A dissertation on: Platelets, hemostasis, immunity, and pathogens: A conceptual understanding of their interactions. Open Access

Loria, David (2012)

Permanent URL: https://etd.library.emory.edu/concern/etds/z890rv14r?locale=en
Published

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

VHFs.........................................................................................................................................................................49
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

About this Dissertation

Rights statement
  • Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.
School
Department
Subfield / Discipline
Degree
Submission
Language
  • English
Research field
Keyword
Committee Chair / Thesis Advisor
Committee Members
Last modified

Primary PDF

Supplemental Files