No abstract

The non-obese diabetic (NOD) mouse spontaneously develops type 1 diabetes (T1D) and has thus served as a model for understanding the genetic and immunological basis, and treatment, of T1D. Since its initial description in 1980, however, the field has matured and recognized that prevention of diabetes in NOD mice (i.e., preventing the disease from occurring by an intervention prior to frank diabetes) is relatively easy to achieve and does not correlate well with curing the disease (after the onset of frank hyperglycemia). Hundreds of papers have described the prevention of diabetes in NOD mice but only a handful have described its actual reversal. The paradoxical conclusion is that preventing the disease in NOD mice does not necessarily tell us what caused the disease nor how to reverse it. The NOD mouse model is therefore best used now, with respect to human disease, as a way to understand the genetic and immunologic causes of and as a model for trying to reverse disease once hyperglycemia occurs. We describe how genetic approaches to identifying causative gene variants can be adapted to identify novel therapeutic agents for reversing new-onset T1D.

Rheumatoid arthritis (RA) is an autoimmune disease that primarily affects the synovial joints and can lead to bone erosion and cartilage damage. One hallmark of RA is anti-citrullinated protein autoantibodies (ACPA) and memory citrulline-specific B-cells, which have been implicated in RA pathogenesis. While depletion of B-cells with Rituximab improves clinical responses in RA patients, this treatment strategy leaves patients susceptible to infections. Therefore, using Siglecengaging Tolerance-inducing Antigenic Liposomes (STALs) to selectively target the citrullinespecific B-cells may be beneficial. ACPA production from purified human RA patients' B-cells in vitro was achieved through a set stimulation conditions, which includes: BAFF, anti-CD40, IL-21, and LPS. In vivo generation of citrulline specific B-cells and ACPA production was accomplished by antigenic liposomes consisting of monophosphoryl lipid A (MPLA) and a cyclic citrullinated peptide (CCP) administered to SJL/J mice. We show that STALs that co-display a high affinity CD22 glycan ligand and synthetic citrullinated antigen (CCP STALs) can prevent ACPA production from RA patients' memory B-cells in vitro. These CCP STALs were also effective in inducing tolerance to citrullinated antigens in SJL/J mice. The results demonstrate that tolerization of the B-cells responsible for ACPA can be achieved by exploiting the inhibitory receptor CD22

CD22, a sialic-acid binding immunoglobulin type-lectin (Siglec) family member, is an inhibitory co-receptor of the B-cell receptor (BCR) with established roles in health and disease. The restricted expression pattern of CD22 on B-cells and most B-cell lymphomas has made CD22 a therapeutic target for B-cell-mediated diseases. Models to better understand how in vivo targeting of CD22 translates to human disease are needed. Here, we report development of a transgenic mouse expressing human CD22 (hCD22) in B-cells and assess its ability to functionally substitute for murine CD22 (mCD22) for regulation of BCR signaling, antibody responses, homing, and tolerance. Expression of hCD22 on transgenic murine B-cells is comparable to expression on human primary B-cells, and co-localizes with mCD22 on the cell surface. Murine B-cells expressing only hCD22 have identical calcium (Ca2+) flux responses in response to anti-IgM as mCD22-expressing WT B-cells. Furthermore, hCD22 transgenic mice on a mCD22−/− background have restored levels of marginal zone B-cells and antibody responses compared to deficiencies observed in CD22−/− mice. Consistent with these observations, hCD22 transgenic mice develop normal humoral responses in a peanut allergy oral sensitization model. Homing of B-cells to Peyer’s patches (PP) was partially rescued by expression of hCD22 compared to CD22−/− B-cells, although not to WT levels. Notably, Siglec-engaging antigenic liposomes (STALs) formulated with a hCD22 ligand were shown to prevent B-cell activation, increase cell death, and induce tolerance in vivo. This hCD22 transgenic mouse will be a valuable model for investigating the function of hCD22 and pre-clinical studies targeting hCD22.