An ALV-J isolate is responsible for spontaneous haemangiomas in layer chickens in China.

Subgroup J avian leukosis virus (ALV-J), first isolated in 1989, mainly induces tumours of myeloid leukosis (ML) in meat-type chickens. In 2006, ALV-J strain SCAU-HN06 was isolated from commercial layer hens with spontaneous haemangiomas in China. To confirm its role in the induction of haemangioma, we constructed a full-length copy of the proviral genome from SCAU-HN06, recovered virus from DF-1 cells detected by enzyme-linked immunosorbent assay, characterized its growth property and investigated its pathogenicity. The recovered virus appeared to be identical to SCAU-HN06 analysed by both blast gene sequences and indirect immunofluorescence assay. It also showed similarities in growth to the parental wild-type virus in vitro. The pathogenicity of the rescued and parental virus in specific-pathogen-free White Leghorn chickens was investigated. Both SCAU-HN06 and rSCAU-HN06 could induce haemangioma, with incidence of 52% and 42.8% respectively. Overall, our findings indicated that the ALV-J strain SCAU-HN06 was the causal agent inducing haemangiomas rather than ML in certain layer chickens.

The PI3K/Akt pathway is involved in early infection of some exogenous avian leukosis viruses.

Avian leukosis virus (ALV) is an enveloped and oncogenic retrovirus. Avian leukosis caused by the members of ALV subgroups A, B and J has become one of the major problems challenging the poultry industry in China. However, the cellular factors such as signal transduction pathways involved in ALV infection are not well defined. In this study, our data demonstrated that ALV-J strain NX0101 infection in primary chicken embryo fibroblasts or DF-1 cells was correlated with the activity and phosphorylation of Akt. Akt activation was initiated at a very early stage of infection independently of NX0101 replication. The specific phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 or wortmannin could suppress Akt phosphorylation, indicating that NX0101-induced Akt phosphorylation is PI3K-dependent. ALV-A strain GD08 or ALV-B strain CD08 infection also demonstrated a similar profile of PI3K/Akt activation. Treatment of DF-1 cells with the drug 5-(N, N-hexamethylene) amiloride that inhibits the activity of chicken Na(+)/H(+) exchanger type 1 significantly reduced Akt activation induced by NX0101, but not by GD08 and CD08. Akt activation triggered by GD08 or CD08 was abolished by clathrin-mediated endocytosis inhibitor chlorpromazine. Receptor-mediated endocytosis inhibitor dansylcadaverine had a negligible effect on all ALV-induced Akt phosphorylation. Moreover, viral replication of ALV was suppressed by LY294002 in a dose-dependent manner, which was due to the inhibition of virus infection by LY294002. These data suggest that the activation of the PI3K/Akt signalling pathway by exogenous ALV infection plays an important role in viral entry, yet the precise mechanism remains under further investigation.

[Sequence and promoter efficacy analysis of avian leukosis virus subgroup J strains of different pathotypes].

To characterize the long terminal repeat (LTR) of the ALV-J strain which can induce hemangioma, fragments of provirus LTR of the three different ALV-J strains SCAU-HN06, NX0101 and JS-nt were amplified with a pair of specific primers, then cloned and subjected to sequence analysis. In comparison with the prototype ALV-J strains HPRS-103 and ADOL-7501, the LTRs of domestic strains (SCAU-HN06, NX0101, JS-nt and SD07lk1) had an 88.0%-97.2% nucleotide sequence identity; the U5 and R regions in the LTR had a high nucleotide similarity, while the U3 region in the LTR showed significant variance. The LTR fragments from the different ALV-J strains were inserted into the upstream of bacterial CAT gene of the plasmid pCAT-Basic, respectively. The resultant recombinant plasmids were transfected into DF-1 cells. The transfected cells were harvested 48 h post-transfection, and cell lysates were prepared for CAT expression detection. The CAT assay was performed using CAT-ELISA. The results showed that the promoter activity of the LTRSCAU-HNO6 was a little higher than those of LTRJS-nt and LTRNX0101, but there was no significant difference in the promoter activity among the compared LTRs.

A Massachusetts prototype like coronavirus isolated from wild peafowls is pathogenic to chickens.

Coronavirus infection was investigated in apparently healthy wild peafowls in Guangdong province of China in 2003, while severe acute respiratory syndrome (SARS) broke out there. No SARS-like coronavirus had been isolated but a novel avian coronavirus strain, Peafowl/GD/KQ6/2003 (KQ6), was identified. Sequence analysis revealed that KQ6 was an avian coronavirus infectious bronchitis virus (IBV), a member of coronavirus in group 3. The genome sequence of KQ6 had extremely high degree of identity with that of a Massachusetts prototype IBV M41. KQ6 was pathogenic to chickens but non-pathogenic to peafowls under experimental conditions. Seventeen out of fifty-four (31.48%) peafowl serum samples were tested positive for specific antibodies against IBV. Present results indicate that the peafowl isolate KQ6 is a Massachusetts prototype like coronavirus strain which undergoes few genetic changes and peafowl might have acted as a natural reservoir of IBV for very long time.