Efficacy of Live Virus Vaccines Against Infectious Laryngotracheitis Assessed by Polymerase Chain Reaction–Restriction Fragment Length Polymorphism

Abstract

The efficacy of four different commercial live vaccines (vaccines A, B, C, and D) against the infectious laryngotracheitis virus (ILTV) was assessed in specific-pathogen-free (SPF) chickens. SPF chickens were vaccinated intraocularly at 6 wk old with ILTV live vaccines and were challenged intratracheally with the N91B01 strain of virulent Korean ILTV 2 wk after vaccination. The immunity against ILTV live vaccines was assessed by the incidence of latent infection by the challenge virus in the chickens' tracheas and trigeminal ganglia, the reisolation rate of the challenge virus, and the clinical signs in the chickens challenged with the N91B01 strain of ILTV. The latent infection in chickens was assessed by nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Our data showed that the clinical signs and challenge virus isolation were negative in all chickens receiving four difference commercial ILTV live vaccines. The viral DNA of the vaccine strain, but not that of the challenge virus, was detected in chickens vaccinated with vaccine A by nested PCR-RFLP. The viral DNAs of both the vaccine and challenge strains were detected from chickens vaccinated with vaccines B, C, and D. This study showed that only vaccine A can protect chickens from latent infection with the field virulent ILTV. We speculate that the efficacy of infectious laryngotracheitis live vaccines to protect chickens from latent infection with virulent ILTVs can be assessed by nested PCR-RFLP analysis.

Evaluation of the protection elicited by direct and indirect exposure to live attenuated infectious laryngotracheitis virus vaccines against a recent challenge strain from the United States

“…In contrast to other challenge studies (Hilbink et al, 1987;Fulton et al, 2000;Han & Kim 2003), clinical signs and mortality were scored every day from day 2 to 12 d.p.c., in order to monitor the length of infection. The protection induced by CEO and TCO vaccines in vaccinated and challenged chickens was demonstrated by assessing clinical signs, mortality, body weight and shedding of the challenge virus to sentinel chickens.…”

“…These attenuated vaccines induce protection, preventing clinical signs and mortality (Gelenczei & Marty, 1964;Fulton et al, 2000;Han & Kim, 2003). Both types can persist in apparently healthy birds (Andreasen et al, 1989;Hughes et al, 1989) and can spread from vaccinated to unvaccinated birds in close contact (Gelenczei & Marty, 1964;Hilbink et al, 1987;Andreasen et al, 1989;Rodríguez-Avila et al, 2007).…”

“…The protection efficacy of live attenuated ILT vaccines has been evaluated against a variety of ILTV strains by clinical signs, mortality, viral recovery and spread (Gelenczei & Marty, 1964;Hilbink et al, 1987;Fulton et al, 2000;Han & Kim 2003). The objective of the present study was to evaluate the protection induced by direct and indirect exposure to these vaccines against a current group VI ILTV isolate.…”

Recombination in alphaherpesviruses

“…Avian alphaherpesvirus vaccines share the same risk. Indeed a virulent field isolate of infectious laryngo-tracheitis virus (gallid herpesvirus 1, GaHV-1) was found with a TK gene sequence similar to the sequence typically found in a virulent strain, whereas its glycoprotein G sequence was identical to that of the vaccine strain [107]. This highly virulent strain was suspected to be produced by in vivo recombination between virulent and vaccine strains of GaHV-1.…”

Detection of Wild- and Vaccine-Type Avian Infectious Laryngotracheitis Virus in Clinical Samples and Feather Shafts of Commercial Chickens

“…The restriction enzyme HaeIII was used to digest the PCR product obtained in the TKPD2 amplification (Table 1), as described [13]. Briefly, 20 U of HaeIII (New England Determination of the sensitivity of detection of ILTV by the TK gene nested PCR.…”