Expression of cellular oncogene Bcl-xL prevents coronavirus-induced cell death and converts acute infection to persistent infection in progenitor rat oligodendrocytes

Murine coronavirus mouse hepatitis virus (MHV) causes persistent infection of the central nervous system (CNS) in rodents, which has been associated with demyelination. However, the precise mechanism of MHV persistence in the CNS remains elusive. Here we show that the progenitor oligodendrocytes (central glial 4 [CG-4] cells) derived from newborn rat brain were permissive to MHV infection, which resulted in cell death, although viral replication was restricted. Interestingly, treatment with fetal bovine serum or exogenous expression of cellular oncogene Bcl-xL prevented CG-4 cells from MHV-induced cell death. Significantly, overexpression of Bcl-xL alone was sufficient to convert acute to persistent, nonproductive infection in CG-4 cells. This finding indicates that intracellular factors rather than viral components play a critical role in establishing viral persistence in CNS cells. Although viral genomic RNAs continuously persisted in Bcl-xL-expressing CG-4 cells over 10 passages, infectious virus could no longer be isolated beyond 2 passages of the cell. Such a phenomenon resembles the persistent MHV infection in animal CNS. Thus, the establishment of a persistent, nonproductive infection in CG-4 cells may provide a useful in vitro model for studying viral persistence in animal CNS. The data also suggest that direct virus-host cell interaction is one of the underlying mechanisms that regulate viral persistence in CNS cells.