Human herpesvirus 8 (HHV-8; Kaposi's sarcoma-associated herpesvirus is linked to Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD), all of which are viewed as cytokine-driven malignancies. In particular, interleukin-6 (IL-6) has been found to promote the growth and proliferation of cells from KS and PEL. HHV-8 encodes a homologue of IL-6 (viral IL-6 [vIL-6]), which functions similarly to the cellular IL-6. Therefore, vIL-6 has been proposed to play an important role in tumor progression. Several groups have reported that vIL-6 is expressed from the HHV-8 genome at higher levels in PEL and MCD lesions than in KS lesions. However, it is not clear how vIL-6 expression is regulated. We characterized the transcription at the vIL-6 gene locus by Northern blot analysis and, in contrast to previous reports, we observed two distinct transcripts from induced PEL cell lines. This observation was confirmed by primer extension, as well as 5′ and 3′ rapid amplification of cDNA ends. Two transcription initiation sites and putative TATA boxes were mapped. A luciferase reporter system was used to show that each of the two putative TATA boxes contributed to vIL-6 promoter activity. Since virally encoded transcriptional activator Rta potently activates the viral lytic gene expression cascade, we examined the role of Rta in controlling vIL-6 gene expression and found that Rta activated the vIL-6 promoter. The Rta-responsive element was further mapped through a series of deletion constructs. Electrophoretic mobility shift assays demonstrated that Rta binds directly to the vIL-6 Rta-responsive element, and the core Rta-responsive element was mapped to a 26-bp region spanning from nucleotide 18315 to 18290 on the viral genome. We propose that the existence of two vIL-6 promoters offers opportunities for differential regulation of vIL-6 gene expression in different tissue types and may account for the variable vIL-6 levels observed in KS, PEL, and MCD.
Human herpesvirus 8 (HHV-8) infection has been implicated in the etiology of Kaposi’s sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman’s disease (MCD), three diseases that frequently develop in immunocompromised, human immunodeficiency virus-positive individuals. One hypothesis that would account for different pathological manifestations of infection by the same virus is that viral genes are differentially expressed in heterogeneous cell types. To test this hypothesis, we analyzed the localization and levels of expression of two viral genes expressed in latent and lytic infections and the viral homologue of interleukin-6 (vIL-6). We show that PEL parallels KS in the pattern of latent and lytic cycle viral gene expression but that the predominant infected cell type is a B cell. We also show that MCD differs from KS not only in the infected cell type (B-cell and T-cell lineage) but also in the pattern of viral gene expression. Only a few cells in the lesion are infected and all of these cells express lytic-cycle genes. Of possibly greater significance is the fact that in a comparison of KS, PEL, and MCD, we found dramatic differences in the levels of expression of vIL-6. Interleukin-6 is a B-cell growth and differentiation factor whose altered expression has been linked to plasma cell abnormalities, as well as myeloid and lymphoid malignancies. Our findings support the hypothesis that HHV-8 plays an important role in the pathogenesis of PEL and MCD, in which vIL-6 acts as an autocrine or paracrine factor in the lymphoproliferative processes common to both.
Human herpesvirus 8 (HHV-8) is found in immunoblastic B cells of patients with multicentric Castleman's disease (MCD) and, predominantly in a latent form, in primary effusion lymphoma (PEL) cells and Kaposi's sarcoma (KS) spindle cells. Recent studies have shown that upon reactivation, HHV-8 expresses factors that downregulate major histocompatibility class I proteins and coactivation molecules and that may enable productively infected cells to escape cytotoxic T lymphocytes and natural killer cell responses. One of these viral factors is encoded by open reading frame (ORF) K3. Here we show that in PEL cells, ORF K3 is expressed through viral transcripts that are induced very early upon virus reactivation, including bicistronic RNA molecules containing coding sequences from viral ORFs K3 and 70. Specifically, we found that a bicistronic transcript was expressed in the absence of de novo protein synthesis, thereby identifying a novel HHV-8 immediate-early gene product. Several features of the RNA molecules encoding the K3 product, including multiple transcriptional start sites, multiple donor splicing sites, and potential alternative ATG usage, suggest that there exists a finely tuned modulation of ORF K3 expression. By contrast, ORF K3 transcripts are not detected in the majority of cells present in KS lesions that are latently infected by the virus, suggesting that there are other, as-yet-unknown mechanisms of immune evasion for infected KS spindle cells. Nevertheless, because HHV-8 viremia precedes the development of KS lesions and is associated with the recrudescence of MCD symptoms, the prompt expression of ORF K3 in productively infected circulating cells may be important for virus pathogenesis. Thus, molecules targeting host or viral factors that activate ORF K3 expression or inactivate the biological functions of the K3 product should be exploited for the prevention or treatment of HHV-8-associated diseases in at-risk individuals.
Human herpesvirus 8 (HHV-8) infection is associated with Kaposi’s sarcoma, primary effusion lymphoma (PEL), and multicentric Castleman’s disease. In this study, we used monoclonal antibodies (MAbs) directed against HHV-8 lytic cycle-associated proteins encoded by open reading frame (ORF) 59 (nuclear PF-8 protein) and ORF K8.1 (viral envelope glycoprotein K8.1 [gpK8.1]) to investigate HHV-8 lytic infection in single cells. Lytically infected cells were labeled with MAbs, stained with fluorescently conjugated secondary Abs, and analyzed by flow cytometry. A 3-day stimulation of HHV-8-positive PEL cell lines (BCBL-1 and BC-3) with 12-O-tetradecanoylphorbol-13-acetate (30 nM) or n-butyric acid (0.3 mM) maximized the expression of lytic-phase viral proteins and minimized cell toxicity. The absolute number of expressing cells was inducer and cell line dependent. Expression of PF-8 occurred earlier and more frequently (in up to 20% of cells) than did expression of gpK8.1. A subset of PF-8 positive cells (25%) co-expressed gpK8.1, representing the majority of gpK8.1 expressing cells. Acyclovir, foscarnet, cidofovir, and PMEA reduced the number of cells expressing gpK8.1, but not the number expressing the nonstructural early lytic gene product PF-8. By contrast, alpha interferon (IFN-α) and IFN-β reduced expression of both PF-8 and gpK8.1, implying an overall inhibitory effect on viral gene transcription or translation. In summary, we have characterized and quantified HHV-8 lytic infection in single cells by dual measurement of early- and late-lytic-cycle HHV-8 protein expression. This technique should prove useful for screening of possible antiherpesvirus agents and for detailed phenotypic characterization of HHV-8-infected cells in vitro and in patients with HHV-8-associated diseases.
Human herpesvirus 8 (HHV-8) has been associated with classical, endemic (African), and AIDS-related Kaposi’s sarcoma (KS), body cavity-based primary effusion lymphomas, and multicentric Castleman’s disease (MCD). HHV-8 encodes a functional homologue of interleukin-6 (IL-6), a cytokine that promotes the growth of KS and myeloma cells and is found at elevated levels in MCD lesions and patient sera. We have previously reported that the viral IL-6 (vIL-6) gene product can support the growth of the IL-6-dependent murine hybridoma cell line, B9, and that the gp80 (IL-6 receptor [IL-6R]) component of the IL-6 receptor-signal transducer (gp180) complex plays a role in mediating this activity. However, it has been shown by others that vIL-6 can function in human cells independently of IL-6R. Here we have extended our functional studies of vIL-6 by identifying transcription factors and pathways used in human Hep3B cells, investigating the utilization of gp130 and IL-6R by vIL-6, and undertaking mutational analyses of vIL-6 and gp130. The data presented here establish that vIL-6, in common with its endogenous counterparts, can mediate signal transduction through gp130 and activate multiple transcription factors, map residues within the vIL-6 protein that are and are not important for vIL-6 signalling, and identify a gp130 mutant that is nonfunctional with respect to vIL-6 signalling in the absence of IL-6R but that retains the ability to mediate vIL-6 and human IL-6 (hIL-6) signal transduction when IL-6R is coexpressed. The data presented demonstrate functional and mechanistic similarities between vIL-6 and endogenous IL-6 proteins but also highlight differences in the structural and receptor-binding properties of vIL-6 relative to its human counterpart.
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.
Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), is the etiologic agent of all forms of Kaposi's sarcoma, primary effusion lymphoma and the plasmablastic cell variant of multicentric Castleman disease. In endemic areas of sub-Saharan Africa, blood transfusions have been associated with a substantial risk of HHV-8 transmission. By contrast, several studies among healthy blood donors from North America have failed to detect HHV-8 DNA in samples of seropositive individuals. In this study, using a real-time PCR assay, we investigated the presence of HHV-8 DNA in whole-blood samples of 803 HHV-8 blood donors from three Brazilian states (São Paulo, Amazon, Bahia) who tested positive for HHV-8 antibodies, in a previous multicenter study. HHV-8 DNA was not detected in any sample. Our findings do not support the introduction of routine HHV-8 screening among healthy blood donors in Brazil. (WC = 140).
Burkitt lymphoma (BL) is a highly aggressive non-Hodgkin lymphoma, composed of a monomorphic population of medium-sized B cells with a high proliferation rate and a consistent MYC translocation. Epstein-Barr virus (EBV) has been associated with BL with different frequencies depending on the clinical variant. Kaposi sarcoma–associated herpesvirus, or human herpesvirus 8 (HHV-8), infects a wide range of normal cells, having a well-established role in the pathogenesis of various neoplasms, including Kaposi sarcoma, primary effusion lymphoma, multicentric Castleman disease (MCD) and MCD-associated plasmablastic lymphoma. In secondary immunodeficiencies, such as HIV-1 infection and organ transplantation, HHV-8 is considered an opportunistic pathogen linked to the development of lymphomas in patients with AIDS and HIV+ patients. We studied the association of EBV and HHV-8 by immunohistochemical analysis, in situ hybridization, and polymerase chain reaction in a large number of well-characterized BLs. EBV was present in 45.0% of all BL cases with higher incidence in the pediatric group; most cases were EBV type A. We found no association of BL with HHV-8 in EBV+ BL or in EBV–cases, including the HIV+ BL group.
Burkitt lymphoma; Kaposi sarcoma–associated herpesvirus; Human herpesvirus 8; KSHV/HHV-8; LANA protein; HIV; Immunohistochemistry; Polymerase chain reaction; PCR
Kaposi sarcoma–associated herpesvirus (KSHV; also known as HHV8) is the causative agent of two B cell tumors, multicentric Castleman disease (MCD) and primary effusion lymphoma (PEL). However, little is known about the nature of the specific B cell subtype(s) most susceptible to infection. Identifying these cells would provide direct insight into KSHV transmission and virus-induced transformation. To identify this subset and to determine whether infection alters its cellular phenotype, we exposed human tonsillar cells to KSHV and characterized infected cells using high-throughput multispectral imaging flow cytometry (MIFC). Stable expression of the virally encoded latency-associated nuclear antigen (LANA), a marker of latent KSHV infection, was observed predominantly in cells expressing the l light chain of the B cell receptor. These LANA+ B cells proliferated and exhibited similarities to the cells characteristic of MCD (IgMl-expressing plasmablasts), including blasting morphology with elevated expression of Ki67, variable expression of CD27, and high levels of IgM and IL-6 receptor. Furthermore, the proportion of infected cells showing a blasting phenotype increased upon addition of exogenous IL-6. Our data lead us to propose that oral transmission of KSHV involves the latent infection of a subset of tonsillar IgMl-expressing B cells, which then proliferate as they acquire the plasmablast phenotype characteristic of MCD.
Kaposi’s sarcoma-associated herpesvirus (KSHV; human herpesvirus 8) is a human herpesvirus, classified as a gamma-herpesvirus. KSHV is detected in Kaposi’s sarcoma (KS), primary effusion lymphoma (PEL), and some cases of multicentric Castleman’s disease (MCD). Similar to other herpes viruses, there are two phases of infection, latent and lytic. In KSHV-associated malignancies such as KS and PEL, KSHV latently infects almost all tumor cells. Quantitative PCR analysis revealed that each tumor cell contains one copy of KSHV in KS lesions. The oncogenesis by KSHV has remained unclear. Latency-associated nuclear antigen (LANA)-1 plays an important role in the pathogenesis of KSHV-associated malignancies through inhibition of apoptosis and maintenance of latency. Because all KSHV-infected cells express LANA-1, LANA-1 immunohistochemistry is a useful tool for diagnosis of KSHV infection. KSHV encodes some homologs of cellular proteins including cell-cycle regulators, cytokines, and chemokines, such as cyclin D, G-protein-coupled protein, interleukin-6, and macrophage inflammatory protein-1 and -2. These viral proteins mimic or disrupt host cytokine signals, resulting in microenvironments amenable to tumor growth. Lytic infection is frequently seen in MCD tissues, suggesting a different pathogenesis from KS and lymphoma.
Kaposi’s sarcoma-associated herpesvirus; HHV-8; latency-associated nuclear antigen; LANA-1; primary effusion lymphoma
Multicentric Castleman's disease (MCD) is a rare disease, but is more frequent in AIDS patients. MCD has only been reported twice before in patients receiving immunosuppressive therapy after renal transplantation, and never in patients receiving immunosuppressive therapy without transplantation. About half of the cases of MCD are human herpesvirus 8 (HHV8) – related, in contrast to Kaposi's sarcoma, a more common complication arising after immunosuppression, where the virus is found in virtually all cases.
We report a HIV-1 negative, non-transplant patient who developed HHV8-associated multicentric Castleman's disease and Kaposi's sarcoma after 17 years of immunosuppressive treatment with cyclosporin A for a minimal change nephropathy. Chemotherapy with liposomal doxorubicin resolved both symptoms of multicentric Castleman's disease and Kaposi's sarcoma in this patient. A concomitant decline in the HHV8 viral load in serum/plasma, as determined by a quantitative real-time PCR assay, was observed.
Multicentric Castleman's disease can be a complication of cyclosporin A treatment. Both multicentric Castleman's disease and Kaposi's sarcoma in this patient were responsive to liposomal doxorubicin, the treatment of choice for Kaposi's sarcoma at the moment, again suggesting a common mechanism linking both disorders, at least for HHV8-positive multicentric Castleman's disease and Kaposi's sarcoma.
HHV8 viral load measurements can be used to monitor effectiveness of therapy.
Kaposi sarcoma herpesvirus (KSHV) is specifically associated with Kaposi sarcoma (KS) and 2 B cell lymphoproliferative diseases, namely primary effusion lymphoma (PEL) and multicentric Castleman disease (MCD). KS, PEL, and MCD are largely incurable and poorly understood diseases most common in HIV-infected individuals. Here, we have revealed the role of viral FLICE-inhibitory protein (vFLIP) in the initiation of PEL and MCD by specifically expressing vFLIP at different stages of B cell differentiation in vivo. Mice showed MCD-like abnormalities and immunological defects including lack of germinal centers (GCs), impaired Ig class switching, and affinity maturation. In addition, they showed increased numbers of cells expressing cytoplasmic IgM-λ, a thus far enigmatic feature of the KSHV-infected cells in MCD. B cell–derived tumors arose at high incidence and displayed Ig gene rearrangement with downregulated expression of B cell–associated antigens, which are features of PEL. Interestingly, these tumors exhibited characteristics of transdifferentiation and acquired expression of histiocytic/dendritic cell markers. These results define immunological functions for vFLIP in vivo and reveal what we believe to be a novel viral-mediated tumorigenic mechanism involving B cell reprogramming. Additionally, the robust recapitulation of KSHV-associated diseases in mice provides a model to test inhibitors of vFLIP as potential anticancer agents.
A 57 year old Italian female with a 3 year history of constituitional symptoms with non-HIV Kaposi sarcoma was referred to the immunology clinic. She was previously diagnosed with chronic human herpes virus 8 (HHV8) infection with positive HHV8 polymerase chain reaction in serum.
Is valganciclovir effective in treating chronic human herpes virus 8 infection without Multicentric Castleman's Disease (MCD)?
She was started on valganciclovir, resulting in remission of her symptoms, improvement in inflammatory markers and clearing of detectable HHV8 viraemia
Valganciclovir is effective in treating symptomatic HHV8 infections without MCD.
human herpes virus 8; valganciclovir; Kaposi sarcoma
Background: Although rare in mainland Japan, classic Kaposi’s sarcoma (KS) is frequently reported in Okinawa, a subtropical island in southern Japan. Human herpesvirus 8 (HHV8) has been identified in the tumours and geographical differences occur.
Aim: To sequence HHV8 in classic and AIDS associated KS in Okinawa.
Materials/Methods: Eight classic KS cases, one AIDS associated KS, five granuloma pyogenicum cases, two inflammatory pseudotumours, two Castleman’s disease cases, one angiosarcoma, and one primary effusion lymphoma (PEL) were studied. As a control, HHV8 positive cultured PEL cells (TY-1) were used. The presence of HHV8 sequences was evaluated by PCR and in situ hybridisation. PCR products were sequenced.
Results: There were no histological differences among KS resulting from the different virus genotypes. HHV8 was detected in all cases of KS, in one PEL, and one granuloma pyogenicum. Eight classic KS cases and one granuloma pyogenicum were infected with HHV8 genotype II/C (K1 region) or subtype C (ORF26 region), which had a five amino acid deletion at K1 VR2 region. An AIDS associated KS and a PEL were infected with type I/A virus.
Conclusion: In Okinawa, classic KS cases and one granuloma pyogenicum case were infected with HHV8 genotype II/C, also classified as subtype C. AIDS associated KS and PEL were infected with a different HHV8 (genotype I/A), similar to that found in the USA. In Okinawa, HHV8 infection is more than four times higher than in mainland Japan, resulting in many cases of KS because of HHV8 genotype II/C infection.
human herpesvirus 8 genotype; Kaposi’s sarcoma; granuloma pyogenicum; Castleman’s disease; primary effusion lymphoma
The ORF74 or vGCR gene encoded by Kaposi's sarcoma-associated herpesvirus (KSHV; also called human herpesvirus 8) has properties of a ligand-independent membrane receptor signaling protein with angiogenic properties that is predicted to play a key role in the biology of the virus. We have examined the expression of vGCR mRNA and protein in primary effusion lymphoma (PEL) cell lines, PEL and multicentric Castleman's disease (MCD) tumors, Kaposi's sarcoma lesions and infected endothelial cell cultures. The vGCR gene proved to be expressed in PEL cell lines as a large spliced bicistronic mRNA of 3.2 kb that also encompasses the upstream vOX2 (K14) gene. This mRNA species was induced strongly by phorbol ester (TPA) and sodium butyrate treatment in the BCBL-1 cell line, but only weakly in the HBL6 cell line, and was classified as a relatively late and low-abundance delayed early class lytic cycle gene product. A complex bipartite upstream lytic cycle promoter for this mRNA was nestled within the intron of the 5′-overlapping but oppositely oriented latent-state transcription unit for LANA1/vCYC-D/vFLIP and responded strongly to both TPA induction and cotransfection with the KSHV RNA transactivator protein (RTA or ORF50) in transient reporter gene assays. A vGCR protein product of 45 kDa that readily dimerized was detected by Western blotting and in vitro translation and was localized in a cytoplasmic and membrane pattern in DNA-transfected Vero and 293T cells or adenovirus vGCR-transduced dermal microvascular endothelial cells (DMVEC) as detected by indirect immunofluorescence assay (IFA) and immunohistochemistry with a specific rabbit anti-vGCR antibody. Similarly, a subfraction of KSHV-positive cultured PEL cells and of KSHV (JSC-1) persistently infected DMVEC cells displayed cytoplasmic vGCR protein expression, but only after TPA or spontaneous lytic cycle induction, respectively. The vGCR protein was also detectable by immunohistochemical staining in a small fraction (0.5 to 3%) of the cells in PEL and MCD tumor and nodular Kaposi's sarcoma lesion specimens that were apparently undergoing lytic cycle expression. These properties are difficult to reconcile with the vGCR protein's playing a direct role in spindle cell proliferation, transformation, or latency, but could be compatible with proposed contributions to angiogenesis via downstream paracrine effects. The ability of vGCR to transactivate expression of both several KSHV promoter-driven luciferase (LUC) reporter genes and an NFκB motif containing the chloramphenicol acetyltransferase (CAT) reporter gene may also suggest an unexpected regulatory role in viral gene expression.
Childhood multicentric Castleman disease (MCD) is a rare and unexplained lymphoproliferative disorder. We report a human herpesvirus-8 (HHV-8)-infected child, born to consanguineous Comorian parents, who displayed isolated MCD in the absence of any known immunodeficiency. We also systematically review the clinical features of the 32 children previously reported with isolated and unexplained MCD. The characteristics of this patient and the geographic areas of origin of most previous cases suggest that pediatric MCD is associated with HHV-8 infection. Moreover, as previously suggested for Kaposi sarcoma, MCD in childhood may result from inborn errors of immunity to HHV-8 infection.
Children; human herpes virus 8; multicentric Castleman disease; systematic review
Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), discovered in 1994, is a human rhadinovirus (gamma-2 herpesvirus). Unlike other human herpesviruses (herpes simplex virus, Epstein-Barr virus, varicella-zoster virus, cytomegalovirus, HHV-6, and HHV-7), it is not widespread in the general population and has many unique proteins. HHV-8 is strongly associated with all subtypes of Kaposi's sarcoma (KS), multicentric Castleman's disease, and a rare form of B-cell lymphoma, primary effusion lymphoma. In addition, HHV-8 DNA sequences have been found in association with other diseases, but the role of the virus in these diseases is largely unconfirmed and remains controversial. The seroprevalence of HHV-8, based on detection of latent and lytic proteins, is 2 to 5% in healthy donors except in certain geographic areas where the virus is endemic, 80 to 95% in classic KS patients, and 40 to 50% in HIV-1 patients without KS. This virus can be transmitted both sexually and through body fluids (e.g., saliva and blood). HHV-8 is a transforming virus, as evidenced by its presence in human malignancies, by the in vitro transforming properties of several of its viral genes, and by its ability to transform some primary cells in culture. It is not, however, sufficient for transformation, and other cofactors such as immunosuppressive cytokines are involved in the development of HHV-8-associated malignancies. In this article, we review the biology, molecular virology, epidemiology, transmission, detection methods, pathogenesis, and antiviral therapy of this newly discovered human herpesvirus.
Background: Kaposi sarcoma associated herpesvirus (KSHV)/human herpesvirus 8 (HHV-8) associated lymphomas, which often develop in human immunodeficiency virus (HIV) infected patients with advanced AIDS, present predominantly as primary effusion lymphoma (PEL) or, less frequently, as “solid” extracavitary based lymphomas, associated with serous effusions. These last lymphomas, also called “solid PEL”, have been reported before the development of an effusion lymphoma and after resolution of PEL. Interestingly, KSHV/HHV-8 associated lymphomas that present as solid or extracavitary based lesions in HIV seropositive patients without serous effusions have been reported recently.
Methods/Results: This paper provides evidence for the existence of a previously undescribed KSHV/HHV-8 associated lymphoma in HIV seronegative patients without serous effusions. These lymphomas exhibit a predilection for the lymph nodes and display anaplastic large cell morphology. These tumours were completely devoid of common cell type specific antigens, including epithelial and melanocytic cell markers. B and T cell associated antigens and other commonly used lymphoid markers were absent or weakly demonstrable in a fraction of the tumour cells. Conversely, immunohistochemical studies showed strong immunostaining with plasma cell reactive antibodies.
Conclusions: Analysis of viral infection and immunohistological studies are of primary importance to define this lymph node based KSHV/HHV-8 associated lymphoma with anaplastic large cell morphology and plasmablastic immunophenotype occurring in HIV seronegative patients without serous effusions.
lymphoma; KSHV/HHV8 associated lymphomas; anaplastic large cell lymphoma; plasmablastic lymphoma; diffuse large B cell lymphoma
Kaposi sarcoma‐associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV8), is a recent addition to the list of human viruses that are directly associated with lymphoproliferative disorders. KSHV was first shown to be involved in multicentric Castleman disease and primary effusion lymphoma (PEL). Subsequently, the virus was identified in solid lymphomas, often of extranodal sites, with morphological and immunophenotypic characteristics similar to those of PEL, and in other lymphoproliferative disorders with heterogeneous clinicopathological presentations. The recent advances in our understanding of the histology, immunophenotype and pathogenesis of these KSHV‐associated lymphoproliferative disorders are reviewed.
Kaposi sarcoma (KS), multicentric Castleman's disease (MCD), and plasmablastic microlymphoma, are all linked to human herpesvirus-8 (HHV-8) infection and HIV-induced immunodeficiency. Herein, we describe the case of a Kenyan man diagnosed with HIV in 2000. He deferred highly active antiretroviral therapy (HAART) and remained in good health until his CD4+ count declined in 2006. He was hospitalized with bacterial pneumonia in 2008, after which he agreed to take HAART but did so sporadically. In 2010, he was hospitalized with fever, lymphadenopathy, pancytopenia, and an elevated HHV-8 viral load. A lymph node biopsy showed findings consistent with KS, MCD, and plasmablastic microlymphoma. Eight months after starting liposomal doxorubicin, Rituximab, and a new HAART regimen, he has improved clinically, and his HIV and HHV-8 viral loads are suppressed. These three conditions, found in the same lymph node, underscore the inflammatory and malignant potential of HHV-8, particularly in the milieu of HIV-induced immunodeficiency.
Human herpesvirus 8 (HHV-8) is the etiological agent of Kaposi's sarcoma, primary effusion lymphoma, and some forms of multicentric Castleman's disease. Although latent HHV-8 DNA can be detected in B cells from persons with these cancers, there is little information on the replication of HHV-8 in B cells. Indeed, B cells are relatively resistant to HHV-8 infection in vitro. We have recently shown that DC-SIGN, a C-type lectin first identified on dendritic cells (DC), is an entry receptor for HHV-8 on DC and macrophages. We have also demonstrated previously that B lymphocytes from peripheral blood and tonsils express DC-SIGN and that this expression increases after B-cell activation. Here we show that activated blood and tonsillar B cells can be productively infected with HHV-8, as measured by an increase in viral DNA, the expression of viral lytic and latency proteins, and the production of infectious virus. The infection of B cells with HHV-8 was blocked by the pretreatment of the cells with antibody specific for DC-SIGN or with mannan but not antibody specific for xCT, a cystine/glutamate exchange transporter that has been implicated in HHV-8 fusion to cells. The infection of B cells with HHV-8 resulted in increased expression of DC-SIGN and a decrease in the expression of CD20 and major histocompatibility complex class I. HHV-8 could also infect and replicate in B-cell lines transduced to express full-length DC-SIGN but not in B-cell lines transduced to express DC-SIGN lacking the transmembrane domain, demonstrating that the entry of HHV-8 into B cells is related to DC-SIGN-mediated endocytosis. The role of endocytosis in viral entry into activated B cells was confirmed by blocking HHV-8 infection with endocytic pathway inhibitors. Thus, the expression of DC-SIGN is essential for productive HHV-8 infection of and replication in B cells.
Kaposi sarcoma–associated herpesvirus (KSHV) encodes 12 pre-microRNAs that yield 25 mature microRNAs. We previously reported phylogenetic analysis of the microRNA-coding region of KSHV from Kaposi sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman disease (MCD) patients. We observed a high level of conservation for most sequences but also a divergent cluster of 5 KSHV sequences, including 2 from MCD patients.
KSHV microRNA sequences from 23 MCD patients and 7 patients with a newly described KSHV-associated inflammatory cytokine syndrome (KICS) were examined by amplification, cloning, and sequencing of a 646-bp fragment of K12/T0.7 encoding microRNA-K12-10 and microRNA-K12-12 and a 2.8-kbp fragment containing the remaining 10 pre-microRNAs.
Phylogenetic analysis showed a distinct variant cluster consisting exclusively of MCD and KICS patients in all trees. Pearson χ2 analysis revealed that 40 single-nucleotide polymorphisms (SNPs) at various loci were significantly associated with MCD and KICS risk. Cluster analysis of these SNPs generated several combinations of 3 SNPs as putative indicators of MCD and KICS risk.
These findings show that MCD and KICS patients frequently have unusual KSHV microRNA sequences and suggest an association between the observed sequence variation and risk of MCD and KICS.
Kaposi's sarcoma is a multifocal lesion that is reported to be greatly influenced by cytokines such as interleukin-6 (IL-6) and oncostatin M. DNA sequences of a novel human gammaherpesvirus, termed human herpesvirus 8 (HHV-8) or Kaposi sarcoma-associated herpesvirus, have been identified in all epidemiological forms of Kaposi's sarcoma with high frequency. The presence of HHV-8 DNA is also clearly associated with certain B-cell lymphomas (body cavity-based lymphomas) and multicentric Castleman's disease. Sequence analysis of a 17-kb fragment revealed that adjacent to a block of conserved herpesvirus genes (major DNA-binding protein, glycoprotein B, and DNA polymerase), the genome of HHV-8 encodes structural homolog of IL-6. This cytokine is involved not only in the pathogenesis of Kaposi's sarcoma but also in certain B-cell lymphomas and multicentric Castleman's disease. The viral counterpart of IL-6 (vIL-6) has conserved important features such as cysteine residues involved in disulfide bridging or an amino-terminal signal peptide. Most notably, the region known to be involved in receptor binding is highly conserved in vIL-6. This conservation of essential features and the remarkable overlap between diseases associated with HHV-8 and diseases associated with IL-6 disregulation clearly suggest that vIL-6 is involved in HHV-8 pathogenesis.
Human herpesvirus 8 (HHV-8), or Kaposi's sarcoma-associated herpesvirus, is a gammaherpesvirus first detected in Kaposi's sarcoma tumor cells and subsequently in primary effusion lymphoma (PEL) tumor cells and peripheral blood mononuclear cells from PEL patients. PEL has been recognized as an individual nosologic entity based on its distinctive features and consistent association with HHV-8 infection. PEL is an unusual form of body cavity-based B-cell lymphoma (BCBL). It occurs predominantly in human immunodeficiency virus (HIV)-positive patients but occasionally also in elderly HIV-negative patients. We describe a case of PEL, with ascites, bilateral pleural effusions, and a small axillary lymphadenopathy, in a 72-year-old HIV-negative man. PCR performed on a lymph node specimen and in liquid effusion was positive for HHV-8 and negative for Epstein-Barr virus. The immunophenotype of the neoplastic cells was B CD19+ CD20+ CD22+ with coexpression of CD10 and CD23 and with clonal kappa light chain rearrangement. The patient was treated with Rituximab, a chimeric (human-mouse) anti-CD20 monoclonal antibody. Thirteen months later, the patient continued in clinical remission. This is the first report of an HHV-8-associated BCBL in an HIV-negative patient in Argentina.
Human herpesvirus-8 (HHV-8) is the causative agent of Kaposi's sarcoma and is associated with the angioproliferative disorders primary effusion lymphoma and multicentric Castleman's disease. Evidence of HHV-8 infection within the pulmonary vasculature of patients with idiopathic pulmonary arterial hypertension (IPAH) has been described. We hypothesize that HHV-8 infection of pulmonary microvascular endothelial cells results in an apoptotic-resistant phenotype characteristic of severe pulmonary arterial hypertension. Our objective was to investigate the ability of HHV-8 to infect human pulmonary microvascular endothelial cells in vitro and characterize the phenotypic effect of this infection. Human pulmonary microvascular endothelial cells were exposed to HHV-8 using two methods (direct virus and co-culture technique). The presence of lytic and latent infection was confirmed. Changes in endothelial cell gene and protein expression and effects on cellular apoptosis were measured. HHV-8 can both lytically and latently infect primary human pulmonary microvascular endothelial cells in vitro. HHV-8 infection results in significant changes in gene expression, including alterations of pathways important to cellular apoptosis. HHV-8 infection also alters expression of genes integral to the bone morphogenic protein pathway, including down-regulation of bone morphogenic protein-4. Other genes previously implicated in the development of PAH are affected by HHV-8 infection, and cells infected with HHV-8 are resistant to apoptosis.
HHV-8; endothelial cells; pulmonary hypertension