Abstract
Background: Infectious laryngotracheitis (ILT) is a highly contagious acute respiratory disease of chickens. Antigenic mutation of infectious laryngotracheitis virus (ILTV) may result in a vaccination failure in the poultry industry and thus a protective vaccine against predominant ILTV strains is highly desirable. Methods: The full-length glycoprotein B (gB) gene of ILTV with the two mutated synonymous sites of fowlpox virus (FPV) transcription termination signal sequence was cloned into the insertion vector p12LS, which was co-transfected with wild-type (wt) FPV into chicken embryo fibroblast (CEF) to develop a recombinant fowlpox virus-gB (rFPV-gB) candidate vaccine strain. Furthermore, its biological and immunological characteristics were evaluated. Results: The results indicated that gB gene was expressed correctly in the rFPV by indirect immunofluorescent assay and Western blot, and the rFPV-gB provided a 100% protection in immunized chickens against the challenge of predominant ILTV strains that were screened by pathogenicity assay when compared with the commercialized rFPV vaccine, which only provided 83.3%. Conclusion: rFPV-gB can be used as a potential vaccine against predominant ILTV strains.
Highlights
Infectious laryngotracheitis (ILT) is a highly contagious acute respiratory disease in chickens.Infectious laryngotracheitis virus (ILTV), classified as Gallid herpesvirus I, is a key pathogen, which has the characteristics of rapid spread, high mortality, and low egg production rates in infected laying hens [1]
The results showed that the titer of the glycoprotein B (gB) antibody induced by recombinant fowlpox virus-gB (rFPV-gB) at 7 and 14 days postinfection (d.p.i) was significantly higher than that of crFPV, and there was no difference between them at2020, 21 d.p.i
According to Agnew-Crumpton’s and Choi’s classification method [10,26,27], the results showed that predominant wild infectious laryngotracheitis virus (ILTV) strains were close to class 8 by phylogenetic analysis of thymidine kinase (TK), Infected cell protein 4 (ICP4), ORFB-TK, and the gB gene, while WG strain belonged to class 4 (Table 1), which indicated that the update of the vaccine was necessary because the ILTV virus was constantly evolving
Summary
Infectious laryngotracheitis virus (ILTV), classified as Gallid herpesvirus I, is a key pathogen, which has the characteristics of rapid spread, high mortality, and low egg production rates in infected laying hens [1]. It is becoming an enzootic in China [2,3,4,5]. Results: The results indicated that gB gene was expressed correctly in the rFPV by indirect immunofluorescent assay and Western blot, and the rFPV-gB provided a 100% protection in immunized chickens against the challenge of predominant ILTV strains that were screened by pathogenicity assay when compared with the commercialized rFPV vaccine, which only provided 83.3%. Conclusion: rFPV-gB can be used as a potential vaccine against predominant ILTV strains
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