Spontaneous and differentiation-dependent regulation of measles virus gene expression in human glial cells.

The expression of measles virus (MV) in six different permanent human glioma cell lines (D-54, U-251, U-138, U-105, U-373, and D-32) was analyzed. Although all cell lines were permissive for productive replication of all MV strains tested, U-251, D-54, and D-32 cells spontaneously revealed restrictions of MV transcription similar to those observed for primary rat astroglial cells and brain tissue. In vitro differentiation of D-54 and U-251 cells by substances affecting the intracellular cyclic AMP level caused a significant reduction of the expression of the viral proteins after 18, 72, and 144 h of infection. This pronounced restriction was not paralleled to a comparable level by an inhibition of the synthesis and biological activity in vitro of virus-specific mRNAs as shown by quantitative Northern (RNA) blot analyses and in vitro translation. The block in viral protein synthesis could not be attributed to the induction of type I interferon by any of the substances tested. Our findings indicate that down-regulation of MV gene expression in human brain cells can occur by a cell type-dependent regulation of the viral mRNA transcription and a differentiation-dependent regulation of translation, both of which may be crucial for the establishment of persistent MV infections in the central nervous system.