Human Herpesvirus-8: Clinical Features of an Emerging Viral Pathogen

The Pediatric Infectious Disease Journal. Jan, 2005  |  Pubmed ID: 15665715

Cells Lytically Infected with Epstein-Barr Virus Are Detected and Separable by Immunoglobulins from EBV-seropositive Individuals

Journal of Virological Methods. Oct, 2006  |  Pubmed ID: 16843536

The role of Epstein-Barr virus (EBV) lytic cycle gene expression in lymphocytes in the pathogenesis of EBV-associated diseases is incompletely understood. The ability to physically separate lytically induced from latently infected cells from the same population and to examine them in parallel would significantly enhance understanding of the viral, cellular, and environmental factors that govern susceptibility of an EBV-infected cell to lytic cycle induction stimuli at the single cell level. This study demonstrates, using a flow cytometry-based system, that human serum immunoglobulins from individuals immune to EBV reproducibly discriminate between and can be used to physically separate lytically induced from latently infected B cells. Using this new quantitative and sensitive technique, two novel observations about lytic cycle activation were made. First, the kinetics of lytic cycle activation by histone deacetylase inhibitors is more rapid than induction by a DNA methyl transferase inhibitor. Second, butyrate-treated cells which are initially refractory to lytic cycle activation can be induced upon subsequent exposure to the inducing agent. Therefore, susceptibility to lytic cycle induction of a latently infected B cell is governed by environmental and physiologic factors and not by permanent cellular or viral genetic changes.

Purulent Pericarditis Caused by Group a Streptococcus

Texas Heart Institute Journal / from the Texas Heart Institute of St. Luke's Episcopal Hospital, Texas Children's Hospital. 2006  |  Pubmed ID: 17215986

Purulent pericarditis is a rare disease that is most often caused by organisms such as Staphylococcus aureus, Streptococcus pneumoniae, viridans streptococci, Haemophilus influenzae, and anaerobic bacteria. We present an unusual case of purulent pericarditis caused by Streptococcus pyogenes, Lancefield group A streptococcus (GAS), and we provide a review of the literature.

Serum IgA Antibodies to Epstein-Barr Virus (EBV) Early Lytic Antigens Are Present in Primary EBV Infection

The Journal of Infectious Diseases. Feb, 2007  |  Pubmed ID: 17230407

Primary Epstein-Barr virus (EBV) infection is characterized by the presence of IgM antibodies to viral capsid antigen and the absence of antibodies to EB nuclear antigen. Here, using a flow cytometry-based assay, we investigated whether IgA antibodies are a marker for primary infection. Serum IgA antibodies in 15 individuals with primary EBV infection reacted with 15%-55.6% of HH514-16 Burkitt lymphoma cells expressing early lytic antigens (EAs), whereas IgA antibodies in serum samples from 15 healthy EBV-seropositive individuals reacted with 0.02%-2% of cells with EAs (P<.0001). IgA antibodies in primary infection were directed against the Bam Z Epstein-Barr replication activator (ZEBRA) (BZLF1) and diffuse EA (BMRF1) EAs. Thus, IgA antibodies to EBV EAs are produced during primary EBV infection and are likely to be stimulated as a result of lytic EBV replication in mucosal sites. Detection of IgA antibodies to EA may be developed into a diagnostic tool for primary EBV infection.

Repertoire and Frequency of Immune Cells Reactive to Epstein-Barr Virus-derived Autologous Lymphoblastoid Cell Lines

Blood. Feb, 2008  |  Pubmed ID: 17942757

Answers to questions about frequency and repertoire of immune cells, relative contributions made by different types of immune cells toward the total Epstein-Barr virus (EBV)-directed response and the variation of such responses in healthy persons have been elusive because of disparities in assays, antigen presenting cells, and antigenic sources used in previous experiments. In this study, we addressed these questions using an assay that allowed direct comparison of responses generated by different types of cells of the immune system. This short-term (20-hour) ex vivo assay measured interferon-gamma production by blood cells in response to autologous EBV-transformed lymphoblastoid cell lines (LCLs). Our experiments defined the variation in responses among persons and clearly distinguished 10 healthy EBV-immune from 10 healthy EBV-naive persons. In EBV-immune persons, 33% of responding cells were CD4(+), 43.3% were CD8(+), and 12.9% were gamma-delta T cells. LCL-reactive CD8(+) T cells were only 1.7-fold more frequent than similarly reactive CD4(+)T cells. Responses by gamma-delta T cells were 6-fold higher in seropositive than in seronegative persons. Our findings emphasize the importance of CD4(+) and gamma-delta T-cell responses and have implications for immunotherapy and for identifying defects in T-cell populations that might predispose to development of EBV-associated lymphomas.

Epstein-Barr Virus-mediated Dysregulation of Human MicroRNA Expression

Cell Cycle (Georgetown, Tex.). Nov, 2008  |  Pubmed ID: 19001862

MicroRNAs (miRNAs) are a large class of small (approximately 22 nt) noncoding RNAs that negatively regulate gene expression most often at the level of translation, and have been shown to be key regulators in a variety of processes including development, cell cycle and immunity. The Epstein-Barr virus (EBV) is an oncogenic herpes virus endemic in humans that encodes at least twenty-two of its own miRNAs. Cellular miRNAs have well-established roles in cancer and immune pathways, and multiple cellular miRNAs directly target viral messages. Additionally, multiple viruses express suppressors of cellular RNAi-induced silencing. Here we show that EBV de novo infection of primary cultured human B-cells results in a dramatic downregulation of cellular miRNA expression, suggesting the virus may encode or activate a suppressor of miRNA expression. We additionally show that the immuno-modulatory microRNA miR-146a, downregulated on initial infection, is significantly upregulated more than 100-fold upon induction of the viral lytic cycle, and appears to have inhibitory effects on the progression of the lytic cycle. Our results show that EBV has substantial effects on cellular miRNA expression.

Stimulus Duration and Response Time Independently Influence the Kinetics of Lytic Cycle Reactivation of Epstein-Barr Virus

Journal of Virology. Oct, 2009  |  Pubmed ID: 19656890

Epstein-Barr virus (EBV) can be reactivated from latency into the lytic cycle by many stimuli believed to operate by different mechanisms. Cell lines containing EBV differ in their responses to inducing stimuli, yet all stimuli require de novo protein synthesis (44). A crucial step preliminary to identifying these proteins and determining when they are required is to measure the duration of stimulus and response time needed for activation of expression of EBV BRLF1 and BZLF1, the earliest viral indicators of reactivation. Here we show, with four EBV-containing cell lines that respond to different inducing agents, that stimuli that are effective at reactivating EBV can be divided into two main groups. The histone deacetylase inhibitors sodium butyrate and trichostatin A require a relatively long period of exposure, from 2 to 4 h or longer. Phorbol esters, anti-immunoglobulin G (anti-IgG), and, surprisingly, 5-aza-2'-deoxycytidine require short exposures of 15 min or less. The cell/virus background influences the response time. Expression of the EBV BZLF1 and BRLF1 genes can be detected before 2 h in Akata cells treated with anti-IgG, but both long- and short-duration stimuli required 4 or more hr to activate BZLF1 and BRLF1 expression in HH514-16, Raji, or B95-8 cells. Thus, stimulus duration and response time are independent variables. Neither stimulus duration nor response time can be predicted by the number of cells activated into the lytic cycle. These experiments shed new light on the earliest events leading to lytic cycle reactivation of EBV.

Upregulation of STAT3 Marks Burkitt Lymphoma Cells Refractory to Epstein-Barr Virus Lytic Cycle Induction by HDAC Inhibitors

Journal of Virology. Jan, 2010  |  Pubmed ID: 19889776

A fundamental problem in studying the latent-to-lytic switch of Epstein-Barr virus (EBV) and the viral lytic cycle itself is the lack of a culture system fully permissive to lytic cycle induction. Strategies to target EBV-positive tumors by inducing the viral lytic cycle with chemical agents are hindered by inefficient responses to stimuli. In vitro, even in the most susceptible cell lines, more than 50% of cells latently infected with EBV are refractory to induction of the lytic cycle. The mechanisms underlying the refractory state are not understood. We separated lytic from refractory Burkitt lymphoma-derived HH514-16 cells after treatment with an HDAC inhibitor, sodium butyrate. Both refractory- and lytic-cell populations responded to the inducing stimulus by hyperacetylation of histone H3. However, analysis of host cell gene expression showed that specific cellular transcripts Stat3, Fos, and interleukin-8 (IL-8) were preferentially upregulated in the refractory-cell population, while IL-6 was upregulated in the lytic population. STAT3 protein levels were also substantially increased in refractory cells relative to untreated or lytic cells. This increase in de novo expression resulted primarily in unphosphorylated STAT3. Examination of single cells revealed that high levels of STAT3 were strongly associated with the refractory state. The refractory state is manifest in a unique subpopulation of cells that exhibits different cellular responses than do lytic cells exposed to the same stimulus. Identifying characteristics of cells refractory to lytic induction relative to cells that undergo lytic activation will be an important step in developing a better understanding of the regulation of the EBV latent to lytic switch.

Identification of a Sub-population of B Cells That Proliferates After Infection with Epstein-Barr Virus

Virology Journal. 2011  |  Pubmed ID: 21352549

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.