IgM monoclonal gammopathy is a common age-related demyelinating sensory and motor polyneuropathy. It has been shown to be associated with antibodies against myelin-associated glycoproteins (MAG/SGPG). The HNK-1 carbohydrate epitope is a terminal 3-sulfo-glucuronyl residue attached to lactosamine structures and it is shared both in MAG and SGPG (SO4-3-GlcA(β1-3)Gal-(β1-4)GlcNAc(β1-3)Gal-(β1-4)Glcβ(1-1′)Cer). It is mostly expressed in the nervous system and plays an important role in preferential motor reinnervation. Nevertheless, the HNK-1 epitope is difficult to be isolated and synthesized and diagnostic assays used in the clinics are not always reproducible and reliable. Therefore in our study, our goal is to identify a simple synthetic diagnostic tool (peptide or monosaccharide), mimetic of the HNK-1 epitope, able to recognize antibodies in neurogammopathies sera by Surface Plasmon Resonance to be used in earlier stage patients and possibly to monitor disease activity. For this reason, we firstly tried to synthesize this trisaccharide and then we achieved the synthesis of its terminal monosaccharides with different function groups (octyl glucopyranoside, octyl glucuronic acid, octyl 3-O-sulfo-glucuronic acid and 8-amino octyl 3-O-sulfo-glucuronic acid). Then 10 linear and cyclic peptides conformationally and/or structurally mimicking HNK-1 were also synthesized (LSETTI, LSETTl, cyclo(-TTILSE-), cyclo(-TTlLSE-), cyclo(-TKTlLSE-), cyclo(-TETKlLSE-), TYTKlLSE, TY(SO3)TKlLSE, cyclo(-TYTKlLSE-) and cyclo(-TY(SO3)TKlLSE-)). The SPR kinetic binding affinities of all these sugar and peptide mimics were studied with commercial anti HNK-1 antibody using Biacore. Moreover, mimics with highest binding affinities were chosen for antigen-antibody interaction study in IgM gammopathy patients' serum.

La gammopathie monoclonale IgM est une polyneuropathie démyélinisante sensorielle et motrice. Il a été montré qu'elle est associée à des anticorps contre des glycoprotéines associées à la myéline (MAG/SGPG). L'épitope HNK-1 est un résidu 3-sulfo-glucuronyle lié à des structures lactosamine et il est présent aussi bien dans MAG que dans SGPG (SO4-3-GlcA(β1-3)Gal-(β1-4)GlcNAc(β1-3)Gal-(β1-4)Glcβ(1-1′)Cer). Il est exprimé principalement dans le système nerveux et joue un rôle important dans la réinnervation motrice préférentielle. Toutefois, l'épitope HNK-1 est difficile à isoler et à synthétiser et les essais diagnostiques cliniques ne sont pas toujours reproductibles et fiables.Le but de notre étude est d'identifier un outil synthétique simple de diagnostic (peptide ou monosaccharide), mimétique de l'épitope HNK-1, capable de reconnaître les anticorps dans les sera des neurogammapathies par Surface Plasmon Resonance (SPR) afin qu'il soit utilisé chez des patients à l'état précoce et qu'il puisse éventuellement permettre le suivi de l'évolution de la maladie. Pour cela, nous avons essayé de synthétiser ce trisaccharide, puis nous avons réalisé la synthèse de ses monosaccharides terminaux avec différents groupements fonctionnels (glucopyranoside d'octyle, acide 1-O-octylglucuronique, acide 1-O-octyl-3-O-sulfoglucuronique et acide 8-aminooctyl-3-O-sulfo-glucuronique).Puis 10 peptides linéaires et cycliques mimant conformationellement et/ou structuralement le HNK-1 ont également été synthétisés (LSETTI, LSETTl, cyclo(-TTILSE-), cyclo(-TTlLSE-), cyclo(-TKTlLSE-), cyclo(-TETKlLSE-), TYTKlLSE, TY(SO3)TKlLSE, cyclo(-TYTKlLSE-) et cyclo(-TY(SO3)TKlLSE-)). Les cinétiques d'affinité de ces mimes sucres et peptides ont été étudiées avec un anticorps anti HNK-1 commercial en utilisant le Biacore. De plus, les mimes avec les plus fortes affinités ont été choisis pour des études d'interaction antigène-anticorps dans des sera de patients atteints de gammapathie IgM. / IgM monoclonal gammopathy is a common age-related demyelinating sensory and motor polyneuropathy. It has been shown to be associated with antibodies against myelin-associated glycoproteins (MAG/SGPG). The HNK-1 carbohydrate epitope is a terminal 3-sulfo-glucuronyl residue attached to lactosamine structures and it is shared both in MAG and SGPG (SO4-3-GlcA(β1-3)Gal-(β1-4)GlcNAc(β1-3)Gal-(β1-4)Glcβ(1-1′)Cer). It is mostly expressed in the nervous system and plays an important role in preferential motor reinnervation. Nevertheless, the HNK-1 epitope is difficult to be isolated and synthesized and diagnostic assays used in the clinics are not always reproducible and reliable. Therefore in our study, our goal is to identify a simple synthetic diagnostic tool (peptide or monosaccharide), mimetic of the HNK-1 epitope, able to recognize antibodies in neurogammopathies sera by Surface Plasmon Resonance to be used in earlier stage patients and possibly to monitor disease activity. For this reason, we firstly tried to synthesize this trisaccharide and then we achieved the synthesis of its terminal monosaccharides with different function groups (octyl glucopyranoside, octyl glucuronic acid, octyl 3-O-sulfo-glucuronic acid and 8-amino octyl 3-O-sulfo-glucuronic acid). Then 10 linear and cyclic peptides conformationally and/or structurally mimicking HNK-1 were also synthesized (LSETTI, LSETTl, cyclo(-TTILSE-), cyclo(-TTlLSE-), cyclo(-TKTlLSE-), cyclo(-TETKlLSE-), TYTKlLSE, TY(SO3)TKlLSE, cyclo(-TYTKlLSE-) and cyclo(-TY(SO3)TKlLSE-)). The SPR kinetic binding affinities of all these sugar and peptide mimics were studied with commercial anti HNK-1 antibody using Biacore. Moreover, mimics with highest binding affinities were chosen for antigen-antibody interaction study in IgM gammopathy patients' serum.