Selective targeting of auto reactive B cells using bispecific molecules

Abstract Type 1 diabetes occurs when autoreactive T cells attack insulin-producing cells in pancreatic islets. B cells promote disease by acting as essential antigen presenting cells. Targeted immune therapy for treatment and prevention of autoimmune diseases is preferable to drugs that cause global immunosuppression. We therefore investigated the efficacy of three constructs designed to specifically target and neutralize anti-insulin B cells. Construct one has a 4-arm PEG backbone with insulin attached to 2 of the arms (insulin-PEG). Construct two has insulin attached to 2 of the PEG arms and a trisaccharide molecule that acts as a ligand for inhibitory receptor CD22 on the remaining 2 PEG arms (insulin-PEG-CD22L). Construct three consists of insulin directly conjugated to CD22L (insulin-CD22L). In vitro experiments using transgenic anti-insulin B cells demonstrate that insulin-PEG unexpectedly promotes excessive proliferation and upregulation of CD86 in anti-CD40 treated anti-insulin B cells. Addition of CD22L (insulin-PEG-CD22L) restores anti-insulin B cell responses to baseline but has no overall benefit. Conversely, insulin-CD22L blunts the effects of anti-CD40 stimulation, reducing proliferation by 15% and IgM surface expression by 50% . CD22L alone has no effect on stimulated anti-insulin B cells. Preliminary in vivo data using 2-photon imaging shows that insulin-CD22L binds anti-insulin B cells in spleen, pancreatic lymph nodes and pancreatic islets within 30 minutes of injection. Thus, this novel insulin-CD22L construct directs the dampening effect of CD22 specifically to anti-insulin B cells that promote T1D, making it a promising therapeutic intervention that may also be useful when paired with anti-T cell treatments. P20GM1133117 T32GM008545 5T32AI7163-43