A Preliminary Study On The Application Of Fusion Bursin Peptide As Growth Regulator And Immunomodulator In Chickens Congenitally Infected By ALV

Avian Leukosis(AL)is a neoplastic disease caused by the Avian Leukosis Virus(ALV)that severely affects the development of the poultry industry.It caused slow growth of chickens,a decrease in the egg production rate of laying hens and immunosuppression.Meanwhile,it caused huge economic losses and adverse social impact.There are many ALV subgroups and the phenotypes of the tumors induced by ALV are complex.Once it occurs,it is difficult to control and completely eradicate.In addition to performing AL purification of breeder flocks,biological agents should be developed to reduce or mitigate the adverse effects of ALV.Therefore,this experiment used chicken embryo yolk sac inoculated with recombinant ALV to establish an ALV congenital infection chicken model.In the course of vaccination,prokaryotic expression of fused bursin(BS)was injected to investigate the effect of BS on ALV-induced growth inhibition and immunosuppressive effects,providing a scientific basis for the clinical application of fused BS.Methods:At the age of 7 days(d),chick embryos were inoculated with 3000 TCID50 ALV natural recombinant virus FJ15HT0 to establish an animal model of congenital ALV infection.Infected chickens were randomly divided into BS treatment group and infection control group.A mock control group and a mock BS treatment group were set up at the same time.All chicks were vaccinated with NDV attenuated vaccines and their subcutaneous vaccines were injected into the inactivated vaccine against avian influenza virus(AIV)subtype H5 at 1 d and 14 d after hatching.The treated chickens were intramuscularly injected with 50 ?g of purified BS.All the chicks in the control group were injected intramuscularly with ultrasonic supernatant solution of BL21.At 21 days,28 days,35 days,and 42 days of the chicks,the serum was collected for the detection of various indicators,and the body weight,tissue and organ index,NDV,and AIV-H5 for the congenital and non-infected chickens were statistically analyzed.Antibody titers,serum cytokines(IL-2,IL-4,IFN-?)and antibody subtypes(IgG1,IgG2)and the expression levels of ALV gp85 and CNTFR? genes in experimental animal tissues were detected.The transcriptional analysis of bursa of SPF chicken with BS 1 day before injection,1 day,3 days and 7 days after injection.Results:(1)At 7 days,there was a significant difference between the body weight of the vertical bacteria group and the other three groups(blank bacterial group,blank BS group,and vertical BS group)(P<0.01).At 14 days,there was a significant difference between the body weight of the blank bacterial group and the vertical bacterial group(P<0.01).At 35 days,there was a significant difference between the body weight of the blank bacterial group,the blank BS group and the vertical bacterial group(P<0.01).At 42days,there was a significant difference between the weight of chickens infected with the ALV group and the blank group(P<0.01).(2)There were significant differences in the liver index between the vertical and vertical BS groups(P<0.01).There was a very significant difference in the kidney index between the blank and the blank BS groups(P<0.01).(3)On the 42 days,there was a significant difference between the NDV antibody titer of the vertical bacterial group and the vertical BS group(P<0.01).In addition,fused BS has a certain maintenance effect on the growth and decline of NDV antibodies.(4)At 35 days and 42 days,there was a very significant difference between the AIV-H5 antibody titers between the blank bacterial group and the vertical bacterial group(P<0.01).In addition,the fused BS had a maintenance effect on the AIV-H5 antibody in chickens.(5)The effect of fused BS on IL-2 and IFN-y in serum of blank group was extremely significant(P<0.01).The effect of IL-2,IL-4 and IFN-? in serum of chickens infected congenitally with ALV was not significant(P>0.05).(6)At 42 days,there was a significant difference between the IgG1/IgG2 levels in the blank BS group,the vertical bacterial group,and the blank bacterial group(P<0.01).(7)The transcriptome analysis showed that fusion of BS involved PPAR,MAPK and other signaling pathways,which caused a significant downregulation of MAPK11 gene in the MAPK pathway(P<0.05).(8)In the bursa of Fabricius,there was a very significant difference in the expression of gp85 between the vertical and vertical BS groups(P<0.01).In the liver tissue,the expression level of CNTFR? in the mock bacterial group was 3.7 times that of the blank BS group.In thymus tissue,the expression of CNTFRa in the vertical bacterial solution group was 2.58 times that of the vertical BS group.Conclusions:The fusion of BS can improve the weight gain efficiency of ALV-infected animals,increase the antibody titer of the animals against inactivated vaccines,increase the duration of antibody peaks for ALV infected animals against attenuated vaccines,and inhibit the replication of ALV.Therefore,it has the value of becoming a feed additive and an immunomodulator.