CpG oligonucleotide, host defense peptide and polyphosphazene act synergistically, inducing long-lasting, balanced immune responses in cattle

Vaccines consisting of subunit or protein antigens are less immunogenic than traditional vaccines, and therefore require formulation with an adjuvant. Conventional adjuvants, however, often cause undesirable injection site reactions and Th2-biased immune responses. Therefore, novel vaccine adjuvants which can safely enhance and selectively bias the resulting immune response are required. Here the adjuvant combination of CpG ODN, indolicidin and polyphosphazene (CpG + indol + PP) was evaluated for its ability to enhance and modulate the immune response when formulated with the antigen hen egg lysozyme (HEL). Cattle immunized with HEL co-adjuvanted with CpG + indol + PP developed higher antigen-specific humoral responses, and long-lasting cell-mediated immune responses, as evidenced by elevated levels of IFN-γ secretion by re-stimulated PBMCs, that were superior even to EMULSIGEN®, an oil-in-water based adjuvant that was used as positive control. Physical characterization of the vaccines indicated that formulation of HEL with CpG + indol + PP resulted in the formation of antigen-adjuvant complexes, which may have contributed to their enhanced immunogenicity. Furthermore, the addition of polyphosphazene to CpG ODN and indolicidin dose-dependently enhanced the secretion of the cytokines IFN-α, TNF-α and IFN-γ in vitro, indicating that polyphosphazene can also synergize with CpG ODN and indolicidin to stimulate innate immune responses.