HCV-NS3 and IgG-Fc crossreactive IgM in patients with type II mixed cryoglobulinemia and B-cell clonal proliferations

Mixed Cryoglobulinaemia Vasculitis after Persistent Hepatitis C Virus Eradication

Mixed cryoglobulinaemia vasculitis (MCV) is a systemic vasculitis of the small and medium-size vessels caused by active hepatitis C (HCV) infection in >80% of cases. Beuthien et al. presented the first case of MCV with undetectable HCV after 10 months of therapy. In the last few years, more authors have described other cases of symptomatic MCV after 1 year of persistent HCV eradication. Here, we present a case report of a 57-year-old man who developed MCV with renal involvement after 3 years of HCV eradication with interferon therapy.

LEARNING POINTS

Mixed cryoglobulinaemia can occur after persistent hepatitis C virus eradication.Most cases described in the literature presented mixed cryoglobulinaemia vasculitis (MCV) after 1 year of HCV eradication compared with after 3 years of persistent eradication in our case.The exact mechanism linking HCV and B-cells is not fully understood, but the main factor seems to be the sustained HCV antigenic stimulation of the B-cell compartment.

Inflammation and kidney involvement in human viral diseases caused by SARS-CoV-2, HIV, HCV and HBV

Inflammation is closely related to renal diseases. This is particularly true for renal diseases caused by infections as in viral diseases. In this review, we highlight the inflammatory mechanisms that underlie kidney dysfunction in SARS-CoV-2, human immunodeficiency (HIV), hepatitis C (HCV), and hepatitis B (HBV) infections. The pathophysiology of renal involvement in COVID-19 is complex, but kidney damage is frequent, and the prognosis is worse when it happens. Virus-like particles were demonstrated mostly in renal tubular epithelial cells and podocytes, which suggest that SARS-CoV-2 directly affects the kidneys. SARS-CoV-2 uses the angiotensin-converting enzyme 2 receptor, which is found in endothelial cells, to infect the human host cells. Critical patients with SARS-CoV-2-associated acute kidney injury (AKI) show an increase in inflammatory cytokines (IL-1β, IL-8, IFN-γ, TNF-α), known as cytokine storm that favors renal dysfunction by causing intrarenal inflammation, increased vascular permeability, volume depletion, thromboembolic events in microvasculature and persistent local inflammation. Besides AKI, SARS-CoV-2 can also cause glomerular disease, as other viral infections such as in HIV, HBV and HCV. HIV-infected patients present chronic inflammation that can lead to a number of renal diseases. Proinflammatory cytokines and TNF-induced apoptosis are some of the underlying mechanisms that may explain the virus-induced renal diseases that are here reviewed.

Physiologic Target, Molecular Evolution, and Pathogenic Functions of a Monoclonal Anti-Citrullinated Protein Antibody Obtained From a Patient With Rheumatoid Arthritis

OBJECTIVE

In plasma from a patient with rheumatoid arthritis (RA), we previously isolated a human monoclonal anti-citrullinated protein antibody (ACPA), CCP-Ab1, that recognizes various citrullinated antigens. In this study, we aimed to explore the physiologic target of CCP-Ab1 and the role of molecular evolution, through affinity maturation, of this ACPA in the onset and the exacerbation of RA.

METHODS

The target protein of CCP-Ab1 was identified in the plasma of a patient with RA and purified under native conditions. Germline-reverted (GL-rev) CCP-Ab1 was generated, and its reactivity was compared to that of mature CCP-Ab1. The functions of CCP-Ab1 and GL-rev CCP-Ab1 in the onset or exacerbation of autoimmune arthritis were analyzed using autoimmune arthritis-prone SKG mice.

RESULTS

CCP-Ab1 bound citrullinated fibrinogen under native conditions. In cultures with GL-rev CCP-Ab1, the binding affinity to citrullinated fibrinogen was drastically reduced (P < 0.05). The elements implicated in GL-rev CCP-Ab1 binding to a citrullinated peptide, cfc1-cyc, were almost identical to those implicated in CCP-Ab1 binding. In arthritis-prone SKG mice, CCP-Ab1, but not GL-rev CCP-Ab1, induced significant exacerbation of experimental arthritis (P < 0.05). Increased production of interleukin-6, both in the joint tissue and in the serum, was observed in SKG mice treated with CCP-Ab1 compared to those treated with GL-rev CCP-Ab1 (P < 0.05). Furthermore, the immune complex formed by CCP-Ab1 and fibrinogen was detected at higher concentrations in the synovial tissue of SKG mice administered CCP-Ab1 (P < 0.05 versus control treatment groups).

CONCLUSION

These data show that germline-encoded CCP-Ab1, which binds weakly to citrullinated fibrinogen, undergoes hypermutation through the activation of naive B cells by citrullinated peptides/proteins, thereby stimulating high reactivity to citrullinated fibrinogen. These findings deepen our understanding of the role of molecular evolution of ACPAs in the onset and exacerbation of RA.

TLR9 signalling in HCV-associated atypical memory B cells triggers Th1 and rheumatoid factor autoantibody responses

BACKGROUND & AIMS

Hepatitis C virus (HCV) infection contributes to the development of autoimmune disorders such as cryoglobulinaemia vasculitis (CV). However, it remains unclear why only some individuals with HCV develop HCV-associated CV (HCV-CV). HCV-CV is characterized by the expansion of anergic CD19⁺CD27⁺CD21^low/- atypical memory B cells (AtMs). Herein, we report the mechanisms by which AtMs participate in HCV-associated autoimmunity.

METHODS

The phenotype and function of peripheral AtMs were studied by multicolour flow cytometry and co-culture assays with effector T cells and regulatory T cells in 20 patients with HCV-CV, 10 chronicallyHCV-infected patients without CV and 8 healthy donors. We performed gene expression profile analysis of AtMs stimulated or not by TLR9. Immunoglobulin gene repertoire and antibody reactivity profiles of AtM-expressing IgM antibodies were analysed following single B cell FACS sorting and expression-cloning of monoclonal antibodies.

RESULTS

The Tbet⁺CD11c⁺CD27⁺CD21^- AtM population is expanded in patients with HCV-CV compared to HCV controls without CV. TLR9 activation of AtMs induces a specific transcriptional signature centred on TNFα overexpression, and an enhanced secretion of TNFα and rheumatoid factor-type IgMs in patients with HCV-CV. AtMs stimulated through TLR9 promote type 1 effector T cell activation and reduce the proliferation of CD4⁺CD25^hiCD127^-/lowFoxP3⁺ regulatory T cells. AtM expansions display intraclonal diversity with immunoglobulin features of antigen-driven maturation. AtM-derived IgM monoclonal antibodies do not react against ubiquitous autoantigens or HCV antigens including NS3 and E2 proteins. Rather, AtM-derived antibodies possess rheumatoid factor activity and target unique epitopes on the human IgG-Fc region.

CONCLUSION

Our data strongly suggest a central role for TLR9 activation of AtMs in driving HCV-CV autoimmunity through rheumatoid factor production and type 1 T cell responses.

LAY SUMMARY

B cells are best known for their capacity to produce antibodies, which often play a deleterious role in the development of autoimmune diseases. During chronic hepatitis C, self-reactive B cells proliferate and can be responsible for autoimmune symptoms (arthritis, purpura, neuropathy, renal disease) and/or lymphoma. Direct-acting antiviral therapy clears the hepatitis C virus and eliminates deleterious B cells.

Heterogeneity and coexistence of oncogenic mechanisms involved in HCV-associated B-cell lymphomas

The association of HCV-infection with B-lymphomas is supported by the regression of most indolent/low-grade lymphomas following anti-viral therapy. Studies on direct and indirect oncogenic mechanisms have elucidated the pathogenesis of HCV-associated B-lymphoma subtypes. These include B-lymphocyte proliferation and sustained clonal expansion by HCV-envelope protein stimulation of B-cell receptors, and prolonged HCV-infected B-cell growth by overexpression of an anti-apoptotic BCL-2 oncogene caused by the increased frequency of t(14;18) chromosomal translocations in follicular lymphomas. HCV has been implicated in lymphomagenesis by a "hit-and-run" mechanism, inducing enhanced mutation rate in immunoglobulins and anti-oncogenes favoring immune escape, due to permanent genetic damage by double-strand DNA-breaks. More direct oncogenic mechanisms have been identified in cytokines and chemokines in relation to NS3 and Core expression, particularly in diffuse large B-cell lymphoma. By reviewing genetic alterations and disrupted signaling pathways, we intend to highlight how mutually non-contrasting mechanisms cooperate with environmental factors toward progression of HCV-lymphoma.

From hepatitis C virus infection to B-cell lymphoma

In addition to liver disorders, hepatitis C virus (HCV) is also associated with extrahepatic immune manifestations and B-cell non-Hodgkin lymphoma (NHL), especially marginal zone lymphoma, de novo or transformed diffuse large B-cell lymphoma and to a lesser extent, follicular lymphoma. Epidemiological data and clinical observations argue for an association between HCV and lymphoproliferative disorders. The causative role of HCV in NHL has been further supported by the response to antiviral therapy. Pathophysiological processes at stake leading from HCV infection to overt lymphoma still need to be further elucidated. Based on reported biological studies, several mechanisms of transformation seem however to emerge. A strong body of evidence supports the hypothesis of an indirect transformation mechanism by which sustained antigenic stimulation leads from oligoclonal to monoclonal expansion and sometimes to frank lymphoma, mostly of marginal zone subtype. By infecting lymphocytes, HCV could play a direct role in cellular transformation, particularly in de novo large B-cell lymphoma. Finally, HCV is associated with follicular lymphoma in a subset of patients. In this setting, it may be hypothesized that inflammatory cytokines stimulate proliferation and transformation of IgH-BCL2 clones that are increased during chronic HCV infection. Unraveling the pathogenesis of HCV-related B-cell lymphoproliferation is of prime importance to optimize therapeutic strategies, especially with the recent development of new direct-acting antiviral drugs.

Renal complications of liver diseases

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are the major causes of chronic liver disease. HBV and HCV affect nearly 7% of the world's population. Extra-hepatic complications and particularly renal failure have different mechanisms and manifestations. The underlying mechanism, although differing for each disease, mainly involves the immune system and antibody deposits in the kidney, which can lead to tissue damage. Areas covered: We do not cover in this review hepatorenal syndrome. We report on the renal complications of viral hepatitis (HBV, HCV, hepatitis E), autoimmune hepatitis, cirrhosis, and Wilson's disease. The most frequent renal disorders are those related to HBV, and HCV due to their high prevalence worldwide. Expert commentary: Thanks to generalization of vaccination against HBV, prevalence of HBV-related liver diseases will decrease, and thereby its associated renal involvement such as polyarteritis nodosa (an exceptional condition), and glomerulonephritis such as membranous nephropathy. Thanks to direct acting antiviral agents HCV infection will be cured within the next decade. However, HCV-related cryoglobulinemia with or without renal involvement might evolve on its own after the patient has eliminated HCV, necessitating then rituximab therapy. Conversely, orofecal-transmitted hepatitis viruses such as hepatitis A and hepatitis E are still very prevalent in developing countries; however, they are rarely associated with renal manifestations.

[Renal involvement of cryoglobulinemia]

Cryoglobulins are immunoglobulins that undergo reversible precipitation at low temperatures. They can induce systemic vasculitis, characterized by purpuric cutaneous lesions, arthritis, peripheral neuropathy, hypocomplementemia and glomerular disease. Renal pathology reveals membranoproliferative glomerulonephritis, with particularly intense mesangial cell proliferation and infiltration by macrophages, associated with intracapillary thrombi. This renal disease presents as a nephritic syndrome, with heavy proteinuria, haematuria severe hypertension and rapidly progressive kidney failure that can lead to end-stage renal disease. Hepatitis C is the main cause of mixed (type 2 or 3) cryoglobulinemia and requires the initiation of a specific antiviral therapy, together with immunosuppressive drugs. Rituximab is now considered as the best immunosuppressive therapy in this situation, inducing B-cell depletion, clearance of circulating cryoglobulin and resolution of renal symptoms. Monoclonal (type 1) cryoglobulinemia, is a rare condition, but it usually reveals an B-cell or a plasma cell proliferation, that require a specific hematological treatment to obtain remission of the renal disease.

From the pathogenesis to the cure of indolent B-cell lymphoproliferative disorders associated with hepatitis C virus infection: which role for direct-acting antivirals?

INTRODUCTION

Hepatitis C virus (HCV) causes monoclonal B cell lymphoproliferative disorders ranging from benign, such as in mixed cryoglobulinemia (MC), to indolent or aggressive lymphomas. MC and indolent lymphomas commonly regress when HCV is eradicated with interferon (IFN) therapy; however, sustained virologic response (SVR) to IFN is achieved only in ~50% of patients. The new all oral direct-acting antivirals (DAA), yielding nearly 100% SVR, promise a breakthrough in the treatment of HCV-associated lymphoproliferative disorders, but experience is still scanty. Areas covered: A literature search was performed to summarize current pathogenetic hypotheses in HCV-associated indolent lymphoproliferative disorders and to identify clinical trials focused on the use of antiviral therapy. Hematological outcomes of IFN-based and IFN-free DAA-based regimens were compared. Expert commentary: While MC appears to regress in most patients after DAA therapy, the still very limited experience with indolent lymphomas suggests that hematologic responses might be less than those observed with IFN. Furthermore, anecdotal observations of early progression to aggressive lymphoma after DAA are disquieting. Large studies are needed to determine the values and limits of DAA for treating HCV-associated indolent lymphomas and to identify subgroups at risk of non-response.

Hepatitis C virus - Associated marginal zone lymphoma

The link between hepatitis C virus (HCV) infection and the development of B-cell non-Hodgkin lymphoma is now well established and based on a number of epidemiological studies. It is further supported by the observation of lymphoma regression after HCV eradication by antiviral treatment. The far most frequent entities are marginal zone lymphoma (MZL) and diffuse large B-cell lymphoma (DLBCL). MZL usually emerge on a background of mixed cryoglobulinemia, a low-grade lymphoproliferation, and often transform into DLBCL, thereby following a multistep oncogenesis process. The role of HCV in lymphomagenesis is not yet fully understood but several mechanisms have been proposed including (i) chronic external stimulation through the B-cell receptor and other surface receptors, and (ii) direct transformation by intracellular viral proteins, the former being probably predominant in MZL. Regression of HCV-associated MZL can be achieved with antiviral therapy and the novel generation of direct-acting antiviral agents appears highly effective and safe for the treatment of these lymphoma.

Delineation of autoantibody repertoire through differential proteogenomics in hepatitis C virus-induced cryoglobulinemia

Antibodies cross-reactive to pathogens and autoantigens are considered pivotal in both infection control and accompanying autoimmunity. However, the pathogenic roles of autoantibodies largely remain elusive without a priori knowledge of disease-specific autoantigens. Here, through a novel quantitative proteogenomics approach, we demonstrated a successful identification of immunoglobulin variable heavy chain (VH) sequences highly enriched in pathological immune complex from clinical specimens obtained from a patient with hepatitis C virus-induced cryoglobulinemia (HCV-CG). Reconstructed single-domain antibodies were reactive to both HCV antigens and potentially liver-derived human proteins. Moreover, over the course of antiviral therapy, a substantial "de-evolution" of a distinct sub-repertoire was discovered, to which proteomically identified cryoprecipitation-prone autoantibodies belonged. This sub-repertoire was characterized by IGHJ6*03-derived, long, hydrophobic complementarity determining region (CDR-H3). This study provides a proof-of-concept of de novo mining of autoantibodies and corresponding autoantigen candidates in a disease-specific context in human, thus facilitating future reverse-translational research for the discovery of novel biomarkers and the development of antigen-specific immunotherapy against various autoantibody-related disorders.

The expanding spectrum of HCV-related cryoglobulinemic vasculitis: a narrative review

Cryoglobulinemic vasculitis (CV) is a small-to-medium-vessel vasculitis that appears in 10-15 % of patients chronically infected with hepatitis C virus (HCV). The classic symptom triad of CV, purpura/asthenia/arthralgia, is accompanied by clinical features that include glomerulonephritis, neuropathy, interstitial pneumonitis, and cardiomyopathy, ranging in their severity from mild to life threatening. The risk of developing non-Hodgkin lymphoma is also higher. The cumulative 10-year survival rate of CV patients is significantly lower than in the age- and sex-matched general population, with death typically caused by nephropathy, malignancies, liver involvement, and severe infections. Unfailing serological stigmata include both a cryoglobulin IgM fraction with rheumatoid factor activity and decreased complement C4 levels. On peripheral B cells, the expression of the CD81 B cell receptor is reduced while that of the CD19 receptor is increased. A monoclonal B cell lymphocytosis develops in almost one-third of patients. HCV-related proteins (but not HCV-RNA genomic sequences) can be detected on biopsy samples by immunofluorescence and immunohistochemistry and involve the vessel lumen, vessel walls, and the perivascular spaces of the skin, kidney, and peripheral nerves, supporting the pathogenetic role of HCV in the onset of a widespread microvasculitis. Based on the demonstration of HCV infection in the large majority of CV patients, a therapeutic regimen consisting of once-weekly pegylated interferon-α and the daily administration of ribavirin results in a sustained virologic response in ~50 % of patients. In those with refractory and relapsing disease, addition of the anti-CD20 monoclonal antibody rituximab has significantly increased the overall response rates. The extension to CV of latest-generation direct-acting antivirals, strikingly successful in non-CV HCV-positive patients, has yielded high complete response rates according to the few studies published thus far.

Extrahepatic Manifestations of Hepatitis C Virus

Chronic infection with the hepatitis C virus (HCV) is a major cause of liver disease worldwide and is also responsible for extrahepatic manifestations (EHMs) involving the skin, kidneys, salivary glands, eyes, thyroid, and immune system. Mixed cryoglobulinemia is the prototype EHM related to HCV infection. Although these HCV-related EHMs may contribute to significant rates of morbidity affecting patient's quality of life and survival, most of these complications can reverse after HCV eradication by interferon therapy. This notwithstanding, individual patients may have an irreversible injury in various organs that is not reversed by a cure of the HCV infection.

Virus-driven autoimmunity and lymphoproliferation: the example of HCV infection

HCV chronic infection is characterized by possible development of both hepatic and extrahepatic manifestations. The infection by this both hepatotropic and lymphotropic virus is responsible for polyoligoclonal B-lymphocyte expansion, leading to several immune-mediated disorders. Mixed cryoglobulinemia syndrome that in some cases may evolve to frank B-cell non-Hodgkin's lymphoma is the prototype of HCV-driven autoimmune and lymphoproliferative disorders. The HCV oncogenic potential has been suggested by several clinicoepidemiological and laboratory studies; it includes hepatocellular carcinoma, B-cell non-Hodgkin's lymphoma and papillary thyroid cancer. The definition HCV syndrome refers to the complex of HCV-driven diseases; these latter are characterized by heterogeneous geographical distribution, suggesting a role of other important genetic and/or environmental cofactors. The natural history of HCV syndrome is the result of a multifactorial and multistep pathogenetic process, which may evolve from mild manifestations to systemic autoimmune disorders, and less frequently to malignant neoplasias. The present updated review analyzes the clinical and pathogenetic aspects of the main HCV-associated diseases.

Assessment of total hepatitis C virus (HCV) core protein in HCV-related mixed cryoglobulinemia

Introduction

In hepatitis C virus (HCV)-related mixed cryoglobulinemia (MCG), the nonenveloped HCV core protein (HCV-Cp) is a constituent of the characteristic cold-precipitating immune complexes (ICs). A possible correlation between HCV-Cp, virologic, laboratory, and clinical parameters in both untreated MCG patients and those undergoing specific treatment was explored.

Methods

HCV-Cp was quantified by a fully automated immune assay. Correlations between HCV-Cp and HCV RNA, cryocrit, and virus genotype (gt) were investigated in 102 chronically HCV-infected MCG patients.

Results

HCV-Cp concentrations strongly correlated with HCV RNA levels in baseline samples. An average ratio of 1,425 IU and 12,850 IU HCV RNA per picogram HCV-Cp was estimated in HCV gt-1 and gt-2 patients, respectively. This equation allowed us to estimate that, on average, HCV-Cp was associated with the viral genome in only 3.4% of the former and in 35% of the latter group of patients. The direct relation between HCV-Cp and the cryocrit level suggests that the protein directly influences the amount of cryoprecipitate. Although the therapy with rituximab (RTX) as a single agent resulted in the enhancement of HCV-Cp levels, in patients treated with RTX in combination with a specific antiviral therapy (pegylated interferon-α plus ribavirin), the prompt and effective clearance of HCV-Cp was documented.

Conclusions

Our data provide evidence that HCV-Cp has a direct effect on the cold-precipitation process in a virus genotype-dependence in HCV-related MCG patients.

Relationships between lymphomas linked to hepatitis C virus infection and their microenvironment

The relationships between lymphomas and their microenvironment appear to follow 3 major patterns: (1) an independent pattern; (2) a dependent pattern on deregulated interactions; and (3) a dependent pattern on regulated coexistence. Typical examples of the third pattern are hepatitis C virus (HCV)-associated marginal zone lymphomas (MZLs) and mucosa-associated lymphoid tissue lymphomas. In these lymphomas, a regulated coexistence of the malignant cells and the microenvironmental factors usually occurs. At least initially, however, tumor development and cell growth largely depend on external signals from the microenvironment, such as viral antigens, cytokines, and cell-cell interactions. The association between HCV infection and B-cell lymphomas is not completely defined, although this association has been demonstrated by epidemiological studies. MZL and diffuse large B-cell lymphoma are the histotypes most frequently associated with HCV infection. Many mechanisms have been proposed for explaining HCV-induced lymphomagenesis; antigenic stimulation by HCV seems to be fundamental in establishing B-cell expansion as observed in mixed cryoglobulinemia and in B-cell lymphomas. Recently, antiviral treatment has been proved to be effective in the treatment of HCV-associated indolent lymphomas. Importantly, clinically responses were linked to the eradication of the HCV-RNA, providing a strong argument in favor of a causative link between HCV and lymphoproliferation.

Hepatitis C virus (HCV)-related cryoglobulinemia: cryoglobulin type and anti-HCV profile. Clin Vaccine Immunol. 2013;20:698-703. [PMID: 23467778 DOI: 10.1128/cvi.00720-12]

Cryoglobulin characteristics in chronic hepatitis C (CHC) might be of importance for knowing more about the pathogenesis and treatment of the disease. We aimed to investigate the relationship between cryoglobulin types and their specificity against hepatitis C virus (HCV) antigenic epitopes in CHC patients. We analyzed samples from 43 patients with HCV-associated cryoglobulinemia, of whom 4 had concomitant lymphoma. Cryoglobulins were measured, purified, typed by immunofixation electrophoresis, and tested for IgG and IgM anti-HCV antibodies by immunoblot analysis and an enzyme-linked immunosorbent assay (ELISA). Clinical and other laboratory data were recorded. The median cryocrit level of the tested samples was 6%. Type I cryoglobulins were detected in 9.3% (4/43) of the cryoprecipitates, and type II cryoglobulins were detected in 48.8% (21/43) of the cryoprecipitates. IgM monoclonal protein, mainly IgM(κ), was found in 92% (23/25) of type I and II cryoprecipitates. Type III cryoglobulins were identified in 41.9% (18/43) of the patients and were associated with high blood serum IgG levels. In 81.3% (13/16) of type II and 92.3% (12/13) of type III cryoglobulins, there was IgG reactivity against the viral core region. Ninety-two percent and 32% of IgG anti-HCV core-positive cryoprecipitates had additional specificities against the NS3 and NS4 regions, respectively. Also, IgM anti-HCV antibodies were detected in 31% of the cryoprecipitates. In conclusion, all types of cryoglobulins were found in patients with HCV-associated cryoglobulinemia, with type II being the most frequently identified. Type III cryoglobulins were common and were associated with high serum IgG levels. HCV-related cryoglobulins demonstrated IgM, and particularly IgG, anti-HCV specificities, mainly against the core and NS3 epitopes.

The hepatitis C virus infection as a systemic disease

Hepatitis C Virus (HCV) is a major health problem, infecting about 3 % of people worldwide and leading to liver as well as extrahepatic diseases. This justifies the definition of HCV infection as a systemic disease. Based on available data, the link between the virus and some of these extrahepatic disorders is certain, whereas for some others needs further confirmation. HCV-related lymphoproliferative disorders, ranging from benign, but pre-lymphomatous conditions, like mixed cryoglobulinemia, to frank lymphomas, represent the extrahepatic manifestations most closely related to HCV. The primary involvement of the liver and lymphatic system corresponds to the double viral tropism, being HCV able to infect both hepatic and lymphatic cells. Other HCV-associated disorders include renal, endocrine, dermatological, cardiovascular, rheumatologic and central nervous system diseases. On the whole, the HCV disease appears a very important, mainly hidden, public health problem leading to heavy direct and indirect costs. The possibility that HCV may be eradicated following antiviral therapy is important for both the therapeutic and preventive points of view, making the HCV disease an ideal model for pathogenetic studies.

Hepatitis C virus-mediated modulation of cellular immunity

The hepatitis C virus (HCV) is a major cause of chronic liver disease globally. A chronic infection can result in liver fibrosis, liver cirrhosis, hepatocellular carcinoma and liver failure in a significant ratio of the patients. About 170 million people are currently infected with HCV. Since 80 % of the infected patients develop a chronic infection, HCV has evolved sophisticated escape strategies to evade both the innate and the adaptive immune system. Thus, chronic hepatitis C is characterized by perturbations in the number, subset composition and/or functionality of natural killer cells, natural killer T cells, dendritic cells, macrophages and T cells. The balance between HCV-induced immune evasion and the antiviral immune response results in chronic liver inflammation and consequent immune-mediated liver injury. This review summarizes our current understanding of the HCV-mediated interference with cellular immunity and of the factors resulting in HCV persistence. A profound knowledge about the intrinsic properties of HCV and its effects on intrahepatic immunity is essential to be able to design effective immunotherapies against HCV such as therapeutic HCV vaccines.

Molecular signature in HCV-positive lymphomas. Clin Dev Immunol. 2012;2012:623465. [PMID: 22952554 PMCID: PMC3431075 DOI: 10.1155/2012/623465]

Hepatitis C virus (HCV) is a positive, single-stranded RNA virus, which has been associated to different subtypes of B-cell non-Hodgkin lymphoma (B-NHL). Cumulative evidence suggests an HCV-related antigen driven process in the B-NHL development. The underlying molecular signature associated to HCV-related B-NHL has to date remained obscure. In this review, we discuss the recent developments in this field with a special mention to different sets of genes whose expression is associated with BCR coupled to Blys signaling which in turn was found to be linked to B-cell maturation stages and NF-κb transcription factor. Even if recent progress on HCV-B-NHL signature has been made, the precise relationship between HCV and lymphoma development and phenotype signature remain to be clarified.

HCV and lymphoproliferation. Clin Dev Immunol. 2012;2012:980942. [PMID: 22852020 PMCID: PMC3407626 DOI: 10.1155/2012/980942]

Hepatitis C virus (HCV) infection is a serious public health problem because of its worldwide diffusion and sequelae. It is not only a hepatotropic but also a lymphotropic agent and is responsible not only for liver injury--potentially evolving to cirrhosis and hepatocellular carcinoma--but also for a series of sometimes severely disabling extrahepatic diseases and, in particular, B-cell lymphoproliferative disorders. These latter range from benign, but prelymphomatous conditions, like mixed cryoglobulinemia, to frank lymphomas. Analogously with Helicobacter pylori related lymphomagenesis, the study of the effects of viral eradication confirmed the etiopathogenetic role of HCV and showed it is an ideal model for better understanding of the molecular mechanisms involved. Concerning these latter, several hypotheses have been proposed over the past two decades which are not mutually exclusive. These hypotheses have variously emphasized the important role played by sustained stimulation of the immune system by HCV, infection of the lymphatic cells, viral proteins, chromosomal aberrations, cytokines, or microRNA molecules. In this paper we describe the main hypotheses that have been proposed with the corresponding principal supporting data.

A randomized controlled trial of rituximab for the treatment of severe cryoglobulinemic vasculitis

OBJECTIVE

To conduct a long-term, prospective, randomized controlled trial evaluating rituximab (RTX) therapy for severe mixed cryoglobulinemia or cryoglobulinemic vasculitis (CV).

METHODS

Fifty-nine patients with CV and related skin ulcers, active glomerulonephritis, or refractory peripheral neuropathy were enrolled. In CV patients who also had hepatitis C virus (HCV) infection, treatment of the HCV infection with antiviral agents had previously failed or was not indicated. Patients were randomized to the non-RTX group (to receive conventional treatment, consisting of 1 of the following 3: glucocorticoids; azathioprine or cyclophosphamide; or plasmapheresis) or the RTX group (to receive 2 infusions of 1 gm each, with a lowering of the glucocorticoid dosage when possible, and with a second course of RTX at relapse). Patients in the non-RTX group who did not respond to treatment could be switched to the RTX group. Study duration was 24 months.

RESULTS

Survival of treatment at 12 months (i.e., the proportion of patients who continued taking their initial therapy), the primary end point, was statistically higher in the RTX group (64.3% versus 3.5% [P < 0.0001]), as well as at 3 months (92.9% versus 13.8% [P < 0.0001]), 6 months (71.4% versus 3.5% [P < 0.0001]), and 24 months (60.7% versus 3.5% [P < 0.0001]). The Birmingham Vasculitis Activity Score decreased only after treatment with RTX (from a mean ± SD of 11.9 ± 5.4 at baseline to 7.1 ± 5.7 at month 2; P < 0.001) up to month 24 (4.4 ± 4.6; P < 0.0001). RTX appeared to be superior therapy for all 3 target organ manifestations, and it was as effective as conventional therapy. The median duration of response to RTX was 18 months. Overall, RTX treatment was well tolerated.

CONCLUSION

RTX monotherapy represents a very good option for severe CV and can be maintained over the long term in most patients.

Hepatitis C virus infection and mixed cryoglobulinemia. Clin Dev Immunol. 2012;2012:502156. [PMID: 22844322 PMCID: PMC3403343 DOI: 10.1155/2012/502156]

Hepatitis C virus (HCV) chronic infection is recognized as the major cause of mixed cryoglobulinemia (MC). Its persistence represents a continuous stimulus for host immune system with production of circulating immune complexes (ICs), one-third of them with cryoprecipitate property. Several factors contribute to the biological activities of ICs, many of which are not completely known. Among them, complement factors play a crucial role in the cold-insoluble ICs-mediated vasculitis, involving primarily small blood vessels in different tissues including skin, kidney, peripheral, and central nervous system. Liver represents the major target of HCV infection with inflammatory infiltrates, resembling secondary lymphoid follicles. Cytokine like CXCL13 contribute to B-cell homing in intraportal lymphoid aggregates, in which B-cell clonal selection may arise. B-cell clonal expansion starts as an antigen-driven event and expands towards indolent and malignant B-cell proliferation. Occurrence of intrahepatic B-cell clonalities correlates with extrahepatic clinical manifestations of HCV infection. In this context, cryoglobulinemic patients should be considered a peculiar HCV-infected population that needs a clinical multidisciplinary approach and more articulated therapeutic measures.

Molecular mimicry as a mechanism of autoimmune disease

A variety of mechanisms have been suggested as the means by which infections can initiate and/or exacerbate autoimmune diseases. One mechanism is molecular mimicry, where a foreign antigen shares sequence or structural similarities with self-antigens. Molecular mimicry has typically been characterized on an antibody or T cell level. However, structural relatedness between pathogen and self does not account for T cell activation in a number of autoimmune diseases. A proposed mechanism that could have been misinterpreted for molecular mimicry is the expression of dual T cell receptors (TCR) on a single T cell. These T cells have dual reactivity to both foreign and self-antigens leaving the host vulnerable to foreign insults capable of triggering an autoimmune response. In this review, we briefly discuss what is known about molecular mimicry followed by a discussion of the current understanding of dual TCRs. Finally, we discuss three mechanisms, including molecular mimicry, dual TCRs, and chimeric TCRs, by which dual reactivity of the T cell may play a role in autoimmune diseases.

HCV proteins and immunoglobulin variable gene (IgV) subfamilies in HCV-induced type II mixed cryoglobulinemia: a concurrent pathogenetic role

The association between hepatitis C virus (HCV) infection and type II mixed cryoglobulinemia (MCII) is well established, but the role played by distinct HCV proteins and by specific components of the anti-HCV humoral immune response remains to be clearly defined. It is widely accepted that HCV drives the expansion of few B-cell clones expressing a restricted pool of selected immunoglobulin variable (IgV) gene subfamilies frequently endowed with rheumatoid factor (RF) activity. Moreover, the same IgV subfamilies are frequently observed in HCV-transformed malignant B-cell clones occasionally complicating MCII. In this paper, we analyze both the humoral and viral counterparts at the basis of cryoglobulins production in HCV-induced MCII, with particular attention reserved to the single IgV subfamilies most frequently involved.

The role of humoral innate immunity in hepatitis C virus infection

Infection with Hepatitis C Virus (HCV) causes chronic disease in approximately 80% of cases, resulting in chronic inflammation and cirrhosis. Current treatments are not completely effective, and a vaccine has yet to be developed. Spontaneous resolution of infection is associated with effective host adaptive immunity to HCV, including production of both HCV-specific T cells and neutralizing antibodies. However, the supporting role of soluble innate factors in protection against HCV is less well understood. The innate immune system provides an immediate line of defense against infections, triggering inflammation and playing a critical role in activating adaptive immunity. Innate immunity comprises both cellular and humoral components, the humoral arm consisting of pattern recognition molecules such as complement C1q, collectins and ficolins. These molecules activate the complement cascade, neutralize pathogens, and recruit antigen presenting cells. Here we review the current understanding of anti-viral components of the humoral innate immune system that play a similar role to antibodies, describing their role in immunity to HCV and their potential contribution to HCV pathogenesis.

Hepatitis C virus infection and lymphoma. Mediterr J Hematol Infect Dis. 2010;2:e2010004. [PMID: 21415946 PMCID: PMC3033108 DOI: 10.4084/mjhid.2010.004]

Apart from its well known role as an etiological agent for non-A and non-B viral hepatitis, there is growing evidence that hepatitis C virus is associated to B-cell non-Hodgkin lymphoma. The association between HCV and lymphoproliferative disorders has been recently postulated based on epidemiological data, biological studies and clinical observations. Although various subtypes of lymphomas appear to be associated to HCV, diffuse large B-cell lymphoma, small lymphocytic lymphoma/chronic lymphocytic leukemia and marginal zone lymphoma appeared to be particularly represented among HCV-positive patients. The causative role of HCV in those disorders has been further supported by the response to antiviral therapy. Despite a better understanding of pathophysiological processes at stake leading from HCV infection to overt lymphoma, many issues still need to be further elucidated. Although HCV has been demonstrated to directly infect peripheral blood mononuclear cells both in vitro and, in some cases, in vivo, a strong body of evidence rather supports the hypothesis of an indirect transformation mechanism by which sustained antigenic stimulation leads from oligoclonal to monoclonal expansion and sometimes to lymphoma, probably through secondary oncogenic events. Here, we review epidemiological and biological studies, as well as clinical data on antiviral therapy, linking HCV-infection to B-cell non-Hodgkin lymphoma.

PPAR signaling pathway and cancer-related proteins are involved in celiac disease-associated tissue damage

Celiac disease (CD) is an immune-mediated disorder triggered by the ingestion of wheat gliadin and related proteins in genetically predisposed individuals. To find a proteomic CD diagnostic signature and to gain a better understanding of pathogenetic mechanisms associated with CD, we analyzed the intestinal mucosa proteome alterations using two dimensional difference gel electrophoresis (2D-DIGE) coupled with matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF ms) of CD patients with varying degrees of histological abnormalities defined by Marsh criteria and controls. Our results clearly evidenced the presence of two groups of patients: Group A, including controls and Marsh 0-I CD patients; and Group B, consisting of CD subjects with grade II-III Oberhuber-Marsh classification. Differentially expressed proteins were involved mainly in lipid, protein and sugar metabolism. Interestingly, in Group B, several downregulated proteins (FABP1, FABP2, APOC3, HMGCS2, ACADM and PEPCK) were implicated directly in the peroxisome proliferator-activated receptor (PPAR) signaling pathway. Moreover, Group B patients presented a deregulation of some proteins involved in apoptosis/survival pathways: phosphatidylethanolamine-binding protein 1 (PEBP1), Ras-related nuclear protein (Ran) and peroxiredoxin 4 (PRDX4). PEBP1 downregulation and RAN and PRDX4 upregulation were associated with more severe tissue damage. Likewise, IgMs were found strongly upregulated in Group B. In conclusion, our results indicate that a downregulation of proteins involved in PPAR signaling and the modulation of several cancer-related proteins are associated with the highest CD histological score according to Oberhuber-Marsh classification.

HLA DR-DQ combination associated with the increased risk of developing human HCV positive non-Hodgkin's lymphoma is related to the type II mixed cryoglobulinemia

This investigation was focused on the contribution of individual human leukocyte antigen (HLA)-DR and -DQ alleles to the human hepatitis C virus (HCV)(+) non-Hodgkin's lymphoma (NHL), with and without mixed cryoglobulinemia (MC), to study whether individual HLA class II alleles are expressed preferentially or equally in human HCV-specific NHL. For this purpose, peripheral blood mononuclear cells were obtained from two groups of patients with HCV(+) NHL and with or without MC (70 and 71 cases, respectively), and from 4575 blood donors. Eighty-three subjects with HCV infection only, and 118 patients with MC, only without lymphoma, were added as additional control groups. Individual HLA-DR and -DQ alleles were determined using high-resolution sequence-based typing and then data were collected by considering the HLA-DRB1 and DQB1 supertypes on the basis of common structural and functional features, proposed by in silico Bioinformatic studies. From the data, it is evidenced that the DR5-DQ3 HLA combination was strongly associated with the HCV (+) MC (+) NHL group of patients compared with bone marrow donor population (P<or= 0.001, RR = 2.498), while the contribution of DR1-DQ1 was higher in HCV (+) NHL without MC (P<or= 0.001, RR = 2.519). Thus, cryoglobulinemia clinical manifestation was found to be correlated with the preferential use of HLA DR-DQ combination in HCV-associated NHL. These data provide new insight into HCV-associated lymphoproliferative pathogenesis.

Characterization of antibodies directed against the immunoglobulin light kappa chain variable chain region (VK) of hepatitis C virus-related type-II mixed cryoglobulinemia and B-cell proliferations

Autoimmune type-II cryoglobulinemia (II-MC) is sustained by hepatitis C virus (HCV) infection and B-cell (oligo)clones. This is the reason why the disease may be considered an "indolent B-cell lymphoma (NHL)." B clones show a restricted use of immunoglobulin variable genes (BCR), in particular in the use of the variable kappa (VK)3-20/15 light chain, and show a homology between their BCR functional regions and those of autoimmune rheumatoid factors. We underlined the BCR unique repertoire with frequent rheumatoid factor activity also observed in other autoimmune disorders associated with NHL. The immunoglobulin idiotype is a clonal B-cell marker and an ideal target for immunotherapy. Five monoclonal antibodies were produced in our laboratory toward the VK3-20 of a subject with HCV infection and a II-MC-associated NHL. Epitope determination was performed using the epitope excision approach. Monoclonal antibody reactivity was tested in vitro in ELISA, Western blot, and cytofluorimetry. Data confirmed that a panel of antibodies, reactive against shared idiotypes, can be produced from patients with HCV-associated B-cell lymphoproliferative diseases, thus obviating the need to produce an anti-idiotype antibody for each patient.

Clonal CD27+ CD19+ B cell expansion through inhibition of FC gammaIIR in HCV(+) cryoglobulinemic patients

Persistent HCV infection may be associated with extrahepatic manifestations such as type II mixed cryoglobulinemia (II-MC), a clonal B cell proliferative disorder. In persistent HCV infection without II-MC, an increase in serum immunoglobulins (Ig) is commonly observed. This increase is polyclonal and is determined primarily by increased levels of IgG which include both HCV-specific and nonspecific antibodies. Nonetheless, memory CD27(+) B cells do not accumulate. This paradoxical phenomenon depends on heightened sensitivity of memory B cells to BCR-independent noncognate T cell help, which speeds up their terminal differentiation into antibody-secreting cells and makes them more prone to apoptosis. In persistent HCV infection with II-MC, serum Ig elevation is also a general occurrence, and characteristically includes IgM antibodies with rheumatoid factor activity, which are essential for the development of circulating, cryoprecipitable immune complexes. Hypergammaglobulinemia is sustained by a peripheral expansion of IgM(+)k(+)IgD(low/neg)CD21(low)CD27(+) B cells. These cells exhibit marked V(H), J(H), and V(K) gene segment usage restriction, indicating that a limited number of antigens drive their proliferation through BCR interaction. Recently, two epitopes, one of the human IgG and the second of the HCV(NS3) protein, had been identified and demonstrated able to link the BCR exposed on II-MC subjects. Based on the above findings, we propose a model whereby BCR binding the IgM/IgG/HCV(NS3) immune complexes deprives Fc gammaIIR of its natural ligand. This takes the brake off RF(+)CD27(+) B cell proliferation and promotes their selective accumulation, which is otherwise prevented by increased apoptosis susceptibility in persistent HCV infection without II-MC.

Hepatitis C virus-induced cryoglobulinemia

In this review we discuss the clinical manifestations, pathogenesis, and treatment of hepatitis C virus (HCV)-related cryoglobulinemia. HCV is a major cause of liver-related morbidity and is increasingly recognized as an instigator of B-cell lymphoproliferative disorders such as mixed cryoglobulinemia and non-Hodgkin lymphoma. Cryoglobulinemia is characterized by the clonal expansion of rheumatoid factor-expressing B cells in the liver, lymph nodes, and peripheral blood, resulting in the presence of cryoglobulins in the circulation. Cryoglobulins are cold-insoluble immune complexes containing rheumatoid factor, polyclonal IgG, and HCV RNA that precipitate and deposit on vascular endothelium, causing vasculitis in organs such as the skin, kidneys, and peripheral nerves. A subset of patients develops a low-grade lymphoma composed of B cells that are immunophenotypically similar to the expanded B cells seen in cryoglobulinemia. HCV-related B-cell lymphoproliferative disorders likely comprise a spectrum of disease, ranging from asymptomatic clonal B-cell expansions to pathogenic cryoglobulinemia and lymphoma. It is unclear how B cells become dysregulated during the course of chronic HCV infection, and continued patient-centered research is necessary to elucidate the pathogenesis of HCV-related B-cell dysregulation.

Cryoglobulinemia and renal disease

PURPOSE OF REVIEW

Cryoglobulinemia occurs in a variety of clinical settings including lymphoproliferative disorders, infection and autoimmune disease. The worldwide pandemic of hepatitis C virus infection has resulted in a significant increase in its extrahepatic complications including cryoglobulinemia and renal disease. Here we review the types of cryoglobulins, mechanisms of cryoglobulin formation, links between hepatitis C virus and renal disease, and current approaches to therapy.

RECENT FINDINGS

The prevalence of cryoglobulinemia in hepatitis C virus-infected individuals is surprisingly large and may be found in more than 50% of some infected subpopulations. Most of these patients will not have overt renal disease, but there is a population of unknown size of patients with subclinical glomerular disease that has the potential to become clinically significant. In cases of hepatitis C virus-associated cryoglobulinemia, treatment remains focused on eradication of viremia, but interventions directed at B lymphocytes are increasingly utilized. The mechanisms of cryoglobulin formation and renal injury remain largely obscure, but recent evidence implicates the innate immune system in the initiation of disease.

SUMMARY

The most common renal injury associated with hepatitis C virus infection, in patients both with and without evidence of cryoglobulinemia, is membranoproliferative glomerulonephritis. There has been increasing focus on defining the mechanisms that link these processes and the evolution of renal injury in all clinical settings of cryoglobulinemia.

Hepatitis C virus infection, mixed cryoglobulinemia and BLyS upregulation: targeting the infectious trigger, the autoimmune response, or both?

Mixed cryoglobulinemia syndrome (MCsn) is a systemic vasculitis prevalently mediated by immune complexes, i.e., mixed cryoglobulins, and characterized by non-neoplastic B-cell lymphoproliferation favouring the progression into frank B-cell non-Hodgkin lymphoma (NHL) in 5-10% of patients. The hepatitis C virus (HCV) infection is the etiologic agent in the large majority of MCsn cases and chronic antigenic stimulation by HCV is considered a key mechanism sustaining the proliferation of the RF-secreting B-cell clones. Besides chronic antigenic stimulation, cytokines and growth factors may also play a key role in sustaining B-cell overactivation. B-lymphocyte stimulator (BlyS) was recently described as a critical survival factor for B cells, promoting their activation and maturation. Abnormal production of BLyS alters immune tolerance by allowing the survival of autoreactive B cells, thus triggering autoimmune disorders. BLyS inhibits B-cell apoptosis, and B-cell apoptosis is implicated in the pathogenesis of MCsn, as well as of other autoimmune diseases. Both antiviral therapy and B- cell depletive therapy in MCsn may influence BlyS expression. Antiviral therapy, monotherapy against biologic targets downstream viral infection, or the combination of the two, should be optimized in the single patient and stage of the disease, based on disease pathobiology, efficacy and safety issues.

Hepatitis C virus (HCV)-driven stimulation of subfamily-restricted natural IgM antibodies in mixed cryoglobulinemia

Hepatitis C virus (HCV) infection has been closely related to mixed cryoglobulinemia (MC). During HCV infection, cryoglobulins derive from the restricted expression of few germline genes as VH1-69, a subfamily highly represented in anti-HCV humoral response. Little is known about the self-reacting IgM component of the cryoprecipitate. In the present study, the IgM/K repertoire of an HCV-infected cryoglobulinemic patient was dissected by phage-display on well-characterized anti-HCV/E2 VH1-69-derived monoclonal IgG1/Kappa Fab fragments cloned from the same patient. All selected IgM clones were shown to react with the anti-HCV/E2 antibodies belonging to VH1-69 subfamily. More than 60% of selected clones showed a bias in VH gene usage, restricted to two VH subfamilies frequently described in autoimmune manifestations (VH3-23; VH3-21). Moreover, all selected clones showed an high similarity (>98.5%) to germline genes evidencing their natural origin. A possible hypothesis is that clones belonging to some subfamilies are naturally prone to react against other VH gene subfamilies, as VH 1-69. An antigen-driven stimulation of these subfamilies, and their overexpression as in HCV infection, could lead to a breaking of humoral homeostatic balance exposing the patients to the risk of developing autoimmune disorders.

HCV-related immunocytoma and type II mixed cryoglobulinemia-associated autoantigens

Hepatitis C virus (HCV) is a hepatotropic virus causing hepatocellular damage and chronic liver inflammation that progressively can lead to cirrhosis and hepatocellular carcinoma (HCC). HCV is also lymphotropic, as demonstrated by its capacity to replicate in lymphocytes, by the recurrent detection of organ- and non-organ-specific autoantibodies in HCV-infected patients, and by the strong association found between HCV infection and type II mixed cryoglobulinemic syndrome (MC-II). Moreover, accumulating data ascribe an etiopathogenetic role in the development of B cell non-Hodgkin's lymphomas (NHL) to HCV. All these findings account for the profound effect of HCV infection in the host's immune system. The unique virus-host interactions that culminate in the generation and sustained production of autoantibodies and cryoglobulins have not been delineated. It appears that chronic antigenic stimulation could cause the emergence of specific B cell clones that produce cryoglobulins; moreover, B cell activation and/or deregulation could originate as a result of HCV binding to CD81 tetraspanin or as a consequence of its ability to replicate in B cells. In a previous study we demonstrated that, in MC-II HCV-positive patients, cryoprecipitated monoclonal IgMs, and B cell receptors (BCR) of overexpanded B cell clones share the same combinatory region. Moreover, these IgMs were reactive against both the Fc region of human IgG and the HCV-NS3 antigen. NS3 and Fc epitopes have been idengified by epitope excision approach. One of the idengified NS3 epitopes has been used to immunize a mouse and the monoclonal antibody obtained showed the same cross-reactivity as patients' IgMs. The characterization of antigenic specificity of this antibody may be useful to idengify antigens that can stimulate B cell proliferation in HCV-infected individuals.

Pathophysiological aspects of memory B-cell development

B cells follow two functionally distinct pathways of development: a classical germinal center (GC) T-dependent pathway in which diversification and maturation generate a slow, but virtually unlimited high-affinity response to cognate antigens; and a marginal zone (MZ) T-independent pathway providing a first line of 'innate-like' defense against specific pathogens. Cells populating these two distinct locations are the normal counterparts of two clinically important pathological entities, follicular lymphoma (FL) and MZ lymphoma (MZL). FL and MZ represent paradigms of two rising concepts of lymphomagenesis, protracted preclinical and antigen-driven lymphoproliferation, respectively. Integrating the mechanisms and functions of MZ and GC B cells and the distinctive features of their pathological counterparts should provide essential clues to the understanding of their malignant development, and should offer new insights into the design of effective treatments for B-cell lymphomas.

The pathophysiology of HCV induced B-cell clonal disorders

Hepatitis C virus (HCV) has been shown in epidemiologic studies to be associated with immune system disorders. Primarily disorders that stem from B-cell regulatory control disturbance, such as mixed cryoglobulinemia (MC) and non-Hodgkin's lymphoma (NHL). The causative role of HCV in these disorders is supported by the response to anti-viral treatment. The understanding of the pathophysiological process leading from HCV infection to B-cell clonal expansion has improved significantly. Data supports an antigen-driven indirect stimulation of clonal expansion model, leading from oligoclonal to monoclonal expansion and in some instances to frank malignancy. HCV-E2 antigen has been suggested as a candidate antigen as well as NS3. Binding of the B-cell receptor by viral antigens coupled with direct binding of CD-81 by HCV-E2 has been shown to provide a strong proliferative signal. Additional regulatory elements are also affected in HCV-related B-cell clonal expansion, including the Fas and BLyS signaling mechanisms. Finally, genetic events such as bcl-2 rearrangement may also be involved in clonal expansion. In this review, evidence linking HCV with MC and NHL, as well as known events in the pathophysiological process are described.