Protection of chickens from infectious laryngotracheitis with a recombinant fowlpox virus expressing glycoprotein B of infectious laryngotracheitis virus

Infectious laryngotracheitis (ILT) is an economically important disease of chickens caused by a type I gallid herpesvirus, infectious laryngotracheiti s virus (ILTV). The vaccines currently available are modified live viruses, which are effective in preventing disease outbreaks. However, they have of ten been associated with a variety of adverse effects including spread of v accine virus to non-vaccinates, inadequate attenuation, production of laten tly infected carriers, and increased virulence as a result of in vivo passa ge. In this study, a recombinant fowlpox virus expressing glycoprotein B (g B) of ILTV (rFPV-ILTVgB) was constructed. Protection of specific pathogen f ree (SPF) and commercial chickens from ILT with the rFPV-ILTVgB and commerc ial ILTV vaccine (Nobilis ILT) were compared after challenge with a lethal dose of virulent ILTV. Both the rFPV-ILTVgB- and the Nobilis ILT-vaccinated SPF chickens were completely protected from death, while 90% of the unvacc inated chickens died after challenge. The immunized commercial chickens wer e also 100% protected with rFPV-ILTVgB, compared with 85% protected with No bilis ILT. The protective efficacy was also measured by the antibody respon se to ILTV gB, isolation of challenge virus and polymerase chain reaction a mplification of the ILTV thymidine kinase gene after challenge. The results showed that rFPV-ILTVgB could be a potential safe vaccine to replace curre nt modified live vaccines for preventing ILT.