scholarly journals B Cell-Intrinsic Expression of Interferon Regulatory Factor 1 Supports Chronic Murine Gammaherpesvirus 68 Infection

2020 ◽  
Vol 94 (13) ◽  
Author(s):  
C. N. Jondle ◽  
K. E. Johnson ◽  
A. A. Uitenbroek ◽  
P. A. Sylvester ◽  
C. Nguyen ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Chronic Infection ◽  
Latent Reservoir ◽  
B Cell Differentiation ◽  
B Cell Lymphomas ◽  
Murine Gammaherpesvirus ◽  
Gammaherpesvirus 68 ◽  
Murine Gammaherpesvirus 68

ABSTRACT Gammaherpesviruses are ubiquitous pathogens that are associated with cancers, including B cell lymphomas. These viruses are unique in that they infect naive B cells and subsequently drive a robust polyclonal germinal center response in order to amplify the latent reservoir and to establish lifelong infection in memory B cells. The gammaherpesvirus-driven germinal center response in combination with robust infection of germinal center B cells is thought to precipitate lymphomagenesis. Importantly, host and viral factors that selectively affect the gammaherpesvirus-driven germinal center response remain poorly understood. Global deficiency of antiviral tumor-suppressive interferon regulatory factor 1 (IRF-1) selectively promotes the murine gammaherpesvirus 68 (MHV68)-driven germinal center response and expansion of the viral latent reservoir. To determine the extent to which antiviral effects of IRF-1 are B cell intrinsic, we generated mice with conditional IRF-1 deficiency. Surprisingly, B cell-specific IRF-1 deficiency attenuated the establishment of chronic infection and the germinal center response, indicating that MHV68 may, in a B cell-intrinsic manner, usurp IRF-1 to promote the germinal center response and expansion of the latent reservoir. Further, we found that B cell-specific IRF-1 deficiency led to reduced levels of active tyrosine phosphatase SHP1, which plays a B cell-intrinsic proviral function during MHV68 infection. Finally, results of this study indicate that the antiviral functions of IRF-1 unveiled in MHV68-infected mice with global IRF-1 deficiency are mediated via IRF-1 expression by non-B cell populations. IMPORTANCE Gammaherpesviruses establish lifelong infection in over 95% of all adults and are associated with B cell lymphomas. The virus’s manipulation of the germinal center response and B cell differentiation to establish lifelong infection is thought to also precipitate malignant transformation, through a mechanism that remains poorly understood. The host transcription factor IRF-1, a well-established tumor suppressor, selectively attenuates MHV68-driven germinal center response, a phenotype that we originally hypothesized to occur in a B cell-intrinsic manner. In contrast, in testing, B cell-intrinsic IRF-1 expression promoted the MHV68-driven germinal center response and the establishment of chronic infection. Our report highlights the underappreciated multifaceted role of IRF-1 in MHV68 infection and pathogenesis.

scholarly journals Selective Gene Expression of Latent Murine Gammaherpesvirus 68 in B Lymphocytes

2003 ◽  
Vol 77 (13) ◽  
pp. 7308-7318 ◽  
Author(s):  
Sofia Marques ◽  
Stacey Efstathiou ◽  
K. G. Smith ◽  
Matthias Haury ◽  
J. Pedro Simas
Keyword(s):  
Gene Expression ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Critical Role ◽  
Murine Gammaherpesvirus ◽  
Virus Transcription ◽  
Gammaherpesvirus 68 ◽  
Murine Gammaherpesvirus 68 ◽  
Germinal Center B Cells

ABSTRACT Intranasal infection of mice with murine gammaherpesvirus 68 (MHV-68), a virus genetically related to the human pathogen Kaposi's sarcoma-associated herpesvirus, results in a persistent, latent infection in the spleen and other lymphoid organs. Here, we have determined the frequency of virus infection in splenic dendritic cells, macrophages, and several B-cell subpopulations, and we quantified cell type-dependent virus transcription patterns. The frequencies of virus genome positive cells were maximal at 14 days postinfection in all splenic cell populations analyzed. Marginal zone and germinal center B cells harbored the highest frequency of infection and the former population accounted for approximately half the total number of infected B cells. Analysis of virus transcription during the establishment of latency revealed that virus gene expression in B cells was restricted and dependent on the differentiation stage of the B cell. Notably, transcription of ORF73 was detected in germinal center B cells, a finding in agreement with the predicted latent genome maintenance function of ORF73 in dividing cells. At late times after infection, virus DNA could only be detected in newly formed and germinal center B cells, which suggests that B cells play a critical role in facilitating life-long latency.

The Alternative Breakpoint Region (ABR) of BCL6 Is An Active Transcribed Region in Germinal Center B Cells and May Serve as An Enhancer

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4465-4465
Author(s):  
Yulei Shen ◽  
Himabindu Ramachandrareddy ◽  
Wing C. Chan ◽  
Timothy McKeithan
Keyword(s):  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Regulatory Elements ◽  
Breakpoint Region ◽  
Luciferase Reporter ◽  
Regulatory Function ◽  
B Cell Differentiation ◽  
B Cell Lymphomas ◽  
Bcl6 Expression

Abstract Chromosomal translocations at 3q27 involving BCL6 occur in two different regions. Rearrangements with breaks within the major breakpoint region (MBR), comprising the first exon and part of the first intron of BCL6, are among the most common genetic abnormalities in of B-cell non-Hodgkin lymphoma, whereas breaks within an alternative breakpoint region (ABR), located between 245 and 285 kb 5′ to BCL6, have also been reported in follicular lymphoma grade and a small group (6.4%) of diffuse large B-cell lymphomas (DLBCLs). As a result of the MBR translocation, BCL6 expression is deregulated by promoter substitution with either immunoglobulin (Ig) genes or non-Ig genes as partners. A role for deregulated BCL6 expression in the pathogenesis of DLBCL has previously been confirmed in a mouse model. However, the biological role of the more distant ABR region is still not known. Using real-time PCR, we identified in the ABR region an evolutionarily conserved DNase I hypersensitive site (named Far5) which contains a conserved composite binding site for transcription factors PU.1 and IRF4, both of which play important roles in B-cell differentation. Further studies demonstrated that chromatin in the Far5 region, 190kb upstream of BCL6 promoter, has an open configuration in DHL6, Granta 519 and U266 cell lines. Far5 DNA showed enhancer activity by a luciferase reporter assay. PU.1 binds to Far5 in vivo (DHL16 cell line) by a chromatin immunoprecipitation (ChIP) assay, and PU.1 binds in vitro to the conserved PU.1/IRF composite site in Far5 synergistically with either IRF4 or IRF8. ChIP-on-chip assays showed Far5 histone H3K4 monomethylation, a chromatin modification associated with gene enhancers and other regulatory elements. In addition, we identified a transcript upstream of the Far5 region that is specifically expressed in germinal center (GC) B cells, but not at other stages of B-cell differentation. These results indicated that Far5 may play a role in selective expression of intergenic transcripts in GC B-cells. In other genes, intergenic transcription plays a role in looping between distal regulatory regions and the promoter. Our data showed that ABR region is constitutively active in GC B-cells and may play an important role in increasing BCL6 transcription when naïve B cells differentiate into GC B-cells. Further investigation of interactions between the ABR and the BCL6 promoter will uncover the regulatory function of the BCL6 ABR in B-cell differentiation and B-cell lymphomas.

scholarly journals Establishment and Maintenance of Long-Term Murine Gammaherpesvirus 68 Latency in B Cells in the Absence of CD40

2005 ◽  
Vol 79 (5) ◽  
pp. 2891-2899 ◽  
Author(s):  
David O. Willer ◽  
Samuel H. Speck
Keyword(s):  
B Cells ◽  
B Cell ◽  
Virus Replication ◽  
Receptor Expression ◽  
Cell Phenotype ◽  
Memory B Cell ◽  
Murine Gammaherpesvirus ◽  
Gammaherpesvirus 68 ◽  
Murine Gammaherpesvirus 68

ABSTRACT Murine gammaherpesvirus 68 (γHV68), like Epstein-Barr virus (EBV), establishes a chronic infection in its host by gaining access to the memory B-cell reservoir, where it persists undetected by the host's immune system. EBV encodes a membrane protein, LMP1, that appears to function as a constitutively active CD40 receptor, and is hypothesized to play a central role in EBV-driven differentiation of infected naive B cells to a memory B-cell phenotype. However, it has recently been shown that there is a critical role for CD40-CD40L interaction in B-cell immortalization by EBV (K.-I. Imadome, M. Shirakata, N. Shimizu, S. Nonoyama, and Y. Yamanashi, Proc. Natl. Acad. Sci. USA 100:7836-7840, 2003), indicating that LMP1 does not adequately recapitulate all of the necessary functions of CD40. The role of CD40 receptor expression on B cells for the establishment and maintenance of γHV68 latency is unclear. Data previously obtained with a competition model, demonstrated that in the face of CD40-sufficient B cells, γHV68 latency in CD40-deficient B cells waned over time in chimeric mice (I.-J. Kim, E. Flano, D. L. Woodland, F. E. Lund, T. D. Randall, and M. A. Blackman, J. Immunol. 171:886-892, 2003). To further investigate the role of CD40 in γHV68 latency in vivo, we have characterized the infection of CD40 knockout (CD40−/−) mice. Here we report that, consistent with previous observations, γHV68 efficiently established a latent infection in B cells of CD40−/− mice. Notably, unlike the infection of normal C57BL/6 mice, significant ex vivo reactivation from splenocytes harvested from infected CD40−/− mice 42 days postinfection was observed. In addition, in contrast to γHV68 infection of C57BL/6 mice, the frequency of infected naive B cells remained fairly stable over a 3-month period postinfection. Furthermore, a slightly higher frequency of γHV68 infection was observed in immunoglobulin D (IgD)-negative B cells, which was stably maintained over a period of 3 months postinfection. The presence of virus in IgD-negative B cells indicates that γHV68 may either directly infect memory B cells present in CD40−/− mice or be capable of driving differentiation of naive CD40−/− B cells. A possible explanation for the apparent discrepancy between the failure of γHV68 latency to be maintained in CD40-deficient B cells in the presence of CD40-sufficient B cells and the stable maintenance of γHV68 B-cell latency in CD40−/− mice came from examining virus replication in the lungs of infected CD40−/− mice, where we observed significantly higher levels of virus replication at late times postinfection compared to those in infected C57BL/6 mice. Taken together, these findings are consistent with a model in which chronic virus infection of CD40−/− mice is maintained through virus reactivation in the lungs and reseeding of latency reservoirs.

scholarly journals Role for MyD88 Signaling in Murine Gammaherpesvirus 68 Latency

2008 ◽  
Vol 82 (8) ◽  
pp. 3853-3863 ◽  
Author(s):  
Lisa M. Gargano ◽  
Janice M. Moser ◽  
Samuel H. Speck
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Response ◽  
Wild Type ◽  
Tlr Signaling ◽  
Murine Gammaherpesvirus ◽  
Gammaherpesvirus 68 ◽  
Murine Gammaherpesvirus 68 ◽  
B Cell Response

ABSTRACT Toll-like receptors (TLRs) are known predominantly for their role in activating the innate immune response. Recently, TLR signaling via MyD88 has been reported to play an important function in development of a B-cell response. Since B cells are a major latency reservoir for murine gammaherpesvirus 68 (MHV68), we investigated the role of TLR signaling in the establishment and maintenance of MHV68 latency in vivo. Mice deficient in MyD88 (MyD88−/−) or TLR3 (TLR3−/−) were infected with MHV68. Analysis of splenocytes recovered at day 16 postinfection from MyD88−/− mice compared to those from wild-type control mice revealed a lower frequency of (i) activated B cells, (ii) germinal-center B cells, and (iii) class-switched B cells. Accompanying this substantial defect in the B-cell response was an approximately 10-fold decrease in the establishment of splenic latency. In contrast, no defect in viral latency was observed in TLR3−/− mice. Analysis of MHV68-specific antibody responses also demonstrated a substantial decrease in the kinetics of the response in MyD88−/− mice. Analysis of wild-type × MyD88−/− mixed-bone-marrow chimeric mice demonstrated that there is a selective failure of MyD88−/− B cells to participate in germinal-center reactions as well as to become activated and undergo class switching. In addition, while MHV68 established latency efficiently in the MyD88-sufficient B cells, there was again a ca. 10-fold reduction in the frequency of MyD88−/− B cells harboring latent MHV68. This phenotype indicates that MyD88 is important for the establishment of MHV68 latency and is directly related to the role of MyD88 in the generation of a B-cell response. Furthermore, the generation of a B-cell response to MHV68 was intrinsic to B cells and was independent of the interleukin-1 receptor, a cytokine receptor that also signals through MyD88. These data provide evidence for a unique role for MyD88 in the establishment of MHV68 latency.

scholarly journals Ablation of STAT3 in the B Cell Compartment Restricts Gammaherpesvirus LatencyIn Vivo

mBio ◽  
2016 ◽  
Vol 7 (4) ◽  
Author(s):  
Sandeep Steven Reddy ◽  
Hui-Chen Chang Foreman ◽  
Thubten Ozula Sioux ◽  
Gee Ho Park ◽  
Valeria Poli ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Function ◽  
Acute Infection ◽  
Therapeutic Benefit ◽  
Therapeutic Interventions ◽  
Murine Gammaherpesvirus ◽  
Gammaherpesvirus 68 ◽  
Murine Gammaherpesvirus 68

ABSTRACTA challenging property of gammaherpesviruses is their ability to establish lifelong persistence. The establishment of latency in B cells is thought to involve active virus engagement of host signaling pathways. Pathogenic effects of these viruses during latency or following reactivation can be devastating to the host. Many cancers, including those associated with members of the gammaherpesvirus family, Kaposi’s sarcoma-associated herpesvirus and Epstein-Barr virus, express elevated levels of active host signal transducer and activator of transcription-3 (STAT3). STAT3 is activated by tyrosine phosphorylation in response to many cytokines and can orchestrate effector responses that include proliferation, inflammation, metastasis, and developmental programming. However, the contribution of STAT3 to gammaherpesvirus pathogenesis remains to be completely understood. This is the first study to have identified STAT3 as a critical host determinant of the ability of gammaherpesvirus to establish long-term latency in an animal model of disease. Following an acute infection, murine gammaherpesvirus 68 (MHV68) established latency in resident B cells, but establishment of latency was dramatically reduced in animals with a B cell-specific STAT3 deletion. The lack of STAT3 in B cells did not impair germinal center responses for immunoglobulin (Ig) class switching in the spleen and did not reduce either total or virus-specific IgG titers. Although ablation of STAT3 in B cells did not have a global effect on these assays of B cell function, it had long-term consequences for the viral load of the host, since virus latency was reduced at 6 to 8 weeks postinfection. Our findings establish host STAT3 as a mediator of gammaherpesvirus persistence.IMPORTANCEThe insidious ability of gammaherpesviruses to establish latent infections can have detrimental consequences for the host. Identification of host factors that promote viral latency is essential for understanding latency mechanisms and for therapeutic interventions. We provide the first evidence that STAT3 expression is needed for murine gammaherpesvirus 68 to establish latency in primary B cells during an active immune response to infection. STAT3 deletion in B cells does not impair adaptive immune control of the virus, but loss of STAT3 in B cells has a long-lasting impact on viral persistence. These results indicate a potential therapeutic benefit of STAT3 inhibitors for combating gammaherpesvirus latency and, thereby, associated pathologies.

scholarly journals B Cell-Intrinsic SHP1 Expression Promotes the Gammaherpesvirus-Driven Germinal Center Response and the Establishment of Chronic Infection

2019 ◽  
Vol 94 (1) ◽  
Author(s):  
K. E. Johnson ◽  
P. T. Lange ◽  
C. N. Jondle ◽  
P. J. Volberding ◽  
U. M. Lorenz ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Chronic Infection ◽  
Cell Activation ◽  
Tyrosine Phosphatase ◽  
Viral Latency ◽  
Negative Regulator ◽  
B Cell Differentiation

ABSTRACT Gammaherpesviruses are ubiquitous pathogens that establish lifelong infections in the majority of adults worldwide. Chronic gammaherpesvirus infection has been implicated in both lymphomagenesis and, somewhat controversially, autoimmune disease development. Pathogenesis is largely associated with the unique ability of gammaherpesviruses to usurp B cell differentiation, specifically, the germinal center response, to establish long-term latency in memory B cells. The host tyrosine phosphatase SHP1 is known as a brake on immune cell activation and is downregulated in several gammaherpesvirus-driven malignancies. However, here we demonstrate that B cell- but not T cell-intrinsic SHP1 expression supports the gammaherpesvirus-driven germinal center response and the establishment of viral latency. Furthermore, B cell-intrinsic SHP1 deficiency cooperated with gammaherpesvirus infection to increase the levels of double-stranded DNA-reactive antibodies at the peak of viral latency. Thus, in spite of decreased SHP1 levels in gammaherpesvirus-driven B cell lymphomas, B cell-intrinsic SHP1 expression plays a proviral role during the establishment of chronic infection, suggesting that the gammaherpesvirus-SHP1 interaction is more nuanced and is modified by the stage of infection and pathogenesis. IMPORTANCE Gammaherpesviruses establish lifelong infection in a majority of adults worldwide and are associated with a number of malignancies, including B cell lymphomas. These viruses infect naive B cells and manipulate B cell differentiation to achieve a lifelong infection of memory B cells. The germinal center stage of B cell differentiation is important as both an amplifier of the viral latent reservoir and the target of malignant transformation. In this study, we demonstrate that expression of tyrosine phosphatase SHP1, a negative regulator that normally limits the activation and proliferation of hematopoietic cells, enhances the gammaherpesvirus-driven germinal center response and the establishment of chronic infection. The results of this study uncover an intriguing beneficial interaction between gammaherpesviruses that are presumed to profit from B cell activation and a cellular phosphatase that is traditionally perceived to be a negative regulator of the same processes.

scholarly journals Lung Epithelial Cells Are a Major Site of Murine Gammaherpesvirus Persistence

1998 ◽  
Vol 187 (12) ◽  
pp. 1941-1951 ◽  
Author(s):  
James P. Stewart ◽  
Edward J. Usherwood ◽  
Alan Ross ◽  
Heather Dyson ◽  
Tony Nash
Keyword(s):  
B Cells ◽  
Epithelial Cells ◽  
B Cell ◽  
Virus Genome ◽  
Lung Epithelial Cells ◽  
Murine Gammaherpesvirus ◽  
Latently Infected ◽  
Gammaherpesvirus 68 ◽  
Murine Gammaherpesvirus 68 ◽  
Deficient Mice

It is currently believed that latently infected, resting B lymphocytes are central to gammaherpesvirus persistence, whereas mucosal epithelial cells are considered nonessential. We have readdressed the question of nonlymphoid persistence using murine gammaherpesvirus 68 (MHV-68). To dissect lymphoid from nonlymphoid persistence, we used μMT transgenic mice that are defective in B cells. MHV-68 DNA persisted in the lungs of intact and B cell–deficient mice. Both episomal and linear forms of the virus genome were present in lungs, implying the presence of both latency and productive replication. In situ hybridization for virus tRNA transcripts revealed latent MHV-68 in pulmonary epithelial cells. Infectious virus was recovered from the lungs of μMT mice after T cell depletion, showing that the persisting virus DNA was reactivatable. Finally, using adoptive transfer of B cells into B cell–deficient mice, it was shown that virus persisting in lungs seeded splenic B cells, and virus resident in the spleen seeded the lungs. These results show that mucosal epithelia can act as a nonlymphoid reservoir for gammaherpesvirus persistence, and that there is a two-way movement of virus between lymphoid and nonlymphoid compartments during persistence.

scholarly journals Gammaherpesvirus Usurps Host IL-17 Signaling To Support the Establishment of Chronic Infection

mBio ◽  
2021 ◽  
Vol 12 (2) ◽  
Author(s):  
C. N. Jondle ◽  
K. E. Johnson ◽  
C. Aurubin ◽  
P. Sylvester ◽  
G. Xin ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Fungal Infections ◽  
Lytic Replication ◽  
Latent Reservoir ◽  
Dependent Manner ◽  
B Cell Lymphomas ◽  
Germinal Center B Cells

ABSTRACT Gammaherpesviruses establish lifelong infection and are associated with a variety of cancers, including B cell lymphomas. These viruses manipulate the B cell differentiation process to establish lifelong infection in memory B cells. Specifically, gammaherpesviruses infect naive B cells and promote entry of both infected and uninfected naive B cells into germinal centers, where the virus usurps rapid proliferation of germinal center B cells to exponentially increase its cellular latent reservoir. In addition to facilitating the establishment of latent infection, germinal center B cells are thought to be the target of viral transformation. In this study, we have uncovered a novel proviral role of host interleukin 17A (IL-17A), a well-established antibacterial and antifungal factor. Loss of IL-17A signaling attenuated the establishment of chronic gammaherpesvirus infection and gammaherpesvirus-driven germinal center response in a route of inoculation-dependent manner. Further, IL-17A treatment directly supported gammaherpesvirus reactivation and de novo lytic infection. This study is the first demonstration of a multifaceted proviral role of IL-17 signaling. IMPORTANCE Gammaherpesviruses establish lifelong infections in a majority of humans and are associated with B cell lymphomas. IL-17A is a host cytokine that plays a well-established role in the clearance of bacterial and fungal infections; however, the role of IL-17A in viral infections is poorly understood. In this study, we show that IL-17A signaling promoted the establishment of chronic gammaherpesvirus infection following the mucosal route of infection, viral lytic replication, and reactivation from latency. Thus, our study unveils a novel proviral role of IL-17A signaling in gammaherpesvirus infection.

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