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Attenuation of bovine herpesvirus type 1 by deletion of its glycoprotein G and tk genes and protection against virulent viral challenge

Zhang, Minmin, Fu, Shulin, Deng, Mingliang, Xie, Qian, Xu, Haiyang, Liu, Zhengfei, Hu, Changmin, Chen, Huanchun, Guo, Aizhen
Vaccine 2011 v.29 no.48 pp. 8943-8950
Bovine herpesvirus 1, blood serum, calves, dexamethasone, genes, glycoproteins, homologous recombination, immunization, infectious bovine rhinotracheitis, interferon-beta, interferon-gamma, mutants, neutralization, neutralizing antibodies, thymidine kinase, tumor necrosis factor-alpha, vaccines, virulence, viruses
To develop a novel vaccine against infectious bovine rhinotracheitis (IBR), a bovine herpesvirus-1 (BoHV-1) mutant was constructed by deleting the genes for glycoprotein G (gG) and thymidine kinase (tk) through homologous recombination. The resulting sequences for both genes were shown to be correct and a gG expression defect was also confirmed. A parallel study of the BoHV-1 gG⁻/tk⁻, gE⁻/tk⁻ mutants and wild type (wt) in 31 calves was performed at three different doses, 4×10⁵PFU, 4×10⁶PFU and 4×10⁷PFU. Compared to wt BoHV-1, inoculation of BoHV-1 gG⁻/tk⁻ and gE⁻/tk⁻ produced no clinical signs and the virus was not reactivated by dexamethasone (dex). Inoculation of BoHV-1 gG⁻/tk⁻ at the doses of 4×10⁶ and 4×10⁷PFU provided full clinical protection for the cattle against wt BoHV-1 challenge at 4×10⁷PFU/calf. Although the mutants were associated with significantly lower levels of serum neutralizing antibody, interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) than wt BoHV-1 on days 3, 5 and 7 after immunization, stimulation of IFN-β by BoHV-1 gG⁻/tk⁻ was significantly higher than that of wt BoHV-1 and gE⁻/tk⁻ on days 3 and 5. We conclude that BoHV-1 gG⁻/tk⁻ was attenuated adequately and that it maintains the ability to stimulate immune protection. Therefore, it may be a promising candidate for a marker vaccine against IBR.