Fc-fusion technologies, in which
immunoglobulin Fc is genetically fused to an antigenic
protein, have been developed to confer antibody-like properties to
proteins and
peptides. Mammalian
IgG Fc fusion exhibits improved
antigen-induced immune responses by providing aggregates with high avidity for the
IgG Fc receptor and salvaging the antigenic portion from endosomal degradation. However, whether the linked chicken
IgY Fc fragment shares similar characteristics to mammalian
IgG Fc remains unclear. In this study, we linked the chicken
IgY Fc gene to the
outer membrane protein A (ompA) of Bordetella avium through overlapping PCR. The fusion gene was cloned into the pPIC9 plasmid to construct the recombinant Pichia pastoris transformant expressing the ompA-Fc fusion
protein. The effects of the linked Fc on macrophage vitality, activity, efficiency of antigen processing, and immune responses induced by the fused ompA were investigated. Furthermore, the effect of Taishan Pinus massoniana pollen
polysaccharide (TPPPS), an
immunomodulator, on chicken macrophage activation was evaluated. TPPPS was also used as an adjuvant to investigate its immunomodulatory effect on immunoresponses induced by the fused ompA-Fc in chickens. The pinocytosis, phagocytosis, secretion of
nitric oxide and TNF-α, and MHC-II molecular expression of the macrophages treated with the fused ompA-Fc were significantly higher than those of the macrophages treated with ompA alone. The addition of TPPPS to the fused ompA-Fc further enhanced macrophage functions. The fused ompA-Fc elicited higher
antigen-specific immune responses and protective efficacy compared with ompA alone. Moreover, the fused ompA-Fc conferred higher serum antibody titers, serum
IL-2 and
IL-4 concentrations, CD4+ and CD8+ T-lymphocyte counts, lymphocyte transformation rate, and protection rate compared with ompA alone. Notably, the prepared TPPPS adjuvant ompA-Fc
vaccines induced high immune responses and protection rate. The linked Fc and TPPPS adjuvant can remarkably enhance macrophage functions and specific immune responses. This study provides new perspectives to improve the immune effects of
subunit vaccines for prevention of
poultry diseases.