M2 and Blimp-1: Studies in Murine Gammaherpesvirus 68Pathogenesis and B cell Biology Open Access

Siegel, Andrea Michelle (2009)

Permanent URL: https://etd.library.emory.edu/concern/etds/bg257f63c?locale=en
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Abstract

M2 and Blimp-1: Studies in Murine Gammaherpesvirus 68 Pathogenesis and B cell Biology By Andrea Michelle Siegel

Gammaherpesviruses establish life-long infections in lymphcytes and are associated with a variety of lymphomas and carcinomas. The murine gammaherpesvirus68 (MHV68), which naturally infects wild murid rodents, has emerged as a model pathogen to study latency and reactivation in vivo. MHV68 latently infects B cells, dendritic cells, and macrophages; the long-term latency reservoir is the memory B cell. This thesis explores the role of B cells in MHV68 latency from both the pathogen and host viewpoint. Firstly, I examined how M2, a latency-associated MHV68 gene product, manipulates B cell biology to enable MHV68 to establish and reactivate from latency. I demonstrate that M2 expression in primary murine B cells leads to B cell proliferation, survival, and differentiation into an activated, pre-plasma memory B cell phenotype. M2-driven proliferation is dependent on IL-10, and M2 expression during MHV68 infection is associated with a significant increase in serum IL-10 levels at the onset of latency. Secondly, I studied the role of B-lymphocyte induced maturation protein-1 (Blimp-1), the master transcriptional regulator of plasma cell differentiation, in MHV68 pathogenesis in vivo. I observed that Blimp-1 expression in infected cells plays a significant role in the establishment of latency and reactivation from latency. Additionally, Blimp-1 expression in splenocytes is needed for the maintenance of MHV68 long-term latency. Together, these studies of M2 and Blimp-1 demonstrate how the biology of the B cell is intertwined with MHV68 pathogenesis.

Table of Contents

TABLE OF CONTENTS Chaper I:

Introduction...1 Gammaherpesviruses: lymphotropic viruses...1 Murine Gammaherpesvirus68 as a model pathogen...3 Murine Gammaherpesvirus68 and B cells...4 Manipulation of B cells by Gammaherpesviruses...6 M2: a latency-associated Murine Gammaherpesvirus68 Protein...8 Plasma B cell Differentiation...14 Blimp-1: master transcriptional regulator of plasma cell development...16 Plasma cells and gammaherpesvirus reactivation...20 Figures...23 Figure Legends...26

Chaper II: The MHV68 M2 protein drives IL-10 dependent B cell proliferation and differentiation

Introduction...28 Materials and Methods...32 Results MHV68 M2 protein augments LPS-driven B cell proliferation...39 M2 protein expression leads to B cell differentiation...42 M2 protein expression leads to secretion of IL-10...44 IL-10 is required for the M2-driven B cell proliferation...45 Loss of M2 protein expression during MHV68 infection results in a significant reduction in serum IL-10 levels...48 Loss of M2 expression during MHV68 infection correlates with an increase in virus-specific, activated CD8+ T cells...49 Discussion...51 Figures...59 Figure Legends...66

Chaper III: Blimp-1 expression is necessary for the maintenance of Murine Gammaherpesvirus68 latency

Introduction...73 Materials and Methods...78 Results Blimp-1 expression is dispensable for lytic replication in the spleen...83 Blimp-1 expression is necessary for the efficient establishment of latency in the spleen...84 Mice deficient in plasma cells exhibit a decrease in the establishment of, and reactivation from, splenic latency in vivo...85 B cell responses to MHV68 are diminished in the absence of Blimp-1...88 Vβ4+ CD8+ T cells expand to wild-type levels in the absence of Blimp-1...89 Blimp-1 is necessary for the prolonged antibody response to MHV68 in vivo...90 Loss of Blimp-1 expression in infected splenocytes leads to a significant decrease in latency at day 90 post-infection...91 Discussion...93 Figures and Table...98 Figure Legends...106

Chapter IV: Summary, Future Directions, and Conclusions

M2 and IL-10...110 Blimp-1 and Murine Gammaherpesvirus68 Pathogenesis...115 Conclusions...119

References...121

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