Analysis Of Fibres Knob Domains Of Fowl Adenovirus Group â…  And Partial Biological Characterization Of The Viruses

Avian Adenovirus can be subdivided into three groups:groupâ… ,â…¡andâ…¢.Groupâ… includes the conventional groupâ… adenovirus and fowl adenovirus(FAV-1～2) isolates from chickens,turkeys,geese and other avian species,which share a common group antigen.The pathogenesis of Groupâ… virus is not well defined.They appear to be one of secondary pathogen in association with other diseases.As other adenoviruses,fowl adenovirus groupâ… (FAVI) is a icosahedral virus containing 240 hexamer and 12 pentamer capsomers.There is an interesring phenomenon that the penton of avian adenovirus presents two fibres which might bind to different receptors.In order to learn how the tow fibers of FAVI function in the pathogenesis,the sequences of knob domains of both fibres of FAVI from different origins(from chicken,duck or goose) were cloned and sequenced.The senqueces were analyzed and compared with each other in the same origin animal and between different origin animals.The results suggested that nucleotide homologies of knob domain of fibre 1 were almost 100%in the same origin,but only 22.6-100%of homologies between different origin animals.Nucleotide homologies of knob domain of fibre 2 were almost 100%no matter in the same origin or between different ones.These results indicated that fiber 1 may determine the host tropism of FAVI and take the main role in the process of infection.Fiber 2 could bind a uniform structure.Biological characterization of FAVI JS strain was investigated by PCR which amplify ITR fragment of the viral genome,virus morphology,heamagglutination(HA), cytopathogenic effect(CPE) and the pathogenic effect in SPF chicken embryoes.The results showed that the virus particales as a non-enveloped,round,about 70～80 nm in diameter.It could not agglutinate red blood cells(RBC) of chicken.CPE was found in CEK infected FAVI-JS strain post 3～5days.The cells showed clustering,bunching and falling off finally.The chicken embryos at 9～10days old were inoculated with the virus and died post 4～6days.The virus could cause visible chicken embryo lesions, such as blooding,delayed growth,lack of feathers.28 14-day old SPF chickens were inoculated intravenously with FAVI-G24-YZ0605 strain(goose-origin) at 10¹⁰TCID₅₀/chicken.2 chickens from experimental group and control group were killed respectively very 2 days post inoculation.The results demonstrated that typical lesions of inclusion body hepatitis were found when the the chickens infected with goose-origin FAVI-G24-YZ0605 strain.The basophilia intranuclear inclusion bodies whose characteristic of morphology was irregular were found in the hepatic cells.It indicated that goose-origin FAVI-G24-YZ0605 strain is a pathogenic factor to chickens,and could cause avian inclusion body hepatitis.