Location: Endemic Poultry Viral Diseases ResearchTitle: Attenuation, transmission, and immunogenicity of an ORF-C gene deleted strain of infectious laryngotracheitis virus (ILTV) in specific pathogen free chickens Author
Submitted to: American Association of Avian Pathologists
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2012
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Infectious laryngotracheitis (ILT) is a very serious and widespread respiratory disease of chickens caused by infectious laryngotracheitis virus (ILTV). Conventional attenuated ILT vaccines, obtained by continuous passages in chicken embryos and tissue culture, had been the main tools utilized by the poultry industry to control the disease. Unfortunately these vaccines have been demonstrated to revert to virulence after bird-to-bird passages.This emphasizes the need for the development of a genetically defined ILTV strain deficient in virulence factors as a safer alternative for ILT control. Recent full genome sequencing analysis performed in our laboratory revealed that a mutation that introduces a premature stop codon in the gene encoding ORF-C might be responsible for the attenuation phenotype of the tissue culture origin (TCO) vaccine. We have constructed a recombinant (delORF-C) containing deletion in ORF-C within a virulent background (USDA-ch). An initial study in specific-pathogen-free (SPF) chickens showed that the ORF-C deleted strain was significantly attenuated with respect to the induction of clinical signs and bird mortality. Therefore this ORF-C deficient strain of ILTV is an attractive vaccine candidate for the control of infectious laryngotracheitis. The first objective of this study is to determine the level attenuation and degree of transmission of the delORF-C strain after eye-drop vaccination of SPF chickens. The second objective is to evaluate the degree of protection induced by the delORF-C strain after challenge of SPF chickens with a virulent ILTV strain.