Chitosan-tripolyphosphate nanoparticles as a novel vehicle for DNA vaccine delivery: combatting Aeromonas hydrophila in zebrafish

Abstract

Over the past few decades, aquaculture has been steering the giant wheel of the world’s food production system. A number of significant diseases, such as dropsy, swelling of tissues, and haemorrhagic septicemia, are triggered by various bacterial species. In this study, we aimed to develop and achieve oral delivery of pVAX-Aly (Aerolysin) DNA vaccines in biodegradable nanoparticles using a zebrafish (Danio rerio) model to enhance defence against Aeromonas hydrophila infection. We utilized the pathogenic gene Aerolysin (Aly), which is linked to the virulence of A. hydrophila, to construct a DNA vaccine using the pVAX1 vector, designated as the pVAX-Aly DNA vaccine. Additionally, chitosan-tripolyphosphate nanoparticles (Cs/TPP-NPs) were formulated, functional groups were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, morphology was determined by Field Emission Scanning Electron Microscopy (FE-SEM) (50.6 nm ± 52.8 nm), and transmission electron microscopy (TEM) imaging showed dimensions of ~ 0.5 to 1 µm. The Cs/TPP-NPs were utilized to encapsulate the pVAX-Aly DNA vaccine. The effectiveness of encapsulation of Cs/TPP-NPs was determined to be 78.5%. The lyophilized pVAX-Aly DNA-Cs/TPP complex preparations were fed to the fish, and the tissue distribution of pVAX-Aly was studied by polymerase chain reaction (PCR). Histopathological examination suggested no cell lesions and no negative impact on the vaccinated fish. Furthermore, quantitative real-time PCR (qRT-PCR) was assessed, and the immune-related genes transferrin, lysozyme, tumor necrosis factor-alpha (TNF-α), and heat shock protein 70 (HSP70) also exhibited significantly higher expression after immunization. Additionally, the exposure of different concentrations of Cs/TPP-NPs to Danio rerio fibroblast (DrF) cell lines revealed no significant morphological abnormalities. The findings from this study demonstrated that the Cs/TPP-NPs encapsulated DNA vaccine administered through feed could improve disease resistance to A. hydrophila infection via upregulation of the immune-related gene (transferrin, lysozyme, TNF-α, and HSP70), good tissue distribution, maintenance of histological integrity, and enhancement of leukocyte population in Danio rerio.