Analysis of Korean strains of infectious laryngotracheitis virus by nucleotide sequences and restriction fragment length polymorphism

Korean field strains of infectious laryngotracheitis virus (ILTV) were anal yzed by comparison of nucleotide sequences of thymidine kinase (TK) and gly coprotein G (gG) genes and polymerase chain reaction-restriction fragment l ength polymorphism (PCR-RFLP) patterns. Main differences among TK gene sequ ence were found in both amino acid at 252 and mRNA polyadenylation signals. In virulent strains, amino acid 252 of TK gene was methionine but was thre onine in low virulence and vaccine strains. The mRNA polyadenylation signal s of TK gene were identified at 24 bp downstream from the stop codon in vir ulent strains, but not in low virulence and vaccine strains. The gG gene of all virulent strains showed the same nucleotide sequence except for N87278 which had a gG gene sequence identical to that of vaccine strains. The vir ulent ILTV strains differed from low virulence and vaccine strains in PCR-R FLP patterns of TK and gG genes. The RFLP patterns of TK and gG genes of lo w virulence ILTV strains were identical to those of vaccine strains. In the case of N87278, the PCR-RFLP patterns of TK and gG genes were identical to those of virulent and vaccine strains of ILTV, respectively. From these re sults, ILTV field strains were classified into three groups according to se quences of TK and gG genes and PCR-R-FLP and the virulent ILTV strains coul d be discriminated from low virulence and vaccine strains by PCR-RFLP of TK gene. And it was suspected that N87278 might be produced by in vivo recomb ination between virulent and vaccine strains of ILTV. (C) 2001 Elsevier Sci ence B.V. All rights reserved.