Altered functionality of anti-bacterial antibodies in patients with chronic hepatitis C virus infection.

BACKGROUND: Using comparative glycoproteomics, we have previously identified a glycoprotein that is altered in both amount and glycosylation as a function of liver cirrhosis. The altered glycoprotein is an agalactosylated (G0) immunoglobulin G molecule (IgG) that recognizes the heterophilic alpha-gal epitope. Since the alpha gal epitope is found on gut enterobacteria, it has been hypothesized that anti-gal antibodies are generated as a result of increased bacterial exposure in patients with liver disease. METHODS: The N-linked glycosylation of anti-gal IgG molecules from patients with fibrosis and cirrhosis was determined and the effector function of anti-bacterial antibodies from over 100 patients examined. In addition, markers of microbial exposure were determined. RESULTS: Surprisingly, the subset of agalactosylated anti-gal antibodies described here, was impaired in their ability to mediate complement mediated lysis and inhibited the complement-mediated destruction of common gut bacteria. In an analysis of serum from more than 100 patients with liver disease, we have shown that those with increased levels of this modified anti-gal antibody had increased levels of markers of bacterial exposure. CONCLUSIONS: Anti-gal antibodies in patients with liver cirrhosis were reduced in their ability to mediate complement mediated lysis of target cells. As bacterial infection is a major complication in patients with cirrhosis and bacterial products such as LPS are thought to play a major role in the development and progression of liver fibrosis, this finding has many clinical implications in the etiology, prognosis and treatment of liver disease.

Increased levels of tetra-antennary N-linked glycan but not core fucosylation are associated with hepatocellular carcinoma tissue.

BACKGROUND: Alterations in glycosylation have long been associated with the development of cancer. In the case of primary hepatocellular carcinoma (HCC), one alteration that has often been associated is increased amounts of fucose attached to the N-glycans of serum proteins secreted by the liver. METHODS: In an effort to determine the origin of this increased fucosylation, we have conducted N-linked glycan analysis of HCC tissue, the surrounding nontumor tissue, and compared this to tissue from a nondiseased adult liver. RESULTS: Surprisingly, no difference in the level of fucosylation was observed from the three donor groups, suggesting that the increased levels of fucosylation observed in serum of those with HCC is not the result of increased synthesis of fucosylated proteins in the cancer tissue. On the other hand, increased levels of a tetra-antennary glycan were observed in the HCC tissue as compared with the surrounding tissue or to the nondiseased livers. CONCLUSIONS: This represents, to our knowledge, one of the first reports associating increased levels of branching with the development of HCC. IMPACT: The identification of increased levels of tetra-antennary glycan on liver tumor tissue, as opposed to adjacent or nondiseased tissue may lead to improved detection of HCC.

Novel changes in glycosylation of serum Apo-J in patients with hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and the occurrence of HCC has more than doubled in the United States in the past decade. Early detection is considered key to reducing the mortality of HCC. METHODS: Using two-dimensional gel electrophoresis and high-performance liquid chromatography we have analyzed the glycosylation of Apo-J from healthy controls, patients with liver cirrhosis, or those with HCC. RESULTS: Apo-J in the serum from patients with HCC had decreased levels of (ß-1,4) triantennary N-linked glycan compared with the healthy controls or patients with liver cirrhosis. We analyzed this change in an independent cohort of 76 patients with HCC, 32 with cirrhosis, and 43 infected with hepatitis C virus using the Datura stramonium lectin (DSL), which binds to (ß-1,4) triantennary N-linked glycan. The level of DSL-reactive Apo-J allowed us to differentiate HCC from cirrhosis with an area under the receiver operating characteristic curve (AUROC) of 0.852. When Apo-J was combined with other serum biomarkers such as α-fetoprotein (AFP) and fucosylated kininogen by using a multivariate logistic regression model, the AUROC increased to 0.944, a value much greater than that observed with AFP alone (AUROC of 0.765). CONCLUSIONS: The glycosylation of Apo-J is a useful marker when used alone or in combination with outer makers for the early detection of HCC. IMPACT: The potential use of a combination of AFP, DSL-reactive Apo-J, and fucosylated kininogen as a biomarker of HCC would have great value in the management of patients with liver disease.

Linkage specific fucosylation of alpha-1-antitrypsin in liver cirrhosis and cancer patients: implications for a biomarker of hepatocellular carcinoma.

BACKGROUND: We previously reported increased levels of protein-linked fucosylation with the development of liver cancer and identified many of the proteins containing the altered glycan structures. One such protein is alpha-1-antitrypsin (A1AT). To advance these studies, we performed N-linked glycan analysis on the five major isoforms of A1AT and completed a comprehensive study of the glycosylation of A1AT found in healthy controls, patients with hepatitis C- (HCV) induced liver cirrhosis, and in patients infected with HCV with a diagnosis of hepatocellular carcinoma (HCC). METHODOLOGY/PRINCIPAL FINDINGS: Patients with liver cirrhosis and liver cancer had increased levels of triantennary glycan-containing outer arm (alpha-1,3) fucosylation. Increases in core (alpha-1,6) fucosylation were observed only on A1AT from patients with cancer. We performed a lectin fluorophore-linked immunosorbent assay using Aleuria Aurantia lectin (AAL), specific for core and outer arm fucosylation in over 400 patients with liver disease. AAL-reactive A1AT was able to detect HCC with a sensitivity of 70% and a specificity of 86%, which was greater than that observed with the current marker of HCC, alpha-fetoprotein. Glycosylation analysis of the false positives was performed; results indicated that these patients had increases in outer arm fucosylation but not in core fucosylation, suggesting that core fucosylation is cancer specific. CONCLUSIONS/SIGNIFICANCE: This report details the stepwise change in the glycosylation of A1AT with the progression from liver cirrhosis to cancer and identifies core fucosylation on A1AT as an HCC specific modification.