Piirainen L, Airaksinen A, Hovi T, Roivainen M
Enterovirus Laboratory, National Public Health Institute, Helsinki, Finland.
Arch Virol. 1996;141(6):1011-20. doi: 10.1007/BF01718605.
A large proportion of host cell-bound virions of poliovirus type 1 strain Mahoney (PV1/M) is known to elute to the culture medium during incubation at 37 degrees C, and only a fraction of the virions remaining cell-associated will successfully uncoat and contribute to the new replication cycle. We found that while the proportion of inoculum type 3 poliovirus strain Saukett (PV3/S) bound to GMK cells was of the same order as that of PV1/M, the bound PV3/S virions uncoated much less efficiently, as judged by velocity sedimentation analysis of virion disintegration. Rather, the majority of the cell-associated PV3/S viruses remained apparently unaffected for several hours within an unidentified intracellular compartment. Incubation of PV3/S with intestinal trypsin is known to result in selective cleavage of the capsid protein VP1 and striking antigenic changes. Trypsin treatment of stock PV3/S preparations did not affect the infectivity titre or modify single-cycle progeny virus yields significantly. However, the fate of the cell-bound inoculum virus was profoundly altered. Trypsin-treated PV3/S virions (PV3/S-Try) attached to GMK cells less tightly than the untreated PV3/S virus or PV1/M, and a relatively larger proportion of the cell-bound virus eluted to the medium during subsequent incubation at 36 degrees C. However, the fraction of virions remaining cell-associated rapidly disintegrated suggesting efficient uncoating. In accordance with these observations, one step growth curves of PV3/S-Try in all cell lines tested showed lowered eclipse phase titres compared to those obtained with the untreated PV3/S inocula. Similar effects were also demonstrated for type 3 poliovirus strain Sabin while trypsin-sensitive strains of the other two serotypes of poliovirus remained unaffected in this sense. The putative biological significance of the altered sorting of cell-bound PV3/S-Try virions is not known. It might be related to the observations that sensitivity of type 3 poliovirus strains to trypsin is conserved in spite of the fact that the target site of trypsin action is flanked by highly variable motives in an immunodominant antigenic site.
已知1型脊髓灰质炎病毒Mahoney株（PV1/M）与宿主细胞结合的大量病毒粒子在37℃孵育期间会洗脱到培养基中，只有一小部分仍与细胞相关的病毒粒子会成功脱壳并进入新的复制周期。我们发现，虽然3型脊髓灰质炎病毒Saukett株（PV3/S）与GMK细胞结合的接种物比例与PV1/M相同，但通过病毒粒子解体的速度沉降分析判断，结合的PV3/S病毒粒子脱壳效率要低得多。相反，大多数与细胞相关的PV3/S病毒在一个未明确的细胞内区室中数小时内显然未受影响。已知用肠胰蛋白酶孵育PV3/S会导致衣壳蛋白VP1的选择性裂解和显著的抗原变化。用胰蛋白酶处理储备的PV3/S制剂不会影响感染性滴度，也不会显著改变单周期子代病毒产量。然而，与细胞结合的接种病毒的命运发生了深刻改变。经胰蛋白酶处理的PV3/S病毒粒子（PV3/S-Try）与GMK细胞的结合不如未处理的PV3/S病毒或PV1/M紧密，并且在随后36℃孵育期间，相对较大比例的与细胞结合的病毒洗脱到培养基中。然而，仍与细胞相关的病毒粒子部分迅速解体，表明脱壳效率高。根据这些观察结果，与未处理的PV3/S接种物相比，在所有测试细胞系中PV3/S-Try的一步生长曲线显示出更低的隐蔽期滴度。对于3型脊髓灰质炎病毒Sabin株也显示出类似的效果，而其他两种血清型脊髓灰质炎病毒的胰蛋白酶敏感株在这方面未受影响。与细胞结合的PV3/S-Try病毒粒子分选改变的假定生物学意义尚不清楚。这可能与以下观察结果有关：尽管胰蛋白酶作用的靶位点两侧是免疫显性抗原位点中高度可变的基序，但3型脊髓灰质炎病毒株对胰蛋白酶的敏感性是保守的。
