Sequence and promoter efficacy analysis of avian leukosis virus subgroup J strains of different pathotypes / 病毒学报

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.

Cloning and analysis of full-length genes of a H9N2 subtype avian influenza virus isolated from Guangdong / 病毒学报

Eight full-length genes of an avian influenza virus Chinese isolate of H9N2 subtype, A/Chicken/Guangdong/HL/2006 (H9N2) (abbreviated as Ck/GD/HL/06), were amplified by RT-PCR, including the 5' and 3' non-coding region. All the genes were cloned and sequenced. The phylogenetic analysis results showed the HA gene of Ck/GD/HL/06 was located in the same phylogenetic clade as Dk/HK/Y280/97 (H9N2), while the Dk/HK/Y280/97-like viruses had been predominately isolated from chickens in mainland China. After the analysis of glycosylation sites and receptor-binding sites in the HA, it was shown that the HA of Ck/GD/HL/06 exhibited the common feature of H9 subtype avian influenza virus isolated from China, but the leucine (Leu) residue at the amino acid position 226 indicated the potential of binding with SA alpha,2-6 receptor. The three internal genes of Ck/GD/HL/06 (PB1, PA and NP) had the highest nucleotide identity with A/Viet Nam/1203/2004 (abbreviated A/VN/1203/04) isolate, which was shown to be transmitted from chickens to human and caused lethal infection in human. No analogous H9N2 strains was reported in previous studies. Based on the high similarity of Ck/GD/HL/06 three genes to A/VN/1203/04, it was suggested that the possibility of generating new highly pathogenic H5N1 AIVs by recombination was worthy of our attention. Further studies should be needed for molecular epidemiologic surveillance of H9N2 AIV in the south China for a long time.