Development of Innovative Oral Transethosome Vaccine for Effective Prevention of Francisellosis in Tilapia (Oreochromis sp.)

Summary 

The research focuses on developing an innovative oral transethosome vaccine to prevent Francisellosis, a bacterial disease caused by Francisella orientalis, in Tilapia (Oreochromis sp.). Francisellosis poses a significant threat to the aquaculture industry, leading to high mortality rates and severe economic losses. Outbreaks of this pathogen can decimate Tilapia populations, causing substantial financial damage to fish farmers due to the loss of stock and the costs associated with managing and containing the disease. The transethosome vaccine delivery system enhances the stability and bioavailability of the vaccine when administered orally, ensuring an effective immune response. By reducing the reliance on antibiotics, this vaccine addresses the growing concern of antimicrobial resistance (AMR) in aquaculture. Overuse of antibiotics in fish farming contributes to the emergence of resistant bacteria, posing risks to both aquatic life and human health. The study involves optimizing the vaccine formulation, conducting laboratory trial to assess its efficacy and safety, and providing recommendations for its implementation in aquaculture practices. With the advancement of oral vaccine delivery technology, the expected outcomes include reduced disease incidence, ensured vaccine safety, and seamless integration into standard practices. This vaccine can enhance the sustainability and resilience of Tilapia farming by decreasing antibiotic use, mitigating risks associated with antimicrobial resistance (AMR), and reducing economic losses due to disease outbreaks. Consequently, it can support global food security.

Project Outcomes

Emerging infectious diseases caused by Francisella orientalis (Fo) pose significant challenges to aquaculture. This study aimed to develop and evaluate a novel transethosome-based nanovaccine (T-FoBCFSVac) formulated with bacteriocin cell-free supernatant (BCFS) derived from F. orientalis. The characteristics of T-FoBCFSVac, including size, zeta potential and morphology, were analyzed using dynamic light scattering (DLS) and transmission electron microscope (TEM). The vaccine was then assessed for safety, protection and immune responses in tilapia vaccinated for 7 and 14 days, with sampling at week 8 post-vaccination following disease resistance analysis against F. orientalis. The T-FoBCFSVac vaccine exhibited uniform particle sizes (~100 nm) with a narrow polydispersity index (~0.24) and stable negative zeta potential (−55 to −58 mV). The optimized formulation preserved the structural integrity of bacteriocin and antigen components through mild ultrasonication processing. Immunological analyses revealed significantly elevated IgM titers, enhanced serum lysozyme activity, and upregulated immunoglobulin-related genes, including IgM. IgT and IgD and intestinal mucosal responses. Pathway enrichment analysis demonstrated progressive activation of innate and adaptive immune pathways, notably phagosome, cell adhesion molecules, cytokine–cytokine receptor interaction, ubiquitin-mediated proteolysis, RIG-l-like receptor signaling pathway, and intestinal immune network for Ig production. Protective efficacy studies showed significantly lower bacterial loads, improved survival rates (60–67.5%), and high relative percent survival (51.25–60.32%) in T-FoBCFSVac-treated fish compared to the controls. Importantly, no significant changes in blood biochemistry or tissue pathology were observed, which confirmed the nanovaccine’s safety and biocompatibility. These findings suggest that T-FoBCFSVac offers a robust and safe prophylactic strategy against F. orientalis, with potential applications for disease management in aquaculture. 

Keywords: Transethosome-based nanovaccine, bacteriocin cell-free supernatant, Francisella orientalis, immunomodulation, intestinal mucosal immunity, oral vaccine, red tilapia.