Reactive astrocytes in viral infections of the human brain express endothelin-like immunoreactivity

In order to investigate the expression of endothelin-like immunoreactivity in astrocytes of viral infections of the human brain the avidin-biotin peroxidase complex method and a polyclonal antiserum were used. Autopsy material was obtained from 5 cases of herpes simplex encephalitis, two of progressive multifocal leukoencephalopathy (PML) and two of subacute sclerosing panencephalitis (SSPE). All the 5 herpes simplex encephalitis cases presented groups of immunoreactive astrocytes around necrotic, inflammatory lesions. The PML cases exhibited a large number of immunoreactive astrocytes in and around lesions of the white matter. The cases of SSPE disclosed numerous, markedly stained fibrillary immunoreactive astrocytes; they were most abundant in degenerated regions of the white matter. The processes and peripheral cytoplasm of giant astrocytes in the PML cases contained immunoreactive material but the perinuclear region was devoid of such material. In the herpes simplex and the SSPE cases immunoreactivity was present throughout the cytoplasm and processes of reactive fibrillary astrocytes. Many nerve cells in the cerebral cortex, hippocampus, cerebellum and pons of control cases exhibited endothelin-like immunoreactivity but this occurred in only exceptional astrocytes of control cases. Endothelin-like immunoreactivity was not present in the oligodendrocytes and vascular endothelial cells of controls and cases of virus infection. The expression of endothelin-like immunoreactivity in astrocytes in human viral diseases reflects probably an increased intracellular content of endothelin. If this peptide is released from such astrocytes, it may act as a mitogen and by inducing constriction of arterioles it may influence the microcirculation.