Infectious respiratory diseases caused by Bordetella bronchiseptica (Bb) are seriously endangering the development of the rabbit industry in China. Unfortunately, no licensed vaccines are available for this pathogen. The present study was designed to determine whether the inactivated Bb antigen formulated with vegetable oil adjuvant (named E515) which contains soybean oil, vitamin E, and ginseng saponins, functions as a safe and effective vaccine (E515-Bb) against Bb infection in rabbits. Based on local and systemic reactions, both the E515 adjuvant alone and the E515-Bb vaccine exhibited good safety in rabbits. Immune response analysis implies that rabbits immunized with the E515-Bb vaccine produced significantly higher, earlier, and longer-lasting specific antibody responses and activated Th1/Th2/Th17 cell responses than those immunized with the aluminum hydroxide (Alum)-adjuvanted Bb vaccine (Alum-Bb) or Bb antigen alone. Moreover, the E515-Bb vaccine effectively protected rabbits from Bb infection. Additionally, integrated multi-omics analysis revealed that the immunoprotective effect of the E515-Bb vaccine was achieved through upregulation of the complement and coagulation cascades and cell adhesion molecule (CAM) pathways, and the downregulation of the P53 pathway. Overall, these results indicate that the E515-Bb vaccine is safe, elicits an efficient immune response and provides good protection against Bb infection in rabbits. Thus, the E515-adjuvanted Bb vaccine can be considered a promising candidate vaccine for preventing Bb infection.

This study aimed to determine the prevalence of bacterial diseases in pig farms in various regions of Zhejiang Province and surrounding areas. A total of 526 samples were collected from 85 pig farms in Zhejiang Province and surrounding areas. In this study, samples were analyzed using bacterial isolation and purification, Gram staining, PCR amplification, and antimicrobial susceptibility testing. A total of 36 Pasteurella multocida (Pm) isolates were detected, with an isolation rate of 6.84%; 37 Bordetella bronchiseptica (Bb) isolates were detected, with an isolation rate of 7.03%; 60 Glasserella parasuis (G. parasuis) isolates were detected, with an isolation rate of 11.41%; 170 Escherichia coli (E. coli) isolates were detected, with an isolation rate of 32.32%; 67 Streptococcus suis (SS) isolates were detected, with an isolation rate of 12.74%; 44 Actinobacillus pleuropneumoniae (APP) isolates were detected, with an isolation rate of 8.37%; and 7 Salmonella enteritis (SE) isolates were detected, with an isolation rate of 1.33%. Antimicrobial drug susceptibility testing against 21 types of antibiotics was carried out on the isolated strains, and the results showed that 228 strains had varying degrees of resistance to 21 antibiotics, including Pm, Bb, E. coli, and APP, with the highest resistance to lincomycin, at 100%. Pm and APP were the most sensitive to cephalothin, with resistance rates of 0. In terms of strains, Pm had the highest overall sensitivity to 21 antibiotics, and E. coli had the highest resistance. In short, bacterial diseases in Zhejiang and the surrounding areas were harmful, and the drug resistance situation was severe. This study provides scientific guidance for the clinical treatment of bacterial diseases.

Cyniclomyces guttulatus is usually recognised as an inhabitant of the gastrointestinal (GI) tract in rabbits. However, large numbers of C. guttulatus are often detected in the faeces of diarrhoeic rabbits. The relationship of C. guttulatus with rabbit diarrhoea needs to be clearly identified. In this study, a C. guttulatus Zhejiang strain was isolated from a New Zealand White rabbit with severe diarrhoea and then inoculated into SPF New Zealand white rabbits alone or co-inoculated with Eimeriaintestinalis, another kind of pathogen in rabbits. Our results showed that the optimal culture medium pH and temperature for this yeast were pH 4.5 and 40–42 °C, respectively. The sequence lengths of the 18S and 26S ribosomal DNA fragments were 1559 bp and 632 bp, respectively, and showed 99.8% homology with the 18S ribosomal sequence of the NRRL Y-17561 isolate from dogs and 100% homology with the 26S ribosomal sequence of DPA-CGR1 and CGDPA-GP1 isolates from rabbits and guinea pigs, respectively. In animal experiments, the C. guttulatus Zhejiang strain was not pathogenic to healthy rabbits, even when 1 × 10⁸ vegetative cells were used per rabbit. Surprisingly, rabbits inoculated with yeast showed a slightly better body weight gain and higher food intake. However, SPF rabbits co-inoculated with C. guttulatus and E. intestinalis developed more severe coccidiosis than rabbits inoculated with C. guttulatus or E. intestinalis alone. In addition, we surveyed the prevalence of C. guttulatus in rabbits and found that the positive rate was 83% in Zhejiang Province. In summary, the results indicated that C. guttulatus alone is not pathogenic to healthy rabbits, although might be an opportunistic pathogen when the digestive tract is damaged by other pathogens, such as coccidia.

Background/Objectives: The current Bordetella bronchiseptica (Bb) vaccine, when adjuvanted with alum, does not elicit adequate robust cellular immunity or effective antibody defense against Bb attacks. Unfortunately, antibiotic treatment generally represents an ineffective strategy due to the development of resistance against a broad range of antibiotics. Methods: The present study was designed to investigate the immune response, protective capabilities and underlying mechanisms of a plant oil-based adjuvant E515 formulated with inactivated Bb antigen as a potential vaccine candidate against Bordetella bronchiseptica. Results: Immunization studies revealed that a combination of SO, VE and GS (E515) exhibited a good synergistic adjuvant effect. The E515 adjuvanted Bb vaccine was proven to be highly efficacious and induced a mixed Th1/Th2/Th17 immune response in mice, leading to a significant increase in Bb-specific IgG, IgG1 and IgG2a antibodies, proliferative lymphocyte responses and cytokine levels (by lymphocytes and serum) and effectively induced responses by CD4⁺ TE, TM cells and B cells. The E515 adjuvant significantly enhanced the immune protection provided by the Bb vaccine in a mice model, as indicated by a reduced bacterial burden in the lungs. Multi-omics sequencing analysis revealed that E515 functions as an adjuvant by modulating critical pathways, including cytokine–cytokine receptor interaction, the IL-17 signaling pathway and the chemokine signaling pathway. This modulation also included interactions with beneficial species of bacteria including Alistipes, Odoribacter and Colidextribacter, as well as energy and lipid-related metabolites, thus highlighting its role as an immunomodulatory agent. Conclusion: Collectively, our results demonstrate the huge potential of E515-Bb vaccine candidates, thus highlighting the vegetable oil original adjuvant E515 as a promising agent for the development of new veterinary vaccines.

Background: Inactivated Pasteurella multocida (Pm) vaccines are safe and practical for veterinary use, but their protection is often limited by weak cellular immune activation and insufficient durability of antibody responses. This study investigated whether a tea saponin–soybean oil submicron emulsion could improve the durability, breadth and protective efficacy of immune responses induced by an inactivated P. multocida vaccine. Methods: Inactivated P. multocida antigen was formulated with tea saponin and soybean oil to generate TS-Pm. The formulation was characterized by particle size, polydispersity, surface charge, morphology and storage stability. Macrophage antigen uptake, cytokine secretion and activation-associated surface markers were examined in vitro . In mice, we evaluated antibody persistence, B-cell differentiation, splenic cellular immunity, pulmonary CD11b ⁺ myeloid phenotypes, systemic tolerability, protection after lethal challenge and draining lymph-node proteomic profiles. Results: TS-Pm formed a stable oil-in-water submicron emulsion of approximately 300 nm with low polydispersity, negative surface charge and preserved morphology after 6 months at 4 °C. In RAW264.7 macrophages, TS-Pm increased antigen uptake, pro-inflammatory cytokine production and CD80, CD86 and MHC-II expression. Compared with alum-adjuvanted vaccine, TS-Pm maintained higher Pm-specific IgG responses, increased both IgG1 and IgG2a, and promoted plasmablast, plasma cell and germinal-center-associated B-cell responses. TS-Pm also enhanced antigen-responsive splenic proliferation, cytokine-producing CD4 ⁺ and CD8 ⁺ T-cell subsets, and activation-associated phenotypes in pulmonary CD11b ⁺ myeloid cells. After lethal challenge, TS-Pm improved survival to 90%, compared with 60% for Alum-Pm, and reduced pulmonary bacterial burden and lung pathology without evidence of aggravated systemic injury. Draining lymph-node proteomics showed changes associated with antigen processing and presentation, NF-κB-related signaling and immune-cell trafficking. Conclusion: Tea saponin–soybean oil submicron emulsion improved the durability, breadth and protective efficacy of immune responses induced by an inactivated P. multocida vaccine. These findings identify TS-Pm as a practical plant-derived adjuvant formulation for inactivated bacterial vaccines requiring sustained humoral and cellular immunity.