Development Of Trivalent Inactivated Vaccine And Yolk Antibody Against Fowl Adenovirus Group ?

Fowl adenovirus group ?(FAdV-1)clinically mainly causes chicken hydropericardium-hepatitis syndrome(HHS)and inclusion body hepatitis(IBH).Among its 12 serotypes,each seropype can cause chicken inclusion body hepatitis,only fowl adenovirus group ? serotype 4(FAdV-4)can cause chicken hydropericardium-hepatitis syndrome.In the past five years,these two diseases have been outbreaks in many provinces of China,which has caused great economic losses to the poultry farms,and there is currently no commercial vaccine to prevent and control fowl adenovirus group ? in China.In view of this,three dominant serotype strains FAdV-2,FAdV-4 and FAdV-8b were selected in this study to prepare FAdV-I trivalent oil emulsion inactivated vaccine and yolk antibody in order to provide reference for the prevention and control of fowl adenovirus group ?.1 Proliferation of FAdV-2?FAdV-4?FAdV-8b and preparation of trivalent inactivated vaccineThe study used leghorn male hepatocellular(LMH)to proliferate FAdV-2,FAdV-4,and FAdV-8b,after PCR identification and TCID50 determination of the collected virus,the final concentration of 0.15%formaldehyde solution was used for inactivation,and the FAdV-I trivalent inactivated vaccine was prepared according to the 2:1 oil-water ratio,and its quality was tested.The results showed that the LMH could be stably passaged,which were beneficial to the proliferation of FAdV-I.The TCID50 of the harvested FAdV-2,FAdV-4,and FAdV-8b were 10-6.62/0.1mL,10-7.78/0.1mL,and 10-7.30/0.1mL,respectively.The appearance of the vaccine was a uniform emulsion,water-in-oil formulation,stability and sterility testing were in line with the requirements,7 days old SPF chickens could be completely absorbed by the body within one week after inoculation,after 14 days of observation,the chickens were in good mental state,without adverse reactions.2 Evaluation of immune efficacy of fowl adenovirus trivalent oil emulsion inactivated vaccineThe vaccine prepared in Study 1 was inoculated into 7-day-old SPF chicks to test the minimum immune dose,antibody level titer and clinical protective efficacy.The results showed that the minimum immunization dose of the vaccine was 0.4 mL per chicken.The antibody level of the immunized chickens began to increase in the 2nd week after immunization,reached the highest in the 4th week,at this time,the antibody level produced by FAdV-2,FAdV-4,and FAdV-8b were 1:1230,1:1413 and 1:1349,respectively,and gradually declined in the later period.After 14 days of vaccine immunization,the chickens of each group were injected with 0.2mL of FAdV-2,FAdV-4,FAdV-8b virus solution,respectively,after 14 days of observation,all the chickens survived,no pathological changes after necropsy,PCR tests were negative on the 3rd,5th,7th,10th,and 14th days after virus injection,the clinical protection rate was 100%.Studies have shown that the trivalent oil emulsion inactivated vaccine had good immune effect and high clinical protection rate,which could provide a reference for the prevention and control of FAdV-I.3 Preparation of trivalent yolk antibody of FAdV-2?FAdV-4 and FAdV-8bThe vaccine prepared in the above studies was immunized to laying hens three times,and their sera and yolk antibody were collected every week for titer monitoring after the first immunization.Take yolk antibody with antibody titer higher than 1:1024 for quality inspection,and the qualified yolk antibody titers were diluted to 1:1024 and then inoculated with chicks for chicken prevention and treatment tests.The results showed that the serum and yolk antibody titer of the laying hens started to increase in the 2nd week after the first immunization and reached the highest at the 11th week,and then maintained above 1:1024.The quality inspection of the prepared yolk antibody meet the requirements,and the chickens were in good mental state after injection,and there were no adverse reactions within 14 days.After inoculating 1.0 mL of yolk antibody with a titer of 1:1024 into the chickens of each group for 3 days,0.2mL of FAdV-2,FAdV-4,FAdV-8b virus solution was injected,during the observation period of 14 days,all the chickens survived,and there were no pathological changes in the autopsy,PCR tests were negative on the 3rd,5th,7th,10th and 14th days after virus injection,and the clinical protection rate was 100%.After artificially infecting the chickens of each group with 0.2mL of FAdV-2,FAdV-4,FAdV-8b virus solution for 1 day,1.0mL of yolk antibody with a titer of 1:1024 was injected,after 14 days of observation,the cure rate of FAdV-2 infected chickens was 100%,and the cure rate of FAdV-4 and FAdV-8b infected chickens was 90%.It shown that the quality of the yolk antibody prepared by the study was qualified and had high safety,and had good preventive and therapeutic effects on chickens infected with FAdV-2,FAdV-4 and FAdV-8b.