| To determine the immune modulating effects of chicken interleukin-2 (chIL-2), a cytokine 24% identical to mammalian IL-2 at the amino acid level, we undertook vaccination studies in chickens utilizing a truncated Marek's Disease virus (MDV) glycoprotein B (gp49, gB) with chIL-2 as adjuvant, administered as plasmid DNA or recombinant protein. To maintain close proximity between antigen and cytokine, the respective plasmids were co-administered by attenuated ΔactA Listeria monocytogenes (ΔactA LM), gene gun inoculation or needle injection, and recombinant gB and chIL-2 protein were co-delivered by three types of microspheres: 5 micron polystyrene latex microspheres (PLM), biodegradable polylactic acid microspheres (PLAM) and 1 micron aldehyde/sulfate polystyrene latex microspheres (A/SPLM). Chickens were immunized at 3 weeks with plasmid DNA or protein, and their immune responses to the antigen and recall responses to live virus were evaluated by ELISA and T cell proliferative assays. Results showed that ΔactA LM could serve as DNA vaccine delivery vehicle in chickens. The specific humoral responses were significantly enhanced by co-administration of chIL-2 by gene gun, intramuscular plasmid injection and all three types of microspheres. The one micron A/SPLM were the most effective vehicles in inducing T cell proliferative responses, and co-delivery of chIL-2 significantly enhanced these responses. In summary, chIL-2 was proven, for the first time, to be an effective adjuvant for antibody and T cell proliferative responses. Another important finding was that latex microspheres were an excellent vehicle for co-delivering microgram quantities of recombinant proteins with chIL-2. These microspheres should be useful for testing the adjuvanticity of other cytokines and costimulatory molecules. |
