RAPID DIFFERENTIATION OF VACCINE STRAINS AND FIELD ISOLATES OF INFECTIOUS LARYNGOTRACHEITIS VIRUS BY RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM OF PCR PRODUCTS

A procedure was developed for differentiation of vaccine strains and f ield isolates of infectious laryngotracheitis virus (ILTV) by restrict ion fragment length polymorphism (RFLP) of DNA fragments amplified fro m the genome of ILTV by polymerase chain reaction (PCR). RFLP patterns of viral thymidine kinase (TK) gene, glycoprotein C (gC) gene, glycop rotein X (gX) gene and ICP4 gene amplified from different ILT viruses were compared. The results showed that the vaccine strain of tissue-cu lture-origin (TCO) could be readily distinguished from other ILT virus es. Moreover, two out of the four field isolates could be differentiat ed from vaccine strains of chicken embryo origin (CEO); but the remain ing two field isolates were identical to the CEO vaccine strains. Thes e results suggested that both vaccine-like and vaccine-unlike ILT viru ses were involved in the field outbreak of this disease, and that the PCR/RFLP procedure could serve as a fast and sensitive method for the detection and differentiation of vaccine strains and field isolates of ILT viruses. (C) 1997 Elsevier Science B.V.