Genes induced after BDV infection in Sprague Dawley and Lewis rats

Borna Disease Virus (BDV) is a neurotropic virus that persistently infects neurons in the central nervous system of various hosts, including rats. Although BDV is known to be an IFN sensitive virus, determination of the cellular mRNA transcript levels revealed the induction of IFN-stimulated genes in organotypic rat hippocampus slice cultures, raising the question how BDV evades this innate immune response. Using rat Mx protein as a specific marker for IFN-induced gene products, we could show that neurons lack detectable levels of Mx in these BDV infected cultures, whereas astrocytes and microglial cells were Mx positive. Neurons remained Mx negative after treatment of uninfected hippocampus cultures as well as primary dissociated neuronal cultures with high concentrations of IFN-α. This non-responsiveness correlated with a lack of a detectable nuclear translocation of pSTAT1 in rat neurons. Consistently, IFN treatment of BDV-infected rat neurons did not prevent the establishment of a viral persistence in the neuronal tissue. However, IFN treatment efficiently prevented vesicular stomatitis virus (VSV) replication, indicating that these cells can mount a weak innate immune response. In contrast, IFN treatment of mouse neurons resulted in the upregulation of Mx1 proteins and inhibition of BDV replication, indicating species-specific differences in the IFN response in neurons between mice and rats. Rat neurons may therefore represent the ideal cell type for BDV to evade the innate immune in the central nervous system. To determine the mRNA levels in the hippocampal slice cultures after BDV infection in Sprague Dawley and Lewis rats Hippocampal slice cultures were prepared from newborn Lewis and SD rats (P0-P2). Half of the samples remained uninfected, whereas the other half was infected with 1000 focus forming units (FFU) of BDV strain He/80. Total RNA from a pool of 12 slice cultures was prepared