Effect Of Avian Leukosis Virus On Chicken Immune Function And Production Performance Through The Attenuated Vaccine Contamination

Avian leukosis virus(ALV)is an important poultry pathogen and its infection may result in low productivity and tumor mortality in chickens,which can lead to cellular and humoral immune suppression and growth inhibition,to bring significant losses to the poultry industry.In order to prevent the prevalence of ALV,many countries have implemented ALV eradication.However,due to the extensive spread of ALV,is still prevalent in China.Beside the vertical transmission,the ALV contaminated in attenuated vaccine is one of the important routes of infection.It has repeatedly reported ALV in attenuated vaccine contamination in China and other countries,which will result in significant losses to enterprises that have completed ALV eradication.Therefore,we conducted on the effect of different doses of ALV contaminated vaccine on Hyline brown chickens,and compared the different detection methods of ALV in the attenuated vaccine.1.The effect of ALV contamination on the immune function and production performance in attenuated vaccineIn order to explore the effects of ALV contamination in attenuated vaccine of production performance and immune function,Hyline-Brown Chickens were vaccinated with different doses of ALV-A mixed with commercially Marek's disease vaccine,and challenged with ALV-A and ALV-J at 7 days old of chickens,and simultaneously vaccinated with NDV,AIV-H9..The results showed that 10 TCID50 and 50 TCID50 ALV per plume attenuated MDV vaccines were used to cause the weight loss of Hyline-Brown Chickens,compared with the use of the non contaminated vaccine group,it has significant difference.The MDV vaccine group with contamination of 50 TCID50 ALV was significant lower than the 10TCID50 ALV.The MDV load compared with the use of the non contaminated groups also decrease after use the vaccine with two doses of ALV contaminated.The MDV vaccine group with contamination of 50 TCID50 ALV was significant lower than the 10TCID50 ALV.NDV andAIV-H9 antibody levels compared with the use of the non contaminated groups also decreased after use the vaccine with two doses of ALV contaminated.The MDV load compared with the use of the non contaminated groups also decrease after use the vaccine with two doses of ALV contaminated.Moreover,chickens were infected with ALV,at 7 days of age,the growth and immune inhibition was more obvious,and shows significant difference.The results of this study suggesting that we should prevent exogenous virus contaminated in attenuated vaccine.2.Interference and identification of endogenous Avian Leukemia Virus for the detection of ALV contaminated in the attenuated vaccines.Attenuated live vaccines carry a potential risk of contaminated with avian leukemia virus,especially for the ALV subgroup A(ALV-A),is known to one of the routes of ALV transmission.However,the ALV contamination in the attenuated vaccines for detecting using PCR assays is usually affected by the interference of endogenous ALV gene on chicken chromosome.At the present,the national standard of the procedure is the vaccine was treatment by different method and inoculated to chicken embryo fibroblasts after blind passages and determine the p27 using the ELISA kits.But,many poultry industry do not understand vaccine contaminated detection by PCR method,and induce a lot of disputes.The supernatant of the cell culture and the egg albumen were then assayed for ALV p27 antigen by ELISA method was negative.The primers were used to detect the Marek's disease virus(MDV),infectious bursa disease virus(IBDV)and fowl pox virus(FPV)vaccines were positive by PCR assay.However,avian leukosis virus-specific nucleic acid probes cross-hybridize spot detection kit was used to detect the above three vaccines,which showed negative to ALV.And a low dosage of 10 TCID50/1000 plumes contamination could be detected by dot-blot hybridization in attenuated vaccines.In conclusion,all data in this present study demonstrated that endogenous avian leukemia virus in SPF chicken embryo and its products may interfere the PCR molecular assays,and offered an available solution through the comparison test.