Two interferon-independent double-stranded RNA-induced host defense strategies suppress the common cold virus at warm temperature

Most strains of rhinovirus (RV), the common cold virus, replicate better at cool temperatures found in the nasal cavity (33-35 degrees C) than at lung temperature (37 degrees C). Recent studies found that although 37 degrees C temperature suppressed RV growth largely by engaging the type 1 IFN response in infected epithelial cells, a significant temperature dependence to viral replication remained in cells devoid of IFN induction or signaling. To gain insight into IFN-independent mechanisms limiting RV replication at 37 degrees C, we studied RV infection in human bronchial epithelial cells and H1-HeLa cells. During the single replication cycle, RV exhibited temperature-dependent replication in both cell types in the absence of IFN induction. At 37 degrees C, earlier signs of apoptosis in RV-infected cells were accompanied by reduced virus production. Furthermore, apoptosis of epithelial cells was enhanced at 37 degrees C in response to diverse stimuli. Dynamic mathematical modeling and B cell lymphoma 2 (BCL2) overexpression revealed that temperature-dependent host cell death could partially account for the temperature-dependent growth observed during RV amplification, but also suggested additional mechanisms of virus control. In search of a redundant antiviral pathway, we identified a role for the RNA-degrading enzyme RNAseL. Simultaneous antagonism of apoptosis and RNAseL increased viral replication and dramatically reduced temperature dependence. These findings reveal two IFN-independent mechanisms active in innate defense against RV, and demonstrate that even in the absence of IFNs, temperature-dependent RV amplification is largely a result of host cell antiviral restriction mechanisms operating more effectively at 37 degrees C than at 33 degrees C.