Oral DNA vaccine adjuvanted with cyclic peptide nanotubes induced a virus-specific antibody response in ducklings against goose parvovirus

Background: Cyclic peptide nanotubes (cPNTs) formed from the spontaneous beta-sheet stacking of peptide rings may serve as a safe and effective oral delivery vehicle/adjuvant for DNA vaccines. Aim: In this study, we sought to determine if a DNA vaccine expressing the VP2 protein of goose parvovirus, adjuvanted with cPNTs, may elicit virus-specific antibody response through oral vaccination. Material and methods: Forty 20-day-old Muscovy ducks were randomly assigned to two groups of 20 ducks each and vaccinated. Ducks were orally vaccinated (Day 0) and boosted (Day 1 and Day 2) or were mock-vaccinated with saline as the negative control. For immunohistochemical staining, the primary antibody used comprised a rabbit anti-GPV antibody, and the secondary antibody was a goat anti-rabbit antibody. Goat-anti-mouse-IgG was used as a tertiary antibody. IgG and IgA antibody titers in serum were analyzed by the GPV virus-coated ELISA. For IgA antibody analysis, intestine lavage was harvested too. Results: A DNA vaccine, coated with cPNTs, can induce a significant antibody response in ducklings. Immunohistochemical staining of tissues from vaccinated ducklings showed that VP2 proteins can be detected in the intestines and livers for up to six weeks, confirming the antigen expression by the DNA vaccine. Antibody analysis found that this vaccine formulation was very efficient at inducing IgA antibodies in the serum and the intestinal tract. Conclusion: A DNA vaccine adjuvanted with cPNTs can effectively express the antigen and can significantly induce an antibody response against goose parvovirus through oral vaccination.