The adjuvant effects of chicken IL-2, IL-18, IFN-γ and CpG DNA on HA DNA vaccines against H5 sub-type of avian influenza virus delivered by attenuated Salmonella
Objective To evaluate the adjuvant effects of chicken IL-2, IL-18, IFN-γand specific CpG DNA on HA DNA vaccines against H5 subtype of avian influenza virus delivered by attenuated Salmonella. Meth- ods The recombinant expression plasmids and pVAX1 were transformed by electroporation into an attenuated Sal- monella typhimurium strain SL7207, and the recombinant bacteria were screened and designated as SL7207 (pVAX1-HA-IL2), SL7207 (pVAX1-HA-IL18), SL7207 (pVAX1-HA-IFN-γ), SL7207 (pVAX1-HA-CpG), SL7207 (pVAX1-HA) and SL7207 (pVAX1) respectively. One-day-old commercial ISA brown chickens were im- munized orally and intranasally twice with the different recombinant Salmonella at dosage of 5×10~9 CFU at a two- week interval. Results The significant increased of IgA titers were found in immunized groups of SL7207 (pVAX1-HA-CpG), SL7207 (pVAX1-HA-IFN-γ) and SL7207 (pVAX1-HA)+SL7207 (pVAX1-IFN-γ) group. The titers of serum specific antibodies in positive control group were significantly higher than those of other groups three weeks at second PI (P0.05). After intranasally and orally challenged with virulent strain of H5 subtype of avain influenza virus, the protective index of SL7207 (pVAX1-HA-CpG), SL7207 (pVAX1-HA-IFN-γ) and posi- tive control groups were significantly higher than those of negative control groups (P0.01). Conclusion The adjuvant effects of CpG DNA are better than those of chicken IFN-γ, IL-18, IL-2 was not effective.