@article{mbs:/content/journal/jgv/10.1099/jgv.0.000521, author = "Garcia, Maricarmen and Spatz, S. J. and Cheng, Y. and Riblet, S. M. and Volkening, J. D. and Schneiders, G. H.", title = "Attenuation and protection efficacy of ORF C gene-deleted recombinant of infectious laryngotracheitis virus", journal= "Journal of General Virology", year = "2016", volume = "97", number = "9", pages = "2352-2362", doi = "https://doi.org/10.1099/jgv.0.000521", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/jgv.0.000521", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", keywords = "Infectious laryngotracheitis virus (ILTV)", keywords = "Open reading frame (ORF C)", keywords = "Attenuation", abstract = "Infectious laryngotracheitis (ILT) is a highly contagious respiratory disease of chickens caused by infectious laryngotracheitis virus (ILTV). The disease is controlled by the use of live-attenuated vaccines. Previously we reported the complete nucleotide sequence of the ILTV vaccine strain (TCO) and identified a nonsense mutation in the gene encoding the ORF C protein. This suggested that the ORF C protein might be associated with viral virulence. To investigate this, an ILTV recombinant with a deletion in the gene encoding ORF C was constructed using the genome of the virulent United States Department of Agriculture (USDA) challenge strain (USDAch). Compared to the parental virus, the ΔORF C recombinant replicated in chicken kidney (CK) cells with similar kinetics and generated similar titres. This demonstrated that the ORF C deletion had no deleterious effects on replication efficacy in vitro. In chickens, the recombinant induced only minor microscopic tracheal lesions when inoculated via the intra-tracheal/ocular route, while the parental strain induced moderate to severe microscopic tracheal lesions, even though virus load in the tracheas were comparable. Groups of chickens vaccinated via eye-drop with the ∆ORFC-ILTV were protected to levels comparable to those elicited by TCO vaccination. To our knowledge, this is the first report that demonstrates the suitability of ∆ORFC as a live-attenuated vaccine to prevent the losses caused by ILTV.", }