Immunodeficiency and IL-6 production by peripheral blood monocytes in multicentric Castleman's disease

The lymph node transcriptome of unicentric and idiopathic multicentric Castleman disease

Castleman disease is a polyclonal lymphoproliferative disorder characterized by unicentric or multicentric lymphadenopathy with characteristic histomorphological features, in addition to variable inflammatory symptomatology. The molecular mechanisms and etiologies of unicentric Castleman disease (UCD) and idiopathic multicentric Castleman disease (iMCD) are poorly understood, and identification of targetable disease mediators remains an unmet clinical need. We performed whole exome sequencing on lymph node biopsies from patients with UCD and iMCD and compared the transcriptomic profiles to that of benign control lymph nodes. We identified significantly upregulated genes in UCD (n=443), iMCD (n=316) or both disease subtypes (n=51) and downregulated genes in UCD (n=321), iMCD (n=105) or both (n=10). The transcriptomes of UCD and iMCD showed enrichment and upregulation of elements of the complement cascade. By immunohistochemistry, C4d deposits indicative of complement activation were found to be present in UCD and iMCD, mostly within abnormally regressed germinal centers, but also in association with plasma cell clusters, endothelial cells and stroma cell proliferations. Other enriched gene sets included collagen organization, S1P3 pathway and VEGFR pathway in UCD; and humoral response, oxidative phosphorylation and proteosome in iMCD. Analysis of cytokine transcripts showed upregulation of CXCL13 but not IL6 in UCD and iMCD. Among angiogenic mediators, the VEGFR1 ligand placental growth factor (PGF) was upregulated in both disease subtypes. We hereby report for the first time the whole lymph node transcriptomes of UCD and iMCD, underscoring findings that could aid in the discovery of targetable disease mediators.

Transcriptome and unique cytokine microenvironment of Castleman disease

Castleman disease (CD) represents a group of rare, heterogeneous and poorly understood disorders that share characteristic histopathological features. Unicentric CD (UCD) typically involves a single enlarged lymph node whereas multicentric CD (MCD) involves multiple lymph node stations. To understand the cellular basis of CD, we undertook a multi-platform analysis using targeted RNA sequencing, RNA in-situ hybridization (ISH), and adaptive immune receptor rearrangements (AIRR) profiling of archived tissue from 26 UCD, 14 MCD, and 31 non-CD reactive controls. UCD showed differential expression and upregulation of follicular dendritic cell markers (CXCL13, clusterin), angiogenesis factors (LPL, DLL4), extracellular matrix remodeling factors (TGFβ, SKIL, LOXL1, IL-1β, ADAM33, CLEC4A), complement components (C3, CR2) and germinal center activation markers (ZDHHC2 and BLK) compared to controls. MCD showed upregulation of IL-6 (IL-6ST, OSMR and LIFR), IL-2, plasma cell differentiation (XBP1), FDC marker (CXCL13, clusterin), fibroblastic reticular cell cytokine (CCL21), angiogenesis factor (VEGF), and mTORC1 pathway genes compared to UCD and controls. ISH studies demonstrated that VEGF was increased in the follicular dendritic cell-predominant atretic follicles and the interfollicular macrophages of MCD compared to UCD and controls. IL-6 expression was higher along interfollicular vasculature-associated cells of MCD. Immune repertoire analysis revealed oligoclonal expansions of T-cell populations in MCD cases (2/6) and UCD cases (1/9) that are consistent with antigen-driven T cell activation. The findings highlight the unique genes, pathways and cell types involved in UCD and MCD. We identify potential novel targets in CD that may be harnessed for therapeutics.

IL-6 expression helps distinguish Castleman's disease from IgG4-related disease in the lung

Background

It is difficult to distinguish between multicentric Castleman’s disease (MCD) and IgG4-related lung disease (IgG4-LD), an IgG4-related disease (IgG4-RD) in the lung.

Methods

We focused on IL-6, which is elevated in MCD, to distinguish between MCD and IgG4-LD by RNAscope, a highly sensitive RNA in situ method. Six cases of MCD and four cases of IgG4-LD were selected.

Results

In all cases of MCD and IgG4-LD, 10 or more IgG4-positive cells were found in one high-power field. All MCD cases were inconsistent with the pathological IgG4-related comprehensive diagnostic criteria, but 2 of 6 cases had an IgG4/IgG ratio greater than 40%. In all IgG4-LD cases, histological features were consistent with the pathological IgG4-RD comprehensive diagnostic criteria. IL-6 expression was observed in all MCD and IgG4-LD cases except for one IgG4-LD biopsy. IL-6-expressing cells were mainly identified in the stroma. Sites of IL-6 expression were not characteristic and were sparse. IL-6 expression tended to be higher in MCD compared with IgG4-LD. A positive correlation was found between the IL-6 H-score and serum IL-6 level.

Conclusion

Differences in IL-6 expression may help distinguish between MCD and IgG4-LD. In addition, the presence of high IL-6 levels may help elucidate the pathological mechanisms of IgG4-LD.

Novel Functions and Virus-Host Interactions Implicated in Pathogenesis and Replication of Human Herpesvirus 8

Human herpesvirus 8 (HHV-8) is classified as a γ2-herpesvirus and is related to Epstein-Barr virus (EBV), a γ1-herpesvirus. One important aspect of the γ-herpesviruses is their association with neoplasia, either naturally or in animal model systems. HHV-8 is associated with B-cell-derived primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD), endothelial-derived Kaposi's sarcoma (KS), and KSHV inflammatory cytokine syndrome (KICS). EBV is also associated with a number of B-cell malignancies, such as Burkitt's lymphoma, Hodgkin's lymphoma, and posttransplant lymphoproliferative disease, in addition to epithelial nasopharyngeal and gastric carcinomas. Despite the similarities between these viruses and their associated malignancies, the particular protein functions and activities involved in key aspects of virus biology and neoplastic transformation appear to be quite distinct. Indeed, HHV-8 specifies a number of proteins for which counterparts had not previously been identified in EBV, other herpesviruses, or even viruses in general, and these proteins are believed to play vital functions in virus biology and to be involved centrally in viral pathogenesis. Additionally, a set of microRNAs encoded by HHV-8 appears to modulate the expression of multiple host proteins to provide conditions conductive to virus persistence within the host and possibly contributing to HHV-8-induced neoplasia. Here, we review the molecular biology underlying these novel virus-host interactions and their potential roles in both virus biology and virus-associated disease.

Idiopathic multicentric Castleman's disease: a clinicopathologic study in comparison with IgG4-related disease

The present study aimed to compare clinicopathologic features between idiopathic multicentric Castleman's disease (n=22) and IgG4-related disease (n=26). Histology was analyzed using lymph node and lung biopsies. The expression of IL-6 mRNA in tissue was also examined by in situ hybridization and real-time PCR. Patients with idiopathic multicentric Castleman's disease were significantly younger than those with IgG4-related disease (p<0.001). Splenomegaly was observed in only idiopathic multicentric Castleman's disease (p=0.002), while pancreatitis and sialo-dacryoadenitis were restricted to IgG4-related disease (both p<0.001). Serum IgG4 concentrations were commonly elevated at >135 mg/dL in both groups (p=0.270). However, the IgG4/IgG ratio in IgG4-related disease was significantly higher than that in Castleman's disease (p<0.001). Histologically, sheet-like plasmacytosis was highly characteristic of idiopathic multicentric Castleman's disease (p<0.001), while plasmacytic infiltration in IgG4-related disease was always associated with intervening lymphocytes. Similar to laboratory findings, the IgG4/IgG-positive plasma cell ratio, but not the IgG4-positive cell count, was significantly higher in IgG4-related disease (p=0.002). Amyloid-like hyalinized fibrosis was found in 6/8 lung biopsies (75%) of Castleman's disease. The over-expression of IL-6 mRNA was not confirmed in tissue samples of Castleman's disease by either in situ hybridization or quantitative real-time PCR. In conclusion, useful data for a differential diagnosis appear to be age, affected organs, the serum IgG4/IgG ratio, sheet-like plasmacytosis in biopsies, and the IgG4/IgG-positive cell ratio on immunostaining. Since IL-6 was not over-expressed in tissue of idiopathic multicentric Castleman's disease, IL-6 may be produced outside the affected organs, and circulating IL-6 may lead to lymphoplasmacytosis at nodal and extranodal sites.

Treatment of Idiopathic Castleman Disease

Important progress has been made in the treatment of idiopathic multicentric Castleman disease (iMCD) with the introduction of interleukin-6 targeting monoclonal antibodies. This article describes the clinical results obtained with different treatment modalities and uses this evidence to provide treatment guidelines for the practicing clinician. Much is still to be learned about the pathophysiology of iMCD and further research is urgently needed to develop novel and curative treatment approaches for all patients.

Clinical and pathological characteristics of HIV- and HHV-8-negative Castleman disease

Castleman disease (CD) comprises 3 poorly understood lymphoproliferative variants sharing several common histopathological features. Unicentric CD (UCD) is localized to a single region of lymph nodes. Multicentric CD (MCD) manifests with systemic inflammatory symptoms and organ dysfunction due to cytokine dysregulation and involves multiple lymph node regions. Human herpesvirus 8 (HHV-8) causes MCD (HHV-8-associated MCD) in immunocompromised individuals, such as HIV-infected patients. However, >50% of MCD cases are HIV and HHV-8 negative (defined as idiopathic [iMCD]). The clinical and biological behavior of CD remains poorly elucidated. Here, we analyzed the clinicopathologic features of 74 patients (43 with UCD and 31 with iMCD) and therapeutic response of 96 patients (43 with UCD and 53 with iMCD) with HIV-/HHV-8-negative CD compared with 51 HIV-/HHV-8-positive patients. Systemic inflammatory symptoms and elevated inflammatory factors were more common in iMCD patients than UCD patients. Abnormal bone marrow features were more frequent in iMCD (77.0%) than UCD (45%); the most frequent was plasmacytosis, which was seen in 3% to 30.4% of marrow cells. In the lymph nodes, higher numbers of CD3⁺ lymphocytes (median, 58.88 ± 20.57) and lower frequency of CD19⁺/CD5⁺ (median, 5.88 ± 6.52) were observed in iMCD patients compared with UCD patients (median CD3⁺ cells, 43.19 ± 17.37; median CD19⁺/CD5⁺ cells, 17.37 ± 15.80). Complete surgical resection is a better option for patients with UCD. Siltuximab had a greater proportion of complete responses and longer progression-free survival (PFS) for iMCD than rituximab. Centricity, histopathological type, and anemia significantly impacted PFS. This study reveals that CD represents a heterogeneous group of diseases with differential immunophenotypic profiling and treatment response.

Idiopathic multicentric Castleman's disease: a systematic literature review

BACKGROUND

Multicentric Castleman's disease describes a group of poorly understood lymphoproliferative disorders driven by proinflammatory hypercytokinaemia. Patients have heterogeneous clinical features, characteristic lymph node histopathology, and often deadly multiple organ dysfunction. Human herpesvirus 8 (HHV8) causes multicentric Castleman's disease in immunosuppressed patients. The cause of HHV8-negative multicentric Castleman's disease is idiopathic; such cases are called idiopathic multicentric Castleman's disease. An absence of centralised information about idiopathic multicentric Castleman's disease represents a major challenge for clinicians and researchers. We aimed to characterise clinical features of, treatments for, and outcomes of idiopathic multicentric Castleman's disease.

METHODS

We did a systematic literature review and searched PubMed, the Cochrane database, and ClinicalTrials.gov from January, 1995, with keywords including "Castleman's disease" and "giant lymph node hyperplasia". Inclusion criteria were pathology-confirmed Castleman's disease in multiple nodes and minimum clinical and treatment information on individual patients. Patients with HHV8 or HIV infection or diseases known to cause Castleman-like histopathology were excluded.

FINDINGS

Our search identified 626 (33%) patients with HHV8-negative multicentric Castleman's disease from 1923 cases of multicentric Castleman's disease. 128 patients with idiopathic multicentric Castleman's disease met all inclusion criteria for the systematic review. Furthermore, aggregated data for 127 patients with idiopathic multicentric Castleman's disease were presented from clinical trials, which were excluded from primary analyses because patient-level data were not available. Clinical features of idiopathic multicentric Castleman's disease included multicentric lymphadenopathy (128/128), anaemia (79/91), elevated C-reactive protein (65/79), hypergammaglobulinaemia (63/82), hypoalbuminaemia (57/63), elevated interleukin 6 (57/63), hepatomegaly or splenomegaly (52/67), fever (33/64), oedema, ascites, anasarca, or a combination (29/37), elevated soluble interleukin 2 receptor (20/21), and elevated VEGF (16/20). First-line treatments for idiopathic multicentric Castleman's disease included corticosteroids (47/128 [37%]), cytotoxic chemotherapy (47/128 [37%]), and anti-interleukin 6 therapy (11/128 [9%]). 49 (42%) of 116 patients failed first-line therapy, 2-year survival was 88% (95% CI 81-95; 114 total patients, 12 events, 36 censored), and 27 (22%) of 121 patients died by the end of their observed follow-up (median 29 months [IQR 12-50]). 24 (19%) of 128 patients with idiopathic multicentric Castleman's disease had a diagnosis of a separate malignant disease, significantly higher than the frequency expected in age-matched controls (6%).

INTERPRETATION

Our systematic review provides comprehensive information about clinical features, treatment, and outcomes of idiopathic multicentric Castleman's disease, which accounts for at least 33% of all cases of multicentric Castleman's disease. Our findings will assist with prompt recognition, diagnostic criteria development, and effective management of the disease.

FUNDING

None.

HHV-8-negative, idiopathic multicentric Castleman disease: novel insights into biology, pathogenesis, and therapy

Multicentric Castleman's disease (MCD) describes a heterogeneous group of disorders involving proliferation of morphologically benign lymphocytes due to excessive proinflammatory hypercytokinemia, most notably of interleukin-6. Patients demonstrate intense episodes of systemic inflammatory symptoms, polyclonal lymphocyte and plasma cell proliferation, autoimmune manifestations, and organ system impairment. Human herpes virus-8 (HHV-8) drives the hypercytokinemia in all HIV-positive patients and some HIV-negative patients. There is also a group of HIV-negative and HHV-8-negative patients with unknown etiology and pathophysiology, which we propose referring to as idiopathic MCD (iMCD). Here, we synthesize what is known about iMCD pathogenesis, present a new subclassification system, and propose a model of iMCD pathogenesis. MCD should be subdivided into HHV-8-associated MCD and HHV-8-negative MCD or iMCD. The lymphocyte proliferation, histopathology, and systemic features in iMCD are secondary to hypercytokinemia, which can occur with several other diseases. We propose that 1 or more of the following 3 candidate processes may drive iMCD hypercytokinemia: systemic inflammatory disease mechanisms via autoantibodies or inflammatory gene mutations, paraneoplastic syndrome mechanisms via ectopic cytokine secretion, and/or a non-HHV-8 virus. Urgent priorities include elucidating the process driving iMCD hypercytokinemia, identifying the hypercytokine-secreting cell, developing consensus criteria for diagnosis, and building a patient registry to track cases.

Molecular biology of human herpesvirus 8: novel functions and virus-host interactions implicated in viral pathogenesis and replication

Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), is the second identified human gammaherpesvirus. Like its relative Epstein-Barr virus, HHV-8 is linked to B-cell tumors, specifically primary effusion lymphoma and multicentric Castleman's disease, in addition to endothelial-derived KS. HHV-8 is unusual in its possession of a plethora of "accessory" genes and encoded proteins in addition to the core, conserved herpesvirus and gammaherpesvirus genes that are necessary for basic biological functions of these viruses. The HHV-8 accessory proteins specify not only activities deducible from their cellular protein homologies but also novel, unsuspected activities that have revealed new mechanisms of virus-host interaction that serve virus replication or latency and may contribute to the development and progression of virus-associated neoplasia. These proteins include viral interleukin-6 (vIL-6), viral chemokines (vCCLs), viral G protein-coupled receptor (vGPCR), viral interferon regulatory factors (vIRFs), and viral antiapoptotic proteins homologous to FLICE (FADD-like IL-1β converting enzyme)-inhibitory protein (FLIP) and survivin. Other HHV-8 proteins, such as signaling membrane receptors encoded by open reading frames K1 and K15, also interact with host mechanisms in unique ways and have been implicated in viral pathogenesis. Additionally, a set of micro-RNAs encoded by HHV-8 appear to modulate expression of multiple host proteins to provide conditions conducive to virus persistence within the host and could also contribute to HHV-8-induced neoplasia. Here, we review the molecular biology underlying these novel virus-host interactions and their potential roles in both virus biology and virus-associated disease.

Human herpesvirus 8-encoded cytokines

Human herpesvirus (HHV)-8, also called Kaposi's sarcoma-associated herpesvirus, was discovered in 1994 and was rapidly sequenced, revealing several unique and surprising features of its genetic makeup. Among these discoveries was the identification of the first viral homolog of IL-6 and three CC/beta-chemokine ligands (viral CCL-1, -2 and -3), not previously found in gamma-herpesviruses. Viral IL-6 was immediately recognized as a potential contributor to HHV-8 pathogenesis, specifically endothelial-derived Kaposi's sarcoma and the B-cell malignancy multicentric Castleman's disease with which IL-6, a proangiogenic and B-cell growth factor, had previously been implicated. The roles of the viral chemokines were speculated to involve immune evasion; however, like viral IL-6, the viral chemokines have the potential to contribute to pathogenesis through their shared angiogenic activities, known to be important for Kaposi's sarcoma and HHV-8-associated primary effusion lymphoma, and also via direct prosurvival activities. This article will discuss the molecular properties, activities and functions of viral IL-6 and the viral CCLs, proteins that could provide appropriate targets for antiviral and therapeutic strategies.

Human gammaherpesvirus cytokines and chemokine receptors

Most herpesviruses of the beta and gamma subfamilies encode homologues of cytokines and chemokine receptor- related G protein-coupled receptors (GPCRs). The roles of these proteins during normal virus replication in the infected host have not been defined in most cases, but the available data and extrapolation from what is known about the properties and functions of their cellular counterparts indicate that they play primary roles in immune evasion or in activating cellular signaling cascades that enhance virus productive replication. Cytokines and chemokine receptors specified by the two human gammaherpesviruses, human herpesvirus 8 (HHV-8) and Epstein-Barr virus (EBV), are the subject of this review. HHV-8 encodes three chemokines, a homologue of interleukin-6, and a CXCR2-related chemokine receptor, while EBV encodes a distinct GPCR and a homologue of interleukin-10. While these viral cytokines and chemokine receptors no doubt contribute to virus biology, their properties indicate that they may also be involved in virus-induced neoplasia. This review discusses the properties, functions, and likely roles of HHV-8 and EBV cytokines and chemokine receptors in relation to both virus biology and virus-associated disease.

The therapeutic potential of interleukin-6 hyperagonists and antagonists

Interleukin-6 (IL-6) is a 4-helical protein that binds to a specific IL-6 receptor on target cells and to two molecules of the promiscuous signal transducing protein, glycoprotein 130 (gp130). Structure-function analysis has led to the definition of molecular contacts between IL-6 and its receptor subunits. This knowledge has led to the design of competitive antagonistic proteins that retain their receptor binding capability, but fail to stimulate one or both gp130 proteins; the properties of such recombinant antagonistic proteins are compared with traditional neutralising monoclonal antibodies targeted at IL-6 or receptor subunits. Furthermore, several strategies have been employed to construct molecules with increased bioactivity. Possible therapeutic applications in putative IL-6 dependent haematologic disorders, e.g., Castleman's disease (CD), POEMS syndrome, multiple myeloma, and bone diseases, e.g., Paget's disease, osteoporosis, are outlined. IL-6 antagonists could also, in theory, suppress inflammatory activity in rheumatic and autoimmune diseases and could prevent secondary amyloidosis. This principle may prove advantageous in myocardial infarction (MI) and unstable angina pectoris. More generally, IL-6 antagonists could improve the wasting and microcytic anaemia of chronic diseases. IL-6 antagonists might slow down development of mesangio-proliferative glomerulonephritis (MPGN). Hyperagonistic variants of IL-6 have a potential use in the ex vivo expansion of haematopoietic progenitor cells and as thrombopoietic agents. They might well be the first drugs to aid liver regeneration in vivo.

Interleukin-6 (IL-6) expression and natural killer (NK) cell dysfunction and anergy in heart failure

Immune dysfunction has been postulated to play a role in the pathophysiology of chronic heart failure. We examined the relation between interleukin-6 (IL-6) production and natural killer (NK) cell dysfunction in patients with chronic heart failure. Sera and peripheral blood mononuclear cells (PBMCs) were collected from 82 patients with advanced heart failure. Levels of circulating NK cells and T cells were determined by flow cytometry. NK cell function was measured by standard cytotoxicity assays. IL-6 in supernatants of PBMC cultured in vitro was quantitated by an enzyme-linked immunosorbent assay. The levels of circulating NK cells were lower in patients with heart failure than in normal controls (p = 0.0037). NK cells from patients with heart failure also exhibited impaired cytolytic functions in the absence of stimuli and in response to IL-2 and IL-12 (p <0.0001 for all conditions). PBMCs from patients with heart failure produced higher levels of IL-6 in response to a T-cell stimulus than did PBMCs from healthy controls (p = 0.0012). The level of IL-6 produced by unstimulated PBMCs in patients with heart failure correlated with NK cell cytolytic impairment (p = 0.0012). These results demonstrated that PBMCs are a source of IL-6 in patients with heart failure. Production of IL-6 by PBMCs correlated with NK cell anergy to other cytokines that use signal transduction pathways that may be regulated by IL-6. These results support a model of cytokine-induced anergy in conditions that result in high systemic levels of IL-6.

Human herpesvirus-8-encoded signalling ligands and receptors

Analysis of the genome of human herpesvirus 8 (HHV-8) led to the discovery of several novel genes, unique among the characterized gammaherpesviruses. These include cytokines (interleukin-6 and chemokine homologues), two putative signal-transducing transmembrane proteins encoded by genes K1 and K15 at the genome termini, and an OX-2 (CD200) receptor homologue that had not previously been identified in a gammaherpesvirus. HHV-8 also specifies a diverged version of the gammaherpesvirus-conserved G protein-coupled chemokine receptor (vGCR) and a latently expressed protein unique to HHV-8 specified by open reading frame (ORF) K12. These cytokine and receptor homologues mediate signal transduction or modulate the activities of other endogenous cytokines and receptors to enhance viral productive replication, regulate latent-lytic switching, evade host attack, or mediate cell survival. The viral signalling ligands and receptors are also potential contributors to virus-associated diseases, Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease, and so represent potentially important targets for therapeutic and antiviral drugs. Understanding these proteins' modes of action and functions in viral biology and disease is therefore of considerable importance, and the subject of this review.

The molecular pathology of Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) is the eighth and most recently identified human herpesvirus (HHV-8). KSHV was discovered in 1994 by Chang et al. who used representational difference analysis to search for DNA sequences present in AIDS-associated KS but not in adjacent normal skin [1]. The virus has since been shown to be specifically associated with all forms of this disease and has fulfilled all of Hill's criteria for causation (reviewed in ). KSHV is also found in all cases of primary effusion lymphoma and in a plasmablastic variant of multicentric Castleman's disease. Over the last few years a wealth of data has been gained on the role of KSHV genes during infection. This review is an attempt to assemble this information into a more complete picture of how KSHV may cause disease.

[Castleman's disease in patients infected with HIV]

PURPOSE

Castleman's disease is a polyclonal lymphoplasmacytic and vascular proliferation prominant in lymphoid tissues. It is associated with lymph node enlargement, hepatosplenomegaly and fever. This manifestations could be secondary to hyperproduction of interleukin 6. The prognosis is poor. The opportunistic infections which are characteristic of severe HIV infection worsen the prognosis. Prolonged monochemotherapy with vinblastine or etoposide can control Castleman's disease.

CURRENT KNOWLEDGE AND KEY POINTS

Recent advances in human herpesvirus 8 (HHV8) knowledge and its predominance in the forms which are linked to the HIV seropositivity have partly explained the clinical manifestations of Castleman's disease. Indeed, HHV8 produce an homologous interleukin 6, the vIL-6, responsible for lymphoplasmacytic proliferation. The presence of other homologues of human cytokines produced by HHV8 could contribute to lymphoplasmacytosis and to endothelial proliferation.

FUTURE AND PROSPECTS

Taking into account this viral origin, alpha interferon could be an alternative in forms which are less progressive. However, antiviral therapy against HHV8 or HIV and the immunitary restoration do not have any influence on the evolution of Castleman's disease, contrary to opportunistic infections.

Evolutionary aspects of oncogenic herpesviruses

Several of the gamma-herpesviruses are known to have cellular transforming and oncogenic properties. The genomes of eight distinct gamma-herpesviruses have been sequenced, and the resulting database of information has enabled the identification of genetic similarities and differences between evolutionarily closely related and distant viruses of the subfamily and between the gamma-herpesviruses and other members of the herpesvirus family. The recognition of coincident loci of genetic divergence between individual gamma-herpesviruses and the identification of novel genes and cellular gene homologues in these genomic regions has delineated a subset of genes that are likely to contribute to the unique biological properties of these viruses. These genes, together with gamma-herpesvirus conserved genes not found in viruses outside the family, might be responsible for virus specific pathogenicity and pathogenic effects, such as viral associated neoplasia, characteristic of the subfamily. The presence of the gamma-herpesvirus major divergent genomic loci and the apparent increased mutational frequencies of homologous genes (where they occur) within these regions, indicates that these loci possess particular features that drive genetic divergence. Whatever the mechanisms underlying this phenomenon, it potentially provides the basis for the relatively rapid adaptation and evolution of gamma-herpesviruses and the diversity of biological and pathogenic properties.

Increased expression of vascular endothelial growth factor (VEGF) in Castleman's disease: proposed pathomechanism of vascular proliferation in the affected lymph node

Castleman's disease is a lymphoproliferative disorder of unknown etiology characterized by enlarged hyperplastic lymph nodes with marked vascular proliferation. To evaluate the possible involvement of vascular endothelial growth factor (VEGF) in the pathogenesis of Castleman's disease, we studied VEGF expression in sera and lymph nodes from four patients with either the plasma-cell type or mixed type of Castleman's disease. Clinically, one patient had the multicentric type and the others the localized type. The VEGF levels of the sera and the supernatants of the cultured lymph nodes were higher than those of normal controls. VEGF was strongly expressed in plasma cells in the interfollicular region of the lymph nodes, but rarely in normal lymph nodes. The disregulated IL-6 gene expression is considered to be a primary event that could be related to the etiology of this disease. Recently, Kaposi's sarcoma virus/human herpes virus 8 (KSHV/HHV-8) has been reported to be associated with a subset of the multicentric type of Castleman's disease, and a viral homologue of IL-6 (vIL-6) encoded by KSHV/HHV-8 has been shown to induce VEGF expression. Human IL-6 produced in the affected lymph nodes of Castleman's disease may induce paracrine VEGF-production by plasma cells and vascular proliferation in the lymph node. The confirmation of the role of VEGF in the pathogenesis of Castleman's disease may provide a therapeutic strategy.

Human herpesvirus 8 interleukin-6 (vIL-6) signals through gp130 but has structural and receptor-binding properties distinct from those of human IL-6

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.

Human Herpesvirus 8 Infection in Patients With POEMS Syndrome–Associated Multicentric Castleman’s Disease

The polyneuropathy, organomegaly, endocrinopathy, M protein, skin changes (POEMS) syndrome is a rare multisystemic disorder associated with osteosclerotic myeloma and multicentric Castleman’s disease (MCD). Human herpesvirus type 8 (HHV-8) DNA sequences have been detected in lymph nodes of about 40% of human immunodeficiency virus (HIV)-negative patients with MCD, and in bone marrow stromal cells of patients with multiple myeloma. Considering these data, we investigated the presence of HHV-8 in 18 patients with POEMS syndrome (9 with MCD), by nested polymerase chain reaction (N-PCR) to detect DNA sequenses in various cells and tissues obtained by biopsy or at autopsy (13 patients, of whom 7 had MCD), and by an immunofluorescence assay to detect anti–HHV-8 IgG antibodies in blood (18 patients, of whom 9 had MCD). Detection of HHV-8 DNA was performed using three different N-PCR, targeting nonoverlapping regions in open reading frame (ORF) 25 and ORF26. Seven of 13 (54%) POEMS patients had HHV-8 DNA sequences in their tissues, as assessed by all three N-PCR, and 9 of 18 (50%) had circulating anti–HHV-8 antibodies. HHV-8 was mainly detected in the subset of POEMS patients with MCD (6 of 7 [85%] for DNA sequences; 7 of 9 [78%] for antibodies). The percentage of positive N-PCR was higher in lymph nodes than in bone marrow samples (P &lt; .02). Sequencing of amplicons showed a homogeneous restricted variability in the ORF26 region, characteristic of the minority subgroup B defined by Zong, and responsible for isoleucine and glycine substitutions at amino acid positions 134 and 167. These findings strongly suggest an association of HHV-8 infection with POEMS syndrome-associated MCD.

Human Herpesvirus 8 Infection in Patients With POEMS Syndrome–Associated Multicentric Castleman’s Disease

The polyneuropathy, organomegaly, endocrinopathy, M protein, skin changes (POEMS) syndrome is a rare multisystemic disorder associated with osteosclerotic myeloma and multicentric Castleman’s disease (MCD). Human herpesvirus type 8 (HHV-8) DNA sequences have been detected in lymph nodes of about 40% of human immunodeficiency virus (HIV)-negative patients with MCD, and in bone marrow stromal cells of patients with multiple myeloma. Considering these data, we investigated the presence of HHV-8 in 18 patients with POEMS syndrome (9 with MCD), by nested polymerase chain reaction (N-PCR) to detect DNA sequenses in various cells and tissues obtained by biopsy or at autopsy (13 patients, of whom 7 had MCD), and by an immunofluorescence assay to detect anti–HHV-8 IgG antibodies in blood (18 patients, of whom 9 had MCD). Detection of HHV-8 DNA was performed using three different N-PCR, targeting nonoverlapping regions in open reading frame (ORF) 25 and ORF26. Seven of 13 (54%) POEMS patients had HHV-8 DNA sequences in their tissues, as assessed by all three N-PCR, and 9 of 18 (50%) had circulating anti–HHV-8 antibodies. HHV-8 was mainly detected in the subset of POEMS patients with MCD (6 of 7 [85%] for DNA sequences; 7 of 9 [78%] for antibodies). The percentage of positive N-PCR was higher in lymph nodes than in bone marrow samples (P < .02). Sequencing of amplicons showed a homogeneous restricted variability in the ORF26 region, characteristic of the minority subgroup B defined by Zong, and responsible for isoleucine and glycine substitutions at amino acid positions 134 and 167. These findings strongly suggest an association of HHV-8 infection with POEMS syndrome-associated MCD.

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 herpesvirus-8-associated body cavity-based lymphoma in human immunodeficiency virus-infected patients: a unique B-cell neoplasm

Human immunodeficiency virus (HIV)-related body cavity-based lymphomas (BCBLs) are known to exhibit unusual clinical, immunophenotypic, and genotypic features, and have recently been found to harbor DNA sequences of a new human herpesvirus, designated Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV-8). The authors have encountered eight cases of HHV-8-associated BCBL in HIV-infected patients. A literature search revealed an additional 50 reported cases of HIV-related BCBL, as well as reports of several other disorders associated with HHV-8 DNA. Comprehensive analysis of the clinical and pathobiological features of all 58 known cases of HIV-related BCBL shows it to be a unique B-cell neoplasm with a strong propensity for body-cavity involvement without mass lesions and with little or no dissemination, poor prognosis, high grade usually immunoblastic morphology, late B-cell phenotype and genotype, no associated c-myc gene rearrangement, frequent presence of Epstein-Barr virus (EBV) genome, and uniform association with HHV-8 DNA. Considering these features in the context of other disorders associated with HHV-8 DNA, HHV-8 appears to play a causal role in BCBL, possibly in concert with EBV, and may induce this lymphoma through dysregulation of cytokines, particularly interleukin-6, or infection of an unusual B-cell subset. The characteristics of HHV-8-associated BCBL suggest a possible role for antiherpes or anticytokine agents in the treatment of this lymphoma.

Multicentric Castleman's disease with an increased serum level of macrophage colony-stimulating factor

We describe a 74-year-old patient with multicentric Castleman's disease (MCD) whose serum macrophage colony-stimulating factor level was elevated. Serum levels of tumor necrosis factor-alpha and interleukin 6 were also elevated at presentation, and they returned to normal levels after chemotherapy. Although the total serum cholesterol level was below normal on admission, it increased after chemotherapy. These results suggest that the activation of monocytes or macrophages may be involved in certain pathological phenomena in MCD.

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.

[Castleman's disease]

Castleman's disease, also called angiofollicular lymph node hyperplasia was first described as a distinct entity by Castleman et al in 1956. Two forms are now described a localized and a multicentric. The clinical and biological signs are varied and heterogeneous, and the diagnostic is made on the histologic examination. This atypical lymphoproliferative disorder is of unknown origin, but interleukin 6 play a central part in this disease. Despite the benignity of this "prelymphoma state", an aggressive course with poor prognosis occur usually in the multicentric form. Malignant lymphomas and Kaposi's sarcoma have been associated with Castleman's disease.

Castleman's disease

OBJECTIVE

To describe the two variants of Castleman's disease--the hyaline-vascular type and the plasma-cell type--and discuss the associated histologic features.

DESIGN

We present a case of the hyaline-vascular type and review the literature.

RESULTS

Castleman's disease was once thought to be localized and self-limited, but in recent years, reports have described a multicentric variety with severe systemic manifestations and, at times, an inexorable clinical course. Unlike the localized type for which surgical excision is curative regardless of the histologic type, multicentric disease often necessitates aggressive systemic therapy and portends a poor outcome. Little is known about the cause of this disorder, but the bulk of evidence points toward faulty immunoregulation that results in excessive proliferation of B lymphocytes and plasma cells in lymphoid organs.

CONCLUSION

Castleman's disease is rare and poorly understood. The diagnosis is "contextual" and must be considered in the appropriate clinical setting and only after all other causes of lymphadenopathy have been investigated and excluded. The optimal therapeutic regimen is unknown.