Abstract

Avian infectious laryngotracheitis (ILT) is a severe clinical respiratory disease of chickens and causes the clinical symptoms of difficulty in breathing and bloody coughing and as if involves laying hens affect the egg production. In order to cloning of the coding region of TK gene of ILT virus , PCR product of the open reading frame of the gene from DNA extracted of infectious tissue of involved poultry farms in different parts of south west of Iran was  amplified by PCR.  An 1141bp PCR product of the TK gene with BamHI, XhoI restriction sites were subcloned of pTZ57R/T and digested by the mentioned endonucleases. Digested insert cloned in to pGEX-4T-3 and transfected in E. coli cells. For the expression of TK protein, the pGEX-4T-3 recombinant vector was transformed and then induced in BL21 (DE3) strain of E. coli competent cells using IPTG, the presence of TK expressed protein was shown in immunoblotting and SDS-PAGE system. Analysis of the partial ILT virus TK gene sequences obtained from insert and was carried out. The Iranian ILT TK sequences were compared to 11 other corresponding sequences of ILT isolated in different countries. Nucleotide analyzing of the sequences were shown a variation of 0 - 62.8% and constructing phylogenetic tree revealed two clusters in it. Most of agreement was related to the known sequences in the TK gene in USA (S83714.1), China (DQ522947.1, AF435453.1), Switzerland (EU360946.1) and most of differences were related to Australian strains of this virus (GQ180115.1).

Key words: Avian infectious laryngotracheitis, Thymidine kinase, pTZ57R/T, pGEX-4T-3, Phylogenetic analysis, protein expression