Al-Mubarak A, Zhou Y, Chowdhury S I
Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506, USA.
J Virol. 2004 May;78(9):4806-16. doi: 10.1128/jvi.78.9.4806-4816.2004.
The bovine herpesvirus 5 (BHV-5) gE ectodomain contains a glycine-rich epitope coding region (gE5 epitope), residues 204 to 218, that is significantly different from the corresponding gE region of BHV-1. Deletion of the gE epitope significantly reduced the neurovirulence of BHV-5 in rabbits. Pulse-chase analyses revealed that the epitope-deleted and wild-type gE were synthesized as N-glycosylated endoglycosidase H-sensitive precursors with approximate molecular masses of 85 kDa and 86 kDa, respectively. Like the wild-type gE, epitope-deleted gE complexed with gI and was readily transported from the endoplasmic reticulum. Concomitantly, the epitope-deleted and wild-type gE acquired posttranslational modifications in the Golgi leading to an increased apparent molecular mass of 93-kDa (epitope-deleted gE) and 94-kDa (wild-type gE). The kinetics of mutant and wild-type gE processing were similar, and both mature proteins were resistant to endoglycosidase H but sensitive to glycopeptidase F. The gE epitope-deleted BHV-5 formed wild-type-sized plaques in MDBK cells, and the epitope-deleted gE was expressed on the cell surface. However, rabbits infected intranasally with gE epitope-deleted BHV-5 did not develop seizures, and only 20% of the infected rabbits showed mild neurological signs. The epitope-deleted virus replicated efficiently in the olfactory epithelium. However, within the brains of these rabbits there was a 10- to 20-fold reduction in infected neurons compared with the number of infected neurons within the brains of rabbits infected with the gE5 epitope-reverted and wild-type BHV-5. In comparison, 70 to 80% of the rabbits exhibited severe neurological signs when infected with the gE5 epitope-reverted and wild-type BHV-5. These results indicated that anterograde transport of the gE epitope-deleted virus from the olfactory receptor neurons to the olfactory bulb is defective and that, within the central nervous system, the gE5 epitope-coding region was required for expression of the full virulence potential of BHV-5.
牛疱疹病毒5型（BHV - 5）的gE胞外结构域包含一个富含甘氨酸的表位编码区（gE5表位），位于第204至218位氨基酸残基，与BHV - 1的相应gE区域有显著差异。删除gE表位可显著降低BHV - 5对家兔的神经毒力。脉冲追踪分析显示，缺失表位的gE和野生型gE均作为N - 糖基化的内切糖苷酶H敏感前体合成，其近似分子量分别为85 kDa和86 kDa。与野生型gE一样，缺失表位的gE与gI形成复合物，并易于从内质网转运。同时，缺失表位的gE和野生型gE在高尔基体中进行翻译后修饰，导致表观分子量增加至93 kDa（缺失表位的gE）和94 kDa（野生型gE）。突变型和野生型gE的加工动力学相似，两种成熟蛋白对内切糖苷酶H有抗性，但对糖肽酶F敏感。缺失gE表位的BHV - 5在MDBK细胞中形成野生型大小的噬斑，且缺失表位的gE在细胞表面表达。然而，经鼻内感染缺失gE表位的BHV - 5的家兔未出现癫痫发作，只有20%的感染家兔表现出轻度神经症状。缺失表位的病毒在嗅上皮中高效复制。然而，与感染gE5表位回复型和野生型BHV - 5的家兔脑内感染神经元数量相比，这些家兔脑内的感染神经元数量减少了10至20倍。相比之下，70%至80%的家兔在感染gE5表位回复型和野生型BHV - 5时表现出严重神经症状。这些结果表明，缺失gE表位的病毒从嗅觉受体神经元向嗅球的顺行运输存在缺陷，并且在中枢神经系统内，gE5表位编码区是BHV - 5充分表达毒力潜能所必需的。
