ABSTRACT
Clinical cases of hepatitis-hydropericardium syndrome (HHS) from fowl adenovirus serotype 4 (FAdV-4) have increased in China since 2013. Therefore, the development of a new serologic method for HHS detection is now urgent. Here, the FAdV-4 strain JSJ13 was used to construct a plasmid for prokaryotic expression of the JSJ13 fiber-2 protein. The protein, purified by affinity chromatography, was refolded by gradient dialysis. After coating a 96-well plate with the purified fiber-2 protein (1.5 µg/ml), standard serum and secondary antibodies (1:200 and 1:6000 dilutions, respectively) were used to develop an indirect ELISA (I-ELISA). Nine field-collected serum samples and JSJ13-positive serum were tested by I-ELISA and the results corresponded with those of the serum neutralization test. The I-ELISA was used to test 450 clinical serum samples from different parts of China. Chickens from nonvaccinated flocks had low antibody titers and low virus positivity rates. In contrast, FAdV-4 vaccinated chickens were strongly positive, and the positivity rates of all the flocks exceeded 73.3%. The newly developed I-ELISA with the recombinant JSJ13 fiber-2 protein as the antigen detected antibodies to FAdV-4 accurately and sensitively.
Subject(s)
Adenoviridae Infections/veterinary , Antibodies, Viral/analysis , Aviadenovirus/isolation & purification , Capsid Proteins/immunology , Chickens , Enzyme-Linked Immunosorbent Assay/veterinary , Poultry Diseases/diagnosis , Adenoviridae Infections/diagnosis , Adenoviridae Infections/virology , Animals , China , Enzyme-Linked Immunosorbent Assay/methods , Hepatitis, Viral, Animal/diagnosis , Hepatitis, Viral, Animal/virology , Poultry Diseases/virology , Recombinant Proteins/immunologyABSTRACT
Fowl adenoviruses (FAdVs) have a worldwide distribution and are associated with a variety of diseases, causing considerable economic losses to the poultry industry. We characterized 10 FAdVs isolated from China in 2015-2016 and assessed the pathogenicity of a FAdV-8 strain in specific-pathogen-free (SPF) chickens. Phylogenetic analysis of a hexon gene revealed that only 1 of the 10 isolates belonged to FAdV-8, whereas others belonged to FAdV-4, indicating that Chinese FAdVs were mainly FAdV-4 in recent years. The pathogenicity experiment of the FAdV-8 strain CH/SD/2015/09 showed that no clinical signs were observed in infected chickens. Necropsy displayed mild necrotic foci and petechial hemorrhage of livers collected at 5 days postinfection (dpi). Histopathologic examination identified the presence of intranuclear inclusion bodies in hepatocytes. No virus was detected in oral and cloacal swabs at 5 dpi, and only viral DNA could be measured in kidneys collected at the same time. The results revealed that CH/SD/2015/09 had no obvious pathogenicity in 5-wk-old SPF chickens, which could provide a better understanding about the pathogenicity of the FAdV-8 serotype.
