Cross-Reactivity of Herpesvirus-Specific CD8 T Cell Lines Toward Allogeneic Class I MHC Molecules

Although association between persistent viral infection and allograft rejection is well characterized, few examples of T-cell cross-reactivity between self-MHC/viral and allogeneic HLA molecules have been documented so far. We appraised in this study the alloreactivity of CD8 T cell lines specific for immunodominant epitopes from human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV). CD8 T cell lines were generated after sorting with immunomagnetic beads coated with either pp65495–503/A*0201, BMLF1259–267/A*0201, or BZLF154–64/B*3501 multimeric complexes. Alloreactivity of the CD8 T cell lines against allogeneic class I MHC alleles was assessed by screening of (i) TNF-α production against COS-7 cells transfected with as many as 39 individual HLA class I-encoding cDNA, and (ii) cytotoxicity activity toward a large panel of HLA-typed EBV-transformed B lymphoblastoid cell lines. We identified several cross-reactive pp65/A*0201-specific T cell lines toward allogeneic HLA-A*3001, A*3101, or A*3201. Moreover, we described here cross-recognition of HLA-Cw*0602 by BZLF1/B*3501-specific T cells. It is noteworthy that these alloreactive CD8 T cell lines showed efficient recognition of endothelial cells expressing the relevant HLA class I allele, with high level TNF-α production and cytotoxicity activity. Taken together, our data support the notion that herpes virus-specific T cells recognizing allo-HLA alleles may promote solid organ rejection

Recombinant human C1-inhibitor prevents acute antibody-mediated rejection in alloimmunized baboons

Acute antibody-mediated rejection is an unsolved issue in transplantation, especially in the context of pretransplant immunization. The deleterious effect of preformed cytotoxic anti-HLA antibodies through complement activation is well proven, but very little is known concerning complement blockade to prevent/cure this rejection. Here, we used a baboon model of preimmunization to explore the prevention of acute antibody-mediated rejection by an early inhibition of the classical complement pathway using human recombinant C1-inhibitor. Baboons were immunized against peripheral blood mononuclear cells from allogeneic donors and, once a specific and stable immunization had been established, they received a kidney from the same donor. Rejection occurred at day 2 posttransplant in untreated presensitized recipients, with characteristic histological lesions and complement deposition. As recombinant human C1-inhibitor blocks in vitro cytotoxicity induced by donor-specific antibodies, other alloimmunized baboons received the drug thrice daily intravenously during the first 5 days after transplant. Rejection was prevented during this treatment but occurred after discontinuation of treatment. We show here that early blockade of complement activation by recombinant human C1-inhibitor can prevent acute antibody-mediated rejection in presensitized recipients. This treatment could also be useful in other forms of acute antibody-mediated rejection caused by induced antibodies

Corneal Xenotransplantation: Anterior Lamellar Keratoplasty

International audienceCorneal transplantation for the treatment of corneal blindness is challenging in many countries due to the shortage of graft procurement. Xenocorneal transplantation is an interesting alternative to explore despite immunologic rejection, which mainly involves endothelial cells. As anterior lamellar keratoplasty, when indicated, shows less immunologic reaction, we developed and describe below a pig-to-non-human-primate model of anterior lamellar corneal xenograft. This model can be used to assess the efficacy of corneas from genetically modified pigs

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

International audienceSelective targeting of CD28 might represent an effective immunomodulation strategy by preventing T cell costimulation, while favoring coinhibition since inhib-itory 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 allo-transplantation. 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 Treg-specific demethylated region DNA analysis. In conclusion , FR104 reinforces immunosuppression in calci-neurin inhibitor (CNI)-low or CNI-free protocols, without the need of steroids. Accumulation of intra-graft Tregs suggested the promotion of immunoregu-latory mechanisms. Selective CD28 antagonists might become an alternative CNI-sparing strategy to B7 antagonists for kidney transplant recipients

hCTLA4-Ig transgene expression in keratocytes modulates rejection of corneal xenografts in a pig to non-human primate anterior lamellar keratoplasty model

Version of Record online: 7 JUL 2014Background: Human corneal allografting is an established procedure to cure corneal blindness. However, a shortage of human donor corneas as well as compounding economic, cultural, and organizational reasons in many countries limit its widespread use. Artificial corneas as well as porcine corneal xenografts have been considered as possible alternatives. To date, all preclinical studies using de-cellularized pig corneas have shown encouraging graft survival results; however, relatively few studies have been conducted in pig to non-human primate (NHP) models, and particularly using genetically engineered donors. Methods: In this study, we assessed the potential benefit of using either hCTLA4-Ig transgenic or α1,3-Galactosyl Transferase (GT) Knock-Out (KO) plus transgenic hCD39/hCD55/hCD59/fucosyl-transferase pig lines in an anterior lamellar keratoplasty pig to NHP model. Results: Corneas from transgenic animals expressing hCTLA4-Ig under the transcriptional control of a neuron-specific enolase promoter showed transgene expression in corneal keratocytes of the stroma and expression was maintained after transplantation. Although a first acute rejection episode occurred in all animals during the second week post-keratoplasty, the median final rejection time was 70 days in the hCTLA4-Ig group vs. 21 days in the wild-type (WT) control group. In contrast, no benefit for corneal xenograft survival from the GTKO/transgenic pig line was found. At rejection, cell infiltration in hCTLA4Ig transgenic grafts was mainly composed of macrophages with fewer CD3+ CD4+ and CD79+ cells than in other types of grafts. Anti-donor xenoantibodies increased dramatically between days 9 and 14 post-surgery in all animals. Conclusions: Local expression of the hCTLA4-Ig transgene dampens rejection of xenogeneic corneal grafts in this pig-to-NHP lamellar keratoplasty model. The hCTLA4-Ig transgene seems to target T-cell responses without impacting humoral responses, the control of which would presumably require additional peripheral immunosuppression.Bertrand Vabres, Stéphanie Le Bas-Bernardet, David Riochet, Yan Chérel, David Minault, Jérémy Hervouet, Yvette Ducournau, Anne Moreau, Véronique Daguin, Flora Coulon, Annaïck Pallier, Sophie Brouard, Simon C. Robson, Mark B. Nottle, Peter J. Cowan, Eric Venturi, Pascal Mermillod, Philippe Brachet, Cesare Galli, Irina Lagutina, Roberto Duchi, Jean-Marie Bach, Gilles Blancho, Jean-Paul Soulillou and Bernard Vanhov