Genome sequence determination and analysis of a Chinese virulent strain, LMS, of Gallid herpesvirus type 2

Marek's disease (MD) is a neoplastic and neurodegenerative disease of chickens, which is caused by the Gallid herpesvirus type 2 (GaHV-2). Although vaccination has been used widely in China, MD still occurs frequently. Some molecular epidemiologic studies have shown that Chinese GaHV-2 isolates seem to constitute a separate clade from strains isolated from other regions. However, more of a genomic background of the Chinese strains is necessary. In 2007, a virulent GaHV-2 field strain, named LMS, was isolated from diseased chicken flocks in the southwest of China. The whole genome sequence of LMS was determined to evaluate its genetic property. The genome of LMS is 177,526 bp long, and 197 open reading frames (ORFs) were predicted. Most of the ORFs have high sequence identity with homologous ORFs of reference strains. Two regions in the LMS genome are grossly different from other strains: the α-like region and the latency-associated transcripts (LATs) promoters. Evolutionary analysis demonstrated that LMS has a larger phylogenetic distance from most American isolated strains but a closer relationship with 648Ap80 and the European pC12/130 strain. The characterised genome of LMS provides further insight into the genetics of the Chinese GaHV-2 field strains, which is useful for the control of MD in China.