Gamma Interferon-Dependent, Noncytolytic Clearance of Sindbis Virus Infection from Neurons In Vitro

Due to the nonrenewable nature of neurons, recovery from viral infection of the central nervous system requires noncytopathic mechanisms for control of virus replication. Recovery from alphavirus encephalitis can occur without apparent neurological damage through the effects of antibody and gamma interferon (IFN-gamma). To establish an in vitro cell culture system that will allow the study of mechanisms of IFN-gamma-mediated control of Sindbis virus (SINV) replication in neurons, we have characterized the susceptibility to SINV infection and IFN-gamma responsiveness of two neuronal cell lines that can be differentiated in vitro: CSM14.1, a rat nigral cell line, and NSC34, a mouse motor neuron cell line. Undifferentiated CSM14.1 and NSC34 cells were permissive for SINV and susceptible to virus-induced cell death. With differentiation, CSM14.1 cells reduced virus replication and became progressively resistant to virus-induced cell death, resulting in prolonged virus replication. NSC34 cells did not differentiate completely and became only partially resistant to SINV infection. Both CSM14.1 and NSC34 cells responded to pretreatment with IFN-gamma by decreasing SINV replication. Differentiated CSM14.1 cells treated 24 h after infection with IFN-gamma responded with increased cell viability and clearance of infectious virus. IFN-gamma treatment sequentially altered the ratio of genomic to subgenomic viral RNA synthesis, promoted recovery of cellular protein synthesis, reduced viral protein synthesis, and inhibited viral RNA transcription within 24 h after treatment. We conclude that CSM14.1 cells provide an excellent model for the study of IFN-gamma-mediated noncytolytic clearance of SINV from mature neurons.