In this study we investigated pathological changes of the expression of the measles virus (MV) receptor, CD46, in subacute sclerosing panencephalitis (SSPE) brains. We analyzed CD46 expression in lesions of brain specimens from five SSPE patients in comparison to uninfected regions of the same brains and to normal human brains. The correlation between CD46 and MV infection, in individual cells in SSPE brains, was analyzed by double-staining procedures using monoclonal antibodies (mAbs) and in situ hybridization to detect MV-specific mRNAs. We found that CD46 was expressed at relatively low levels by neurons and astrocytes in normal brains in comparison to neuroblastoma and astrocytoma cell lines. Within heavily infected (MV-positive) brain lesions of all five SSPE cases, CD46 was either not detected or was expressed to a lesser degree by neural cells, irrespective of whether MV antigens were detectable or not. In contrast, normal levels of CD46 were found in SSPE brain tissue distant from the lesion. Using in situ hybridization, mRNAs of both MV nucleocapsid and MV hemagglutinin (MV-H) were detected in all SSPE lesions, while no or only small amounts of MV-H protein were detected. MV-infected neurons were never found to express CD46. Although a strict correlation between levels of the MV-H protein and the absence CD46 could not be seen, these findings suggest that the CD46 expression is reduced by the MV infection in lesions of SSPE brains.

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