The Dynamics of EBV Shedding Implicate a Central Role for Epithelial Cells in Amplifying Viral Output

To develop more detailed models of EBV persistence we have studied the dynamics of virus shedding in healthy carriers. We demonstrate that EBV shedding into saliva is continuous and rapid such that the virus level is replaced in ≤2 minutes, the average time that a normal individual swallows. Thus, the mouth is not a reservoir of virus but a conduit through which a continuous flow stream of virus passes in saliva. Consequently, virus is being shed at a much higher rate than previously thought, a level too high to be accounted for by replication in B cells in Waldeyer's ring alone. Virus shedding is relatively stable over short periods (hours-days) but varies through 3.5 to 5.5 logs over longer periods, a degree of variation that also cannot be accounted for solely by replication in B cells. This variation means, contrary to what is generally believed, that the definition of high and low shedder is not so much a function of variation between individuals but within individuals over time. The dynamics of shedding describe a process governing virus production that is occurring independently ≤3 times at any moment. This process grows exponentially and is then randomly terminated. We propose that these dynamics are best explained by a model where single B cells sporadically release virus that infects anywhere from 1 to 5 epithelial cells. This infection spreads at a constant exponential rate and is terminated randomly, resulting in infected plaques of epithelial cells ranging in size from 1 to 105 cells. At any one time there are a very small number (≤3) of plaques. We suggest that the final size of these plaques is a function of the rate of infectious spread within the lymphoepithelium which may be governed by the structural complexity of the tissue but is ultimately limited by the immune response

Incidence of multiple Herpesvirus infection in HIV seropositive patients, a big concern for Eastern Indian scenario

<p>Abstract</p> <p>Background</p> <p>Human immunodeficiency virus (HIV) infection is associated with an increased risk for human <it>herpes viruses </it>(HHVs) and their related diseases and they frequently cause disease deterioration and therapeutic failures. Methods for limiting the transmission of HHVs require a better understanding of the incidence and infectivity of oral HHVs in HIV-infected patients. This study was designed to determine the seroprevalence of human herpes viruses (CMV, HSV 2, EBV-1, VZV) antibodies and to evaluate their association with age, sex as well as other demographic and behavioral factors.</p> <p>Results</p> <p>A study of 200 HIV positive patients from Eastern India attending the Calcutta Medical College Hospital, Kolkata, West Bengal, Apex Clinic, Calcutta Medical College Hospital and ART Center, School of Tropical Medicine, Kolkata, West Bengal was done. Serum samples were screened for antibodies to the respective viruses using the indirect ELISA in triplicates.</p> <p><it>CytoMegalo virus </it>(CMV), <it>Herpes Simplex virus </it>type 2 (HSV-2), <it>Varicella Zoster virus </it>(VZV), and <it>Epstein Barr virus </it>(EBV-1) were detected in 49%, 47%, 32.5%, and 26% respectively.</p> <p>Conclusion</p> <p>This study has contributed baseline data and provided insights in viral OI and HIV co-infection in Eastern India. This would undoubtedly serve as a basis for further studies on this topic.</p

Early Events Associated with Infection of Epstein-Barr Virus Infection of Primary B-Cells

Epstein Barr virus (EBV) is closely associated with the development of a vast number of human cancers. To develop a system for monitoring early cellular and viral events associated with EBV infection a self-recombining BAC containing 172-kb of the Epstein Barr virus genome BAC-EBV designated as MD1 BAC (Chen et al., 2005, J.Virology) was used to introduce an expression cassette of green fluorescent protein (GFP) by homologous recombination, and the resultant BAC clone, BAC-GFP-EBV was transfected into the HEK 293T epithelial cell line. The resulting recombinant GFP EBV was induced to produce progeny virus by chemical inducer from the stable HEK 293T BAC GFP EBV cell line and the virus was used to immortalize human primary B-cell as monitored by green fluorescence and outgrowth of the primary B cells. The infection, B-cell activation and cell proliferation due to GFP EBV was monitored by the expression of the B-cell surface antigens CD5, CD10, CD19, CD23, CD39, CD40 , CD44 and the intercellular proliferation marker Ki-67 using Flow cytometry. The results show a dramatic increase in Ki-67 which continues to increase by 6–7 days post-infection. Likewise, CD40 signals showed a gradual increase, whereas CD23 signals were increased by 6–12 hours, maximally by 3 days and then decreased. Monitoring the viral gene expression pattern showed an early burst of lytic gene expression. This up-regulation of lytic gene expression prior to latent genes during early infection strongly suggests that EBV infects primary B-cell with an initial burst of lytic gene expression and the resulting progeny virus is competent for infecting new primary B-cells. This process may be critical for establishment of latency prior to cellular transformation. The newly infected primary B-cells can be further analyzed for investigating B cell activation due to EBV infection

Epstein-Barr virus: clinical and epidemiological revisits and genetic basis of oncogenesis

Epstein-Barr virus (EBV) is classified as a member in the order herpesvirales, family herpesviridae, subfamily gammaherpesvirinae and the genus lymphocytovirus. The virus is an exclusively human pathogen and thus also termed as human herpesvirus 4 (HHV4). It was the first oncogenic virus recognized and has been incriminated in the causation of tumors of both lymphatic and epithelial nature. It was reported in some previous studies that 95% of the population worldwide are serologically positive to the virus. Clinically, EBV primary infection is almost silent, persisting as a life-long asymptomatic latent infection in B cells although it may be responsible for a transient clinical syndrome called infectious mononucleosis. Following reactivation of the virus from latency due to immunocompromised status, EBV was found to be associated with several tumors. EBV linked to oncogenesis as detected in lymphoid tumors such as Burkitt's lymphoma (BL), Hodgkin's disease (HD), post-transplant lymphoproliferative disorders (PTLD) and T-cell lymphomas (e.g. Peripheral T-cell lymphomas; PTCL and Anaplastic large cell lymphomas; ALCL). It is also linked to epithelial tumors such as nasopharyngeal carcinoma (NPC), gastric carcinomas and oral hairy leukoplakia (OHL). In vitro, EBV many studies have demonstrated its ability to transform B cells into lymphoblastoid cell lines (LCLs). Despite these malignancies showing different clinical and epidemiological patterns when studied, genetic studies have suggested that these EBV- associated transformations were characterized generally by low level of virus gene expression with only the latent virus proteins (LVPs) upregulated in both tumors and LCLs. In this review, we summarize some clinical and epidemiological features of EBV- associated tumors. We also discuss how EBV latent genes may lead to oncogenesis in the different clinical malignancie

Defective viral DNA in Epstein-Barr virus-associated oral hairy leukoplakia.

Defective Epstein-Barr virus (EBV) has a deleted and rearranged genome (termed het DNA) that disrupts latency and induces standard EBV to replicate in vitro. We used the polymerase chain reaction to detect, in 2 of 10 patient samples, the junction of abnormally juxtaposed EBV DNA fragments BamHI W and Z, a genomic rearrangement responsible for the biologic activity of het DNA. By sequence analysis, the junction in wild-type defective DNA appears to be similar but not identical to the recombination in the DNA of laboratory strain P3HR-1. The presence of this marker for het DNA in the epithelial lesions of two patients suggests a role for defective EBV in a human pathologic process