Introduction:
In the realm of aquaculture, bacterial infections pose a significant challenge, leading to substantial economic losses globally. Among these infections, those caused by Aeromonas species, such as tail and fin rot, hemorrhagic septicemia, and epizootic ulcerative syndrome (EUS), account for a substantial portion of fish infections. Aeromonas hydrophila, a Gram-negative bacterium, has been identified as a major culprit in fish infections and has also been implicated in human infections through contaminated food consumption.
Traditionally, antibiotics have been a key treatment option for Aeromonas infections in fish. However, the rising concern of antibiotic resistance has shifted the focus towards alternative strategies, with vaccines emerging as a promising solution due to their efficacy and environmentally friendly nature. Subunit vaccines, particularly those targeting surface proteins of A. hydrophila, have shown potential in inducing specific immune responses in host fish. Notably, the bacterial adhesin Aha1 has demonstrated strong immunogenicity and the ability to trigger both humoral and cellular immune responses in hosts, making it a promising candidate for vaccine development.
Methods:
In this study, recombinant vectors carrying the gene encoding the 49 kDa Aha1 protein from A. hydrophila were constructed and introduced into the probiotic strain Lactobacillus casei CC16 to generate two types of recombinants: L. casei-pPG1-Aha1 (Lc-pPG1-Aha1) and L. casei-pPG2-Aha1 (Lc-pPG2-Aha1). These recombinant strains were orally administered to common carps to assess their immunogenicity. The expression and localization of the Aha1 protein in relation to L. casei were validated using Western blotting, flow cytometry, and immunofluorescence techniques.
Results:
The recombinant vaccines showed high efficacy in stimulating antibody production and key immune parameters in the serum of hosts. Furthermore, significant upregulation of immune-related gene expressions in various tissues, including cytokines IL-10, IL-1β, TNF-α, and IFN-γ, indicated a robust immune response post-immunization. Enhanced phagocytosis responses and increased survival rates following re-infection with virulent A. hydrophila highlighted the protective potential of the recombinant L. casei strains. Moreover, the survivability of the recombinant L. casei in the intestines of immunized fish further underscored their potential as oral vaccines against A. hydrophila infections in common carps.
Conclusion:
The findings of this study demonstrate the promising immunogenicity and protective efficacy of recombinant Lactobacillus casei expressing Aha1 against A. hydrophila infections in common carps. By leveraging the probiotic characteristics of L. casei as a safe and effective oral vaccine carrier, this research opens up new avenues for combating bacterial infections in aquaculture. The development of oral vaccines using recombinant probiotics represents a novel and innovative approach towards enhancing immunity and disease resistance in fish populations.
Key Takeaways:
– Recombinant L. casei expressing Aha1 from A. hydrophila shows high efficacy in stimulating immune responses in common carps.
– Oral vaccination with recombinant L. casei leads to increased antibody levels and immune-related gene expressions in host fish.
– The recombinant L. casei strains enhance phagocytosis responses and improve survival rates against virulent A. hydrophila infections.
– The survivability of recombinant L. casei in the fish intestines highlights their potential as long-lasting oral vaccines for aquaculture.
– This study paves the way for utilizing probiotic-based oral vaccines as a sustainable and eco-friendly solution to combat fish infections.
Tags: downstream, upstream, probiotics, secretion
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