Long-term Infection and Shedding of Human Cytomegalovirus in T98G Glioblastoma Cells

Human cytomegalovirus (HCMV) is the leading viral cause of birth defects, affecting primarily the central nervous system (CNS). To further understand this CNS pathology, cells from glioblastoma cell lines T98G and A172, the astrocytic glioblastoma cell line CCF-STTG1 (CCF), and the neuroblastoma cell line SH-SY5Y (SY5Y) were infected with HCMV. CCF and SY5Y cells were fully permissive for infection, while A172 cells were nonpermissive. In T98G cells, the majority of cells showed viral deposition into the nucleus by 6 h postinfection (hpi); however, viral immediate-early gene expression was observed in only approximately 30% of cells in the first 72 h. In viral antigen (Ag)-positive cells, although the development of complete viral replication centers was delayed, fully developed centers formed by 96 hpi. Interestingly, even at very late times postinfection, a mixture of multiple small, bipolar, and large foci was always present. The initial trafficking of input pp65 into the nucleus was also delayed. Titer and infectious-center assays showed a small number of T98G cells shedding virus at very low levels. Surprisingly, both Ag-positive and Ag-negative cells continued to divide; because of this continuous division, we adopted a protocol for passaging the T98G cells every third day to prevent overcrowding. Under this protocol, detectable infectious-virus shedding continued until passage 5 and viral gene expression continued through eight passages. This evidence points to T98G cells as a promising model for long-term infections.