Detailed analysis of the E2-IgM complex in hepatitis C-related type II mixed cryoglobulinaemia

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.

Vasculitis related to viral and other microbial agents

Vasculitis due to infection may occur as a consequence of the inflammation of vessel walls due to direct or contiguous infection, type II or immune complex-mediated reaction, cell-mediated hypersensitivity, or inflammation due to immune dysregulation triggered by bacterial toxin and/or superantigen production. As immunosuppressive therapy administered in the absence of antimicrobial therapy may increase morbidity and fail to effect the resolution of infection-associated vascular inflammation, it is important to consider infectious entities as potential inciting factors in vasculitis syndromes. The causality between infection and vasculitis has been established in hepatitis B-associated polyarteritis nodosa (HBV-PAN) and hepatitis C-associated (cryoglobulinemic) vasculitis (HCV-CV). The review summarizes the recent literature on the pathophysiological mechanisms and the approaches to the management of HBV-PAN and HCV-CV. Roles of other viral and microbial infections, which either manifest as vasculitic syndromes or are implicated in the pathogenesis of primary vasculitides, are also discussed.

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.

Molecular signatures of hepatitis C virus (HCV)-induced type II mixed cryoglobulinemia (MCII)

The role of hepatitis C virus (HCV) infection in the induction of type II mixed cryoglobulinemia (MCII) and the possible establishment of related lymphoproliferative disorders, such as B-cell non-Hodgkin lymphoma (B-NHL), is well ascertained. However, the molecular pathways involved and the factors predisposing to the development of these HCV-related extrahepatic complications deserve further consideration and clarification. To date, several host- and virus-related factors have been implicated in the progression to MCII, such as the virus-induced expansion of selected subsets of B-cell clones expressing discrete immunoglobulin variable (IgV) gene subfamilies, the involvement of complement factors and the specific role of some HCV proteins. In this review, we will analyze the host and viral factors taking part in the development of MCII in order to give a general outlook of the molecular mechanisms implicated.

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.

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.

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.

Membranoproliferative glomerulonephritis and mixed cryoglobulinemia after hepatitis C virus infection secondary to glomerular NS3 viral antigen deposits

BACKGROUND

We report on 3 cases of membranoproliferative glomerulonephritis associated with mixed cryoglobulin in patients with hepatitis C virus (HCV) antibodies but a negative blood viral load. These cases explore the pathogenesis of the renal disease.

METHODS

We searched for occult HCV infection in peripheral blood mononuclear cells, cryoprecipitate, bone marrow cells, and glomeruli using ultrasensitive PCR assays and immunohistochemistry. We also looked for infraclinical B cell lymphoma by computed tomodensitometry, bone marrow aspiration and biopsy, and lymphocyte typing.

RESULTS

By PCR assays, we did not evidence occult hepatitis C infection in peripheral blood mononuclear cells, bone marrow cells, or cryoprecipitates. In the only patient with available kidney specimen, we evidenced HCV-NS3 antigen in glomeruli. HCV-associated lymphoma was excluded, but mild polyclonal B lymphocytosis was present in the 3 patients. Remission occurred spontaneously in 1 patient, and in another patient it occurred after rituximab treatment. The third patient was lost to follow-up.

CONCLUSIONS

In patients with hepatitis C-negative viral load, membranoproliferative glomerulonephritis could be induced by the persistence of HCV antigen in the kidney but not in hematopoietic cells. Nonlymphomatous B cell proliferation may also be induced by chronic viral stimulation.

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.

Cryoglobulinemia

Cryoglobulinemia refers to the presence in serum of immunoglobulins that precipitate at a cold temperature. Type I cryoglobulins are single monoclonal immunoglobulins usually associated with haematological disorders. Types II and III are mixed cryoglobulins, composed of monoclonal or polyclonal IgM respectively, having rheumatoid factor activity that bind to polyclonal immunoglobulins. Mixed cryoglobulinemia (MC) syndrome is a consequence of immune-complex mediated vasculitis and is characterized by a typical clinical triad: purpura, weakness, arthralgias; many organs particularly kidney and peripheral nervous system may be involved. MC may be associated with infectious and systemic disorders and since 1990 studies have demonstrated that hepatitis C virus (HCV) may be considered the principal trigger of the disease. The relation between MC and HCV infection shows new insights in the interpretation of the link between viral infection, autoimmune phenomena and lymphoproliferative disorders evolution. In fact, the virus chronically stimulates B-cell polyclonal proliferation from which a monoclonal population may emerge. In symptomatic patients with HCV related MC therapeutic strategy should include an attempt at viral eradication. Antiviral therapy may also be effective in determining the regression of B-cell lymphoproliferative disorder. Rituximab could represent a safe and effective alternative to standard immunosuppression and exerts selective B-cell control.