| In recent years,there has been a significant increase in reports of aquatic animal infections by Aeromonas caviae,posing a serious threat to aquaculture.Since the treatment of diseases caused by this bacterium is still at the stage of using chemical drugs,and the widespread use of different antibiotics has led to serious resistance of pathogenic bacteria,which leads to food safety problems.The use of vaccines is not only effective in preventing diseases,but also in alleviating these problems.When adjuvants are used in combination with inactivated vaccines,the vaccine is twice as effective and provides better protection against pathogenic bacteria.In this study,the identified Aeromonas caviae AC-CY strain was made into an inactivated vaccine,and aluminum adjuvant,glucan,APSs and propolis were selected as vaccine adjuvants to be used with the inactivated vaccine to immunize carp.The inactivated vaccine adjuvants of Aeromonas caviae were selected based on the source,cost,method of use and safety of the adjuvants,and were more suitable for mass production.In this study,we investigated the effects of combining four different immune adjuvants with inactivated vaccine on the immune indexes such as serum biochemical indexes,serum antibody potency,leukocyte phagocytic activity and tissue immunity-related cytokine expression of crucian carp.The adjuvant with inactivated vaccines made according to the proportion of 1:1 mixed adjuvants inactivated vaccines,and establish the blank control group and experimental group without adjuvant inactivated vaccines.The adjuvant vaccine was administered intraperitoneally on the 1st and 14 th day of feeding,and blood and tissue organs were collected from different carp randomly selected every 7 days for Immune-related index testing.The experimental results showed that the expression of ACP,AKP,C3,C4,CAT,Ig M,LZM and SOD in the serum of each immunized group of crucian carp was significantly higher(p<0.01)compared with the control group,and the expression of serum biochemical indexes in aluminum adjuvant group,glucan group,APSs group and propolis group were significantly higher than those in vaccine group(p<0.05).The leukocyte phagocytosis assay further verified that all experimental groups could enhance leukocyte phagocytic activity;in the serum antibody potency,the serum antibody potency results of each immunization group were higher than the control group,and the adjuvant group results were higher than the vaccine group;the relative expressions of IL-10,IL-1β,IFN-γ and TNF-α genes in liver,spleen,kidney and intestinal tissues were detected,which confirmed that the addition of adjuvant could promote the inflammatory response of the organism.In the immunoprotection experiment,all crucian carp in the control group died 7 d after the attack,the survival rate of crucian carp in the APSs group was 84%,the survival rate of crucian carp in the glucan,propolis and aluminum adjuvant groups were 72%,80% and 68%,respectively,and the survival rate of crucian carp in the vaccine group was 60%,all the immunization groups could resist the infection of Aeromonas caviae to some extent,and the adjuvant group was better than the vaccine group.All immune groups in the total bacterial content assay were effective in inhibiting the value-added of Aeromonas caviae in crucian carp and could reduce the total bacterial content in systemic organs.The final results showed that inactivated vaccination of crucian carp could produce immune protection in the fish,and aluminum adjuvant,glucan,APSs and propolis as adjuvants could improve the immunity and anti-infection ability of crucian carp against Aeromonas caviae AC-CY.The overall immunity of crucian carp in the APSs and propolis groups was the strongest,followed by the glucan group,and the aluminum adjuvant group was slightly lower than the former in all results.In conclusion,the screening of inactivated vaccine adjuvants for Aeromonas caviae,which are more suitable for mass production,which may be more effective in prevention of Aeromonas caviae,and to provide stronger data support and reference in the application of inactivated vaccine adjuvant for Aeromonas caviae. |
