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At least 361 records · Page 20Linked to original sources
PubMed2005

Regulation of CD1d expression and function by a herpesvirus infection.

Little is known about the role of CD1d-restricted T cells in antiviral immune responses. Here we show that the lytic replication cycle of the Kaposi sarcoma-associated herpesvirus (KSHV) promotes downregulation of cell-surface CD1d. This is caused by expression of the 2 modulator of immune recognition (MIR) proteins of the virus, each of which promotes the loss of surface CD1d expression following transfection into uninfected cells. Inhibition of CD1d surface expression is due to ubiquitination of the CD1d alpha-chain on a unique lysine residue in its cytoplasmic tail, which triggers endocytosis. Unlike MIR-mediated MHC class I downregulation, however, CD1d downregulation does not appear to include accelerated lysosomal degradation. MIR2-induced downregulation of CD1d results in reduced activation of CD1d-restricted T cells in vitro. KSHV modulation of CD1d expression represents a strategy for viral evasion of innate host immune responses and implicates CD1d-restricted T cells as regulators of this viral infection.

Antigens, CD1↗
PubMed2006

KSHV targets multiple leukocyte lineages during long-term productive infection in NOD/SCID mice.

To develop an animal model of Kaposi sarcoma-associated herpesvirus (KSHV) infection uniquely suited to evaluate longitudinal patterns of viral gene expression, cell tropism, and immune responses, we injected NOD/SCID mice intravenously with purified virus and measured latent and lytic viral transcripts in distal organs over the subsequent 4 months. We observed sequential escalation of first latent and then lytic KSHV gene expression coupled with electron micrographic evidence of virion production within the murine spleen. Using novel technology that integrates flow cytometry with immunofluorescence microscopy, we found that the virus establishes infection in murine B cells, macrophages, NK cells, and, to a lesser extent, dendritic cells. To investigate the potential for human KSHV-specific immune responses within this immunocompromised host, we implanted NOD/SCID mice with functional human hematopoietic tissue grafts (NOD/SCID-hu mice) and observed that a subset of animals produced human KSHV-specific antibodies. Furthermore, treatment of these chimeric mice with ganciclovir at the time of inoculation led to prolonged but reversible suppression of KSHV DNA and RNA levels, suggesting that KSHV can establish latent infection in vivo despite ongoing suppression of lytic replication.

Animals↗
PubMed2025

Repression of varicella zoster virus gene expression during quiescent infection in the absence of detectable histone deposition.

Varicella zoster virus (VZV) is a human-specific herpesvirus that establishes latency in peripheral neurons. The only transcripts detected in infected human trigeminal ganglia (TG) obtained shortly after death correspond to the VZV latency-associated transcript (VLT) and associated VLT-ORF63 splice variants. In vitro studies showed that VLT-ORF63 is translated into a protein (pVLT-ORF63) that induces VZV transcription. The mechanisms that lead to this restricted gene expression and the transition to lytic replication remain unknown, partly due to the difficulty of working with human neurons. In this study, we addressed whether the neuroblastoma-derived cell line SH-SY5Y could serve as a model to investigate the mechanisms that lead to repression of VZV gene expression followed by reactivation. VZV productively infected differentiated SH-SY5Y (dSH-SY5Y) whereas incubation with acyclovir (ACV) inhibited virus replication and induced a progressive repression of the virus. Upon removal of ACV there was production of viral particles in a subset of cells, while others contained non-replicating VZV genomes and VLT-containing transcripts for at least 20 days post-infection (dpi). Exogenous expression of VLT-ORF63 induced productive infection, suggesting that the non-replicating and repressed genomes remained functional. Interestingly, histone deposition was undetectable at VZV genomes in quiescently infected dSH-SY5Y cells, pointing to a potential novel mechanism leading to VZV repression in this neuronal setting.

Humans↗
PubMed2005

Analysis of fusion using a virus-free cell fusion assay.

For enveloped viruses, such as viruses within the herpesvirus family, of which Epstein-Barr virus (EBV) is a member, infection of target cells includes two distinct steps. The first is characterized by the binding of viral envelope glycoproteins to host cellular receptors. After binding, the viral membrane and the cellular membrane fuse. Without both binding and fusion, the virus is not able to enter the host target cell efficiently. Combined with the specific tropism of EBV for primarily two cell types, B lymphocytes and epithelial cells, and the difficulty in inducing lytic replication of EBV in vitro, there is a lack of a good experimental model to study EBV-induced viral fusion. To study fusion more efficiently and effectively, we have employed a virus-free cell-cell fusion assay. In the effector cell, the viral glycoproteins and a plasmid containing the T7 promoter, driving the luciferase gene, are expressed. In the target cell type, T7 RNA polymerase is transfected. Fusion is quantitated by the amount of luciferase expression after mixing of the two cell types. Alongside the fusion assay, a CELISA is performed to determine glycoprotein expression on the effector cells. This methodology has been useful in studying membrane fusion induced by other herpesvirus family members.

B-Lymphocytes↗
PubMed2005

Molecular genetics of DNA viruses: recombinant virus technology.

Recombinant viral genomes cloned onto BAC vectors can be subjected to extensive molecular genetic analysis in the context of E. coli. Thus, the recombinant virus technology exploits the power of prokaryotic genetics to introduce all kinds of mutations into the recombinant genome. All available techniques are based on homologous recombination between a targeting vector carrying the mutated version of the gene of interest and the recombinant virus. After modification, the mutant viral genome is stably introduced into eukaryotic cells permissive for viral lytic replication. In these cells, mutant viral genomes can be packaged into infectious particles to evaluate the effect of these mutations in the context of the complete genome.

Bacteriophage lambda↗
PubMed2005

Cancer scene investigation: how a cold virus became a tumor killer.

Oncolytic therapy is a novel anticancer treatment with attenuated lytic viruses such as adenovirus (Ad). These viruses kill the host cells through their lytic replication cycle and are thus distinct from classical gene therapy viruses, which serve as gene delivery agents and do not replicate. Oncolytic Ads are genetically engineered so as to replicate only in cancer cells. Their replication cycle leads to viral multiplication, the killing of the host cells and spreading of the infection throughout the tumor. Following success in preclinical studies, their anti-tumor potential is now being evaluated in the clinic. Three oncolytic Ads (dl1520, Ad5-CD/TKrep, and CV706) have completed Phase I and II clinical trials in cancer patients where their administration via multiple routes and in combination with chemo- or radiotherapies, has demonstrated overall safety. These viruses are being re-engineered to arm them with additional therapeutic genes, bolstering their oncolytic activity with a bystander effect. For example, Ad5-CD/TKrep delivers a therapeutic prodrug-activating (suicide) gene. These data indicate that oncolytic Ads are a promising novel cancer treatment approach that can be combined with other modalities, such as gene therapy and classical chemo- and radiotherapies. Further improvements to enhance their specificity, targeting and oncolytic activity are needed however, as these first-generation viruses showed modest anti-tumor activity. To improve their efficacy in the clinic, it will be important to devise and incorporate novel monitoring techniques in the clinical trials, such as analysis of viral replication in biopsies and through the use of creative noninvasive imaging technologies.

Forecasting↗
PubMed2005

Modeling early Epstein-Barr virus infection in Drosophila melanogaster: the BZLF1 protein.

Epstein-Barr virus (EBV) is the causative agent of infectious mononucleosis and is associated with several forms of cancer, including lymphomas and nasopharyngeal carcinoma. The EBV immediate-early protein BZLF1 functions as a transcriptional activator of EBV early gene expression and is essential for the viral transition between latent and lytic replication. In addition to its role in the EBV life cycle, BZLF1 (Z) also has profound effects upon the host cellular environment, including disruption of cell cycle regulation, signal transduction pathways, and transcription. In an effort to understand the nature of Z interactions with the host cellular environment, we have developed a Drosophila model of early EBV infection, where we have expressed Z in the Drosophila eye. Using this system, we have identified a highly conserved interaction between the Epstein-Barr virus Z protein and shaven, a Drosophila homolog of the human Pax2/5/8 family of genes. Pax5 is a well-characterized human gene involved with B-cell development. The B-cell-specific Pax5 also promotes the transcription of EBV latent genes from the EBV Wp promoter. Our work clearly demonstrates that the Drosophila system is an appropriate and powerful tool for identifying the underlying genetic networks involved in human infectious disease.

Animals↗
PubMed2000

Virological and molecular characterisation of a new B lymphoid cell line, established from an AIDS patient with primary effusion lymphoma, harbouring both KSHV/HHV8 and EBV viruses.

We report here a new case of primary effusion lymphoma (PEL), occurring in a French homosexual HIV-1 infected male with a pericardial, pleural and mesenteric tumour dissemination, and the establishment from his pleural effusion of a new cell line, Cra-BCBL, dually infected by EBV and KSHV/HHV8. Cra-BCBL cells are of B-cell origin as judged by their clonal immunoglobulin heavy chain (IgH) gene rearrangement, identical to that of the parental tumour. Both the cell line and the lymphoma cells expressed CD38 and CD45 antigens but no classical B-cell or T-cell lineage-restricted antigens. Cra-BCBL harbours a type I EBV virus, expressing a latency type II. Expression of KSHV/HHV8 ORF72 and ORF75 was detected by RT/PCR. In addition, KSHV lytic replication could be induced by treatment by n-butyrate. An equivalent and high copy number of KSHV genomes (20 to 200 copies by cell) was detected both in the primary tumour cells and in the cell line. Southern blot (SB) analysis of EBV terminal repeats (TR) displayed the same unique band in the cell line DNA and in the original tumour cells, consistent with a monoclonal infection of EBV. Furthermore, SB analysis of KSHV/HHV8 TR revealed the same hybridisation pattern between Cra-BCBL and the effusion cells, with a common band at around 30-40 kb corresponding to the fused termini of the viral episomes and a 5 Kb rearranged fragment. The new cell line characterised here could be a useful model to study interactions between two human herpes viruses and their contribution to lymphomagenesis.

Adult↗
PubMed2004

Herpes simplex virus-specific CD8+ T cells can clear established lytic infections from skin and nerves and can partially limit the early spread of virus after cutaneous inoculation.

HSV infects skin or mucosal epithelium as well as entering the sensory nerves and ganglia. We have used TCR-transgenic T cells specific for the immunodominant class I-restricted determinant from HSV glycoprotein B (gB) combined with a flank zosteriform model of infection to examine the ability of CD8+ T cells to deal with infection. During the course of zosteriform disease, virus rapidly spreads from the primary inoculation site in the skin to sensory dorsal root ganglia and subsequently reappears in the distal flank. Virus begins to be cleared from all sites about 5 days after infection when gB-specific CD8+ T cells first appear within infected tissues. Although activated gB-specific effectors can partially limit virus egress from the skin, they do so only at the earliest times after infection and are ineffective at halting the progression of zosteriform disease once virus has left the inoculation site. In contrast, these same T cells can completely clear ongoing lytic replication if transferred into infected immunocompromised RAG-1-/- mice. Therefore, we propose that the role of CD8+ T cells during the normal course of disease is to clear replicating virus after infection is well established rather than limit the initial spread of HSV from the primary site of inoculation.

Administration, Cutaneous↗
PubMedDate not supplied

Identification of a major latent nuclear antigen, LNA-1, in the human herpesvirus 8 genome.

OBJECTIVES: Human herpesvirus 8 (HHV-8) is strongly associated with all forms of Kaposi's sarcoma (KS) and with primary effusion lymphomas (PEL). KS patients' sera are immunoreactive against discrete nuclear localizing antigens in PEL cell lines. This study sought to identify and characterize these nuclear localizing proteins. STUDY DESIGN/METHODS: KS patients' sera were used to screen a cDNA expression library derived from a PEL cell line (BCP-1) latently infected with HHV-8. RESULTS: An HHV-8-specific cDNA clone was isolated. It encoded one partial and two complete open reading frames (ORFs): ORF 73, ORF 72 (v-cyclin), and K13, respectively. The immunodominant epitope was mapped to the C-terminal domain of ORF 73. Analysis with the KS patients' sera of HEK 293 cells transfected with a clone encompassing the complete coding region of ORF 73, ORF 72, and K13 gave a nuclear immunofluorescence pattern similar to that observed in BCP-1 cells. Western blot analysis with KS patients' sera of transfected HEK 293 cells revealed an immunoreactive protein of 220 to 230 kD that was similar to that observed previously in PEL cell lines. After induction of lytic replication of HHV-8 in BCP-1 cells with n-butyrate, we observed a major reduction in the expression of an ORF 73-specific 6.6-kb mRNA, indicating that this region is under latent control. CONCLUSIONS: These data identify a region of HHV-8 encoding for a major immunoreactive latent nuclear antigen (LNA-1), analogous to the Epstein-Barr virus latent nuclear antigens.

Amino Acid Sequence↗
PubMedDate not supplied

[Role of Epstein-Barr virus in the pathogenesis of lymphogranulomatosis. Immunohistochemical and molecular-biological (hybridization in situ) research].

EBV was found in 72.7% of 66 LGM patients aged from 4 to 76 years. EBV occurred in 100% of lymphoid depletion, 81% of mixed-cell variant and in 66.6% of nodular sclerosis. The occurrence of virus-positive cases was significantly higher at the age of under 10 years and over 50 years (100%). In the intermediate group it was 65.4 (p < 0.01). Necrotic changes in the lymph nodes were observed more frequently (p < 0.05) when EBV was present. The virus-positive cases of mixed-cell LGM are characterized by increased number of tumor and plasma cells (p < 0.05). EBV was also in a latent state without signs of lytic replication. The influence of the virus manifested in higher expression of antigens CD30 (p < 0.05) and bcl oncoproteins (p < 0.01) as well as in weak CD79 expression (p < 0.05).

Adolescent↗
PubMed2004

[Polyomavirus nephropathy: pathogenesis, morphological and clinical aspects].

The polyoma-BK-virus strain was said to be "in search" of a disease. The search is finally over. Since the mid 1990's, when new third generation immunosuppressive drug regimens were introduced into the routine management of renal allograft recipients, the polyoma-BK-virus (allograft) nephropathy (BKN) has gained increasing clinical interest. BKN is currently the most common infection affecting renal allografts with a prevalence of 1% up to 10% reported in various transplant centers world-wide. It can lead to chronic allograft dysfunction and eventual graft loss in more than 50% of cases (observed in some institutions). BKN is most likely caused by the reactivation of latent BK viruses which enter under sustained and intensive immunosuppression into a productive and lytic replicative cycle. BKN is typically limited to the kidney transplant. It is histologically defined by the presence of intranuclear viral inclusion bodies in tubular and parietal glomerular epithelial cells. Different variants of polyomavirus inclusion bodies (types 1 through 4) and adjunct techniques [immunohistochemistry, electron microscopy and polymerase chain reaction (PCR)] that are used for proper characterization are described. Virally induced severe tubular injury is the morphologic correlate for the clinically observed allograft dysfunction. Special emphasis is placed on the pathogenesis leading from latent to productive BK-Virus infections and on the clinical and pathophysiological significance of different histological stages of BKN. Risk factors promoting disease as well as clues to diagnose BKN and concurrent acute allograft rejection are discussed. The pathologist's role in patient management using the detection of polyomavirus inclusion bearing decoy cells in the urine, plasma PCR analyses, and graft biopsies is highlighted.

BK Virus↗
PubMed1989

Inhibition by parvovirus H-1 of the formation of tumors in nude mice and colonies in vitro by transformed human mammary epithelial cells.

The formation of tumors in adult nude mice from transformed human mammary epithelial cells was drastically inhibited (greater than 80%) both after coinjection of tumoral cells and virus or after a single s.c. injection of parvovirus H-1 at the site of cell implantation prior to tumor formation. Moreover, when injected i.v. in animals bearing preformed tumors, H-1 virus was able to slow down and even in some cases to revert neoplastic growth. Thus, H-1 virus achieved the suppression of implanted tumors of human origin under conditions where the immune antitumor mechanisms of the recipient animals were dramatically impaired. Viral infection was not accompanied by detectable deleterious side effects. Imprints of H-1 virus DNA were found in one residual tumor. Normal human mammary epithelial cells were also compared with homologous transformed cells, either derived from tumors (three lines) or containing simian virus 40 (one line), for their susceptibility to the lytic replication of H-1 virus in vitro. Transformed cell lines were more sensitive to virus-induced killing than secondary cultures of normal cells. Moreover, the former had much greater abilities than the latter to amplify viral DNA and to express the viral nonstructural protein NS-1. Altogether, these results are compatible with the idea that the oncosuppressive activity exerted by H-1 virus may be mediated, at least in part, by virus replication in developing tumors.

Animals↗
PubMed1994

Biochemical and genetic studies of Epstein-Barr virus latent membrane protein 2.

Epstein-Barr Virus (EBV) causes infectious mononucleosis in normal adolescents and malignant B lymphocyte proliferation in immune compromised patients, in marmosets, or upon transfer of infected human B lymphocytes into SCID mice. EBV is also etiologically associated with African Burkitt's lymphoma, Hodgkin's Disease, and nasopharyngeal cancer. EBV transformed, latently infected B lymphocytes contain EBV episomes and eight virus encoded proteins. Six are nuclear proteins (EBNAs) and two are the integral membrane proteins, LMP1 and LMP2. These eight proteins are presumed to mediate latent virus infection or B lymphocyte proliferation and are thus under intense scrutiny. Besides EBNA1, which is required for episome maintenance, LMP1 and LMP2, are the two transformation associated proteins that are most consistently detected in EBV related malignancies, and the LMP2 message is the only message detected in PCR analysis of B lymphocytes from individuals harboring EBV latent infections. LMP2 associates with src family tyrosine kinases, a 70 kda cell phosphoprotein, LMP1 and several other unidentified cell proteins. LMP1 is a key mediator of EBV's effects on inducing B lymphocyte activation and adhesion molecules and is a transforming oncogene in rodent fibroblasts. The association of these two EBV encoded membrane proteins could create a macromolecular complex mediating constitutive B lymphocyte activation through normal cell signal transduction pathways. LMP2 might may control activation of lytic replication or down regulate the activation state of EBV infected cells allowing persistence in the human host.

Amino Acid Sequence↗
PubMedDate not supplied

Potential in vitro activity of Kutapressin against Epstein-Barr virus.

BACKGROUND: Kutapressin (KU), a porcine liver extract with bradykinin-potentiating effects but no vitamin B 12 activity, has been used in the treatment of Herpes zoster. We examined a phenol-free preparation of this drug for in vitro activity against Epstein-Barr Virus (EBV). MATERIALS AND METHODS: Immortalization-inhibition assays were used to assess EBV infectivity. Mitogen stimulation and cell viability assays were used to assess kutapression toxicity. Lytic replication assays and flow cytometry were used to assess the mechanism of drug activity. RESULTS: Seventy-five hundred mcg/ml of KU blocked the infection of 2 x 10(5) human umbilical cord mononuclear cells when added together with two strains of EBV (B95-8 and FF41). Doses as low as 250 mcg/ml were occasionally effective as well. Unlike acyclovir, KU does not inhibit viral DNA polymerase nor does it appear to compete with EBV as it binds to its receptor on the B-cell surface. CONCLUSIONS: The mechanism whereby KU may inhibit EBV immortalization remains to be determined. KU, a drug which is safe in humans, deserves further study as an agent with potential to block EBV-induced immortalization of B-lymphocytes.

Animals↗
PubMed1997

Cloning and functional characterization of the origin of lytic-phase DNA replication of rat cytomegalovirus.

A cis-acting sequence within the rat cytomegalovirus (RCMV) genome (oriLyt) that directs initiation of lytic-phase DNA replication is identified in this report. RCMV oriLyt was localized within a 4.3 kb NcoI fragment that is situated immediately upstream of the gene encoding the major DNA-binding protein. The activity of oriLyt was investigated in a transient replication assay, in which the ability of plasmid constructs to promote DNA replication was tested. Replication of oriLyt-containing plasmids was autonomous and resulted in the generation of high-molecular-mass concatemers of head-to-tail-linked plasmid oligomers. oriLyt-mediated replication was found to depend on viral DNA polymerase activity supplied by RCMV infection. The sequence required for oriLyt function was found to reside within a 3.3 kb HincII-NcoI fragment. The RCMV oriLyt sequence is highly complex, containing 23 direct repeats (DRs) and 16 inverted repeats (IRs) of lengths greater than 10 bp. Two of the DRs (DR21 and DR22) are exceptionally large, being 80 and 88 bp in length, respectively. In addition, two sequence elements (of 127 and 120 bp) with dyad symmetry were identified within oriLyt. Although the sequence similarity of RCMV oriLyt with its human cytomegalovirus counterpart is limited, there is a striking resemblance in the overall organization of several IRs and DRs within both sequences.

Animals↗
PubMed2001

Identification of the rhesus macaque rhadinovirus lytic origin of DNA replication.

We have identified a lytic origin of DNA replication (oriLyt) for rhesus macaque rhadinovirus (RRV), the rhesus macaque homolog of human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus. RRV oriLyt maps to the region of the genome between open reading frame 69 (ORF69) and ORF71 (vFLIP) and is composed of an upstream A+T-rich region followed by a short (300-bp) downstream G+C-rich DNA sequence. A set of overlapping cosmids corresponding to the entire genome of RRV was capable of complementing oriLyt-dependent DNA replication only when additional ORF50 was supplied as an expression plasmid in the transfection mixture, suggesting that the level of ORF50 protein originating from input cosmid DNA was insufficient. The requirement of RRV ORF50 in the cotransfection replication assay may also suggest a direct role for this protein in DNA replication. RRV oriLyt shares a high degree of nucleotide sequence and G+C base distribution with the corresponding loci in HHV-8.

Animals↗
PubMed1993

cis-acting elements in the lytic origin of DNA replication of Epstein-Barr virus.

oriLyt, the cis-acting element of Epstein-Barr virus, mediates viral DNA replication in the lytic phase of the virus's life cycle. Oligonucleotide-directed in vitro mutagenesis of oriLyt plasmids allowed the identification of two noncontiguous components within the complex structure of oriLyt. Both components were indispensable for DNA replication of this origin. The upstream component colocalized with the promoter of the viral BHLF1-encoding gene, and mutants affecting DNA replication affected RNA transcription, too. The second component crucial for oriLyt function was determined to be 40 bp long and positioned approximately 530 bp downstream. It was dispensable for transcriptional transactivation but it was absolutely required for replication. Thus, the overall design of oriLyt has striking similarity to multipartite regulatory elements of transcription, consisting of proximal promoters and distal enhancers, but special elements are exclusively dedicated to DNA replication.

Base Sequence↗