The roles of anti-GM1 complex antibodies in autoimmune neuropathies

Meehan, Gavin Robertson (2015) The roles of anti-GM1 complex antibodies in autoimmune neuropathies. PhD thesis, University of Glasgow.

Abstract

Anti-ganglioside antibodies have been implicated in autoimmune neuropathies
for several decades. They are thought to elicit injury through binding to sites in
the peripheral nervous system, where they activate the complement pathway to
induce cell death. Patient serum is therefore regularly screened for these
antibodies to aid in the diagnosis of various conditions. Recent work has found
that complexes composed of gangliosides and other glycolipids can improve the
detection of these antibodies beyond the signals detected to the single
ganglioside species.
In MMN research, complexes comprised of GM1 and GalC have been found to
significantly enhance antibody detection in patient sera. In certain patients,
however, antibody binding was only detected against these complexes and not
the single antigens. This led some researchers to hypothesise that an
unidentified class of antibody may have arisen that binds specifically to a neoepitope
formed by the combination of the two glycolipids. It has also been
hypothesised that that this complex may be the true target of immune mediated
attack in MMN.
This thesis sought to address this hypothesis by either cloning these antibodies
directly from patient serum or through active immunisations with mice. Analysis
of previously generated human monoclonal antibodies indicated that their
behaviours were modified by complexes containing particular gangliosides or
glycolipids. Furthermore, the antibodies behaviours were found to diverge, when
they were screened against complexes comprised of gangliosides and different
concentrations of accessory lipids. These findings suggested that the accessory
lipids were interacting with the ganglioside headgroups to modify the
presentation of different binding epitopes. This indicated that conformational
modulation, rather than neo-epitope formation, may be responsible for complex
enhancement
Cloning antibodies from patient sera was unsuccessful but examination of the
screening techniques suggested that the appearance of complex-dependent
antibodies may have been an artefact. Attempts to induce complex-specific
responses in mice were similarly unsuccessful but several anti-ganglioside and
anti-sulfatide antibodies were created. The subsequent chapters focused on the
characterisation of these antibodies and indicated that most of them bound well
to solid-phase assays, cells and tissue and may therefore be of use in future
studies.
Taken together, the data from this thesis suggests that complex-dependent
antibodies may not exist but are merely low concentrations of anti-ganglioside
antibodies that are cis-enhanced by particular lipids. Future work should
therefore focus on assessing how the ganglioside microenvironment modifies
epitope presentation and how this affects the binding capabilities of antiganglioside
antibodies.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Autoimmune, neuropathy, multifocal motor, sulfatide, GM1, ganglioside, Guillain-Barre syndrome, antibody, complex, concentration, dependent, independent, BO1, BO3, BR1, DO1, SM1, WO1, GAME, GAME-M2, GAME-M5, GAME-M6, GAME-M7, GAME-G1, GAME-G3
• Subjects: Q Science > QR Microbiology > QR180 Immunology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Funder's Name: Guillain-Barre Support Group of the United Kingdom (GUILL)
• Supervisor's Name: Willison, Professor Hugh
• Date of Award: 2015
• Depositing User: Mr Gavin Robertson Meehan
• Unique ID: glathesis:2015-7145
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 10 Mar 2016 12:00
• Last Modified: 25 Mar 2016 13:39
• URI: https://theses.gla.ac.uk/id/eprint/7145