Bicistronic DNA vaccine macromolecule complexed with poly lactic-co-glycolic acid-chitosan nanoparticles enhanced the mucosal immunity of Labeo rohita against Edwardsiella tarda infection.

DNA vaccine is an important tool to elicit both humoral and cellular immunity. Present study investigates mucosal immune response of Labeo rohita (15 ± 04 g) to plasmid DNA (pDNA) vaccine macromolecule complexed with nanoparticles (NPs). Poly lactic-co-glycolic acid (PLGA), Chitosan (Chit) and PLGA-Chit-NPs were synthesized by double emulsion solvent evaporation method. Synthesized NPs were complexed with pDNA (pGPD + IFN) vaccine construct. Size and zeta potential of PLGA-NPs, Chit-NPs and PLGA-Chit-NPs-pDNA complex were recorded to be 120 nm and +0.5 mV, 117 nm and +32 mV, 189 nm and +11 mV, respectively. Immunization by immersion was carried out in two groups receiving PLGA-Chit-NPs-pDNA (T1) and PLGA-NPs-pDNA (T2) respectively. After immersion, samples were collected on 0, 2, 4, 7, 15 and 30 days from mucosa-associated lymphoid tissues (MALT) for mRNA expression studies of IgM, IgD and IgZ using qRT-PCR. Significant up-regulation of the mRNA expression of IgM, IgD, and IgT were observed in MALT in immunized fish compared to control. After 30 days post-immunization fish were infected with a virulent strain of Edwardsiella tarda. The highest relative percentage survival was observed in T1 (64.7%) compared to T2. The study showed better efficiency of pDNA-PLGA-Chit-NPs compared to pDNA-PLGA-NPs for inducing adaptive mucosal immunity in fish.