Background/Objectives: Porcine Circovirus 2 (PCV2) infection poses significant health and economic challenges to the global swine industry. The disease in pigs leads to lymphoid depletion, resulting in immunosuppression and increased susceptibility to co-infections with other bacterial and viral pathogens. This study evaluated the efficacy of two novel recombinant Newcastle disease virus (NDV) strain R2B vectored vaccines that express the cap gene of PCV2 alone and along with the transmembrane and cytoplasmic tail (TMCT) domains of the NDV F gene. The efficacy of the vaccine candidates was studied in mouse and pig models. Methods: Six-week-old BALB/c mice were divided into five groups and immunized intramuscularly three times at 14-day intervals with various vaccine candidates, namely rNDV-R2B-PCVcap-TMCT, rNDV-R2B-PCVcap, and CircoFLEX commercial vaccine, along with controls. Following immunization and PCV2d virus challenge, multiple assays assessed the immune responses in animal trials. In the pig animal trial, pigs were divided into four groups: a control group (PBS), NDV-vectored PCVcap-TMCT group, NDV-vectored-PCVcap group, and CircoFLEX vaccine group. Pigs were immunized intramuscularly twice at 28-day intervals. Blood samples were collected at regular intervals over 70 days to evaluate the humoral and cell-mediated immune responses. Results: Both mice and pigs’ trials indicated that the NDV-vectored PCV2 cap-TMCT vaccine candidate elicited superior immune responses. In mice, the rNDV-R2B-PCVcap-TMCT group showed enhanced humoral and cellular immunity, increased PCV2-specific antibody levels, higher CD4+/CD8+ ratio, elevated IFN-γ and TNF-α levels, decreased IL-10 levels, reduced viral loads, and minimal histopathological changes. In pigs, the NDV-vectored PCVcap-TMCT group demonstrated better antibody responses, cytokine profiles (IFN-γ and IL-10), and higher levels of PCV2-specific neutralizing antibodies against the PCV2a, PCV2b and PCV2d genotypes when compared to other groups. Conclusions: These findings suggest NDV-vectored PCVcap-TMCT vaccine candidate, expressing the cap gene of PCV2 along with the TMCT domain, offers a promising alternative for protecting against PCV2 infection, potentially addressing the challenges posed by emerging PCV2 strains in the swine industry.

Background: Classical swine fever, a highly endemic pig disease in India, particularly in the NER, spots Assam with the highest outbreaks. Despite available CSF vaccines, concern prevails over protective immune response of C-strain vaccine, as emerging genotype 2 replaces genotype 1 globally, causing outbreak in immunized herds. Methods: The study assessed the cross-protective and cross-neutralization potency of existing vaccines against additional prevalent genotypes. Archived CSFV samples were reconfirmed by S-ELISA and nRT-PCR. Following E2 full-length genome sequencing and phylogeny (MEGA-X), representative CSFV samples from NER were isolated in PK-15 cell line. Hyper-immune serum was raised to test neutralization and cross–neutralization efficacy. Result: Of 77 archived samples, 43 were S-ELISA positive and 47 nRT-PCR. Phylogenetic analysis revealed either 1.1 or 2.2 sub-genotypes. Virus titre was 4.49-5.16 log TCID50 per ml in four samples representing two sub-genotypes (1.1 and 2.2) after 5 passages in PK-15 cells. Neutralization assay showed complete neutralization for sub-genotype 1.1, sub-genotype 2.2 showed 84% with C-strain specific antibody. The study revealed prevalence of both sub-genotypes 1.1 and 2.2 in NER with lower neutralization efficacy of vaccine strain antibodies to heterologous genotypes with conserved immunogenic epitope.

Duck viral enteritis (DVE) causes significant economic losses to duck industries in endemic regions, and existing control measures, including embryonated-egg-based vaccines, are limited by batch variability and restricted scalability. In this context, the present study reports the development of a cell culture-based live attenuated duck enteritis virus (DEV) vaccine and its evaluation under both experimental and field conditions. The Holland strain of DEV was adapted to chicken embryo fibroblast (CEF) cells and cultured through 60 serial passages, achieving a titer of 10⁶^.⁸⁸ 50% tissue culture-infective dose (TCID₅₀)/mL. Evaluation in seronegative ducklings demonstrated the safety and immunogenicity of the vaccine, with no adverse clinical signs. Field evaluation in 9,000 ducklings across diverse farming systems showed consistent humoral immune responses under varying conditions. The vaccine's efficacy was further assessed under controlled-challenge conditions, where it conferred complete protection against a virulent field isolate of DEV (DP/As/Km/19). Overall, the findings indicate that the CEF-adapted live attenuated vaccine is safe, highly immunogenic, and suitable for large-scale production, highlighting its potential as a practical and scalable strategy for controlling DVE in endemic regions.