Summary
Vaccination provides a sustainable alternative to the unsustainable use of antibiotics in aquaculture for the treatment of bacterial diseases, thereby reducing the incidence of antimicrobial resistance (AMR). Our project focuses on the development of a feed-based vaccine against infection by Vibrio spp. (MyIPO Malaysia, patent filing number: PI2021000105). This vaccine is unique in term of its cost-effectiveness, ease of administration, and environmental safety. Moreover, it reduces the reliance on trained personnel for vaccine administration and minimizes fish stress during vaccination. The oral vaccine stimulates both mucosal and systemic immune responses that prevent infections by multiple Vibrio species, resulting in an average survival of 80% to reach market weight. For optimal protection, it is recommended that this vaccine be administered orally according to the prescribed schedule.
The promising efficacy calls for commercialization efforts, including upscaling and field validation of the upscaled product on efficacy and suitability in cage cultured marine farms in low- and middle-income countries (LMICs). In collaboration with Bio-Angle Vacs Sdn. Bhd. (co-applicant industry), we plan to optimize the manufacturing process in a certified GMP facility. The upscaled vaccine will undergo field studies in farms in Malaysia and Indonesia (co-applicant LMIC, Indonesia) to validate its efficacy, elucidate vaccination mechanisms (co- applicant UK partner), and conduct a cost-benefit analysis of vaccination. These goals contribute to the development of an effective oral vaccine for marine fish, addressing the challenges that small- to medium-scale farmers in LMICs are facing when utilising injectable vaccines and eventually, reduce AMR for sustainable aquaculture production.
Project Outcomes
This project focused on developing and testing the ViVac feed-based vaccine, a novel solution to combat vibriosis in aquaculture, particularly targeting marine fish species. The vaccine was designed to be incorporated into fish feed, enabling easier administration and widespread application in aquaculture farms. Key laboratory studies demonstrated the vaccine's stability under conditions mimicking fish digestion and industrial feed production. Acid stability tests confirmed the vaccine's ability to remain effective in the highly acidic environment of the fish gut (pH 2), ensuring efficient delivery of antigens to trigger immune responses. However, heat sensitivity tests revealed that the vaccine's effectiveness declined at high temperatures, with 40 °C identified as the safe upper limit for maintaining its integrity during feed production.
Field trials conducted at a farm in Indonesia showcased the vaccine's potential under real-world aquaculture conditions. Over a 16-week trial, vaccinated fish achieved notable improvements in feed efficiency, consuming less feed compared to unvaccinated fish while maintaining comparable growth rates. Vaccinated fish also exhibited a better feed conversion ratio (FCR), an essential metric for cost-effective fish farming. Survival rates were high for all fish, but vaccinated fish demonstrated enhanced disease resilience.
Immunological assessments revealed significantly higher antibody levels (IgM titers) in vaccinated fish, peaking at four weeks after the initial vaccination. However, the immune response did not show further enhancement following a second booster dose, suggesting that adjustments to the vaccination schedule may further improve long-term immunity. Advanced genetic analyses confirmed the upregulation of critical immune-related genes, such as IL-1β, TNFα, and IgM, indicating that the vaccine stimulates both innate and adaptive immune responses.
Gut health and microbiota diversity also improved in vaccinated fish. Metagenomic analyses showed a more balanced and diverse gut microbiota in vaccinated fish, with lower levels of harmful pathogens like Vibrio vulnificus and Photobacterium damselae. Importantly, traces of the vaccine's bacterial antigen (V. harveyi strain VH1) were detected in the fish gut, demonstrating that the vaccine remains intact through digestion.
In summary, the ViVac feed-based vaccine offers promising benefits for marine aquaculture by improving feed efficiency, enhancing immune responses, reducing harmful pathogens, and promoting gut health. While these findings highlight the vaccine's potential, further refinements in the vaccination schedule and production processes are recommended to maximize its effectiveness.