Targeting Siglec-10 in autoimmunity and inflammation

Thesis

Autoimmunity is defined as a loss of immunological tolerance and the inappropriate attack of ‘self’, which can arise due to a combination of genetic and environmental triggers. Despite advances in the development of new therapies for autoimmune disease, there is a still a requirement for more specific, targeted approaches. One newly recognised strategy is the development of antibody agonists to checkpoint receptors to inhibit immune cell activation. One such inhibitory immunoreceptor, Siglec-10, represents a novel target for agonistic antibodies and is yet to be fully explored in this context. Siglec-10 is highly expressed on the surface of non-classical monocytes and the receptor possesses two intracellular ITIM motifs to mediate inhibitory signalling function.

In this thesis, a diverse panel of antibodies targeting Siglec-10 were generated and characterised. Functional assessment in vitro and in vivo using a human Siglec-10 knock-in mouse model showed that bivalent antibodies targeting Siglec-10 are limited by rapid internalisation, which is likely triggered by clustering of receptor dimers at the cell surface. Monovalent Siglec-10 antibodies showed reduced internalisation and induced dose-dependent inhibitory signalling in reporter and primary B cell activation assays. The greater surface residency of monovalent Siglec-10 antibodies was subsequently translated to effective target cell depletion in vivo. To an extent, these findings were also applicable to Siglec-2, however, factors such as internalisation following FcR mediated cross-linking and the mechanism of antibody depletion can impact the suitability of a monovalent antibody approach.

Given the potentially pathogenic function of non-classical monocytes in autoimmune disease, the work described in this thesis provides a means to determine whether the inhibition or depletion of non-classical monocytes in autoimmunity is a valid therapeutic approach. More broadly, this work will inform future antibody development against other dimeric receptors impacted by antibody-induced internalisation.

Authors: Matthews, M

• DOI: 10.5287/ora-qya0oy2pr
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English