Bioencapsulation of Transgenic Nannochloropsis sp. Using Artemia as a Vaccine Delivery System to Zebrafish as a Fish Model Against Vibriosis

Abstract

Aquaculture faces decline due to diseases like vibriosis from Vibrio spp. This study aimed to examined the effect of transgenic microalgae Nannochloropsis sp. expressing the antigen OmpK gene originated from Vibrio harveyi and bioencapsulated with Artemia offers any potential as an oral vaccine in zebrafish. Nannochloropsis sp. was transformed using VCP_OMPK_ZA1 vector and successful transformant was incubated with Artemia prior fed to zebrafish. Zebrafish RNA was extracted to investigate immune response activation via gene expression analysis specifically the IgZ, TNF-ɑ, and IL-1β genes. Vaacinated and Unvaccinated fish were then challenged with pathogenic strain to test the efficacy of the oral vaccine. Results showed IgZ and IL-1β expressions increased on Days 7 and 14, while TNF-ɑ upregulated significantly in transgenic-fed zebrafish compared to wild-type. Upon bacterial challenge, transgenic-fed fish exhibited 100% relative percentage survival (RPS) compared to wild-type-fed (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. Results indicate transgenic microalgae enhance larval fish immunity against vibriosis, potentially serving as an effective vaccination method.