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Journal of Investigative Dermatology 03/2012; 132(6):1733-5. · 6.31 Impact Factor
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ABSTRACT: In the field of herpesvirus research, the exact molecular mechanism by which such viruses reactivate from latency remains elusive. Kaposi's sarcoma-associated herpesvirus (KSHV) primarily exists in a latent state, while only 1-3% of cells support lytic infection at any specific time. KSHV reactivation from latency is an exceedingly intricate process mediated by the integration of viral and cellular factors. Previously, our lab has described early growth response-1 (Egr-1) as an essential component for the KSHV reactivation process via its ability to mediate transcription of KSHV ORF50, the gene encoding for replication and transcription activator (RTA), a viral component known to control the switch from latent to lytic infection. In here, electrophoretic mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP) experiments revealed that Egr-1 binds KSHV ORF50 promoter (ORF50P) in at least two different GC-rich binding domains. Expression profiles of cellular egr-1 and KSHV-encoded ORF50 follow a similar pattern during de novo KSHV infection. Over-expressing Egr-1, a signaling component downstream of Raf>MEK>ERK1/2, in KSHV-infected cells activates KSHV lytic replication. Through performing more physiologically relevant experiments, we analyzed the effect of a dietary supplement containing resveratrol on KSHV-infected cells. Our results, for the first time, demonstrate resveratrol to act in lowering ERK1/2 activity and expression of Egr-1 in KSHV-infected cells, resulting in the suppression of virus reactivation from latency. Taken together, these findings will undoubtedly contribute to future studies on not only combating KSHV related disease conditions, but also on other herpesviruses-induced pathogenesis.
PLoS ONE 01/2012; 7(3):e33364. · 4.09 Impact Factor
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ABSTRACT: Viruses are obligate intracellular parasites, relying to a major extent on the host cell for replication. An active replication of the viral genome results in a lytic infection characterized by the release of new progeny virus particles, often upon the lysis of the host cell. Another mode of virus infection is the latent phase, where the virus is 'quiescent' (a state in which the virus is not replicating). A combination of these stages, where virus replication involves stages of both silent and productive infection without rapidly killing or even producing excessive damage to the host cells, falls under the umbrella of a persistent infection. Reactivation is the process by which a latent virus switches to a lytic phase of replication. Reactivation may be provoked by a combination of external and/or internal cellular stimuli. Understanding this mechanism is essential in developing future therapeutic agents against viral infection and subsequent disease. This article examines the published literature and current knowledge regarding the viral and cellular proteins that may play a role in viral reactivation. The focus of the article is on those viruses known to cause latent infections, which include herpes simplex virus, varicella zoster virus, Epstein-Barr virus, human cytomegalovirus, human herpesvirus 6, human herpesvirus 7, Kaposi's sarcoma-associated herpesvirus, JC virus, BK virus, parvovirus and adenovirus.
Future Virology 04/2011; 6(4):451-463. · 1.21 Impact Factor
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ABSTRACT: One of the important questions in the field of virus research is about the balance between latent and lytic cycles of replication. Kaposi's sarcoma-associated herpesvirus (KSHV) remains predominantly in a latent state, with only 1-3% of cells supporting a lytic replication at any time. KSHV glycoprotein B (gB) is expressed not only on the virus envelope but also on the surfaces of the few cells supporting lytic replication. Using co-culture experiments, we determined that expression of KSHV gB on as few as 1-2% of human dermal microvascular endothelial cells resulted in a 10-fold inhibition of expression of ORF50, a viral gene critical for the onset of lytic replication. Also, we demonstrate that such a profound inhibitory effect of gB on the lytic cycle of virus replication is by repressing the ability of Egr-1 (early growth response-1) to bind and activate the ORF50 promoter. In general, virus-encoded late stage structural proteins, such as gB, are said to play major roles in virus entry and egress. The present report provides initial evidence supporting a role for membrane-associated gB expressed in a minimal number of cells to promote virus latency. These findings may have ramifications leading to a better understanding of the role of virus-encoded structural proteins not only in KSHV-related diseases but also in other viruses causing latent infections.
Journal of Biological Chemistry 11/2010; 285(48):37491-502. · 4.77 Impact Factor
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ABSTRACT: One of the important questions in the field of virus research is about the balance between latent and lytic cycles of replication.
Kaposi sarcoma associated herpesvirus (KSHV) remains predominately in a latent state with only 1-3% of cells supporting a
lytic replication at any time. KSHV glycoprotein B (gB) is not only expressed on the virus envelope but also on the surfaces
of the few cells supporting lytic replication. Using co-culture experiments, we determined that expression of KSHV gB on
as few as 1-2% of human dermal microvascular endothelial (HMVEC-d) cells resulted in a 10 fold inhibition of ORF50 expression;
a viral gene critical for the onset of lytic replication. Also, we demonstrate that such a profound inhibitory effect of
gB on the lytic cycle of virus replication is by repressing the ability of early growth response-1 (Egr-1) to bind and activate
the ORF50 promoter. In general, virus encoded late stage structural proteins such as gB are said to play major roles in virus
entry and egress. The present report provides initial evidence supporting a role for membrane associated gB expressed in
a minimal number of cells to promote virus latency. These findings may have ramifications leading to a better understanding
of the role of virus encoded structural proteins in not only KSHV related diseases but also in other viruses causing latent
infections.
Journal of Biological Chemistry 09/2010; · 4.77 Impact Factor
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ABSTRACT: Kaposi's sarcoma-associated herpesvirus (KSHV) has both latent and lytic phases of replication. The molecular switch that triggers a reactivation is still unclear. Cells from the S phase of the cell cycle provide apt conditions for an active reactivation. In order to specifically delineate the Raman spectra of cells supporting KSHV reactivation, we followed a novel approach where cells were sorted based on the state of infection (latent versus lytic) by a flow cytometer and then analysed by the Raman tweezers. The Raman bands at 785, 813, 830, 1095 and 1128 cm(-1) are specifically altered in cells supporting KSHV reactivation. These five peaks make up the Raman fingerprint of cells supporting KSHV reactivation. The physiological relevance of the changes in these peaks with respect to KSHV reactivation is discussed in the following report.
Journal of Cellular and Molecular Medicine 09/2008; 13(8B):1920-32. · 4.13 Impact Factor
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ABSTRACT: Kaposi's sarcoma-associated herpesvirus (KSHV) has two modes of replications: latent and lytic replications. Reactivation from latency is dictated, in part, by the cell cycle. Herein, we have attempted to delineate the importance of cell cycle in KSHV pathogenesis by exploring the expression pattern of cell-surface receptors during different phases of the cell cycle. alphaV integrin expression is augmented during S phase in fibroblasts, epithelial and KSHV-infected cells. Using a Matrigel system, we pioneer the concept that KSHV-infected primary effusion lymphoma cells can attach to extracellular matrix proteins. This attachment is mediated primarily via alphaV integrins or virally encoded gB, and occurs preferentially in cells from S phase or cells from S phase actively supporting a lytic infection respectively. Such an ability of infected B cells to attach to endothelial cells may also aid in the dissemination of infection. The keystone of this work is that for the first time, we describe the ability of KSHV-infected B cells to preferentially use cellular (alphaV) or viral (gB) receptors to specifically bind cells, depending upon the stage of the cell cycle and infection.
Cellular Microbiology 08/2008; 10(7):1546-58. · 5.46 Impact Factor
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ABSTRACT: Nanotechnology is at the forefront of a revolution in the biomedical sciences. It has the p?tential to give both researchers
and doctors' abilities they would never have previously dreamt of, including everything from the capability to deliver engineered
drugs to specific target tissues to filtering even the smallest harmful particles out of our water supply. With such increased
power, however, also comes increased responsibility. Nanotechnologies have as much p?tential to do harm as they do good. For
instance, nanotechnology could be an enormously effective tool in the hands of a bioterrorist. As such, it is critically important
for mankind to fully appreciate the technology's awesome p?tential and the possible harm it may cause before this p?tential
is realized. To this end, this review discusses not only the current and future applications of nanotechnology in the biomedical
sciences, but also the incredibly important ethical ramifications of such applications.
KeywordsNanotechnology-ethics-nanite-nanate-medicine-review
12/2007: pages 117-130;
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ABSTRACT: Cells require the ability to appropriately respond to signals in their extracellular environment. To initiate, inhibit and control these processes, the cell has developed a complex network of signaling cascades. The phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways regulate several responses including mitosis, apoptosis, motility, proliferation, differentiation and many others. It is not surprising, therefore, that many viruses target the PI3K and MAPK pathways as a means to manipulate cellular function. Recently, Kaposi's sarcoma-associated herpes virus (KSHV) has been added to the list. KSHV manipulates the PI3K and MAPK pathways to control such divergent processes as cell survival, cellular migration, immune responses, and to control its own reactivation and lytic replication. Manipulation of the PI3K and MAPK pathways also plays a role in malignant transformation. Here, the authors review the potential to target the PI3K and MAPK signaling pathways to inhibit KSHV infection and pathogenesis.
Expert opinion on therapeutic targets 06/2007; 11(5):589-99. · 3.72 Impact Factor
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ABSTRACT: Angiogenesis is defined as the formation of new blood vessels. In a recently concluded study, we identified Kaposi's sarcoma-associated herpesvirus (KSHV)-infected cells derived from primary effusion lymphoma (PEL) to overexpress vascular endothelial growth factor (VEGF) that had the propensity to mediate tubule formation on a Matrigel, an indicator of angiogenesis. The objective of this study was to determine the receptor molecules that mediate the tubule formation induced by the supernatant derived from KSHV-infected PEL cells.
The identity of receptor(s) that play a role in mediating tubule formation driven by PEL supernatant was determined by the classical in vitro angiogenesis assay conducted on a Matrigel.
RGD peptides, antibodies, and siRNA specific to beta1 integrins significantly lowered the ability of the PEL supernatants to induce tubule formation by endothelial cells. beta1 Integrins mediated tubule formation to comparable levels in endothelial cells that were incubated with supernatants derived from uninduced or TPA-induced PEL cells. Interestingly, the beta1 integrins did not seem to have a major role in cellular attachment.
We report for the first time a critical role for beta1 integrins in angiogenesis supported by the supernatant from KSHV-infected PEL cells.
Intervirology 02/2007; 50(4):245-53. · 2.34 Impact Factor
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ABSTRACT: Following an infection, Kaposi's sarcoma-associated herpes virus (KSHV) exists predominantly in its latent state, with only 1-2% of infected cells undergoing lytic reactivation. We have previously demonstrated along with others a relationship between lytic reactivation and cell cycle progression (Bryan et al., 2006. J. Gen. Virol. 87: 519; McAllister et al., 2005. J. Virol. 79: 2626). Infected cells in the S phase are much more likely to undergo lytic reactivation when compared to those in G(0)/G(1) phase. Through the use of scanning electron microscopy (SEM), we analyzed changes occurring on the surface of cells undergoing KSHV reactivation. KSHV reactivation was observed predominantly in cells with smoother surface topology; a hallmark of cells derived from S phase. Interestingly, during the late stages of the reactivation process, we observed KSHV particles to egress cells through budding. Taken together, based on scanning electron microscopy and transmission electron microscopy evidences, we demonstrate for the first time the existence of a direct link between cell surface topology, cell cycle progression and KSHV reactivation.
Journal of Electron Microscopy 01/2007; 56(1):27-36. · 1.31 Impact Factor
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ABSTRACT: Kaposi's sarcoma-associated herpesvirus (KSHV) causes Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman's disease. KSHV infection of cells produces both latent and lytic cycles of infection. In vivo, the virus is found predominantly in the latent state. In vitro, a lytic infection can be induced in KSHV-infected cells by treating with phorbol ester (TPA). However, the exact signalling events that lead to the reactivation of KSHV lytic infection are still elusive. Here, a role is demonstrated for B-Raf/MEK/ERK signalling in TPA-induced reactivation of KSHV latent infection. Inhibiting MEK/ERK signalling by using MEK-specific inhibitors decreased expression of the TPA-induced KSHV lytic-cycle gene ORF8. Transfection of BCBL-1 cells with B-Raf small interfering RNA inhibited TPA-induced KSHV lytic infection significantly. Additionally, overexpression of MEK1 induced a lytic cycle of KSHV infection in BCBL-1 cells. The significance of these findings in understanding the biology of KSHV-associated pathogenesis is discussed.
Journal of General Virology 06/2006; 87(Pt 5):1139-44. · 3.36 Impact Factor
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ABSTRACT: Kaposi's sarcoma-associated herpesvirus (KSHV) is the latest addition to the long list of human herpesviruses. Reactivation of latent herpesvirus infections is still a mystery. It was demonstrated recently that the phorbol ester TPA was efficient in inducing a reactivation of KSHV infection in the S phase of the cell cycle. In the present study, flow cytometry-sorted, TPA-induced, KSHV-infected haematopoietic cells (BCBL-1) were used to analyse the expression profiles of cancer-related cellular genes in the S phase of the cell cycle compared with the G0/1 phase by using microarrays. Overall, the S phase of the cell cycle seems to provide KSHV with an apt environment for a productive lytic cycle of infection. The apt conditions include cellular signalling that promotes survivability, DNA replication and lipid metabolism, while blocking cell-cycle progression to M phase. Some of the important genes that were overexpressed during the S phase of the cell cycle compared with the G0/1 phase of TPA-induced BCBL-1 cells are v-myb myeloblastosis (MYBL2), protein kinase-membrane associated tyrosine/threonine 1 (PKMYT1), ribonucleotide reductase M1 polypeptide (RRM1) and peroxisome proliferator-activated receptors delta (PPARD). Inhibition of PKMYT1 expression by the use of specific short interfering RNAs significantly lowered the TPA-induced KSHV lytic cycle of infection. The significance of these and other genes in the reactivation of KSHV is discussed in the following report. Taken together, a flow cytometry-microarray-based method to study the cellular conditions critical for the reactivation of KSHV infection is reported here for the first time.
Journal of General Virology 04/2006; 87(Pt 3):519-29. · 3.36 Impact Factor
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ABSTRACT: In the molecular world, researchers act as detectives working hard to unravel the mysteries surrounding cells. One of the researchers' greatest tools in this endeavor has been Raman spectroscopy. Raman spectroscopy is a spectroscopic technique that measures the unique Raman spectra for every type of biological molecule. As such, Raman spectroscopy has the potential to provide scientists with a library of spectra that can be used to unravel the makeup of an unknown molecule. However, this technique is limited in that it is not able to manipulate particular structures without disturbing their unique environment. Recently, a novel technology that combines Raman spectroscopy with optical tweezers, termed Raman tweezers, evades this problem due to its ability to manipulate a sample without physical contact. As such, Raman tweezers has the potential to become an incredibly effective diagnostic tool for differentially distinguishing tissue, and therefore holds great promise in the field of virology for distinguishing between various virally infected cells. This review provides an introduction for a virologist into the world of spectroscopy and explores many of the potential applications of Raman tweezers in virology.
Virology Journal 02/2006; 3:51. · 2.34 Impact Factor
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ABSTRACT: Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with Kaposi's sarcoma (KS), primary effusion lymphoma(PEL), multicentric Castleman disease, and other tumors. Progression of KS is dictated by an aberrant production of inflammatory cytokines and increase in KSHV infection of cells. In this study, we analyzed the effect of cigarette smoke concentrate (CSC) on KSHV infection of human foreskin fibroblasts (HFF) using real time quantitative RT-PCR. Our results demonstrated that the CSC-treated cells supported 50% lower infection of KSHV when compared to the untreated cells. Radiolabeled-binding assays indicated that CSC inhibited KSHV infection of cells at a post attachment stage of entry. Taken together, we report for the first time the ability of CSC to specifically inhibit KSHV infection of cells.
Virus Research 01/2006; 114(1-2):172-6. · 2.94 Impact Factor
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ABSTRACT: Leukemia is characterized by the production of an excessive number of abnormal white blood cells. Over time, this expanding population of poorly/non- functional white blood cells overwhelms the normal function of the body's blood and immune systems. DNA translocations have been found common to leukemia, including Raf mutations. While the cause of leukemia is not known, several risk factors have been identified. In this review, we present an update on the role of AIDS related viruses as an etiology for leukemia. Human immunodeficiency virus-1 and -2 (HIV-1; -2) are the cause for the development of acquired immune deficiency syndrome (AIDS). Epstein-Barr virus (EBV), human cytomegalovirus (HCMV), Human papillomavirus (HPV), and Kaposi's sarcoma-associated herpesvirus (KSHV) are specifically implicated in AIDS associated malignancies. However, there are other viruses that are associated to a lesser extent with the AIDS condition and they are Human T-cell leukemia virus-1 (HTLV-1), hepatitis B virus (HBV), hepatitis C virus (HCV), and human herpesvirus-6 (HHV-6). Of these viruses, HTLV-1 has been etiologically associated with leukemia. Recent evidence suggests that EBV, HBV, HCV, and KSHV may also play a role in the development of some types of leukemia. Raf signaling has been shown to aid in the infection and pathogenesis of many of these viruses, making Raf pathway components good potential targets for the treatment of leukemia induced by AIDS related viruses.
Current HIV Research 11/2005; 3(4):319-27. · 1.75 Impact Factor
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ABSTRACT: Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus-8 (HHV-8) is a newly identified herpesvirus. KSHV is an important pathogen capable of causing disease that affects all age groups worldwide. KSHV is etiologically associated with all forms of Kaposi's sarcoma (KS), body cavity lymphomas, and multicentric Castleman disease (MCD). The use of highly active antiretroviral therapy (HAART) since 1996 has markedly reduced the prevalence of KS in western countries, but because 99% of the 40 million patients with AIDS in the world cannot afford HAART, KSHV pathogenesis is still a very common problem. In this chapter, we delineate some of the latest findings about KSHV infection and pathogenesis.
Frontiers in Bioscience 02/2005; 10:2882-91. · 3.52 Impact Factor
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ABSTRACT: Recombinant green fluorescent protein encoding Kaposi's sarcoma-associated herpesvirus (rKSHV.152) infection of beta-estradiol stimulated human foreskin fibroblasts (HFF) or HFF/DeltaB-Raf([FF]):ER (expressing a weaker form of B-Raf) could be enhanced to levels comparable to that of HFF/DeltaB-Raf([DD]):ER cells by pretreating cells with soluble vascular endothelial growth factor (VEGF). Conversely, VEGF expression and infection efficiency typically observed in beta-estradiol stimulated HFF/DeltaB-Raf([DD]):ER cells could be lowered significantly by treating with VEGF small interfering RNA. In addition, we observed enhancement of the KSHV infection in HFF cells transfected with human VEGF(121). These results confirm the ability of Raf-induced VEGF to augment KSHV infection of cells.
Journal of Virology 01/2005; 78(23):13381-90. · 5.40 Impact Factor
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ABSTRACT: Kaposiâ s sarcoma-associated herpesvirus (KSHV) has two modes replication: latent and lytic replication. Reactivation from latency is dictated, in part, by the cell cycle. Herein, we have attempted to delineate the importance of cell cycle in KSHV pathogenesis by exploring the expression pattern of cell surface receptors during different phases of the cell cycle. â £V integrin expression is augmented during S phase in fibroblasts, epithelial, and KSHV infected cells. Using a Matrigel system, we pioneer the concept that KSHV infected primary effusion lymphoma (PEL) cells can attach to extracellular matrix proteins. This attachment is mediated primarily via â £V integrins or virally encoded gB, and occurs preferentially in cells from S phase or cells from S phase actively supporting a lytic infection, respectively. Such an ability of infected B cells to attach to endothelial cells may also aid in the dissemination of infection. The keystone of this work is that for the first time, we describe the ability of KSHV infected B cells to preferentially use cellular (â £V) or viral (gB) receptors to specifically bind cells, depending upon the stage of the cell cycle and infection. Originally published Cellular Microbiology, Vol. 10, No. 7, July 2008
