Duck enteritis virus and Pasteurella multocida are major duck pathogens that induce duck plague and fowl cholera, respectively, in ducks and other waterfowl populations, leading to high levels of morbidity and mortality. Immunization with live attenuated DEV vaccine containing P. multocida outer membrane protein H (OmpH) can provide the most effective protection against these two infectious diseases in ducks. We have recently reported the construction of recombinant DEV expressing P. multocida ompH gene using the CRISPR/Cas9 gene editing strategy with the goal of using it as a bivalent vaccine that can simultaneously protect against both infections. Here we describe the findings of our investigation into the systemic immune responses, potency and clinical protection induced by the two recombinant DEV-ompH vaccine constructs, where one copy each of the ompH gene was inserted into the DEV genome at the UL55-LORF11 and UL44-44.5 intergenic regions, respectively. Our study demonstrated that the insertion of the ompH gene exerted no adverse effect on the DEV parental virus. Moreover, ducklings immunized with the rDEV-ompH-UL55 and rDEV-ompH-UL44 vaccines induced promising levels of P. multocida OmpH-specific as well as DEV-specific antibodies and were completely protected from both diseases. Analysis of the humoral and cellular immunity confirmed the immunogenicity of both recombinant vaccines, which provided strong immune responses against DEV and P. multocida. This study not only provides insights into understanding the immune responses of ducks to recombinant DEV-ompH vaccines but also demonstrates the potential for simultaneous prevention of viral and bacterial infections using viral vectors expressing bacterial immunogens.

Fowl cholera is caused by the bacterium Pasteurella multocida, a highly transmissible avian ailment with significant global implications, leading to substantial economic repercussions. The control of fowl cholera outbreaks primarily relies on vaccination using traditional vaccines that are still in use today despite their many limitations. In this research, we describe the development of a genetically engineered herpesvirus of turkeys (HVT) that carries the OmpH gene from P. multocida integrated into UL 45/46 intergenic region using CRISPR/Cas9-NHEJ and Cre-Lox system editing. The integration and expression of the foreign cassettes were confirmed using polymerase chain reaction (PCR), indirect immunofluorescence assays, and Western blot assays. The novel recombinant virus (rHVT-OmpH) demonstrated stable integration of the OmpH gene even after 15 consecutive in vitro passages, along with similar in vitro growth kinetics as the parent HVT virus. The protective efficacy of the rHVT-OmpH vaccine was evaluated in vaccinated ducks by examining the levels of P. multocida OmpH-specific antibodies in serum samples using ELISA. Groups of ducks that received the rHVT-OmpH vaccine or the rOmpH protein with Montanide™ (SEPPIC, Paris, France) adjuvant exhibited high levels of antibodies, in contrast to the negative control groups that received the parental HVT or PBS. The recombinant rHVT-OmpH vaccine also provided complete protection against exposure to virulent P. multocida X-73 seven days post-vaccination. This outcome not only demonstrates that the HVT vector possesses many characteristics of an ideal recombinant viral vaccine vector for protecting non-chicken hosts, such as ducks, but also represents significant research progress in identifying a modern, effective vaccine candidate for combatting ancient infectious diseases.

The intracellular bacterium Ehrlichia canis is the causative pathogen of canine monocytic ehrlichiosis (CME) in dogs. Despite its veterinary and medical importance, there is currently no available vaccine against this pathogen. In this study, the recombinant GP19 (rGP19) was produced and used as a recombinant vaccine prototype in a mouse model against experimental E. canis infection. The efficacy of the rGP19 vaccine prototype in the part of stimulating B and T cell responses and conferring protection in mice later challenged with E. canis pathogen were evaluated. The rGP19-specific antibody response was evaluated by ELISA after E. canis challenge exposure (on days 0, 7, and 14 post-challenge), and demonstrated significantly higher mean antibody levels in rGP19-immunized mice compared with adjuvant-immunized and naive mice. Significantly lower ehrlichial loads in blood, liver, and spleen DNA samples were detected in the immunized mice with rGP19 by qPCR. The up-regulation of IFNG and IL1 mRNA expression were observed in mice immunized with rGP19. In addition, this study detected IFN-γ-producing memory CD4+ T cells in the rGP19-immunized mice and later infected with E. canis on day 14 post-infection period using flow cytometry. The present study provided a piece of evidence that rGP19 may eliminate E. canis by manipulating Th1 and B cell roles and demonstrated a promising strategy in vaccine development against E. canis infection in the definitive host for further study.

Toxoplasmosis is a significant parasitic zoonosis caused by Toxoplasma gondii. Among livestock animals, small ruminants, especially sheep and goats, are the most infected. This infection is a leading cause of abortion, resulting in considerable economic losses for goat breeders. The present study aimed to assess the prevalence of T. gondii infection in goats in northern Thailand, with an emphasis on its potential zoonotic transmission to humans. Polymerase chain reaction (PCR) targeting the T. gondii dihydrofolate reductase-thymidylate synthase (Tgdhfr-ts) gene was employed for molecular detection. This represents the first report of T. gondii molecular detection in blood samples from small ruminants in Thailand by PCR. A total of 176 meat goat blood samples were analyzed, yielding an 8.52% (15/176) positivity rate for T. gondii DNA. The selected DNA sequences from the positive T. gondii DNA displayed a high degree of nucleotide sequence homology with the reference Tgdhfr-ts sequence. Phylogenetic analysis revealed a single clade alongside other T. gondii strains, showing no differentiation based on genotype. This study contributes to the understanding of T. gondii epidemiology and provides a foundation for future strategies to control and manage T. gondii transmission in livestock populations.

Metastasis-related disease is a major cause of death in canine mammary tumours (CMTs). Immunotherapy has been investigated due to the less successful outcomes of systemic therapy. This study aims to examine the expression of Programmed Cell Death Ligand-1 (PD-L1) in canine mammary tumours in dogs of Chiang Mai, Thailand, and determine the relationship between the level of mRNA expression and clinicopathologic characteristics. A total of 28 CMT samples were collected at the Small Animal Hospital, Chiang Mai University. Quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) and western blot assays were performed. The results revealed that all CMTs in this study expressed PD-L1 mRNA and PD-L1 protein. The mean relative mRNA expression showed no significant differences between groups categorized by age, tumour size, or histopathological findings. However, the mean relative mRNA expression in tumours with a TNM stage >3 was significantly lower compared to those with TNM stage ≤2. In conclusion, this study investigates the expression of PD-L1 mRNA and PD-L1 protein, particularly in malignant CMTs. The findings strongly support the potential for developing effective immunotherapy methods targeting the PD-1/PD-L1 pathway for advanced CMTs in the future. For further conclusive assessment, future studies should focus on refining immunotherapy strategies for CMT cases expressing PD-L1.

Porcine adenoviruses (PAdVs) are promising but still underdeveloped viral-vector platforms for swine vaccine development. Compared with human adenovirus-based vectors, PAdV vectors may offer potential advantages in host association, veterinary relevance, and mucosal delivery while avoiding direct reliance on common human adenovirus backbones. This review summarizes current knowledge on PAdV biology, vector engineering, vaccine applications, immune responses, translational challenges, and future priorities. Early studies showed that recombinant PAdV vectors can express heterologous antigens from important swine pathogens, including classical swine fever virus, pseudorabies virus, and transmissible gastroenteritis virus. The strongest direct proof-of-concept evidence comes from recombinant PAdV expressing classical swine fever virus E2/gp55, which induced neutralizing antibodies and protection in pigs. Comparative adenovirus-vectored swine vaccine studies support the broader feasibility of adenoviral antigen delivery for porcine reproductive and respiratory syndrome, porcine epidemic diarrhea, swine influenza, and African swine fever, but these data should not be interpreted as direct validation of PAdV for these diseases. Major gaps remain in anti-PAdV immunity, genetic stability, biosafety, shedding, target-animal safety, DIVA compatibility, manufacturing, and regulatory readiness. Recent advances in PAdV-5 reverse genetics provide new opportunities for modern vector design.