Cell type-specific MxA-mediated inhibition of measles virus transcription in human brain cells

Measles virus (MV)-specific transcription in human brain cells is characterized by particularly low abundances of the distal mRNAs encoding the MV envelope proteins. Similar transcriptional restrictions of the closely related vesicular stomatitis virus have been observed in mouse fibroblasts constitutively expressing the interferon-inducible MxA protein (P. Staeheli and J. Pavlovic, J. Virol. 65:4498-4501, 1991). We found that MV infection of human brain cells is accompanied by rapid induction and high-level expression of endogenous MxA proteins. After stable transfection of MxA, human glioblastoma cells (U-87-MxA) released 50- to 100-fold less infectious virus and expression of viral proteins was highly restricted. The overall MV-specific transcription levels were reduced by up to 90%, accompanied by low relative frequencies of the distal MV-specific mRNAs. These restrictions were linked to an inhibition of viral RNA synthesis and not to a decreased stability of the viral RNAs. Our results indicate that expression of MxA is associated with transcriptional attenuation of MV in brain cells, thus probably contributing to the establishment of persistent MV central nervous system infections. In addition, the mechanism of MxA-dependent resistance against MV infection, in contrast to that of vesicular stomatitis virus, is cell type specific, because an inhibition of MV glycoprotein synthesis independent of transcriptional alterations was observed in MxA-transfected human monocytes (J. J. Schnorr, S. Schneider-Schaulies, A. Simon-Jödicke, J. Pavlovic, M. A. Horisberger, and V. ter Meulen, J. Virol. 67: 4760-4768, 1993).