Comparison Of Different Immunization Routes Of Aeromonas Virens HisJ Gene Deletion Mutant Strain Against Crucian Carp

Aeromonas veronii(A.veronii)is a human-animal-aquatic animal pathogen that can cause acute enteritis or bacteremia in humans,while in aquaculture it can cause serious diseases such as enteritis,ulcers and bleeding to fish.A recombinantly constructed hisJ gene deletion strain of Aeromonas veronii in our laboratory,and proved through follow-up tests that its virulence was significantly reduced compared with wild strains,and a weakly virulent hisJ strain that could stabilize the inheritance was obtained.In this project,the deletion strain was prepared as an attenuated biological preparation,and then immunized by four routes:intraperitoneal injection,intramuscular injection,oral administration and immersion,to investigate the effect of different immunization routes on crucian carp.The results showed that the attenuated biological preparation at a concentration of 2×10~7 CFU/m L was safe for immunization of crucian carp by different routes.At this safe concentration,the carp were immunized by different routes could increase the phagocytes phagocytic activity in crucian carp serum to varying degrees,elevated levels of non-specific immune-related enzymes(ACP,AKP,C3,C4,LZM,SOD and Ig M)in carp serum,and increase the level of specific serum antibodies in crucian carp;The levels of IL-1β,IL-10,TNF-α,TGF-βin organs(liver,spleen,kidney,midgut and gill)of crucian carp were also increased;After challenge,the protective rate was 64%in intraperitoneal injection group,56%in intramuscular injection group,52%in oral injection group and 48%in immersion group,this indicates that different immunization routes can produce certain protective power against crucian carp after vaccination with mitigating biological agent,but the level of protection is different;By measuring the bacterial load after challenge,the anti-infection ability of crucian carp against Aeromonas veronii was enhanced after vaccination by different immune routes.In summary,the deletion strain of Aeromonas veronii hisJ gene can be used as a safe mitigating biological agent,and immunizing crucian carp by intraperitoneal injection at a concentration of 2×10~7CFU/m L can increase the immune level and phagocytic activity of crucian carp,enhance the antioxidant stress ability of crucian carp,and obtain certain disease resistance of Aeromonas veronii.It provides new ideas for the prevention and control of Aeromonas veronii in aquatic animals,the foundation was also laid for the development of a live,weakly virulent vaccine for Aeromonas veronii.