Journal Article

Full Genome Sequence-Based Comparative Study of Wild-Type and Vaccine Strains of Infectious Laryngotracheitis Virus from Italy

Lavezzo, Enrico, Massi, Paola, Piccirillo, Alessandra, Niero, Giulia, Franchin, Elisa, Toppo, Stefano, Palù, Giorgio, Salata, Cristiano, Moreno, Ana

2016

Overview

Infectious laryngotracheitis (ILT) is an acute and highly contagious respiratory disease of chickens caused by an alphaherpesvirus, infectious laryngotracheitis virus (ILTV). Recently, full genome sequences of wild-type and vaccine strains have been determined worldwide, but none was from Europe. The aim of this study was to determine and analyse the complete genome sequences of five 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 three ILTV field isolates from outbreaks occurred in Italy in 1980, 2007 and 2011, and two commercial chicken embryo origin (CEO) vaccines were sequenced using the 454 Life Sciences technology. The comparison with the Serva genome showed that 35 open reading frames (ORFs) differed across the five genomes. Overall, 54 single nucleotide polymorphisms (SNPs) and 27 amino acid differences in 19 ORFs and two insertions in the UL52 and ORFC genes were identified. Similarity among the field strains and between the field and the vaccine strains ranged from 99.96% to 99.99%. Phylogenetic analysis revealed a close relationship among them, as well. This study generated data on genomic variation among Italian ILTV strains revealing that, even though the genetic variability of the genome is well conserved across time and between wild-type and vaccine strains, some mutations may help in differentiating among them and may be involved in ILTV virulence/attenuation. The results of this study can contribute to the understanding of the molecular bases of ILTV pathogenicity and provide genetic markers to differentiate between wild-type and vaccine strains.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Amino acids / Amino Acids - genetics / Base Sequence / Biology and Life Sciences / Causes of / Chickens / Comparative studies / Deoxyribonucleic acid / Development and progression / DNA / Eggs / Embryos / Epidemics / Evolution, Molecular / Food science / Gene sequencing / Genetic aspects / Genetic markers / Genetic variability / Genome, Viral / Genomes / Genomics / Herpes viruses / Herpesvirus 1, Gallid - genetics / Herpesviruses / Immunization / Infections / Infectious diseases / Laryngotracheitis / Medicine / Medicine and Health Sciences / Mutation / Nucleotide sequence / Nucleotides - genetics / Open reading frames / Open Reading Frames - genetics / Outbreaks / Pathogenicity / Pathogens / Phylogenetics / Phylogeny / Physiological aspects / Polymerase chain reaction / Poultry / Proteins / Research and Analysis Methods / Respiratory diseases / Sequence Analysis, DNA / Similarity / Single-nucleotide polymorphism / Strains (organisms) / Vaccines / Vaccines, Attenuated - immunology / Viral genetics / Viral infections / Virulence / Viruses