Isolation of a Heterogeneous Population of Temperature-sensitive Mutants of Measles Virus from Persistently Infected Human Lymphoblastoid Cell Lines* by Grace Ju,$ Stephen Udem, Bracha Rager°zisman,§ and Barry

A number of slow neurological diseases occurring in an imals and in man appear to be associated with a long-term, chronic infection of the host by a virus or virall ike agent. Measles virus, or a var ian t of measles, has been shown to be the etiologic agent of the chronic and invar iab ly fatal human disease, subacute sclerosing panencephal i t is (SSPE). 1 In SSPE, the virus appears to produce a pers is tent infection of beth the central nervous system and lymphoid cells (1-3). There is also increasing evidence tha t measles virus might be associated with mul t ip le sclerosis (MS), and possibly wi th other chronic human diseases as well (4). Several observations suggest tha t lymphoid cells might serve as a reservoir for measles virus dur ing the long incubation period in a chronic infection before the onset of clinical manifestat ions. One of the first isolations of the measles var ian t virus associated with SSPE was from lymph nodes of SSPE pat ients (3). Recently, detection of measles viral ant igens in the mononuclear cells of the jejunal mucosa of pat ients with MS has been reported (5), and measlesl ike virus has been isolated from jejunal biopsies (6).