Human herpesvirus-8: detection of novel herpesvirus-like DNA sequences in Kaposi's sarcoma and other lesions

Pemphigus: trigger and predisposing factors

Pemphigus is a life-threatening autoimmune blistering disease affecting skin and mucous membranes. Despite its etiopathogenesis remains largely unknown, several trigger and predisposing factors have been reported. Pemphigus is caused by autoantibodies that target desmoglein 1 and desmoglein 3, impacting desmosome function. However, circulating autoantibodies are often the consequence of a precipitating factor that occurs in predisposed individuals. This review aims to describe and discuss almost all trigger and predisposing factors reported as possible or probable cause of the disease. Among the reported trigger factors that may induce or exacerbate pemphigus, we have found of particular interest: drug intake (especially thiol- and phenol-containing compounds), vaccines, infections, as well as some reports about pregnancy, radiations, emotional stress, pesticides and physical trauma. Moreover, we discuss the possible role of food intake in pemphigus onset and particular attention is given to dietary factors containing thiol, phenol and tannin compounds. A trigger factor is "the straw that breaks the camel's back," and often acts together with predisposing factors. Here we discuss how pemphigus onset may be influenced by genetic susceptibility and comorbidities like thyroid diseases, malignancies and other autoimmune disorders. To identify other hitherto unknown trigger and predisposing factors, well designed prospective studies are needed. In this context, future research should explore their connection with the aim to advance our understanding of pemphigus pathogenesis.

Autophagy as a molecular target for cancer treatment

Autophagy is an evolutionarily conserved catabolic mechanism, by which eukaryotic cells recycle or degrades internal constituents through membrane-trafficking pathway. Thus, autophagy provides the cells with a sustainable source of biomolecules and energy for the maintenance of homeostasis under stressful conditions such as tumor microenvironment. Recent findings revealed a close relationship between autophagy and malignant transformation. However, due to the complex dual role of autophagy in tumor survival or cell death, efforts to develop efficient treatment strategies targeting the autophagy/cancer relation have largely been unsuccessful. Here we review the two-faced role of autophagy in cancer as a tumor suppressor or as a pro-oncogenic mechanism. In this sense, we also review the shared regulatory pathways that play a role in autophagy and malignant transformation. Finally, anti-cancer therapeutic agents used as either inhibitors or inducers of autophagy have been discussed.

The crystal structure of KSHV ORF57 reveals dimeric active sites important for protein stability and function

Kaposi's sarcoma-associated herpesvirus (KSHV) is a γ-herpesvirus closely associated with Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman disease. Open reading frame 57 (ORF57), a viral early protein of KSHV promotes splicing, stability and translation of viral mRNA and is essential for viral lytic replication. Previous studies demonstrated that dimerization of ORF57 stabilizes the protein, which is critical for its function. However, the detailed structural basis of dimerization was not elucidated. In this study, we report the crystal structures of the C-terminal domain (CTD) of ORF57 (ORF57-CTD) in both dimer at 3.5 Å and monomer at 3.0 Å. Both structures reveal that ORF57-CTD binds a single zinc ion through the consensus zinc-binding motif at the bottom of each monomer. In addition, the N-terminal residues 167-222 of ORF57-CTD protrudes a long "arm" and holds the globular domains of the neighboring monomer, while the C-terminal residues 445-454 are locked into the globular domain in cis and the globular domains interact in trans. In vitro crosslinking and nuclear translocation assays showed that either deletion of the "arm" region or substitution of key residues at the globular interface led to severe dimer dissociation. Introduction of point mutation into the zinc-binding motif also led to sharp degradation of KSHV ORF57 and other herpesvirus homologues. These data indicate that the "arm" region, the residues at the globular interface and the zinc-binding motif are all equally important in ORF57 protein dimerization and stability. Consistently, KSHV recombinant virus with the disrupted zinc-binding motif by point mutation exhibited a significant reduction in the RNA level of ORF57 downstream genes ORF59 and K8.1 and infectious virus production. Taken together, this study illustrates the first structure of KSHV ORF57-CTD and provides new insights into the understanding of ORF57 protein dimerization and stability, which would shed light on the potential design of novel therapeutics against KSHV infection and related diseases.

Distinct roles for extracellular signal-regulated kinase 1 (ERK1) and ERK2 in the structure and production of a primate gammaherpesvirus

During their progression from intranuclear capsids to mature trilaminar virions, herpesviruses incorporate an extensive array of viral as well as a smaller subset of cellular proteins. Our laboratory previously reported that rhesus monkey rhadinovirus (RRV), a close homolog of the human pathogen Kaposi's sarcoma-associated herpesvirus (KSHV), is comprised of at least 33 different virally encoded proteins. In the current study, we found that RRV infection activated the extracellular signal-regulated kinase (ERK) pathway and nascent virions preferentially incorporated the activated form of ERK2 (pERK2) into the tegument. This was evident even in the face of greatly diminished stores of intracellular ERK2, suggesting a clear bias toward the incorporation of pERK2 into the RRV particle. Similar to earlier findings with KSHV, activation of ERK was essential for the production of lytic viral proteins and virions. Knockdown of intracellular ERK, however, failed to inhibit virus production, likely due to maintenance of residual pools of intracellular pERK2. Paradoxically, selective knockdown of ERK1 enhanced virion production nearly 5-fold and viral titers more than 10-fold. These data are the first to implicate ERK1 as a negative regulator of lytic replication in a herpesvirus and the first to demonstrate the incorporation of an activated signaling molecule within a herpesvirus. Together, the results further our understanding of how herpesviruses interact with host cells during infection and demonstrate how this family of viruses can exploit cellular signal transduction pathways to modulate their own replication.

Kaposi sarcoma in the setting of cushing disease

OBJECTIVE

To report a case of a human immunodeficiency virus (HIV)-negative Kaposi sarcoma (KS) associated with Cushing disease (CD).

METHODS

The details of case presentation, evaluation, diagnosis, and treatment are presented and cases of KS and CD published before November 1, 2010 on PubMed and Scopus are reviewed.

RESULTS

A 54-year-old Hispanic HIV-negative man presented with typical signs and symptoms of CD (easy bruisability, proximal muscle wasting, and abdominal fat pads). Numerous raised, purplish, nonblanching plaques 0.5 to 2 cm in diameter extended throughout his lower extremities. Biochemical tests and pituitary magnetic resonance imaging confirmed CD. A lesion biopsy showed atypical vascular proliferation positive by immunohistochemistry for human herpesvirus 8 (HHV-8), consistent with KS. He underwent 2 transsphenoidal surgeries followed by a bilateral adrenalectomy. After recovery, his KS was treated with a systemic combination of liposomal doxorubicin and paclitaxel.

CONCLUSION

The occurrence of CD and KS is rare. Specific therapy for CD and chemotherapy for KS are effective in the treatment of KS associated with CD.

Infectious agents and lymphoma

In the past 25 years revelations on the genesis of human cancer have come at an increasing pace. Research on oncogenic infectious agents, especially viruses, has helped us to understand the process of malignant transformation of cells because the cellular events in viral-driven transformation mirror, often brilliantly, basic cellular processes that culminate in cancer, even those not associated with viruses. Infectious agents, especially viruses, account for several of the most common malignancies-up to 20% of all cancers. Some of these cancers are endemic, with a high incidence in certain geographic locations, but sporadic/lower incidence in other parts of the world. Lymphomas arise frequently in association with infectious agents such as Epstein-Barr virus, human immunodeficiency virus, human herpes virus 8, Helicobacter pylori, and hepatitis C virus. In this review, we will focus on the association between infectious agents and lymphomas, with a look at the molecular mechanisms they use to disturb cell regulation and eventually result in cancer.

The single RBP-Jkappa site within the LANA promoter is crucial for establishing Kaposi's sarcoma-associated herpesvirus latency during primary infection

Kaposi's sarcoma-associated herpesvirus (KSHV; or human herpesvirus 8 [HHV8]) is implicated in the pathogenesis of many human malignancies including Kaposi's sarcoma (KS), multicentric Castleman's disease (MCD), and primary effusion lymphoma (PEL). KSHV infection displays two alternative life cycles, referred to as the latent and lytic or productive cycle. Previously, we have reported that the replication and transcription activator (RTA), a major lytic cycle transactivator, contributes to the development of KSHV latency by inducing latency-associated nuclear antigen (LANA) expression during early stages of infection by targeting RBP-Jκ, the master regulator of the Notch signaling pathway. Here, we generated a bacterial artificial chromosome (BAC) KSHV recombinant virus with a deletion of the RBP-Jκ site within the LANA promoter to evaluate the function of the RBP-Jκ cognate site in establishing primary latent infection. The results showed that genetic disruption of the RBP-Jκ binding site within the KSHV LANA promoter led to enhanced expression of the KSHV-encoded immediate early RTA, resulting in an increase in lytic replication during primary infection of human peripheral blood mononuclear cells (PBMCs). This system provides a powerful tool for use in indentifying additional cellular and viral molecules involved in LANA-mediated latency maintenance during the early stages of KSHV infection.

Kaposin-B enhances the PROX1 mRNA stability during lymphatic reprogramming of vascular endothelial cells by Kaposi's sarcoma herpes virus

Kaposi's sarcoma (KS) is the most common cancer among HIV-positive patients. Histogenetic origin of KS has long been elusive due to a mixed expression of both blood and lymphatic endothelial markers in KS tumor cells. However, we and others discovered that Kaposi's sarcoma herpes virus (KSHV) induces lymphatic reprogramming of blood vascular endothelial cells by upregulating PROX1, which functions as the master regulator for lymphatic endothelial differentiation. Here, we demonstrate that the KSHV latent gene kaposin-B enhances the PROX1 mRNA stability and plays an important role in KSHV-mediated PROX1 upregulation. We found that PROX1 mRNA contains a canonical AU-rich element (ARE) in its 3′-untranslated region that promotes PROX1 mRNA turnover and that kaposin-B stimulates cytoplasmic accumulation of the ARE-binding protein HuR through activation of the p38/MK2 pathway. Moreover, HuR binds to and stabilizes PROX1 mRNA through its ARE and is necessary for KSHV-mediated PROX1 mRNA stabilization. Together, our study demonstrates that kaposin-B plays a key role in PROX1 upregulation during lymphatic reprogramming of blood vascular endothelial cells by KSHV.

Kaposi's sarcoma (KS) is the most common cancer in HIV-positive patients and KS-associated herpes virus (KSHV) was identified as its causing agent. We and others have discovered that when the virus infects endothelial cells of blood vessels, KSHV reprograms the cell type resembling endothelial cells in lymphatic vessels. Although endothelial cells of the blood vascular system and of the lymphatic system share functional similarities, the cell type-reprogramming does not occur under a normal physiological condition. Therefore, cell-fate reprogramming by the cancer-causing virus KSHV provides an important insight into the molecular mechanism for viral pathogenesis. Our current study investigates the molecular mechanism underlying the KSHV-mediated cell fate reprogramming. We identified that a KSHV latent gene kaposin-B plays an important role in KSHV-mediated regulation of PROX1 to promote PROX1 mRNA stability. This study will provide a better understanding on the tumorigenesis and pathogenesis of KS with a potential implication toward new KS therapy.

Possible DNA viral factors of human breast cancer

Viruses are considered to be one of the high-risk factors closely related to human breast cancer. However, different studies of viruses in breast cancer present conflicting results and some of these works remain in dispute. DNA viruses, such as specific types of human papillomaviruses (HPV), Epstein–Barr virus (EBV), human cytomegalovirus (HCMV), herpes simplex virus (HSV), and human herpes virus type 8 (HHV-8), have emerged as causal factors of some human cancers. These respective exogenous viruses and the possibility of multiple viral factors are discussed in this review.

1 Alpha,25-dihydroxyvitamin D3 and its TX527 analog inhibit the growth of endothelial cells transformed by Kaposi sarcoma-associated herpes virus G protein-coupled receptor in vitro and in vivo

The Kaposi sarcoma-associated herpes virus-G protein-coupled receptor is a key molecule in the pathogenesis of Kaposi sarcoma, playing a central role in promoting vascular endothelial growth factor-driven angiogenesis and spindle cell proliferation. We studied the effects of 1 alpha,25-dihydroxyvitamin D(3) [1 alpha,25(OH)(2)D(3)] and the analog TX527 on the proliferation of endothelial cells (SVECs) and SVECs transformed by the viral G protein-coupled receptor (SVEC-vGPCR). 1 alpha,25(OH)(2)D(3) and TX527 decreased SVEC-vGPCR and SVEC numbers, the response being time dependent and similar in both cell lines. Vitamin D receptor (VDR) levels increased on treatment with 10 nm 1 alpha,25(OH)(2)D(3) or 1 nm TX527 in a time-dependent manner (1.5-24 h) in SVECs and SVEC-vGPCR. Basal VDR levels were increased in SVEC-vGPCR. The antiproliferative effects were accompanied by reduction in cyclin D1 and accumulation of p27 in SVECs but not SVEC-vGPCR. Induction of VDR was blocked by transfection of short hairpin RNA against VDR in SVEC-vGPCR and the antiproliferative effects of 1 alpha,25(OH)(2)D(3) and TX527 were decreased, involving the VDR genomic pathway in the hormone and analog mechanism of action. In vivo experiments showed that 1 alpha,25(OH)(2)D(3) and TX527 decreased SVEC-vGPCR tumor progression when the tumor cells were implanted in nude mice. In conclusion, we have demonstrated that 1 alpha,25(OH)(2)D(3) and its TX527 analog have antiproliferative effects on the growth of endothelial cells transformed by the vGPCR in vitro and in vivo, the vitamin D receptor being part of the inhibitory mechanism of action.

Cellular corepressor TLE2 inhibits replication-and-transcription- activator-mediated transactivation and lytic reactivation of Kaposi's sarcoma-associated herpesvirus

Replication and transcription activator (RTA) encoded by open reading frame 50 (ORF50) of Kaposi's sarcoma-associated herpesvirus (KSHV) is essential and sufficient to initiate lytic reactivation. RTA activates its target genes through direct binding with high affinity to its responsive elements or by interaction with cellular factors, such as RBP-Jkappa, Ap-1, C/EBP-alpha, and Oct-1. In this study, we identified transducin-like enhancer of split 2 (TLE2) as a novel RTA binding protein by using yeast two-hybrid screening of a human spleen cDNA library. The interaction between TLE2 and RTA was confirmed by glutathione S-transferase (GST) binding and coimmunoprecipitation assays. Immunofluorescence analysis showed that TLE2 and RTA were colocalized in the same nuclear compartment in KSHV-infected cells. This interaction recruited TLE2 to RTA bound to its recognition sites on DNA and repressed RTA auto-activation and transactivation activity. Moreover, TLE2 also inhibited the induction of lytic replication and virion production driven by RTA. We further showed that the Q (Gln-rich), SP (Ser-Pro-rich), and WDR (Trp-Asp repeat) domains of TLE2 and the Pro-rich domain of RTA were essential for this interaction. RBP-Jkappa has been shown previously to bind to the same Pro-rich domain of RTA, and this binding can be subject to competition by TLE2. In addition, TLE2 can form a complex with RTA to access the cognate DNA sequence of the RTA-responsive element at different promoters. Intriguingly, the transcription level of TLE2 could be upregulated by RTA during the lytic reactivation process. In conclusion, we identified a new RTA binding protein, TLE2, and demonstrated that TLE2 inhibited replication and transactivation mediated by RTA. This provides another potentially important mechanism for maintenance of KSHV viral latency through interaction with a host protein.

Wildlife cancer: a conservation perspective

Until recently, cancer in wildlife was not considered to be a conservation concern. However, with the identification of Tasmanian devil facial tumour disease, sea turtle fibropapillomatosis and sea lion genital carcinoma, it has become apparent that neoplasia can be highly prevalent and have considerable effects on some species. It is also clear that anthropogenic activities contribute to the development of neoplasia in wildlife species, such as beluga whales and bottom-dwelling fish, making them sensitive sentinels of disturbed environments.

Identification and characterization of the promoter region of Kaposi's sarcoma-associated herpesvirus ORF11

Open reading frame 11 (ORF11) of Kaposi's sarcoma-associated herpesvirus belongs to a herpesviral homologous protein family that is conserved among members of the gamma-herpesvirus subfamily. Little is known about the function of ORF11 and how this viral gene is regulated in KSHV life cycle. In this study, we have characterized the major transcript of the ORF11 gene, which is located adjacent and in the opposite orientation to a well-characterized viral IL-6 gene. Northern blot analysis revealed that the ORF11 gene is lytic viral gene with delayed-early expression kinetics. We have determined the 5' and 3' untranslated region of the unspliced ORF11 transcript and identified both the transcription start site and the transcription termination site. Core promoter region, representing ORF11 promoter activity, was mapped to a 160nt fragment 5' most proximal to the transcription start site. A functional TATA box was identified in the core promoter region. We also found that the characterized ORF11 gene promoter region is not responsive to Rta, the KSHV lytic switch protein. Our data help to elucidate transcription regulation of the KSHV ORF11 gene and to understand the biology of ORF11 in KSHV life cycle.

AIDS and non AIDS-related malignant lymphoma in Tanzania

BACKGROUND

Malignant lymphoma (ML) in HIV patients, are second in frequency to Kaposi's sarcoma (AKS) as AIDS-defining tumors. In Africa the frequency of AIDS-related lymphoma (ARL) is rare and the findings are controversial. Kaposi's sarcoma (KS) lesions are now causally associated with KSHV/HHV-8 but whether African ARL shows this association is not clear.

METHOD

Cancer registry data was reviewed for retrospective cases. Both retrospective and prospective lymphoma cases were classified according to the revised European-American (REAL) classification. Immunephenotyping was performed on both frozen and fixed paraffin sections. Viral DNA was assessed by polymerase chain reaction (PCR) of formalin fixed or frozen biopsies. In situ hybridization (ISH) was used to determine the presence of EBV encoded RNA (EBER).

OBJECTIVES

To determine the frequency and type of AIDS and non-AIDS related malignant lymphoma in Tanzania and a possible co-association with KSHV/HHV-8 and EBV.

RESULTS

An overall increasing tendency for ML in Tanzania was observed during 1991-94 and a clear increase from 1993. The tumors were classified as Burkitt's (6), diffuse large cell (10), precursor-B lymphoblastic (1) and Hodgkin's disease (5) from HIV positive and negative patients. Ten (40%) high grade ML and three Hodgkin's lymphoma from HIV patients had HHV-8 DNA. These findings were not related to age, sex or type of lymphoma. There was no association of HHV-8 with the lymphoma cells. Epstein-Barr virus (EBV) was demonstrable in most (13/18; 72%) of the tested tumors and seven (31.8%) had both HHV-8 and EBV.

CONCLUSIONS

This study suggests an overall increased frequency of ML patients infected with HHV-8 in Tanzania particularly in HIV patients which may result from the well established high HHV-8 prevalence in the general population, but HHV-8 was not associated with ARL pathogenesis as reflected by lack of tumor cell infection. As opposed to EBV, measures targeting HHV-8 for control of ML may therefore not be appropriate.

Intravascular Kaposi's sarcoma - a hitherto unrecognized phenomenon

BACKGROUND

Based on the spectrum of histological features, Kaposi's sarcoma (KS) is grouped into patch, plaque and nodular stages. The histological changes overlap, especially with lesional evolution. To date, intravascular KS is undocumented.

METHODS

A clinicopathological description of six cases of intravascular KS.

RESULTS

Clinical: There were four men and two women (mean age = 65 years). Four patients, who presented clinically with classic (sporadic) KS, developed solitary violaceous nodules on the extremities. Two patients with acquired immune deficiency syndrome-related KS had disseminated cutaneous KS lesions in all stages of evolution. Six months to 3 years follow-up showed no evidence of systemic KS in any of the patients. Histopathology: Exclusive intravascular growth was seen in five patients. The vascular channels, highlighted by mural immunostaining with desmin and anti-smooth muscle actin, had the histological features of veins. Intravascular growth was characterized by interlacing fascicles of human herpesvirus 8, CD31 and CD34-positive spindle cells with formation of cleft-like spaces, erythrocyte extravasation, hyaline globules and a lymphoplasmacytic infiltrate. One patient had a proliferation of irregular, vascular channels in the desmin in addition to the intravenous growth.

CONCLUSION

Intravascular KS is a peculiar hitherto unrecognized morphological variant of KS that does not seem to be associated with an increased risk of aggressive behaviour.

Sarcoma

Sarcomas comprise a heterogeneous group of mesenchymal neoplasms. They can be grouped into 2 general categories, soft tissue sarcoma and primary bone sarcoma, which have different staging and treatment approaches. This review includes a discussion of both soft tissue sarcomas (malignant fibrous histiocytoma, liposarcoma, leiomyosarcoma, synovial sarcoma, dermatofibrosarcoma protuberans, angiosarcoma, Kaposi sarcoma, gastrointestinal stromal tumor, aggressive fibromatosis or desmoid tumor, rhabdomyosarcoma, and primary alveolar soft-part sarcoma) and primary bone sarcomas (osteosarcoma, Ewing sarcoma, giant cell tumor, and chondrosarcoma). The 3 most important prognostic variables are grade, size, and location of the primary tumor. The approach to a patient with a sarcoma begins with a biopsy that obtains adequate tissue for diagnosis without interfering with subsequent optimal definitive surgery. Subsequent treatment depends on the specific type of sarcoma. Because sarcomas are relatively uncommon yet comprise a wide variety of different entities, evaluation by oncology teams who have expertise in the field is recommended. Treatment and follow-up guidelines have been published by the National Comprehensive Cancer Network (www.nccn.org).

The human herpesvirus 8 chemokine receptor vGPCR triggers autonomous proliferation of endothelial cells

We have used a novel conditional transgenic system to study the mechanisms of angioproliferation induced by viral G protein-coupled receptor (vGPCR), the constitutively active chemokine receptor encoded by human herpesvirus 8 (HHV8, also known as Kaposi sarcoma herpesvirus). Using this system, we were able to control temporal expression of vGPCR and to monitor its expression in situ via the use of the surrogate marker LacZ. Upon treatment with doxycycline (DOX), cells expressing vGPCR and LacZ (vGPCR/LacZ(+) cells) progressively accumulated in areas where angioproliferation was observed. Sorted vGPCR/LacZ(+) cells from angiogenic lesions expressed markers characteristic of endothelial progenitor cells, produced angiogenic factors, and proliferated in vitro. Prolonged treatment of transgenic mice with DOX led to development of tumors in the skin of ears, tail, nose, and paws. vGPCR/LacZ(+) cells were frequent in early lesions but scarce within these tumors. Finally, transfer of vGPCR/LacZ(+) cells into Rag1(-/-) mice treated with DOX led to angioproliferation and, with time, to development of tumors containing both vGPCR/LacZ(+) and vGPCR/LacZ(-) cells. Taken together, these results indicate that vGPCR triggers angioproliferation directly and suggest a novel role for this molecule in the pathogenesis of Kaposi sarcoma.

Proteomic maps of the cancer-associated infectious agents

The number of infectious agents associated with cancer is increasing. There is a need to develop approaches for the early detection of the infected host which might lead to tumor development. Recent advances in proteomic approaches provide that opportunity, and it is now possible to generate proteomic maps of cancer-associated infectious agents. Protein arrays, interaction maps, data archives, and biological assays are being developed to enable efficient and reliable protein identification and functional analysis. Herein, we discuss the current technologies and challenges in the field, and application of protein signatures in cancer detection and prevention.

Transcription program of murine gammaherpesvirus 68

Murine gammaherpesvirus 68 (MHV-68 [also referred to as gammaHV68]) is phylogenetically related to Kaposi's sarcoma-associated herpesvirus (KSHV [also referred to as HHV-8]) and Epstein-Barr virus (EBV). However, unlike KSHV or EBV, MHV-68 readily infects fibroblast and epithelial cell lines derived from several mammalian species, providing a system to study productive and latent infections as well as reactivation of gammaherpesviruses in vivo and in vitro. To carry out rapid genome-wide analysis of MHV-68 gene expression, we made DNA arrays containing nearly all of the known and predicted open reading frames (ORFs) of the virus. RNA obtained from an MHV-68 latently infected cell line, from cells lytically infected with MHV-68 in culture, and from the lung tissue of infected mice was used to probe the MHV-68 arrays. Using a tightly latent B-cell line (S11E), the MHV-68 latent transcription program was quantitatively described. Using BHK-21 cells and infected mice, we demonstrated that latent genes are transcribed during lytic replication and are relatively independent of de novo protein synthesis. We determined that the transcription profiles at the peak of lytic gene expression are similar in cultured fibroblast and in the lung of infected mice. Finally, the MHV-68 DNA arrays were used to examine the gene expression profile of a recombinant virus that overexpresses replication and transcription activator (RTA), C-RTA/MHV-68, during lytic replication in cell culture. The recombinant virus replicates faster then the parental strain and the DNA arrays revealed that nearly every MHV-68 ORF examined was activated by RTA overexpression. Examination of the gene expression patterns of C-RTA/MHV-68 over a time course led to the finding that the M3 promoter is RTA responsive in the absence of other viral factors.

Comparative study of regulation of RTA-responsive genes in Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8

Replication and transcription activator (RTA) (also referred to as ORF50), an immediate-early gene product of Kaposi's sarcoma-associated herpesvirus (KSHV)/(human herpesvirus 8), plays a critical role in balancing the viral life cycle between latency and lytic replication. RTA has been shown to act as a strong transcription activator for several downstream genes of KSHV. Direct binding of RTA to DNA is thought to be one of the important mechanisms for transactivation of target genes, while indirect mechanisms are also implicated in RTA transactivation of certain selected genes. This study demonstrated direct binding of the DNA-binding domain of RTA (Rdbd) to a Kaposin (Kpsn) promoter sequence, which is highly homologous to the RTA-responsive element (RRE) of the PAN promoter. We undertook a comparative study of the RREs of PAN RNA, ORF57, vIL-6, and Kpsn to understand how RTA regulates gene expression during lytic replication. Comparing RNA abundance and transcription initiation rates of these RTA target genes in virus-infected cells suggested that the transcription initiation rate of the promoters is a major determinant of viral gene expression, rather than stability of the transcripts. RTA-mediated transactivation of reporters containing each RRE showed that their promoter strengths in a transient-transfection system were comparable to their transcription rates during reactivation. Moreover, our electrophoretic mobility shift assays of each RRE demonstrated that the highly purified Rdbd protein directly bound to the RREs. Based on these results, we conclude that direct binding of RTA to these target sequences contributes to their gene expression to various extents during the lytic life cycle of KSHV.

Cell cycle regulation by Kaposi's sarcoma-associated herpesvirus K-bZIP: direct interaction with cyclin-CDK2 and induction of G1 growth arrest

In order to cope with hostile host environments, many viruses have developed strategies to perturb the cellular machinery to suit their replication needs. Some herpesvirus genes protect cells from undergoing apoptosis to prolong the lives of infected cells, while others, such as Epstein-Barr virus Zta, slow down the G(1)/S transition phase to allow ample opportunity for transcription and translation of viral genes before the onset of cellular genomic replication. In this study, we investigated whether Kaposi's sarcoma-associated herpesvirus (KSHV) K-bZIP, a homologue of the Epstein-Barr virus transcription factor BZLF1 (Zta), plays a role in cell cycle regulation. Here we show that K-bZIP physically associates with cyclin-CDK2 and downmodulates its kinase activity. The association can be detected in the natural environment of KSHV-infected cells without artificial overexpression of either component. With purified protein, it can be shown that the interaction between K-bZIP and cyclin-CDK2 is direct and that K-bZIP alone is sufficient to inhibit CDK2 activity. The interacting domain of K-bZIP has been mapped to the basic region. The result of these associations is a prolonged G(1) phase, accompanied by the induction of p21 and p27 in a naturally infected B-cell line. Thus, in addition to the previously described transcription and genome replication functions, a new role of K-bZIP in KSHV replication is identified in this report.

Kaposi's sarcoma-associated herpesvirus K-bZIP is a coregulator of K-Rta: physical association and promoter-dependent transcriptional repression

Kaposi's sarcoma-associated herpesvirus (KSHV) is a human gammaherpesvirus that has been implicated in the pathogenesis of Kaposi's sarcoma and B-cell neoplasms. The genomic organization of KSHV is similar to that of Epstein-Barr virus (EBV). EBV encodes two transcriptional factors, Rta and Zta, which functionally interact to transactivate EBV genes during replication and reactivation from latency. KSHV encodes a basic leucine zipper protein (K-bZIP), a homologue of EBV Zta, and K-Rta, the homologue of EBV Rta. EBV Rta and Zta are strong transcriptional transactivators. Although there is ample evidence that K-Rta is a potent transactivator, the role of K-bZIP as a transcriptional factor is much less clear. In this study, we report that K-bZIP modulates K-Rta function. We show that K-bZIP directly interacts with K-Rta in vivo and in vitro. This association is specific, requiring the basic domain (amino acids 122 to 189) of K-bZIP and a specific region (amino acids 499 to 550) of K-Rta, and can be detected with K-bZIP and K-Rta endogenously expressed in BCBL-1 cells treated with tetradecanoyl phorbol acetate. The functional relevance of this association was revealed by the observation that K-bZIP represses the transactivation of the ORF57 promoter by K-Rta in a dose-dependent manner. K-bZIP lacking the interaction domain fails to repress K-Rta-mediated transactivation; this finding attests to the specificity of the repression. Interestingly, this repression is not observed for the promoter of polyadenylated nuclear (PAN) RNA, another target of K-Rta; thus, repression is promoter dependent. Finally, we provide evidence that the modulation of K-Rta by K-bZIP also occurs in vivo during reactivation of the viral genome in BCBL-1 cells. When K-bZIP is overexpressed in BCBL-1 cells, the level of expression of ORF57 but not PAN RNA is repressed. These data support the model that one function of K-bZIP is to modulate the activity of the transcriptional transactivator K-Rta.

Viral diseases of the oral mucosa

A wide variety of both DNA and RNA viruses affect the oral cavity. When considered in conjunction with cutaneous features, careful examination of the oral mucosa and oropharynx aids the clinician in making a diagnosis. Examination of the oral cavity should be incorporated as a regular component of the dermatologic examination because diagnostic clues are readily available to assist in the evaluation of infectious processes.

Characterization of interactions between RTA and the promoter of polyadenylated nuclear RNA in Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8

RTA (replication and transcription activator; also referred to as ORF50, Lyta, and ART), an immediate-early gene product of Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus 8, disrupts latency and drives lytic replication. RTA activates the expression of polyadenylated nuclear (PAN) RNA (also known as T1.1 or nut-1) of KSHV. This novel noncoding PAN RNA is the most abundant lytic transcript of KSHV; therefore, studying PAN RNA expression serves as a model system for understanding how RTA transactivates target genes during lytic replication. The RTA-responsive element of the PAN promoter (pPAN RRE) was previously identified, and our data suggested direct binding of full-length RTA to the pPAN RRE. Here, we present a detailed analysis of specific interactions between RTA and the PAN promoter. We expressed and purified the DNA-binding domain of RTA (Rdbd) to near homogeneity and measured its affinity for the pPAN RRE. In electrophoretic mobility shift assays (EMSAs), the dissociation constant (K(d)) of Rdbd on the pPAN RRE was determined to be approximately 8 x 10(-9) M, suggesting a strong interaction between RTA and DNA. The specificity of RTA binding to the PAN promoter was confirmed with supershift assays. The Rdbd binding sequences on the PAN promoter were mapped within a 16-bp region of the pPAN RRE by methylation interference assays. However, the minimal DNA sequence for Rdbd binding requires an additional 7 bp on both sides of the area mapped by interference assays, suggesting that non-sequence-specific as well as sequence-specific interactions between RTA and DNA contribute to high-affinity binding. To better understand the molecular interactions between RTA and the PAN promoter, an extensive mutagenesis study on the pPAN RRE was carried out by using EMSAs and reporter assays. These analyses revealed base pairs critical for both Rdbd binding in vitro and RTA transactivation in vivo of the PAN promoter. The results from methylation interference, deletion analysis, and mutagenesis using EMSAs and reporter assays were closely correlated and support the hypothesis that RTA activates PAN RNA expression through direct binding to DNA.

Transcription activation of polyadenylated nuclear rna by rta in human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus

Human herpesvirus 8 (HHV-8) (also known as Kaposi's sarcoma-associated herpesvirus) encodes a novel noncoding polyadenylated nuclear (PAN) RNA (also known as T1.1 or nut-1) during the early phase of lytic replication. PAN RNA is the most abundant transcript of HHV-8, comprising 80% of total poly(A)-selected transcripts in HHV-8-infected cells during lytic replication. We directly measured the abundance of PAN RNA by visualizing 1.1- to 1.2- kb PAN RNA in an ethidium bromide-stained gel from poly(A)-selected RNA. We further pursued the mechanisms by which PAN RNA expression is induced to such high levels. rta, an immediate-early gene of HHV-8, is a transactivator that is sufficient and necessary to activate lytic gene expression in latently infected cells. Ectopic expression of Rta was previously shown to induce PAN RNA expression from the endogenous viral genome and activate the PAN promoter in a reporter system. Here, we have identified the Rta-responsive element (RRE) in the PAN promoter. Deletion analysis revealed that the RRE is present in a region between nucleotides -69 and -38 of the PAN promoter. A promoter construct containing the 69 nucleotides upstream of the transcription start site of the PAN promoter was activated by Rta in the absence or presence of the HHV-8 genome. Rta activated the PAN promoter up to 7,000-fold in 293T cells and 2,000-fold in B cells. Electrophoretic mobility shift assays demonstrated that Rta formed a highly stable complex with the RRE of the PAN promoter. Our study suggests that Rta can induce PAN RNA expression by direct binding of Rta to the RRE of the PAN promoter. This study has highlighted an important mechanism controlling PAN RNA expression and also provides a model system for investigating how Rta transactivates gene expression during lytic replication.

Hot-spot variations of Kaposi's sarcoma-associated herpesvirus latent nuclear antigen and application in genotyping by PCR-RFLP

Kaposi's sarcoma-associated herpesvirus (KSHV, human herpesvirus-8) is aetiologically associated with Kaposi's sarcoma and several other lymphoproliferative disorders. The latent nuclear antigen (LNA) encoded by KSHV ORF73 has important functions in virus latent infection and shows molecular polymorphism. Sequence variations were identified in the internal repeat domain (IRD) of ORF73. DNA sequencing of ORF73 from one KSHV-infected cell line, PK-1, revealed that there were 558 bp (30.2%) deletions and 66 (3.6%) point mutations located mainly in repeat region 2, the glutamine-rich region of ORF73 IRD, compared with ORF73 of BC-1 KSHV. Similar sequence variations of ORF73 were also identified in two other isolates. None of the sequence variations caused any translational frame-shift in these four KSHV isolates examined, suggesting that LNA has a conservative function in virus latent infection. The frequent sequence variations in repeat region 2 of ORF73 IRD were also identified by PCR-RFLP genotyping in 26 KSHV isolates, suggesting that this region is a 'hot-spot' for genetic variations. Each Kaposi's sarcoma lesion sample contained one virus genotype with a unique RFLP pattern, indicating that in vivo KSHV infection was established with single predominate genotypes, which was further supported by the presence of invariable genotypes in multifocal lesions from individual KS patients. Four KSHV subtypes were classified based on the RFLP patterns that represent the patterns of DNA sequence variations in the ORF73 IRD. PCR-RFLP genotyping is capable of identifying LNA genetic variations and differentiating individual KSHV isolates, and thus may be useful for KSHV molecular epidemiology studies.

Expression of human herpesvirus-8 (HHV-8) encoded pathogenic genes in Kaposi's sarcoma (KS) primary lesions

Transcription of six different HHV-8 specific mRNAs was examined in early- and late-stage KS primary lesions. Expression of the latency-associated T0.7 mRNA and of VP23 mRNA which is a specific marker of lytic/productive infection suggested that HHV-8 is secondarily recruited into the KS lesions by productively infected monocytes, macrophages. From these cells HHV-8 is transmitted to the KS spindle cells, which are latently infected. v-BCL-2, v-MCP-1 and v-IL-6 were not expressed in latently infected KS spindle cells, therefore the impact of these factors in KS pathogenesis appears to be low. By contrast, v-Cyclin D was highly expressed in almost all latently infected spindle cells and may therefore be an important factor triggering progression of late-stage KS lesions.

Human Herpesvirus 8 Infections

Human herpesvirus 8 (HHV-8) or Kaposi's sarcoma (KS)-associated herpesvirus is a recently identified virus that is associated with KS, multicentric Castleman's disease, and body cavity-based lymphomas. KS is the most common kind of cancer in AIDS patients and the initial AIDS-defining condition in over 20% of patients. HHV-8 DNA has now been detected in over 95% of KS tissue samples supporting the concept that HHV-8 has a causal role in KS. The discovery has opened new avenues for understanding the epidemiology, pathogenesis, and treatment of KS and related conditions.

The prevalence of herpes family virus DNA in the conjunctiva of patients positive and negative for human immunodeficiency virus using the polymerase chain reaction

OBJECTIVE

To help understand the pathogenesis of herpes family virus ocular infection among patients positive for HIV, the authors compared the rates of detection of herpes family virus DNA from the conjunctiva of patients who are positive and negative for human immunodeficiency virus (HIV) using the polymerase chain reaction (PCR).

DESIGN

Cross-sectional study.

PARTICIPANTS

The conjunctival scrapings of 30 patients positive for HIV and 30 patients negative for HIV were examined.

INTERVENTION

PCR was used to assay for the presence of herpes simplex virus type 1 (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) DNA (n = 240 samples).

MAIN OUTCOME MEASURE

The rate of detection of virus DNA in the two groups, controlling for age, gender, and race, was measured.

RESULTS

HSV and VZV DNA were not detected in any of the HIV-positive or HIV-negative samples. CMV DNA was detected in 20% (6 of 30) of patients positive for HIV and was undetected in control subjects negative for HIV (P = 0.01). EBV DNA was detected in 40% (12 of 30) of patients positive for HIV and in 47% (14 of 30) of control subjects negative for HIV (P = 0.58).

CONCLUSIONS

There was no difference in the frequency of detection of HSV, VZV, or EBV DNA from the conjunctiva of patients positive or negative for HIV. Only CMV DNA was detected at a significantly higher rate in the conjunctiva of patients positive for HIV compared with control subjects negative for HIV. These different rates of peripheral virus shedding may be one possible explanation for the different rates of clinical infection among the herpes family viruses among patients positive for HIV.

Kaposi's sarcoma and human herpesvirus-8

KS is a major cause of morbidity and mortality among AIDS patients and a treatment problem in the sporadic cases that are not associated with HIV. All four forms of the disease are linked to a newly described herpesvirus, HHV-8 or KSHV, via strong epidemiologic associations and biologic plausibility as a causal agent. HHV-8 is also epidemiologically associated with body cavity-based lymphomas, which are almost unique to AIDS, and Castleman's disease. Existing radiation and chemotherapeutic treatments of KS are only partially effective and cause significant adverse effects. New preventive approaches and therapies aimed at inhibiting HHV-8 may be effective. New treatments that interfere with the molecular mechanisms that drive KS may, in the future, provide the best opportunities to control the disease.

Detection of human herpesvirus-8 DNA in Kaposi's sarcomas from iatrogenically immunosuppressed patients

BACKGROUND

Kaposi's sarcoma (KS) accounts for more than 5% of malignancies in immunosuppressed organ transplant patients (OKS). A new herpesvirus (HHV-8) was identified with high prevalence in biopsy specimens of AIDS-KS, endemic KS, and classic KS and in OKS. KS has also been associated with other underlying diseases in patients treated with corticosteroids, but this subset of KS has been reported to contain HHV-8 in only a few case reports.

OBJECTIVE

In this larger study, we determined the prevalence of HHV-8 in seven patients of Jewish origin in whom KS developed during immunosuppressive therapy for different primary diseases (ISKS).

METHODS

The study included HHV-8 DNA detection by polymerase chain reaction (PCR) coupled with Southern blot and sequence analysis as well as by in situ hybridization.

RESULTS

HHV-8 sequences were detected by PCR with confirmation by Southern blot and sequence analysis in 100% of the ISKS samples. Direct sequencing revealed several previously unknown base changes within the 208 bp region from open reading frame 26 (ORF26[208]) of HHV-8 in ISKS.

CONCLUSION

Ours is the largest known study describing the presence of HHV-8 in iatrogenic KS from immunosuppressed nontransplant patients and provides data of previously unknown sequence variations within the ORF26 of HHV-8 DNA.

Expression of human herpesvirus 8-encoded cyclin D in Kaposi's sarcoma spindle cells

BACKGROUND

Human herpesvirus 8 (HHV-8) DNA sequences have been detected in Kaposi's sarcoma, in primary effusion lymphoma (an unusual high-grade non-Hodgkin's lymphoma seen primarily in patients with acquired immunodeficiency syndrome [AIDS]), and in Castleman's disease (a rare lymphoproliferative disorder); however, proof that HHV-8 is involved in the pathogenesis of these diseases remains to be established. HHV-8 contains a gene, i.e., v-cyclin D, that is a homologue of the cellular cyclin D2 gene, which encodes a protein that promotes passage through G1 phase of the cell cycle. Previous studies have identified v-cyclin D messenger RNA (mRNA) in biopsy specimens of Kaposi's sarcoma. In this study, we isolated a full-length v-cyclin D complementary DNA and characterized the pattern of v-cyclin D mRNA expression in Kaposi's sarcoma.

METHODS

Standard methods were used to construct and to screen HHV-8 genomic and complementary DNA libraries. Reverse transcription-polymerase chain reaction (RT-PCR) methods and in situ hybridization with RNA probes were used to examine v-cyclin D mRNA expression.

RESULTS

RT-PCR demonstrated the presence of v-cyclin D mRNA in biopsy specimens of AIDS-related Kaposi's sarcoma, in early-passage spindle cells from classical (i.e., not AIDS-related) Kaposi's sarcoma, and in spindle cells isolated from the peripheral blood of patients with AIDS-related Kaposi's sarcoma. In situ hybridization indicated that mRNAs for v-cyclin D and kaposin, an HHV-8 latency-associated gene, were present in approximately 1% of the spindle cells in early patch lesions and approximately 60% of the spindle cells in late nodular lesions of Kaposi's sarcoma.

CONCLUSIONS

Spindle cells of Kaposi's sarcoma, which have been regarded as the tumor cells of this cancer, contain v-cyclin D mRNA. Expression of v-cyclin D protein may be involved in the pathogenesis of Kaposi's sarcoma by promoting cell proliferation.