Experimental design for chicken immunization.

1Route of vaccine administration was shown as O: oral (via oral gavage), P: parenteral (intramuscularly) and X: no vaccination.2Chickens survived virus challenge were sacrificed at day 49, bursa was extracted and analyzed for the presence of virus and histological bursa lesion assessment.3Pichia: freeze-dried and inactivated intact P. pastoris cells. Resuspended in 1 ml drinking water.4Oral adjuvant is a mixture of NaF salt (100 mg/kg chicken weight) and 50 µg CpG oligodeoxynucleotide (CpG ODN).5The administered dosage was according to the manufacture's instructions (Lohmann Animal Health, Cuxhaven, Germany).