scholarly journals Selection at Multiple Checkpoints Focuses VH12 B Cell Differentiation toward a Single B-1 Cell Specificity

1999 ◽  
Vol 190 (7) ◽  
pp. 903-914 ◽  
Author(s):  
Calin Tatu ◽  
Jian Ye ◽  
Larry W. Arnold ◽  
Stephen H. Clarke
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
High Frequency ◽  
Clonal Expansion ◽  
Selective Advantage ◽  
B Cell Differentiation ◽  
Cell Specificity ◽  
Selective Elimination

Phosphatidyl choline (PtC)-specific B cells segregate to the B-1 subset, where they comprise up to 10% of the B-1 repertoire. About half express VH12 and Vκ4/5H and are restricted in VHCDR3. We have previously reported that anti-PtC VHCDR3 is enriched among VH12-expressing cells by selective elimination of pre-B cells. We report here a bias for Vκ4/5H expression among VH12-expressing B cells, even among those that do not bind PtC and are not B-1. This is due in part to an inability of VH12 to associate with many light (L) chains but must also be due to a selective advantage in survival or clonal expansion in the periphery for Vκ4/5H-expressing cells. Thus, the bias for Vκ4/5H expression is independent of PtC binding, and, as segregation to B-1 occurs after Ig gene expression, it precedes segregation to the B-1 subset. In 6-1 mice, splenic B-1 cells reside in follicles but segregate to follicles distinct from those that contain B-2 cells. These data indicate that selection at multiple developmental checkpoints ensures the co-expression of an anti-PtC VHCDR3 and L chain in a high frequency of VH12 B cells. This focus toward specificity for PtC facilitates the development of a large anti-PtC B-1 repertoire.

Gene Expression in Leukemic Blasts Persisting at Day 8 of Induction Therapy in Childhood ALL Displays a Common Shift towards Terminally Differentiated B Cells and a Cytoreduction-Associated Impairment of the Translational Machinery.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 537-537
Author(s):  
Peter Rhein ◽  
Stefanie Scheid ◽  
Richard Ratei ◽  
Christian Hagemeier ◽  
Karl Seeger ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Induction Therapy ◽  
Peripheral Blood ◽  
Therapy Resistance ◽  
B Cell Differentiation ◽  
Translational Machinery ◽  
Blast Cells

Abstract In childhood acute lymphoblastic leukemia (ALL), persistence of leukemic blasts during therapy is of crucial prognostic significance. To approach the mechanisms of therapy resistance, we addressed genome-wide gene expression in blasts persisting after one week of induction therapy (day 8 blasts) and their molecular signatures as compared with blast cells at initial diagnosis (day 0 blasts). In order to approach this issue experimentally, a procedure has been established including flow sorting of leukemic blasts by their leukemia-associated immunophenotype and preparation of cRNA, starting from a small number of cells. Blast cells from 12 patients with precursor B-cell ALL were investigated using Affymetrix HG U133A microarrays, and genes commonly up- or down-regulated in blast cells under therapy were identified in matched pairs of day 8 and day 0 samples. In spite of the heterogeneous clinical features of the patients (mean rate of cytoreduction after 7 days of initial therapy = 82%, range between 33% and 99%), we were able to determine a set of 310 genes whose expression was commonly changed between day 8 and day 0 with an estimated false discovery rate of 0.05. The identified set of genes indicated inhibited cell cycling, reduced metabolism, and expression changes of multiple factors related to B-cell differentiation. These changes collectively suggested that gene expression in day 8 blasts is shifted towards resting mature B cells. To test this hypothesis, we isolated normal B cells from peripheral blood samples of leukemic patients and compared their gene expression to that of leukemic blasts using Principal Component Analysis (PCA). PCA revealed that day 8 samples are positioned between day 0 samples and normal B-cell samples, and statistical significance of this observation could be established using the Jonckheere-Terpstra test. Changes of B-cell differentiation markers on protein level supported this finding. In addition, we analyzed all genes with regard to the correlation of their expression changes with the rates of cytoreduction in peripheral blood. We observed differential impairment of the key components of the translational machinery including ribosome, eukaryotic 43S preinitiation complex and eukaryotic 48S initiation complex. Overall, expression levels of these factors decreased in therapy-sensitive patients but did not change in therapy-resistant patients. Taken together, investigation of leukemia cells persisting during therapy identifies common and individual expression changes which may potentially affect sensitivity towards anti-leukemic agents and offers new insights into the mechanisms of therapy resistance in ALL.

scholarly journals An IRF4-MYC-mTORC1 integrated pathway controls cell growth and the proliferative capacity of activated B cells during B cell differentiation in vivo

2021 ◽  
Author(s):  
Dillon G Patterson ◽  
Anna K Kania ◽  
Madeline J Price ◽  
James R Rose ◽  
Christopher D Scharer ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
B Cells ◽  
Cell Growth ◽  
B Cell ◽  
Proliferative Response ◽  
Cell Activation ◽  
B Cell Differentiation ◽  
B Cell Activation

Cell division is an essential component of B cell differentiation to antibody-secreting plasma cells, with critical reprogramming occurring during the initial stages of B cell activation. However, a complete understanding of the factors that coordinate early reprogramming events in vivo remain to be determined. In this study, we examined the initial reprogramming by IRF4 in activated B cells using an adoptive transfer system and mice with a B cell-specific deletion of IRF4. IRF4-deficient B cells responding to influenza, NP-Ficoll and LPS divided, but stalled during the proliferative response. Gene expression profiling of IRF4-deficient B cells at discrete divisions revealed IRF4 was critical for inducing MYC target genes, oxidative phosphorylation, and glycolysis. Moreover, IRF4-deficient B cells maintained an inflammatory gene expression signature. Complementary chromatin accessibility analyses established a hierarchy of IRF4 activity and identified networks of dysregulated transcription factor families in IRF4-deficient B cells, including E-box binding bHLH family members. Indeed, B cells lacking IRF4 failed to fully induce Myc after stimulation and displayed aberrant cell cycle distribution. Furthermore, IRF4-deficient B cells showed reduced mTORC1 activity and failed to initiate the B cell-activation unfolded protein response and grow in cell size. Myc overexpression in IRF4-deficient was sufficient to overcome the cell growth defect. Together, these data reveal an IRF4-MYC-mTORC1 relationship critical for controlling cell growth and the proliferative response during B cell differentiation.

EBV MicroRNA Expression in Virus Driven B-Cell Differentiation and Lymphomagenesis.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 93-93
Author(s):  
Jamie P Nourse ◽  
Pauline Crooks ◽  
Do Nguyen Van ◽  
Kimberley Jones ◽  
Nathan Ross ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
Phase 1 ◽  
Differentiation Process ◽  
B Cell Differentiation ◽  
B Cell Lymphomas

Abstract Abstract 93 Lymphomagenesis is a complex process, in part reflecting the nature of the transforming event, as well as the developmental stage of the cell. In the B-cell differentiation represents a continuum that is initiated when a naïve B-cell encounters antigen, undergoes a germinal centre (GC) reaction and ends with terminal differentiation into either a memory or plasma B-cell. Interruption of this process by a transforming event may result in a clonal proliferation where differentiation of the cell is blocked at this stage. The majority of B-cell lymphomas are derived from GC or post-GC B-cells. As physiologically relevant human models that emulate the various stages of B-cell differentiation are lacking we rationalized that in-vitro utilization of the B-cell lymphotrophic Epstein-Barr virus (EBV) would provide insights into this process. In one scenario, EBV infects naïve B-cells and drives a differentiation process paralleling the GC reaction through a well-characterized series of latency gene expression programs. EBV is also implicated in a range of GC and post-GC derived B-cell lymphomas (including Burkitt's, Hodgkin's, PTLD and DLBCL). Using high efficiency EBV infection of isolated naïve B-cells from EBV seronegative subjects, we have demonstrated that EBV infection provides a highly relevant in-vitro model that accurately reflects three distinct phases in the GC differentiation process. Alterations in the expression of a broad range of genes associated with the differentiation of the naïve B-cell were observed within 24 hours of infection and within four days of infection a process exhibiting many similarities to the GC reaction had taken place. These included BCL6, the levels of which were rapidly down-regulated within 24 hours indicating activation of the naïve B-cell. Levels of the memory cell marker CD27 steadily increased over 24 to 96 hours, while BLIMP1 expression increased, peaking at 48 hours. An increase in AID expression over 8 to 48 hours was consistent with somatic hypermutation and isotype switching. Finally a dramatic elevation in expression of the GC associated oncogene LMO2 was observed after two days followed by an equally dramatic downregulation after two weeks. Within two weeks of infection (phase 1), B-cells progressed through a GC-like phase followed by a one week transition state (phase 2) after which continued culture resulted in further differentiation to cells with the phenotypic hallmarks of post-GC cells (phase 3). MicroRNAs (miRNAs) are small non-coding RNAs, which act as negative regulators of gene expression. miRNA expression reflects the developmental lineage and differentiation state of several human cancers and over-expression is implicated in lymphomagenesis. They are also associated with the development of the GC reaction. EBV expresses at least 39 unique miRNAs from the BART and BHRF1 clusters within the viral genome. These EBV miRNAs are differentially expressed in tumour cell lines, suggesting roles during EBV-driven B-cell differentiation and lymphomagenesis. The relationship between EBV miRNAs and the kinetics of EBV driven B-cell differentiation has not been characterized. In our model we find distinct miRNA expression kinetics, coincidental with gene expression changes during B-cell differentiation, suggesting that these regulatory molecules may be involved in the GC process. Although a small number of EBV miRNAs were expressed at low levels early in the GC-like phase 1, the majority were up-regulated during the transition phase 2, exhibiting a subsequent partial down-regulation in the post-GC-like phase 3. The three phases were coincident with differential BART and BHRF1 promoter usage and alternate splicing. Strikingly, application of the infection model to primary patient samples and lymphoma cell-lines revealed that lymphomas clustered within distinct phases, reflecting the full continuum of the B-cell differentiation process. Interestingly, the majority of PTLD samples clustered within the transition phase, whereas Burkitt's and Hodgkin's lymphoma sample segregated with the GC stage. Application of our gene expression and miRNA data to cell-lines and a range of GC and post-GC EBV-positive lymphomas of various histological types indicate that our B-cell differentiation model can be used to accurately classify B-cell lymphomas in a physiologically relevant manner according to the stage of arrested B-cell differentiation. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Molecular definition of the germinal centre stage of B–cell differentiation

2001 ◽  
Vol 356 (1405) ◽  
pp. 83-89 ◽  
Author(s):  
Chi Ma ◽  
Louis M. Staudt
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Expression Analysis ◽  
Peripheral Blood ◽  
Gene Expression Analysis ◽  
Gene Expression Signature ◽  
Germinal Centre ◽  
B Cell Differentiation

Genomic–scale gene expression analysis provides views of biological processes as a whole that are difficult to obtain using traditional single–gene experimental approaches. In the case of differentiating systems, gene expression profiling can define a stage of differentiation by the characteristic expression of hundreds of genes. Using specialized DNA microarrays termed ‘Lymphochips’, gene expression during mature B–cell differentiation has been defined. Germinal centre B cells represent a stage of differentiation that can be defined by a gene expression signature that is not shared by other highly proliferative B–cell populations such as mitogenically activated peripheral blood B cells. The germinal centre gene expression signature is maintained to a significant degree in lymphoma cell lines derived from this stage of differentiation, demonstrating that this gene expression programme does not require ongoing interactions with other germinal centre cell types. Analysis of representative cDNA libraries prepared from resting and activated peripheral blood B cells, germinal centre centroblasts, centrocytes and tonsillar memory B cells has confirmed and extended the results of DNA microarray gene expression analysis.

Gene expression profiling of plasma cells and plasmablasts: toward a better understanding of the late stages of B-cell differentiation

Blood ◽  
2003 ◽  
Vol 102 (2) ◽  
pp. 592-600 ◽  
Author(s):  
Karin Tarte ◽  
Fenghuang Zhan ◽  
John De Vos ◽  
Bernard Klein ◽  
John Shaughnessy
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Plasma Cells ◽  
Close Contact ◽  
Expression Profiles ◽  
Principal Component ◽  
B Cell Differentiation

AbstractPlasma cells (PCs), the end point of B-cell differentiation, are a heterogeneous cell compartment comprising several cell subsets from short-lived highly proliferative plasmablasts to long-lived nondividing fully mature PCs. Whereas the major transcription factors driving the differentiation of B cells to PCs were recently identified, the subtle genetic changes that underlie the transition from plasmablasts to mature PCs are poorly understood. We recently described an in vitro model making it possible to obtain a large number of cells with the morphologic, phenotypic, and functional characteristics of normal polyclonal plasmablastic cells (PPCs). Using Affymetrix microarrays we compared the gene expression profiles of these PPCs with those of mature PCs isolated from tonsils (TPCs) and bone marrow (BMPCs), and with those of B cells purified from peripheral blood (PBB cells) and tonsils (TBCs). Unsupervised principal component analysis clearly distinguished the 5 cell populations on the basis of their differentiation and proliferation status. Detailed statistical analysis allowed the identification of 85 PC genes and 40 B-cell genes, overexpressed, respectively, in the 3 PC subsets or in the 2 B-cell subsets. In addition, several signaling molecules and antiapoptotic proteins were found to be induced in BMPCs compared with PPCs and could be involved in the accumulation and prolonged survival of BMPCs in close contact with specialized stromal microenvironment. These data should help to better understand the molecular events that regulate commitment to a PC fate, mediate PC maintenance in survival niches, and could facilitate PC immortalization in plasma cell dyscrasias.

AB0144 STRATIFICATION OF PATIENTS WITH PRIMARY SJÖGREN’S SYNDROME BY MEASURING B-CELL HEALTH

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1372-1373
Author(s):  
G. M. Verstappen ◽  
J. C. Tempany ◽  
H. Cheon ◽  
A. Farchione ◽  
S. Downie-Doyle ◽  
...  
Keyword(s):  
Cell Division ◽  
Cell Differentiation ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
B Cell Differentiation ◽  
Research Support ◽  
Differentiation Capacity ◽  
Cell Responses ◽  
Healthy Donors

Background:Primary Sjögren’s syndrome (pSS) is a heterogeneous immune disorder with broad clinical phenotypes that can arise from a large number of genetic, hormonal, and environmental causes. B-cell hyperactivity is considered to be a pathogenic hallmark of pSS. However, whether B-cell hyperactivity in pSS patients is a result of polygenic, B cell-intrinsic factors, extrinsic factors, or both, is unclear. Despite controversies about the efficacy of rituximab, new B-cell targeting therapies are under investigation with promising early results. However, for such therapies to be successful, the etiology of B-cell hyperactivity in pSS needs to be clarified at the individual patient level.Objectives:To measure naïve B-cell function in pSS patients and healthy donors using quantitative immunology.Methods:We have developed standardised, quantitative functional assays of B-cell responses that measure division, death, differentiation and isotype switching, to reveal the innate programming of B cells in response to T-independent and dependent stimuli. This novel pipeline to measure B-cell health was developed to reveal the sum total of polygenic defects and underlying B-cell dysfunction at an individual level. For the current study, 25 pSS patients, fulfilling 2016 ACR-EULAR criteria, and 15 age-and gender-matched healthy donors were recruited. Standardized quantitative assays were used to directly measure B cell division, death and differentiation in response to T cell-independent (anti-Ig + CpG) and T-cell dependent (CD40L + IL-21) stimuli. Naïve B cells (IgD+CD27-) were sorted from peripheral blood mononuclear cells and were labeled with Cell Trace Violet at day 0 to track cell division until day 6. B cell differentiation was measured at day 5.Results:Application of our standardized assays, and accompanying parametric models, allowed us to study B cell-intrinsic defects in pSS patients to a range of stimuli. Strikingly, we demonstrated a hyperresponse of naïve B cells to combined B cell receptor (BCR) and Toll-like receptor (TLR)-9 stimulation in pSS patients. This hyperresponse was revealed by an increased mean division number (MDN) at day 5 in pSS patients compared with healthy donors (p=0.021). A higher MDN in pSS patients was observed at the cohort level and was likely attributed to an increased division burst (division destiny) time. The MDN upon BCR/TLR-9 stimulation correlated with serum IgG levels (rs=0.52; p=0.011). No difference in MDN of naïve B cells after T cell-dependent stimulation was observed between pSS patients and healthy donors. B cell differentiation capacity (e.g., plasmablast formation and isotype switching) after T cell-dependent stimulation was also assessed. At the cohort level, no difference in differentiation capacity between groups was observed, although some pSS patients showed higher plasmablast frequencies than healthy donors.Conclusion:Here, we demonstrate defects in B-cell responses both at the cohort level, as well as individual signatures of defective responses. Personalized profiles of B cell health in pSS patients reveal a group of hyperresponsive patients, specifically to combined BCR/TLR stimulation. These patients may benefit most from B-cell targeted therapies. Future studies will address whether profiles of B cell health might serve additional roles, such as prediction of disease trajectories, and thus accelerate early intervention and access to precision therapies.Disclosure of Interests:Gwenny M. Verstappen: None declared, Jessica Catherine Tempany: None declared, HoChan Cheon: None declared, Anthony Farchione: None declared, Sarah Downie-Doyle: None declared, Maureen Rischmueller Consultant of: Abbvie, Bristol-Meyer-Squibb, Celgene, Glaxo Smith Kline, Hospira, Janssen Cilag, MSD, Novartis, Pfizer, Roche, Sanofi, UCB, Ken R. Duffy: None declared, Frans G.M. Kroese Grant/research support from: Unrestricted grant from Bristol-Myers Squibb, Consultant of: Consultant for Bristol-Myers Squibb, Speakers bureau: Speaker for Bristol-Myers Squibb, Roche and Janssen-Cilag, Hendrika Bootsma Grant/research support from: Unrestricted grants from Bristol-Myers Squibb and Roche, Consultant of: Consultant for Bristol-Myers Squibb, Roche, Novartis, Medimmune, Union Chimique Belge, Speakers bureau: Speaker for Bristol-Myers Squibb and Novartis., Philip D. Hodgkin Grant/research support from: Medimmune, Vanessa L. Bryant Grant/research support from: CSL

scholarly journals Cutting Edge: Polycomb Gene Expression Patterns Reflect Distinct B Cell Differentiation Stages in Human Germinal Centers

2000 ◽  
Vol 164 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Frank M. Raaphorst ◽  
Folkert J. van Kemenade ◽  
Elly Fieret ◽  
Karien M. Hamer ◽  
David P. E. Satijn ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
B Cell ◽  
Expression Patterns ◽  
Germinal Centers ◽  
Cutting Edge ◽  
Gene Expression Patterns ◽  
B Cell Differentiation

scholarly journals YY1 plays an essential role at all stages of B-cell differentiation

2016 ◽  
Vol 113 (27) ◽  
pp. E3911-E3920 ◽  
Author(s):  
Eden Kleiman ◽  
Haiqun Jia ◽  
Salvatore Loguercio ◽  
Andrew I. Su ◽  
Ann J. Feeney
Keyword(s):  
Transcription Factor ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Signaling Pathways ◽  
Mrna Splicing ◽  
Cell Populations ◽  
Sequencing Analysis ◽  
B Cell Differentiation ◽  
Chip Sequencing

Ying Yang 1 (YY1) is a ubiquitously expressed transcription factor shown to be essential for pro–B-cell development. However, the role of YY1 in other B-cell populations has never been investigated. Recent bioinformatics analysis data have implicated YY1 in the germinal center (GC) B-cell transcriptional program. In accord with this prediction, we demonstrated that deletion of YY1 by Cγ1-Cre completely prevented differentiation of GC B cells and plasma cells. To determine if YY1 was also required for the differentiation of other B-cell populations, we deleted YY1 with CD19-Cre and found that all peripheral B-cell subsets, including B1 B cells, require YY1 for their differentiation. Transitional 1 (T1) B cells were the most dependent upon YY1, being sensitive to even a half-dosage of YY1 and also to short-term YY1 deletion by tamoxifen-induced Cre. We show that YY1 exerts its effects, in part, by promoting B-cell survival and proliferation. ChIP-sequencing shows that YY1 predominantly binds to promoters, and pathway analysis of the genes that bind YY1 show enrichment in ribosomal functions, mitochondrial functions such as bioenergetics, and functions related to transcription such as mRNA splicing. By RNA-sequencing analysis of differentially expressed genes, we demonstrated that YY1 normally activates genes involved in mitochondrial bioenergetics, whereas it normally down-regulates genes involved in transcription, mRNA splicing, NF-κB signaling pathways, the AP-1 transcription factor network, chromatin remodeling, cytokine signaling pathways, cell adhesion, and cell proliferation. Our results show the crucial role that YY1 plays in regulating broad general processes throughout all stages of B-cell differentiation.

scholarly journals Optimized Protocols for in Vitro T Cell-Dependent and T Cell-Independent Activation for B Cell Differentiation Studies Using Limited Cells

2021 ◽  
Author(s):  
Casper Marsman ◽  
Dorit Verhoeven
Keyword(s):  
Cell Differentiation ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Plasma Cells ◽  
Cell Formation ◽  
B Cell Differentiation ◽  
Differentiation Potential ◽  
Human B Cell

Background/methods: For mechanistic studies, in vitro human B cell differentiation and generation of plasma cells are invaluable techniques. However, the heterogeneity of both T cell-dependent (TD) and T cell-independent (TI) stimuli and the disparity of culture conditions used in existing protocols makes interpretation of results challenging. The aim of the present study was to achieve the most optimal B cell differentiation conditions using isolated CD19+ B cells and PBMC cultures. We addressed multiple seeding densities, different durations of culturing and various combinations of TD stimuli and TI stimuli including B cell receptor (BCR) triggering. B cell expansion, proliferation and differentiation was analyzed after 6 and 9 days by measuring B cell proliferation and expansion, plasmablast and plasma cell formation and immunoglobulin (Ig) secretion. In addition, these conditions were extrapolated using cryopreserved cells and differentiation potential was compared. Results: This study demonstrates improved differentiation efficiency after 9 days of culturing for both B cell and PBMC cultures using CD40L and IL-21 as TD stimuli and 6 days for CpG and IL-2 as TI stimuli. We arrived at optimized protocols requiring 2500 and 25.000 B cells per culture well for TD and TI assays, respectively. The results of the PBMC cultures were highly comparable to the B cell cultures, which allows dismissal of additional B cell isolation steps prior to culturing. In these optimized TD conditions, the addition of anti-BCR showed little effect on phenotypic B cell differentiation, however it interferes with Ig secretion measurements. Addition of IL-4 to the TD stimuli showed significantly lower Ig secretion. The addition of BAFF to optimized TI conditions showed enhanced B cell differentiation and Ig secretion in B cell but not in PBMC cultures. With this approach, efficient B cell differentiation and Ig secretion was accomplished when starting from fresh or cryopreserved samples. Conclusion: Our methodology demonstrates optimized TD and TI stimulation protocols for more indepth analysis of B cell differentiation in primary human B cell and PBMC cultures while requiring low amounts of B cells, making them ideally suited for future clinical and research studies on B cell differentiation of patient samples from different cohorts of B cell-mediated diseases.

scholarly journals Conserved gammaherpesvirus protein kinase counters the antiviral effects of myeloid cell specific STAT1 expression to promote the establishment of splenic B cell latency.

2021 ◽  
Author(s):  
P. A. Sylvester ◽  
C. N. Jondle ◽  
K. P. Stoltz ◽  
J. Lanham ◽  
B. N. Dittel ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
Protein Kinase ◽  
B Cell ◽  
Latent Reservoir ◽  
Type I ◽  
B Cell Differentiation ◽  
Cell Type ◽  
Antiviral Effects ◽  
Cell Type Specific

Gammaherpesviruses establish life-long infections and are associated with B cell lymphomas. Murine gammaherpesvirus-68 (MHV68) infects epithelial and myeloid cells during acute infection, with subsequent passage of the virus to B cells, where physiological B cell differentiation is usurped to ensure the establishment of chronic latent reservoir. Interferons (IFNs) represent a major antiviral defense system that engages transcriptional factor STAT1 to attenuate diverse acute and chronic viral infections, including those of gammaherpesviruses. Correspondingly, global deficiency of type I or type II IFN signaling profoundly increases the pathogenesis of acute and chronic gammaherpesvirus infection, compromises host survival, and impedes mechanistic understanding of cell type-specific role of IFN signaling. Here we demonstrate that myeloid-specific STAT1 deficiency attenuates acute and persistent MHV68 replication in the lungs and suppresses viral reactivation from peritoneal cells, without any effect on the establishment of viral latent reservoir in splenic B cells. All gammaherpesviruses encode a conserved protein kinase that antagonizes type I IFN signaling in vitro. Here, we show that myeloid-specific STAT1 deficiency rescues the attenuated splenic latent reservoir of kinase null MHV68 mutant. However, despite having gained access to splenic B cells, protein kinase null MHV68 mutant fails to drive B cell differentiation. Thus, while myeloid-intrinsic STAT1 expression must be counteracted by the gammaherpesvirus protein kinase to facilitate viral passage to splenic B cells, expression of the viral protein kinase continues to be required to promote optimal B cell differentiation and viral reactivation, highlighting the multifunctional nature of this conserved viral protein during chronic infection. Importance. IFN signaling is a major antiviral system of the host that suppresses replication of diverse viruses, including acute and chronic gammaherpesvirus infection. STAT1 is a critical member and the primary antiviral effector of IFN signaling pathways. Given the significantly compromised antiviral status of global type I or type II IFN deficiency, unabated gammaherpesvirus replication and pathogenesis hinders understanding of cell type-specific antiviral effects. In this study, a mouse model of myeloid-specific STAT1 deficiency unveiled site-specific antiviral effects of STAT1 in the lungs and peritoneal cavity, but not spleen of chronically infected hosts. Interestingly, expression of a conserved gammaherpesvirus protein kinase was required to counteract the antiviral effects of myeloid-specific STAT1 expression to facilitate latent infection of splenic B cells, revealing a cell-type specific virus-host antagonism during the establishment of chronic gammaherpesvirus infection.

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