Boycott R, Klenk H D, Ohuchi M
Institut für Virologie, Philipps-Universität Marburg, Germany.
Virology. 1994 Sep;203(2):313-9. doi: 10.1006/viro.1994.1489.
When influenza virus A/WSN/33 (H1N1) was grown in MDBK or CV-1 cells in serum-free medium, progeny virus released from these cells contained only uncleaved hemagglutinin (HA). This virus was unable to infect CV-1 cells unless subjected to cleavage activation by trypsin, but it was infectious for MDBK cells without such treatment. Temperature shift experiments demonstrated that HA of radiolabeled input virus was cleaved within 30 min after inoculation of MDBK cells. As indicated by its resistance to trypsin cleavage, the virus was already internalized at this stage. Cleavage was not observed after inoculation of CV-1 cells. The serine-protease inhibitor leupeptin blocked virus growth when added to MDBK cells during the initial phase of the replication cycle. The inhibitor did not show this effect, when the input virus contained already cleaved HA. These results demonstrate that activation of HA of the WSN strain can occur in MDBK cells, but not in CV-1 cells, at the stage of virus entry, presumably by an endosomal protease.
当甲型流感病毒A/WSN/33（H1N1）在无血清培养基中的MDBK或CV-1细胞中培养时，从这些细胞释放的子代病毒仅含有未裂解的血凝素（HA）。这种病毒除非经过胰蛋白酶裂解激活，否则无法感染CV-1细胞，但未经此类处理时对MDBK细胞具有感染性。温度转换实验表明，放射性标记的输入病毒的HA在接种MDBK细胞后30分钟内被裂解。从其对胰蛋白酶裂解的抗性可以看出，此时病毒已经内化。接种CV-1细胞后未观察到裂解现象。丝氨酸蛋白酶抑制剂亮肽素在复制周期初始阶段添加到MDBK细胞中时会阻断病毒生长。当输入病毒已经含有裂解的HA时，该抑制剂没有显示出这种效果。这些结果表明，WSN株的HA激活可能在内体蛋白酶作用下，于病毒进入阶段在MDBK细胞中发生，但在CV-1细胞中不会发生。
