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

Kaposi's sarcoma (KS) is a malignancy suspected of having an infectious etiology. Unique viral DNA sequences were recognized in KS lesions, using a novel technique that identifies small differences between two complex genomes. The virus had homology with the herpesvirus family, especially Epstein Barr virus (EBV), yet it was distinct from the known herpesviridae, and was appropriately named human herpesvirus 8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus (KSHV). HHV-8 DNA sequences were present in AIDS-associated KS, classic KS, African endemic KS, Mediterranean KS, iatrogenic KS, and KS in homosexual men without HIV infection. HHV-8 DNA sequences were also present in peripheral blood mononuclear cells (PBMC) of KS+ patients; body-cavity-based lymphomas in HIV positive patients without KS; and in tissue from a number of malignant and non-malignant lesions in patients without HIV infection. The role of HHV-8 in KS and other malignancies is not known. Viruses are notoriously trophic for lesional tissue. Therefore, in order to determine the role of HHV-8 in KS pathogenesis, HHV-8 needs to be isolated and shown to induce immortalization in a suitable system. Regardless of its role in KS, another human herpesvirus has been discovered, and the extent of its pathogenicity needs to be uncovered.Abbreviations KS Kaposi's sarcoma - HHV-8 human herpesvirus-8 - KSHV Kaposi's sarcoma-associated herpesvirus - EBV Epstein-Barr virus RDA representational difference analysis     

Dominant human herpesvirus type 8 RNA transcripts in classical and AIDS-related Kaposi's sarcoma

Skin biopsy sections of Kaposi's sarcoma (KS) from 25 patients (5 AIDS-related, 20 classical cases) were histologically staged and hybridized in situ with oligonucleotide probes for constitutively transcribed human herpesvirus 8 (HHV-8) mRNA T0.7 and T1.1 using a colourimetric technique. T1.1 increases during experimental induction of the viral lytic phase in the HHV-8-infected lymphocytes of primary effusion lymphoma and its colourimetric detection in KS cells presumably corresponds to virion production. Immunostaining with anti-CD20, CD45RO, MAC 387, and α-smooth muscle actin was performed following T1.1 in situ hybridization (ISH). When the amount of T0.7 was above the detection threshold, the signal was made up of multiple coarse intranuclear dots in most spindle cells. Of the six early-stage lesions, none produced a T1.1 hybridization signal. Two of four AIDS-related and two of eight classical lesions with incipient spindle cell growth produced rare but distinct dense intranuclear T1.1 signals in endothelial cells lining narrow tubes. In contrast, eight of ten (all classical KS) mature spindle cell lesions displayed a signal, scattered in up to 2 per cent of spindled endothelial cells. Cell types other than endothelium produced no T1.1 hybridization signal in double stains. The results are consistent with other published data indicating latent HHV-8 infection in endothelium and its tumour cell progeny, with simultaneous virion production in a small subset of cells. Immunodeficiency may not influence the number of cells lytically infected with HHV-8 in early KS, in contradistinction to other herpesviruses with latent-lytic cycles. Copyright © 1999 John Wiley & Sons, Ltd.     

Human herpesvirus 8 oral shedding in HIV-infected men with and without Kaposi sarcoma

OBJECTIVES: Two main routes of human herpesvirus 8 (HHV-8) transmission are known: sexual, predominantly in men who have sex with men; and nonsexual, in endemic populations. Both routes implicate saliva, so identifying the factors that influence oral HHV-8 shedding is important. METHODS: Using polymerase chain reaction and immunohistochemistry, we prospectively analyzed HHV-8 infection of oral epithelial cells in 98 Swiss HIV Cohort Study patients, with mean follow-up of 9.4 years, and correlated data to immune status, HHV-8 serology, and Kaposi sarcoma (KS) history, as well as survival. RESULTS: Sixty-eight (43.9%) of the 98 men were HHV-8 seropositive, and 33 (33.67%) had a history of KS. In both groups, men who have sex with men were significantly more affected than heterosexuals (P < 0.05). Of 77 patients, 9 (11.6%) were oral HHV-8 polymerase chain reaction positive, and 2 of these were also positive by immunohistochemistry. Oral HHV-8 detection was not influenced by the immune status, but a trend toward higher detection was observed in patients with KS (P = 0.084). Oral HHV-8 shedding had no predictive value either for the development of KS lesions or for survival. CONCLUSIONS: Human herpesvirus 8 can be present in oral epithelial cells and is shed independent of the patient's immune status, indicating that oral HHV-8 shedding may occur at any time in HHV-8-seropositive individuals.     

Consistent polymerse chain reaction–single-strand conformation polymorphism pattern of human herpesvirus-8 in the course of classical Kaposi's sarcoma assumes its clonal origin

There is emerging evidence that Kaposi's sarcoma–associated herpesvirus (KSHV or HHV-8) has a central role in the pathogenesis of Kaposi's sarcoma (KS). The occurrence of HHV-8 in classical KS biopsies is reported irrespective of its clinical stage (patch, plaque, nodular). HHV-8 was detected in 25 of 28 formalin-fixed paraffin-embedded classical KS samples by nested polymerase chain reaction. In addition, in six patients multiple tumors were available (n = 21). Single-strand conformation polymorphism (SSCP) analysis of the amplicons showed uniform SSCP pattern of samples belonging to the same patient regardless of whether the KS was multiplex or developed again years after the first excision. Most of the SSCP patterns were confirmed by further sequence analysis. The presence of the same sequence variant of HHV-8 in various samples of the same patient supports the clonal origin of classical Kaposi's sarcoma. J. Med. Virol. 54:300–304, 1998. © 1998 Wiley-Liss, Inc.     

Detection of the herpesvirus-like DNA sequences in matched specimens of semen and blood from patients with AIDS-related Kaposi's sarcoma by polymerase chain reaction in situ hybridization.

The DNA sequences of a novel human gamma-herpesvirus type 8 (HHV-8) have recently been detected in Kaposi's sarcoma (KS) lesions obtained from different populations in whom this neoplasm occurs, suggesting that this virus may be implicated in the etiology and/or pathogenesis of KS. To study the distribution and possible means of transmission of the putative viral agent, specimens of KS skin lesions, matched uninvolved skin, peripheral blood mononuclear cells (PB-MCs), and semen were collected from 12 HIV-positive homosexual men with acquired immune deficiency syndrome (AIDS)-related KS (AIDS-KS) and 2 human immunodeficiency virus (HIV)-negative homosexual men with KS. HHV-8 virus DNA was detected by polymerase chain reaction (PCR) studies in all 14 of these KS specimens and in 6 of 14 biopsies of normal-appearing skin distant from any KS lesions including 1 uninvolved skin specimen from an HIV-negative homosexual male with KS. In addition, 3 of 12 PBMC samples and 3 of 12 semen samples from the AIDS-KS patients were positive for HHV-8. The DNA sequences of HHV-8 were not detected in the matched semen and PBMC specimens obtained from 2 HIV-negative homosexual men with KS, 4 HIV-positive homosexual patients without KS, 2 HIV-seronegative healthy homosexual men, 5 HIV-positive heterosexual male intravenous drug users, or 5 healthy HIV-negative heterosexual donors. Using PCR in situ, positive signals for HHV-8 were demonstrated in the B lymphocyte subsets of PBMCs and/or in spermatozoa and mononuclear cells in the semen from some of the PCR-positive specimens from the AIDS-KS patients examined. These data show that HHV-8 is present in and could possibly be transmitted via semen and/or blood from some homosexual men with AIDS-KS.     

Human herpesvirus 8 reactivation and human immunodeficiency virus type 1 gp120

CONTEXT: Human herpesvirus 8 (HHV-8) is the presumed etiologic agent of Kaposi sarcoma (KS), the most common neoplasm in patients with acquired immunodeficiency syndrome. Current evidence indicates HHV-8 is necessary, but not sufficient, for KS development without the involvement of other cofactors. One potentially important cofactor is human immunodeficiency virus type 1 (HIV-1). Although HIV-1 is not essential for development of KS, studies have shown factors released from HIV-1-infected cells, including HIV-1 proteins and cytokines, promote the growth of KS cells in vitro. Recently, studies have shown that coculture of HIV-1-infected T cells with HHV-8-infected primary effusion lymphoma cell lines results in HHV-8 reactivation. This response was due, in part, to cytokines. However, only a portion of induced HHV-8 replication could be accounted for by cytokine stimulation, indicating that other factors, including HIV-1-associated proteins, may also be involved. OBJECTIVE: To investigate a possible role for HIV-1 gp120 in HHV-8 reactivation. DESIGN: Using an in vitro model system, we examined the effect of recombinant HIV-1 gp120 protein on HHV-8 replication in latently infected primary effusion lymphoma cell lines. MAIN OUTCOME MEASURES: Reactivation of HHV-8 was analyzed using Northern blot analysis and quantitative polymerase chain reaction for ORF26 messenger RNA expression, a gene encoding for the HHV-8 minor capsid protein produced only during reactivation. The results were extended and confirmed using a luciferase reporter construct driven by the HHV-8 ORF50 promoter, the first promoter activated during HHV-8 replication. RESULTS: No evidence of enhanced HHV-8 replication was found following treatment with HIV-1 gp120. In addition, HIV-1 gp120 was unable to act synergistically with interferon-gamma or hepatocyte growth factor/scatter factor to enhance reactivation of the virus in infected primary effusion lymphoma cell lines. CONCLUSIONS: HIV-1 gp120 does not appear to be responsible for the reactivation of HHV-8 demonstrated in our previous studies. Further studies are necessary to determine if other HIV-associated proteins, particularly Tat, gp160, and/or gp41, which are also released from infected cells, may be important in inducing HHV-8 reactivation.     

Antiretroviral therapy with protease inhibitors in human immunodeficiency virus type 1– and human herpesvirus 8–coinfected patients

Human herpesvirus 8 (HHV-8) is believed to play a role in the pathogenesis of Kaposi's sarcoma (KS) and possibly in other proliferative disorders often associated with human immunodeficiency virus type 1 (HIV-1) infection. Recent case reports have indicated resolution of KS and clearance of HHV-8 DNA from peripheral blood mononuclear cells (PBMC) in HIV-1–infected subjects following highly effective antiretroviral therapy, including HIV-1 protease inhibitors (PI), suggesting a possible activity for these compounds on HHV-8 replication. In the present study, the time course of PBMC HHV-8 DNA levels, plasma HIV-1 RNA load, and CD4⁺ T-cell counts were followed up in six coinfected subjects (four with and two without KS) under antiretroviral therapy with PI. A specific anti–HHV-8 role for PI was not consistently found, since fluctuation of HHV-8 viral load over time appeared to be independent of treatment. Nevertheless, our data support the hypothesis that KS patients may significantly benefit from PI therapy as an indirect consequence of partial restoration of immune functions following effective anti–HIV-1 combination therapy. J. Med. Virol. 57:140–144, 1999. © 1999 Wiley-Liss, Inc.     

Geographically Distinct HHV-8 DNA Sequences in Saudi Arabian Iatrogenic Kaposi’s Sarcoma Lesions

A new member of the γ-herpesvirus family, HHV-8 (also known as Kaposi’s sarcoma (KS)-associated herpesvirus), has been linked to KS and body cavity-based lymphoma. Other members of this family, eg, Epstein-Barr virus, were originally thought to have only one strain, but subsequent analysis revealed different strains correlating to cellular patterns of infectivity and geographical location. To determine whether multiple strains of HHV-8 exist, we compared DNA sequences among KS and body cavity-based lymphoma-derived HHV-8 and examined differences in HHV-8 subgroups between American and Saudi Arabian iatrogenic KS patients. Samples were analyzed by polymerase chain reaction using multiple primer sets to five different open reading frames from HHV-8, and DNA sequencing was performed. HHV-8 DNA was present in all of our KS and body cavity-based lymphoma samples by polymerase chain reaction. HHV-8 DNA was detected in each body cavity-based lymphoma sample using a majority of the primers, whereas only two primer sets consistently amplified HHV-8 DNA derived from KS lesions. DNA sequencing within open reading frames 26 and 27 indicate the existence of at least three variants of HHV-8, with the majority of iatrogenic KS patients in Saudi Arabia containing unique nucleotide changes that may define a distinct, previously unidentified subgroup we term SA, whereas those from America were of Group A or B. Thus, although the sequencing data within open reading frames 26 and 27 did not permit discrimination between patients with lymphoma versus KS disease processes, HHV-8 derived from Saudi Arabian KS lesions were shown to have a distinct nucleotide sequence not seen in any of the other clinical samples examined.     

Detection of antibodies against viral capsid proteins of human herpesvirus 8 in AIDS-associated Kaposi’s sarcoma

 Sequences of a new herpesvirus with homology to gammaherpesvirinae were recently identified in AIDS-associated Kaposi’s sarcoma (KS). Subsequently this novel virus, called KS-associated virus (KSHV) or human herpesvirus (HHV) 8 was detected in classical KS and AIDS-associated body cavity based lymphomas by polymerase chain reaction. In this report major and minor capsid proteins of HHV-8 were molecularly cloned and produced as recombinant proteins in Escherichia coli. Sera from 69 HIV-1 infected patients with KS, 30 HIV-1 infected patients without KS and 106 control individuals were tested by enzyme-linked immunosorbent assay for anti-HHV-8 capsid IgM and IgG antibodies. Sera from four patients were tested over periods ranging from 18 months to 6 years. IgG antibodies directed against HHV-8 capsid antigens were detected in patients with AIDS-associated KS and in some AIDS patients without KS. Seroconversion with IgM and IgG antibodies directed against HHV-8 capsid proteins occurred more than 1 year prior to diagnosis of KS. In a considerable portion of KS patients no IgM or IgG antibodies against HHV-8 capsid proteins were detected. In these patients there was an inverse relationship between antibodies against HHV-8orf26 and the CD4/CD8 ratio, suggesting that the inconsistency of anti-HHV-8orf26 antibodies is due at least partly to an impaired immune response. No reactivity against HHV-8 capsid antigens was detected in the vast majority of sera from HIV-negative control individuals. Our findings indicate that a specific humoral immune response against capsid proteins is raised in HHV-8 infected individuals, and that anti-capsid antibodies can be used to diagnose HHV-8 infection. The correlation between occurrence of anti-HHV-8 antibodies and KS supports the hypothesis of a causative role of HHV-8. Received: 3 August 1996 / Accepted: 28 November 1996     

Localization of human herpes-like virus type 8 in vascular endothelial cells and perivascular spindle-shaped cells of Kaposi's sarcoma lesions by in situ hybridization.

Kaposi''s sarcoma (KS) is a neoplasm that develops as multifocal lesions characterized by a histological picture that includes irregularly shaped vascular spaces surrounded by perivascular and interstitial spindle-shaped cells, extravasated erythrocytes, and an inflammatory mononuclear cell infiltrate. Recently, the DNA sequences of a novel human gamma-herpesvirus-like (HHV-8) agent have been detected by polymerase chain reaction in KS associated with acquired immune deficiency syndrome (AIDS-KS), classical KS, and African endemic KS. The present study was done to identify the specific cells within KS tumors that contain the viral DNA. Fourteen skin biopsy specimens, including three classical KSs, six AIDS-KSs, three normal skin specimens, and two common warts from healthy individuals, were examined by polymerase chain reaction for the presence of the HHV-8 DNA sequences. HHV-8 DNA were present in all nine KS specimens but not detectable in the five non-KS tissue samples. Using in situ hybridization, we found the HHV-8 DNA sequences to be predominantly localized to the nuclei of endothelial cells lining the vascular slits and some perivascular spindle-shaped cells, in two of three KS and four of six AIDS-KS tissue sections examined. The HHV-8-positive cells of KS specimens were concurrently shown to also be positive for factor-VIII-related antigen by immunohistochemical staining. The presence of the DNA of HHV-8 in the nuclei of KS cells further supports the possibility that this agent may play a role in the pathogenesis of this tumor.     

Proteomic characterization of HIV-modulated membrane receptors, kinases and signaling proteins involved in novel angiogenic pathways

Background  

Kaposi's sarcoma (KS), hemangioma, and other angioproliferative diseases are highly prevalent in HIV-infected individuals. While KS is etiologically linked to the human herpesvirus-8 (HHV8) infection, HIV-patients without HHV-8 and those infected with unrelated viruses also develop angiopathies. Further, HIV-Tat can activate protein-tyrosine-kinase (PTK-activity) of the vascular endothelial growth factor receptor involved in stimulating angiogenic processes. However, Tat by itself or HHV8-genes alone cannot induce angiogenesis in vivo unless specific proteins/enzymes are produced synchronously by different cell-types. We therefore tested a hypothesis that chronic HIV-replication in non-endothelial cells may produce novel factors that provoke angiogenic pathways.     

Occult lymphadenopathic Kaposi's sarcoma associated with severe pulmonary hypertension: A clinical hint about the potential role of HHV-8 in HIV-related pulmonary hypertension?

Severe pulmonary hypertension (PH) mimicking idiopathic PH is an increasingly recognized complication of human immunodeficiency virus (HIV) infection. PH shares several histopathologic features with Kaposi's sarcoma (KS), the most common malignancy in AIDS patients, and molecular evidence of the vasculotropic Kaposi's sarcoma-associated herpesvirus or human herpesvirus 8 (HHV-8) has been found in the lung tissue of patients with the disease. Although the prevalence of HHV-8 infection is increased among HIV-infected patients, no clinical association between KS and PH has ever been reported. Herein, we described a 30-year-old HIV-infected female co-infected with HHV-8 who developed severe PH coincident with occult KS. The clinical presentation of KS was unusual and remained masqueraded for years as an indolent cervical lymphadenopathy, without the typical cutaneous lesions. This is the first ever-reported case of PH associated with KS. Although the co-occurrence of both diseases in this patient could have been just a coincidence, the observation may also indicate that a relationship between HHV-8 infection and HIV-associated PH exists. Coinfection with HHV-8 and occult lymphadenopatic KS should be considered in HIV-infected patients developing PH.     

Unique expression pattern of viral proteins in human herpesvirus 8-positive plasmablastic lymphoma: a case report

Background: Human herpesvirus 8 (HHV8)-positive plasmablastic lymphoma is a disease which correlates with acquired immunodeficiency syndrome (AIDS). Little is known about the pathogenesis of the disease due to its rarity. We report an autopsy case about AIDS related HHV-8-positive plasmablastic lymphoma and presents an examination about HHV8 related proteins for the disease by using immunohistochemical techniques. Case presentation: Two kinds of tumors complicated the male AIDS patient: one was HHV-8-positive plasmablastic lymphoma and the other was Kaposi’s sarcoma (KS). Immunohistochemically, the lymphoma cells were positive for HHV8-associated lytic early proteins as well as HHV8 latency-associated nuclear antigen 1 (LANA-1), and, on the other hand, the lymphoma cells were negative for lytic immediately early proteins. KS was positive for only LANA-1. Conclusion: These findings indicate that the lymphoma cells acquired an ability to proliferate without de novo HHV8 replication. Moreover, the onset mechanisms of HHV-8-positive plasmablastic lymphoma may be different from those of KS.     

Localisation of HHV-8 in AIDS related lymphadenopathy.

BACKGROUND: Many lymph node abnormalities have been described in AIDS. These include opportunistic infections that sometimes result in spindle cell pseudotumours, Kaposi's sarcoma (KS), malignant lymphoma (Hodgkin's and non-Hodgkin's), and florid reactive hyperplasia. Among these, reactive hyperplasia is the most common manifestation of AIDS related lymphadenopathy. AIM: To examine whether human herpesvirus 8 (HHV-8), the aetiological agent of KS, can be localised in AIDS related lymphadenopathy and whether its appearance in such nodes is predictive of Kaposi's sarcoma development. METHODS: A series of human immunodeficiency virus (HIV) positive men (n = 21) with AIDS related lymphadenopathy who at the time of presentation had KS or subsequently developed KS (n = 5) were examined. The prevalence of HHV-8 was assessed in these patients using solution phase polymerase chain reaction (PCR), real time TaqMan quantitative PCR, and in cell amplification techniques (PCR in situ hybridisation (PCR-ISH) and labelled primer driven in cell amplification). RESULTS: Using standard solution phase PCR in a nested format, only two of the 21 patients with AIDS related lymphadenopathy were positive for HHV-8. The lymph node of one of these patients contained KS lesions. Three HHV-8 positive patients were identified using TaqMan PCR (the original two positive patients and one additional patient). All of the positive patients either subsequently developed KS (n = 2) or had KS at the time of diagnosis (n = 1). Two additional patients subsequently developed KS, but were negative for HHV-8 by solution phase PCR and TaqMan PCR. Using PCR-ISH, HHV-8 amplicons were identified in some lymphoid cells (in one patient) and in spindle cells of the KS lesion in another. The positive lymphoid cells were predominantly concentrated in B cell areas of the affected lymph nodes, confirming the B cell tropism exhibited by HHV-8. CONCLUSIONS: The presence of HHV-8 in AIDS related lymphadenopathy is predictive of KS development and probably represents seeding of HHV-8 infected B cells from the peripheral blood. These findings support a role for HHV-8 in the pathobiology of KS.     

Human herpesvirus 8 (HHV-8) detected in two patients with Kaposi's sarcoma-like pyogenic granuloma

AIMS: To report the finding of human herpesvirus 8 (HHV-8) in two patients with Kaposi's sarcoma (KS)-like pyogenic granuloma. This form of pyogenic granuloma closely resembles KS histologically and it has been reported that immunohistochemistry in such lesions may be positive for smooth muscle actin and factor VIII related antigen, which are typically negative in KS. In both patients the lesions were positive for CD31, CD34, smooth muscle actin, and factor VIII related antigen, a profile typical of KS-like pyogenic granuloma. The lesions were tested for the presence of HHV-8 DNA, which to date has been consistently found in all types of KS. METHODS: The lesions were tested for the presence of HHV-8 DNA using the polymerase chain reaction (PCR). A known HHV-8 positive KS specimen was used as the positive control. Six samples of non-KS vascular skin lesions were used as negative controls for the PCR reaction. RESULTS: Both lesions were positive on PCR for HHV-8 and the specificity of product was confirmed by direct sequencing. None of the six control vascular skin lesions was positive for HHV-8. These results strongly indicate KS as the true diagnosis and are supported by the reported clinical course in both cases. CONCLUSIONS: Techniques targeting HHV-8 DNA for detection to confirm a diagnosis of KS are both sensitive and specific. In cases where the differential diagnosis includes KS-like pyogenic granuloma, caution should be taken not to diagnose solely on the basis of immunohistochemistry phenotype. In such cases, PCR targeting HHV-8 DNA sequences is a better diagnostic tool.     

Human herpesvirus 8/Kaposi sarcoma herpesvirus cell association during evolution of Kaposi sarcoma

Kaposi sarcoma (KS) is associated with a herpesvirus (HHV-8/KSHV), which expresses a latency-associated nuclear antigen (LANA). The histopathology of KS is characterized by angiogenesis, inflammatory cells, and the development of CD34+ tumor spindle cells (SCs). However, the cellular basis for the recruitment and dissemination of HHV-8 during the development of KS lesions is not clear. Twenty-nine KS biopsies with AIDS (AKS, n=22) and without HIV infection (endemic KS or EKS, n=7) were immunostained by a triple antibody method to characterize HHV-8-infected and noninfected (LANA+/-) CD34+ SCs, infiltrating CD3+, CD68+, CD20+, and CD45+ leukocytes as well as proliferating (Ki67+) cells. The CD34+/LANA+ SCs were more frequent in late (nodular) as compared with early (patch/plaque) KS stages. However, in late AKS 36.0% of SCs (median of 11 cases) were CD34+/LANA- compared with 20.7% in early cases (median of 11 cases). Furthermore, both AKS and EKS showed, at all stages, a small (4.1-6.5%) population of LANA+/CD34- cells. Proliferating Ki67+ cells were seen (4.5-11.5%) at all KS stages, and were usually more frequent in early AKS, but no significant difference was observed between nodular AKS and EKS. Most of the proliferating cells in the KS lesions were LANA+/CD34+ but a small fraction was LANA+/CD34-. Lesional CD68+ and CD3+ cells varied between AKS (7.3 and 5.2%, respectively) and EKS (4.9 and 3.1%, respectively) but were not clearly stage related. No LANA+ cells were CD3+, CD20+, or CD45+ and very few (<0.5%) were CD68+. These results indicate that not all CD34+ KS SCs were LANA+, suggesting recruitment of noninfected SCs to the lesions. Cell proliferation in general was much higher in early as compared with the late AKS stages. LANA+ SCs could have a proliferative advantage as suggested by higher frequency of cycling (Ki67+) LANA+ SCs. Few macrophages but no lymphocytes are LANA+.     

Expression and antigenicity of human herpesvirus 8 encoded ORF59 protein in AIDS-associated Kaposi's sarcoma.

Human herpesvirus 8 (HHV-8, Kaposi's sarcoma-associated herpesvirus, KSHV) is a new herpes virus isolated from patients with AIDS-associated Kaposi's sarcoma (AIDS-KS). The ORF59 protein of HHV-8 has recently been shown to encode a processivity factor (PF-8) for HHV-8-encoded DNA polymerase. By immunoscreening a cDNA library derived from the HHV-8-infected cell line TY-1, ORF59 antigen was identified in AIDS-KS patients. Immunoblotting revealed that recombinant ORF59 protein reacted with sera from patients with AIDS-KS. Enzyme-linked immunosorbent assay (ELISA) using ORF59-recombinant protein as the antigen revealed that 7 of 22 (31. 8%) AIDS-KS patients and 6 of 263 (2.2%) Japanese HIV-negative patients or healthy blood donors were positive for anti-ORF59 antibodies. Immunohistochemistry using anti-ORF59 rabbit antibodies revealed that this protein was expressed in some of the tumor cells found in KS tissues and that ORF59 protein was detected in 11 of 22 (50%) AIDS-KS tissues. In situ hybridization indicated that some of KS tumor cells were positive for HHV-8 T1.1 mRNA in the same specimen. These data suggest that ORF59 is one of the HHV-8 encoded antigens in patients with AIDS-KS and also indicated that viral replication occurred in some of KS tumor cells.