A dissertation on: Platelets, hemostasis, immunity, and pathogens: A conceptual understanding of their interactions. Open Access
Loria, David (2012)
Abstract
Abstract
Platelets, hemostasis, immunity, and pathogens: A conceptual
understanding
of their interactions
Severe arenaviral infections in humans are characterized by
clinical findings
common to other viral hemorrhagic fevers (VHF), including
thrombocytopenia,
leukopenia, skin and internal organ hemorrhages, high viral
replication, splenic
necrosis, and death. Host responses, rather than direct damage by
the arenaviral
replication, account for most of the observed pathology, but it is
not known what
protective roles platelets may have in each of the manifestations.
To address this
issue in an animal model, we compared non-depleted (100%), partial
y depleted
(15%), and profoundly (<2,5%) platelet-depleted mice infected
with the mouse
arenavirus lymphocytic choriomeningitis virus (LCMV). Here, we
describe that
systemic bleedings and death were seen only in those animals
receiving the
stronger depletion treatment. Furthermore, we showed that the
non-hemorrhagic
but partial y platelet-depleted mice were unable to control the
viral replication due
to generalized splenic necrosis, affecting innate and adaptive
immune cel s.
These data suggest that, by their supportive roles in hemostasis,
platelets may
be preventing the severe pathology observed in human arenaviral
infections.
Table of Contents
Table of Contents
DISTRIBUTION
AGREEMENT..............................................................................................................1
A DISSERTATION
ON:............................................................................................................................5
ACKNOWLEDGEMENTS
........................................................................................................................6
CHAPTER 1: INTRODUCTION
.............................................................................................................1
CHAPTER 2: THEORETICAL BACKGROUND
...................................................................................6
Diagram 1.
...............................................................................................................................................................6
IMMUNITY AND
PATHOGENS.............................................................................................................6
INNATE SOLUBLE IMMUNITY
...................................................................................................................................7
INNATE CELLULAR IMMUNITY
..............................................................................................................................10
ADAPTIVE IMMUNITY B CELLS
.............................................................................................................................11
ADAPTIVE IMMUNITY T CELLS
.............................................................................................................................12
IMMUNE SUPPRESSION BY VIRUSES
.....................................................................................................................13
Immunosuppression-inducing viral infections in
humans...............................................................14
Immunosuppression in the LCMV clone 13 murine
model...............................................................18
IMMUNITY AND
HEMOSTASIS.........................................................................................................
19
INFLAMMATION.......................................................................................................................................................19
IMMUNE CELLS INTERACTION WITH
ENDOTHELIUM........................................................................................20
RECIRCULATION AND TRAFFICKING
....................................................................................................................20
PLATELETS AND HEMOSTASIS
.......................................................................................................
21
PLATELET
STRUCTURE...........................................................................................................................................21
PLATELET
RECEPTORS...........................................................................................................................................22
PLATELET
GRANULES.............................................................................................................................................24
PLATELET ATTACHMENT AND
AGGREGATION...................................................................................................25
PLATELETS AND VASCULAR
LEAKAGE.................................................................................................................27
PLATELETS AND
IMMUNITY............................................................................................................
29
LEUKOCYTE
EXTRAVASATION...............................................................................................................................30
PLATELETS AND TOLL-‐LIKE RECEPTORS
(TLRS).............................................................................................30
PLATELETS AND CD40L
.......................................................................................................................................31
PLATELETS MODULATION OF IMMUNE
RESPONSES..........................................................................................32
PLATELET LEUKOCYTE AGGREGATES AND EXTRACELLULAR
TRAPS..............................................................34
PLATELET AND ORGAN REJECTION
......................................................................................................................35
PLATELETS AND
PATHOGENS.........................................................................................................
36
PLATELETS AND PATHOGEN
INTERACTIONS......................................................................................................37
Bacteria..................................................................................................................................................................37
Virus.........................................................................................................................................................................41
Parasites
................................................................................................................................................................43
PLATELETS AND LPS SHOCK SYNDROME
...........................................................................................................44
PATHOGENS AND
THROMBOCYTOPENIA.............................................................................................................45
Lymphocytic choriomeningitis virus
.........................................................................................................45
HIV............................................................................................................................................................................46
Dengue....................................................................................................................................................................47
Malaria
...................................................................................................................................................................48
PATHOGENS AND HEMOSTASIS ..................................................................................................... 51
Diagram 2. ............................................................................................................................................................51
INFLAMMATION AND HEMORRHAGES
.................................................................................................................51
TUMOR GROWTH IN
THROMBOCYTOPENIA........................................................................................................52
HEMORRHAGES IN
VHFS.......................................................................................................................................53
OUR
RESULTS...........................................................................................................................................................53
CHAPTER 3: MATERIALS, METHODS, AND SYSTEMS OPTIMIZATION
............................... 54
MICE, VIRUSES, AND
INFECTIONS.........................................................................................................................54
PLATELET DEPLETIONS, PLATELETS COUNTS, AND THROMBOPOIETIN TREATMENT
................................54
FLOW CYTOMETRY AND LIVE/DEAD
DISCRIMINATION....................................................................................55
HISTOLOGY AND IMMUNOFLUORESCENCE
MICROSCOPY.................................................................................55
PEPTIDE STIMULATIONS, TETRAMER STAINING, AND
VSV-‐NEUTRALIZING ANTIBODIES
.........................55
CYTOKINE
ANALYSIS...............................................................................................................................................56
STATISTICAL
ANALYSIS..........................................................................................................................................56
CHAPTER 4: RESULTS
........................................................................................................................
57
LOW LEVELS OF CIRCULATING PLATELETS PREVENT SEVERE SYSTEMIC
HEMORRHAGE AND LETHALITY
DURING ACUTE LCMV
INFECTION.......................................................................................................................57
MICE WITH REDUCED PLATELET NUMBERS ARE UNABLE TO CONTROL LCMV
ARMSTRONG
REPLICATION
...........................................................................................................................................................58
LEUKOCYTE NUMBERS AND LOCATIONS ARE NOT AFFECTED BY PLATELET
REMOVAL..............................59
EARLY INNATE CONTROL OF LCMV REQUIRES
PLATELETS............................................................................60
CD8 T CELL RESPONSES ARE AFFECTED BY PLATELET DEPLETION
INDEPENDENTLY OF HIGH VIRAL
TITERS.......................................................................................................................................................................61
SPLENIC NECROSIS IN PLATELET-‐DEPLETED MICE AFFECTS
INNATE AND ADAPTIVE IMMUNE
COMPONENTS...........................................................................................................................................................62
PLATELET DEPLETION DURING LCMV INFECTION DISRUPTS THE SPLENIC
ARCHITECTURE ...................63
THROMBOPOIETIN TREATMENT DOES NOT IMPROVE CHRONIC LCMV VIRAL
CLEARANCE......................64
CONTROL OF VSV INFECTION IS ALSO AFFECTED IN THE ABSENCE OF
PLATELETS....................................64
FIGURES....................................................................................................................................................................66
Figure 1. Approximately 15% of the total platelet count is
sufficient to prevent lethality
and peripheral organ hemorrhage during LCMV Armstrong
infection.....................................66
Figure 2. Partially platelet-depleted mice fail to control
an acute LCMV Armstrong
infection and have exhausted LCMV-specific CD8+ T cell
responses...........................................71
Figure 3. Platelet removal in the absence of infection does not
affect the blood and
secondary lymphoid organ (SLO)
compartments................................................................................75
Figure 4. Early control of the virus is affected by partial
platelet depletion independent of
type I IFN production.
......................................................................................................................................79
Figure 5. CD8 T cell responses are directly affected by partial
platelet depletion
independent of the levels of circulating viral antigen.
......................................................................84
Figure 6. Reduced innate and adaptive immune cell populations in
spleens of platelet-
depleted infected animals correlates with an increase of necrotic
splenocytes.....................89
Figure 7. Organization of the splenic structure is disrupted by
the LCMV infection in
platelet-depleted mice.
....................................................................................................................................94
Figure 8. Vesicular Stomatitis virus (VSV) infection is also
affected by the partial
depletion of
platelets........................................................................................................................................99
CHAPTER 5: DISCUSSION
................................................................................................................103
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