The Presence of Renal IgG Deposits in Necrotizing Crescentic Glomerulonephritis Associated with ANCA Is Not Related to Worse Renal Clinical Outcomes.

INTRODUCTION: Classical pauci-immune necrotizing crescentic glomerulonephritis (CGN) associated with antineutrophil cytoplasmic autoantibodies (ANCA) is characterized by the absence of renal immunoglobulin (Ig) deposits. However, IgG deposits can sometimes be present. We wanted to assess whether necrotizing CGN with IgG deposits is associated with a more severe presentation and outcome than necrotizing CGN without IgG deposits. METHODS: Between November 2008 and August 2013, we retrospectively identified 158 patients from four centers who had necrotizing CGN due to primary ANCA-associated systemic vasculitis. Glomerular IgG deposits were found in 18 (11%) patients (group 1). For each patient in group 1, we selected 2 patients with classical pauci-immune necrotizing CGN with the nearest date of diagnosis in the same center (group 2, n = 36). We assessed clinical, biological, and pathological characteristics in both groups. RESULTS: Baseline characteristics were similar in both groups, and most patients had ANCA-associated vasculitis with antibodies to myeloperoxidase (74%). Deposits displayed moderate to strong staining in 9 patients. As compared with group 2, group 1 exhibited a higher frequency of interstitial fibrosis/tubular atrophy lesions (p = 0.024) and lower frequency of acute tubular necrosis (p = 0.046). Nevertheless, after a mean follow-up of 30 and 26 months for group 1 and group 2, respectively, IgG deposits did not affect the renal prognosis or probability of relapse. Finally, the groups did not differ in renal or patient survival. CONCLUSIONS: IgG deposits, detected in 11% of patients with ANCA-associated necrotizing CGN, did not affect renal or patient outcomes.

Anti-CD28 Antibody and Belatacept Exert Differential Effects on Mechanisms of Renal Allograft Rejection.

Belatacept is a biologic that targets CD80/86 and prevents its interaction with CD28 and its alternative ligand, cytotoxic T lymphocyte antigen 4 (CTLA-4). Clinical experience in kidney transplantation has revealed a high incidence of rejection with belatacept, especially with intensive regimens, suggesting that blocking CTLA-4 is deleterious. We performed a head to head assessment of FR104 (n=5), a selective pegylated Fab' antibody fragment antagonist of CD28 that does not block the CTLA-4 pathway, and belatacept (n=5) in kidney allotransplantation in baboons. The biologics were supplemented with an initial 1-month treatment with low-dose tacrolimus. In cases of acute rejection, animals also received steroids. In the belatacept group, four of five recipients developed severe, steroid-resistant acute cellular rejection, whereas FR104-treated animals did not. Assessment of regulatory T cell-specific demethylated region methylation status in 1-month biopsy samples revealed a nonsignificant trend for higher regulatory T cell frequencies in FR104-treated animals. Transcriptional analysis did not reveal significant differences in Th17 cytokines but did reveal higher levels of IL-21, the main cytokine secreted by CD4 T follicular helper (Tfh) cells, in belatacept-treated animals. In vitro, FR104 controlled the proliferative response of human preexisting Tfh cells more efficiently than belatacept. In mice, selective CD28 blockade also controlled Tfh memory cell responses to KLH stimulation more efficiently than CD80/86 blockade. Our data reveal that selective CD28 blockade and belatacept exert different effects on mechanisms of renal allograft rejection, particularly at the level of Tfh cell stimulation.

Advantages of Papio anubis for preclinical testing of immunotoxicity of candidate therapeutic antagonist antibodies targeting CD28.

Antagonist anti-CD28 antibodies prevent T-cell costimulation and are functionally different from CTLA4Ig since they cannot block CTLA-4 and PDL-1 co-inhibitory signals. They demonstrated preclinical efficacy in suppressing effector T cells while enhancing immunoregulatory mechanisms. Because a severe cytokine release syndrome was observed during the Phase 1 study with the superagonist anti-CD28 TGN1412, development of other anti-CD28 antibodies requires careful preclinical evaluation to exclude any potential immunotoxicity side-effects. The failure to identify immunological toxicity of TGN1412 using macaques led us to investigate more relevant preclinical models. We report here that contrary to macaques, and like in man, all baboon CD4-positive T lymphocytes express CD28 in their effector memory cells compartment, a lymphocyte subtype that is the most prone to releasing cytokines after reactivation. Baboon lymphocytes are able to release pro-inflammatory cytokines in vitro in response to agonist or superagonist anti-CD28 antibodies. Furthermore, we compared the reactivity of human and baboon lymphocytes after transfer into non obese diabetic/severe combined immunodeficiency (NOD/SCID) interleukin-2rγ knockout mice and confirmed that both cell types could release inflammatory cytokines in situ after injection of agonistic anti-CD28 antibodies. In contrast, FR104, a monovalent antagonistic anti-CD28 antibody, did not elicit T cell activation in these assays, even in the presence of anti-drug antibodies. Infusion to baboons also resulted in an absence of cytokine release. In conclusion, the baboon represents a suitable species for preclinical immunotoxicity evaluation of anti-CD28 antibodies because their effector memory T cells do express CD28 and because cytokine release can be assessed in vitro and trans vivo.