Metabolic and immune effects of immunotherapy with proinsulin peptide in human new-onset type 1 diabetes.

Immunotherapy using short immunogenic peptides of disease-related autoantigens restores immune tolerance in preclinical disease models. We studied safety and mechanistic effects of injecting human leukocyte antigen-DR4(DRB1*0401)-restricted immunodominant proinsulin peptide intradermally every 2 or 4 weeks for 6 months in newly diagnosed type 1 diabetes patients. Treatment was well tolerated with no systemic or local hypersensitivity. Placebo subjects showed a significant decline in stimulated C-peptide (measuring insulin reserve) at 3, 6, 9, and 12 months versus baseline, whereas no significant change was seen in the 4-weekly peptide group at these time points or the 2-weekly group at 3, 6, and 9 months. The placebo group's daily insulin use increased by 50% over 12 months but remained unchanged in the intervention groups. C-peptide retention in treated subjects was associated with proinsulin-stimulated interleukin-10 production, increased FoxP3 expression by regulatory T cells, low baseline levels of activated ß cell-specific CD8 T cells, and favorable ß cell stress markers (proinsulin/C-peptide ratio). Thus, proinsulin peptide immunotherapy is safe, does not accelerate decline in ß cell function, and is associated with antigen-specific and nonspecific immune modulation.

Role of the Fc region in CD70-specific antibody effects on cardiac transplant survival.

BACKGROUND: The role of the CD70-specific antibody and the mechanisms by which it extends transplant survival are not known. METHODS: Fully major histocompatibility complex-mismatched heterotopic heart transplantation (BALB/c to C57BL/6) was performed. Treated mice received intraperitoneal injections of wild-type (WT) CD70-specific antibody (FR70) or IgG1 or IgG2a chimeric antibodies on days 0, 2, 4, and 6 posttransplantation. RESULTS: WT FR70 antibody significantly extended heart transplant survival to 19 days compared with untreated mice (median survival time [MST]=10 days). Graft survival using the nondepleting IgG1 antibody was significantly shorter (MST=14 days), whereas the survival using depleting IgG2a antibody (MST=18) was similar to that using WT FR70. The FR70 and IgG2a antibodies demonstrated a greater efficiency of fixing mouse complement over the IgG1 variant in vitro. CD4 and CD8 T-cell graft infiltration was reduced with treatment; however, this was most pronounced with WT FR70 and IgG2a antibody therapy compared with the IgG1 chimeric variant. Circulating donor-specific IgG alloantibodies were initially reduced with WT FR70 treatment (day 8 posttransplantation) but increased at days 15 and 20 posttransplantation to the level detected in untreated controls. CONCLUSION: We conclude that WT (FR70) and the IgG2a depleting variant of CD70-specific antibody reduce graft infiltrating CD4 and CD8 T cells, transiently reduce serum alloantibody levels, and extend graft survival. In contrast, the nondepleting IgG1 variant of this antibody showed lower efficacy. These data suggest that a depleting mechanism of action and not merely costimulation blockade plays a substantial role in the therapeutic effects of CD70-specific antibody.

Intermittent antibody-based combination therapy removes alloantibodies and achieves indefinite heart transplant survival in presensitized recipients.

BACKGROUND: It is well established that primed/memory T cells play a critical role in heart transplant rejection. This contributes to the challenges faced in the transplant clinic because current treatments that are efficient in controlling naïve T cell alloresponses have limited efficacy on primed T cell responders. METHODS: Fully MHC-mismatched heart transplantation was performed from BALB/c to C57BL/6 mice presensitized with BALB/c splenocytes 14 days pretransplantation. A combination therapy comprising CD70-, CD154-, and CD8-specific antibodies (Abs) was administered at day 0 and 4 posttransplantation with rapamycin on days 0 to 4. RESULTS: The Ab combination therapy extended heart transplant survival in presensitized recipients from median survival time 8 days (MST) to MST 78 days. A decrease in the number of splenic interferon-gamma-secreting cells measured by ELISpot assay was seen in the treated group compared with the untreated controls. However, graft-infiltrating CD8+ and CD4+ T cells persisted despite treatment and the number of intragraft CD4+ T cells increased at day 30 posttransplantation. When an additional "rescue therapy" comprising the same Abs was readministered at days 30, 60, and 90 posttransplantation, T cell infiltration was reduced and indefinite graft survival was observed. Furthermore, rescue therapy resulted in gradual decrease in titer and, by day 90 posttransplantation, the complete loss of the preexisting, donor-specific Abs. CONCLUSION: We conclude that our Ab combination therapy extends allograft survival in presensitized recipients. When combined with intermittent Ab-mediated rescue therapy, this results in indefinite allograft survival and a loss of the preexisting, donor-specific Abs from the circulation.