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

PLoS One. 2016 Feb 18;11(2):e0149529. doi: 10.1371/journal.pone.0149529. eCollection 2016.

Abstract

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / genetics
  • Base Sequence
  • Evolution, Molecular
  • Genome, Viral*
  • Herpesvirus 1, Gallid / genetics*
  • Nucleotides / genetics
  • Open Reading Frames / genetics
  • Phylogeny
  • Sequence Analysis, DNA*
  • Vaccines, Attenuated / immunology*

Substances

  • Amino Acids
  • Nucleotides
  • Vaccines, Attenuated

Grants and funding

This work was funded by University of Padua (ex 60% 2009 and 2012, AP; “Progetto di Ateneo” PRAT CPDA138081/13, ST; “Assegno senior” and “Bando giovani studiosi”, GRIC13AAI9, EL) (http://www.unipd.it/), Istituto Zooprofilattico Sperimentale della Lombardia e dell’Emilia Romagna (Ricerca Corrente 2011 IZSLER, PRC2011005, AP, AM and PM) (http://www.izsler.it/), Regione Veneto (GP) (http://www.regione.veneto.it/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.