Transcript Use of rabies virus as a transneuronal tracer of neuronal

Use of rabies virus as a transneuronal tracer
of neuronal connections: implications for the
understanding of rabies pathogenesis
Gabriella Ugolini
NBCM, CNRS Gif-sur-Yvette
Kuypers & Ugolini, Trends Neurosci. 1990
Amplification
of the signal:
self-amplifying
marker
3°
Rabies
Virus
CVS strain
(1010
PFU/ml)
Asymptomatic period
Transneuronal tracing with
rabies virus:
1 - Amplification of the signal: selfamplifying marker.
2 - Exclusive tropism for neurones in vivo.
3 - Absence of degeneration of infected
neurones: possibility of combined
visualisation of neurotransmitters & other
tracers.
4 - Specificity: propagation exclusively by
transneuronal transfer between connected
neurones at chemical synapses.
5 - Intracellular transport is preferentially
addressed to dendrites: transneuronal
transfer occurs only in the retrograde
direction.
6 - Ubiquitous distribution of rabies
receptors in the CNS, but not in the
peripheral nervous system.
7 - The only technique allowing the
identification of neuronal connections
across a practically unlimited number of
synapses.
1 - Peripheral uptake is restricted to
motoneurons: no uptake via sensory
and autonomic neurons
2 - No propagation via gap junctions (DM MNs)
3 - Sequential infection of 2°, 3 and 4° order
neurons
4 - Centrifugal transfer to sensory and
autonomic neurons at long time points, during
the asymptomatic period
RAT
Tang, Rampin,
Giuliano & Ugolini
(1999) J. Comp.
Neurol. 414:167-192.
PRIMATES (macaque monkeys): injection into the lateral rectus (LR) muscle
1 - Peripheral uptake is restricted to motoneurons
2 - Ubiquitous distribution of rabies receptors within the CNS
3 - Centrifugal transfer to the vestibular (Scarpa’s) ganglion
at 3 days p.i. (during the asymptomatic incubation period)
Ugolini et al. J. Comp. Neurol. 2006
PRIMATES: differences in monosynaptic pathways to motoneurons of the
lateral rectus muscle (LR) which innervate slow and fast muscle fibers
- Muscle: defective replication in fibrocytes,
no virus in myocites.
- No spread within the muscle: uptake
occurs only at the site of inoculation.
- Combined visualisation of rabies virus and
choline acetyltransferase (CAT): infected
motoneurons remain viable.
Primates: Injection of rabies virus into
the CNS (Posterior parietal cortex, areas VIP, MIP)
Same pattern of propagation of rabies
virus after central and peripheral
inoculations:
1 - Infection of first-order neurons at 2 days.
2 - Transneuronal transfer occurs only
retrogradely (no anterograde transfer to the
pontine nuclei).
3 - Transfer to connected neurons at
sequential intervals of 12 hrs.
4 - No local spread or cell death.
3° order at 3 days p.i.: centrifugal transfer
to the vestibular (Scarpa’s) ganglion
2° order at 2.5 days p.i.:
vestibular nuclei
Co-injection of rabies virus & a conventional tracer
(Cholera toxin B fragment, CTB) = no interference
between uptake of rabies & CTB
3°
Scarpa’s
ganglion
Rabies pathogenesis:
1.
In primates & rodents (rats, guinea pigs),
peripheral uptake is restricted to motor
endplates/axons: in keeping with the
presynaptic location of NCAM and with a role
of Ach nicotinic receptors (despite their mainly
post-synaptic location).
2.
Rabies virus does not spread within the
muscle: uptake occurs only at the site of
inoculation = importance of complete wound
infiltration with rabies antibodies as soon as
possible, to prevent virus entry!
3.
Motoneurons are the only gateway for
propagation of rabies virus to the CNS.
4.
Rabies virus propagates exclusively by
retrograde transneuronal transfer at chemical
synapses - not via gap junctions or local
spread.
5.
Transneuronal transfer occurs only
retrogradely – due to the fact that, after
replication, centrifugal intracellular transport
of rabies targets only dendrites, and not
axons.
6.
Retrograde transport and transneuronal
transfer occur at high speed, by active axonal
transport (P/LC8 interactions and microtubulebased transport)
7.
Ubiquitous distribution of rabies receptor(s) within the
CNS: transneuronal transfer involves all known
populations connected to first-order neurons,
regardless of their transmitters.
8.
Extensive propagation of rabies virus within the CNS
during the asymptomatic period! Each successive step
of transfer (to 2°, 3°, 4° order neurons) requires only 12
hrs, regardless of the distance.
9.
Infection of sensory and autonomic neurons requires
longer incubation times because it reflects centrifugal
propagation from the CNS to the periphery.
Acknowledgments
Supported by:
EU grants BIO4-CT98-0546 (TransVirus) &
QLK6-CT-2002-0015 (EUROKINESIS)