A role for a new herpes virus (KSHV) in different forms of Kaposi's sarcoma

PCR assay fails to detect molluscum contagiosum virus-related sequences in AIDS-related Kaposi's sarcoma

Previous PCR-based studies have demonstrated the presence of various viral DNA or RNA sequences in Kaposi's sarcoma (KS) tissues. To date, only human herpesvirus 8 (HHV-8) DNA sequences are found consistently in KS. The putative role of this agent in KS pathogenesis remains, however, to be determined; HHV-8 could infect populations endemically and could be reactivated in patients with KS. A close association between AIDS-related KS and molluscum contagiosum occurrence was found and this study was conducted primarily to search for the presence of molluscum contagiosum virus DNA sequences in KS. Frozen KS samples were examined for the presence of both HHV-8 and molluscum contagiosum virus DNA sequences by PCR. Despite a high rate of co-infection, no molluscum contagiosum virus (MCV) DNA sequence could be found in the KS samples whereas HHV-8 was uniformly detected. These results suggest that the high prevalence of MCV in AIDS patients with KS relies on a mode of transmission common for HHV-8 and molluscum contagiosum virus rather than on a multiviral etiology of KS. They may also indicate a particular susceptibility of the host to viral reactivation. If this is so, the failure to detect MCV DNA sequences in KS tissues by PCR indicates that locally produced or released cyotokines are not involved in the latter process.

Identification of kaposin (open reading frame K12) as a human herpesvirus 8 (Kaposi's sarcoma-associated herpesvirus) transforming gene

The recently identified human herpesvirus 8 (HHV-8, or Kaposi's sarcoma-associated herpesvirus) has been implicated in the etiology of both Kaposi's sarcoma (KS) and primary effusion (body cavity-based) lymphoma (PEL) (Y. Chang et al., Science 266:1865-1869, 1994; P. S. Moore et al., J. Virol. 70:549-558, 1996). An important feature of the association of HHV-8 with these malignancies is the expression of an abundant, latency-associated 0.7-kb transcript, T0. 7 (W. Zhong et al., Proc. Natl. Acad. Sci. USA 93:6641-6646, 1996). T0.7 is found in all stages in nearly all KS tumors of different epidemiologic origin, including AIDS-associated, African endemic, and classical KS (K. A. Staskus et al., J. Virol. 71:715-719, 1997), as well as in a body cavity-based lymphoma-derived cell line, BCBL-1, that is latently infected with HHV-8 (R. Renne et al., Nat. Med. 2:342-346, 1996). T0.7 encodes a unique HHV-8 open reading frame, K12, also known as kaposin. In this study, we report that the kaposin gene induced tumorigenic transformation. Constructs with kaposin expressed either from its endogenous promoter or from a heterologous promoter induced focal transformation upon transfection into Rat-3 cells. All transformed Rat-3 cell lines containing kaposin sequences produced high-grade, highly vascular, undifferentiated sarcomas upon subcutaneous injection of athymic nu/nu mice. Tumor-derived cell lines expressed kaposin mRNA, suggesting a role in the maintenance of the transformed phenotype. Furthermore, kaposin protein was detected in transformed and tumor-derived cells by immunofluorescence and localized to the cytoplasm. More importantly, expression of kaposin protein was also detected in the PEL cell lines BCBL-1 and KS-1. These findings demonstrate the oncogenic potential of kaposin and suggest its possible role in the development of KS and other HHV-8-associated malignancies.

High human herpesvirus 8 seroprevalence in the homosexual population in Switzerland

The seroprevalence of human herpesvirus 8 (HHV-8) in the Swiss population was investigated. By enzyme-linked immunosorbent assay, sera reactive to the recombinant HHV-8 antigen orf 65.2 were found in 24% of human immunodeficiency virus (HIV)-positive patients without and in 92% of HIV-positive patients with Kaposi's sarcoma. Surprisingly, 20% of homosexual HIV-negative men, versus only 7% of heterosexual HIV-negative individuals and 5% of blood donors, had antibodies to HHV-8.

Human immunodeficiency virus (HIV) in America, 1981 to 1997: epidemiologic and therapeutic considerations

In the last 16 years, acquired immunodeficiency syndrome (AIDS) has evolved from a mysterious syndrome apparently afflicting only gay men, into a viral illness affecting every segment of society. Until the advent of combination antiretroviral therapy, HIV appeared to be universally fatal. New therapies and technologies have been developed offering normal or near-normal life spans for some people living with HIV. Coincident with the development of life-prolonging therapies has been the realization that competent HIV care requires the integration of medical care, social services, and psychological support services to promote therapeutic adherence and maximize quality of life.

Kaposi's sarcoma: a result of the interplay among inflammatory cytokines, angiogenic factors and viral agents

Kaposi's sarcoma (KS) is an angioproliferative disease occurring in 4 clinic-epidemiologic forms. Although the AIDS-associated KS (AIDS-KS) is the most aggressive, all forms of KS share the same immunological and histopathological features suggesting common etiological and pathogenic factors. Recent data indicate that at least in early stage KS is not a real sarcoma but an angiohyperplastic-inflammatory lesion mediated by inflammatory cytokines and angiogenic factors, that is triggered or amplified by infection with human herpesvirus-8. In addition, the human immunodeficiency virus type-1 Tat protein appears to be responsible for the higher grade of aggressiveness of AIDS-KS as compared to the other forms of KS. However, given time, reactive KS may progress to a sarcoma as suggested by evidence of monoclonality in late-nodular lesions.

Diagnosis of pulmonary Kaposi's sarcoma by detection of human herpes virus 8 in bronchoalveolar lavage

Human herpes virus 8 (HHV8) DNA has recently been detected in sarcoma tissue of patients with Kaposi's sarcoma. HHV8 DNA could also be found in bronchoalveolar lavage (BAL) fluid of patients with tracheobronchial Kaposi's sarcoma. To determine the specificity, sensitivity and predictive values of HHV8 DNA detection in the BAL for the diagnosis of pulmonary Kaposi's sarcoma, 100 consecutive BAL were prospectively analyzed for the presence of HHV8 DNA using a nested PCR assay. In addition, 19 BAL samples of 14 AIDS patients with cutaneous or visceral Kaposi's sarcoma were retrospectively investigated. The prospective group consisted of 79 BAL performed in immunocompromised and of 21 BAL in nonimmunocompromised patients. Four patients of the prospectively analyzed group undergoing six BAL showed tracheobronchial Kaposi's sarcoma at five bronchoscopies. All of the five BAL samples performed in these patients with endoscopically visible Kaposi's sarcoma were positive for HHV8 DNA. Following chemotherapy and antiretroviral treatment tracheobronchial Kaposi's sarcoma was no longer detectable at a subsequent bronchoscopy and HHV8 DNA in BAL became negative in one patient. One BAL sample of a HIV-positive patient with no evidence of Kaposi's sarcoma was HHV8 DNA-positive. The sensitivity, specificity, positive and negative predictive values of HHV8 detection for the diagnosis of tracheobronchial Kaposi's sarcoma were 100%, 98.9%, 83.3%, and 100%, respectively. Twelve of 19 BAL samples of the retrospective group were HHV8 DNA-positive. In this group, 10 patients undergoing a total of 14 BAL suffered from pulmonary Kaposi's sarcoma. HHV8 DNA was documented in 10 of these 14 BAL samples. In three BAL of this group HHV8 DNA was positive, but pulmonary Kaposi's sarcoma was diagnosed at a later stage. In conclusion, the detection of HHV8 DNA in BAL is restricted to patients with Kaposi's sarcoma and is highly sensitive and specific for pulmonary involvement of Kaposi's sarcoma.

The evaluation of human herpesvirus 8 (Kaposi's sarcoma-associated herpesvirus) in cutaneous lesions of Kaposi's sarcoma: a study of formalin-fixed paraffin-embedded tissue

The etiologic role of human herpesvirus 8 (HHV8) in Kaposi's sarcoma (KS) remains controversial. This polymerase chain reaction (PCR)-based study was undertaken to evaluate the relationship of HHV8 in KS from our geographical region and to determine its utility in formalin-fixed, paraffin-embedded biopsy specimens. Forty-two biopsy specimens were studied, including nine AIDS-associated cases and four from classic KS. Of the 39 patients included, 21 were HIV+ and 18 had no clinical evidence of HIV infection. Only a single (internal) primer pair was used in the PCR. All PCR products were tested with an HHV8 specific probe by dot blot analysis. Seven of the nine AIDS KS specimens were positive for HHV8 on electrophoresis, and all nine were positive after dot blot. Two of four specimens from classic KS were positive for HHV8 on the gel electrophoresis, and three of four were positive on blot confirmation. Non-KS specimens from 15 HIV+ patients yielded one positive venous hemangioma from a man with HHV8-positive KS at another site. Specimens from HIV-unrelated controls with a variety of diagnoses were negative by PCR with blot. The predominant negativity for HHV8 in non-KS lesions suggests that HHV8 is not widespread in our patients. These results demonstrate yet another series linking KS with HHV8 and show that paraffin-embedded biopsy specimens are satisfactory for this technique.

Human herpesvirus 8 (HHV-8) in the pathogenesis of Kaposi's sarcoma and other diseases

The discovery of Kaposi's Sarcoma-associated herpesvirus/human herpesvirus-8 (KSHV/ HHV-8) and subsequent studies of this virus have provided a body of evidence that support the concept that this is an etiologic agent for Kaposi's sarcoma (KS). Several studies have indicated that this virus may also be a causal agent for primary effusion lymphoma (PEL) and Castleman's disease as well. First generation serologic assays for HHV-8 have now been developed. The preponderance of data suggest that the incidence of HHV-8 infection is highest in populations at risk for KS: male homosexuals, immunosuppressed patients, and those who live in endemic regions. HHV-8 encodes for functional homologs of human proteins that may play a role in the development of disease. As we learn more about the steps by which this virus can lead to KS and/or other diseases, rational therapies and preventative strategies may be possible.

Human herpes virus 8 (Kaposi's sarcoma herpesvirus)

Human herpes virus 8 (HHV-8) is a recently discovered herpesvirus related to Herpesvirus saimiri and Epstein-Barr virus (EBV). It has been assigned to the Rhadinovirus genus (gamma-2 herpesvirus) on the basis of its genomic sequence and structure. HHV-8 is the first member of this genus known to infect humans and it is now evident that it is the likely cause of Kaposi's sarcoma (KS). The virus is present in endothelial and spindle cells of KS, and in HIV disease the presence of HHV-8 in peripheral blood, and/or serum IgG antibodies to HHV-8, predicts the development of AIDS-related KS. HHV-8 can also infect CD19 + B cells and is of aetiological significance in the development of body cavity B cell lymphomas of AIDS. Of note, the translation products of viral open reading frames (ORFs) reveal HHV-8 to be a molecular pirate, capable of producing homologues of several human gene products that may result in alterations in cell cycle arrest, inhibit apoptosis and cell-mediated immune responses, and thus provide the potential for tumour production.

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.

HHV8 and female Kaposi's sarcoma

Kaposi's sarcoma (KS) is an enigmatic tumour of uncertain histogenesis. Epidemiological data have long suggested that KS may be caused by an infectious agent, possibly sexually transmitted. Following the documentation of human herpesvirus 8 (HHV8) and its strong association with all forms of KS, it now appears that the putative agent has at last been identified. As KS is rare in females, a unique group was screened for the presence of HHV8 using both conventional solution-phase polymerase chain reaction (PCR) and the newly described technique of TaqMan PCR. The presence of HHV8 was demonstrated in 10/12 of these female patients. This further supports the direct role of HHV8, in conjunction with cytokines and other factors, in the pathogenesis of KS.

Identification of the gene encoding the major latency-associated nuclear antigen of the Kaposi's sarcoma-associated herpesvirus

Over 85% of patients with Kaposi's sarcoma (KS) are seropositive for antibodies to the latency-associated nuclear antigen (LANA) expressed in B cell lines infected with Kaposi's sarcoma-associated herpesvirus (KSHV). The presence of antibodies to LANA strongly correlates with the risk of developing the disease. However, the identity of the protein(s) comprising LANA and the corresponding gene(s) has remained unclear. To identify potential latent gene candidates for LANA, we probed total RNA extracted from BCBL-1 cells (a B cell line latently infected with KSHV) using lambda clones that span the KSHV genome. One region encoding latent transcripts spanned KSHV open reading frames (orfs) 71 (K13), 72 (v-cyclin), and 73. Among these, however, only orf 73, when expressed in heterologous mammalian cell systems, reacted with KSHV antibody-positive human sera, resulting in a punctate nuclear staining pattern reminiscent of LANA in BCBL-1 cells. Furthermore, extracts from cells expressing the orf 73 protein product specifically blocked the binding of KS patient antibodies to LANA. Finally, seroreactivity with recombinant orf 73 protein exactly paralleled reactivity with classical LANA as expressed in BCBL-1 cells, both in KS patients and in other groups. Together, these data support the identification of KSHV orf 73 as the gene encoding the dominant immunogenic component of LANA.

Aetiology of Kaposi's sarcoma: current understanding and implications for therapy

Kaposi's sarcoma is an angiogenic neoplasm composed of endothelial and spindle cells. The enormous increase in Kaposi's sarcoma with HIV infection, and recent discovery that a new human herpesvirus (Kaposi's sarcoma-associated herpesvirus, also called human herpesvirus 8) is present in this tumor, has activated intense interest in the aetiology, epidemiology and pathogenesis of this disease. Today, Kaposi's sarcoma is one of the most frequent neoplasms in men under 50 years old in the USA, and in some African countries it is the most common tumour overall.

Monocytes in Kaposi's sarcoma lesions are productively infected by human herpesvirus 8

PCR analysis and serological studies demonstrated a close association between Kaposi's sarcoma (KS)-associated herpesvirus, or human herpesvirus 8 (HHV-8), and the development of Kaposi's sarcoma (KS). The majority of the KS cells were shown to be latently infected by the virus. In this study we investigated which type of cell is productively infected in KS lesions. In situ hybridization was performed with strand-specific RNA probes complementary to the sequences coding for the minor capsid protein (VP23) of HHV-8. The VP23 gene is specifically expressed during the lytic or replicative period of the virus life cycle, and therefore it is a useful marker to detect productively infected cells. By in situ hybridization of KS lesions, a strong hybridization signal was detected only in a small subset of the KS cells of the lesions. Simultaneous application of immunohistochemical staining and in situ hybridization identified the virus-replicating cells to be of monocytic origin. Productively infected monocytes may be an important reservoir for transmission of the virus and for the increase and maintenance of the high load of HHV-8 generally observed in nodular KS lesions during late stages of infection.

The structure and coding organization of the genomic termini of Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) is a novel human herpesvirus closely linked to two AIDS-related neoplasms. We have prepared DNA from KSHV virions produced in cell culture and have examined the structure of the viral genomic termini. As in the related simian herpesvirus H. saimiri (HVS), the central unique region of KSHV DNA is bounded by tandemly repeated units of noncoding, GC-rich DNA. The KSHV repeats are 803 bp in length and are 85% G+C. Each molecule harbors 35-45 such repeats, but the repeats are not arrayed uniformly and symmetrically at each end. Rather, different molecules appear to contain different numbers of repeats at each end, with the sum total of repeated DNA per genome being relatively fixed, since the full genome is uniformly 165-170 kb. Thus, molecules with many repeats at one end will have fewer at the other. Because the unique viral genes bordering the left-hand repeats of the HVS genome play key roles in oncogenesis, we also examined the coding organization of the corresponding region of KSHV. No homologs of the HVS transforming genes were identified in this region of KSHV; rather, this region bears a novel gene encoding a putative transmembrane protein that appears to be upregulated during the early phase of lytic viral replication.

The protease and the assembly protein of Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8)

A genomic clone encoding the protease (Pr) and the assembly protein (AP) of Kaposi's sarcoma-associated herpesvirus (KSHV) (also called human herpesvirus 8) has been isolated and sequenced. As with other herpesviruses, the Pr and AP coding regions are present within a single long open reading frame. The mature KSHV Pr and AP polypeptides are predicted to contain 230 and 283 residues, respectively. The amino acid sequence of KSHV Pr has 56% identity with that of herpesvirus salmiri, the most similar virus by phylogenetic comparison. Pr is expressed in infected human cells as a late viral gene product, as suggested by RNA analysis of KSHV-infected BCBL-1 cells. Expression of the Pr domain in Escherichia coli yields an enzymatically active species, as determined by cleavage of synthetic peptide substrates, while an active-site mutant of this same domain yields minimal proteolytic activity. Sequence comparisons with human cytomegalovirus (HCMV) Pr permitted the identification of the catalytic residues, Ser114, His46, and His134, based on the known structure of the HCMV enzyme. The amino acid sequences of the release site of KSHV Pr (Tyr-Leu-Lys-Ala*Ser-Leu-Ile-Pro) and the maturation site (Arg-Leu-Glu-Ala*Ser-Ser-Arg-Ser) show that the extended substrate binding pocket differs from that of other members of the family. The conservation of amino acids known to be involved in the dimer interface region of HCMV Pr suggests that KSHV Pr assembles in a similar fashion. These features of the viral protease provide opportunities to develop specific inhibitors of its enzymatic activity.

The 222- to 234-kilodalton latent nuclear protein (LNA) of Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) is encoded by orf73 and is a component of the latency-associated nuclear antigen

Kaposi's sarcoma (KS)-associated herpesvirus or human herpesvirus 8 (KSHV/HHV8) is the likely cause of KS and primary effusion lymphomas or body cavity-based lymphomas (BCBLs). A latency-associated nuclear immunofluorescence antigen (LANA) (D. H. Kedes, E. Operskalski, M. Busch, R. Kohn, J. Flood, and D. Ganem, Nat. Med. 2:918-924, 1996; S. J. Gao, L. Kingsley, M. Li, W. Zheng, C. Parravicini, J. Ziegler, R. Newton, C. R. Rinaldo, A. Saah, J. Phair, R. Detels, Y. Chang, and P. S. Moore, Nat. Med. 2:925-928, 1996) and a 222- to 234-kDa nuclear protein (LNA) (S. J. Gao, L. Kingsley, D. R. Hoover, T. J. Spira, C. R. Rinaldo, A. Saah, J. Phair, R. Detels, P. Parry, Y. Chang, and P. S. Moore, N. Engl. J. Med. 335:233-241, 1996) have previously been described in BCBL cell lines by immunofluorescence and Western blotting techniques, respectively. To identify the viral gene(s) encoding this antigen(s) we screened a cDNA library from HBL-6 cells, a B-cell lymphoma cell line persistently infected with KSHV/HHV8, with KS patient sera. One set of positive clones contained the 3' end of orf73, as well as the complete orf72 and orfK13, and another set contained the 5' end of orf73. Comparison of cDNA sequences with the KSHV/HHV8 genomic sequence revealed a splice event, occurring upstream of orf73. Immunoaffinity purified antibodies to a recombinant carboxy-terminal fragment of the orf73-encoded protein showed the characteristic speckled nuclear immunofluorescence pattern of LANA and reacted with the 222- to 234-kDa LNA on Western blots. Expression of full-length orf73 in bacteria and COS7 cells reproduced the LNA banding pattern. Immunohistochemistry on cases of nodular KS revealed that orf73/LNA is expressed in the nucleus of KS spindle cells. These findings demonstrate that orf73 encodes the 222- to 234-kDa LNA, is a component of LANA, and is expressed in KS tumor cells.

Expression of HHV-8 latency-associated T0.7 RNA in spindle cells and endothelial cells of AIDS-associated, classical and African Kaposi's sarcoma

Analysis by polymerase chain reaction (PCR) and serological studies have demonstrated a close association between the novel human herpes virus, Kaposi's sarcoma-associated herpes virus (KSHV) or human herpes virus-8 (HHV-8) and the development of Kaposi's sarcoma (KS). To clarify the role of HHV-8 in KS pathogenesis, we investigated at the cellular level by in situ hybridization the expression of a recently described 0.7-kb HHV-8-encoded mRNA (T0.7 mRNA) in KS tissues of different epidemiological origin (AIDS-KS, African endemic KS and classical KS). The T0.7 mRNA likely encodes a small membrane protein, supposedly expressed in latently HHV-8-infected cells. Indeed, we detected T0.7 mRNA in virtually all cells of the cell line BCBL-1 established from a body cavity-based lymphoma (BCBL) and latently infected with HHV-8. In all KS biopsies examined, independent of their epidemiological type, the late-stage (nodular) KS tissues showed a high level of T0.7 mRNA expression in typical KS spindle cells but also in endothelial cells lining blood vessels, indicating latent HHV-8 infection of these cells. The presence of T0.7-expressing cells was restricted to KS tumor tissue and therefore appears to indicate an important role of latent HHV-8 infection in KS pathogenesis.

Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8: a new virus in human pathology

The discovery of a new human herpesvirus in Kaposi's sarcoma (KS) tissue of patients with AIDS has opened up new vistas in virology and oncology. This herpesvirus was first descriptively named KS-associated herpesvirus (KSHV), but was recently renamed human herpesvirus 8 (HHV8). KSHV/HHV8 DNA has been found in all forms of KS, suggesting that it might be involved in the pathogenesis of KS. In addition, KSHV/HHV8 can be detected in both malignant and benign lymphoproliferative disease. KSHV/HHV8 was also found in patients with angiosarcoma of the face and angiolymphoid hyperplasia with eosinophilia. Although only a limited portion of the virus has been sequenced, KSHV/HHV8 is equipped with genes that could confer oncogenic potential. The virus can now be cultured, providing the possibility for studies of viral replication and the mode of transmission. The recently developed serologic assays for antiviral antibodies suggest that infection with KSHV/HHV8 is not ubiquitous because KSHV/HHV8 seropositivity is limited to a small proportion of the population.

Experimental investigation of herpes simplex virus latency

The clinical manifestations of herpes simplex virus infection generally involve a mild and localized primary infection followed by asymptomatic (latent) infection interrupted sporadically by periods of recrudescence (reactivation) where virus replication and associated cytopathologic findings are manifest at the site of initial infection. During the latent phase of infection, viral genomes, but not infectious virus itself, can be detected in sensory and autonomic neurons. The process of latent infection and reactivation has been subject to continuing investigation in animal models and, more recently, in cultured cells. The initiation and maintenance of latent infection in neurons are apparently passive phenomena in that no virus gene products need be expressed or are required. Despite this, a single latency-associated transcript (LAT) encoded by DNA encompassing about 6% of the viral genome is expressed during latent infection in a minority of neurons containing viral DNA. This transcript is spliced, and the intron derived from this splicing is stably maintained in the nucleus of neurons expressing it. Reactivation, which can be induced by stress and assayed in several animal models, is facilitated by the expression of LAT. Although the mechanism of action of LAT-mediated facilitation of reactivation is not clear, all available evidence argues against its involving the expression of a protein. Rather, the most consistent models of action involve LAT expression playing a cis-acting role in a very early stage of the reactivation process.

Kaposi's sarcoma-associated herpesvirus infection of bone marrow dendritic cells from multiple myeloma patients

Kaposi's sarcoma-associated herpesvirus (KSHV) was found in the bone marrow dendritic cells of multiple myeloma patients but not in malignant plasma cells or bone marrow dendritic cells from normal individuals or patients with other malignancies. In addition the virus was detected in the bone marrow dendritic cells from two out of eight patients with monoclonal gammopathy of undetermined significance (MGUS), a precursor to myeloma. Viral interleukin-6, the human homolog of which is a growth factor for myeloma, was found to be transcribed in the myeloma bone marrow dendritic cells. KSHV may be required for transformation from MGUS to myeloma and perpetuate the growth of malignant plasma cells.

Etiology of AIDS-related Kaposi's sarcoma and lymphoma

Kaposi's sarcoma (KS) and non-Hodgkin's lymphomas (NHL) are common consequences of HIV infection. These tumours appear to be precipitated by herpesviruses. Epstein-Barr virus (EBV) is implicated as a cause of up to 50% of systemic NHLs and up to 100% of central nervous system lymphomas in patients with AIDS. KS may be a consequence of the newly identified gamma-herpesvirus KSHV (KS-associated herpesvirus or HHV-8). This herpesvirus is found in all KS biopsies from different epidemiologic forms of this disease. KSHV is also implicated in the pathogenesis of a rare form of B cell lymphoma called body-cavity based lymphoma or primary effusion lymphoma (PEL).

Identification of two homologs of the Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) in retroperitoneal fibromatosis of different macaque species

Simian retroperitoneal fibromatosis (RF) is a vascular fibroproliferative neoplasm which has many morphological and histological similarities to human Kaposi's sarcoma (KS). Like epidemic KS in AIDS patients, RF is highly associated with an immunodeficiency syndrome (simian acquired immunodeficiency syndrome [SAIDS]) caused by a retrovirus infection. Recently, a new gammaherpesvirus, called Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV8), has been identified in KS tumors, suggesting that KS has a viral etiology. Our previous experimental transmission studies and epidemiological data suggest that RF also has an infectious etiology. In order to determine whether a similar virus is also associated with RF, we have assayed for the presence of an unknown herpesvirus using degenerate PCR primers targeting the highly conserved DNA polymerase genes of the herpesvirus family. Here we provide DNA sequence evidence for two new herpesviruses closely related to KSHV from RF tissues of two macaque species, Macaca nemestrina and Macaca mulatta. Our data suggest that KSHV and the putative macaque herpesviruses define a new group within the subfamily Gammaherpesvirinae whose members are implicated in the pathogenesis of KS and KS-like neoplasms in different primate species.

HHV8 and Kaposi's sarcoma: a time cohort study

AIMS

The recent finding that human herpes virus 8 (HHV8) is found in the majority of Kaposi's sarcoma (KS) cases supports the epidemiological observation that the tumour may be caused by an infectious agent. This study aimed to address when and how HHV8 evolved.

METHODS

A cohort of African endemic KS (49 samples from 45 patients) and European KS (18 samples from 13 patients), spanning 27 years, was assessed for the presence of HHV8 by both standard solution phase polymerase chain reaction (PCR) and the newly described technique of TaqMan PCR.

RESULTS

HHV8 was present in approximately 49% (24 of 49 tissue samples) of the African cases and in more than 90% (16 of 18 tissue samples) of the European cohort, in keeping with recent seroepidemiological data.

CONCLUSIONS

HHV8 is strongly linked to the development of KS; however, in some patients, other factors may operate. The utility and flexibility of TaqMan PCR in detecting low copy viral target in human tissues was demonstrated.

Kaposi's sarcoma-associated human herpesvirus-8 encodes homologues of macrophage inflammatory protein-1 and interleukin-6

Human herpesvirus-8 (HHV-8) has been detected in Kaposi's sarcoma (KS) lesions of all types (AIDS-related, classical and endemic), in body-cavity-based B-cell lymphomas (BCBLs) and in lesions of multicentric Castleman's disease (MCD). We have identified a major gamma-herpesvirus-divergent locus (DL-B) in HHV-8 DNA encoding several HHV-8 unique open reading frames (ORFs), including a homologue of interleukin-6 (IL-6) and two homologues of macrophage inflammatory protein MIP-1. We show that the HHV-8-encoded IL-6 homologue (vIL-6) shares functional properties with endogenous IL-6 proteins and that both vIL-6 and vMIP-1 transcripts are present at high levels following butyrate induction of an HHV-8' BCBL cell line. Low amounts of constitutive vIL-6, but not vMIP-1, mRNA were also detected. The presence of a functional IL-6 homologue encoded by HHV-8 may provide a mechanistic model for the hypothesized role of HHV-8 in KS, MCD and BCBL that involves the mitogenic effects of vIL-6 on surrounding cells. MIP-1 proteins may enhance these effects through the chemotactic recruitment of endogenous cytokine-producing cells into affected tissues and could potentially influence HIV disease progression in coinfected individuals through interactions with the HIV co-receptor CCR-5.

Acquired immunodeficiency syndrome-associated Kaposi's sarcoma. Biology and management

Kaposi's Sarcoma (KS), the most common AIDS-associated malignancy, occurs with increased frequency in all HIV transmission groups, but at a particularly high rate in homosexual men. Recent studies suggest that KS pathogenesis involves exposure to an infectious agent, altered expression and response to cytokines, and modulation of growth by HIV gene products. KS varies in its clinical presentation from a relatively indolent process to a widely disseminated, aggressive disease. A variety of local and systemic treatments provide effective, but usually temporary, disease palliation. Insights into KS pathogenesis suggest a number of targeted therapeutic approaches that may eventually lead to improved disease management and disease cure.

Kaposi's sarcoma-associated herpesvirus encodes a functional bcl-2 homologue

Kaposi's sarcoma-associated herpesvirus (KSHV) is a newly discovered herpesvirus etiologically associated with Kaposi's sarcoma (KS) and two lymphoproliferative disorders. We describe a KSHV vbcl-2 gene with homology to the proto-oncogene bcl-2. It is expressed in KS lesions and in cell lines derived from primary effusion lymphomas. Using yeast and human cells we demonstrate the ability of KSHV vBcl-2 protein to suppress Bax toxicity. We show that KSHV vBcl-2 heterodimerizes with human Bcl-2 in a yeast two-hybrid system. These results suggest that KSHV vBcl-2 plays an anti-apoptotic role in virus infected cells.

Characterization of ribonucleoprotein complexes containing an abundant polyadenylated nuclear RNA encoded by Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8)

Infection with Kaposi's sarcoma-associated herpesvirus (KSHV) (also called human herpesvirus 8) is strongly linked to all forms of Kaposi's sarcoma. We have previously identified two polyadenylated KSHV transcripts that are actively transcribed in Kaposi's sarcoma (KS) tumors and in KSHV-infected B-lymphoma cells. One of these RNAs (termed T1.1 or nut-1 RNA) is a 1.1-kb transcript present in a subpopulation of KS tumor cells. This RNA is localized to the nucleus of infected cells and has no open reading frames longer than 62 codons, suggesting that it may not function as an mRNA in vivo. Here we demonstrate that nut-1 RNA is a lytic-cycle gene product that is found in high-molecular-weight ribonucleoprotein complexes in infected cell nuclei. The transcript lacks the trimethylguanosine (TMG) cap found in many U-like small nuclear RNAs, but a subpopulation of nut-1 RNAs can associate with Sm protein-containing small nuclear ribonucleoproteins, as judged by immunoprecipitation analyses using monoclonal anti-Sm and anti-TMG antibodies. This interaction does not require other viral gene products, and deletion of the sole candidate Sm binding site on nut-1 RNA does not ablate this association. This finding suggests an indirect interaction with Sm-containing structures, and models for such associations are presented.

Kaposi's sarcoma-associated herpesvirus-like DNA sequences (KSHV/HHV-8) in oral AIDS-Kaposi's sarcoma: a PCR and clinicopathologic study

Recently, a new human herpesvirus (KSHV/HHV-8) has been identified in classic, transplant, endemic, and AIDS Kaposi's sarcoma that may be involved in the pathogenesis of Kaposi's sarcoma. The purpose of this study was to evaluate oral AIDS-Kaposi's sarcoma for detection of KSHV/HHV-8 DNA. DNA extracted from 54 oral AIDS-Kaposi's sarcoma lesions (47 initial, 7 postvinblastine treated), 5 non-Kaposi's sarcoma HIV-positive lesions, and 3 non-Kaposi's sarcoma HIV-negative lesions was evaluated by polymerase chain reaction (KS330(233bp)amplicon) for KSHV/HHV-8. The AIDS-Kaposi's sarcoma study population consisted of 52 patients (51:1, men:woman; 92% men having sex with men, 8% heterosexual; mean age, 38 years; mean, CD4 59/mm3) Opportunistic infections occurred in 88% (candidiasis, 65%; Pneumocystis carinii pneumonia, 31%; nonoral Kaposi's sarcoma, 25%; mycobacterium avium-intracellulare (MAI), 16%; cytomegalovirus, 14%; herpes simplex virus, 14%). Sexually transmitted diseases occurred in 73% (gonorrhea, 37%; syphilis, 23%; condyloma, 22%; HSV, 16%). Most frequent lesion sites were palate (74%) and gingiva (17%). Most common lesion types were purple nodular (48%) and macular (42%). Histopathologic subtypes were nodular (71%), plaque (27%), and patch (2%). Polymerase chain reaction analysis detected KSHV/HHV-8 DNA in 53 of 54 AIDS-Kaposi's sarcoma lesions (47 of 47 initial, 6 of 7 postvinblastine treatment). KSHV/HHV-8 DNA was not detected in non-Kaposi's sarcoma lesions in HIV-positive or HIV-negative persons. KSHV/HHV-8 DNA sequence is present in a high proportion of oral AIDS-Kaposi's sarcoma lesions. Whether KSHV/HHV-8 is an etiologic agent or a cofactor in the development of this vascular neoplasm is uncertain and remains to be proven. Polymerase chain reaction analysis for KSHV/HHV-8 DNA sequence detection may be helpful in identifying Kaposi's sarcoma in early vascular proliferations, when the characteristic histopathologic features are not present.

Kaposi's sarcoma associated herpes virus (KSHV/HHV 8): epidemiology, molecular biology and tissue distribution

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Selective switch between latency and lytic replication of Kaposi's sarcoma herpesvirus and Epstein-Barr virus in dually infected body cavity lymphoma cells

The BC-1 cell line, derived from a body cavity-based, B-cell lymphoma, is dually infected with Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV). In these studies, the relationships between these two gammaherpesviruses and BC-1 cells were characterized and compared. Single-cell cloning experiments suggested that all BC-1 cells contain both genomes. In more than 98% of cells, both viruses were latent. The two viruses could be differentially induced into their lytic cycles by chemicals. EBV was activated into DNA replication and late-gene expression by the phorbol ester tetradecanoyl phorbol acetate (TPA). KSHV was induced into DNA replication and late-gene expression by n-butyrate. Amplification of both EBV and KSHV DNAs was inhibited by phosphonoacetic acid. Induction of the KSHV lytic cycle by n-butyrate was accompanied by the disappearance of host-cell beta-actin mRNA. Induction of EBV by TPA was not accompanied by such an effect on host-cell gene expression. Induction of the KSHV lytic cycle by n-butyrate was associated with the expression of several novel polypeptides. Recognition of one of these, p40, served as the basis of development of an assay for antibodies to KSHV in the sera of infected patients. BC-1 cells released infectious EBV; however, there was no evidence for the release of encapsidated KSHV genomes by BC-1 cells, even though n-butyrate-treated cells contained numerous intranuclear nucleocapsids. The differential inducibility of these two herpesviruses in the same cell line points to the importance of viral factors in the switch from latency to lytic cycle.

Kaposi's sarcoma-associated herpesvirus gene expression in endothelial (spindle) tumor cells

The recent discovery of DNA sequences of a new human herpesvirus in Kaposi's sarcoma (KS) has fueled speculation that this virus might cause KS. The mere presence, however, of a virus in a complex multicellular tumor like KS could just as well be construed as evidence of a passenger agent. We sought stronger evidence linking the KS-associated herpesvirus (KSHV) to tumor formation by using in situ hybridization to investigate the specificity, constancy, and timing of KSHV gene expression in KS tumor cells. Here we document expression of a 700-nucleotide viral RNA in every KS tumor examined, from the earliest histologically recognizable stage to advanced tumors in which the vast majority of identifiable spindle tumor cells contain this transcript. Two other KSHV RNAs were also detected in a smaller fraction of the tumor cells in all but the earliest lesion. These viral RNAs were expressed to relatively low levels in this subset; because one of these RNAs encodes a major viral capsid protein, these cells may be producing KSHV. We did not find these KSHV genes expressed in a variety of other tumors and proliferative processes, but we did detect viral gene expression in prostatic tissue, supporting a possible mechanism for sexual transmission of KSHV. The close relationship between KS and KSHV gene expression is consistent with the hypothesis that KSHV is directly involved in the etiology and pathogenesis of KS.

Nucleotide sequence of the Kaposi sarcoma-associated herpesvirus (HHV8)

The genome of the Kaposi sarcoma-associated herpesvirus (KSHV or HHV8) was mapped with cosmid and phage genomic libraries from the BC-1 cell line. Its nucleotide sequence was determined except for a 3-kb region at the right end of the genome that was refractory to cloning. The BC-1 KSHV genome consists of a 140.5-kb-long unique coding region flanked by multiple G + C-rich 801-bp terminal repeat sequences. A genomic duplication that apparently arose in the parental tumor is present in this cell culture-derived strain. At least 81 ORFs, including 66 with homology to herpesvirus saimiri ORFs, and 5 internal repeat regions are present in the long unique region. The virus encodes homologs to complement-binding proteins, three cytokines (two macrophage inflammatory proteins and interleukin 6), dihydrofolate reductase, bcl-2, interferon regulatory factors, interleukin 8 receptor, neural cell adhesion molecule-like adhesin, and a D-type cyclin, as well as viral structural and metabolic proteins. Terminal repeat analysis of virus DNA from a KS lesion suggests a monoclonal expansion of KSHV in the KS tumor.

Molecular mimicry of human cytokine and cytokine response pathway genes by KSHV

Four virus proteins similar to two human macrophage inflammatory protein (MIP) chemokines, interleukin-6 (IL-6), and interferon regulatory factor (IRF) are encoded by the Kaposi's sarcoma-associated herpesvirus (KSHV) genome. vIL-6 was functional in B9 proliferation assays and primarily expressed in KSHV-infected hematopoietic cells rather than KS lesions. HIV-1 transmission studies showed that vMIP-I is similar to human MIP chemokines in its ability to inhibit replication of HIV-1 strains dependent on the CCR5 co-receptor. These viral genes may form part of the response to host defenses contributing to virus-induced neoplasia and may have relevance to KSHV and HIV-I interactions.

The size and conformation of Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) DNA in infected cells and virions

The genome of a novel human herpesvirus has been detected in specimens of Kaposi's sarcoma (KS) and in several AIDS-related lymphoproliferative disorders. Here we examine the size and genomic conformation of the DNA of this virus (known as KS-associated herpesvirus or human herpesvirus 8) in latently and lytically infected cells and in virions. Pulsed-field gel electrophoresis of viral DNA shows that the viral genome is similar in size to those of other gammaherpesviruses (160 to 170 kb). As with Epstein-Barr virus, KS-associated herpesvirus DNA is stably maintained in latently infected B cells as episomal monomer circles and induction from latency is associated with the selective accumulation of linear genomic forms.

Kaposi's sarcoma-associated herpesvirus contains G protein-coupled receptor and cyclin D homologs which are expressed in Kaposi's sarcoma and malignant lymphoma

A new human herpesvirus was recently identified in all forms of Kaposi's sarcoma (Kaposi's sarcoma-associated herpesvirus [KSHV] or human herpesvirus 8), as well as in primary effusion (body cavity-based) lymphomas (PELs). A 12.3-kb-long KSHV clone was obtained from a PEL genomic library. Sequencing of this clone revealed extensive homology and colinearity with the right end of the herpesvirus saimiri (HVS) genome and more limited homology to the left end of the Epstein-Barr virus genome. Four open reading frames (ORFs) were sequenced and characterized; these are homologous to the following viral and/or cellular genes: (i) Epstein-Barr virus membrane antigen p140 and HVS p160, (ii) HVS and cellular type D cyclins, (iii) HVS and cellular G protein-coupled receptors, and (iv) HVS. Since there is considerable evidence that cyclin D1 and some G protein-coupled receptors contribute to the development of specific cancers, the presence of KSHV homologs of these genes provides support for a role for KSHV in malignant transformation. All ORFs identified are transcribed in PELs and Kaposi's sarcoma tissues, further suggesting an active role for KSHV in these diseases.

Prevalence of Kaposi's sarcoma associated herpesvirus infection measured by antibodies to recombinant capsid protein and latent immunofluorescence antigen

BACKGROUND

Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8, may be the infectious cause of KS. Its prevalence in the general population, on the basis of detection of the virus genome, is controversial. To investigate the seroprevalence, we measured antibodies to a recombinant capsid-related (lytic cycle) KSHV antigen and a latent antigen complex.

METHODS

We selected potentially immunoreactive capsid-related proteins of KSHV by expressing them as recombinant proteins and testing them in western blot assays. We used a truncated recombinant protein encoded by KSHV open reading frame 65 (orf 65) to develop a diagnostic enzyme-linked immunosorbent assay (ELISA) and tested sera from HIV-infected individuals with KS, HIV-uninfected patients with "classic" KS, other HIV risk groups, and blood donors. We also compared the antibody response to this capsid-related protein to the response to latent antigen(s) in an immunofluorescence assay.

FINDINGS

77/92 (84%) sera from KS patients reacted with the KSHV orf 65 protein and 84/103 (81.5%) reacted with KSHV latent antigen(s). The dominant immunogenic region of orf 65 is within the carboxyterminal 80 aminoacids, a region with little sequence similarity to the related Epstein-Barr virus, suggesting that orf 65 is a KSHV specific antigen. Only three sera from patients with haemophilia (1/84) or from intravenous drug users (2/63) had KSHV specific antibodies in the orf 65 assay whereas none of these sera reacted with latent antigen. Antibodies to KSHV were also infrequently found in UK and US blood donors by either assay (UK, 3/174 with orf 65 and 4/150 with latent antigen; US, 6/117 with orf 65 and 0/117 with latent antigen). They were more common among HIV-infected gay men without KS (5/16 by orf 65 ELISA, 10/33 by IFA), HIV-uninfected STD clinic attenders (14/166 by IFA), and Ugandan HIV-uninfected controls (6/17 by orf 65 ELISA, 9/17 by IFA). Antibody reactivity to the orf 65 protein (ELISA) and to latent antigen(s) (IFA) was concordant in 89% of 462 sera tested but reactive blood donor sera were discordant in both assays. Four AIDS-KS sera were unreactive in both assays.

INTERPRETATION

The distribution of antibodies to both a capsid-related recombinant protein and latent antigen(s) of KSHV strongly supports the view that infection with this virus is largely confined to individuals with, or at increased risk for, KS. However, infection with KSHV does occur, rarely, in the general UK and US population and is more common in Uganda. Antibodies to latent antigen(s) or to orf 65 encoded capsid protein will not detect all cases of KSHV infection, and a combination of several antigens will probably be required for accurate screening and confirmatory assays.

Expression of adhesion molecules in endemic and epidemic Kaposi's sarcoma

Spindle cells and vascular endothelium in nodular lesions of AIDS associated (epidemic) and endemic Kaposi's sarcoma showed similar immunohistochemical patterns of expression for cell adhesion molecules and extracellular matrix proteins. Spindle cells as well as endothelium also expressed both alpha 5 and alpha V integrin subunits and ICAM-1 suggesting a possible role for inflammatory cytokines in spindle cell formation. The spindle cell compartment was rich in collagen, laminin, fibronectin and tenascin suggesting an important reactive component in the evolution of Kaposi's sarcoma. The lack of thrombospondin expression in the spindle cells favours the contention that they could be transitional, proliferating cells of endothelial origin. Specific expression of tat protein was not seen suggesting minimal if any HIV replication in these lesions. Our findings suggest similar histopathogenetic mechanisms for endemic and epidemic Kaposi's sarcoma. The clinically more malignant features of most AIDS related cases may reflect an important effect of systemic and focal cytokines in HIV patients and possibly other cofactor(s), i.e. tat protein in the induction and growth of the lesions.

KSHV sequences in biopsies and cultured spindle cells of epidemic, iatrogenic and Mediterranean forms of Kaposi's sarcoma

The pathogenesis of Kaposi's sarcoma (KS) is still unclear, and several factors appear to be involved in the onset of the Kaposi's lesion. Epidemiological studies suggest that a common infective agent may contribute to KS. Sequences which appear to represent a new gammaherpesvirus, currently termed KSHV/HHV8, have recently been identified in KS. To further examine the relationship between this virus and KS, we obtained biopsy samples of KS lesions; these samples, the spindle cells cultured from these lesions and the PBMC of the same patients were tested for the presence of KSHV sequences by PCR. In addition, we tested several "late passage" KS spindle cell lines as well as control samples. The biopsy samples were from lesions of the following forms of KS: one sporadic KS, two epidemic KS and three iatrogenic KS, one of which was in the process of regressing after reduction of immunosuppressive therapy, and two that were at different stages (patch and nodular) from a single patient. The sporadic KS specimen was positive, as were the PBMCs from this patient, and cells grown from this biopsy appeared to contain KSHV viral sequences up to the fifth passage. Both epidemic KS biopsies were positive, but in these cases KSHV sequences were not detected in the cultured cells. The biopsy from the regressing iatrogenic KS lesion was negative, as were the cells cultured from this lesion. However, the PBMCs of this patient were weakly positive for KSHV at the time of biopsy, and PBMCs collected from this patient one month later were completely negative. The samples of both the patch and the nodular KS lesions obtained from another immunosuppressed patient showed amplifiable sequences of KSHV, but both the PBMCs of this patient and primary KS cell cultures from these biopsies were negative. Of the late-passage KS lines tested, only one, IST AIDS KS 12, was positive for KSHV. This line is derived from an early angiomatous-macula lesion. Taken together, these data suggest that an active KSHV infection is associated with KS and that elimination of KSHV from the lesion precedes regression of the lesion, strongly correlating KSHV with KS. In addition, early KS lesions may have a higher KSHV burden, or contain cells more susceptible to KSHV infection, further linking KSHV to KS.