Pellet feed adsorbed with the recombinant Lactococcus lactis BFE920 expressing SiMA antigen induced strong recall vaccine effects against Streptococcus iniae infection in olive flounder (Paralichthys olivaceus). (August 2016)

• Record Type: Journal Article
• Authors: Kim, Daniel; Beck, Bo Ram; Lee, Sun Min; Jeon, Jongsu; Lee, Dong Wook; Lee, Jae Il; Song, Seong Kyu
• Is Part Of: Fish & shellfish immunology. Volume 55(2016:Aug.)
• Page Start: 374
• Page End: 383
• Publication Date: 2016-08
• Subjects: Olive flounder -- Lactococcus lactis BFE920 -- Feed vaccine -- Oral immunization -- Vaccine vehicle -- Streptococcus iniae -- Streptococcosis; Fishes -- Immunology -- Periodicals; Shellfish -- Immunology -- Periodicals; Poissons -- Immunologie -- Périodiques; Crustacés -- Immunologie -- Périodiques; 571.9617
• DOI: 10.1016/j.fsi.2016.06.010
• Languages: English
• ISSNs: 1050-4648

Abstract

Abstract: The aim of this study was to develop a fish feed vaccine that provides effective disease prevention and convenient application. A lactic acid bacterium (LAB), Lactococcus lactis BFE920, was modified to express the SiMA antigen, a membrane protein of Streptococcus iniae . The antigen was engineered to be expressed under the nisin promoter, which is induced by nisin produced naturally by the host LAB. Various sizes (40 ± 3.5 g, 80 ± 2.1 g, and 221 ± 2.4 g) of olive flounder ( Paralichthys olivaceus ) were vaccinated by feeding the extruded pellet feed, onto which the SiMA-expressing L. lactis BFE920 (1.0 × 10 7 CFU/g) was adsorbed. Vaccine-treated feed was administered twice a day for 1 week, and priming and boosting were performed with a 1-week interval in between. The vaccinated fish had significantly elevated levels of antigen-specific serum antibodies and T cell marker mRNAs: CD4-1, CD4-2, and CD8a. In addition, the feed vaccine significantly induced T cell effector functions, such as the production of IFN-γ and activation of the transcription factor that induces its expression, T-bet. When the flounder were challenged by intraperitoneal infection and bath immersion with S. iniae, the vaccinated fish showed 84% and 82% relative percent survival (RPS), respectively. Furthermore, similar protective effects were confirmed even 3 months after vaccination in a field study (n = 4800), indicating that this feed vaccine elicited prolonged duration of immunopotency. In addition, the vaccinated flounder gained 21% more weight and required 16% less feed to gain a unit of body weight compared to the control group. The data clearly demonstrate that the L. lactis BFE920-SiMA feed vaccine has strong protective effects, induces prolonged vaccine efficacy, and has probiotic effects. In addition, this LAB-based fish feed vaccine can be easily used to target many different pathogens of diverse fish species. Highlights: The pellet feed adsorbed rL. lactis - simA protected fish against Streptococcus iniae infection. The feed vaccine induced strong immunological recall against the pathogen. The vaccine efficacy was confirmed in a large-scale field study (n = 4800). The feed vaccine activated antigen-specific effector functions of B and T cells. This vaccine stimulated probiotic effects of metabolism besides disease protection.