Fig 4.

Human astrocytoma cell line CCF-STTG1 supports persistent CVB3 infection. (A) Impact of CVB3 persistent infection on viability of CCF-STTG1 cells. Equal numbers of cells persistently infected for the indicated times p.i. and mock-infected cells were seeded in 96-well plates. Relative cell viability was measured with a Cell Counting Kit-8 using the corresponding uninfected cells (mock) as controls (for which viability was set equal to 100%). The results are presented as the means ± standard deviations of triplicate measurements. (B) Persistence of both positive- and negative-strand CVB3 RNA in CCF-STTG1 cells. The levels of viral RNA replication dynamics of both positive and negative polarity were determined in persistently infected CCF-STTG1 cells by strand-specific real-time PCR. The results are presented as the means ± standard deviations of triplicate measurements. (C) Detection of viral antigen (green) and GFAP (red) in CCF-STTG1 cells persistently infected with CVB3 by IFA. Cell nuclei (blue) were counterstained with Hoechst 33258. Bars, 10 μm. The results of one representative experiment out of three are shown. (D) CCF-STTG1 cells persistently infected with CVB3 showed continuous detectable levels of infectious virus progeny ranging from 10^4.8 to 10^6.6 TCID₅₀s/ml. Means and standard deviations of three independent experiments are shown. (E) The percentage of CVB3-infected CCF-STTG1 cells was determined by both IFA and IC assay at the indicated times p.i. The results are presented as the means ± standard deviations of triplicate measurements.