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Attenuation and protection efficacy of open reading frame C (ORF C) gene deleted recombinant of infectious laryngotracheitis virus (ILTV).

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García M, Spatz SJ, Cheng Y, Riblet SM, Volkening JD, Schneiders GH,


García M, Spatz SJ, Cheng Y, Riblet SM, Volkening JD, Schneiders GH, (click to view)

García M, Spatz SJ, Cheng Y, Riblet SM, Volkening JD, Schneiders GH,

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The Journal of general virology 2016 6 09() doi 10.1099/jgv.0.000521

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 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 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 titers. 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.

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