GLYCOBIOLOGY AND MEDICINE Proceedings of the 7th Jenner Glycobiology and Medicine Symposium

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GLYCOBIOLOGY AND MEDICINE

Proceedings of the 7th Jenner Glycobiology and Medicine Symposium

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ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY

Editorial Board:

NATHAN BACK, State University of New York at Buffalo IRUN R. COHEN, The Weizmann Institute of Science DAVID KRITCHEVSKY, Wistar Institute

ABEL LAJTHA, N. S. Kline Institute for Psychiatric Research RODOLFO PAOLETTI, University of Milan

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UPDATES IN PATHOLOGY

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GLYCOBIOLOGY AND MEDICINE Edited by John S. Axford Volume 565

SLIDING FILAMENT MECHANISM IN MUSCLE CONTRACTION: FIFTY YEARS OF RESEARCH

Edited by Haruo Sugi Volume 566

OXYGEN TRANSPORT TO TISSUE XXVI

Edited by Paul Okunieff, Jacqueline Williams, and Yuhchyau Chen Volume 567

THE GROWTH HORMONE-INSULIN-LIKE GROWTH FACTOR AXIS DURING DEVELOPMENT

Edited by Isabel Varela-Nieto and Julie A. Chowen Volume 568

HOT TOPICS IN INFECTION AND IMMUNITY IN CHILDREN II Edited by Andrew J. Pollard and Adam Finn

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Edited by David C. Chieng and Gene P. Siegal

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GLYCOBIOLOGY AND MEDICINE

Proceedings of the 7th Jenner Glycobiology and Medicine Symposium

Edited by

John S. Axford

St George’s, University of London, UK t

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INTRODUCTION

7th Jenner Glycobiology and Medicine Symposium Sunday 5 – Wednesday 8 September 2004 W W

John S. Axford

The potential for glycobiology to improve the practice of medicine has been well recognised, which is why biannual meetings concerning the association have been taking place for the last 14 years. The science of glycobiology has matured rapidly, and with it the far reaching clinical implications are becoming understood. The next decade is going to see this ﬁnal frontier of science conquered. The impact this understanding of glycobiology will have upon our practice of medicine is going to be exciting. The 7th Jenner Glycobiology and Medicine Symposium was designed to reﬂect these advances. All the major clinical areas were involved, with contributions from pivotal players in science and medicine.

As with our previous meetings, junior scientists were involved as we recognise that at the end of the next decade they will be in the driving seat. This introduction serves as a taster to whet your appetite.

From embryogenesis to pathogenesis, glycosylation plays a pivotal role.

Complex and hybrid N-glyans and O-fucose glycans are critical in oocyte development and function. This area must surely be a fertile ground for glycosylation research.

The pathogenesis of viral infections involves sugars at every turn. Hepatitis C virus and Bovine viral diarrhoea virus are diseases that are opening themselves to scrutiny. The BVDV has proven very useful in the evaluation of the antiviral activity of molecules that inhibit morphogenesis and/or viral entry. Infection by human immunodeﬁciency virus type-1 is characterised by low levels of neutralising antibod- ies. One broadly neutralising human monoclonal antibody is 2G12.This has 3 possible combining sites and recognises a cluster of oligomannose residues on the

‘‘immunologically silent’’ face. This recognition provides exciting challenges for immunogen design.

v John S. Axford (ed.), Glycobiology and Medicine, v-viii.

St George’s, University of London, UK

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vi J. S. Axford

N- and O-linked glycosylation of enveloped glycoproteins permits Ebola virus binding to host cells. It is thought that an alternative pathway to the calnexin- calreticulin folding and quality control pathway is being used by the viral glycoproteins.

Immune mechanisms will be a major focus for clinical intervention over the next decade. This will involve modulation of both the innate and adaptive immune defences.

The innate immune system provides the ﬁrst line of defence to invading pathogens, and recognition of pathogens governs the induction, and type of pathogen- speciﬁc adaptive responses.

Schistosomiasis is a major tropical parasitic disease. Recently several antigen presenting cell-associated lectins, that show interaction with egg glycoproteins of S.

mansoni, such as the dendritic cell-speciﬁc DC-SIGN, L-SIGN on liver sinusoid endothelial cells, MGL (macrophage galactose-type lectin) and galectin 3, have been identiﬁed. Since their glycan ligands occur on many parasitic helminths, that they may constitute parasite patterns for lectin-mediated immune recognition. For example, Lex interacts with DC-SIGN on dendritic cells and it is thought that this interaction may play a role in triggering dendritic cells s to mount to a Th2 response.

Mannan binding lectin (MBL) is an oligomeric protein designed to recognize pathogen-associated molecular patterns. The biological importance of MBL was indicated when opsonin-deﬁcient children with recurrent infections were found to be genetically deﬁcient in MBL. Further interest in this molecule was sparked by the observation of complement activation upon binding to carbohydrates. Glycosylation is now known to play a central role in the MBL pathway of complement activation and the glycosylation of the mannose receptor determines its functional specialisation.

Glycan structures that can act as potential ligands for MBL have been identiﬁed on all the immunoglobulins. In human serum only IgG-G0 and polymeric and dimeric IgA have been shown to bind MBL and initiate the lectin pathway of complement. This is thought to occur through GlcNAc-terminating glycan structures.

Disease associations with sugar changes are plentiful, when the adaptive immune system is considered. This may involve fundamental processes, for example glycosylation related molecular mechanisms are thought to involve the function of the T cell co-receptor CD8; which will have far reaching implications if abnormal.

Sugar associations with cancer have been recognised for some time. There continues to be new data concerning ovarian cancer and arthritis, but research is expanding into new areas. Sugars have now been shown to be associated with the pathological mechanism associated with the GPI anchorage of the prion protein, pigeon fanciers’ lung and muscular dystrophy.

At least six different forms of muscular dystrophy are caused by genes thatffff encode glycosyltransferases, and when malfunctioning result in a secondary deficiency in the glycosylation of dystroglycan.

Autoimmune arthritis has been associated with the generation of remnant glyco- epitopes by gelatinase B.gelatinase B/matrix metalloproteinase-9, which is an inflammatory mediator and effector. Considerable amounts of gelatinase B areffff released by neutrophils in the synovial cavity of patients with rheumatoid arthritis.

This is thought to be linked to the pathogenesis of arthritis as gelatinase B-deﬁcient mice are resistant to antibody-induced arthritis. Determination of T-cell reactivity

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Introduction vii

against the gelatinase B-cleaved fragments of collagen II indicates that, there are many glyco-epitopes present in collagen II, which reinforces the role of glycopeptide antigens in autoimmunity.

It is however always exciting when clinical anecdotes translate into therapeutic and diagnostic possibilities. Glycobiology is at that transition.

Once disease mechanisms have been understood, the next step is to determine whether this information can be used to devise therapeutic options. Predictably, therapeutic hypotheses are plentiful. For example, there is a possibility that polysaccharide may be used to block skin inﬂammation.

There have been new developments in treating glycosphingolipid storage diseases. This may not be a common group of diseases, but for those that have it this opens the door to improved quality of life.

The glycosphingolipid lysosomal storage diseases result from defects in glycosphingolipid catabolism. They are progressive disorders, the majority of which involve storage and pathology in the central nervous system. A new approach to treatment is substrate reduction therapy (SRT), using small molecule inhibitors to reduce the rate of glycosphingolipid biosynthesis, to offset the catabolic defect. Oneffff of these drugs, NB-DNJ has recently been approved for clinical use in type 1 Gaucher disease, following a successful clinical trial. There is also the potential of combining SRT with drugs that target the downstream consequences of storage.

RA is a common disorder where the available diagnostic tests eg rheumatoid factor, anti-citrulinated cyclic peptide, lack sensitivity. The diagnostic potential of IgG glycosylation has been previously discussed and we await the results from prospective trials.

Indeed, abnormal galactosylation of polyclonal IgG in ANCA associated sys- temic vasculitis patients has now been reported and the diagnostic potential of this technology for other autoimmune rheumatic diseases is signiﬁcant.

Experiments looking at the cause behind these sugar changes indicate both quantitative and qualitative changes in the RA serum GTase isoform profile. This is likely to be due to a greater proportion of hypersialylated isoforms, which have the potential to adversely affect the catalytic activity of the enzyme, thus providing affff possible mechanism for post-translational regulation of GTase activity in RA. It also provides further evidence that RA glycosylation changes may be more general than previously indicated and encompass proteins other than IgG. These observations can only strengthen the potential of sugars as RA disease biomarkers.

The selectin family of adhesion molecules mediates the initial attachment of leukocytes to venular endothelial cells at sites of tissue injury and inflammation. For example in staphylococcal arthritis. Fucoidin, a sulfated polysaccharide from sea- weed, binds to and blocks the function of L-and P-selectins thereby inhibiting leukocyte rolling and adhesion to endothelial surface. Treatment with fucoidin has been shown to reduce the severity of septic arthritis within the first three days following bacterial infection. It is suggested that the efficient treatment of septic arthritis should encompass a combination of antibiotics and immunomodulation.

Gastroenterologists want to know more about normal and abnormal bacteria that inhabit our bowels. O-acetyl sialic acid expression in colorectal mucosa has been shown to be regulated by enteric microﬂora; as demonstrated by the loss of sialic acid oligo-O acetylation after elimination of the faecal ﬂow. There is therefore

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viii J. S. Axford

potential to use this observation to quantitate bacterial colonisation and perhaps interfere with disease associated pathology.

Biological therapies will be the new treatments of the next decade. The impact of glycosylation on the structure and function of natural and recombinant (therapeutic) IgG antibody is therefore important to get to grips with.

It has been shown that the in vivo micro-environment can have a profound influence on the glycosylation profile of IgG-Fc. This may reflect the unique structural relationship between the oligosaccharide and the protein. The ‘‘core’’ heptasaccharide is essential for FccRI, FccRII, FccRIII and C1 activation whilst outer arm sugar residues can influence these and other functions, e.g. FccRIII, FcRn, MBL, MR.

Thus, fidelity of glycosylation is essential to the effector function profile of antibodiesffff and in the future the oligosaccharide will be used to function as a structural ‘‘rheostat’’

to generate specific glycoforms exhibiting optimal effector activities for a particularffff disease target.

Cellular glycoengineering for fully human glycosylation and optimised sialylation of proteins is therefore going to be important if these molecules are going to be fully and specifically active. Most pharmaceutical proteins are expressed in bacteria, yeast or mammalian cells resulting in proteins lacking glycosylation or carrying glycans which largely differ from human carbohydrate chains in various aspectsffff including sialylation. However, relationships between the N-glycan structures and biological activities of, for example, recombinant human erythropoietins produced using different culture conditions and purification procedures are now better under-ffff stood. It is nevertheless apparent that novel glycoprotein expression technology will need to be developed to address this problem and data is now available to demon- strate how this can be done.

The above introduction adds up to the fact that Glycobiology is an extremely exciting science to be involved in. Additionally, if you are a clinician, it is even more gripping as you will be at the forefront of important clinical developments.

I hope these proceedings stimulate you as much as they have me and I look forward to seeing you at Jenner 8!

REFERENCES

Axford J Keida C Van Dijk WV, Rudd PM. 6th Jenner Glycobiology and Medicine. CPD Bulletin.

Immunology & Allergy 2004; 3(3): 84–87.

Alavi A, Axford J. Glycobiology of the Rheumatic Diseases: an update. Adv Exp Med Biol. 2003; 535:

271–80.

Axford J, Keida C & Dikk WV. Meeting Report 5th Jenner Glycobiology and Medicine. Glycobiology 2001; 11(2): 5G-7G.

Axford JS. 4th Jenner International Glycoimmunology Meeting: A Review. Immunol Today 1997; 18(11):

511–513.

Axford JS. 3rd Jenner International Glycoimmunology Meeting. Immunol Today 1995; 16(5):213–215.

Axford JS. 2nd Jenner International Glycoimmunology Meeting. Immunol Today 1993; 14(3): 104–106.

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GLYCOBIOLOGY AND MEDICINE Proceedings of the 7th Jenner Glycobiology and Medicine Symposium

GLYCOBIOLOGY AND MEDICINE

GLYCOBIOLOGY AND MEDICINE

Proceedings of the 7th Jenner Glycobiology and Medicine Symposium

John S. Axford

INTRODUCTION

7th Jenner Glycobiology and Medicine Symposium Sunday 5 – Wednesday 8 September 2004 W W

CONTENTS