Not AvailableDNA-based immunization has proven to be an effective prophylactic measure to control aquatic animal
diseases. In order to improve the efficiency of vaccine against fish pathogen, novel delivery mechanism
needs to be adopted. In the present study we nanoconjugated the previously constructed DNA vaccine
(pGPD + IFN) with chitosan nanoparticles (CNPs) by complex coacervation process. After construction
of the vaccine, an in vivo vaccination trial was conducted in which 2 groups of rohu (L. rohita) fingerlings
were vaccinated with CNPs-pGPD + IFN, one group by oral route (incorporated in feed for 14 days) and
the other by immersion route (primary and booster immunised), whereas, a third group was
intramuscularly (I/M) injected (initial and booster immunised) with naked pGPD + IFN and subsequently
challenged with E. tarda (8.7* 104 CFU/fish) at 35-day post initial vaccination. The protective immune
responses were determined in terms of relative percentage survival (RPS), specific antibody production,
non-specific immune response, expression kinetics of immune-related genes and pathological manifestation.
Evaluation of RPS analysis revealed that CNPs-pGPD + IFN groups recorded highest RPS (81.82% and
72.73% in oral and immersion vaccinated fish group respectively) while the naked pGPD + IFN injected
group showed 63.62% RPS when compared with 55% cumulative mortality of control group. In addition,
NBT, myeloperoxidase activity, serum lysozyme activity and specific antibody titre in case of CNPs-pGPD
+ IFN groups showed higher activities during all the time points. Furthermore, CNPs-pGPD + IFN groups
showed significant (p < 0.05) upregulation of different immune gene transcripts (IgHC, iNOS, TLR22,
NOD1 and IL-1b) in three immunologically important tissues post immunization (both primary and
booster dose) as well as after challenge. Thus, from this study, we can conclude that oral or immersion
vaccination with CNPs-pGPD + IFN can orchestrate an effective immunisation strategy in organizing a
coordinative immune response against E. tarda in L. rohita exhibiting minimum stress to the host with
maximum efficacy.Not Availabl