Schneider P A, Hatalski C G, Lewis A J, Lipkin W I
Department of Microbiology and Molecular Genetics, University of California-Irvine, 92697-4290, USA.
J Virol. 1997 Jan;71(1):331-6. doi: 10.1128/JVI.71.1.331-336.1997.
The Borna disease virus (BDV) antigenome is comprised of five major open reading frames (ORFs). Products have been reported only for ORFs I, II, and III, encoding N (p40), P (p24/p23), and M (gp18), respectively. ORF IV predicts a 57-kDa protein with several potential glycosylation sites. Analysis of radiolabeled extracts from BDV-infected C6 cells and BHK-21 cells transfected with a Semliki Forest virus vector that contains ORF IV demonstrated the presence of a 94-kDa protein (G protein) which was sensitive to tunicamycin, endoglycosidase F/N-glycosidase, and endoglycosidase H but not to O-glycosidase. Sera from BDV-infected rats detected the G protein and had neutralization activity that was reduced following immunoadsorption with the G protein. Preincubation of cells with the G protein interfered with BDV infectivity. This effect was enhanced by treatment of the G protein with the exoglycosidase alpha-mannosidase and reduced after subsequent treatment with N-acetyl-beta-D-glucosaminidase. In concert these findings indicate that ORF IV encodes a 94-kDa N-linked glycoprotein with extensive high mannose- and/or hybrid-type oligosaccharide modifications. The presence of neutralization epitopes on the G protein and its capacity to interfere with infectivity suggest that the G protein is important for viral entry.
博尔纳病病毒（BDV）反基因组由五个主要开放阅读框（ORF）组成。目前仅报道了ORF I、II和III的产物，分别编码N（p40）、P（p24/p23）和M（gp18）。ORF IV预测有一个含有多个潜在糖基化位点的57 kDa蛋白。对感染BDV的C6细胞和用含有ORF IV的辛德毕斯病毒载体转染的BHK - 21细胞的放射性标记提取物进行分析，结果显示存在一种对衣霉素、内切糖苷酶F/N - 糖苷酶和内切糖苷酶H敏感但对O - 糖苷酶不敏感的94 kDa蛋白（G蛋白）。来自感染BDV大鼠的血清可检测到G蛋白，并且具有中和活性，在用G蛋白进行免疫吸附后中和活性降低。用G蛋白对细胞进行预孵育会干扰BDV的感染性。用外切糖苷酶α - 甘露糖苷酶处理G蛋白可增强这种效应，而随后用N - 乙酰 - β - D - 氨基葡萄糖苷酶处理后效应减弱。这些研究结果一致表明，ORF IV编码一种94 kDa的N - 连接糖蛋白，具有广泛的高甘露糖型和/或杂合型寡糖修饰。G蛋白上存在中和表位及其干扰感染性的能力表明，G蛋白对于病毒进入至关重要。
