Download Infectious laryngotracheitis (ILT) is an acute and highly contagious

Infectious laryngotracheitis (ILT) is an acute and highly contagious respiratory disease of chickens, caused
by an alphaherpesvirus, named Infectious Laryngotracheitis virus (ILTV). Recently, full genome sequences
of wild-type and vaccine strains have been analysed, but none was from Europe. The aim of this study was to
determine and analyse the complete genome sequences of five Italian ILTV strains. Sequences were also
compared to reveal the similarity of strains across time and to discriminate between wild-type and vaccine
strains. Genomes of 3 ILTV field isolates from outbreaks occurred in Italy in 1980, 2007 and 2011, and 2
commercial chicken embryo origin (CEO) vaccines were sequenced using the 454 Life Sciences technology.
Sequences were mapped on the reference sequence (Serva strain, GenBank accession no. HQ630064) using
Roche gsMapper. The length of the five ILTV genomes ranged from 153,650 bp to 153,662 bp. The
comparison with the Serva genome showed that 35 open reading frames (ORFs) differed across the five
ILTV genomes. Overall, 54 single nucleotide polymorphisms (SNPs) and 27 amino acid differences in 19
ORFs and 2 insertions of 9 and 3 nucleotides in two different ILTV genes were identified. Similarity among
the wild-type and between the wild-type and the vaccine strains ranged from 99.95% to 99.98%.
Phylogenetic analysis of the five strains and all the ILTV complete genomes available within the NCBI
GenBank database showed a dose relatedness of the three wild-type isolates, whereas the two vaccine strains
grouped into separate clusters. This study generated data on genomic variation among Italian ILTV strains
revealing that the genome is well conserved across time and between wild-type and vaccine strains. Results of
this study may contribute to the understanding of the molecular bases of ILTV pathogenicity and the genetic
differences between wild-type and vaccine ILTV strains.