Pathogenicity Of SPF Chickens Infected With Reticuloendotheliosis Virus And The Inhibition Effect Of Type Ⅰ Interferon On Reticuloendotheliosis Virus In Vitro And In Vivo

Reticuloendotheliosis(RE)is a viral tumor disease caused by Reticuloendotheliosis virus(REV).Clinical infections are mainly manifested as immunosuppression,fatal reticulocell tumor,and the generation of chronic tumors.In recent years,epidemiological surveys have shown that REV infection has become quite common in China,and so far no commercial vaccine and drugs are available for its prevention and control.Vertical transmission is an important mode of REV transmission,and the implementation of germline decontamination is one of the possible effective ways to control it.To this end,this study observed the morbidity characteristics and detoxification patterns of chickens infected with REV by different transmission routes,in order to provide reference data for future implementation of breeding source decontamination,and explored the in vivo and ex vivo inhibitory effects of interferon on REV,in order to provide new strategies for the prevention and control of the disease.1.Pathogenicity of SPF chickens after REV infection in different waysIn order to systematically understand the difference of pathogenicity of REV infected by different infection methods,this experiment used chicken embryo yolk sac inoculation,1-day-old intraperitoneal inoculation and cohabitation infection to infect SPF chickens with REV,and used a combination of assays to initially explore the pathogenesis and detoxification patterns of chickens infected with REV by different infection methods.The results showed that REV infection caused a significant inhibition of body weight gain in SPF chickens and a significant decrease in antibody potency after NDV and AIV-H9 vaccination,both of which were significantly different from the blank control group(P < 0.05);the chickens in both the REV yolk sac infection group and the intraperitoneal infection group continued to detoxify to the outside world throughout the test period,and the number of detoxified chickens was positively correlated with the age of infection.The number of detoxified chickens was positively correlated with the age of infection.The number of chickens in the yolk-sac infected group started to detoxify from their shells and reached the peak of detoxification on the 21 st day after infection,while the chickens in the ventral infected group had two peaks of detoxification,on the 14 th and 42 nd day after infection,respectively.The results of REV carriage status in blood samples from each experimental group showed that the viral load in the blood of chickens in the yolk sac infection group was significantly higher than that in the peritoneal infection group(P < 0.05),and the positive rate of REV viremia in the test chickens of both infection modes gradually increased with increasing age.The results of REV antibody detection showed that both the yolk-sac infected group and the peritoneal infected group detected REV positive test chickens on day 28 after infection,and the antibody titers showed an increasing trend followed by a decreasing trend,with the highest REV antibody titers on day 42 and 63 after infection,respectively.The results showed that RT-PCR and virus isolation were the best in detecting vertical transmission in chickens,so the applicability of the detection method was crucial to control the spread of REV.2.Inhibitory effect of type Ⅰ interferon on REV in vitro and in vivoIn this study,the inhibitory effect of interferon on REV proliferation was observed by adding different concentrations of type Ⅰ interferon to DF-1 cell cultures containing the same number of viruses and inoculating the same number of viruses with REV in DF-1 cell cultures containing different concentrations of type Ⅰ interferon,using fluorescence quantitative RT-PCR and indirect immunofluorescence.The results of indirect immunofluorescence showed that the specific fluorescence intensity of REV inoculated with interferon and then REV positive control group was not significantly different,however,the specific fluorescence intensity of REV inoculated with interferon and then interferon positive control group was significantly stronger than that of REV inoculated with interferon and the specific fluorescence intensity was negatively correlated with the concentration of interferon.The results of the quantitative fluorescence RT-PCR assay showed that the therapeutic effect of the REV followed by interferon group was better than that of the interferon followed by REV group,and the therapeutic effect was positively correlated with the concentration of interferon.The results of in vivo tests also showed that REV vaccination followed by interferon treatment could effectively alleviate the immunosuppression caused by REV infection,and also had significant advantages in alleviating liver and spleen enlargement,inhibiting liver carriage,fecal detoxification and viral replication in blood.In conclusion,this study preliminarily explored the pathogenesis characteristics and detoxification rules of SPF chickens infected with REV in different ways,and confirmed that type Ⅰ interferon treatment can inhibit REV replication,providing a new strategy for purification and prevention of REV.