There are a number of similarities between canine distemper
and murine models of virus-induced demyelination
such as Theiler’s virus and mouse hepatitis virus
infection. As in the mouse models, canine distemper is
also a systemic infection with subsequent involvement of
the nervous system. Both virus-induced oligodendroglial
changes as well as inflammatory myelin damage occur in
distemper and in the mouse models. While direct viral
destruction of oligodendrocytes has been found in mice,
there is no clear evidence for oligodendrocyte necrosis or
apoptosis in distemper. In distemper there is a restricted
infection of oligodendrocytes with a dramatic impairment
of myelin metabolism. In addition, virus-induced
microglial cell activation probably also plays a role in
the demyelinating process. Since extensive experimental
manipulation of the immune system as in the murine
models is not feasible in dogs, direct comparison between
the canine model and the demyelinating conditions
in mice is difficult. There is little doubt, however,
that the local anti-virus immune/inflammatory response
contributes to myelin damage in the sense of a bystander
effect in all models, involving a variety of molecules such
as reactive oxygen radicals and cytokines. There is evidence
for the triggering of autoimmune reactions in
some of the mouse models, and also in distemper. It is
uncertain to what extent such events play an active role
in myelin damage. So far, there is no conclusive evidence
in our animal models for a virus-induced autoimmune
disease which continues to progress despite complete
clearance of the infectious agent, as proposed in MS.
Rather, common to distemper and mouse models is
virus persistence in the CNS, which appears to be the
key to the progression of the disease. Apparently, the
persistent agent precipitates recurrent immune reactions
even though the infectious load may be very small and
difficult to detect. Therefore, a major remaining challenge
is to understand mechanisms of virus persistence,
which may also lead to new approaches to discover
hidden agents in the nervous system.
There are a number of similarities between canine distemperand murine models of virus-induced demyelinationsuch as Theiler’s virus and mouse hepatitis virusinfection. As in the mouse models, canine distemper isalso a systemic infection with subsequent involvement ofthe nervous system. Both virus-induced oligodendroglialchanges as well as inflammatory myelin damage occur indistemper and in the mouse models. While direct viraldestruction of oligodendrocytes has been found in mice,there is no clear evidence for oligodendrocyte necrosis orapoptosis in distemper. In distemper there is a restrictedinfection of oligodendrocytes with a dramatic impairmentof myelin metabolism. In addition, virus-inducedmicroglial cell activation probably also plays a role inthe demyelinating process. Since extensive experimentalmanipulation of the immune system as in the murinemodels is not feasible in dogs, direct comparison betweenthe canine model and the demyelinating conditionsin mice is difficult. There is little doubt, however,that the local anti-virus immune/inflammatory responsecontributes to myelin damage in the sense of a bystandereffect in all models, involving a variety of molecules suchas reactive oxygen radicals and cytokines. There is evidencefor the triggering of autoimmune reactions insome of the mouse models, and also in distemper. It isuncertain to what extent such events play an active rolein myelin damage. So far, there is no conclusive evidencein our animal models for a virus-induced autoimmunedisease which continues to progress despite completeclearance of the infectious agent, as proposed in MS.Rather, common to distemper and mouse models isvirus persistence in the CNS, which appears to be thekey to the progression of the disease. Apparently, thepersistent agent precipitates recurrent immune reactionseven though the infectious load may be very small anddifficult to detect. Therefore, a major remaining challengeis to understand mechanisms of virus persistence,which may also lead to new approaches to discoverhidden agents in the nervous system.
การแปล กรุณารอสักครู่..
