Robert L. Kampen

results From A Human Renal Allograft Tolerance Trial Evaluating The Humanized Cd52-specific Monoclonal Antibody Alemtuzumab (campath-1h)

Background. Profound T‐cell depletion before allotransplantation with gradual posttransplant T‐cell repopulation induces a state of donor‐specific immune hyporesponsiveness or tolerance in some animal models. Alemtuzumab (Campath‐1H, Millennium Pharmaceuticals, Cambridge, MA) is a humanized CD52‐specific monoclonal antibody that produces profound T‐cell depletion in humans and reduces the need for maintenance immunosuppression after renal transplantation. We therefore performed a study to determine if pretransplant T‐cell depletion with alemtuzumab would induce tolerance in human renal allografts and to evaluate the nature of the alloimmune response in the setting of T‐cell depletion. Methods. Seven nonsensitized recipients of livingdonor kidneys were treated perioperatively with alemtuzumab and followed postoperatively without maintenance immunosuppression. Patients were evaluated clinically by peripheral flow cytometry, protocol biopsies evaluated immunohistochemically, and real‐time polymerase chain reaction‐based transcriptional analysis. Results. Lymphocyte depletion was profound in the periphery and secondary lymphoid tissues. All patients developed reversible rejection episodes within the first month that were characterized by predominantly monocytic (not lymphocytic) infiltrates with only rare T cells in the peripheral blood or allograft. These episodes were responsive to treatment with steroids or sirolimus or both. After therapy, patients remained rejection‐free on reduced immunosuppression, generally monotherapy sirolimus, despite the recovery of lymphocytes to normal levels. Conclusions. T‐cell depletion alone does not induce tolerance in humans. These data underscore a prominent role for early responding monocytes in human allograft rejection.

Alefacept promotes co-stimulation blockade based allograft survival in nonhuman primates

Memory T cells promote allograft rejection particularly in co-stimulation blockade–based immunosuppressive regimens. Here we show that the CD2-specific fusion protein alefacept (lymphocyte function–associated antigen-3–Ig; LFA -3–Ig) selectively eliminates memory T cells and, when combined with a co-stimulation blockade–based regimen using cytotoxic T lymphocyte antigen-4 (CTLA-4)-Ig, a CD80- and CD86-specific fusion protein, prevents renal allograft rejection and alloantibody formation in nonhuman primates. These results support the immediate translation of a regimen for the prevention of allograft rejection without the use of calcineurin inhibitors, steroids or pan–T cell depletion.

Effect of Alemtuzumab (CAMPATH 1-H) in patients with inclusion-body myositis

Sporadic inclusion-body myositis (sIBM) is the most common disabling, adult-onset, inflammatory myopathy histologically characterized by intense inflammation and vacuolar degeneration. In spite of T cell-mediated cytotoxicity and persistent, clonally expanded and antigen-driven endomysial T cells, the disease is resistant to immunotherapies. Alemtuzumab is a humanized monoclonal antibody that causes an immediate depletion or severe reduction of peripheral blood lymphocytes, lasting at least 6 months. We designed a proof-of-principle study to examine if one series of Alemtuzumab infusions in sIBM patients depletes not only peripheral blood lymphocytes but also endomysial T cells and alters the natural course of the disease. Thirteen sIBM patients with established 12-month natural history data received 0.3 mg/kg/day Alemtuzumab for 4 days. The study was powered to capture ≥10% increase strength 6 months after treatment. The primary end-point was disease stabilization compared to natural history, assessed by bi-monthly Quantitative Muscle Strength Testing and Medical Research Council strength measurements. Lymphocytes and T cell subsets were monitored concurrently in the blood and the repeated muscle biopsies. Alterations in the mRNA expression of inflammatory, stressor and degeneration-associated molecules were examined in the repeated biopsies. During a 12-month observation period, the patients’ total strength had declined by a mean of 14.9% based on Quantitative Muscle Strength Testing. Six months after therapy, the overall decline was only 1.9% (P < 0.002), corresponding to a 13% differential gain. Among those patients, four improved by a mean of 10% and six reported improved performance of daily activities. The benefit was more evident by the Medical Research Council scales, which demonstrated a decline in the total scores by 13.8% during the observation period but an improvement by 11.4% (P < 0.001) after 6 months, reaching the level of strength recorded 12 months earlier. Depletion of peripheral blood lymphocytes, including the naive and memory CD8+ cells, was noted 2 weeks after treatment and persisted up to 6 months. The effector CD45RA+CD62L cells, however, started to increase 2 months after therapy and peaked by the 4th month. Repeated muscle biopsies showed reduction of CD3 lymphocytes by a mean of 50% (P < 0.008), most prominent in the improved patients, and reduced mRNA expression of stressor molecules Fas, Mip-1a and αB-crystallin; the mRNA of desmin, a regeneration-associated molecule, increased. This proof-of-principle study provides insights into the pathogenesis of inclusion-body myositis and concludes that in sIBM one series of Alemtuzumab infusions can slow down disease progression up to 6 months, improve the strength of some patients, and reduce endomysial inflammation and stressor molecules. These encouraging results, the first in sIBM, warrant a future study with repeated infusions (Clinical Trials. Gov NCT00079768).

Induction Therapy With Monoclonal Antibodies Specific For Cd80 And Cd86 Delays The Onset Of Acute Renal Allograft Rejection In Non-human Primates1

CD80 and CD86 (also known as B7–1 and B7–2, respectively) are both ligands for the T cell costimulatory receptors CD28 and CD152. Both CD80 and CD86 mediate T cell costimulation, and as such, have been studied for their role in promoting allograft rejection. In this study we demonstrate that administering monoclonal antibodies specific for these B7 ligands can delay the onset of acute renal allograft rejection in rhesus monkeys. The most durable effect results from simultaneous administration of both anti-B7 antibodies. The mechanism of action does not involve global depletion of T or B cells. Despite in vitro and in vivo evidence demonstrating the effectiveness of the anti-B7 antibodies in suppressing T cell responsiveness to alloantigen, their use does not result in durable tolerance. Prolonged therapy with murine anti-B7 antibodies is limited by the development of neutralizing antibodies, but that problem was avoided when humanized anti-B7 reagents are used. Most animals develop rejection and an alloantibody response although still on antibody therapy and before the development of a neutralizing antibody response. Anti-B7 antibody therapy may have use as an adjunctive agent for clinical allotransplantation, but using the dosing regimens we used, is not a tolerizing therapy in this non-human primate model.

Functionally significant renal allograft rejection is defined by transcriptional criteria

Renal allograft acute cellular rejection (ACR) is a T‐cell mediated disease that is diagnosed histologically. However, many normally functioning allografts have T‐cell infiltrates and histological ACR, and many nonimmune processes cause allograft dysfunction. Thus, neither histological nor functional criteria are sufficient to establish a significant rejection, and the fundamental features of clinical rejection remain undefined. To differentiate allograft lymphocyte infiltration from clinically significant ACR, we compared renal biopsies from patients with ACR to patients with: sub‐clinical rejection (SCR, stable function with histological rejection); no rejection; and nontransplanted kidneys. Biopsies were compared histologically and transcriptionally by RT‐PCR for 72 relevant immune function genes. Neither the degree nor the composition of the infiltrate defined ACR. However, transcripts up‐regulated during effector TH1 T‐cell activation, most significantly the transcription factor T‐bet, the effector receptor Fas ligand and the costimulation molecule CD152 clearly (p = 0.001) distinguished the patient categories. Transcripts from other genes were equivalently elevated in SCR and ACR, indicating their association with infiltration, not dysfunction. Clinically significant ACR is not defined solely by the magnitude nor composition of the infiltrate, but rather by the transcriptional activity of the infiltrating cells. Quantitative analysis of selected gene transcripts may enhance the clinical assessment of allografts.

Results from a human renal allograft tolerance trial evaluating T-cell depletion with alemtuzumab combined with deoxyspergualin.

Background. Perioperative lymphocyte depletion induces allograft tolerance in some animal models, but in humans has only been shown to reduce immunosuppressive requirements. Without maintenance immunosuppression, depleted human renal allograft recipients experience rejection characterized by infiltration of the allograft with monocytes and macrophages. T-cell depletion combined with a brief course of deoxyspergualin (DSG), a drug with inhibitory effects on monocytes and macrophages, induces tolerance in nonhuman primates. We therefore performed a trial to determine if lymphocyte depletion with alemtuzumab combined with DSG would induce tolerance in humans. Methods. Five recipients of live donor kidneys were treated perioperatively with alemtuzumab and DSG and followed postoperatively without maintenance immunosuppression. Patients were evaluated clinically, by flow cytometry, and by protocol biopsies analyzed immunohistochemically and with real-time polymerase chain reaction. Results were compared to previously studied patients receiving alemtuzumab alone or standard immunosuppression. Results. Despite profound T-cell depletion and therapeutic DSG dosing, all alemtuzumab/DSG patients developed reversible rejection that was similar in timing, histology, and transcriptional profile to that seen in patients treated with alemtuzumab alone. Chemokine expression was marked prior to and during rejections. Conclusions. We conclude that treatment with alemtuzumab and DSG does not induce tolerance in humans. Chemokine production may not be adequately suppressed using this approach.

Molecular evaluation of BK polyomavirus nephropathy.

Understanding at a molecular level, the immunologic response of polyomavirus nephropathy (PVN), a critical cause of kidney graft loss, could lead to new targets for treatment and diagnosis. We undertook a transcriptional evaluation of kidney allograft biopsies from recipients with PVN or acute rejection (AR), as well as from recipients with stable allograft function (SF). In both the PVN and AR groups, Banff histologic scores and immunohistochemical analysis of inflammatory infiltrates were similar. Despite their different etiologies, the transcriptional profiles of PVN and AR were remarkably similar. However, transcription of genes previously linked to AR including CD8 (65.9 ± 18.8) and related molecules IFN‐γ(55.1 ± 17.0), CXCR3 (49.9 ± 12.8) and perforin (153.8 ± 50.4) were significantly higher in PVN compared to AR (30.9 ± 2.0, 14.0 ± 7.3, 12.1 ± 7.3 and 15.6 ± 3.8‐fold, respectively; p < 0.01). Importantly, transcription of molecules associated with graft fibrosis including matrix collagens, TGFβ, MMP2 and 9, as well as markers of epithelial‐mesenchymal transformation (EMT) were significantly higher in PVN than AR. Thus, renal allografts with PVN transcribe proinflammatory genes equal in character and larger in magnitude to that seen during acute cellular rejection. BK infection creates a transcriptional microenvironment that promotes graft fibrosis. These findings provide new insights into the intrarenal inflammation of BK infection that promotes graft loss.

Combination induction therapy with monoclonal antibodies specific for CD80, CD86, and CD154 in nonhuman primate renal transplantation.

Background. Antibodies and fusion proteins specific for CD80, CD86, and CD154 have shown promise as agents capable of inducing donor-specific tolerance in rodents. These agents have also been shown to be synergistic with one another in many settings of counter-adaptive immunity. In the nonhuman primate, monoclonal antibodies specific for CD80 and CD86 have prolonged the time to rejection of renal allografts but have not resulted in tolerance. A monoclonal antibody specific for CD154 has resulted in markedly prolonged survival of kidney, islet, cardiac, and skin allografts, but again most animals have eventually developed rejection after prolonged periods of rejection-free survival off therapy. Methods. A combination of monoclonal antibodies specific for CD80, CD86, and CD154 were used in a mismatched nonhuman primate renal-allograft model. Doses used were based on optimized treatment protocols for each agent individually. Results. Treatment of four rhesus macaques with this combination yielded a mean rejection-free survival of 565 days (311–911 days), significantly greater than untreated controls (mean survival=7.0 days, P =0.001) and animals treated with only a combination of anti-CD80 and CD86 (mean survival=191 days, P =0.01). The survival of animals treated with this combination of monoclonal antibodies was not significantly greater than those treated with anti-CD154 alone, but the production of alloantibody was delayed compared with monotherapy anti-CD154. Conclusion. These data suggest that a synergy exists between these agents, particularly with regard to T-dependent B-cell responses, but that they fail to induce durable tolerance in nonhuman primates.

Humanized anti-CD154 antibody therapy for the treatment of allograft rejection in nonhuman primates.

The anti-CD154 antibody hu5C8 prevents acute allograft rejection and prolongs allograft survival after withdrawal of therapy in nonhuman primates. This study describes the use of hu5C8 as a rescue agent for rejection developing after the withdrawal of hu5C8. Twelve rhesus monkeys that had received renal allografts under hu5C8 induction and subsequently rejected were studied. Rescue with hu5C8 was analyzed based on the histological character of the rejection (acute versus chronic) and whether conventional therapy was received at the time of rescue or induction. The diagnosis of rejection and response to therapy was based on allograft function and histology. Four monkeys that had acute rejection associated with conventional immunosuppression and hu5C8 were not reversed by hu5C8 rescue. Four animals with isolated chronic rejection following prolonged rejection-free survival after the withdrawal of hu5C8 did not respond to hu5C8 rescue therapy. Hu5C8 rescue therapy effectively reversed acute rejection occurring in two monkeys after hu5C8 withdrawal. One of two animals with combined acute on chronic rejection responded to hu5C8 rescue therapy. Hu5C8 effectively reverses acute but not chronic allograft rejection and appears to have no synergistic effect with conventional rescue agents.

Disruption of CD40/CD40-Ligand Interactions in a Retinal Autoimmunity Model Results in Protection without Tolerance

We examined the role of CD40/CD40L interactions on the development of experimental autoimmune uveoretinitis (EAU), a cell-mediated, Th1-driven autoimmune disease that serves as a model for autoimmune uveitis in humans. EAU-susceptible B10.RIII mice immunized with the retinal autoantigen interphotoreceptor retinoid binding protein in CFA and treated with anti-CD40L Ab (MR1) had reduced incidence and severity of disease. Real-time PCR analysis revealed that the innate and adaptive responses of protected mice were reduced, without an obvious shift toward a Th2 cytokine profile. In contrast to some other reports, no evidence was found for regulatory cells in adoptive transfer experiments. To determine whether CD40L blockade resulted in long-term tolerance, mice protected by treatment with MR1 Ab were rechallenged for uveitis after circulating MR1 Ab levels dropped below the detection limit of ELISA. MR1-treated mice developed severe EAU and strong cellular responses to interphotoreceptor retinoid binding protein, comparable to those of control mice. These responses were higher than in mice that had not received the primary immunization concurrently with anti-CD40L treatment. We conclude that 1) CD40/CD40L interaction is required for EAU and its disruption prevents disease development; 2) CD40L blockade inhibits the innate response to immunization and reduces priming, but does not result in immune deviation; and 3) protection is dependent on persistence of anti-CD40L Abs, and long-term tolerance is not induced. Furthermore, immunological memory develops under cover of CD40L blockade causing enhanced responses upon rechallenge. Taken together, our data suggest that ongoing CD40/CD40L blockade might be required to maintain a therapeutic effect against uveitis.