Haflidadóttir Benedikta S, Matthíasdóttir Sigrídur, Agnarsdóttir Gudrún, Torsteinsdóttir Sigurbjorg, Pétursson Gudmundur, Andrésson Ólafur S, Andrésdóttir Valgerdur
Institute for Experimental Pathology, University of Iceland, Keldur, Reykjavík, Iceland.
J Gen Virol. 2008 Mar;89(Pt 3):716-721. doi: 10.1099/vir.0.83410-0.
We have shown previously that a type-specific neutralization domain is located within a 39 aa sequence in the fourth variable domain of gp135 in visna/maedi virus. We now show that neutralizing antibodies detected early in infection are directed to this epitope, suggesting an immunodominant nature of this domain. Ten antigenic variants were previously analysed for mutations in this region, and all but one were found to be mutated. To assess the importance of these mutations in replication and neutralization, we reconstructed several of the mutations in an infectious molecular clone and tested the resulting viruses for neutralization phenotype and replication. Mutation of a conserved cysteine was shown to alter the neutralization epitope, whilst the replication kinetics in macrophages were unchanged. Mutations modulating potential glycosylation sites were found in seven of the ten antigenic variants. A frequently occurring mutation, removing a potential glycosylation site, had no effect on its own on the neutralization phenotype of the virus. However, adding an extra potential glycosylation site in the region resulted in antigenic escape. The results indicate that the conserved cysteine plays a role in the structure of the epitope and that glycosylation may shield the principal neutralization site.
我们之前已经表明，在维斯纳/梅迪病毒的gp135第四可变域的39个氨基酸序列内存在一个型特异性中和结构域。我们现在表明，感染早期检测到的中和抗体指向该表位，表明该结构域具有免疫显性性质。之前对10个抗原变体进行了该区域突变分析，发现除一个外其余均发生了突变。为了评估这些突变在复制和中和中的重要性，我们在一个感染性分子克隆中重建了其中一些突变，并对产生的病毒进行了中和表型和复制测试。结果表明，一个保守半胱氨酸的突变会改变中和表位，而在巨噬细胞中的复制动力学不变。在10个抗原变体中的7个中发现了调节潜在糖基化位点的突变。一个常见的突变，去除了一个潜在的糖基化位点，其本身对病毒的中和表型没有影响。然而，在该区域添加一个额外的潜在糖基化位点会导致抗原逃逸。结果表明，保守半胱氨酸在表位结构中起作用，糖基化可能会屏蔽主要中和位点。
