Folie 1

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The role of antigen presenting mechanisms in
vaccine planning
Prof. Barbara Seliger
Institute of Medical Immunology Martin Luther
University Halle, Germany
Nordic Centre of Excellence for Development of
anti-tumor Vaccine Concepts Forli, 2nd March
2007
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Prerequisite for proper immune responses

• presentation of tumor-associated antigens via
  MHC class I molecules to CD8 T cells
• effective costimulation for induction of
  effector functions
• overcoming activities of negative regula-
• tory signals and immune cells
• circumventing immune escape mechanisms

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Physiological MHC class I antigen processing and
presentation
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Receptors and ligands involved in the T
cell-mediated immune responses
TCR
TCR
STOP!
GO!
PD-1
4-1BB
ICOS
IL-2
B7-R?
CD8
B7-R?
MHC I
ICOS
øMHC I
B7-R?
4-1BB
CTLA-4
B7-H1,2,3,4
CD28
IL-2
BTLA
B7-1, B7-2
LICOS
B7-x
B7-1, B7-2
Tregss (CD4CD25FoxP3)
CD4 T cell help
OX-40
TGF-ß
MHC II
IL-10
øMHC II
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Tumor host interaction
stroma endothel
tumor microenvironment
(immune cell infiltrate)
APC B cells DC
tumor cell
NKT
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Different categories of immune escape of tumors

• alterations of tumors by loss of function
• of activating immune modulatory molecules
• alterations of tumors by gain of function of
• inhibitory immune modulatory molecules
• active suppression of immune cell function
• by inhibitory molecules of the tumor
• induction of immune suppressive cells thereby
• blocking immune responses

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Immune escape-mechanisms of tumor cells
apoptosie
Fas
TCR
signal 1
no activation
CD28
signal 2
B7-R
B7-H
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Dual role of the immune system
ying and yang
prevention of tumor growth
facilitation of tumor progression selection of
immune escape- variants
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Schematic diagramm of a clinical vaccination
trial
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Monitoring patients prior to and during immune
therapy
RCC patient
surgery
establishment of cell lines
pre and post operation
tissue preparation
NN and TU cell lines
NN and TU tissue
blood serum
urine
monitoring of TAA, APM, immune modu- latory
molecules
monitoring of T cell responses and tumor
phenotype
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Distinct frequencies of MHC class I abnormalities
in human tumors of distinct histology

• HLA class I antigen loss (9-52)
• HLA class I downregulation (3-20)
• selective loss or downregulation of HLA class I
  allospecificities (15-50)

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Defects in the HLA class I surfaceexpression in
tumor lesions
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Deficient expression of TAP1, LMP2, LMP7 in
primary and metastatic RCC
oncocytoma (200x)
RCC, clear cell type, G2 (100x)
RCC, clear cell type, metastasis (100x)
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Alterations of APM components an early or late
event?
defects in the APM expression and immune
selection of tumor cells can occur at different
stages of disease

• during the course of disease
• late in tumor progression originating from
• metastasis
• during immunotherapy!
• dependence of tumor type

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Association of MHC class I, LMP2 and LMP7
expression with patients survival in HNSCC
MHC I
LMP 2
LMP 7



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DC vaccination critical aspects

• distinct APM, co-stimulatoy and amino-
• peptidase expression profiles in different
• DC subtypes
• DC obtained from tumor patients with
• a reduced immune stimulatory potential
• altered DC function due to immune
• suppressive tumor microenvironment

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Differentiation-specific expression of APM
components
APM expression pattern during DC maturation
human blood or buffy coat CD14 monocytes
immature DC RNA, protein
mature DC RNA, protein
day 1, 3 5 GM-CSF IL4
day 5 day 6 day 7 cytokine coc
ktail
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Differential expression of MHC class I components
during DC maturation
TAP2
ß2-m
TAP1
13 kD
71 KD
72 kD
HLA a chain
tapasin
calnexin
47 kD
90 KD
44 kD
PA28a
LMP2
LMP7
30 kD
25 kD
25 KD
immature mature control
immature mature control
immature mature control
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Distinct role of of differentiation-dependent APM
expression in DC
immature DC
mature DC
LMP
TAP, tapasin, MHC
peptide presentation
peptide generation
impact on the design of DC-based immunotherapies
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Gain or loss of function phenotype of tumors
escaping immune responses I
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Gain or loss of function phenotype of tumors
escaping immune responses II
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Complexity of natural tumor associated immune
responses

• multiple mechanisms of immune escape can
  occur and may reflect immune editing
• host tumor relationship involves immune
  responses, immune escape, immune editing and
  immune adaptation
• antitumor immunity may be regional rather than
  systemic

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Immune monitoring required for the development
of more effective immunotherapies

• rapid high-through put analysis of cellular
• immune responses to tumor antigens
• monitoring of immune responses in blood,
• lymph nodes and tumor compartments
• patient-specific modulation of immune
• responses
• selection of immunotherapy based on
  pretreatment and tumor escape
• determination of the effector memory T
• cell phenotypes optimal for tumor control

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Acknowledgements
Derek Atkins, Jun Li, Rudolf Lichtenfels, Chiara
Massa, Markus Meissner Soldano Ferrone III.
Department of Internal Medicine, Mainz and
Martin Luther University, Halle Roswell Park
Cancer Center, Buffalo
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Different immune escape mechanismsof tumors

• loss of antigen presentation
• antigenic loss variants
• fas counter attack
• escaping death receptor signaling
• lacking inhibition/blocking activation
• tumor-induced immune suppression
• suppression of anti-tumor responses