Phase I trial of a humanized, Fc receptor nonbinding OKT3 antibody, huOKT3gamma1(Ala-Ala) in the treatment of acute renal allograft rejection

BACKGROUND

HuOKT3gamma1(Ala-Ala) is a genetically-engineered derivative of the parental murine OKT3 monoclonal antibody, in which the six complementarity-determining regions have been grafted within a human IgG1 mAb, and whose C(H)2 region has been altered by site-directed mutagenesis to alter FcR-binding activity, thereby eliminating T cell activation properties. This report describes the results of a phase I trial of huOKT3gamma1(Ala-Ala) treatment of acute renal allograft rejection.

METHODS

Acute renal allograft rejection in kidney and kidney-pancreas transplant recipients was treated with huOKT3gamma1(Ala-Ala). huOKT3gamma1(Ala-Ala) dosing consisted of daily 5- or 10-mg doses adjusted initially to achieve target levels of 1000 ng/ml.

RESULTS

A total of seven patients, five kidney transplant and two kidney-pancreas transplant recipients, were treated with the monoclonal antibody for first rejection episodes. Corticosteroids (500 mg i.v. Solumedrol) were given 2 hr before the first huOKT3gamma1(Ala-Ala) dose only. Banff classification of treated rejections were the following: grade I, 1 patient, grade IIA, 1 patient, grade IIB, 4 patients, and grade III, 1 patient. Median time from transplant to rejection was 15 days, and median follow up 12 months (range 10-17 months). HuOKT3gamma1(Ala-Ala) therapy was given for 10.1+/-2.5 days, and mean total dose was 76+/-27 mg. Rejection was reversed in five of seven patients, and recurrent rejection was observed in one patient. Serum creatinine values peaked on day 1 of huOKT3gamma1(Ala-Ala) therapy, and thereafter demonstrated a progressive decline. Rejection reversal (return of creatinine to baseline) occurred at a median of 4 days and a mean of 4.1+/-2 days. Renal allograft biopsies obtained during huOKT3gamma1(Ala-Ala) therapy provided evidence of rapid rejection reversal. Patient and graft survival were both 100%. First dose reactions were minimal, and anti-OKT3 antibodies were not detected. Elevations in serum IL-10, but not IL-2 levels were observed after the first huOKT3gamma1(Ala-Ala) dose. Marked reductions in circulating CD2+, CD4+, and CD8+ T cells were observed after the first huOKT3gamma1(Ala-Ala) dose, followed by a slow progressive return of cell counts toward pretreatment values. Pharmacokinetic analysis revealed a half-life of 142+/-32 hr.

CONCLUSIONS

HuOKT3gamma1(Ala-Ala) possesses the ability to reverse vigorous rejection episodes in kidney and kidney-pancreas transplant recipients, and in comparison to murine OKT3, possesses minimal first dose reactions and does not seem to induce antibodies that bind the OKT3 idiotype. These results support the conduct of additional clinical trials with the huOKT3gamma1(Ala-Ala) antibody.

Phase I evaluation of humanized OKT3: toxicity and immunomodulatory effects of hOKT3gamma4

Murine anti-CD3 (OKT3, Muromonab-CD3) is a potent human T-lymphocyte mitogen. A previous clinical Phase I trial examined OKT3 as an immunomodulator for the treatment of cancer. However, the murine monoclonal antibody triggered a potent humoral response that neutralized the antibody activity during subsequent administration. Thus, a "humanized" form of OKT3 (hOKT3gamma4) was developed to minimize immunogenicity. The genetically engineered human anti-CD3 retained its binding activity and effectively activated T cells in vitro. Therefore, we evaluated the safety and activity of hOKT3gamma4 in a Phase I clinical trial. hOKT3gamma4 was administered as a 10-min i.v. infusion every 2 weeks for three injections (one course of therapy). Six dose levels ranging from 50 to 1600 microg/injection were evaluated. Headache and fever were common, transient toxicities but were not dose limiting. The dose-limiting toxicities were rigors and dyspnea at the 1600-microg dose level, which defined 800 microg as the maximally tolerated dose in this trial. A dose-dependent in vivo T-lymphocyte activation was produced by this treatment, and the most significant T-lymphocyte activation occurred in patients treated at the two highest dose levels (800 and 1600 microg). Persistent CD3 modulation occurred after administration of 1600 microg of hOKT3gamma4. Anti-idiotypic antibodies were detected in only 6 of 24 patients after multiple injections and were not associated with attenuation of T-lymphocyte activation. Malignant ascites resolved in three patients, one each with peritoneal mesothelioma, pancreatic adenocarcinoma, and ovarian adenocarcinoma. hOKT3gamma4 can induce T-lymphocyte activation in patients with cancer, and the immunogenicity of the "humanized" antibody is sufficiently reduced relative to its murine "parent" to permit immunostimulation by repetitive i.v. administration. The therapeutic potential of biweekly i.v. hOKT3gamma4 at a dose of 800 microg should be further evaluated.

Characterization of a cis-acting regulatory element which silences expression of the class II-A beta gene in epithelium

Class II major histocompatibility complex (MHC) genes encode for alpha/beta chain pairs that are constitutively expressed principally on mature B cells and dendritic cells in mice. These gene products are easily induced on macrophages with cytokines, and may also aberrantly appear on the surface of epithelium during immune injury. The appearance of class II determinants in parenchymal tissue potentially renders these somatic cells capable of antigen presentation to circulating CD4+ T lymphocytes, and their absence may be protective for normal tissues expressing self-antigens. The low surface class II expression observed on parenchymal cells generally correlates with low levels of mRNA, suggesting that transcription rate is a major element in class II regulation. To understand the transcriptional mechanism maintaining low basal surface expression of class II in somatic cells, we transiently transfected mini-gene reporter constructs to study the regulation of the murine A beta promoter in a cultured renal epithelial cell line. We describe here a negative cis-acting regulatory region located between -552 and -489 bp upstream of the A beta cap site that silences the transcriptional activity of the A beta promoter in epithelial cells in an orientation-dependent manner, and is also able to silence a heterologous promoter. This region is not active in class II-expressing B cells (BAL-17) in culture, but is functional in two other murine class II-negative cell lines, fibroblasts and thymoma T cells. Using competition electrophoretic mobility shift assays, we have localized the core protein binding site within this region to an 8-10-bp response element, designated A beta NRE, at -543 to -534 bp. A nuclear extract from BAL-17 cells does not bind to this element. Mutation of this site abrogates the transcriptional silencing activity of the region. We conclude that the transcription of class II-A beta in parenchymal cells, and some lymphocytes, can be actively repressed by an upstream silencing element.

Mechanisms of tubulointerstitial fibrosis

With regard to tubulointerstitial fibrogenesis we are left with a variety informational gaps regarding nearly all aspects of this clinically important process. Table 2 summarizes a generalized version of fibrogenesis based primarily on investigations in other organs. Extrapolation of data obtained with other fibrogenic systems is useful, but only in so far as it motivates us to adapt and test many of the experimental principles within in the context of the kidney. This begins with a comprehensive examination of the in vivo state, the establishment of adequate animal models, and the dissections of the process in vitro. Key areas for the future are the characterization of the signals involved, the cellular responses to these signals, and the variations in interactions produced by differing inciting fibrogenic conditions.

Murine interstitial nephritis. VII. Suppression of renal injury after treatment with soluble suppressor factor TsF1

We prepared soluble suppressor T cell factor (TsF1) from donor spleens harvested from mice primed with tubular antigen-derivatized lymphocytes to analyze both its functional interactions with a larger suppressor T cell network and its influence on the nephritogenic effector T cell response producing interstitial nephritis to a parenchymal antigen. Our findings indicate that TsF1 is antigen-specific, genetically restricted by I-J in its direct mediation of suppression, and capable of inhibiting the development of interstitial lesions. TsF1 also provides an inducing signal for the activation of effector Ts-2 suppressors following presentation by accessory cells. The induction of a Ts-2 effect, however, requires that the factor-presenting cell and the recipient of such cells share homology at I-J, and that the TsF1, the precursor Ts-2 cells, and the recipient of the Ts-2 effect share the same Igh-V allotype. Finally, the results of this current report clearly demonstrate a possible therapeutic role for soluble suppressor factors in the management of interstitial renal disease.

Murine interstitial nephritis. VII. Suppression of renal injury after treatment with soluble suppressor factor TsF1

We prepared soluble suppressor T cell factor (TsF1) from donor spleens harvested from mice primed with tubular antigen-derivatized lymphocytes to analyze both its functional interactions with a larger suppressor T cell network and its influence on the nephritogenic effector T cell response producing interstitial nephritis to a parenchymal antigen. Our findings indicate that TsF1 is antigen-specific, genetically restricted by I-J in its direct mediation of suppression, and capable of inhibiting the development of interstitial lesions. TsF1 also provides an inducing signal for the activation of effector Ts-2 suppressors following presentation by accessory cells. The induction of a Ts-2 effect, however, requires that the factor-presenting cell and the recipient of such cells share homology at I-J, and that the TsF1, the precursor Ts-2 cells, and the recipient of the Ts-2 effect share the same Igh-V allotype. Finally, the results of this current report clearly demonstrate a possible therapeutic role for soluble suppressor factors in the management of interstitial renal disease.

1,25-dihydroxyvitamin D3 stimulates interleukin-2 production by a T cell lymphoma line (MLA-144) cultured in vitamin D-deficient rat serum

A lymphocyte T cell line (MLA-144), which constitutively secretes interleukin-2 (IL-2), was shown to express receptors for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). The proliferation of an IL-2-dependent cell line (HT-2) in response to supernatants from MLA-144 cells was employed as an index of IL-2 production by MLA-144 cells. IL-2 production was two fold higher from MLA-144 cells cultured in 2% vitamin D-deficient rat serum compared to 10% fetal calf serum (FCS). The addition of 1,25(OH)2D3 at 10(-15) M or 10(-11) M augmented IL-2 production by MLA-144 cells in vitamin D-deficient rat serum, but not in fetal calf serum. At 10(-7) M 1,25(OH)2D3 there was inhibition of IL-2 production by MLA-144 cells in either vitamin D-deficient serum or FCS. There was no effect of 1,25(OH)2D3 added directly to HT-2 cells. Monoclonal antibody to the IL-2 receptor competitively inhibited the proliferation of HT-2 cells in response to MLA-144 supernatants, suggesting that it was IL-2 from the MLA-144 supernatants which influenced HT-2 proliferation. Our findings demonstrate biphasic dose effects of 1,25(OH)2D3 on lymphokine secretion. The use of vitamin D-deficient rat serum allowed us to demonstrate the effects of 1,25(OH)2D3 in the physiologic and subphysiologic range.

Experimental strategies for the study of cellular immunity in renal disease

This overview has examined some of the current experimental options available for the study of cellular immunity in the immunopathogenesis of renal disease. T cell immunity, where it has been examined, seems to have a particularly pivotal role in orchestrating and regulating functional patterns of renal injury. The use of the research methods presented here for the study of cell-mediated interactional events in kidney disease, however, has lagged behind similar efforts in other organ systems. We hope, therefore, this report will serve to stimulate and strengthen further interest in the cell biology of the nephritogenic immune response.

Spontaneous interstitial nephritis in kdkd mice. II. Characterization of a tubular antigen-specific, H-2K-restricted Lyt-2+ effector T cell that mediates destructive tubulointerstitial injury

In this report, we have examined the effector T cell repertoire in the spontaneous interstitial nephritis of kdkd mice. Lymph node cells from nephritic kdkd mice are capable of transferring this disease into thymectomized, irradiated, and bone marrow-reconstituted CBA/Ca recipients. CBA/Ca mice do not spontaneously develop interstitial nephritis and are normally resistant to the adoptive transfer of nephritic cells, a resistance that in the short term can be attenuated with low-dose cyclophosphamide. We therefore used delayed-type hypersensitivity responses and direct transfer of immune cells under the renal capsule to characterize nephritogenic effector cells from kdkd donor mice. Lyt-2+, L3T4- T cells from the peripheral lymphoid organs of nephritic kdkd mice, after adoptive transfer into cyclophosphamide-pretreated CBA/Ca recipients, mediate an antigen-specific delayed-type hypersensitivity response to renal tubular basement membrane antigens. These cells are restricted by gene products in H-2Kk; they are also present in nephritic, but not in control kidneys. We have also observed this same phenotypic subpopulation of kdkd lymphocytes mediate a destructive interstitial renal lesion within 7 days of being placed under the kidney capsule of CBA/Ca mice. These findings suggest that T lymphocytes reactive to a parenchymal tubular antigen are of substantial importance in the development of spontaneous interstitial nephritis in kdkd mice.

Spontaneous interstitial nephritis in kdkd mice. II. Characterization of a tubular antigen-specific, H-2K-restricted Lyt-2+ effector T cell that mediates destructive tubulointerstitial injury

In this report, we have examined the effector T cell repertoire in the spontaneous interstitial nephritis of kdkd mice. Lymph node cells from nephritic kdkd mice are capable of transferring this disease into thymectomized, irradiated, and bone marrow-reconstituted CBA/Ca recipients. CBA/Ca mice do not spontaneously develop interstitial nephritis and are normally resistant to the adoptive transfer of nephritic cells, a resistance that in the short term can be attenuated with low-dose cyclophosphamide. We therefore used delayed-type hypersensitivity responses and direct transfer of immune cells under the renal capsule to characterize nephritogenic effector cells from kdkd donor mice. Lyt-2+, L3T4- T cells from the peripheral lymphoid organs of nephritic kdkd mice, after adoptive transfer into cyclophosphamide-pretreated CBA/Ca recipients, mediate an antigen-specific delayed-type hypersensitivity response to renal tubular basement membrane antigens. These cells are restricted by gene products in H-2Kk; they are also present in nephritic, but not in control kidneys. We have also observed this same phenotypic subpopulation of kdkd lymphocytes mediate a destructive interstitial renal lesion within 7 days of being placed under the kidney capsule of CBA/Ca mice. These findings suggest that T lymphocytes reactive to a parenchymal tubular antigen are of substantial importance in the development of spontaneous interstitial nephritis in kdkd mice.

Inhibition of human natural cytotoxicity by macromolecular antiproteases

Human natural cell-mediated cytotoxicity is inhibited by macromolecular protease inhibitors. Human plasma alpha 1 antiproteases are more effective than the plant antiproteases lima bean trypsin inhibitor and soybean trypsin inhibitor for reduction of cytotoxicity to the "slow" targets T24 human bladder carcinoma and NKI-1 melanoma. This inhibition of natural cytotoxicity is more readily demonstrable in serum-free medium containing crystalline bovine serum albumin than in medium containing fetal calf serum. Although electrophoretically homogeneous plasma alpha 1 antitrypsin inhibits natural cytotoxicity, partially purified alpha 1 antitrypsin preparations that contain several apha 1 proteins are more inhibitory at equivalent trypsin inhibitory capacities. Partially purified alpha 1 antichymotrypsin with no antitrypsin activity is an extremely potent inhibitor. Thus, it seems likely that several of the plasma antiproteases, including alpha 1 antitrypsin and alpha 1 antichymotrypsin, are capable of influencing natural cytotoxicity. These data indicate that serine-dependent proteases hae a critical role in triggering and/or effecting cell-mediated cytolysis. Furthermore, since alpha 1 antichymotrypsin and alpha 1 antitrypsin are acute phase proteins, the increase in plasma concentration or turnover rates of the proteins could influence natural killer cell activity in vivo.

Inhibition of human natural cytotoxicity by macromolecular antiproteases

Human natural cell-mediated cytotoxicity is inhibited by macromolecular protease inhibitors. Human plasma alpha 1 antiproteases are more effective than the plant antiproteases lima bean trypsin inhibitor and soybean trypsin inhibitor for reduction of cytotoxicity to the "slow" targets T24 human bladder carcinoma and NKI-1 melanoma. This inhibition of natural cytotoxicity is more readily demonstrable in serum-free medium containing crystalline bovine serum albumin than in medium containing fetal calf serum. Although electrophoretically homogeneous plasma alpha 1 antitrypsin inhibits natural cytotoxicity, partially purified alpha 1 antitrypsin preparations that contain several apha 1 proteins are more inhibitory at equivalent trypsin inhibitory capacities. Partially purified alpha 1 antichymotrypsin with no antitrypsin activity is an extremely potent inhibitor. Thus, it seems likely that several of the plasma antiproteases, including alpha 1 antitrypsin and alpha 1 antichymotrypsin, are capable of influencing natural cytotoxicity. These data indicate that serine-dependent proteases hae a critical role in triggering and/or effecting cell-mediated cytolysis. Furthermore, since alpha 1 antichymotrypsin and alpha 1 antitrypsin are acute phase proteins, the increase in plasma concentration or turnover rates of the proteins could influence natural killer cell activity in vivo.