Expression of LamB Vaccine Antigen inWolffia globosa(Duck Weed) Against Fish Vibriosis

Vibriosis is a commonly found bacterial disease identified among fish and shellfish cultured in saline waters. A multitude ofVibriospecies have been identified as the causative agents. LamB, a member of outer membrane protein (OMPs) family of these bacteria is conserved among allVibriospecies and has been identified as an efficient vaccine candidate against vibriosis. Rootless duckweed (Wolffia) is a tiny, edible aquatic plant possessing characteristics suitable for the utilization as a bioreactor. Thus, we attempted to express a protective edible vaccine antigen against fish vibriosis in nuclear-transformedWolffia. We amplifiedLamBgene from virulentVibrio alginolyticusand it was modified to maximize the protein expression level and translocate the protein to the endoplasmic reticulum (ER) in plants. It was cloned into binary vector pMYC under the control of CaMV 35S promoter and introduced intoWolffia globosabyAgrobacterium-mediated transformation. Integration and expression of theLamBgene was confirmed by genomic PCR and RT-PCR. Western blot analysis revealed accumulation of the LamB protein in 8 transgenic lines. The cross-protective property of transgenicWolffiawas evaluated by orally vaccinating zebrafish through feeding fresh transgenicWolffiaand subsequently challenging with virulentV. alginolyticus. High relative percent survival (RPS) of the vaccinated fish (63.3%) confirmed that fish immunized with transgenicWolffiawere well-protected fromVibrioinfection. These findings suggest thatWolffiaexpressed LamB could serve as an edible plant-based candidate vaccine model for fish vibriosis and feasibility of utilizingWolffiaas bioreactor to produce edible vaccines.