Pathogenicity Of ALV-A And The Immunoprotection Of Its Subunit Vaccine In Chickens And In Quails

A subgroup avian leukosis virus(ALV-A) is a kind of retrovirus, which can cause immune suppression, lymphatic tumour, hemangioma, and even death in chickens. The serological survey of ALV-A suggests that the positive ratio of ALV-A in chickens flocks in China is more than 47.9%; In recent years, some reports show that ALV-A was separated from dead wildbirds in northeast of China, which suggests that the birds might be hosts of ALV-A, but little has been known about the pathogenicity of ALV-A in birds. In this study, a new ALV-A strain was separated from the native chickens with tumors, the pathegenicity of ALV-A in chickens, quails and pigeons were compared, and the immunoprotection of ALV-A subunit vaccine in chickenc and quails was evaluated.The samples of chickens' tumors from Shandong Weifang City was detected by PCR and IFA and virus separation method in vitro and genome sequencing and analyzed the virus evolutionary relationships; the viremias and the cloacal detoxification were detected in the innoculated quails with three diffent doses of ALV-A-SDAU09C1 strain at 7-day-age and weekly compared in adult quails and pigeons and chickens after innocalation with 106 TCID50 of ALV-A-SDAU09C1 strain. The breeding quails and chickens were inoculated with the prepared ALV-A subunit vaccine and the hatched birds from the inoculated breeding birds were challenged and the ratios of viremia and cloaca detoxification and death were analyed.The results are as follows:(1) A new ALV-A strain were succeedly separated from the black native black chickens, named as ALV-A-SDWF1507, whose homology is closest to the published ALV-A strains: PDRC-1039?PDRC-3246?PDRC-3249.(2) the viremia(0/15) and cloacal detoxification(0/15) and tissue tumor(0/15) were all negative in the innoculated quails with three doses of ALV-A.(3)80%(4/5) of chicken were positive to viremia and cloacal detoxification during 21 days observation after inoculation with 106 TCID50 of ALV-A, Only17%(1/6) of quails was positive to viremia at 6 dpi and none(0/6) was positive to cloacal detoxification and none(0/5) of the inoculated pigeons was positive to viremia and cloacal detoxification; ALV-A was negative in the visceral tissues of quails and pigeons except forchickens with positive viremia.(4) ALV-A subunit vaccine combing Cp G adjuvants could induce all theinoculated breeding chickens to proect 78% of their offsprings against ALV-A infection.; additionally, can also induce the inoculated breeding quails to proect 85%of their offsprings against ALV-A infection.Conclusion: A new ALV-A strain were succeedly separated from the black native black chickens and chicken is more susceptible to ALV-A than quails and pigeons; ALV-A subunit vaccine combining with Cp G-ODN adjuvant can induce breeding birds to protect most of their offsprings against early infection of ALV-A. These results help to understand the scientific significance of ALV-A in wildbirds and to control the popular of ALV-A in breeding chickens.