Hepatitis C virus-related liver damage is related to cold activation of complement

Complement activation correlates with liver necrosis and fibrosis in chronic hepatitis C

Chronic hepatitis C viral infection modulates complement. The aim of this study was to determine whether complement analysis predicts liver inflammation and fibrosis in patients with chronic hepatitis C. 50 chronic hepatitis C patients who underwent a liver biopsy were compared to 50 healthy controls and 35 patients with various liver diseases. Total plasma complement activity (CH50) in plasma was diminished in hepatitis C patients suggesting complement activation. This decrease correlated with increased necrosis (r = -0.24, p < 0.05), and patients with levels below the normal range had a higher METAVIR activity score reflecting enhanced inflammation. SC5b-9, a marker of complement activation, correlated with inflammation (r = 0.40, p < 0.05), activity (r = 0.42, p < 0.05), and fibrosis scores (r = 0.49, p < 0.05). Finally, the prevalence of C1q auto-antibodies was higher in hepatitis C patients, and their presence was associated with increased inflammation and seemed to affect fibrosis. We conclude that complement-induced liver inflammation contributes to fibrosis in patients with chronic hepatitis C.

Hepatitis C virus proteins inhibit C3 complement production

The third component of human complement (C3) plays a central role in innate immune function as its activation is required to trigger classical as well as alternative complement pathways. In this study, we have observed that sera from patients chronically infected with hepatitis C virus (HCV) displayed significantly lower C3 levels than sera from healthy individuals. Liver biopsy specimens from the same patients also exhibited lower C3 mRNA expression than liver tissues from healthy donors. C3 mRNA level was reduced in hepatocytes upon infection with cell culture-grown HCV genotype 1a or 2a in vitro. Further analysis suggested that HCV core protein displayed a weak repression of C3 promoter activity by downregulating the transcription factor farnesoid X receptor (FXR). On the other hand, HCV NS5A protein strongly downregulated C3 promoter activity at the basal level or in the presence of interleukin-1β (IL-1β) as an inducer. In addition, the expression of the transcription factor CAAT/enhancer binding protein beta (C/EBP-β), which binds to the IL-1/IL-6 response element in the C3 promoter, was inhibited in liver biopsy specimens. Furthermore, expression of C/EBP-β was reduced in hepatocytes infected with cell culture-grown HCV, as well as in hepatocytes transfected with the NS5A genomic region of HCV. Together, these results underscore the role of HCV NS5A protein in impairing innate immune function.

Complement activation and disease: protective effects of hyperbilirubinaemia

Complement, an important effector mechanism of the immune system, is an enzymatic cascade of approx. 30 serum proteins leading to the amplification of a specific humoral response. It can be activated through the classical or alternative pathways, or through the mannose-binding lectin pathway. The activation of the classical pathway is initiated by the binding of the C1 component to antigen-bound antibodies, known as immunocomplexes. C1 is a complex of one molecule of C1q, two molecules of C1r and two molecules of C1s. C1q contains three copies of a Y-shaped fundamental unit with globular heads included in its structure, which play a major role in the interaction with the Fc portion of immunoglobulins. Deficient or exacerbated activation of the complement system leads to diseases of variable severity, and pharmacological inhibition of the complement system is considered as a therapeutic strategy to ameliorate the inflammatory effects of exacerbated complement activation. Bilirubin is a product of haem degradation by the concerted action of haem oxygenase, which converts haem into biliverdin, and biliverdin reductase, which reduces biliverdin to UCB (unconjugated bilirubin). UCB exerts both cytoprotective and cytotoxic effects in a variety of tissues and cells, acting either as an antioxidant at low concentrations or as an oxidant at high concentrations. In the present review, we describe in detail the anti-complement properties of bilirubin, occurring at levels above the UCB concentrations found in normal human serum, as a beneficial effect of potential clinical relevance. We provide evidence that UCB interferes with the interaction between C1q and immunoglobulins, thus inhibiting the initial step in the activation of complement through the classical pathway. A molecular model is proposed for the interaction between UCB and C1q.

Hepatitis C, cryoglobulinemia, and cirrhosis: a meta-analysis

Approximately 40% of patients with chronic hepatitis C virus (HCV) infection develop detectable serum cryoglobulins or cryoprecipitates (CP), although most do not show clinical or physical signs of syndromic cryoglobulinemia. Although association of HCV with the extrahepatic complications of cryoglobulinemia is widely recognized, the relationship of cryoglobulinemia with liver disease is unclear. We wished to study the relationship between CP and cirrhosis and to determine whether the development of CP is a true covariate for progressive liver disease or a confounding variable that impacts cirrhosis because of patient age, duration of disease, or differences in gender. We undertook a meta-analysis of 19 studies published between 1994 and 2001. The incidence of cirrhosis was compared in patients with and without CP after logistic regression adjustments for accepted risk factors for progressive liver disease, including age, gender, and estimated duration of disease (EDD). A total of 2,323 patients with chronic hepatitis C were identified, with 1,022 (44%) having detectable CP. Cirrhosis was present in 40% of patients with CP but only 17% of patients without CP (total Chi;(2) = 141.69, P <.001). After adjusting for age, gender, and estimated duration of disease by logistic regression, the combined odds ratio for incidence of cirrhosis in patients CP positive versus CP negative was 4.87, (95% CI: 3.32, 7.15), indicating a highly significant association between cirrhosis and cryoglobulinemia. In conclusion, cryoglobulins may be a useful prognostic indicator for increased risk of cirrhosis with chronic hepatitis C.

Changes in the acute phase complement component and IL-6 levels in patients with chronic hepatitis C receiving interferon alpha-2b

In order to study the effect of interferon alpha on the levels of acute phase complement proteins in vivo, serum concentrations of C9 and C1-inhibitor (C1-INH) were measured in patients with chronic hepatitis C before and 3 months after the beginning of interferon alpha2b therapy. Serum levels of the activation product of terminal complement pathway, C5b-9, HCV RNA and IL-6 were also determined. IFN alpha treatment significantly (P<0.0001) increased the serum concentrations of both complement proteins. C5b-9 levels were found to significantly decrease during the same period of time. When the patients were divided into responders or non-responders (more or less than 50% decrease in plasma HCV RNA concentrations) C9 and C1-INH levels were elevated only in the responder patients. There was no correlation between the changes of IL-6 levels or the amounts of IFN alpha administrated on one hand, and the changes in the complement protein levels on the other. These findings suggest that the marked increase in the serum concentrations of the acute phase complement proteins is a secondary phenomenon due to the IFN alpha-caused diminution of the viral load and the resulting immune complex-induced complement activation.

Evaluation of cryoglobulins

Cryoglobulins are immunoglobulins that precipitate as serum is cooled below core body temperatures. A cryoglobulin screen is the observation of a serum specimen collected and separated while warm for cryoprecipitation over a period of up to 7 days. Values of the screening may be reported as a cryocrit, which is the volume percent of the precipitate compared with the total volume of serum. Further proof that the precipitate is indeed a cryoglobulin can be obtained by demonstrating resolubilization with warming and immunochemical analysis by immunofixation. Detailed characterization of cryoglobulins may also require rigorous washing of the precipitate, quantitation of total protein and immunoglobulins, and evaluation of serum for monoclonal gammopathy, rheumatoid factor activity, evidence of complement activation, and presence of hepatitis C virus seroreactivity or hepatitis C virus RNA. The single most important variable confounding standardization of cryoglobulin testing is the frequently improper separation of warm serum from other blood elements prior to screening and characterization.