Evaluation of the Multivalent Immunoprotective Effects of Protein, DNA, and IgY Vaccines Against Vibrio fluvialis Outer Membrane Protein VF14355 in Carassius auratus

Vaccination is widely recognized as an effective strategy for preventing various bacterial and viral diseases. In this study, protein, DNA, and egg yolk antibody (IgY) vaccines targeting the outer membrane protein VF14355 of <i>Vibrio fluvialis</i> (<i>V. fluvialis</i>) were administered to goldfish (<i>Carassius auratus</i>, <i>C. auratus</i>) subsequently challenged with <i>V. fluvialis</i> and <i>Aeromonas hydrophila</i> (<i>A. hydrophila</i>). The immune efficacy of the three VF14355 vaccines was evaluated through their immune activities, protective rates, anti-inflammatory and antioxidant effects, histopathology, and immunofluorescence, and the results indicated that the protective rates in the three immunized groups were significantly higher than those in the control group; furthermore, the number of kidney bacteria was significantly reduced in the immunized group compared to the control group. The ELISA results demonstrated an in vitro interaction between the bacteria and <i>C. auratus</i> serum. The plasma phagocytosis index and phagocytosis percentage were significantly increased in <i>C. auratus</i>, and their serum immune factor levels, including those of acid phosphatase (ACP), alkaline phosphatase (AKP), and lysozyme (LZM), were increased, while those of serum antioxidant factors, such as superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA), were reduced in the immunized group; notably, the expression levels of inflammatory factors were also diminished in the immunized groups. Histopathological analyses further revealed that the organ structures of the immunized group remained intact, and immunofluorescence tests indicated significant reductions in apoptosis factor p53 and DNA damage factor γH2A.X in kidney tissues. Therefore, the protein, DNA, and IgY vaccines of VF14355 demonstrate the potential to confer resistance against various bacterial infections, positioning them as promising multivalent vaccine candidates for aquaculture.