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Immune Sensing of Latent Cytomegalovirus Reactivation:
Impact on Immune Senescence?
Molecular Virology Lab
Institute for Virology
Immunology Lab
Cytomegalic Inclusion Disease (CID):
a disease of the immunocompromised
Congenital infection (in the US)
Transplantation-associated (in the US)
Cases per annum:
40,000
Asymptomatic at birth: 36,000
5,400 Neurol. sequelae
Symptomatic at birth: 4,000
3,600 Neurol. sequelae
400 Fatal cases
Cases per annum:
Moderate disease:
Severe disease:
2,800
1,200
1,600
160 Fatal cases
IOM study: Vaccines for the 21st century
CMV vaccine is 1 out of 7 ranked in level 1
out of 26 candidate vaccines included in the study
Annual gain of
18,000 - 70,000 QALYs
Annual saving to the health system
US $ 1.1 billion - 4.0 billion
Courtesy of G.Jahn
Institute of Medical Virology
Tuebingen
Jahn et al., Dtsch. Med. Wochenschrift, 1988
Immune senescence:
A new indication for a CMV vaccine?
People aged 65 and older in the US ~ 40 million
Carriers of latent CMV ~ 30 million
Immune surveillance of CMV in the murine BMT model
6 Gy
~
mCMV
BMC
BALB/c
BALB/c
Donor
Recipient
Lungs
Latency
Virus
CD8 T cells
Acute phase
1
5
months
Holtappels et al., JVI, 1998
Podlech et al., JVI, 2000
10
Control of acute CMV infection in the lungs
6 Gy
~
mCMV
Inflammatory focus
BMC
BALB/c
BALB/c
Donor
Recipient
Lungs
Latency
Virus
CD8 T cells
Acute phase
1
5
months
Podlech et al., JVl, 2000
10
Red staining of intranuclear IE1 protein
Black staining of CD8 T cells
Control of acute CMV infection in the lungs
Effector CD8 T cells
Protection upon adoptive transfer
~
6 Gy
mCMV
BALB/c
Recipient
Podlech et al., JVI, 2000
Holtappels et al., JVI, 1998; 2000
• Activated phenotype CD62Llow
• Secrete IFN-g
• Lyse infected target cells
Persistence of protective CD8 T cell infiltrates during latency
Effector-memory CD8 T cells
6 Gy
~
mCMV
• Activated phenotype CD62Llow
• Secrete IFN-g
• Protect upon adoptive transfer
BMC
BALB/c
BALB/c
Donor
Recipient
Lungs
Latency
Acute phase
~
CD8 T cells
Virus
CD8 T cell
Episome
1
5
months
10
The immunodominant IE1 peptide
of murine CMV
ORF
m123 (ie1)
Phase
IE
Sequence
Restriction
168YPHFMPTNL176
Ld
Reference
Reddehase, Rothbard, and
Koszinowski, Nature, 1989
IE1
+ IFN-g
IFN-g
Processing and
presentation
Constitutive
proteasome
Processing
Immunoproteasome
of the IE1 peptide
TAP
ERAAP
For a review, see:
Reddehase,
Nature Rev. Immunol., 2002
ER
Golgi
Presentation
TCR
CD8+
T cell
Enrichment of IE1 peptide-specific CD8 T cells during latency
Lungs
Latency
Virus
CD8 T cells
2
1
m123/IE1
3.000
M84
m123/IE1
M83
M45
m18
12.000
30.000
M84
1
3
M45
2
4
m18
3
60.000
5
m04
4
10 mo
5
% ELISPOT-reactive CD8 T cells
5
m04
% ELISPOT-reactive CD8 T cells
1
Holtappels et al.,
J.Virol., 2000
M83
Acute phase
What is the motor that drives the selective expansion
of the IE1-specific CD8 T cells?
Major Immediate-Early (MIE)
region of mCMV
Selective and stochastic IE1
gene expression during latency
Signal
Receptor
ie1/3 transcription unit
5
4
3
2
TFBS
1
M122 m123
TF
P1/3 enhancer
Activation
Differential splicing
4
3
2
IE1 specific RT-PCR
1
IE1 mRNA
5
3
2
1
IE3 mRNA
What is the motor that drives the selective expansion
of the IE1 specific CD8 T cells?
Major Immediate-Early (MIE)
region of mCMV
Selective and stochastic IE1
gene expression during latency
Signal
Receptor
ie1/3 transcription unit
5
4
3
2
TFBS
1
M122 m123
TF
P1/3 enhancer
Activation
Differential splicing
4
3
2
IE1 specific RT-PCR
1
IE1 mRNA
5
3
2
1
IE3 mRNA
What is the motor that drives the selective expansion
of the IE1 specific CD8 T cells?
Major Immediate-Early (MIE)
region of mCMV
Selective and stochastic IE1
gene expression during latency
Signal
Receptor
ie1/3 transcription unit
5
4
3
2
TFBS
1
M122 m123
TF
P1/3 enhancer
Activation
Differential splicing
4
3
2
IE1 specific RT-PCR
1
IE1 mRNA
5
3
2
1
IE3 mRNA
What is the motor that drives the selective expansion
of the IE1 specific CD8 T cells?
Major Immediate-Early (MIE)
region of mCMV
Selective and stochastic IE1
gene expression during latency
Signal
Receptor
ie1/3 transcription unit
5
4
3
2
TFBS
1
M122 m123
TF
P1/3 enhancer
Activation
Differential splicing
4
3
2
IE1 specific RT-PCR
1
IE1 mRNA
5
3
2
1
IE3 mRNA
What is the motor that drives the selective expansion
of the IE1 specific CD8 T cells?
Major Immediate-Early (MIE)
region of mCMV
Selective and stochastic IE1
gene expression during latency
Signal
Receptor
ie1/3 transcription unit
5
4
3
2
TFBS
1
M122 m123
TF
P1/3 enhancer
Activation
Differential splicing
4
3
2
1
IE1 mRNA
5
3
2
1
IE3 mRNA
Poisson distribution analysis
of variegated gene expression
Kurz et al., JVI, 1999
Grzimek et al., JVI, 2001
Simon et al., JVI, 2005
Generation of recombinant CMV with a point mutation in the
codon of the C-terminal MHC anchor residue of the IE1 peptide
4
3
2
IE1
F
H
Y P
P
M P
F
T
H
N
L
Y
M
T
N A
GCA
P
L176A
CTA
WT and revertant
A176L
MHC class-I anchor mutant
Elimination of IE1 antigenicity enhances the frequency
of latency-associated IE1 transcription
~
Incidence of IE1 transcription*
~
150
131
105
100
84
50
36
27
21
10
Revertant
Mutant
* 5 lungs
Simon et al., in preparation
Desilencing and immune sensing hypothesis
IE1
Desilencing and immune sensing hypothesis
IE1-specific
CD8 T cell
Desilencing and immune sensing hypothesis
IE1-specific
CD8 T cell
IE1
Desilencing and immune sensing hypothesis
IE1-specific
CD8 T cell
Desilencing and immune sensing hypothesis
IE1-specific
CD8 T cell
IE1
Desilencing and immune sensing hypothesis
IE1-specific
CD8 T cell
Effector function
Multiple checkpoints for immune sensing
MIE locus latency
Stages of transcriptional reactivation
Recurrence
IE1
MIE Locus
Immunosuppression
anti-IE1
anti-X1
anti-Xn
~
Conditions for virus recurrence:
Open viral chromatin structure at all essential loci
Abrogation of immune sensing by immunosuppression
How could latency-associated CMV gene
expression contribute to immune senescence?
1. Cellular aging of clonotypic memory cells by a high number
of cell divisions
2. Misallocation of immune system resources by clonal expansion
of memory CD8 T cells specific for a single pathogen