Unwanted antibody responses significantly impact human health, and current options for treating deleterious antibody responses largely rely on broad immunosuppressants that can compromise overall immunity. A desirable alternative is to induce antigen-specific immune tolerance. We have shown that co-presentation of antigen and ligands of B cell Siglecs (sialic acid-binding immunoglobulin-like lectin) on a liposomal nanoparticle induces antigen-specific tolerance. Although Siglec-engaging tolerance-inducing antigenic liposomes (STALs) induce robust B cell tolerance in naïve mice, the full potential of STALs requires long-term tolerance induction and suppression of an ongoing immune response. We hypothesized that STALs encapsulated with rapamycin (RAPA), an immunomodulator, could improve the efficacy of STALs and potentially enable their use in the context of immunological memory. Here, we show that formulation of STALs with RAPA produces enhanced tolerance induction in naïve mice compared to STALs without RAPA, but has minimal impact on inducing tolerance in previously sensitized mice. These findings indicate that the addition of immunomodulator to STALs could be beneficial in tolerance induction and support future development of STALs for the treatment of allergy and autoimmune diseases.

Current treatments for unwanted antibody responses largely rely on immunosuppressive drugs compromising overall immunity. New approaches to achieve antigen-specific tolerance are desirable to avoid unwanted side effects. Several nanoparticle-based approaches that utilize different mechanisms to tolerize the B or T cell arms of the humoral immune response have shown promise for induction of antigen-specific tolerance, raising the possibility that they could work synergistically if combined. Earlier we showed that Siglec-engaging tolerance-inducing antigenic liposomes (STALs) that display both an antigen (Ag) and glycan ligands of the inhibitory co-receptor CD22 (CD22L) lead to robust antigen-specific B cell tolerance to protein antigens in naive mice. In another approach, administration of free Ag with poly­(lactic-co-glycolic acid)–rapamycin nanoparticles (PLGA-R) induced robust antigen-specific tolerance through production of regulatory T cells. Here we illustrate that coadministration of STALs together with PLGA-R to naive mice induced more robust tolerance to multiple antigen challenges than either nanoparticle alone. Moreover, in K/BxN mice that develop spontaneous autoimmune arthritis to the self-antigen glucose-6-phosphate-isomerase (GPI), co-delivery of GPI-LP-CD22L and PLGA-R delayed onset of disease and in some mice prevented the disease indefinitely. The results show synergy between B cell-tolerizing STALs and T cell-tolerizing PLGA-R and the potential to induce tolerance in early stage autoimmune disease.

AbstractObjectiveThis study aims to examine the therapeutic potential of combined treatment with B cell targeted STALs and T cell targeted PLGA-R nanoparticles in treating K/BxN mice that develop spontaneous autoimmune arthritis to the self-antigen glucose-6-phosphate-isomerase (GPI).MethodsSiglec-engaging tolerance-inducing antigenic liposomes (STALs) that display both an antigen (Ag) and glycan ligands of the inhibitory co-receptor CD22 (CD22L) were prepared by thin film hydration method. Rapamycin encapsulated PLGA nanoparticles (PLGA-R) were prepared by the oil in water single emulsion method. The K/BxN arthritis mice were treated intravenously with GPI-STALs and PLGA-R nanoparticles prophylactically and therapeutically. Disease progression was monitored by paw thickness measurements and GPI-specific IgG titers were determined by serum ELISAs. Changes in cartilage and synovium were evaluated by histological analysis.ResultsCo-administration of STALs together with PLGA-R to naïve mice induced more robust tolerance to multiple antigen challenges than either nanoparticle alone. Repeated dosing was beneficial as co-administration of 5 doses of GPI-STALs and PLGA-R prophylactically delayed disease onset until 11 weeks, and in some cases indefinitely. Therapeutic treatment of K/BxN mice with GPI-STALs and PLGA-R after disease symptoms are apparent showed prevention and, in some cases, even reversal of disease. In addition, histological examination of treated K/BxN mice showed normal cartilage and synovium and the absence of infiltrating immune cells into the joint space as compared to untreated mice.ConclusionTogether these data show synergy between B cell-tolerizing STALs and T cell-tolerizing PLGA-R and the potential to induce tolerance in early stage autoimmune disease.

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