FR104, an Antagonist Anti-CD28 Monovalent Fab’ Antibody, Prevents Alloimmunization and Allows Calcineurin Inhibitor Minimization in Nonhuman Primate Renal Allograft

Abstract

These authors contributed equally to the senior authorship of this study.Selective targeting of CD28 might represent an effective immunomodulation strategy by preventing T cell costimulation, while favoring coinhibition since inhibitory signals transmitted through CTLA-4; PD-L1 and B7 would not be affected. We previously showed in vitro and in vivo that anti-CD28 antagonists suppress effector T cells while enhancing regulatory T cell (Treg) suppression and immune tolerance. Here, we evaluate FR104, a novel antagonist pegylated anti-CD28 Fab' antibody fragment, in nonhuman primate renal allotransplantation. FR104, in association with low doses of tacrolimus or with rapamycin in a steroid-free therapy, prevents acute rejection and alloantibody development and prolongs allograft survival. However, when FR104 was associated with mycophenolate mofetil and steroids, half of the recipients rejected their grafts prematurely. Finally, we observed an accumulation of Helios-negative Tregs in the blood and within the graft after FR104 therapy, confirmed by Tregspecific demethylated region DNA analysis. In conclusion, FR104 reinforces immunosuppression in calcineurin inhibitor (CNI)-low or CNI-free protocols, without the need of steroids. Accumulation of intragraft Tregs suggested the promotion of immunoregulatory mechanisms. Selective CD28 antagonists might become an alternative CNI-sparing strategy to B7 antagonists for kidney transplant recipients.

Selective CD28 Antagonist Blunts Memory Immune Responses and Promotes Long-Term Control of Skin Inflammation in Nonhuman Primates

“…response to tuberculin; 3) peripheral regulatory T cell induction or accumulation was excluded in blood because we did not observe significant modulation of regulatory T cell numbers or frequencies, and elimination of these cells did not modify the ex vivo IFN-g response to tuberculin after treatment with FR104 as compared with control; and 4) we and others have previously reported that selective CD28 blockade induced regulatory T cell infiltrates at the site of inflammation (15,17,18,23). In this study, we did not observe important T cell infiltrates in skin biopsies after selective CD28 blockade, suggesting that if regulatory T cells directly control effector T cell activation, they would preferably be located in draining lymph nodes.…”

“…We assessed the efficiency of selective CD28 blockade in a nonhuman primate skin inflammatory model on the control of cellular and humoral memory responses and the effect on latent viral infections. It had been shown previously that CD28 blockade induces immune regulation and prevents allograft rejection or autoimmune attacks in rodents (14) and nonhuman primate (15,23,24) models. However, in these models, animals were immunologically naive toward immunizing Ags.…”

“…FR104 staining was performed with a polyethylene glycol rabbit mAb (Epitomics) followed by fluorescent goat anti-rabbit IgG (Invitrogen, Grand Island, NY). CD28 receptor occupancy by FR104 on T lymphocytes was determined by performing the ratio of mean fluorescence intensity of FR104 staining between an unmodified blood sample and a blood sample incubated for 30 min at room temperature with a saturating concentration of FR104 (5 mg/ml) as previously described (23). This represents the percentage of maximal binding.…”

“…We have recently reported that selective blockade of CD28 with FR104 is effective in naive nonhuman primates to prevent allograft rejection (23) and protects from acute fatal experimental autoimmune encephalomyelitis (24), the elected experimental model of multiple sclerosis. To evaluate the role of CD28 on memory T lymphocyte reactivation, we purified naive (CD45RA + CCR7 + ) and memory (CD45RA + CCR7 + -depleted cells) human T lymphocytes from healthy volunteers and stimulated these cells with either irradiated allogeneic PBMC or autologous T cell-depleted PBMC pulsed with pools of 32 HLA class I-restricted peptides and 23 HLA class II-restricted peptides from CMV, EBV, influenza virus, and tetanus toxin.…”

Selective CD28 blockade attenuates CTLA-4–dependent CD8+ memory T cell effector function and prolongs graft survival

“…Previous studies have examined the impact of selective CD28 blockers in both mouse and NHP models of transplantation and autoimmunity (32)(33)(34)(35)(36)(37). For example, FR104, an antagonist anti-CD28 monovalent Fab' antibody, has been shown to prevent alloimmunization and prolong graft survival (38,39). These effects were CTLA-4 dependent and involved the promotion of Foxp3 + regulatory T cell responses following transplantation (36,40).…”