeched, adaptive mucosal immunity is necessary to prevent infection and limit spread. Current vaccines target only a few of the agents involved in CIRD. Evidence, from the limited amount of published data, indicates that although vaccinating against these agents reduces infection rates, duration of shedding and severity of disease, it does not induce sterilising immunity; and this has important consequences for the management of the disease, and the future of CIRD vaccine development.

Summary

In the process of considering the development of novel CIRD vaccines, this paper focuses on the immunological mechanisms that provide protection for the respiratory tract, the current recommendations for canine vaccination, and the challenges surrounding existing CIRD vaccines, and their future development.

Influenza viral vectors expressing the Brucella OMP16 or L7/L12 proteins as vaccines against B. abortus infection

BACKGROUND

We generated novel, effective candidate vaccine against Brucella abortus based on recombinant influenza viruses expressing the Brucella ribosomal protein L7/L12 or outer membrane protein (Omp)-16 from the NS1 open reading frame. The main purpose of this work was to evaluate the safety, immunogenicity and protectiveness of vaccine candidate in laboratory animals.

METHODS AND RESULTS

Four recombinant influenza A viral constructs of the subtypes Н5N1 or H1N1 expressing the Brucella proteins L7/L12 or Omp16 were obtained by a reverse genetics method: Flu-NS1-124-L7/L12-H5N1, Flu-NS1-124-Omp16-H5N1, Flu-NS1-124-L7/L12-H1N1 and Flu-NS1-124-Omp16-H1N1. Despite of substantial modification of NS1 gene, all constructs replicated well and were retain their Brucella inserts over five passages in embryonated chicken eggs (CE). Administration of the mono- or bivalent vaccine formulation via prime-boost intranasal (i.n.), conjunctival (c.) or subcutaneous (s.c.) immunization was safe in mice; no deaths, body weight loss or pathomorphological changes were observed over 56 days. Moreover, guinea pigs vaccinated i.n. with vaccine vectors did not shed the vaccine viruses through their upper respiratory tract after the prime and booster vaccination. These findings confirmed the replication-deficient phenotype of viral vectors. The highest antibody response to Brucella antigen was obtained with constructs expressing L7/L12 (ELISA, GMT 242.5-735.0); whereas the highest T-cell immune response- with construct expressing Omp16 (ELISPOT, 337 ± 52-651 ± 45 spots/4×105cells), which was comparable (P > 0.05) to the response induced by the commercial vaccine B. abortus 19. Interestingly, c. immunization appeared to be optimal for eliciting T-cell immune response. In guinea pigs, the highest protective efficacy after challenge with B. abortus 544 was achieved with Omp16 expressing constructs in both monovalent or bivalent vaccine formulations; protective efficacy was comparable to those induced by a commercial live B. abortus 19 vaccine.

CONCLUSION

Thus, influenza vectors expressing Brucella protective antigens can be developed as novel influenza vectored vaccine against B. abortus infection.

Antigen targeting to APC: from mice to veterinary species

Antigen delivery to receptors expressed on antigen presenting cells (APC) has shown to improve immunogenicity of vaccines in mice. An enhancement of cytotoxic T lymphocyte (CTL), helper T cell or humoral responses was obtained depending on the type of APC and the surface molecule targeted. Although this strategy is being also evaluated in livestock animals with promising results, some discrepancies have been found between species and pathogens. The genetic diversity of livestock animals, the different pattern of expression of some receptors among species, the use of different markers to characterize APC in large animals and sometimes the lack of reagents make difficult to compare results obtained in different species. In this review, we summarize the data available regarding antigen targeting to APC receptors in cattle, sheep and pig and discuss the results found in these animals in the context of what has been obtained in mice.

Safety and efficacy of a metabolic drift live attenuated Salmonella Gallinarum vaccine against fowl typhoid

Fowl typhoid (FT), a systemic disease that results in septicemia in poultry, is caused by Salmonella enterica serovar Gallinarum biovar Gallinarum (SG). Mortality and morbidity rates from FT can reach up to 80%. Attenuated live Salmonella vaccine candidates have received considerable attention because they confer solid immunity, and they can produce systemic and mucosal immunity in the gut when administered orally. In the present study, five metabolic drift (MD) mutants with a single-(designated SG-Rif1, SG-Sm6) or double-attenuating marker (designated SG-Rif1-Sm4, SG-Sm6-Rif10, and SG-Rif1-Sm10) were isolated. The relative colony sizes to wild-type strain after 24 hr at 37 C incubation were 50%, 40%, 30%, 30%, and 20%, respectively. The probability of a back mutation can almost be excluded because the reduced colony sizes were stable after at least 50 passages on culture media. The safety and immunogenicity were evaluated in susceptible 1-day-old commercial layer chickens. After oral administration of 10(8) colony-forming units (CFU), all developed MD mutants proved to be safe and did not cause death of any infected birds during 15 days postvaccination, whereas chickens receiving 10(6) CFU SG wild-type strain showed a high mortality rate (40%). Vaccination of commercial layer chicks with SG-Rif1, SG-Sm6, SG-Rif1-Sm4, and SG-Sm6-Rif10 MD mutants could protect chickens against challenge by homologous wild-type strain; however, SG-Rif1-Sm10 could not protect against challenge, indicating hyperattenuation. In conclusion, vaccination with SG MD mutant vaccine appears to be safe and offers protection against FT in chickens.

Primary human leukocyte subsets differentially express vaccinia virus receptors enriched in lipid rafts

Poxviruses, including vaccinia virus (VV) and canarypox virus (ALVAC), do not indiscriminately infect all cell types of the primary human leukocytes (PHLs) that they encounter but instead demonstrate an extremely strong bias toward infection of monocytes and monocyte lineage cells. We studied the specific molecular events that determine the VV tropism for major PHL subsets including monocytes, B cells, neutrophils, NK cells, and T cells. We found that VV exhibited an extremely strong bias of cell surface protein-dependent binding to monocytes, B cells, and activated T cells to a similar degree and to neutrophils to a much lesser extent. Resting T cells and resting NK cells exhibited only trace amounts of VV binding. Activated T cells, however, became permissive to VV binding, infection, and replication, while activated NK cells still resisted VV binding. VV binding strongly colocalized with lipid rafts on the surfaces of all VV binding-susceptible PHL subsets, even when lipid rafts were relocated to cell uropods upon cell polarization. Immunosera raised against detergent-resistant membranes (DRMs) from monocytes or activated T cells, but not resting T cells, effectively cross-blocked VV binding to and infection of PHL subsets. CD29 and CD98, two lipid raft-associated membrane proteins that had been found to be important for VV entry into HeLa cells, had no effect on VV binding to and infection of primary activated T cells. Our data indicate that PHL subsets express VV protein receptors enriched in lipid rafts and that receptors are cross-presented on all susceptible PHLs.

A review of vaccine development and research for industry animals in Korea

Vaccination has proven to be the most cost-effective strategy for controlling a wide variety of infectious diseases in humans and animals. For the last decade, veterinary vaccines have been substantially developed and demonstrated their effectiveness against many diseases. Nevertheless, new vaccines are greatly demanded to effectively control newly- and re-emerging pathogens in livestock. However, development of veterinary vaccines is a challenging task, in part, due to a variety of pathogens, hosts, and the uniqueness of host-susceptibility to each pathogen. Therefore, novel concepts of vaccines should be explored to overcome the limitation of conventional vaccines. There have been greatly advanced in the completion of genomic sequencing of pathogens, the application of comparative genomic and transcriptome analysis. This would facilitate to open opportunities up to investigate a new generation of vaccines; recombinant subunit vaccine, virus-like particle, DNA vaccine, and vector-vehicle vaccine. Currently, such types of vaccines are being actively explored against various livestock diseases, affording numerous advantages over conventional vaccines, including ease of production, immunogenicity, safety, and multivalency in a single shot. In this articles, the authors present the current status of the development of veterinary vaccines at large as well as research activities conducted in Korea.

Immunostimulatory effects of recombinant Erysipelothrix rhusiopathiae expressing porcine interleukin-18 in mice and pigs

Interleukin-18 (IL-18), which was originally called gamma interferon (IFN-γ)-inducing factor, has been shown to play an important role in innate and acquired immune responses. In this study, attenuated Erysipelothrix rhusiopathiae strains were engineered to produce porcine IL-18 (poIL-18) and evaluated for their potential immunostimulatory effect in animals. Recombinant poIL-18 was successfully expressed in the recombinant E. rhusiopathiae strains YS-1/IL-18 and KO/IL-18. The culture supernatant of YS-1/IL-18 was confirmed to induce IFN-γ production in murine splenocytes in vitro, and this production was inhibited by incubation with anti-poIL-18 monoclonal antibodies. Furthermore, more IFN-γ production was induced upon stimulation of splenocytes with concanavalin A for splenocytes from mice that were intraperitoneally inoculated with YS-1/IL-18 than for splenocytes from control mice inoculated with the parent strain YS-1. Peritoneal macrophages from mice preinoculated with YS-1/IL-18 exhibited enhanced phagocytosis of Salmonella enterica subsp. enterica serovar Typhimurium compared with peritoneal macrophages from control mice preinoculated with YS-1. We also confirmed the immunostimulatory effect on humoral immune responses against antigens of E. rhusiopathiae and Mycoplasma hyopneumoniae in gnotobiotic pigs that were orally preinoculated with KO/IL-18. Thus, these results provide evidence that E. rhusiopathiae is a promising vector for the expression of host cytokines and suggest the potential utility of E. rhusiopathiae vector-encoded cytokines in the activation of host innate and acquired immune responses.

Biotechnologies for the management of genetic resources for food and agriculture

In recent years, the land area under agriculture has declined as also has the rate of growth in agricultural productivity while the demand for food continues to escalate. The world population now stands at 7 billion and is expected to reach 9 billion in 2045. A broad range of agricultural genetic diversity needs to be available and utilized in order to feed this growing population. Climate change is an added threat to biodiversity that will significantly impact genetic resources for food and agriculture (GRFA) and food production. There is no simple, all-encompassing solution to the challenges of increasing productivity while conserving genetic diversity. Sustainable management of GRFA requires a multipronged approach, and as outlined in the paper, biotechnologies can provide powerful tools for the management of GRFA. These tools vary in complexity from those that are relatively simple to those that are more sophisticated. Further, advances in biotechnologies are occurring at a rapid pace and provide novel opportunities for more effective and efficient management of GRFA. Biotechnology applications must be integrated with ongoing conventional breeding and development programs in order to succeed. Additionally, the generation, adaptation, and adoption of biotechnologies require a consistent level of financial and human resources and appropriate policies need to be in place. These issues were also recognized by Member States at the FAO international technical conference on Agricultural Biotechnologies for Developing Countries (ABDC-10), which took place in March 2010 in Mexico. At the end of the conference, the Member States reached a number of key conclusions, agreeing, inter alia, that developing countries should significantly increase sustained investments in capacity building and the development and use of biotechnologies to maintain the natural resource base; that effective and enabling national biotechnology policies and science-based regulatory frameworks can facilitate the development and appropriate use of biotechnologies in developing countries; and that FAO and other relevant international organizations and donors should significantly increase their efforts to support the strengthening of national capacities in the development and appropriate use of pro-poor agricultural biotechnologies.

The Importance of Animal Models in the Development of Vaccines

Efficient translation of basic vaccine research into clinical therapies greatly depends upon the availability of appropriate animal models. Testing novel vaccine candidates in animal models is a critical step in the development of modern vaccines. Animal models are being used to assess the quality and quantity of the immune response, to identify the optimal route of delivery and formulation, to determine protection from infection and disease transmission, and to evaluate the safety and toxicity of the vaccine formulation. Animal models help to make the translation from basic research to clinical application, and they often allow prediction of the vaccine potential, which helps in predicting the financial risks for vaccine manufacturers. Choosing an appropriate animal model has become increasingly important for the field, as each model has its own advantages and disadvantages. In this review, the criteria for selecting the right animal model, the advantages and disadvantages of various animal models, as well as the future needs for animal models are being discussed.

Use of inactivated Escherichia coli enterotoxins to enhance respiratory mucosal adjuvanticity during vaccination in swine

In order to augment responses to respiratory vaccines in swine, various adjuvants were intranasally coadministered with a foot-and-mouth disease virus (FMDV) antigen to pigs. Detoxified Escherichia coli enterotoxins LTK63 and LTR72 enhanced antigen-specific mucosal and systemic immunity, demonstrating their efficacy as adjuvants for nonreplicating antigens upon intranasal immunization in swine.

Efficacy of oral administration of a modified-live Salmonella Dublin vaccine in calves

OBJECTIVE

To determine the efficacy a modified-live Salmonella Dublin vaccine administered PO in an extralabel manner in the prevention of diseases associated with Salmonella Dublin infection.

DESIGN

Randomized clinical trial.

ANIMALS

288 preweaned Holstein dairy calves on a commercial dairy farm.

PROCEDURES

Calves were orally administered either 2 mL of a commercially available, modified-live Salmonella Dublin vaccine (n = 140) or a placebo (148) at 3 and 10 days of age. Signs of diarrhea and depression were recorded daily. Weight gain between 3 days of age and time of weaning was measured. Fecal samples from clinically depressed or diarrheic calves and fresh tissues samples from calves that died were submitted for bacterial culture of Salmonella organisms.

RESULTS

Salmonella organisms were isolated from samples of 1.4% (2/140) and 3.4% (5/148) of calves receiving the vaccine and placebo, respectively. Additionally, 57.1% (80/140) and 60.1 % (89/148) of the vaccinated and control calves, respectively, had at least 1 day with an abnormal fecal score. Calves receiving the vaccine and placebo were not significantly different in terms of overall morbidity rate, Salmonella-specific morbidity rate, or average daily gain. Adverse reactions related to administration of the vaccine were not seen. The attenuated vaccine strain was not isolated from any fecal or tissue samples.

CONCLUSIONS AND CLINICAL RELEVANCE

This method of vaccination was safe in young Holstein calves, although it was not effective in reducing the incidence of disease or improving weight gain on this farm. However, the power of this study was limited by a low incidence of clinical salmonellosis.

Adjuvants and delivery systems in veterinary vaccinology: current state and future developments

Modern adjuvants should induce strong and balanced immune responses, and it is often desirable to induce specific types of immunity. As an example, efficient Th1-immunity-inducing adjuvants are highly in demand. Such adjuvants promote good cell-mediated immunity against subunit vaccines that have low immunogenicity themselves. The development of such adjuvants may take advantage of the increased knowledge of the molecular mechanisms and factors controlling these responses. However, knowledge of such molecular details of immune mechanisms is relatively scarce for species other than humans and laboratory rodents, and in addition, there are special considerations pertaining to the use of adjuvants in veterinary animals, such as production and companion animals. With a focus on veterinary animals, this review highlights a number of approaches being pursued, including cytokines, CpG oligonucleotides, microparticles and liposomes.

Thermostable tag (TST) protein expression system: engineering thermotolerant recombinant proteins and vaccines

Methods to increase temperature stability of vaccines and adjuvants are needed to reduce dependence on cold chain storage. We report herein creation and application of pVEX expression vectors to improve vaccine and adjuvant manufacture and thermostability. Defined media fermentation yields of 6g/L thermostable toll-like receptor 5 agonist flagellin were obtained using an IPTG inducible pVEX-flagellin expression vector. Alternative pVEX vectors encoding Pyrococcus furiosus maltodextrin-binding protein (pfMBP) as a fusion partner improved Influenza hemagglutinin antigen vaccine solubility and thermostability. A pfMBP hemagglutinin HA2 domain fusion protein was a potent immunogen. Manufacturing processes that combined up to 5 g/L defined media fermentation yields with rapid, selective, thermostable pfMBP fusion protein purification were developed. The pVEX pfMBP-based thermostable tag (TST) platform is a generic protein engineering approach to enable high yield manufacture of thermostable recombinant protein vaccine components.

In silico analysis of chimeric espA, eae and tir fragments of Escherichia coli O157:H7 for oral immunogenic applications

Background

In silico techniques are highly suited for both the discovery of new and development of existing vaccines. Enterohemorrhagic Escherichia coli O157:H7 (EHEC) exhibits a pattern of localized adherence to host cells, with the formation of microcolonies, and induces a specific histopathological lesion (attaching/effacing). The genes encoding the products responsible for this phenotype are clustered on a 35-kb pathogenicity island. Among these proteins, Intimin, Tir, and EspA, which are expressed by attaching-effacing genes, are responsible for the attachment to epithelial cell that leads to lesions.

Results

We designed synthetic genes encoding the carboxy-terminal fragment of Intimin, the middle region of Tir and the carboxy-terminal part of EspA. These multi genes were synthesized with codon optimization for a plant host and were fused together by the application of four repeats of five hydrophobic amino acids as linkers. The structure of the synthetic construct gene, its mRNA and deduced protein and their stabilities were analyzed by bioinformatic software. Furthermore, the immunogenicity of this multimeric recombinant protein consisting of three different domains was predicted.

Conclusion

a structural model for a chimeric gene from LEE antigenic determinants of EHEC is presented. It may define accessibility, solubility and immunogenecity.

Recombinant porcine rotavirus VP4 and VP4-LTB expressed in Lactobacillus casei induced mucosal and systemic antibody responses in mice

Background

Porcine rotavirus infection is a significant cause of morbidity and mortality in the swine industry necessitating the development of effective vaccines for the prevention of infection. Immune responses associated with protection are primarily mucosal in nature and induction of mucosal immunity is important for preventing porcine rotavirus infection.

Results

Lactobacillus casei expressing the major protective antigen VP4 of porcine rotavirus (pPG612.1-VP4) or VP4-LTB (heat-labile toxin B subunit from Echerichia coli) (pPG612.1-VP4-LTB) fusion protein was used to immunize mice orally. The expression of recombinant pPG612.1-VP4 and pPG612.1-VP4-LTB was confirmed by SDS-PAGE and Western blot analysis and surface-displayed expression on L. casei was verified by immunofluorescence. Mice orally immunized with recombinant protein-expressing L. casei produced high levels of serum immunoglobulin G (IgG) and mucosal IgA. The IgA titters from mice immunized with pPG612.1-VP4-LTB were higher than titters from pPG612.1-VP4-immunized mice. The induced antibodies demonstrated neutralizing effects on RV infection.

Conclusion

These results demonstrated that VP4 administered in the context of an L. casei expression system is an effective method for stimulating mucosal immunity and that LTB served to further stimulate mucosal immunity suggesting that this strategy can be adapted for use in pigs.

Bovine neonate natural killer cells are fully functional and highly responsive to interleukin-15 and to NKp46 receptor stimulation

Natural killer (NK) cells are key components of the innate immune system with their killing and cytokine producing abilities. Bovine NK cells have been characterized as NKp46⁺/CD3⁻ lymphocytes, but little is known about these cells in neonatal calves. As the newborn calf, with an insufficiently developed acquired immunity, has to employ the innate immune system, we wanted to investigate whether neonate NK cells had the same characteristics as cells from older calves. Freshly isolated neonate and calf NK cells presented the same resting CD2⁺/CD25^low/CD8^−/low phenotype. Neonates less than 8 days old had one third of the circulating NKp46⁺ cells of older calves, but the NK cells proliferated more actively in vitro in the presence of interleukin (IL)-2 or IL-15. Moreover, neonate NK cells were more cytotoxic both in an NKp46 mediated redirected lysis assay and in direct killing of a bovine cell line MDBK when cultured in the presence of IL-15. Neonate and calf NK cells cultured in the presence of IL-2 and then stimulated with IL-12 produced similar dose-dependent interferon (IFN)-γ amounts, while IL-15 cultured NK cells did not give such a response whatever the age. However, neonatal NK cells cultured in IL-15 and stimulated by IL-12 concomitantly with cross-linking of NKp46, produced 4 to 5 times more IFN-γ than calf NK cells. These data suggest that although present in lower number at birth, neonate NK cells are fully functional and are more responsive to IL-15 and activation through the NKp46 receptor than NK cells from older calves.

Immunization with recombinant Brucella species outer membrane protein Omp16 or Omp19 in adjuvant induces specific CD4+ and CD8+ T cells as well as systemic and oral protection against Brucella abortus infection

Available vaccines against Brucella spp. are live attenuated Brucella strains. In order to engineer a better vaccine to be used in animals and humans, our laboratory aims to develop an innocuous subunit vaccine. Particularly, we are interested in the outer membrane proteins (OMPs) of B. abortus: Omp16 and Omp19. In this study, we assessed the use of these proteins as vaccines against Brucella in BALB/c mice. Immunization with lipidated Omp16 (L-Omp16) or L-Omp19 in incomplete Freund's adjuvant (IFA) conferred significant protection against B. abortus infection. Vaccination with unlipidated Omp16 (U-Omp16) or U-Omp19 in IFA induced a higher degree of protection than the respective lipidated versions. Moreover, the level of protection induced after U-Omp16 or U-Omp19 immunization in IFA was similar to that elicited by live B. abortus S19 immunization. Flow cytometric analysis showed that immunization with U-Omp16 or U-Omp19 induced antigen-specific CD4(+) as well as CD8(+) T cells producing gamma interferon. In vivo depletion of CD4(+) or CD8(+) T cells in mice immunized with U-Omp16 or U-Omp19 plus IFA resulted in a loss of the elicited protection, indicating that both cell types are mediating immune protection. U-Omp16 or U-Omp19 vaccination induced a T helper 1 response, systemic protection in aluminum hydroxide formulation, and oral protection with cholera toxin adjuvant against B. abortus infection. Both immunization routes exhibited a similar degree of protection to attenuated Brucella vaccines (S19 and RB51, respectively). Overall these results indicate that U-Omp16 or U-Omp19 would be a useful candidate for a subunit vaccine against human and animal brucellosis.

Actinobacillus pleuropneumoniaevaccines: from bacterins to new insights into vaccination strategies

With the growing emergence of antibiotic resistance and rising consumer demands concerning food safety, vaccination to prevent bacterial infections is of increasing relevance.Actinobacillus pleuropneumoniaeis the etiological agent of porcine pleuropneumonia, a respiratory disease leading to severe economic losses in the swine industry. Despite all the research and trials that were performed withA. pleuropneumoniaevaccination in the past, a safe vaccine that offers complete protection against all serotypes has yet not reached the market. However, recent advances made in the identification of new potential vaccine candidates and in the targeting of specific immune responses, give encouraging vaccination perspectives. Here, we review past and current knowledge onA. pleuropneumoniaevaccines as well as the newly available genomic tools and vaccination strategies that could be useful in the design of an efficient vaccine againstA. pleuropneumoniaeinfection.

Contagious bovine pleuropneumonia: a rationale for the development of a mucosal sub-unit vaccine

Contagious bovine pleuropneumonia (CBPP) remains a major cattle disease in Africa with serious socio-economic consequences. Its eradication requires the development of improved vaccines. Knowledge on this disease and its causing agent, Mycoplasma mycoides subsp. mycoides biotype Small Colony (MmmSC), has been progressing significantly in the last years, opening new areas for vaccine design. Advances were achieved in the understanding of the protective immune responses to MmmSC infection and immunopathological mechanisms allowing the pathogen to escape the host immune response. Based on sequencing and genomic studies, some virulence factors and metabolic pathways were unraveled leading to the identification of potential MmmSC vaccine candidates. Based on these findings, this review presents a scientific strategy to design multi-component sub-unit vaccines for mucosal delivery as the most promising approach for efficient long-term protective vaccines to prevent CBPP.

Use of animal models in the development of human vaccines

Over the past 100 years, animal infectious disease research has played a crucial role in the development of human vaccines. In fact, many of today's vaccines are based on utilizing animal pathogens, either in the form of an attenuated vaccine or as a vaccine vector. Vaccine development has become increasingly complex with chronic and newly emerging diseases, a demand for therapeutic vaccines for noninfectious diseases, extended vaccine in the neonate and the elderly, and increasing concerns regarding vaccine safety. Furthermore, the evaluation of quantity and quality of immune responses and the ability to efficiently translate the results of basic research into the clinic are critical to ensure that vaccines meet their therapeutic potential. Here, we review the importance of animal models for developing and testing novel human vaccines, discuss the limitations of existing animal models in knowledge translation, and summarize the needs and criteria for future animal models. We argue that efficient translation of basic vaccine research to clinical therapies will depend upon the availability of appropriate animal models to address each of the questions which arise during vaccine development.

Current status of veterinary vaccines

The major goals of veterinary vaccines are to improve the health and welfare of companion animals, increase production of livestock in a cost-effective manner, and prevent animal-to-human transmission from both domestic animals and wildlife. These diverse aims have led to different approaches to the development of veterinary vaccines from crude but effective whole-pathogen preparations to molecularly defined subunit vaccines, genetically engineered organisms or chimeras, vectored antigen formulations, and naked DNA injections. The final successful outcome of vaccine research and development is the generation of a product that will be available in the marketplace or that will be used in the field to achieve desired outcomes. As detailed in this review, successful veterinary vaccines have been produced against viral, bacterial, protozoal, and multicellular pathogens, which in many ways have led the field in the application and adaptation of novel technologies. These veterinary vaccines have had, and continue to have, a major impact not only on animal health and production but also on human health through increasing safe food supplies and preventing animal-to-human transmission of infectious diseases. The continued interaction between animals and human researchers and health professionals will be of major importance for adapting new technologies, providing animal models of disease, and confronting new and emerging infectious diseases.