“Development and Evaluation of a Recombinant Protective Antigen-Based Vaccine Against Bacillus cereus Infection in Asian Sea Bass (Lates calcarifer) (6693)”

Development and Evaluation of a Recombinant Protective Antigen-Based Vaccine Against Bacillus cereus Infection in Asian Sea Bass (Lates calcarifer)

This study aimed to develop a vaccine for Asian sea bass (Lates calcarifer) infected with Bacillus cereus group (Bcg), a pathogenic bacterium known to cause severe septicemia, ultimately leading to significant economic losses in commercial aquaculture systems. The clinical signs of infected fish included multifocal petechiae on the skin, and excessive accumulation of coelomic fluid in the body cavity, all of which indicate systemic infection and potential organ dysfunction. We identified a plasmid, pBS01, in the virulent B. cereus strain, which shares notable similarities with the Bacillus anthracis virulence plasmid pXO1. Further genomic and proteomic analyses revealed the presence of a protective antigen (PA) within this strain, analogous to the protective antigen found in B. anthracis. Given the established role of the protective antigen in anthrax pathogenesis and its importance as a vaccine target, we hypothesized that the PA from B. cereus might serve as an effective immunogen for vaccine development. To investigate the potential interaction between the protective antigen and host immune receptors, we conducted molecular docking studies between PA and anthrax toxin receptor 1 (ANTXR1). The results demonstrated that domain 4 (PD4) of the protective antigen has a binding affinity to ANTXR1, suggesting that this domain may play a critical role in host-pathogen interactions. Based on these findings, we proceeded to express and purify recombinant PD4 as a subunit vaccine candidate. For the vaccination trial, Asian sea bass were immunized at two time points: an initial dose at day 0, followed by a booster at day 14. Each fish received a 50 µg dose of the recombinant PD4 protein. After the immunization period, fish were challenged with B. cereus to assess vaccine efficacy. The results indicated that the vaccinated group exhibited a relative percentage survival (RPS) of 100%, demonstrating complete protection against B. cereus infection. In contrast, the control group, which did not receive the vaccine, exhibited a cumulative mortality rate of 72.5%, confirming the high virulence of the pathogen and underscoring the vaccine’s protective potential.

1. CHEN, SHIH-CHU, NATIONAL PINGTUNG UNIVERSITY OF SCIENCE AND TECHNOLOGY, Presenter
2. CHENG, LI-WU, NATIONAL PINGTUNG UNIVERSITY OF SCIENCE AND TECHNOLOGY, Author
3. WANG, PEI-CHI, NATIONAL PINGTUNG UNIVERSITY OF SCIENCE AND TECHNOLOGY, Author