Evaluation Of The Resistance Of Different Mirror Carp Breeding Generations To CyHV-3

Koi Herpes Virus Disease?KHVD?is caused by Koi Herpes Virus III?CyHV-3?,with this disease exploding for many years in the global carp breeding areas,it has brought large-scale economic losses.Therefore,it is important to study the anti-CyHV-3 defense mechanism to prevent and control the disease.At present,breeding new varieties of anti carp Koi herpes virus were carried out in the F₃ generation.By means of the real-time fluorescence quantitative PCR technology and the immunoassay kit,the study focused on the changing patterns of the virus load of CyHV-3,the expression of immune-related genes?TRAF6,MyD88 a,IL-1?,TLR7 a,I-IFN?,phosphatase activity?AKP,ACP?,antioxidant capacity?GSH,SOD,T-AOC?,specific immune related index?IgM?and non-specific immunity index?LZM,C3,C4?,thereby to evaluate the resistance of different mirror carp breeding generations to herpes virus CyHV-3.The results of this study are as follows:CyHV-3 load comparison study: in viral infection,the CyHV-3 viral load in spleen of the three breeding generations were significantly higher than that in kidney?P<0.05?,which indicted that CyHV-3 may mainly infect the spleen.The CyHV-3 load decreased respectively in the breeding generations F₁,F₂,F₃ after infection,and the CyHV-3 load in F₃ was significantly lower than that in F₁ and F₂?P <0.05?.Therefore,it can be concluded that the disease resistance of breeding generations has the trend of increasing generation by generation,and the resistance to disease of F₃ is remarkable.Immune gene expression analysis:?1?Uninfected period,the expression of I-IFN showed a decreasing trend in three generations F₁,F₂,F₃ and the expression of TRAF6,TLR7 a,MyD88a and IL-1? showed an increasing trend,only the expression of TRAF6 gene in F₃ was significantly higher than that in F₁,F₂?P <0.05?.The above results indicated that only the TRAF6 gene had been breeding.?2?Infection period,The expression levels of I-IFN,TLR7 a,TRAF6,MyD88 a and IL-1? genes showed an upward trend in the three breeding generations.The gene expressions of TRAF6 in the spleen of F₃ were higher than those in the F₁?P<0.05?.The gene expression of IL-1?and MyD88 a in F₃ spleen was higher than that in F₁ and F₂?P<0.05?.In the F₃ kidney of IL-1? and TRAF6 gene expressions were higher than those in the F₁ and F₂?P<0.05?.Therefore,it can be concluded that the disease resistance of breeding generations has the trend of increasing generation by generation,and the F₃ is remarkable.There were significant differences in the expression of immune genes between spleen and kidney?P<0.05?.The expression of TLR7 and I-IFN gene in spleen was significant higher than that in kidney?P <0.05?,the expression of TRAF6,MyD88 and IL-1? in kidney was significantly higher than that in spleen?P <0.05?,The above results indicated that the kidney may be the major immune organ against CyHV-3,and TRAF6,MyD88 and IL-1? genes play an important role in antiviral infection.Comparison of immune indexes in tissues: In three breeding generations' AKP activity showed an upward trend,and the trend of ACP activity was opposite to that of AKP,presumably because the optimum pH value of ACP and AKP was different.The activity of AKP in F₂,F₃ was significantly higher than that in F₁?P <0.05?,indicating that the activity level of AKP was enhanced by generations.The activity of AKP in kidney was higher than that in spleen,and the activity of ACP in spleen was higher than that in kidney,indicating that the activity of the two phosphatase in different tissues had different activity level.There was no significant difference in SOD between spleen and kidney?P>0.05?,the T-AOC in spleen was significantly higher than that in kidney?P<0.05?,and the F₂'s GSH index in kidney was significantly higher in spleen?P<0.05?,but there was no significant difference between the rest?P>0.05?.The indexes of SOD,T-AOC and GSH in F₃ were higher than those in F₁,and the indexes of SOD and T-AOC in F₃ were higher than those of F₂?P<0.05?;the GSH indexes in F₂ were significantly higher than those in F₁ and F₃?P <0.05?.The results indicated that the disease resistance of breeding generations has the trend of increasing generation by generation,and the resistance to disease of F₃ is remarkable.Changes of immune index in serum: nonspecific immune?LZM,C3,C4?and specific immune index?IgM?,showed an upward trend between the three breeding generations,the activity levels of LZM and IgM in F₃ were significantly higher than those in F₁?P <0.05?,and the LZM and C4 in F₃ were significantly higher than in F₂?P<0.05?.The C4 in F₂ was lower than in F₁,but with not significant different?P >0.05?.Those results indicating that the disease resistance of breeding generations has the trend of increasing generation by generation,and the resistance to disease of F₃ is remarkable.The result of culture contrast experiment: In the contrast experiment,the survival rates of F₁,F₂ and F₃ were 61.1%,86.6% and 92.5% respectively,the control group is57.4%,indicating that the resistance to disease was increased by generation by generation,and the disease resistance of F₃ was remarkable.In combination,CyHV-3 viral load,immune gene expression and immune related indicators all indicated that he resistance to disease was increased by generation by generation,and the disease resistance of F₃ was remarkable.This results was consistent with the culture contrast experiment.These results showed that we have successfully evaluated the resistance to disease in breeding generations of the carp through the above three indicators.It also shows that the disease resistance assessment method is an effective method for assessing the disease resistance of carp.