Cellular changes attending mengovirus-induced cytolysis of mouse L-cells

Poliovirus infection of established human blood cell lines: relationship between the differentiation stage and susceptibility of cell killing

The replication of type 1 poliovirus in 13 established human blood cell lines differing in the differentiation stage and cell lineage was investigated. Three T (CCRF-CEM, CCRF-HSB-2, and Molt-3) and three B (Raji, CCRF-SB, and RPMI 8226) cell lines showed no cytopathic effects (CPE) or virus production. CPE associated with virus production were detected in the other seven cell lines: HL-60, ML-1, and KG-1 (granulocytic lineage), U-937 and THP-1 (monocytic lineage), K-562 (erythroid lineage), and Molt-4 (T cell lineage). These susceptible cell lines greatly differed in the speed at which the CPE progressed. The progression of CPE was faster in relatively well-differentiated cell lines such as HL-60 and U-937, independently of the multiplicity of infection, than in less differentiated cell lines such as K-562, KG-1, and THP-1. Thus, for the same lineage, the speed at which CPE progressed became proportionally higher with subsequent differentiation stages. In the K-562 cell culture, CPE were not observed until at least 5 days postinfection (p.i.), while more than 80% of HL-60 cells were killed within 3 days p.i. There were no significant differences between infected HL-60 and K-562 cells in the efficiency of infection determined at 8 hr p.i. by the indirect immunofluorescent technique, the rate of virus growth, or the amount of viral capsid protein synthesized. This indicated that there were similar viral replication cycles in the two cell lines. These observations suggest that the killing function of the virus is expressed more slowly in K-562 cells than in HL-60 cells.

Influence of poliovirus infection on S-phase and mitosis of the host cell

Hep-2 cells were synchronized by a double thymidine block and infected with poliovirus type I (Mahoney) in hourly intervals after release from the second thymidine block. The S-phase is not prevented by a poliovirus infection but, with cells infected 0-4 hours after release, an increase of its duration is found. With an infection 5 hours and later after release, the duration of the S-phase is not different from that of an uninfected, synchronized control culture. DNA synthesis itself is slower early in S-phase and gets inhibited up to 75 per cent late in S-phase. All cultures show the first signs of a CPE 3.5 hours p.i. and, in spite of CPE, the cells continue to synthesize DNA. In infected cells a slightly higher peak of mitotic cells compared to control cultures is found. The time point of the mitotic peak is dependant of the time of infection and seems no longer controlled by the cell cycle. The mitotic indices are similar for all cultures infected at different times after release. When the cells are infected early after release CPE appears before mitosis and prevents the cells from entering mitosis. Cells which are infected towards the end of the S-phase finish mitosis normally before they exhibit characteristics of CPE. Extent and kinetics of poliovirus RNA synthesis and yield of virus progeny are not altered by the cell cycle.

Effects of actinomycin D on the cytopathology induced by poliovirus in HEp-2 cells

One possible mechanism of virus-induced cell damage is that the redistributed (released) lysosomal enzymes produce the cytopathic effect during cytolytic types of infections such as poliovirus in HEp-2 cells. To determine if the lysosomal enzyme redistribution and cell damage are host-cell directed, we studied sensitivity of these events to the action of actinomycin D. By the use of actinomycin D at concentrations producing the least toxicity but maximal effectiveness in shuting down cell RNA synthesis, it was shown that the cytopathic effect and enzyme redistribution were not inhibited and, therefore, not directly controlled and induced by the cell genome in response to the virus infection. Evaluation of cytopathic effect by a phase contrast microscopy method detected changes earlier than the erythrocin B uptake method.

Virus replication, cytopathology, and lysosomal enzyme response of mitotic and interphase Hep-2 cells infected with poliovirus

Mitotic Hep-2 cells, selected by the PEL (colloidal silica) density gradient method and held in mitosis with Colcemid, are readily infected by poliovirus type I (Mahoney). They produce and release the same amount of virus as interphase, random-growing cells. In contrast to interphase cells, mitotic cells show no detectable virus-induced cytopathic effect at the light microscopy level and only slight alterations, consisting of small clusters of vacuoles, at the electron microscopy level. Mitotic cells contain the same total amount of lysosomal enzymes per cell as interphase cells, but they display no redistribution of lysosomal enzymes during the virus infection as interphase cells do. This supports the view that lysosomal enzyme redistribution is associated with the cytopathic effect in poliovirus infection but shows that virus synthesis and release is not dependent on either the cytopathic effect or lysosomal enzyme release. The possible reasons for the lack of cytopathic effect in mitotic cells are discussed.