Incorporation of transgenic Nannochloropis sp. into fish feed as vaccine delivery system against vibriosis

Oral vaccination is one of the potential methods for preventing disease outbreaks, and this method is easier and causes less stress to the fish. However, there is a limitation for oral vaccination which the antigens were easily degraded due to the high acidity of the fish gut. To overcome this limitation, microalgae were used as a vaccine delivery system which it could provide antigen protection from being degraded. Thus, this study aims to evaluate the efficacy of oral vaccines on zebrafish, used as a host model against vibriosis, by incorporating transgenic Nannochloropsis sp. into fish feed. In this research, Nannochloropsis sp. was transformed with a designated vector (VCP_OmpK_ZA1) harbouring OmpK gene fragment, a gene coding for antigenic property protein from Vibrio harveyi. 10% of the verified transgenic Nannochloropsis sp. were mixed with commercial fish feed (TL+CP). Adult zebrafish were fed with the formulated fish feed for 5 consecutive days in week 1, and the booster given in week 3. For the control groups, zebrafish were fed with 10% wild-type Nannochloropsis sp.- formulated feed (WT+CP) and commercial feed (CP). The feeding trials were performed until week 6. The zebrafish then were evaluated through weekly analysis expression of genes via RT-qPCR, and the relative percentage of survival (RPS) and histopathology was analyzed upon bacterial challenge with V. harveyi in week 6. Based on the result obtained, the IgZ gene was significantly upregulated by 4-fold after 8 days post-first dose of vaccination while TNFα and IL-1β genes were slightly upregulated after 1 day post-second dose of vaccination by 1.4-fold and 1.6-fold respectively. The RPS of the vaccinated fish (TL+CP) and unvaccinated fish (CP+WT) were 83% and 42%, respectively. For the histopathology analysis, the unvaccinated fish (CP and CP+WT) had severe histopathological changes and vaccinated fish (CP+TL) showed minor histopathological changes. This study has demonstrated that the transgenic microalgae-formulated feed has the potential to stimulate the immune response of the fish.

Text 122780.pdf Download (949kB) Official URL or Download Paper: http://ethesis.upm.edu.my/id/eprint/18661

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