Passage of the prototypic arenavirus lymphocytic choriomenigitis virus (LCMV) in cultured cells in the presence of the mutagenic agent 5-fluorouracil (FU) resulted in efficient and systematic virus extinction under conditions that did not significantly affect cell survival. FU-mediated extinction of LCMV was associated with 3.6- to 10-fold increases in the mutation frequencies for the three viral genes examined, but with only very modest effects on virus replication and transcription during a single round of infection. Likewise, FU did not affect expression of a LCMV minigenome. In contrast, the well documented antiviral effect of ribavirin against LCMV was not associated with significant increases in virus mutation frequencies, but rather with a dramatic inhibition of both viral RNA synthesis and LCMV minigenome expression. Mutagen induced viral extinction has been recently reported for positive strand RNA viruses polio and foot-and-mouth disease, and the lentivirus HIV-1. Our findings indicate that lethal mutagenesis can be effective also against LCMV, a negative strand RNA virus. Moreover, FU treatment prevented the establishment of LCMV persistent infection in mice deficient in B and T cells, suggesting the feasibility in vivo of lethal mutagenesis as a novel antiviral strategy.

Borna disease virus (BDV), a nonsegmented, negative-stranded (NNS) RNA virus, causes central nervous system (CNS) disease in a broad range of vertebrate species, including felines. Both viral and host factors contribute to very diverse clinical and pathological manifestations associated with BDV infection. BDV persistence in the CNS can cause neurobehavioral and neurodevelopmental abnormalities in the absence of encephalitis. These BDV-induced CNS disturbances are associated with altered cytokine and neurotrophin expression, as well as cell damage that is very restricted to specific brain regions and neuronal subpopulations. BDV also targets astrocytes, resulting in the development of prominent astrocytosis. Astrocytes play essential roles in maintaining CNS homeostasis, and disruption of their normal activities can contribute to altered brain function. Therefore, we have examined the effect of BDV infection on the astrocyte's physiology. We present here evidence that BDV can establish a nonlytic chronic infection in primary cortical feline astrocytes that is associated with a severe impairment in the astrocytes' ability to uptake glutamate. In contrast, the astrocytes' ability to uptake glucose, as well as their protein synthesis, viability, and rate of proliferation, was not affected by BDV infection. These findings suggest that, in vivo, BDV could also affect an important astrocyte function required to prevent neuronal excitotoxicity. This, in turn, might contribute to the neuropathogenesis of BDV.Borna disease (BD) virus (BDV) causes central nervous system (CNS) disease in a broad range of vertebrate species (36,43,48,63,65). BDV has a nonsegmented, negative-strand (NNS) RNA genome (9, 17). Based on its unique genetic and biological features, BDV is considered to be the prototypic member of a new virus family, Bornaviridae, within the order Mononegavirales (19,68).Naturally occurring BDV infections were thought to be mainly restricted to horses and sheep within certain geographic regions of central Europe. Current evidence, however, indicates that the natural host range, geographic distribution, and prevalence of BDV are much broader than previously considered (36,43,63,65). The genetics, immune status, and age of the host, as well as viral factors, contribute to a high degree of heterogeneity in disease symptoms and pathological manifestations associated with BDV infection. Clinical manifestations can range from dramatic to subtle or even been unapparent (32,36,43,63,65). Nevertheless, all known BDV isolates are noncytolytic and highly neurotropic (43,48,65). Heightened viral gene expression in limbic system structures and neuronal structural alterations within the hippocampal formation are the main histopathological hallmarks of BDV infection (32,34,35). Immune cell infiltrates are frequently, but not always, observed in the CNS of BDV-infected animals, and immunemediated neuronal damage is thought to be responsible for the clinical symptoms associated with classic BD (5,48,65,71). BDV affects the postnata...

Borna disease virus (BDV) has a non-segmented, negative-strand (NNS) RNA genome. In contrast to all other known NNS RNA animal viruses, BDV replication and transcription occur in the nucleus of infected cells. Moreover, BDV uses RNA splicing for the regulation of its genome expression. Two introns (I and II), both present in two viral primary transcripts of 2n5 and 7n2 kb, have been reported in BDV. Here, evidence is provided of a new BDV intron, intron III, generated by alternative 3h splicesite choice. Intron III-spliced mRNAs were detected at early times post-infection and found to be present in cells from different types and species. Intron III-spliced mRNAs have coding capability for two new viral proteins with predicted molecular masses of 8n4 and 165 (p165) kDa. p165 is a deleted form of the BDV L polymerase, containing three RGD motifs and a signal peptide signal that could target it into the secretory pathway. These findings underscore the proteomic complexity exhibited by BDV.