Mk. Njenga et al., THEILERS VIRUS PERSISTENCE AND DEMYELINATION IN MAJOR HISTOCOMPATIBILITY COMPLEX CLASS II-DEFICIENT MICE, Journal of virology, 70(3), 1996, pp. 1729-1737
Mice,vith targeted disruption of the Ap gene of major histocompatibili
ty complex class II molecules (Ab'') were used to investigate the role
of class II gene products in resistance or susceptibility to virus-in
duced chronic demyelination in the central nervous system (CNS), Class
II-deficient mice from the resistant H-2(b) [H-2(b)(Ab(o))] and nonmu
tant H-2(b) backgrounds were infected with Theiler's murine encephalom
yelitis virus intracerebrally and examined for CNS virus persistence,
demyelination, and neurologic clinical signs. Virus titers measured by
plaque assays showed that 8 of 10 normally resistant nonmutant H-2(b)
mice had cleared the virus within 21 days, whereas the other 2 mice h
ad low titers. In contrast, all class II-deficient Ab(o) mice had high
virus titers for up to 90 days after infection (4.30 log(10) to 6.18
log(10) PFU per g of CNS tissue), Virus antigens and RNA were localize
d to the brains (cortex, hippocampus, thalamus, and brain stem) and sp
inal cords of Ab(o) mice. Colocalization identified persistent Theiler
's murine encephalomyelitis virus in oligodendrocytes and astrocytes b
ut not in macrophages. There was demyelination in 11 of 23 and 6 of 9
Ab(o) mice 45 and 90 days after virus infection, respectively, whereas
no demyelination was observed in infected nonmutant H-2(b) mice. Demy
elinating lesions in Ab(o) mice showed virus-specific CD8(+) T cells a
nd macrophages but no CD4(+) T cells, Spasticity and paralysis were ob
served in chronically infected Ab(o) mice but not in the nonmutant H-2
(b) mice. These findings demonstrate that class II gene products are r
equired for virus clearance from the CNS but not for demyelination and
neurologic disease.