Homo sapiens Transcriptome or Gene expression

Tick-borne flaviviruses (TBFVs) are ss(+)RNA viruses that cause febrile illnesses, which may progress to severe encephalitis and/or death in humans globally. 30—60% of people who recover from severe acute disease continue to suffer debilitating neurological sequelae due to viral persistence, neurological cell damage incurred during infection and/or host response, or a combination of these. When TBFVs infect mammalian cells in vitro, an acute phase characterized by dramatic apoptosis ensues and kills >95% of infected cells by day 5. Upon refreshing the cell growth medium, surviving cells repopulate and become persistently infected for extended periods of time. However, molecular mechanisms responsible for the initiation and maintenance of viral persistence in vivo and in vitro remain vague. We used unbiased deep sequencing of the HEK 293T cell transcriptome to determine the profiles of acutely infected cells at selected time points as well as of persistently infected cells. Many genes were significantly differentially expressed during the course of the acute phase, but 451 genes were significantly differentially expressed uniquely in persistently infected cells. Ingenuity Pathways Analysis of these genes suggested that the oncogenes AKT2 and ERBB2, which favor cell survival were up-regulated in persistently infected cells, whereas pro-apoptotic genes, such as Bad and IFN-ß1 were down-regulated. There was also an up-regulation of genes encoding antiviral cytokines, such as CCL5, TNF-a and CXCL10 during the acute phase, but these were relatively suppressed in persistently infected cells. Exogenous induction of apoptosis in persistently infected cells with chelerythrine chloride indicated that these cells were resistant to apoptosis in a dose-dependent manner. In summary, the transcriptome profiles of acutely and persistently infected HEK 293T cells are different and evasion of apoptosis is critical for the initiation of TBFV persistence. These results provide a basis for further studying the precise molecular mechanisms of TBFV persistence.

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