Field efficacy of a recombinant toxoid vaccine against Shiga toxin 2e during a naturally occurring edema disease infection.

The objective of this field trial was to determine the efficacy of a recombinant toxoid vaccine against Shiga toxin 2e (Stx2e) in piglets suffering from edema disease (ED). Three farms with confirmed ED cases were selected for the field trials. On each farm, a total of 40 4-day-old pigs were randomly allocated to either the vaccinated or unvaccinated group, with 20 pigs per group (10 males and 10 females). A 1.0-mL dose of the recombinant toxoid vaccine was administered intramuscularly to pigs in the vaccinated groups in accordance with the manufacturer's recommendations at 4 d of age. A single 2.0-mL dose of phosphate-buffered saline was administered to unvaccinated pigs at the same age. Clinical signs of ED were observed in 12 piglets in the unvaccinated groups and 7 unvaccinated pigs died as a result of ED out of the total number of piglets on Farms A, B, and C. Vaccination had a positive effect on pig growth performance compared to that of unvaccinated pigs on 2 of the 3 farms. Seroconversion of neutralizing antibodies against Stx2e occurred in 70% of piglets in the vaccinated group on Farm A, 75% of vaccinated piglets on Farm B, and 55% of vaccinated piglets on Farm C, when detectable antibodies were measured at 17 d post-vaccination (dpv). Detectable antibodies were measured in 85% of vaccinated piglets on Farms A and B and in 90% of these piglets on Farm C at 37 dpv. These field trials determined that the ED recombinant toxoid vaccine successfully reduced clinical signs and mortality, improved average daily weight gain, and resulted in the production of neutralizing antibodies against Stx2e in pigs.

L'objectif de cette étude sur le terrain était de déterminer l'efficacité d'un vaccin à base d'anatoxine recombinante contre la toxine Shiga 2e (Stx2e) chez les porcelets souffrant de la maladie de l'oedème (ED). Trois fermes ayant des cas confirmés de ED ont été sélectionnées pour les études sur le terrain. Dans chaque ferme, un total de 40 porcs âgés de 4 jours ont été répartis au hasard dans le groupe vacciné ou non vacciné, avec 20 porcs par groupe (10 mâles et 10 femelles). Une dose de 1,0 ml du vaccin à base d'anatoxine recombinante a été administrée par voie intramusculaire aux porcs des groupes vaccinés conformément aux recommandations du fabricant à l'âge de 4 jours. Une dose unique de 2,0 ml de solution saline tamponnée au phosphate a été administrée aux porcs non vaccinés au même âge. Des signes cliniques de ED ont été observés chez 12 porcelets des groupes non vaccinés et 7 porcs non vaccinés sont morts des suites d'une maladie de l'oedème sur le nombre total de porcelets des fermes A, B et C. La vaccination a eu un effet positif sur les performances de croissance des porcs par rapport à celles des porcs non vaccinés dans 2 des 3 fermes. La séroconversion des anticorps neutralisants contre Stx2e s'est produite chez 70 % des porcelets du groupe vacciné de la ferme A, 75 % des porcelets vaccinés de la ferme B et 55 % des porcelets vaccinés de la ferme C, lorsque des anticorps détectables ont été mesurés 17 jours après la vaccination (dpv). Des anticorps détectables ont été mesurés chez 85 % des porcelets vaccinés des fermes A et B et chez 90 % de ces porcelets de la ferme C à 37 dpv. Ces études sur le terrain ont déterminé que le vaccin toxoïde recombinant ED réduisait avec succès les signes cliniques et la mortalité, améliorait le gain de poids quotidien moyen et entraînait la production d'anticorps neutralisants contre Stx2e chez les porcs.(Traduit par Docteur Serge Messier).

Flagellin Enhances the Immunogenicity of Pasteurella multocida Lipoprotein E Subunit Vaccine.

Fowl cholera, caused by Pasteurella multocida infection, poses challenges for prevention because of its many serotypes. Bacterins are currently widely used for vaccination against fowl cholera, but protection is limited to homologous strains. Live attenuated vaccines of P. multocida provide some heterologous protection, but side effects are considerable. More recently, protein-based antigens are promising subunit vaccines when their low immunogenicity has been addressed with effective adjuvants. Bacterial flagellin has been widely considered a promising adjuvant for vaccines. In this study, we tested the adjutancy of flagellin in a subunit vaccine against P. multocida in a mice and chicken models. For vaccine formulation, the antigen fPlpE (P. multocida liporotein E) was combined with fFliC (Salmonella Typhimurium flagellin). The recombinant proteins of fPlpE and fFliC were successfully expressed using the Escherichia coli system as the expected sizes of 55 kDa and 70 kDa, respectively. The fFliC elicited strong expression levels of proinflammatory cytokine (IL-1ß, IL-8, and IL-6) when stimulated in native chicken peripheral blood mononuclear cells. Immunization of mice and chickens with the subunit vaccines containing fFliC accelerated the antibody response. In the challenge tests, fFliC increased vaccine protective efficacy against the heterologous strain P. multocida A1 and highly virulent strain Chu01 in mice and chickens, respectively. These data indicated potential possibilities of using fFliC as an immunostimulant adjuvant in developing a subunit vaccine against fowl cholera.

Nota de Investigación- La flagelina aumenta la inmunogenicidad de una vacuna subunitaria que contiene lipoprote'ina E de Pasteurella multocida. La enfermedad del cólera aviar, causada por la infección por Pasteurella multocida, representa desaf'ios para la prevención debido a sus numerosos serotipos. Actualmente, las bacterinas se utilizan ampliamente para la vacunación contra el cólera aviar, pero la protección se limita a cepas homólogas. Las vacunas vivas atenuadas de P. multocida proporcionan cierta protección heteróloga, pero los efectos secundarios son considerables. Recientemente, el uso de ant'igenos basados en prote'inas parece ser prometedor como vacunas subunitarias cuando se ha abordado el problema de su baja inmunogenicidad con adyuvantes eficaces. La flagelina bacteriana se ha considerado ampliamente como un adyuvante prometedor para las vacunas. En este estudio, se analizó la capacidad como adyuvante de la flagelina en una vacuna de subunitaria contra P. multocida en modelos de ratones y pollos. Para la formulación de la vacuna, el ant'igeno fPlpE (liporote'ina E de P. multocida) se combinó con fFliC (flagelina de Salmonella Typhimurium). Las prote'inas recombinantes de fPlpE y fFliC se expresaron con éxito utilizando el sistema de E. coli con los tamaños esperados de 55 kDa y 70 kDa, respectivamente. El fFliC indujo fuertes niveles de expresión de citoquinas proinflamatorias (IL-1ß, IL-8 e IL-6) cuando se estimuló en células mononucleares de sangre periférica de pollos nativos. La inmunización de ratones y pollos con las vacunas subunitarias que contienen fFliC aceleró la respuesta de anticuerpos. En las pruebas de desaf'io, la fFliC aumentó la eficacia protectora de la vacuna contra la cepa heteróloga de P. multocida A1 y la cepa altamente virulenta Chu01 en ratones y pollos, respectivamente. Estos datos indicaron posibilidades potenciales de utilizar fFliC como adyuvante inmunoestimulante en el desarrollo de una vacuna subunitaria contra el cólera aviar.

Protection of Broiler Chickens Against Necrotic Enteritis by Intrapulmonary Delivery of a Live Clostridium perfringens Vaccine Exploiting the Gut-Lung-Axis Concept.

Clostridium perfringens (CP)-induced necrotic enteritis (NE) is an economically important disease in the broiler chicken industry. The incidence of NE is common in 3-to-6-wk-old broiler chickens, once maternal antibodies start declining. Developing an effective vaccination strategy against NE, preferably delivering a single dose of vaccine at hatch to protect broiler chickens against NE without a booster vaccine, is an enormous challenge. The objective of this study was to induce mucosal immunity in the intestines against NE by intrapulmonary (IPL) delivery of a live CP vaccine at hatch, exploiting the gut-lung-axis (GLA) concept by vaccine delivery following in ovo administration of cytosine-phosphorothioate-guanine oligodeoxynucleotides (CpG-ODN) to induce immune cell maturation in the lungs. Experiments were conducted to explore the dose of CP and immune protection against heterologous CP challenge, and to study the efficacy of IPL delivery of a CP vaccine without a booster. Additional studies were conducted to measure serum immunoglobulin (Ig)Y, mucosal IgA, and histopathology of lungs following vaccination. Delivery of a live CP vaccine by the IPL route, with or without in ovo CpG-ODN, provided significant protection against NE (P < 0.0001). Systemic IgY and mucosal IgA against CP were correlated with protection against NE. There was no necrosis or inflammation in the pulmonary parenchyma. There was a low number of CP isolated from the lungs following live CP delivery by the IPL route. A significant influx of (P < 0.001) of CD8+ T cells and macrophages were noted in the lungs 2 days following live CP delivery by the IPL route. IPL delivery of a live CP vaccine, rather than inactivated CP, provided better protection. This study demonstrated the utility in exploiting the GLA concept in vaccine delivery in broiler chickens.

Protección de pollos de engorde contra la enteritis necrótica mediante la administración intrapulmonar de una vacuna viva de Clostridium perfringens que aprovecha el concepto del eje intestino-pulmón. La enteritis necrótica (NE) inducida por Clostridium perfringens (CP) es una enfermedad económicamente importante en la industria de los pollos de engorde. La incidencia de enteritis necrótica es común en pollos de engorde de tres a seis semanas de edad, una vez que los anticuerpos maternos comienzan a disminuir. El desarrollo de una estrategia de vacunación eficaz contra la enteritis necrótica, preferiblemente administrando una dosis única de vacuna en la eclosión para proteger a los pollos de engorde contra dicha enfermedad sin la necesidad de aplicar una vacuna de refuerzo, es un desafío importante. El objetivo de este estudio fue inducir inmunidad de mucosas en los intestinos contra la enteritis necrótica mediante la administración intrapulmonar (IPL) de una vacuna de C. perfringens viva en la eclosión, explotando el concepto del eje intestino-pulmón (GLA) mediante la administración de la vacuna después de la administración in ovo de citosin oligodesoxinucleótidos de fosforotioato-guanina (CpG-ODN) para inducir la maduración de las células inmunitarias en los pulmones. Se realizaron experimentos para explorar la dosis de C. perfringens y la protección inmune contra la exposición heteróloga a C. perfringens, y para estudiar la eficacia de la administración intrapulmonar de una vacuna C. perfringens sin refuerzo. Se realizaron estudios adicionales para medir la inmunoglobulina (Ig)Y sérica, la IgA de mucosas y la histopatología de los pulmones después de la vacunación. La administración de una vacuna de C. perfringens viva por vía intrapulmonar, con o sin CpG-ODN in ovo, proporcionó una protección significativa contra la enteritis necrótica (P < 0.0001). La IgY sistémica y la IgA mucosa contra C. perfringens se correlacionaron con la protección contra la enteritis necrótica. No hubo necrosis ni inflamación en el parénquima pulmonar. Hubo un número bajo de C. perfringens aislado de los pulmones después de la administración de la vacuna viva contra C. perfringens por vía intrapulmonar. Se observó una afluencia significativa (P < 0.001) de células T CD8+ y macrófagos en los pulmones dos días después de la administración de C. perfringens viva por vía intrapulmonar. La administración mediante vía intrapulmonar de una vacuna viva contra C. perfringens, en lugar de la vacuna contra C. perfringens inactivada, proporcionó una mejor protección. Este estudio demostró la utilidad de explotar el concepto del eje intestino-pulmón en la administración de vacunas en pollos de engorde.

A multivalent mRNA-LNP vaccine protects against Clostridioides difficile infection.

Clostridioides difficile infection (CDI) is an urgent public health threat with limited preventative options. In this work, we developed a messenger RNA (mRNA)-lipid nanoparticle (LNP) vaccine targeting C. difficile toxins and virulence factors. This multivalent vaccine elicited robust and long-lived systemic and mucosal antigen-specific humoral and cellular immune responses across animal models, independent of changes to the intestinal microbiota. Vaccination protected mice from lethal CDI in both primary and recurrent infection models, and inclusion of non-toxin cellular and spore antigens improved decolonization of toxigenic C. difficile from the gastrointestinal tract. Our studies demonstrate mRNA-LNP vaccine technology as a promising platform for the development of novel C. difficile therapeutics with potential for limiting acute disease and promoting bacterial decolonization.

Trivalent outer membrane vesicles-based combination vaccine candidate induces protective immunity against Campylobacter and invasive non-typhoidal Salmonella in adult mice.

Campylobacter and invasive non-typhoidal Salmonella (iNTS) are among the most common causative agents of gastroenteritis worldwide. As of now, no single combination licensed vaccine is available for public health use against both iNTS and Campylobacter species. Outer-membrane vesicles (OMVs) are nanoscale proteoliposomes released from the surface of gram-negative bacteria during log phase and harbor a variety of immunogenic proteins. Based on epidemiology of infections, we formulated a novel trivalent outer membrane vesicles (TOMVs)-based vaccine candidate against Campylobacter jejuni (CJ), Salmonella Typhimurium (ST) and Salmonella Enteritidis (SE). Isolated OMVs from CJ, ST and SE were combined in equal ratios for formulation of TOMVs and 5 µg of the developed vaccine candidate was used for intraperitoneal immunization of adult BALB/c mice. Immunization with TOMVs significantly activated both the humoral and cellular arm of adaptive immune response. Robust bactericidal effect was elicited by TOMVs immunized adult mice sera. TOMVs immunization induced long-term protective efficacy against CJ, ST and SE infections in mice. The study illustrates the ability of TOMVs-based combination immunogen in eliciting broad-spectrum protective immunity against prevalent Campylobacter and iNTS pathogens. According to the findings, TOMVs can work as a potent combination-based acellular vaccine candidate for amelioration of Campylobacter and iNTS-mediated gastroenteritis.

Preferences for a Clostridioides difficile vaccine among adults in the United States.

INTRODUCTION: Clostridioides difficile (C.diff) infection (CDI) causes significant morbidity and mortality among older adults. Vaccines to prevent CDI are in development; however, data on the target population's preferences are needed to inform vaccination recommendations in the United States (US). This study assessed US adults' willingness to receive a C.diff vaccine and examined how vaccine attributes influence their choices. METHODS: A cross-sectional online survey with a discrete choice experiment (DCE) was conducted among US adults aged ≥50 years. DCE attributes included effectiveness, duration of protection, reduction in symptom severity, out-of-pocket (OOP) costs, number of doses, and side effects. The DCE included 11 choice tasks, each with two hypothetical vaccine profiles and an opt-out (i.e., no vaccine). Attribute-level preference weights were estimated using hierarchical Bayesian modeling. Attribute relative importance (RI) was compared between select subgroups. RESULTS: Of 1216 adults in the analyses, 29.9% reported they knew either 'a little' (20.7%) or 'a lot' (9.2%) about C.diff before the study. A C.diff vaccine was chosen 58.0% of the time (vs. opt-out) across choice tasks. It was estimated that up to 75.0% would choose a vaccine when OOP was $0. Those who were immunocompromised/high-risk for CDI (vs. not) more frequently chose a C.diff vaccine. Decreases in OOP costs (RI = 56.1), improvements in vaccine effectiveness (RI = 17.7), and reduction in symptom severity (RI = 10.3) were most important to vaccine choice. The rank ordering of attributes by importance was consistent across subgroups. CONCLUSION: OOP cost, improvements in vaccine effectiveness, and reduction in CDI severity were highly influential to vaccine selection. Most adults aged ≥50 years were receptive to a C.diff vaccine, especially with little-to-no OOP cost, suggesting that mandating insurance coverage of vaccination with no copayment may increase uptake. The limited awareness about C.diff among adults presents an opportunity for healthcare providers to educate their patients about CDI prevention.

Optimization and evaluation of a chitosan-coated PLGA nanocarrier for mucosal delivery of Porphyromonas gingivalis antigens.

Recent advances in understanding Alzheimer's disease (AD) suggest the possibility of an infectious etiology, with Porphyromonas gingivalis emerging as a prime suspect in contributing to AD. P. gingivalis may invade systemic circulation via weakened oral/intestinal barriers and then cross the blood-brain barrier (BBB), reaching the brain and precipitating AD pathology. Based on the proposed links between P. gingivalis and AD, a prospective approach is the development of an oral nanovaccine containing P. gingivalis antigens for mucosal delivery. Targeting the gut-associated lymphoid tissue (GALT), the nanovaccine may elicit both mucosal and systemic immunity, thereby hampering P. gingivalis ability to breach the oral/intestinal barriers and the BBB, respectively. The present study describes the optimization, characterization, and in vitro evaluation of a candidate chitosan-coated poly(lactic-co-glycolic acid) (PLGA-CS) nanovaccine containing a P. gingivalis antigen extract. The nanocarrier was prepared using the double emulsion solvent evaporation method and optimized for selected experimental factors, e.g. PLGA amount, surfactant concentration, w1/o phase ratio, applying a d-optimal statistical design to target the desired physicochemical criteria for its intended application. After nanocarrier optimization, the nanovaccine was characterized in terms of particle size, polydispersity index (PdI), ζ-potential, encapsulation efficiency (EE), drug loading (DL), morphology, and in vitro release profile, as well as for mucoadhesivity, stability under simulated gastrointestinal conditions, antigen integrity, in vitro cytotoxicity and uptake using THP-1 macrophages. The candidate PLGA-CS nanovaccine demonstrated appropriate physicochemical, mucoadhesive, and antigen release properties for oral delivery, along with acceptable levels of EE (55.3 ± 3.5 %) and DL (1.84 ± 0.12 %). The integrity of the encapsulated antigens remained uncompromised throughout NPs production and simulated gastrointestinal exposure, as confirmed by SDS-PAGE and Western blotting analyses. Furthermore, the nanovaccine showed effective in vitro uptake, while exhibiting low cytotoxicity. Taken together, these findings underscore the potential of PLGA-CS NPs as carriers for adequate antigen mucosal delivery, paving the way for further investigations into their applicability as vaccine candidates against P. gingivalis.

Immune response and safety of co-administered peste des petits ruminants, contagious caprine pleuropneumonia, sheep and goat pox, and Pasteurellosis vaccines in goats.

Background: Infectious diseases such as peste des petits ruminants (PPRs), contagious caprine pleuropneumonia (CCPP), sheep and goat pox (SGPX), and pasteurellosis have considerable impacts on the optimal utilization of sheep and goat resources in Ethiopia. Immunization using multiple vaccines administered simultaneously has been suggested as a cost-effective and safe approach to controlling and preventing these diseases. Aim: The aim of this study was to assess the immunogenicity and safety of multiple vaccines administered simultaneously in goats. Methods: Sero-negative PPR, CCPP, SGPX, and Pasteurellosis goats were immunized with multiple vaccines. Goats vaccinated with a single vaccine against each disease served as a positive control. The immune response of the goats was assessed using serological tests, and any adverse effects were monitored. Results: The results of the present study showed that goats vaccinated with multiple vaccines exhibited a remarkable immune response against PPR, CCPP, and pasteurellosis. In contrast, they did not produce a protective immune response against sheep or goat pox. No adverse effects were observed with any of the vaccines. Conclusion: This study suggested that combined vaccines can be effective at inducing a protective immune response in goats. However, further research is needed to fully understand the immune response to combined vaccines.

Enhancement of clinical signs in C3H/HeJ mice vaccinated with a highly immunogenic Leptospira methyl-accepting chemotaxis protein following challenge.

Leptospirosis is the most widespread zoonosis and a life-threatening disease in humans and animals. Licensed killed whole-cell vaccines are available for animals; however, they do not offer heterologous protection, do not induce long-term protection, or prevent renal colonization. In this study, we characterized an immunogenic Leptospira methyl-accepting chemotaxis protein (MCP) identified through a reverse vaccinology approach, predicted its structure, and tested the protective efficacy of a recombinant MCP fragment in the C3H/HeJ mice model. The predicted structure of the full-length MCP revealed an architecture typical for topology class I MCPs. A single dose of MCP vaccine elicited a significant IgG antibody response in immunized mice compared to controls (P < 0.0001), especially the IgG1 and IgG2a subclasses. The vaccination with MCP, despite eliciting a robust immune response, did not protect mice from disease and renal colonization. However, survival curves significantly differed between groups, and the MCP-vaccinated group developed clinical signs faster than the control group. There were differences in gross and histopathological changes between the MCP-vaccinated and control groups. The factors leading to enhanced disease process in vaccinated animals need further investigation. We speculate that anti-MCP antibodies may block the MCP signaling cascade and may limit chemotaxis, preventing Leptospira from reaching its destination, but facilitating its maintenance and replication in the blood stream. Such a phenomenon may exist in endemic areas where humans are highly exposed to Leptospira antigens, and the presence of antibodies might lead to disease enhancement. The role of this protein in Leptospira pathogenesis should be further evaluated to comprehend the lack of protection and potential exacerbation of the disease process. The absence of immune correlates of protection from Leptospira infection is still a major limitation of this field and efforts to gather this knowledge are needed.

Syphilis vaccine development: Aligning vaccine design with manufacturing requirements.

Syphilis, caused by Treponema pallidum subsp. pallidum, is a global health concern with increasing rates worldwide. Current prevention strategies, including screen-and-treat approaches, are not sufficient to resolve rising infection rates, emphasizing the need for a vaccine. Developing a syphilis vaccine necessitates a range of cross-disciplinary considerations, including essential disease-specific protection, technical requirements, economic feasibility, manufacturing constraints, public acceptance, equitable vaccine access, alignment with global public vaccination programs, and identification of essential populations to be vaccinated to achieve herd immunity. Central to syphilis vaccine development is prioritization of global vaccine availability, including access in low- to middle-income settings. Various vaccine platforms, including subunit, virus-like particle (VLP), mRNA, and outer membrane vesicle (OMV) vaccines, present both advantages and challenges. The proactive consideration of both manufacturing feasibility and efficacy throughout the pre-clinical research and development stages is essential for producing an efficacious, inexpensive, and scalable syphilis vaccine to address the growing global health burden caused by this disease.

Oral administration of Lactobacillus plantarum expressing aCD11c modulates cellular immunity alleviating inflammatory injury due to Klebsiella pneumoniae infection.

BACKGROUND: Klebsiella pneumoniae (KP), responsible for acute lung injury (ALI) and inflammation of the gastrointestinal tract, is a zoonotic pathogen that poses a threat to livestock farming worldwide. Nevertheless, there is currently no validated vaccine to prevent KP infection. The development of mucosal vaccines against KP using Lactobacillus plantarum (L. plantarum) is an effective strategy. RESULTS: Firstly, the L. plantarum strains NC8-pSIP409-aCD11c' and NC8-pLc23-aCD11c were constructed via homologous recombination to express the aCD11c protein either inducibly or constitutively. Both NC8-pSIP409-aCD11c' and NC8-pLc23-aCD11c strains could enhance the adhesion and invasion of L. plantarum on bone marrow-derived dendritic cells (BMDCs), and stimulate the activation of BMDCs compared to the control strain NC8-pSIP409 in vitro. Following oral immunization of mice with NC8-pSIP409-aCD11c' and NC8-pLc23-aCD11c, the cellular, humoral, and mucosal immunity were significantly improved, as evidenced by the increased expression of CD4+ IL-4+ T cells in the spleen, IgG in serum, and secretory IgA (sIgA) in the intestinal lavage fluid (ILF). Furthermore, the protective effects of L. plantarum against inflammatory damage caused by KP infection were confirmed by assessing the bacterial loads in various tissues, lung wet/dry ratio (W/D), levels of inflammatory cytokines, and histological evaluation, which influenced T helper 17 (Th17) and regulatory T (Treg) cells in peripheral blood and lung. CONCLUSIONS: Both the inducible and constitutive L. plantarum strains NC8-pSIP409-aCD11c' and NC8-pLc23-aCD11c have been found to stimulate cellular and humoral immunity levels and alleviate the inflammatory response caused by KP infection. These findings have provided a basis for the development of a novel vaccine against KP.

Novel recombinant vaccinia virus-vectored vaccine affords complete protection against homologous Borrelia burgdorferi infection in mice.

The rising prevalence of Lyme disease (LD) in North America and Europe has emerged as a pressing public health concern. Despite the availability of veterinary LD vaccines, no vaccine is currently available for human use. Outer surface protein C (OspC) found on the outer membrane of the causative agent, Borrelia burgdorferi, has been identified as a promising target for LD vaccine development due to its sustained expression during mammalian infection. However, the efficacy and immunological mechanisms of LD vaccines solely targeting OspC are not well characterized. In this study, we developed an attenuated Vaccinia virus (VV) vectored vaccine encoding type A OspC (VV-OspC-A). Two doses of the VV-OspC-A vaccine conferred complete protection against homologous B. burgdorferi challenge in mice. Furthermore, the candidate vaccine also prevented the development of carditis and lymph node hyperplasia associated with LD. When investigating the humoral immune response to vaccination, VV-OspC-A was found to induce a robust antibody response predominated by the IgG2a subtype, indicating a Th1-bias. Using a novel quantitative flow cytometry assay, we also determined that elicited antibodies were capable of inducing antibody-dependent cellular phagocytosis in vitro. Finally, we demonstrated that VV-OspC-A vaccination generated a strong antigen-specific CD4+ T-cell response characterized by the secretion of numerous cytokines upon stimulation of splenocytes with OspC peptides. This study suggests a promising avenue for LD vaccine development utilizing viral vectors targeting OspC and provides insights into the immunological mechanisms that confer protection against B. burgdorferi infection.

Evaluation of virulence of Aeromonas veronii strain GZ21-2 and development of a highly effective vaccine for grass carp with the potential for industrial application.

Bacterial septicemia represents a significant disease affecting cultured grass carp culture, with the primary etiological agent identified as the Gram-negative bacterium Aeromonas veronii. In response to an outbreak of septicemia in Guangzhou, we developed a formaldehyde-inactivated vaccine against an A. veronii strain designated AV-GZ21-2. This strain exhibited high pathogenicity in experimental infections across at all developmental stages of grass carp. Mortality rates for grass carp weighing 15 ± 5 g ranged from 16 % to 92 % at exposure temperatures of 19 °C-34 °C, respectively. The median lethal dose (LD50) for grass carp groups weighing 15 ± 5 g, 60 ± 10 g, 150 ± 30 g and 500 ± 50 g were determined to be 1.43, 2.52, 4.65 and 7.12 × 107(CFU/mL), respectively. We investigated the inactivated vaccine in conbination with aluminum hydroxide gel (AV-AHG), Montanide ISA201VG (AV-201VG), and white oil (AV-WO) adjuvants. This study aimed to optimize inactivation conditions and identify the adjuvant that elicits the most robust immune response. The AV-GZ21-2 inactivated bacterial solution (AV),when combined with various adjuvants, was capable of inducing a strong specific immune response in grass carp. The relative percent survival (RPS) following a lethal challenge with AV-GZ21-2 were 94 % for AV-AHG, 88 % for AV-201VG, 84 % for AV-WO and 78 % for AV alone. The minimum immunization dose of the AV-AHG vaccine was determined to be 6.0 × 107 CFU per fish, providing immunity for a duration of six months with an immune protection level exceeding 75 %. Furthermore, the AV-AHG vaccine demonstrated significant protective efficacy against various epidemic isolates of A. veronii. Consequently, we developed an inactivated vaccine targeting a highly pathogenic strain of A. veronii, incorporating an aluminum hydroxide gel adjuvant, which resulted in high immune protection and a duration of immunity exceeding six months. These findings suggest that the AV-AHG vaccine holds substantial potential for industrial application.

Vaccination with a trivalent Klebsiella pneumoniae vaccine confers protection in a murine model of pneumonia.

Klebsiella pneumoniae (K. pneumoniae) is an opportunistic pathogen and the major cause of healthcare-associated infections, which are increasingly complicated by the prevalence of highly invasive and hyper-virulent K. pneumoniae strains, necessitating the development of alternative strategies for combatting infections caused by this bacterium. In this study, we successfully constructed a fusion antigen called KP-Ag1, comprising three antigens (GlnH, FimA, and KPN_00466) that were previously identified through reverse vaccinology. Immunization with KP-Ag1 formulated with Al(OH)3 adjuvant elicited robust humoral and cellular immune response in mice, and conferred protective immunity in a murine model of K. pneumoniae lung infection. Further analysis of serum IgG subtypes from mice immunized with KP-Ag1 revealed a predominant IgG1 response, indicating that KP-Ag1 predominantly induces a Th2-biased immune response. Additionally, opsonophagocytic killing assay suggested that humoral immune responses play a pivotal role in mediating protection conferred by KP-Ag1. Moreover, KP-Ag1 was found to promote the activation and maturation of BMDCs in vitro, which is essential for subsequent efficient antigen presentation. More importantly, vaccination with KP-Ag1 demonstrated cross-protective efficacy against clinical isolates of K. pneumoniae varying in serotypes, antibiotic resistance, and virulence profiles. Therefore, KP-Ag1 holds promise as a candidate for K. pneumoniae vaccine development.

Shedding reduction and immunity modulation in piglets with an inactivated Mycoplasma hyopneumoniae vaccine encapsulated in nanostructured SBA-15 silica.

Mycoplasma (M.) hyopneumoniae is a primary etiological agent of porcine enzootic pneumonia (PEP), a disease that causes significant economic losses to pig farming worldwide. Current commercial M. hyopneumoniae vaccines induce partial protection, decline in preventing transmission of this pathogen or inducing complete immunity, evidencing the need for improving vaccines against PEP. In our study, we aimed to test the effectiveness of the SBA-15 ordered mesoporous silica nanostructured particles as an immune adjuvant of a vaccine composed of M. hyopneumoniae strain 232 proteins encapsulated in SBA-15 and administered by intramuscular route in piglets to evaluate the immune responses and immune-protection against challenge. Forty-eight 24-day-old M. hyopneumoniae-free piglets were divided into four experimental groups with different protocols, encompassing a commercial vaccine against M. hyopneumoniae, SBA-15 vaccine, SBA-15 adjuvant without antigens and a non-immunized group. All piglets were challenged with the virulent strain 232 of M. hyopneumoniae. Piglets that received the SBA-15 and commercial vaccine presented marked immune responses characterized by anti-M. hyopneumoniae IgA and IgG antibodies in serum, anti-M. hyopneumoniae IgA antibodies in nasal mucosa and showed an upregulation of IL-17 and IL-4 cytokines and downregulation of IFN-γ in lungs 35 days post-infection. Piglets immunized with SBA-15 vaccine presented a reduction of bacterial shedding compared to piglets immunized with a commercial bacterin. In addition, piglets from SBA-15 adjuvant suspension group presented increased IL-17 gene expression in the lungs without involvement of Th1 and Th2 responses after challenge. These results indicated that SBA-15 vaccine induced both humoral and cell-mediated responses in the upper respiratory tract and lungs, first site of replication and provided protection against M. hyopneumoniae infection with a homologous strain with reduction of lung lesions and bacterial shedding. Finally, these results enhance the potential use of new technologies such as nanostructured particles applied in vaccines for the pig farming industry.

Vaccination with a Lawsonia intracellularis subunit water in oil emulsion vaccine mitigated some disease parameters but failed to affect shedding.

Lawsonia intracellularis is the causative agent of ileitis in swine that manifests as slower weight gain, mild or hemorrhagic diarrhea and/or death in severe cases. As an economically important swine pathogen, development of effective vaccines is important to the swine industry. In developing a subunit vaccine with three recombinant antigens - FliC, GroEL and YopN - we wanted to identify a formulation that would produce robust immune responses that reduce disease parameters associated with Lawsonia intracellularis infection. We formulated these three antigens with four adjuvants: Montanide ISA 660 VG, Montanide Gel 02 PR, Montanide IMS 1313 VG NST, and Montanide ISA 61 VG in an immunogenicity study. Groups vaccinated with formulations including Montanide ISA 660 VG or Montanide ISA 61 VG had significantly more robust immune responses than groups vaccinated with formulations including Montanide Gel 02 PR or Montanide IMS 1313 VG NST. In the challenge study, animals vaccinated with these antigens and Montanide ISA 61 VG had reduced lesion scores, reduced lesion lengths, and increased average daily gain, but no reduction in shedding relative to the control animals. This work shows that this vaccine formulation should be considered for future study in a field and performance trial.

A field evaluation of a new porcine circovirus type 2d and Mycoplasma hyopneumoniae bivalent vaccine in herds suffering from subclinical PCV2d infection and enzootic pneumonia.

BACKGROUND: This field efficacy study was designed to determine the efficacy of a new bivalent vaccine containing porcine circovirus type 2d (PCV2d) and Mycoplasma hyopneumoniae at three independent pig farms. METHODS: Three pig farms were selected based on their history of subclinical PCV2 infection and enzootic pneumonia. Each farm housed a total of 40, 18-day-old pigs that were randomly allocated to 1 of 2 treatment groups. Pigs were administered a 2.0 mL dose of the bivalent vaccine intramuscularly at 21 days of age in accordance with the manufacturer's recommendations, whereas unvaccinated pigs were administered a single dose of phosphate-buffered saline at the same age. RESULTS: Clinically, the average daily weight gain of vaccinated groups was significantly higher (p < 0.05) than those of unvaccinated animals during the growing (70-112 days of age), finishing (112-175 days of age) and overall (3-175 days of age) stages of production. Vaccinated animals elicited neutralizing anti-PCV2 antibodies and PCV2d-specific interferon-γ secreting cells (IFN-γ-SC), which reduced the amount of PCV2d genomic copies in blood and reduced lymphoid lesions severity when compared with unvaccinated animals. Similarly, vaccinated animals elicited M. hyopneumoniae-specific IFN-γ-SC, which reduced the amount of M. hyopneumoniae in the larynx and reduced lung lesions severity. CONCLUSIONS: The result of the field trial demonstrated that the bivalent vaccine was efficacious in the protection of swine herds suffering from subclinical PCV2d infection and enzootic pneumonia.

Immunogenicity of a pentavalent recombinant Escherichiacoli bacterin against enterotoxemia and botulism in sheep.

INTRODUCTION: Producing commercial bacterins/toxoids against Clostridium spp. is laborious and hazardous. Conversely, developing prototype vaccines using purified recombinant toxoids, though safe and effective, is both laborious and costly for application in production animals. OBJECTIVE: Considering that inactivated recombinant Escherichiacoli (bacterin) is a simple, cost-effective, and to be safe solution, we evaluated, for the first time, a pentavalent formulation of recombinant bacterins containing the alpha, beta, and epsilon toxins of Clostridiumperfringens and C and D neurotoxins of Clostridiumbotulinum in sheep. METHODS: Subcutaneously, 18 Texel sheep received two doses (200 µg of each antigen) of recombinant bacterin (n = 7) or purified recombinant antigens (n = 6) on days 0 and 28, while the control group (n = 5) did not receive an immunization. Sera samples from days 0 (before the 1st dose), 28 (before the 2nd dose), and 56, 84, and 112 were used for measuring IgG (indirect ELISA) and neutralizing antibodies (mouse serum neutralization). RESULTS: Both formulations induced significant levels of IgG against all five toxins (p < 0.05) up to day 112, with peaks at days 28 and 56 post-immunization. The expected booster effect occurred only for the botulinum toxins. The neutralizing antibody titers were satisfactory against ETX (≥2 IU/ml for both formulations) and BoNT-D [5 IU/ml (bacterin) and 10 IU/ml (purified)]. CONCLUSION: While adjustments are required, the recombinant bacterin platform holds great potential for polyvalent vaccines due to its straightforward, safe, and cost-effective production, establishing it as a user-friendly technology for the veterinary immunobiological industry.

Development of two recombinant vaccines against Clostridioides difficile infection and immunogenicity in pregnant sows and neonatal piglets.

INTRODUCTION: Clostridioides difficile is the main cause of antibiotic-associated diarrhea in humans and is a major enteropathogen in several animal species. In newborn piglets, colonic lesions caused by C. difficile A and B toxins (TcdA and TcdB, respectively) cause diarrhea and significant production losses. OBJECTIVE: The present study aimed to develop two recombinant vaccines from immunogenic C-terminal fragments of TcdA and TcdB and evaluate the immune response in rabbits and in breeding sows. Two vaccines were produced: bivalent (rAB), consisting of recombinant fragments of TcdA and TcdB, and chimeric (rQAB), corresponding to the synthesis of the same fragments in a single protein. Groups of rabbits were inoculated with 10 or 50 µg of proteins adjuvanted with aluminum or 0.85 % sterile saline in a final volume of 1 mL/dose. Anti-TcdA and anti-TcdB IgG antibodies were detected in rabbits and sows immunized with both rAB and rQAB vaccines by ELISA. The vaccinated sows were inoculated intramuscularly with 20 µg/dose using a prime-boost approach. RESULTS: Different antibody titers (p ≤ 0.05) were observed among the vaccinated groups of sows (rAB and rQAB) and control. Additionally, newborn piglets from vaccinated sows were also positive for anti-TcdA and anti-TcdB IgGs, in contrast to control piglets (p ≤ 0.05). Immunization of sows with the rQAB vaccine conferred higher anti-TcdA and anti-TcdB responses in piglets, suggesting the superiority of this compound over rAB. CONCLUSION: The synthesized recombinant proteins were capable of inducing antibody titers against C. difficile toxins A and B in sows, and were passively transferred to piglets through colostrum.