The
type-I interferon (IFN) inducible human MxA
protein exhibits
antiviral activity against a variety of RNA viruses including the measles virus (MV). In this study, we investigated the association between the expression of MV
antigens and MxA in
subacute sclerosing panencephalitis (
SSPE) brains. We analyzed the MxA expression in and around lesions in brains of three
SSPE patients and compared it with normal brains. Double staining with
antibodies against MxA and the MV nucleocapsid revealed that MxA was highly expressed in a belt surrounding MV-
antigen-positive lesions in
SSPE brains. In normal appearing regions distant from a lesion in
SSPE brains and in normal brains, MxA was not detected. Furthermore, MxA was often less or not expressed in the center of lesions expressing high amounts of MV
antigens. Such a pattern of MxA expression in
SSPE brains clearly indicates that newly infected cells release type I IFN and will become demarcated by a protecting barrier of MxA expressing cells. Double staining with
antibodies against MxA and
glial fibrillary acidic protein (GFAP) showed that the MxA
protein was expressed mainly in the cytoplasm of astrocytes. MxA expression did not correlate with the presence of cellular infiltrates of inflammatory cells, although some lymphoid cells were also positive for MxA. Since MxA inhibits the replication of MV, these findings suggest that the IFN-induced MxA
protein plays an important role in slowing down the viral spread in
SSPE brains and by doing so may contribute to the persistence of the MV-
infection.