Dr. Sumita  Bhaduri-Mcintosh  Md image

Dr. Sumita Bhaduri-Mcintosh Md

11 Stony Rd
Stony Brook NY 11790
631 441-1152
Medical School: Other - 1989
Accepts Medicare: No
Participates In eRX: No
Participates In PQRS: No
Participates In EHR: No
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NPI: 1952382251
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STAT3 Regulates Lytic Activation of Kaposi's Sarcoma-associated Herpesvirus. - Journal of virology
Lytic activation of Kaposi's Sarcoma-associated Herpesvirus (KSHV) from latency is a critical contributor to pathogenesis and progression of KSHV-mediated disease. Development of targeted treatment strategies and improvement of lytic phase-directed oncolytic therapies therefore hinge on gaining a better understanding of latency-to-lytic transition. A key observation in that regard, also common to other herpesviruses, is the partial permissiveness of latently-infected cells to lytic cycle inducing agents. Here, we address the molecular basis for why only some KSHV-infected cells respond to lytic stimuli. Since cellular Signal Transducer and Activator of Transcription 3 (STAT3) is overactive in KSHV-associated cancers, KSHV activates STAT3, and STAT3 has been found to regulate lytic activation of Epstein-Barr virus (EBV)-infected cells, we asked if STAT3 contributes similarly to the life cycle of KSHV. We found that high levels of STAT3 correlate with the refractory state at the single cell level under conditions of both spontaneous and induced lytic activation; importantly, STAT3 also regulates lytic susceptibility. Further, knockdown of STAT3 suppresses the cellular transcriptional co-repressor Krüppel-associated box domain-associated protein 1 (KAP1), and suppression of KAP1 activates lytic genes including the viral lytic switch RTA, thereby linking STAT3 via KAP1 to regulation of the balance between lytic and latent cells. These findings, taken together with those from EBV-infected, and more recently HSV-1-infected cells, cement the contribution of host STAT3 to persistence of herpesviruses, and simultaneously reveal an important lead to devise strategies to improve lytic phase-directed therapies for herpesviruses.Lytic activation of the cancer-causing Kaposi's Sarcoma-associated Herpesvirus (KSHV) is vital to its life cycle and causation of disease. Like other herpesviruses, however, a substantial fraction of latently-infected cells are resistant to lytic-inducing stimuli. Investigating the molecular basis for this refractory state is essential for understanding how the virus persists, how it causes disease, and to guide efforts to improve treatment of KSHV-mediated diseases. We find that like two other herpesviruses, EBV and HSV-1, KSHV exploits the cellular transcription factor STAT3 to regulate susceptibility of latently-infected cells to lytic triggers. These findings highlight a common STAT3-centered strategy used by herpesviruses to maintain persistence in their host, while also revealing a key molecule to pursue while devising methods to improve herpesvirus lytic phase-directed therapies.Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Anti-TNFα therapy for inflammatory bowel diseases is associated with Epstein-Barr virus lytic activation. - Journal of medical virology
Anti-TNFα therapy, known to suppress T-cell immunity, is increasingly gaining popularity for treatment of autoimmune diseases including inflammatory bowel diseases (IBD). T-cell suppression increases the risk of B-cell EBV-lymphoproliferative diseases and lymphomas. Since EBV-lytic activation is essential for development of EBV-lymphomas and there have been reports of EBV-lymphomas in patients treated with anti-TNFα therapy, we investigated if patients treated with anti-TNFα antibodies demonstrate greater EBV-lytic activity in blood. Peripheral blood mononuclear cells from 10 IBD patients solely on anti-TNFα therapy compared to 3 control groups (10 IBD patients not on immunosuppressive therapy, 10 patients with abdominal pain but without IBD, and 10 healthy subjects) were examined for the percentage of T-cells, EBV load and EBV-lytic transcripts. Patients on anti-TNFα therapy had significantly fewer T-cells, greater EBV load, and increased levels of transcripts from EBV-lytic genes of all kinetic classes compared to controls. Furthermore, exposure of EBV-infected B-cell lines to anti-TNFα antibodies resulted in increased levels of BZLF1 mRNA; BZLF1 encodes for ZEBRA, the viral latency-to-lytic cycle switch. Thus, IBD patients treated with anti-TNFα antibodies have greater EBV loads likely due to enhanced EBV-lytic gene expression and anti-TNFα antibodies may be sufficient to activate the EBV lytic cycle. Findings from this pilot study lay the groundwork for additional scientific and clinical investigation into the effects of anti-TNFα therapy on the life cycle of EBV, a ubiquitous oncovirus that causes lymphomas in the setting of immunocompromise. J. Med. Virol. 9999: 1-7, 2015. © 2015 Wiley Periodicals, Inc.© 2015 Wiley Periodicals, Inc.
Cellular STAT3 functions via PCBP2 to restrain Epstein-Barr Virus lytic activation in B lymphocytes. - Journal of virology
A major hurdle to killing Epstein-Barr virus (EBV)-infected tumor cells using oncolytic therapy is the presence of a substantial fraction of EBV-infected cells that does not support the lytic phase of EBV despite exposure to lytic cycle-promoting agents. To determine the mechanism(s) underlying this refractory state, we developed a strategy to separate lytic from refractory EBV-positive (EBV(+)) cells. By examining the cellular transcriptome in separated cells, we previously discovered that high levels of host STAT3 (signal transducer and activator of transcription 3) curtail the susceptibility of latently infected cells to lytic cycle activation signals. The goals of the present study were 2-fold: (i) to determine the mechanism of STAT3-mediated resistance to lytic activation and (ii) to exploit our findings to enhance susceptibility to lytic activation. We therefore analyzed our microarray data set, cellular proteomes of separated lytic and refractory cells, and a publically available STAT3 chromatin immunoprecipitation sequencing (ChIP-Seq) data set to identify cellular PCBP2 [poly(C)-binding protein 2], an RNA-binding protein, as a transcriptional target of STAT3 in refractory cells. Using Burkitt lymphoma cells and EBV(+) cell lines from patients with hypomorphic STAT3 mutations, we demonstrate that single cells expressing high levels of PCBP2 are refractory to spontaneous and induced EBV lytic activation, STAT3 functions via cellular PCBP2 to regulate lytic susceptibility, and suppression of PCBP2 levels is sufficient to increase the number of EBV lytic cells. We expect that these findings and the genome-wide resources that they provide will accelerate our understanding of a longstanding mystery in EBV biology and guide efforts to improve oncolytic therapy for EBV-associated cancers.Most humans are infected with Epstein-Barr virus (EBV), a cancer-causing virus. While EBV generally persists silently in B lymphocytes, periodic lytic (re)activation of latent virus is central to its life cycle and to most EBV-related diseases. However, a substantial fraction of EBV-infected B cells and tumor cells in a population is refractory to lytic activation. This resistance to lytic activation directly and profoundly impacts viral persistence and the effectiveness of oncolytic therapy for EBV(+) cancers. To identify the mechanisms that underlie susceptibility to EBV lytic activation, we used host gene and protein expression profiling of separated lytic and refractory cells. We find that STAT3, a transcription factor overactive in many cancers, regulates PCBP2, a protein important in RNA biogenesis, to regulate susceptibility to lytic cycle activation signals. These findings advance our understanding of EBV persistence and provide important leads on devising methods to improve viral oncolytic therapies.Copyright © 2015, American Society for Microbiology. All Rights Reserved.
STAT3 interrupts ATR-Chk1 signaling to allow oncovirus-mediated cell proliferation. - Proceedings of the National Academy of Sciences of the United States of America
DNA damage response (DDR) is a signaling network that senses DNA damage and activates response pathways to coordinate cell-cycle progression and DNA repair. Thus, DDR is critical for maintenance of genome stability, and presents a powerful defense against tumorigenesis. Therefore, to drive cell-proliferation and transformation, viral and cellular oncogenes need to circumvent DDR-induced cell-cycle checkpoints. Unlike in hereditary cancers, mechanisms that attenuate DDR and disrupt cell-cycle checkpoints in sporadic cancers are not well understood. Using Epstein-Barr virus (EBV) as a source of oncogenes, we have previously shown that EBV-driven cell proliferation requires the cellular transcription factor STAT3. EBV infection is rapidly followed by activation and increased expression of STAT3, which mediates relaxation of the intra-S phase cell-cycle checkpoint; this facilitates viral oncogene-driven cell proliferation. We now show that replication stress-associated DNA damage, which results from EBV infection, is detected by DDR. However, signaling downstream of ATR is impaired by STAT3, leading to relaxation of the intra-S phase checkpoint. We find that STAT3 interrupts ATR-to-Chk1 signaling by promoting loss of Claspin, a protein that assists ATR to phosphorylate Chk1. This loss of Claspin which ultimately facilitates cell proliferation is mediated by caspase 7, a protein that typically promotes cell death. Our findings demonstrate how STAT3, which is constitutively active in many human cancers, suppresses DDR, fundamental to tumorigenesis. This newly recognized role for STAT3 in attenuation of DDR, discovered in the context of EBV infection, is of broad interest as the biology of cell proliferation is central to both health and disease.
Human B cell immortalization for monoclonal antibody production. - Methods in molecular biology (Clifton, N.J.)
Infection of primary B lymphocytes with Epstein-Barr virus gives rise to growth-transformed and immortalized lymphoblastoid cell lines (LCL) in vitro. Among their many applications is the use of LCL to present antigens in a variety of immunologic assays and to generate human monoclonal antibodies. This chapter describes a method to generate LCL from donor peripheral blood with rapid immortalization and cryopreservation times.
B lymphocytes from patients with a hypomorphic mutation in STAT3 resist Epstein-Barr virus-driven cell proliferation. - Journal of virology
Epstein-Barr virus (EBV) oncogenes exert potent B cell proliferative effects. EBV infection gives rise to B cell lines that readily proliferate in culture. This ability of EBV represents a powerful tool to study cell proliferation. In efforts to delineate the contribution of signal transducer and activator of transcription 3 (STAT3) toward EBV-driven cell proliferation, we have discovered that B cells from patients with autosomal dominant hyper-IgE syndrome (AD-HIES) resist such EBV oncogene-driven outgrowth of cells. Patients with AD-HIES have a dominant negative mutation in their STAT3 gene which renders most of the protein nonfunctional. Exposure of healthy subject-derived B cells to EBV resulted in early activation of STAT3, rapidly followed by increased expression of its mRNA and protein. STAT3 upregulation preceded the expression of EBNA2, temporally one of the first viral oncogenes to be expressed. We found that STAT3 was necessary for subsequent survival and for proliferation of EBV-infected cells past the S phase of the cell cycle. Consequently, B cells from AD-HIES patients were prone to dying and accumulated in the S phase, thereby accounting for impaired cell outgrowth. Of importance, we have now identified a cohort of patients with a primary immunodeficiency disorder whose B cells oppose EBV-driven proliferative signals. These findings simultaneously reveal how EBV manipulates host STAT3 even before expression of viral oncogenes to facilitate cell survival and proliferation, processes fundamental to EBV lymphomagenesis.
Serum IgA to Epstein-Barr virus early antigen-diffuse identifies Hodgkin's lymphoma. - Journal of medical virology
Hodgkin's lymphoma is associated with immune dysregulation. Immune impairment often results in aberrant immune responses and lytic reactivation of ubiquitous Herpesviruses, such as Epstein-Barr virus (EBV) in mucosal tissues. Accordingly, the specificity of IgA to EBV early lytic antigens, which are important for reactivation, was evaluated to determine Hodgkin's lymphoma-specific sero-reactive patterns. Sera from 42 patients with Hodgkin's lymphoma were compared to sera from 17 patients with infectious mononucleosis (IM), another EBV-related condition that often presents in a similar manner; and to sera from 15 healthy EBV-seropositive subjects. Flow cytometry analysis demonstrated that like IM sera, most Hodgkin's lymphoma sera contained IgA that labeled cells expressing EBV early lytic antigens whereas healthy EBV-seropositive sera did not. Further evaluation to distinguish Hodgkin's lymphoma from IM showed that IgA in most Hodgkin's lymphoma, irrespective of the presence of EBV in primary tumors, detected only modified forms of EBV lytic Early Antigen-Diffuse (EA-D) while IM sera detected the un-modified form as well, further supporting the presence of immune dysregulation in Hodgkin's lymphoma patients. This IgA pattern distinguished Hodgkin's lymphoma from IM sera with a sensitivity of 92.9%, specificity 100%, positive predictive value 100%, and negative predictive value 85%. Our findings lay the groundwork for additional scientific and clinical investigation, particularly into the potential for developing Hodgkin's lymphoma-associated diagnostic and prognostic biomarkers.© 2013 Wiley Periodicals, Inc.
Signal transducer and activator of transcription 3 limits Epstein-Barr virus lytic activation in B lymphocytes. - Journal of virology
Lytic activation of Epstein-Barr virus (EBV) is central to its life cycle and to most EBV-related diseases. However, not every EBV-infected B cell is susceptible to lytic activation. This lack of uniform susceptibility to lytic activation also directly impacts the success of viral oncolytic therapy for EBV cancers, yet determinants of susceptibility to lytic induction signals are not well understood. To determine if host factors influence susceptibility to EBV lytic activation, we developed a technique to separate lytic from refractory cells and reported that EBV lytic activation occurs preferentially in cells with lower levels of signal transducer and activator of transcription 3 (STAT3). Using this tool to detect single cells, we now extend the correlation between STAT3 and lytic versus refractory states to EBV-infected circulating B cells in patients with primary EBV infection, leading us to investigate whether STAT3 controls susceptibility to EBV lytic activation. In loss-of-function and gain-of-function studies in EBV-positive B lymphoma and lymphoblastoid cells, we found that the levels of functional STAT3 regulate susceptibility to EBV lytic activation. This prompted us to identify a pool of candidate cellular genes that might be regulated by STAT3 to limit EBV lytic activation. From this pool, we confirmed increases in transcript levels in refractory cells of a set of genes known to participate in transcription repression. Taken together, our findings place STAT3 at a critical crossroads between EBV latency and lytic activation, processes fundamental to EBV lymphomagenesis.
Establishment of Epstein-Barr virus growth-transformed lymphoblastoid cell lines. - Journal of visualized experiments : JoVE
Infection of B cells with Epstein-Barr virus (EBV) leads to proliferation and subsequent immortalization, resulting in establishment of lymphoblastoid cell lines (LCL) in vitro. Since LCL are latently infected with EBV, they provide a model system to investigate EBV latency and virus-driven B cell proliferation and tumorigenesis(1). LCL have been used to present antigens in a variety of immunologic assays(2, 3). In addition, LCL can be used to generate human monoclonal antibodies(4, 5) and provide a potentially unlimited source when access to primary biologic materials is limited(6, 7). A variety of methods have been described to generate LCL. Earlier methods have included the use of mitogens such as phytohemagglutinin, lipopolysaccharide(8), and pokeweed mitogen(9) to increase the efficiency of EBV-mediated immortalization. More recently, others have used immunosuppressive agents such as cyclosporin A to inhibit T cell-mediated killing of infected B cells(7, 10-12). The considerable length of time from EBV infection to establishment of cell lines drives the requirement for quicker and more reliable methods for EBV-driven B cell growth transformation. Using a combination of high titer EBV and an immunosuppressive agent, we are able to consistently infect, transform, and generate LCL from B cells in peripheral blood. This method uses a small amount of peripheral blood mononuclear cells that are infected in vitroclusters of cells can be demonstrated. The presence of CD23 with EBV in the presence of FK506, a T cell immunosuppressant. Traditionally, outgrowth of proliferating B cells is monitored by visualization of microscopic clusters of cells about a week after infection with EBV. Clumps of LCL can be seen by the naked eye after several weeks. We describe an assay to determine early if EBV-mediated growth transformation is successful even before microscopic clusters of cells can be demonstrated. The presence of CD23(hi)CD58(+) cells observed as early as three days post-infection indicates a successful outcome.
Identification of a sub-population of B cells that proliferates after infection with Epstein-Barr virus. - Virology journal
Epstein-Barr virus (EBV)-driven B cell proliferation is critical to its subsequent persistence in the host and is a key event in the development of EBV-associated B cell diseases. Thus, inquiry into early cellular events that precede EBV-driven proliferation of B cells is essential for understanding the processes that can lead to EBV-associated B cell diseases.Infection with high titers of EBV of mixed, primary B cells in different stages of differentiation occurs during primary EBV infection and in the setting of T cell-immunocompromise that predisposes to development of EBV-lymphoproliferative diseases. Using an ex vivo system that recapitulates these conditions of infection, we correlated expression of selected B cell-surface markers and intracellular cytokines with expression of EBV latency genes and cell proliferation.We identified CD23, CD58, and IL6, as molecules expressed at early times after EBV-infection. EBV differentially infected B cells into two distinct sub-populations of latently infected CD23+ cells: one fraction, marked as CD23hiCD58+IL6- by day 3, subsequently proliferated; another fraction, marked as CD23loCD58+, expressed IL6, a B cell growth factor, but failed to proliferate. High levels of LMP1, a critical viral oncoprotein, were expressed in individual CD23hiCD58+ and CD23loCD58+ cells, demonstrating that reduced levels of LMP1 did not explain the lack of proliferation of CD23loCD58+ cells. Differentiation stage of B cells did not appear to govern this dichotomy in outcome either. Memory or naïve B cells did not exclusively give rise to either CD23hi or IL6-expressing cells; rather memory B cells gave rise to both sub-populations of cells.B cells are differentially susceptible to EBV-mediated proliferation despite expression of viral gene products known to be critical for continuous B cell growth. Cellular events, in addition to viral gene expression, likely play a critical role in determining the outcome of EBV infection. By indentifying cells predicted to undergo EBV-mediated proliferation, our study provides new avenues of investigation into EBV pathogenesis.

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