Oral vaccination with recombinant Lactobacillus casei with surface displayed OmpK fused to CTB as an adjuvant against Vibrio mimicus infection in Carassius auratus

• Published in: Fish & shellfish immunology 2023-04, Vol.135, p.108659-108659, Article 108659
• Main Authors: Li, Hong-Jin, Yang, Bin-Tong, Sun, Yu-Feng, Zhao, Tong, Hao, Zhi-Peng, Gu, Wei, Sun, Meng-Xia, Cong, Wei, Kang, Yuan-Huan
• Format: Article
• Language: English
• Subjects: Adjuvants, Immunologic; Animals; Cholera toxin B subunit; Goldfish; Humans; Immune protection; Lacticaseibacillus casei - genetics; Lactobacillus casei; Outer membrane protein K; Recombinant Proteins; Vaccination; Vibrio mimicus
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2023.108659

Vibrio mimicus (V. mimicus) is a pathogenic bacterium that causes diseases in humans and various aquatic animals. A particularly efficient way to provide protection against V. mimicus is through vaccination. However, there are few commercial vaccines against V. mimics, especially oral vaccines. In our study, two surface-display recombinant Lactobacillus casei (L. casei) Lc-pPG-OmpK and Lc-pPG-OmpK-CTB were constructed using L. casei ATCC393 as an antigen delivery vector, outer membrane protein K (OmpK) of V. mimicus as an antigen, and cholera toxin B subunit (CTB) as a molecular adjuvant; furthermore, the immunological effects of recombinant L.casei in Carassius auratus (C. auratus) were assessed. The results indicated that oral recombinant L.casei Lc-pPG-OmpK and Lc-pPG-OmpK-CTB stimulated higher levels of serum-specific immunoglobulin M (IgM) and increased the activity of acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD), lysozyme (LYS), lectin, C3, and C4 in C. auratus, compared with control groups (Lc-pPG group and PBS group). Furthermore, the expression of interleukin-1β (IL-1β), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β) in the liver, spleen, head kidney, hind intestine and gills of C. auratus was significantly increased, compared with that in the controls. These results demonstrated that the two recombinant L. casei strains could effectively trigger humoral and cellular immunity in C. auratus. In addition, two recombinant L.casei strains were able to survive and colonize the intestine of C. auratus. Importantly, after being challenged with V. mimicus, C. auratus fed Lc-pPG-OmpK and Lc-pPG-OmpK-CTB exhibited greater survival rates than the controls (52.08% and 58.33%, respectively). The data showed that recombinant L. casei could elicit a protective immunological response in C. auratus. The effect of the Lc-pPG-OmpK-CTB group was better than that of the Lc-pPG-OmpK group, and Lc-pPG-OmpK-CTB was found to be an effective candidate for oral vaccination. •Two surface-displayed recombinant L. casei strains expressing OmpK and OmpK-CTB were successfully constructed.•Oral administration of L. casei to C. auratus can enhance its humoral and cellular immunity.•Recombinant L.casei can colonize the intestine and protect C. auratus from V. mimicus infection.•Recombinant L. casei fused with molecular adjuvant CTB showed better immune effects in C. auratus than recombinant L. case