Persistent infection of BSC-1 cells by defective measles virus derived from subacute sclerosing panencephalitis

A line of cells (IP-3), persistently infected with defective measles virus, was developed from co-cultures of subacute sclerosing panencephalitis-derived brain cells with monkey kidney cells (BSC-1). The line, carried for more than 45 serial passages, produced neither infectious virus nor hemagglutinin. Cultures consistently displayed a cycling focal cytopathic pattern of infection characterized by formation of syncytia, necrosis, and plaques followed by healing. Fluorescent measles antigen was present in damaged areas only, especially in syncytia. The development of syncytia was suppressed by measles antibody. Syncytia were lysed by antibody plus rabbit complement. A variant noncytopathic subline (IP-3-Ca) was derived from the 16th passage. Infectious virus was not detected. Cells were minimally positive for hemadsorption. Fluorescent measles antigen was present in all cells. Co-cultures of IP-3-Ca cells with normal BSC-1 cells developed massive syncytia and extensive destruction. The IP-3-Ca cells multiplied in the presence of measles antibodies and were destroyed by antibodies plus complement. The possible relevance of these findings to the pathogenesis of subacute sclerosing panencephalitis is discussed.