Exploiting CD22 on antigen-specific B-cells to prevent allergy to the major peanut allergen Ara h 2

Authors: ORGEL, KELLY - University Of North Carolina; DUAN, SHITENG - Scripps Institute; WRIGHT, BENJAMIN - University Of North Carolina; Maleki, Soheila; Wolf, John; VICKERY, BRIAN - University Of North Carolina; BURKS, WESLEY - University Of North Carolina; PAULSON, JAMES - Scripps Institute; KULIS, MIKE - University Of North Carolina; MACAULEY, MATTHEW - University Of North Carolina

Submitted to: Journal of Allergy Clinical Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2017
Publication Date: 1/1/2018
Citation: Orgel, K.A., Duan, S., Wright, B.L., Maleki, S.J., Wolf, J.C., Vickery, B.P., Burks, W., Paulson, J.C., Kulis, M.D., MaCauley, M.S. 2018. Exploiting CD22 on antigen-specific B-cells to prevent allergy to the major peanut allergen Ara h 2. Journal of Allergy Clinical Immunology. 139:366-369.e2. https://doi.org/10.1016/j.jaci.2016.06.053.
DOI: https://doi.org/10.1016/j.jaci.2016.06.053

Interpretive Summary: Oral, sublingual, and epicutaneous immunotherapies are under clinical study as potential food allergy therapies, yet the side effects, requirement for daily dosing, and lack of prolonged efficacy remain limitations in these human trials.[1, 2] Targeting the allergenspecific B-cells may limit side effects and promote long-term tolerance. Sialic acid-binding immunoglobulin-type lectins (Siglecs) are a family of immunomodulatory receptors with cell-specific expression.[3] Inhibitory Siglecs, including CD22 expressed on B-cells, use immunoreceptor tyrosine-based inhibitory motifs (ITIMs) to suppress activatory receptors, such as the B-cell Receptor (BCR). Enforcing co-localization of CD22 with the BCR, with liposomes that co-display an antigen and high affinity CD22 ligand, not only prevents B-cell activation but also induces apoptosis of the antigen-reactive B-cells, resulting in robust immunological tolerance due to depletion of the antigen-specific B-cells from the B-cell repertoire.[4] These Siglec-engaging Tolerance-inducing Antigenic Liposomes (STALs) can be formulated with any antigen of choice. STALs displaying Factor VIII (FVIII) inhibit antibody responses to exogenous FVIII, preventing bleeding in FVIII-/- mice.[4] Accordingly, STALs have the potential to prevent undesired B-cell responses and we were motivated to examine their potential for inducing immunological tolerance to a food allergen.

Technical Abstract: A schematic representing the experimental design is shown in Figure 1B. All animal studies were approved by the UNC IACUC and investigated under protocol # 13-216.0. Four-week old female BALB/cJ mice (Jackson Laboratories, Bar Harbor, Maine) were injected intravenously with 200 µL of 100 µM Ah2 STALs (n=8), 300 µM Ah2 STALs (n=8), 100 µM immunogenic Ah2 liposomes (n=8), or 300 µM immunogenic Ah2 liposomes (n=7). All liposomes consisted of 0.03 mol % Ah2, which amounted to a dose of 0.12 µg of Ah2 in the 100 µM group. STALs additionally consisted of 1% BPA-Neu5Gc, the high affinity and selective CD22 ligand.[4] Two weeks following infusion of STALS, a timeframe previously determined to maximize tolerance induction through STALs [4], the mice were orallysensitized, with 2 mg WPE and 10 µg Cholera toxin (CT) weekly for three weeks followed by a boost dose of 5 mg WPE and 10 µg CT. A group of naïve mice (n=8) underwent the same protocol and were injected with PBS to determine baseline titers. Serum was collected one week later to quantify specific IgE (sIgE) and sIgG1 to Ah2, WPE, Ah1, and CT by ELISA.[6] Mice were initially challenged with 200 µg Ah2 via an intraperitoneal (i.p.) injection. One week later, mice were challenged i.p. with 750 µg WPE. To assess anaphylaxis during challenge, rectal temperatures were recorded for 30 minutes, and symptom scores were documented at 30 minutes using a 0-5 point scale where 0 represents no symptoms and 5 represents death, as described previously.[6] All methods are described in detail in the online repository material.