Enhancement of Avian Influenza Virus vaccines in chickens through identification and application of novel mucosal adjuvants
The avian influenza virus (AIV) is a mucosal pathogen that is of relevance to the poultry industry and humans from economic and public health perspectives. Most commercially available AIV vaccines are of the inactivated type requiring parenteral co-administration with a water-in-oil adjuvant to generate an antigen-specific immune response. Limitations exist in the quantity and quality of antibody-mediated immune responses generated with this approach. This research was aimed at identifying novel, more efficacious adjuvants with the potential to be administered by the intramuscular and aerosol routes. To evaluate the adjuvant potential of class B oligodeoxynucleotides (ODNs) in chickens, 2 doses of CpG ODN (oligodeoxynucleotides containing unmethylated CpG motifs) 2007 (CpG 2007) and 1826 were administered intramuscularly (IM) with a formalin-inactivated, whole, H9N2 avian influenza virus. We concluded that different members of class B ODNs displayed various levels of adjuvancy when combined with inactivated AIV in chickens based on neutralizing and virus-specific antibody responses generated by the 2 doses. Therefore, CpG 2007 was selected at a specific dose for poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticle encapsulation which was administered with inactivated AIV through the IM and aerosol routes; systemic and local mucosal antibody-mediated responses were assessed. Significantly higher systemic and local mucosal antibody responses were observed after the administration of 3 doses of the nanoparticle-encapsulated CpG 2007 vaccine by the aerosol route compared to the formulation containing nonencapsulated CpG 2007. In contrast, significantly higher systemic and local mucosal antibody responses were induced with the nonencapsulated CpG 2007 formulation by IM administration. To gain a better understanding of the antibody-mediated immune responses, the inactivated AIV vaccine component was encapsulated for IM administration. The protective efficacy of the vaccine and the ability to generate IgY antibodies of high avidity were assessed. Nonencapsulated AIV with encapsulated CpG 2007 elicited significantly higher magnitude antibody mediated responses and a reduction in shedding of cloacal virus compared to the encapsulated AIV and encapsulated CpG formulation. High avidity IgY antibodies were induced by both formulations. In conclusion, the adjuvant potential of CpG 2007 and PLGA nanoparticles was demonstrated in the context of inactivated AIV using IM and aerosol routes of administration.