The peptide adjuvant, pleurocidin (PLE), and the Vibrio harveyi antigen, recombinant
glyceraldehyde-3-phosphate dehydrogenase (rGAPDH) protein, were encapsulated with poly
(lactide-co-glycolide) (PLG) polymers in our previous study to produce PLG-encapsulated PLE
plus rGAPDH microparticles (PLG-PLE/rGAPDH MPs) that sustained stable release of both PLE and
rGAPDH as well as, after two-time vaccination with MPs, generated long-term protective immunity
against V. harveyi in grouper. Stable controlled-release of PLE plus rGAPDH from PLG-PLE/rGAPDH
MPs is an attractive feature for developing an e ective single-dose vaccine. In the present study,
therefore, we aim to evaluate whether single administration with PLG-PLE/rGAPDH MPs in grouper
would result in protective immunity against V. harveyi. Peritoneal vaccination of grouper with one
dose of PLG-PLE/rGAPDH MPs raised serum titers over a long 12-week period. Moreover, twelve
weeks after vaccination, significant lymphocyte proliferation and maximum TNF- production were
found in grouper immunized with a single dose of PLG-PLE/rGAPDH MPs. More importantly,
immune responses elicited by single vaccination with PLG-PLE/rGAPDH MPs protected 80% of fish
against a lethal peritoneal challenge of the highly virulent V. harveyi (Vh MML-1). In conclusion, our
data truly reveal the feasibility of the development of a single-dose vaccine against V. harveyi based
on PLG-PLE/rGAPDH MPs.
