THE COURSE OF DISEASE AND PERSISTENCE OF VIRUS IN THE CENTRAL-NERVOUS-SYSTEM VARIES BETWEEN INDIVIDUAL CBA MICE INFECTED WITH THE BEAN STRAIN OF THEILERS MURINE ENCEPHALOMYELITIS VI-RUS

Following intracerebral inoculation of the BeAn strain of Theiler's mu rine encephalomyelitis virus the course of the acute infection and per sistence of virus in the CNS varies between individual CBA mice. On th e basis of clinical signs, virus distribution, virus titres, histopath ology and Southern blot hybridization analysis of virus specific RT-PC R amplified products from total brain and spinal cord RNA, individual CBA mice could be placed into one of three groups. The first group wer e those animals which died of acute encephalitis. The second group wer e animals with or without clinical signs which had early high CNS viru s titres, and in addition to scattered foci of infection had spread of virus in specific neuronal nuclei followed by destruction of these ar eas and thereafter persistence of virus in the CNS. The third group ha d no clinical signs, low CNS virus titres, small foci of CNS infection and were negative for virus after 28 days. This third pattern of infe ction was also seen in BALB/c mice. Between 50 and 268 days post-infec tion 53% of CBA mice were positive for viral RNA in the CNS by RT-PCR. No BALB/c mice were positive. In both the acute and persistent infect ion there was a correlation between serum neutralizing antibody titre and clinical signs. During the acute infection BeAn RNA could be detec ted in neurons and astrocytes. Oligodendrocytes were negative. In thos e CBA mice with persistence, viral RNA was observed in scattered indiv idual or small foci of cells, predominantly oligodendrocytes, in both the brain and spinal cord.