| Chinese perch(Siniperca chuatsi)is an important species of high quality fresh water fish in China.With the expansion of S.chuatsi’s breeding scale and the increase of breeding density,serious diseases have become the main bottleneck restricting the development of Siniperca chuatsi’s breeding industry.The most severe,especially since 1994,infective splenorenal necrosis virus(ISKNV).Therefore,the immune research on ISKNV is very important.Inactivated virus vaccine is one of the most promising vaccines because of its advantages of simple preparation,rapid development and stable immune effect.At the same time,effective immune adjuvants can improve the specific immune response of inactivated virus vaccine,so we plan to screen the immune adjuvants of ISKNV inactivated vaccine.In this study,we was prepared from ISKNV infection virus inactivated vaccine,and select four kinds of adjuvants of chitosan,poly(I:C),anisodamine and ims1312 in vaccine after mixing injection experiments.Then,the protective effect of adjuvant enhanced vaccine was studied by the anatomical comparison,serum enzyme activity,tissue section,qRT-PCR and individual mortality experiment.The main results obtained are showed as follow1.Chitosan as adjuvant can significantly enhance the protective effect of ISKNV vaccine on liver and spleenLiver and spleen samples were taken from each treatment group at 7 days after virus challenge.Under the infection of ISKNV,we observed the pathological changes and injuries between each treatment group and the control group,respectively.The results showed that poly(I:C)and chitosan as adjuvants had better protective effects in liver.Chitosan as adjuvant effectively enhanced the protective effect of the vaccine on the spleen.Through observation of liver and spleen,chitosan,as a new vaccine adjuvant,can effectively improve the protective effect of ISKNV inactivated vaccine on tissue melanin macrophage center(MMC)and tissue inflammation(TI).2.poly(I:C)and chitosan increased serum enzyme activity during infection.As the four kinds of vaccine adjuvants can protect the body’s immune organs,we selected three representative serum enzyme activity mechanical indexes,including CAT,ACP and BUN.The determination of CAT and ACP reflected that the body adopted different ways to protect the fish body from virus and foreign substances invasion,and the changes of BUN enzyme activity reflected that they protected the immune organs of mesonephron from virus and inflammation damage.Among the four adjuvants,poly(I:C)and chitosan played a better role on the increase of vaccine.3.Chitosan and anisodamine significantly inhibited virus replication and enhanced antiviral activity.In order to detect whether the four adjuvants can enhance the function of inhibiting virus replication,we detected the mRNA expression of the ISKNV007 in each treatment group within one week after virus challenge,and conducted qRT-PCR experiments on D1,D4 and D7,respectively.It can be found from the results that the number of viruses increased over time,but both the mesonephron group and the spleen group after the addition of adjuvant significantly reduced the virus replication,inhibiting the virus replication can promote the health of the body,and the mixed chitosan and anisodamine vaccine can better protect the body against the virus invasion of fish.These results are helpful for the fish to cope with virus infection and invasion,reduce ISKNV damage,and effectively protect the body.4.Chitosan and anisodamine can effectively increase the survival rate of S.chuatsi under ISKNV infection.To explore the overall protective effect of the mixed vaccine with four kinds of adjuvants on ISKNV infection,we screen four kinds of adjuvants by measuring the survival rate of S.chuatsi under virus infection.As can be seen from the results,chitosan and anisodamine showed more significant improvement in the survival rate of the vaccine under individual challenge infection,while the other two groups showed no significant improvement.This indicated that the protective effect of the vaccine was limited in the individual infection experiment.When mixed with chitosan or anisodamine,the mandarin fish could be more effectively protected from ISKNV damage,and the chitosan and anisodamine could be used as a new type of immune adjuvant to inactivate ISKNV virus.Collectively,These results showed that chitosan and poly(I:C)enhanced the protective effect of the vaccine on the liver and spleen of the mandarinfish under ISKNV infection.Meanwhile,the effects of CAT,ACP and BUN in serum were enhanced It also increased cytokine levels in the early stages of immunity.Chitosan and anisodamine significantly inhibited virus replication and enhanced antiviral activity.Finally,chitosan and anisodamine effectively increase the survival rate of Siniperca chuatsi under ISKNV infection.These adjuvants effectively improve the function of inactivated vaccine,chitosan is significantly better than other adjuvant selection,can be used as a new type of immune adjuvant to ISKNV inactivated vaccine,and provides a new way for the prevention and treatment of diseases in the future. |
