Involvement of temperature sensitive syncytium inducing VSV or defective retroviruses in the development of spongiform encephalopathies

Various enveloped viruses can induce syncytia in competent cells. Some temperature-sensitive mutants can express the trans-membrane viral G antigen under non-permissive conditions. The G antigen can then migrate at long distances, engulfing thousands of cells without producing any virus. When a temperature-sensitive vesicular stomatitis virus (VSV) infects a sensitive host, and under the condition that the G antigen is expressed, spongiosis can be induced in the central nervous system in the absence of detectable virus multiplication. We postulate that such a mechanism might be observed with various enveloped viruses, as recently illustrated with knock-out mice experimentally infected with defective murine leukemia virus (MULV).