Comparativein vivosafety and efficacy of a glycoprotein G-deficient candidate vaccine strain of infectious laryngotracheitis virus delivered via eye drop

Abstract

Infectious laryngotracheitis (ILT) is an acute respiratory disease in poultry that is commonly controlled by vaccination with conventionally attenuated virus strains. Despite the use of these vaccines, ILT remains a threat to the intensive poultry industry. Our laboratory has developed a novel candidate vaccine strain of infectious laryngotracheitis virus (ILTV) lacking glycoprotein G (ΔgG-ILTV). The aim of the present study was to directly compare this candidate vaccine with three currently available commercial vaccines in vivo. Five groups of specific-pathogen-free chickens were eye-drop inoculated with one of the three commercial vaccine strains (SA2-ILTV, A20-ILTV or Serva-ILTV), or ΔgG-ILTV, or sterile medium. Vaccine safety was assessed by examining clinical signs, weight gain and persistence of virus in the trachea. Vaccine efficacy was assessed by scoring clinical signs and conducting post-mortem analyses following challenge with virulent virus. Following vaccination, birds that received ΔgG-ILTV had the highest weight gain among the vaccinated groups and had clinical scores that were significantly lower than birds vaccinated with SA2-ILTV or A20-ILTV, but not significantly different from those of birds vaccinated with Serva-ILTV. Analysis of clinical scores, weight gain, tracheal pathology and virus replication after challenge revealed a comparable level of efficacy for all vaccines. Findings from this study further demonstrate the suitability of ΔgG-ILTV as a vaccine to control ILT.

Comparison of the replication and transmissibility of two infectious laryngotracheitis virus chicken embryo origin vaccines delivered via drinking water

“…Previous in vivo studies have shown significant variations in pathogenicity between different vaccine strains (Kirkpatrick et al, 2006a;Coppo et al, 2011). The findings from the present study provide evidence of differences in viral replication and transmission between vaccine strains.…”

Infectious Laryngotracheitis Virus Viral Chemokine-Binding Protein Glycoprotein G Alters Transcription of Key Inflammatory Mediators In Vitro and In Vivo

“…3A) but may explain the lower weight gain in chickens inoculated with ΔgG-ILTV ( Fig. 3B) than in the chickens described previously (17,18).…”

“…(12) and 21 days p.i. (18,20) in previous studies using the same commercial enzyme-linked immunosorbent assay (ELISA) kit, a finding that is likely related to the short time that elapsed between inoculation and sampling. Back titration of the inoculum revealed that birds in the ΔgG-ILTV group received 10 0.5 tissue culture infective dose (TCID 50 ) more virus than those in the ΔgGREV-ILTV group (see Materials and Methods).…”

“…The altered composition is consistent with both gG-mediated inhibition of heterophil chemotaxis (12) and increased titers of antibodies to wild-type (gG-expressing) ILTV in serum. The lack of gG modifies the local inflammatory environment at the airway epithelium during acute ILTV infection, reducing the pathogenic effects of the virus while still enabling the development of a protective immune response (7,12,(17)(18)(19)(20).…”

Development and application of a TaqMan single nucleotide polymorphism genotyping assay to study infectious laryngotracheitis virus recombination in the natural host

“…different doses of virus and different times between inoculation of each virus) and also studies to assess how ILTV vaccines may be used to limit recombination. Although ILTV vaccines help to prevent disease they do not fully prevent infection or viral replication following challenge [30]. As alphaherpesvirus recombination is closely associated with replication [15] this means there is the potential for ILTV recombination to occur in vaccinated birds.…”