Huso D L, Narayan O, Hart G W
Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
J Virol. 1988 Jun;62(6):1974-80. doi: 10.1128/JVI.62.6.1974-1980.1988.
The lentivirus caprine arthritis-encephalitis virus (CAEV) is a pathogen of goats. It is transmitted in milk and causes a persistent infection in goats, which often fail to produce neutralizing antibodies to the virus. Native CAEV particles are remarkably resistant to digestion with proteinase K and are neutralized extremely slowly by immune sera. Our studies showed that the virus particles are heavily sialylated. Studies with highly specific sialyltransferase enzymes identified penultimate carbohydrate linkages typical of O- and N-linked oligosaccharides on the virus and suggested that the virus may be more heavily sialylated on O-linked than on N-linked oligosaccharides. Removal of sialic acids from the virus by neuraminidase treatment did not reduce infectivity of the particles. However, desialylation rendered the virus more susceptible to proteolysis by proteinase K. Desialylation also enhanced the kinetics of neutralization of the virus by goat antibodies. These results suggest that the carbohydrates on the viral surface are important both in protecting viral proteins from digestion by proteases and in protecting the virus from rapid neutralization by antibodies.
慢病毒山羊关节炎-脑炎病毒（CAEV）是山羊的一种病原体。它通过乳汁传播，在山羊体内引发持续感染，山羊通常无法产生针对该病毒的中和抗体。天然CAEV颗粒对蛋白酶K消化具有显著抗性，且被免疫血清中和的速度极慢。我们的研究表明，病毒颗粒高度唾液酸化。使用高度特异性唾液酸转移酶进行的研究确定了病毒上典型的O-连接和N-连接寡糖的倒数第二个碳水化合物连接，并表明病毒在O-连接寡糖上的唾液酸化程度可能比在N-连接寡糖上更高。用神经氨酸酶处理去除病毒上的唾液酸并不会降低颗粒的感染性。然而，去唾液酸化使病毒更容易被蛋白酶K蛋白水解。去唾液酸化还增强了山羊抗体对病毒的中和动力学。这些结果表明，病毒表面的碳水化合物在保护病毒蛋白免受蛋白酶消化以及保护病毒免受抗体快速中和方面都很重要。
