Attenuation of bovine herpesvirus type 1 by deletion of its glycoprotein G and tk genes and protection against virulent viral challenge
2011
Zhang, Minmin | Fu, Shulin | Deng, Mingliang | Xie, Qian | Xu, Haiyang | Liu, Zhengfei | Hu, Changmin | Chen, Huanchun | Guo, Aizhen
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.
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