A recombinant avian leukosis virus associated with fowl glioma in layer chickens in Japan

Abstract

Fowl glioma is characterized by multiple nodular growth of astrocytes, and fowl glioma-inducing virus belonging to avian leukosis virus has been isolated from Japanese bantam as a causal agent. Subcutaneous neoplasms of the head and neck have been reported in layer chickens since 2003 in Japan, and fowl glioma concurred in these affected layers. In the present study, the histopathology of 240 layers, including 18 layers with subcutaneous neoplasms and 222 layers kept with the affected layers, was performed to clarify the characteristics of fowl glioma in layers. Microscopically, 103 layers showed non-suppurative encephalitis, and four layers had locally extensive proliferation or multiple nodules of astrocytes. Gliomas concurred in 11 layers with subcutaneous neoplasms and occurred independently in three layers. In addition, two layers had locally extensive proliferation of small, round cells in the cerebrum. The fowl glioma-inducing virus genome was not detected in the affected brains by nested polymerase chain reaction. Ten isolates were obtained from the affected brains. By nucleotide sequencing of the env gene, SU coding regions of these isolates were most closely related to myeloblastosis-associated virus-like viruses, but TM regions showed the highest similarity to endogenous viral (ev) loci. The genome of one isolate mainly consisted of ev loci and contained several parts of other avian leukosis/sarcoma viruses. These results show that the causal avian leukosis virus of fowl glioma is not just fowl glioma-inducing virus and that different avian leukosis virus strains having oncogenicity in the central nervous system by recombination are spread in layers in Japan.

Pathogenicity of avian leukosis viruses related to fowl glioma-inducing virus

“…The entire viral genome was sequenced using the cDNA sample of each isolate as previously described (Tomioka et al, 2004;Hatai et al, 2008b). PCR amplification was performed with three primer pairs*LTRfwd and Prev, GrevF and AD1, or H5 and IPLTRrev (Table 1)*using the GeneAmp PCR System 9700 (Applied Biosystems, Carlsbad, California) in the Max ramp speed mode.…”

“…Total RNA was extracted from cultured DF-1 cells using TRIzol reagent (Invitrogen Life Technologies, Carlsbad, California, USA). Reverse transcription (RT) was performed as previously described (Hatai et al, 2008b). As an internal control for RNA extraction and cDNA synthesis, PCR amplification was performed for all cDNA samples using primers specific to chicken b-actin (Table 1).…”

Cardiac Pathology and Molecular Epidemiology by Avian Leukosis Viruses in Japan

“…Reverse transcription (RT) was performed as previously described [12]. As an internal control for RNA extraction and cDNA synthesis, PCR amplification was performed for all cDNA samples using primers specific to chicken β-actin.…”

“…As an internal control for RNA extraction and cDNA synthesis, PCR amplification was performed for all cDNA samples using primers specific to chicken β-actin. The PCR for chicken β-actin was performed according to conditions described previously [12].…”

“…The env SU regions of 15 strains isolated from field cases and the complete virus genome of Km_5892 were sequenced as previously described [12], [16]. The complete genomic RNA (gRNA) of Km_5892 has been deposited in the DDBJ/GenBank (AB682778).…”