Research On Preparation Of Bacterial Ghost Of Pathogenic Aeromonas Veronii Strain CL0901 And Its Impact On Immune Function Of Carp And Hepcidin Gene Expression

Bacterial diseases,as the main types of aquatic animal disease,have caused huge losses to aquaculture.At the same time some zoonotic pathogenic bacteria has potential threat to human health.Aeromonas Veronii Strain CL0901 is a strain of gram-negative bacillus isolated from pathogenic cryprinus carpiod,which has strong pathogenicity.The infected fish body has symptoms,such as ulceration,fish scales fallen off the lesion site,exposed muscle etc.At present,chemical method and antibiotics as ways for the treatment of bacterial disease have many drawbacks.Compared with above methods,vaccination is a relatively safe and effective method.So many scholars have conducted a great deal of exploration on raising immunity of aquatic animals by using vaccines.In many vaccines,bacteria ghost is the whole bacterial shell formed of the gram-negative bacteria after splitting of the product of lysis gene E of phage PhiX174.In the process of inactivation,compared with traditional formaldehyde inactivated seedlings,it has retained the intact cell morphology and the surface antigen as well as the properties of some adjuvants,which can directly stimulate the immune response of the fish body,making it become an important new vaccine candidate.But the previous researches have laid much stress on the building.In order to promote development and promotion of this kind of vaccine,it is necessary to make the study of the immune effect on the aquatic animal after vaccination.After referring to a large quantity of literatures,it has been found that most scholars have started their researches from specific immune,namely valence of antibody and immune protective rate to explore the mechanism of the immune effect of the aquatic animals after vaccination while they have paid little attention to the nonspecific immune response and deeper study of immune related gene research.In order to make a more fully understanding process of the immune effect of bacterial ghost vaccine on the aquatic animals,the paper has used the prepared bacterial ghost of pathogenic aeromonas veronii strain CL0901 to inoculate the carp and it has studied the specific and non specific immune index of cyprinus carpio together with the changes of the amount of hepcidi expression.What is more,the study has provided a comprehensive study of the impact of the bacterial ghost of aeromonas veronii on the immunity of the carp so as to further supply some scientific references of bacterial ghost vaccine on the ways and effects of fish immune protection.The main research contents and results of the paper are as follows:The experiment was consisted of three treatments and conducted in cylindrical fiberglass tanks(260 L/tank): CLGs group injected with CL0901 ghost vaccine,FKC group with formalin killed cell vaccine and the control group with phosphate buffer solution(PBS).All treatments were injected on 1st,15 th and 29 th day after the experiment started.Three fish in each tank were sampled for blood and tissue at every 7 days after the first inoculation.The evaluation parameters included the serum antibody titer,relative percent survival(RPS),lysozyme(LZM),respiratory burst,complement protein 3(C3),myeloperoxidase(MPO),malonic dialdehyde(MDA)and relative expression content of hepcidin gene.(1)After 35 days,the antibody titer in CLGs group reached 26~28,and was able to maintain for a period of time;This number was significantly higher than that in other groups(P<0.05);The RPS was 57.70% in CLGs group,but 30.77% in FKC group.These results indicate that CLGS can enhance the level of serum antibody titer to strengthen specific immune under certain immune strength.Moreover,the effect of immune protection of CLGs is better than that of FKC.(2)After the secondary inoculation,the respiratory burst,serum LZM,and MPO of CLGs group were significantly higher than those of PBS group(P<0.05).C3 in CLGs group was significantly lower than that in PBS group on 35 and 42 d(P<0.05).The MPO and expression of hepcidin gene of FKC group were significantly lower than those of CLGs group(P<0.05).Above results indicate that CLGS can improve the content of the respiratory burst,serum LZM,and MPO to enhance non-specific immunity.(3)The expression of hepcidin gene occurs mainly in liver tissue,and the CLGS group was significantly higher than FKC group and PBS group on the 28 th day,it's about 4 times higher.Meanwhile,it was the same thing happened in spleen tissue.While in head kidney tissue,the CLGS group was significantly higher than FKC group and PBS group in the 21 day.These results indicated that the CLGs could enhance the serum antibody titer,respiratory burst,lysozyme,myeloperoxidase and relative expression content of hepcidin gene.As a whole,the effect of immune protection of CLGs is better than that of FKC.