A Novel Composite Vaccine Combining Inactivated Antigen and IgY Elicits Sustained Humoral Immunity Against FAdV-4...

Vaccination remains the primary strategy for controlling infectious diseases in farm animals. However, current conventional vaccines demonstrate clinical limitations including suboptimal immunogenicity and frequent booster requirements, which compromise disease management efficacy. This study presents an innovative vaccine platform combining yolk immunoglobulin (IgY) with inactivated antigens as co-immunization components. We developed two formulations targeting economically significant pathogens: avian Fowl Adenovirus Serotype 4 (FAdV-4) and Porcine Epidemic Diarrhea Virus (PEDV). For FAdV-4 vaccine evaluation in specific pathogen-free (SPF) chickens, the IgY-antigen complex demonstrated superior immunogenic properties compared to conventional inactivated vaccines. When administered as a single dose at 14 days of age, the experimental formulation elicited significantly stronger humoral responses as measured by both serum neutralization (SN₅₀) and ELISA. Notably, this vaccination strategy provided 100% protection against lethal FAdV-4 challenge from 0 h to 20 weeks post-vaccination, with complete absence of clinical disease manifestations. In PEDV assessment using mouse models, the IgY-antigen formulation induced significantly higher antibody titers than inactivated antigen alone at all post-immunization timepoints (p < 0.01). Comparative analysis revealed our dual-component platform enhanced both the intensity and rapidity of protective immune responses compared to traditional inactivated vaccines. These findings establish that the IgY-antigen co-immunization strategy represents a promising approach for developing new veterinary vaccines with improved protective efficacy. The platform's ability to generate robust, rapid-onset immunity while maintaining single-dose effectiveness addresses critical limitations of current vaccine technologies.