Immunoadjuvant activities of E. coli- and plasmid-expressed recombinant chicken IFN-α/β, IFN-γ and IL-1β in 1-day- and 3-week-old chickens

In the present study we assessed the capacity of recombinant E. coli- or plasmid-expressed chicken interferons (IFN) and chicken IL-1β, to exert immunostimulatory activities for humoral immune responses, in day-old and adult chickens. We observed that both recombinant E. coli-expressed chicken IFN-α/β and IFN-γ facilitated the induction of a primary and also a secondary antibody response, using tetanus toxoid (TT) as a bacterial model antigen, in immunologically mature 3-week-old chickens. In contrast, no improvement of antibody responses were noted when either type of chicken IFN was co-injected with inactivated Infectious Bursal Disease Virus (IBDV) antigen. TT-specific antibody formation was marginally increased by co-injection of recombinant E. coli-expressed chicken IL-1β. Combined administration of IFN-α/β plus IFN-γ or IL-β increased responses to TT in an additive, but not synergistic fashion. Remarkably, no augmentation of antibody responses specific for TT, nor IBDV, was noted in day-old birds, receiving IFN-α/β or IFN-γ as adjuvant. Also, intramuscular immunization of 3-week-old birds, using plasmids encoding IFN-α/β together with TT protein antigen, significantly increased the speed and magnitude of TT-specific antibody responses. Plasmids encoding chicken IL-β or IFN-γ had a minimal or inhibitory effect, respectively. These data indicate a potential for chicken cytokines as immunoadjuvant for particular types of chicken vaccine antigens.