Oral Vaccination of Largemouth Bass (Micropterus salmoides) against Largemouth Bass Ranavirus (LMBV) Using Yeast Surface Display Technology

Abstract

Largemouth bass ranavirus (LMBV) infects largemouth bass, leading to significant mortality and economic losses. There are no safe and effective drugs against this disease. Oral vaccines that directly target the intestinal mucosal immune system play an important role in resisting pathogens. Herein, the B subunit of Escherichia coli heat-labile enterotoxin (LTB, a mucosal immune adjuvant) and the LMBV main capsid protein (MCP) were expressed using Saccharomyces cerevisiae surface display technology. The yeast-prepared oral vaccines were named EBY100-OMCP and EBY100-LTB-OMCP. The candidate vaccines could resist the acidic intestinal environment. After 7 days of continuous oral immunization, indicators of innate and adaptive immunity were measured on days 1, 7, 14, 21, 28, 35, and 42. High activities of immune enzymes (T-SOD, AKP, ACP, and LZM) in serum and intestinal mucus were detected. IgM in the head kidney was significantly upregulated (EBY100-OMCP group: 3.8-fold; BY100-LTB-OMCP group: 4.3-fold). IgT was upregulated in the intestines (EBY100-OMCP group: 5.6-fold; EBY100-LTB-OMCP group: 6.7-fold). Serum neutralizing antibody titers of the two groups reached 1:85. Oral vaccination protected against LMBV infection. The relative percent survival was 52.1% (EBY100-OMCP) and 66.7% (EBY100-LTB-OMCP). Thus, EBY100-OMCP and EBY100-LTB-OMCP are promising and effective candidate vaccines against LMBV infection.

Isolation, identification, and monoclonal antibody development of largemouth bass virus

“…While several vaccines and herbal extracts have shown efficacy in preventing LMBV infection, there are currently no approved vaccines or drugs available for its prevention or treatment (Yao et al, 2022;Cheng et al, 2023;Wang et al, 2023;Zhang, M. et al, 2023). Moreover, infected fish with LMBV experience rapid mortality once symptoms appear…”

“…Vaccination is considered an ideal approach for preventing LMBV infection. Although some candidate vaccines and herbal extracts have been proven to be potent for defending against LMBV infection under laboratory conditions, there is no licensed vaccine or antiviral drug available for preventing or treating LMBV infection (Jia et al, 2022;Yao et al, 2022;Cheng et al, 2023;Wang et al, 2023;Zhang, M. et al, 2023). Therefore, rapid detection and early diagnosis of LMBV remain crucial strategies to prevent the disease's spread and mitigate economic loss.…”

“…The selection of targets and the production of antibodies are two crucial aspects in the development of immunoassay strips as they directly influence their specificity and sensitivity (Li et al, 2021;Shen et al, 2021). The MCP, which is the most abundant structural protein carrying virus-specific antigens, has emerged as an ideal target for genetic relationship identification, vaccine research, antibody production, development of detection methods, and systematic survey (Montelongo-Alfaro et al, 2019;Guo et al, 2022;Jia et al, 2022;Yao et al, 2022;Qin et al, 2023;Zhang, M. et al, 2023). Thus, we developed the monoclonal antibodies against MCP and assessed their specificity, providing valuable material for the development of immunoassay strips for LMBV detection.…”

β-Sitosterol Reduces the Content of Triglyceride and Cholesterol in a High-Fat Diet-Induced Non-Alcoholic Fatty Liver Disease Zebrafish (Danio rerio) Model

“…After euthanizing zebrafish with MS-222, the liver tissue of zebrafish was extracted and subsequently diluted with sterile phosphate-buffered saline to obtain a tissue homogenate concentration of 1%. The resultant mixture was subjected to centrifugation at 5000× g at 4 • C for 20 min, yielding a supernatant that was utilized for subsequent analysis [38]. Protein concentrations in the tissue homogenate were measured using a bicinchoninic acid (BCA) kit (Biyuntian, Shanghai, China).…”