Saint Louis University

Tick bite-related meat allergy as a cause of chronic urticaria, angioedema, and anaphylaxis in endemic areas.

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

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. 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. 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. 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.

Recognition by the glycoprotein hormone-specific N-acetylgalactosaminetransferase is independent of hormone native conformation.

Some members of the glycoprotein hormone family [luteinizing hormone (LH), thyroid-stimulating hormone (TSH), and free alpha subunit] bear unique asparagine-linked oligosaccharides with the terminal sequence SO4-Gal-NAc beta 1,4GlcNAc beta 1,2Man alpha, whereas other members [human chorionic gonadotropin (hCG) and follicle-stimulating hormone (FSH)] bear predominantly oligosaccharides terminating in the sequence sialic acid alpha-Gal beta 1,4GlcNAc beta 1,2Man alpha. We previously identified an N-acetylgalactosaminetransferase (GalNAc-transferase) in bovine pituitary membranes that specifically recognizes the alpha subunit peptide and adds GalNAc to the synthetic intermediate GlcNAc2Man3GlcNAc2. In the current study we demonstrate that bLH, hCG, hCG beta, hCG alpha, and FSH alpha are recognized by the pituitary GalNAc-transferase in vitro, whereas oFSH, hFSH, and hFSH beta are not (b-, h-, and o-indicate bovine, human, and ovine). The apparent Km values for addition of GalNAc to oligosaccharides on hCG alpha and hCG beta, 13.0 and 6.2 microM, respectively, are not altered by reduction and alkylation. Thus, recognition of the peptide determinant does not require maintenance of native tertiary structural features. In the presence of the recognition determinant the Km for addition of GalNAc to the intermediate GlcNAc2Man3GlcNAc2 is reduced from 1.2-2.6 mM to less than 13 microM. hFSH is not efficiently recognized by the GalNAc-transferase due to the absence of the recognition marker on hFSH beta and some degree of masking of the recognition marker on the alpha subunit when combined with FSH beta. Since recognition is directed at primary and possibly secondary structural features, it should be possible to determine which regions of the alpha and beta subunits are responsible for the specificity of the GalNAc-transferase.