Attempts at experimental transmission and electron microscopic observations in subacute sclerosing panencephalitis

Immunohistochemical and electron microscopic techniques in the diagnosis of viral encephalitides

Electron microscopy and in particular, immunohistochemical examination techniques have substantially improved the chances to attain an etiologic diagnosis in viral encephalitis. The application of these techniques is needed first of all in the examination of cerebral biopsy specimens, but they can contribute to the clearing of the etiology at post mortem study of the brain, too. This review outlines the basic techniques and their application fields. In immunohistochemistry beside the demonstration of specific viral antigens the analysis of the humoral and cellular immune reactions and the identification of the cell types involved by cell specific markers is also important. The second part of the review gives a synopsis of the results of electron microscopic and immunohistochemical studies in the most important acute, subacute and chronic encephalitides occurring in Europe.

SSPE-BIKEN: a naturally arising hemagglutination-defective mutant of measles virus

Biochemical and genetic methods have been used to investigate a defective variant of measles virus previously isolated from a patient with subacute sclerosing panencephalitis (SSPE). Since its isolation, this syncytiogenic strain (SSPE-BIKEN) has remained cell-associated; infected cells do not hemadsorb and do not release infectious virus. Immune precipitation and polyacrylamide gel electrophoresis were used to study the synthesis of measles virion proteins in SSPE-BIKEN-infected cells. All of the virion proteins were detected in immune precipitated whole cell extracts. However, the hemagglutinin (HA) protein was not detected on the cell surface by lactoperoxidase iodination. These results suggest that the failure of the HA protein to insert into the cell membrane accounts for the block in the release of infections virus. Radioactively labeled, noninfectious, virus-like particles have been purified from the media of SSPE-BIKEN-infected cells. These particles contain virus nucleocapsid, nucleocapsid-associated, and membrane proteins, but very little HA and hemolysin proteins. Genetic complementation between SSPE-BIKEN and a temperature-sensitive mutant of measles virus was observed and suggests that the SSPE isolate defect is due to a mutation. Additional evidence of a mutation is provided by the detection of low frequency revertant progeny in SSPE-BIKEN stocks. Our results support the hypothesis that genetic variants of measles virus are involved in the etiology of SSPE.