Bioencapsulation of transgenic Nannochloropsis sp. with Artemia as a vaccine delivery system to zebrafish as a fish model against vibriosis

Aquaculture production is a significant food source, but it has been declining due to aquatic diseases, such as vibriosis caused by Vibrio spp. For fish larvae, given their diminutive size and great susceptibility to the disease, oral vaccination was deemed superior to injection or immersion methods. Therefore, a bioencapsulation technique was utilized, where transgenic Nannochloropsis sp. expressing the OmpK gene was incorporated into live Artemia, a natural diet for fish at their early stage. This study utilized Nannochloropsis sp. transformed with a vector VCP_OMPK_ZA1 harboring OmpK gene fragment originating from Vibrio sp. which acts as an antigen. The cuticle of Artemia offers an additional layer of protection to the antigen, protecting it against degradation in the gastrointestinal tract. Transgenic Nannochloropsis sp. was incubated with Artemia for 2 hours and the presence of the transgene was validated using PCR analysis. The transgenic microalgae-incorporated Artemia was then fed to zebrafish, an excellent model for studying infection and immune responses because of its compact size, swift growth, and suitability for genetic manipulation. The objective was to investigate immune response activation via gene expression analysis, with a specific focus on assessing the IgZ, TNF-ɑ, and IL-1β genes. The levels of expression for IgZ and IL-1β were found to be elevated by factors of 0.8, 1.2, 1.9, and 2.6-fold respectively on Day 7 and Day 14, whereas TNF-ɑ significantly upregulated by 2.9-fold in zebrafish fed with the transgenic microalgae incorporated Artemia in comparison to zebrafish given with wild-type Artemia. IL- 1β (4.0-fold) gene transcripts increased significantly in groups fed with wild-type bioencapsulated Artemia after being infected with bacteria while IgZ levels did not increase significantly for both groups. The effectiveness of the transgenic microalgae was evaluated by subjecting them to a bacterial challenge of Vibrio sp. and measuring the relative percent survival (RPS). The outcomes of the bacterial challenge experiment revealed that the vaccinated groups displayed complete immunity against pathogenic Vibrio spp., with RPS of 100%, and demonstrated significantly increased survival rates when compared to those that were fed with wild-type Nannochloropsis sp. bioencapsulated Artemia (RPS = 40%). The histopathological analysis revealed that the fish that were not vaccinated had severe changes such as hemorrhages and necrosis, whereas those that were vaccinated showed only mild changes such as tubular degeneration and muscle regeneration following the bacterial challenge trial. Overall, the results obtained proved that the incorporation of transgenic microalgae harboring an antigenic peptide administered through the live feed may enhance the fish's immune system to combat vibriosis and be effectively applicable for vaccinating fishes during the early larval stage.

Text 122783.pdf Download (1MB) Official URL or Download Paper: http://ethesis.upm.edu.my/id/eprint/18662

Actions (login required)

View Item