Characterization ofIMVirus, WhichIsFrequently Isolated from Cerebrospinal Fluid ofPatients withMultiple Sclerosis andOther Chronic Diseases oftheCentral NervousSystem

Atransmissible agent, theIMvirus, antigenically related totheJapanese subacute myelo-optico-neuropathy virus, hasbeenisolated fromseveral humancerebrospinal fluids obtained fromAmerican patients with multiple sclerosis andother chronic diseases ofthecentral nervoussystem. Theisolates were propagated in humandiploid fibroblast (MRC5)cells, andvirus wasreleased into theculture mediumintheabsence ofovert cytolysis. Infection ofMRC5cells resulted ina subtle alteration inthenormal growth pattern ofthecells. In unstained cultures, thecell changes were somildthat itwas necessarytocarryoutallvirus assaysundercode toeliminate bias. Cells inlate passageswere moresusceptible thanvigorously growing cells inearly passages. Analysis ofthekinetics ofreplication revealed that newlysynthesized progenyvirus was first detected about12 hpostinfection, thatmaximal virus release occurred by48hpostinfection, andthatvirus production was persistent throughout an 8-day period. Several inhibitors ofDNA synthesis were effective inblocking viral replication, including cytosine arabinoside, iododeoxyuridine, andphosphonoacetic acid.A substantial decrease ininfectivity wasobserved upon treatment ofIMvirus withether, suggesting that alipid-containing structure isessential forinfectivity. Ultrafiltration studies approximated thesize (diameter) ofIMvirus tobe between 100and200nm. Recently, wereported theisolation ofavirus fromthe cerebrospinal fluid (CSF) ofthree Texanpatients withmultiple sclerosis (MS)andonepatient withamyotrophic lateral sclerosis (8). Since then, wehaverecovered anumberof additional American isolates, chiefly frompatients withMS butalsofrompatients withother chronic central nervous systemdiseases. Theisolates proved tobeantigenically related toa virus recovered inJapanfromtheCSFof patients withsubacute myelo-optico-neuropathy