Submitted to: Workshop on Molecular Pathogenesis of Marek's Disease and Avian Immunology
Publication Type: Proceedings
Publication Acceptance Date: 8/25/2010
Publication Date: 9/17/2010
Citation: Spatz, S.J., Afonso, C.L., Zsak, L., Garcia, M., Mundt, E., Riblet, S., Keeler, C., Rock, D. 2010. Comparative nucleotide sequence analysis of three virulent strains of infectious laryngotracheitis virus. Workshop on Molecular Pathogenesis of Marek's Disease and Avian Immunology. 1(1): 59. Interpretive Summary:
Technical Abstract: Infectious laryngotracheitis is a very serious and widespread respiratory disease of chickens caused by gallid herpesvirus type 1, commonly named infectious laryngotracheitis virus. For protection from infectious laryngotracheitis, chickens have traditionally been vaccinated with live-attenuated strains that have been attenuated by either multiple passages in embryonated eggs (chicken embryo origin) or in tissue culture (tissue culture origin). Once a vaccine strain has been introduced in the field, the differentiation between vaccines and virulent strains is difficult due to antigenic and genetic homogeneity that exists between vaccines and virulent field isolates. Safeguarding the poultry industry against virulent infectious laryngotracheitis virus strains remains one of the industry's greatest challenges - the disease is primarily considered to have been restrained rather than well controlled. To investigate the genetic diversity of infectious laryngotracheitis virus strains we have determined the nucleotide sequences of three virulent strains: the United States Department of Agriculture reference strain (genotype I), the genotype V strain and the genotype VI strain, using three different sequencing technologies. The reference strain was sequenced from restriction endonuclease fragment libraries using dideoxynucleotide sequencing. The genotype V and VI strains were sequenced using the next generation technologies 454 pyrosequencing and solid sequencing, respectively. Each sequence was compared to the only infectious laryngotracheitis virus sequence present within GenBank. The lengths of more than 30 open reading frames differ among the newly sequenced genomes and that of the sequence in GenBank. This is not surprising since the GenBank sequence represents a composite or "patchwork" of sequencing data from different strains. However, a strong correlation in open reading frame length of 70% exists between the newly sequenced genomes relative to the GenBank sequence. A comprehensive analysis of these genomes relative to partial sequences of the vaccine strain (chicken embryo origin) will be presented.