Nanovesicles released by OKT3 hybridoma express fully active antibodies

Recent findings have shown that nanovesicles preparations from either primary immune cells culture supernatants or plasma contain immunoglobulins, suggesting that a natural way of antibody production may be through exosome release. To verify this hypothesis, we used the OKT3 hybridoma clone, which produces a murine IgG2a monoclonal antibody used to reduce rejection in patients undergoing organ transplantation. We showed exosome-associated immunoglobulins in hybridoma supernatants, by Western blot, nanoscale flow cytometry and immunocapture-based ELISA. The OKT3-exo was also being able to trigger cytokines production in both CD4 and CD8 T cells. These results show that nanovesicles contain immunoglobulin and could be used for immunotherapy. These data could lead to a new approach to improve the effectiveness of therapeutic antibodies by exploiting their natural property to be expressed on nanovesicle membrane, that probably render them more stable and as a consequence more capable to interact with their specific ligand in the best way.

Versatile and rapid microfluidics-assisted antibody discovery

Recent years have seen unparalleled development of microfluidic applications for antibody discovery in both academic and pharmaceutical research. Microfluidics can support native chain-paired library generation as well as direct screening of antibody secreting cells obtained by rodent immunization or from the human peripheral blood. While broad diversities of neutralizing antibodies against infectious diseases such as HIV, Ebola, or COVID-19 have been identified from convalescent individuals, microfluidics can expedite therapeutic antibody discovery for cancer or immunological disease indications. In this study, a commercially available microfluidic device, Cyto-Mine, was used for the rapid identification of natively paired antibodies from rodents or human donors screened for specific binding to recombinant antigens, for direct screening with cells expressing the target of interest, and, to our knowledge for the first time, for direct broad functional IgG antibody screening in droplets. The process time from cell preparation to confirmed recombinant antibodies was four weeks. Application of this or similar microfluidic devices and methodologies can accelerate and enhance pharmaceutical antibody hit discovery.

Developing an Arrayed CRISPR-Cas9 Co-Culture Screen for Immuno-Oncology Target ID

Immunotherapies including PD-L1 blockade have shown remarkable increases in the T cell-directed antitumor response; however, efficacy is seen only in a minority of patients. Recently, pooled CRISPR-Cas9 knockout (CRISPRn) screens in tumor/immune co-culture systems have identified a number of genes that confer resistance to T cell killing in pathways including antigen presentation and cytokine signaling, providing insight into tumor mechanisms that cause resistance to immunotherapies. The development of an arrayed CRISPRn screen in a tumor/immune co-culture system would allow the identification of novel targets for immuno-oncology, characterization of hits from pooled screens, and multiple assay endpoints to be measured per gene. Here, a small-scale arrayed CRISPRn screen was successfully developed to investigate the effects on a co-culture of T cells and Cas9-expressing PC9 lung adenocarcinoma cells modified to express anti-CD3 antibody on the cell surface (PC9-OKT3 T cell system). A focused CRISPRn library was designed to target genes involved in known resistance mechanisms (including antigen presentation, cytokine signaling, and apoptosis) as well as genes involved in immune synapse interactions. The viability of PC9 cells was assessed in two-dimensional adherent co-cultures via longitudinal imaging analysis. Knockout of epidermal growth factor receptor (EGFR) and PLK1 in tumor cells cultured alone or with T cells resulted in increased tumor cell death, as expected, whereas knockout of the test gene ICAM1 showed subtle donor-specific resistance to T cell killing. Taken together, these data provide proof of concept for arrayed CRISPRn screens in tumor/immune co-culture systems and warrant further investigation of in vitro co-culture models.

Novel T cells with improved in vivo anti-tumor activity generated by RNA electroporation

The generation of T cells with maximal anti-tumor activities will significantly impact the field of T-cell-based adoptive immunotherapy. In this report, we found that OKT3/IL-2-stimulated T cells were phenotypically more heterogeneous, with enhanced anti-tumor activity in vitro and when locally administered in a solid tumor mouse model. To further improve the OKT3/IL-2-based T cell manufacturing procedure, we developed a novel T cell stimulation and expansion method in which peripheral blood mononuclear cells were electroporated with mRNA encoding a chimeric membrane protein consisting of a single-chain variable fragment against CD3 and the intracellular domains of CD28 and 4-1BB (OKT3-28BB). The expanded T cells were phenotypically and functionally similar to T cells expanded by OKT3/IL-2. Moreover, co-electroporation of CD86 and 4-1BBL could further change the phenotype and enhance the in vivo anti-tumor activity. Although T cells expanded by the co-electroporation of OKT3-28BB with CD86 and 4-1BBL showed an increased central memory phenotype, the T cells still maintained tumor lytic activities as potent as those of OKT3/IL-2 or OKT3-28BB-stimulated T cells. In different tumor mouse models, T cells expanded by OKT3-28BB RNA electroporation showed anti-tumor activities superior to those of OKT3/IL-2 T cells. Hence, T cells with both a less differentiated phenotype and potent tumor killing ability can be generated by RNA electroporation, and this T cell manufacturing procedure can be further optimized by simply co-delivering other splices of RNA, thus providing a simple and cost-effective method for generating high-quality T cells for adoptive immunotherapy.

A proteomic view at T cell costimulation

The "two-signal paradigm" in T cell activation predicts that the cooperation of "signal 1," provided by the T cell receptor (TCR) through engagement of major histocompatility complex (MHC)-presented peptide, with "signal 2″ provided by costimulatory molecules, the prototype of which is CD28, is required to induce T cell effector functions. While the individual signalling pathways are well understood, little is known about global changes in the proteome pattern during TCR/CD28-mediated activation. Therefore, comparative 2-DE-based proteome analyses of CD3(+) CD69(-) resting T cells versus cells incubated with (i) the agonistic anti-CD3 antibody OKT3 mimicking signal 1 in absence or presence of IL-2 and/or with (ii) the agonistic antibody 15E8 triggering CD28-mediated signaling were performed. Differentially regulated spots were defined leading to the identification of proteins involved in the regulation of the metabolism, shaping and maintenance of the cytoskeleton and signal transduction. Representative members of the differentially expressed protein families, such as calmodulin (CALM), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), L-lactate dehydrogenase (LDH), Rho GDP-dissociation inhibitor 2 (GDIR2), and platelet basic protein (CXCL7), were independently verified by flow cytometry. Data provide a detailed map of individual protein alterations at the global proteome level in response to TCR/CD28-mediated T cell activation.

Ex vivo expansion of human CD8+ T cells using autologous CD4+ T cell help

Background

Using in vivo mouse models, the mechanisms of CD4⁺ T cell help have been intensively investigated. However, a mechanistic analysis of human CD4⁺ T cell help is largely lacking. Our goal was to elucidate the mechanisms of human CD4⁺ T cell help of CD8⁺ T cell proliferation using a novel in vitro model.

Methods/Principal Findings

We developed a genetically engineered novel human cell-based artificial APC, aAPC/mOKT3, which expresses a membranous form of the anti-CD3 monoclonal antibody OKT3 as well as other immune accessory molecules. Without requiring the addition of allogeneic feeder cells, aAPC/mOKT3 enabled the expansion of both peripheral and tumor-infiltrating T cells, regardless of HLA-restriction. Stimulation with aAPC/mOKT3 did not expand Foxp3⁺ regulatory T cells, and expanded tumor infiltrating lymphocytes predominantly secreted Th1-type cytokines, interferon-γ and IL-2. In this aAPC-based system, the presence of autologous CD4⁺ T cells was associated with significantly improved CD8⁺ T cell expansion in vitro. The CD4⁺ T cell derived cytokines IL-2 and IL-21 were necessary but not sufficient for this effect. However, CD4⁺ T cell help of CD8⁺ T cell proliferation was partially recapitulated by both adding IL-2/IL-21 and by upregulation of IL-21 receptor on CD8⁺ T cells.

Conclusions

We have developed an in vitro model that advances our understanding of the immunobiology of human CD4⁺ T cell help of CD8⁺ T cells. Our data suggests that human CD4⁺ T cell help can be leveraged to expand CD8⁺ T cells in vitro.

Teplizumab for treatment of type 1 diabetes (Protégé study): 1-year results from a randomised, placebo-controlled trial

BACKGROUND

Findings of small studies have suggested that short treatments with anti-CD3 monoclonal antibodies that are mutated to reduce Fc receptor binding preserve β-cell function and decrease insulin needs in patients with recent-onset type 1 diabetes. In this phase 3 trial, we assessed the safety and efficacy of one such antibody, teplizumab.

METHODS

In this 2-year trial, patients aged 8-35 years who had been diagnosed with type 1 diabetes for 12 weeks or fewer were enrolled and treated at 83 clinical centres in North America, Europe, Israel, and India. Participants were allocated (2:1:1:1 ratio) by an interactive telephone system, according to computer-generated block randomisation, to receive one of three regimens of teplizumab infusions (14-day full dose, 14-day low dose, or 6-day full dose) or placebo at baseline and at 26 weeks. The Protégé study is still underway, and patients and study staff remain masked through to study closure. The primary composite outcome was the percentage of patients with insulin use of less than 0·5 U/kg per day and glycated haemoglobin A(1c) (HbA(1C)) of less than 6·5% at 1 year. Analyses included all patients who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov, number NCT00385697.

FINDINGS

763 patients were screened, of whom 516 were randomised to receive 14-day full-dose teplizumab (n=209), 14-day low-dose teplizumab (n=102), 6-day full-dose teplizumab (n=106), or placebo (n=99). Two patients in the 14-day full-dose group and one patient in the placebo group did not start treatment, so 513 patients were eligible for efficacy analyses. The primary outcome did not differ between groups at 1 year: 19·8% (41/207) in the 14-day full-dose group; 13·7% (14/102) in the 14-day low-dose group; 20·8% (22/106) in the 6-day full-dose group; and 20·4% (20/98) in the placebo group. 5% (19/415) of patients in the teplizumab groups were not taking insulin at 1 year, compared with no patients in the placebo group at 1 year (p=0·03). Across the four study groups, similar proportions of patients had adverse events (414/417 [99%] in the teplizumab groups vs 98/99 [99%] in the placebo group) and serious adverse events (42/417 [10%] vs 9/99 [9%]). The most common clinical adverse event in the teplizumab groups was rash (220/417 [53%] vs 20/99 [20%] in the placebo group).

INTERPRETATION

Findings of exploratory analyses suggest that future studies of immunotherapeutic intervention with teplizumab might have increased success in prevention of a decline in β-cell function (measured by C-peptide) and provision of glycaemic control at reduced doses of insulin if they target patients early after diagnosis of diabetes and children.

FUNDING

MacroGenics, the Juvenile Diabetes Research Foundation, and Eli Lilly.

Une étape vers la restauration de la tolérance immunitaire au soi dans les maladies auto-immunes humaines

In developed countries the incidence of autoimmune insulin-dependent or type 1 diabetes as the one of all autoimmune diseases has steadily increased over the last decades. Conventional therapy of type 1 diabetes is essentially palliative namely, chronic delivery of exogenous insulin that is associated with major constraints (multiple daily parenteral administration, serious risks linked to hypoglycemic episodes) and incomplete effectiveness in preventing severe degenerative complications. This explains the growing attention on modern therapeutic strategies using biological agents such as CD3 monoclonal antibodies that allow 'reprogramming' the immune system to restore self-tolerance to pancreatic beta cell antigens. This strategy which proved successful in the experimental setting has recently been translated to the clinic with very encouraging results. CD3 antibodies may represent a new category of drugs affording a real cure for autoimmunity namely, inhibiting the pathogenic immune response while preserving the host reactivity to unrelated antigens.

Immunosuppressive preconditioning or induction regimens : evidence to date

The success of solid organ transplantation has been directly related to the development of immunosuppressive drug therapies. Preconditioning or induction therapy was developed to reduce early immunological and nonimmunological renal injury, with the goal of increasing long-term graft survival. However, the routine induction of immunological tolerance to solid organ allograft is currently not achievable because of the morbidity and mortality related to the immunosuppressive regimens themselves. The different therapeutic preconditioning or induction agents and their associated effects on cellular rejection, graft survival outcomes and the need for multiagent post-transplant maintenance therapy are reviewed.

All-trans retinoic acid stimulates IL-2-mediated proliferation of human T lymphocytes: early induction of cyclin D3

Vitamin A is established as an important immune regulator, but the mechanisms whereby vitamin A regulates T cell biology are poorly defined. In this study, we show that an active metabolite of vitamin A, all-trans retinoic acid (RA), potently stimulates T cell proliferation by modulating IL-2-mediated signaling downstream of IL-2R and independent of the induction of IL-2. Thus, at concentrations as low as 0.1 nM, RA enhanced the division of normal human T lymphocytes that were simultaneously stimulated with anti-CD3 mAbs and saturating concentrations of IL-2. At the optimal concentration of RA (50 nM), a 3-fold increase in T cell proliferation was observed. The induced proliferation was preceded by increased phosphorylation of the retinoblastoma protein and enhanced G1- to S-phase progression. Interestingly, the promitogenic effect of RA was found to be particularly directed toward increased expression of cyclin D3 at both the mRNA and protein level. Furthermore, the stimulatory effect of RA on cyclin D3 expression as well as on cell proliferation was completely abolished in the presence of the JAK inhibitor AG-490 or blocking IL-2R alpha mAbs, and RA also enhanced cyclin D3 expression and T cell proliferation in the presence of IL-2 alone. Finally, we showed that the proliferative effect of RA was mimicked by agonists of the retinoic acid receptor (RAR) and completely inhibited by a RAR-selective antagonist. In conclusion, our results indicate that RA, via RAR, stimulates IL-2-induced signaling in a JAK-dependent manner to enhance cyclin D3 expression and thereby promote T cell proliferation.

Effect of FK506 on the interleukin 15-driven proliferation and apoptosis of anti-CD3-activated umbilical cord blood T cells

BACKGROUND

Increased susceptibility of umbilical cord blood (CB) T cells to FK506 immunosuppression may contribute to the lessened severity of graft-vs-host disease in CB transplantation.

OBJECTIVE

To investigate the FK506 sensitivity of interleukin 15 (IL-15)- and IL-2-driven proliferation and apoptosis of anti-CD3-stimulated CB T cells compared with adult peripheral blood (APB) T cells.

METHODS

Surface flow cytometric analysis (CD25 and CD95), carboxyfluorescein diacetae succinimidyl ester staining to track CD3+ T-cell division, and flow cytometric analysis of apoptotic cell death using Annexin V were performed to determine the effect of FK506 on CD3+ T-cell activation and apoptosis after anti-CD3 stimulation in the presence of IL-15 or IL-2.

RESULTS

IL-15 is superior to IL-2 in promoting CD25 expression and proliferation of anti-CD3-stimulated CB and APB T cells. Although IL-15-driven proliferation evaluated by carboxyfluorescein diacetae succinimidyl ester staining revealed comparable sensitivity to FK506 in anti-CD3-stimulated CB and APB T cells, IL-15-driven CD25 up-regulation in CB T cells was more sensitive to FK506 inhibition than APB T cells. FK506 down-regulated anti-CD3-induced apoptosis in CB and APB T cells (P < .01). However, the FK506 sensitivity of anti-CD3-induced T-cell apoptosis was lost in IL-15-supplemented CB cultures (P = .51) but not in corresponding APB cultures (P = .002). The IL-15-enhanced Fas expression on CB T cells (CD95) was decreased by FK506, similar to that observed with adults.

CONCLUSIONS

We observed differential FK506 sensitivity of IL-15-driven CD25 up-regulation and apoptotic response comparing CB and APB T cells. This finding suggests the potential therapeutic benefit of FK506 in ameliorating graft-vs-host disease by decreasing IL-15-driven donor T-cell proliferation without inhibiting associated activation-induced apoptosis during CB transplantation.

Construction and characterization of a humanized anti-human CD3 monoclonal antibody 12F6 with effective immunoregulation functions

12F6 is a murine anti-human CD3 monoclonal antibody, which competes with OKT3 for binding to human T cells and possesses more effective T-cell suppression and activation properties compared to OKT3. It thus exhibits the potential to be developed as an immunoregulation agent for manipulating T-cell functions and preventing acute allograft rejection. In an attempt to minimize the immunogenicity of murine 12F6 (m12F6) for potential clinical application, a humanized version of 12F6, denoted as hu12F6, was successfully constructed by complementary determining region (CDR) grafting and shown to maintain both T-cell activation and suppression activities similar to m12F6. Furthermore, in order to reduce the first dose reaction syndrome caused by T-cell activation following the first administration of anti-CD3 antibodies, two amino acid mutations were introduced into the Fc region of hu12F6, resulting in the Fc-mutated 12F6 humanized antibody (hu12F6mu). This Fc-mutated version displayed a similar antigen-binding affinity and specificity compared with hu12F6 and m12F6 but with much weaker FcR binding activity. hu12F6mu was shown to be much less potent in the induction of T-cell proliferation, cytokine release (tumour necrosis factor-alpha, interferon-gamma and interleukin-10) and early activation marker expression on the cell surface (CD69 and CD25) than parental 12F6 and OKT3 did. In contrast, hu12F6mu was effective in modulating T-cell receptor/CD3 and inhibiting mixed lymphocyte reaction with a similarity as compared to m12F6 and OKT3. In conclusion, the resultant hu12F6mu was much less mitogenic to T cells but retained potent immunosuppression, suggesting it might be an alternative to OKT3 as an immunosuppressive drug with less immunogenicity and toxicity for clinical application.

Combination therapy with tumor cell-pulsed dendritic cells and activated lymphocytes for patients with disseminated carcinomas

This phase I study was performed to assess the safety and immune response of tumor cell-pulsed dendritic cell (DC) vaccine therapy against cancer patients with multiple metastases. DCs, generated from adherent cells of peripheral blood mononuclear cells (PBMCs) using interleukin-4 (IL-4) and granulocyte/monocyte colony-stimulating factor, were loaded with autologous necrotic whole tumor cells. Thereafter, the DCs were matured with culture supernatants of OK-432-stimulated PBMCs. Activated lymphocytes were also induced from non-adherent cells of PBMCs using OKT-3 and IL-2. Patients received a subcutaneous injection of DCs loaded with tumor cells every 2 weeks and received an intravenous injection of activated lymphocytes every 4 weeks. This combination therapy was named tumor-pulsed DC vaccine therapy. Tumor-pulsed DC vaccine therapy was continued as long as possible in 19 patients. No particular adverse reactions, except for low-grade fever, were found. The patients could be divided into two groups according to the survival time, i.e., 6 responders (long survival patients) and 13 non-responders (short survival patients). Based on the laboratory data of responders, eligibility criteria were determined. Using the eligibility criteria, a phase I/II study was recently performed with 15 patients. A delayed-type hypersensitivity reaction against tumor-pulsed DCs became positive in 13 of the 15 patients within 6 months after the therapy. This therapy was again safe, and no evidence of autoimmune disease was noted. The survival time of these 15 patients was significantly prolonged compared with that of the 13 non-responders of the phase I study (p < 0.0001). This continuous tumor-pulsed DC vaccine therapy was well tolerated in patients with disseminated carcinomas.

TCR stimulation with modified anti-CD3 mAb expands CD8+ T cell population and induces CD8+CD25+ Tregs

Modified anti-CD3 mAbs are emerging as a possible means of inducing immunologic tolerance in settings including transplantation and autoimmunity such as in type 1 diabetes. In a trial of a modified anti-CD3 mAb [hOKT3gamma1(Ala-Ala)] in patients with type 1 diabetes, we identified clinical responders by an increase in the number of peripheral blood CD8+ cells following treatment with the mAb. Here we show that the anti-CD3 mAb caused activation of CD8+ T cells that was similar in vitro and in vivo and induced regulatory CD8+CD25+ T cells. These cells inhibited the responses of CD4+ cells to the mAb itself and to antigen. The regulatory CD8+CD25+ cells were CTLA4 and Foxp3 and required contact for inhibition. Foxp3 was also induced on CD8+ T cells in patients during mAb treatment, which suggests a potential mechanism of the anti-CD3 mAb immune modulatory effects involving induction of a subset of regulatory CD8+ T cells.

Antibody induction therapy in renal transplant patients receiving calcineurin-inhibitor immunosuppressive regimens: a comparative review

Acute rejection during the first year post-transplant is a key predictor of graft survival after renal transplantation. Use of induction therapy with a lymphocyte-depleting agent or an interleukin-2 receptor (IL-2R) antagonist can provide effective protection against rejection in the first critical weeks and months post-transplant. Polyclonal lymphocyte-depleting antibodies are associated with a low incidence of rejection but evidence of their benefit in terms of graft survival is lacking. Thymoglobulin appears to offer superior graft outcomes compared with generic antithymocyte globulin (ATG). The most frequent adverse events are symptoms of cytokine release syndrome, leukopenia, thrombocytopenia, and tachycardia; data on whether polyclonal antibody use increases the risk of lymphoma are conflicting. Muromonab CD3 (OKT3), a monoclonal lymphocyte-depleting antibody, is efficacious but a high incidence of cytokine release syndrome and increased risk of post-transplant lymphoproliferative disease have limited its use. Following their recent introduction, the IL-2R antagonists basiliximab and daclizumab are now used widely, after randomized trials demonstrated that addition to calcineurin inhibitor-based therapy significantly reduced acute rejection by approximately 30-40%. Meta-analyses and registry analysis suggest that addition of an IL-2R antagonist may improve graft survival. The safety profile of IL-2R antagonists is indistinguishable from placebo, with no apparent difference in incidence of infection or post-transplant lymphoproliferative disease. IL-2R antagonists and polyclonal lymphocyte-depleting antibodies (with delayed cyclosporine) offer equivalent efficacy in standard-risk populations; in a trial of high-risk patients, acute rejection rate and graft outcomes were improved with Thymoglobulin. Tolerability is superior with IL-2R antagonists: cytokine release syndrome and hematologic disturbances (notably leukopenia) are significantly more frequent with polyclonal antibodies. Cytomegalovirus infection may also be more common with lymphocyte-depleting antibodies. Thus, in patients at high risk of graft loss, Thymoglobulin may be the preferred choice for induction therapy, while for all other patients, IL-2R antagonists should be considered first-line choice for induction therapy.

Role for NKG2-A and NKG2-C surface receptors in chronic CD4+ T-cell responses

The participation of CD94 and NKG2 gene family members in the function of NK cells and CD8+ cytolytic cells has recently been addressed in detail. However, the role that these molecules play in the key CD4+ regulatory cells remains largely unexplored. This study has examined the expression and regulation of CD94 and NKG2 genes in purified human peripheral CD4+ cells stimulated with several agents. We found a constitutive expression of NKG2-E in CD94-depleted resting peripheral CD4+ cells, whereas inductions of NKG2-A and NKG2-C required chronic cell activation and occurred after expression of CD94. We found that CD3-mediated stimulation induces the expression of CD94 first by day 5 of culture, followed by NKG2-A by day 15 and finally NKG2-C, which is not detected until 20 days after repeated stimulation. This pattern of gene expression differs sharply from that observed in purified CD8+ T cells, where mRNA from all NKG2 gene family members are detected after 5 days of stimulation. Selective activation of TCR V beta 2-bearing cells with toxic shock syndrome toxin-1 superantigen reveals that mRNA induction of NKG2-A and NKG2-C genes is significantly influenced by the presence of cytokines (IL-10 and TGF-beta) and by the restimulation of the cells. In addition, the occupancy of the CD94/NKG2-A receptor expressed on these superantigen-stimulated CD4+ T lymphocytes abrogates TNF-alpha and IFN-gamma production, whereas NKG2-C enhances production of these cytokines. Taken together our results reveal strict gene regulatory mechanisms for CD94 and NKG2 gene expression on CD4+ cells that are different from those governing the expression of these same genes in CD8+ cells. The results suggest that these genes also participate in chronic CD4+ T-cell responses.

Regulation of human auto- and alloreactive T cells by indoleamine 2,3-dioxygenase (IDO)–producing dendritic cells: too much ado about IDO?

Although dendritic cells (DCs) strongly stimulate the immune response, they can also induce unresponsiveness. Recently, a human monocyte-derived DC subpopulation was described that constitutively expresses indoleamine 2,3-dioxygenase (IDO). These DCs were defined as nonadherent CD123+/CC chemokine receptor 6+ (CCR6+) cells that suppress the allogeneic T-cell response. In the present study, we generated nonadherent, mature DCs from human blood monocytes. As expected, in addition to the classic markers, these cells expressed CD123 and CCR6. Reverse transcription–polymerase chain reaction (RT-PCR), however, did not show IDO gene transcription, nor did we detect enzymatic IDO activity. Treating the cells with interferon-γ (IFN-γ) resulted in significant IDO production. Subsequently, we studied the regulatory properties of IDO-producing DCs on autologous and allogeneic T-cell responses. Neither OKT3-stimulated T cells of healthy donors nor myelin basic protein (MBP)–specific T cells of patients with multiple sclerosis (MS) were suppressed by autologous IDO DCs. However, whereas IDOneg DCs supported further stimulation of preactivated MBP-specific T cells of an MS patient, IDOpos DCs had lost this capacity. The allogeneic T-cell response was only marginally suppressed by IDO DCs. Our findings show that nonadherent CD123+/CCR6+ human DCs do not constitutively express IDO, and, even if they express the enzyme after IFN-γ treatment, they possess only limited T-cell regulatory function.

Refractory acute kidney transplant rejection with CD20 graft infiltrates and successful therapy with rituximab

Acute rejection is an expected event after transplantation and has been associated with poor long-term kidney transplant outcome. The presence of B cells in the kidney graft with acute rejection is thought to be an omnious sign, as it has been associated with poor graft outcome. There is no definitive treatment for acute rejection with B cells in the graft. Rituximab, a humanized monoclonal antibody against CD20, has been used in the treatment of B cell lymphoma. We present the case of a 49-yr-old Caucasian male with early acute kidney allograft rejection that was refractory to high doses of steroids and rabbit anti-thymocyte globulin (thymoglobulin). Repeat renal biopsy revealed T cell and B cells in the kidney graft and responded to the combination of rituximab and muromonab (a mouse monoclonal antibody to CD3 receptor). Over 9 months post-transplant, the patient remains rejection free with a serum creatinine of 1.7 mg/dL.

[Eukaryotic expression of anti-CD3 single chain Fv antibody gene and the characterization of its bioactivities]

AIM

To express anti-CD3 scFv in Hela cells and investigate its biological activity.

METHODS

DNA fragment encoding anti-CD3 scFv was inserted into eukaryotic expression vector pDisplay. The recombinant expression vector was sequenced and then transfected into Hela cells by electroporation method. The expression of anti-CD3 scFv was identified by in situ hybridization. In-vitro T lymphocyte activation was then detected by (3)H-TdR incoporation method. Anti-CD3 scFv gene-transfected Hela cells were co-cultured with T cells and cytotoxicity was measured by MTT colorimetry.

RESULTS

Anti-CD3 scFv gene was correctly inserted into pDisplay and expressed in Hela cells. The secreted anti-CD3 scFv was able to activate T lymphocytes in the presence of anti-CD28 mAb. Cytotoxicity could be observed when anti-CD3 scFv gene-transfected Hela cells were mixed and co-cultured with T lymphocytes.

CONCLUSION

Anti-CD3 scFv expressed by Hela cells can activate T lymphocytes.

The production and purification of the human T-cell receptors, the CD3∊γ and CD3∊δ heterodimers: complex formation and crystallization with OKT3, a therapeutic monoclonal antibody

Human CD3 is an essential multisubunit complex that plays a fundamental role in T-cell signalling, T-cell development and surface expression of the alphabeta T-cell receptor. The CD3 complex comprises the CD3epsilongamma and CD3epsilondelta heterodimers and the CD3zetazeta homodimer. Here, the expression of the human CD3epsilongamma and CD3epsilondelta heterodimers, both of which were expressed as single-chain polypeptides, is reported. Following refolding, functional heterodimers were immunoaffinity purified from improperly folded heterodimers using OKT3, a therapeutic monoclonal antibody specific for the CD3epsilon chain. Subsequently, the Fab fragment of OKT3 was used to complex individually with the CD3epsilongamma and CD3epsilondelta heterodimers. Crystals of scCD3epsilongamma-FabOKT3 were grown using 15%(w/v) PEG 3350, 200 mM potassium fluoride, 100 mM Tris-HCl pH 8.0. Crystals of scCD3epsilondelta-FabOKT3 were grown using 20%(w/v) PEG 3350, 200 mM potassium formate, 100 mM Tris-HCl pH 8.0, 2%(v/v) MPD. Crystals of both complexes diffract to beyond 3 A resolution. scCD3epsilongamma-FabOKT3 crystals belonged to space group P2(1), with unit-cell parameters a = 67.70, b = 55.77, c = 96.05 A, beta = 100.85 degrees and one complex per asymmetric unit. scCD3epsilondelta-FabOKT3 crystals belong to space group P2(1), with unit-cell parameters a = 101.67, b = 50.36, c = 138.7 A, beta = 108.84 degrees, suggesting two complexes per asymmetric unit.

The clinical application of monoclonal antibody therapies in renal transplantation

Monoclonal antibodies have become valuable tools for the precise clinical manipulation of the immune system. These highly specific proteins have proven their usefulness in both the treatment and prevention of organ transplant rejection. Indeed, they are the centrepieces of many evolving regimens designed to reduce or eliminate the need for chronic immunosuppression. This manuscript will review the monoclonal antibodies that have made their way into the clinic either as experimental therapies or approved drugs. It will provide a general overview of this class of agents and their mechanisms of action. Standard therapies and potential new applications will be described.

Crystal structure of the human T cell receptor CD3 epsilon gamma heterodimer complexed to the therapeutic mAb OKT3

The CD3 epsilon gamma heterodimer is essential for expression and function of the T cell receptor. The crystal structure of the human CD3 epsilon gamma heterodimer is described to 2.1-A resolution complexed with OKT3, a therapeutic mAb that not only activates and tolerizes mature T cells but also induces regulatory T cells. The mode of CD3 epsilon gamma dimerization provides a general structural basis for CD3 assembly and maps candidate T cell antigen receptor docking sites, including a duplicated linear region rich in acidic residues that is unique to human CD3 epsilon. OKT3 binds to an atypically small area of CD3 epsilon and has a low affinity for the isolated CD3 epsilon gamma heterodimer. The structure of the OKT3/CD3 epsilon gamma complex has implications for T cell signaling and therapeutic design.

Transplantation of cultured islets from two-layer preserved pancreases in type 1 diabetes with anti-CD3 antibody

We sought to determine whether or not optimizing pancreas preservation, islet processing, and induction immunosuppression would facilitate sustained diabetes reversal after single-donor islet transplants. Islets were isolated from two-layer preserved pancreata, purified, cultured for 2 days; and transplanted into six C-peptide-negative, nonuremic, type 1 diabetic patients with hypoglycemia unawareness. Induction immunosuppression, which began 2 days pretransplant, included the Fc receptor nonbinding humanized anti-CD3 monoclonal antibody hOKT3gamma1 (Ala-Ala) and sirolimus. Immunosuppression was maintained with sirolimus and reduced-dose tacrolimus. Of our six recipients, four achieved and maintained insulin independence with normal HbA1c levels and freedom from hypoglycemia; one had partial islet graft function; and one lost islet graft function 2 weeks post-transplant. The four insulin-independent patients showed prolonged CD4+ T-cell lymphocytopenia; inverted CD4:CD8 ratios; and increases in the percentage of CD4+CD25+ T cells. These cells suppressed the in-vitro proliferative response to donor cells and, to a lesser extent, to third-party cells. Severe adverse events were limited to a transient rash in one recipient and to temporary neutropenia in three. Our preliminary results thus suggest that a combination of maximized viable islet yield, pretransplant islet culture, and preemptive immunosuppression can result in successful single-donor islet transplants.

Extensive temporally regulated reorganization of the lipid raft proteome following T-cell antigen receptor triggering

Signalling by immunoreceptors is orchestrated at specific plasma membrane microdomains, referred to as lipid rafts. Here we present a proteomics approach to the temporal analysis of protein association with lipid rafts following T-cell antigen receptor (TCR) triggering. We show that TCR engagement promotes the temporally regulated recruitment of proteins participating in the TCR signalling cascade to lipid rafts. Furthermore, TCR triggering results in profound modifications in the composition of lipid rafts involving a number of proteins associated either directly or indirectly with both plasma and intracellular membranes. Raft-associated proteins can be clustered according to their temporal profile of raft association. The data identify lipid rafts as highly dynamic structures and reveal a dramatic impact of surface TCR triggering not only on components of the TCR signalling machinery but also on proteins implicated in a number of diverse cellular processes.

[Effect of progesterone and 17beta-estradiol on proinflammatory cytokine costimulatory proliferative activity]

The lymphocyte proliferation is multicomponent mechanism of immune system reactivity. Many costimulatory factors take part in this process. Proinflammatory cytokines (TNF, IL-1 alpha and beta) enhance proliferation of activated lymphocytes. Female steroid hormones inhibit proliferation of mitogen and alloantigen-activated lymphocytes. The aim of this study was to investigate the effect of progesterone and 17 beta-estradiol on the costimulatory proliferative activity of proinflammatory cytokines in vitro. Female steroid hormones inhibit lymphocyte response to antiCD3 antibody. Progesterone had a stronger effect than 17 beta-estradiol (64 and 13% of inhibition respectively). 17 beta-estradiol enhanced the TNF costimulatory effect on the lymphocyte proliferation. Progesterone neutralized this TNF-induced effect and reverted it (inhibition of lymphocyte proliferation was enhanced in the presence of TNF). We found dominant inhibitory effect of progesterone on the TNF costimulatory activity when progesterone and estrogen were added simultaneously. Progesterone and 17 beta-estradiol downregulated costimulatory proliferative activity of IL-1 alpha or beta. Thus female steroid hormones had suppressive effect on the antiCD3-stimulated lymphocyte proliferation. They downregulated costimulatory proliferative activity of IL-1 alpha/beta and had opposite effect on TNF costimulatory activity. Our results suggest possible roles female steroid hormones as regulators on activity of proinflammatory cytokines and their functions in lymphocyte proliferation.

Regulation of cytokine production in human peripheral blood mononuclear cells and allergen-specific th cell clones by 1alpha,25-dihydroxyvitamin D3

BACKGROUND

The steroid hormone 1alpha,25-dihydroxyvitamin D3 (calcitriol), in addition to its crucial role in calcium homeostasis, exerts several effects on the immune system by regulating cell proliferation, differentiation, and maturation. These effects may be exerted through the control of protooncogenes and the regulation of cytokine production.

METHODS

The influence of calcitriol on cytokines secretion by human peripheral blood mononuclear cells (PBMC) isolated from healthy donors, and by allergen-specific T helper (Th) cell clones was studied. PBMC were cultured for 48 h with phorbol myristate acetate (PMA) and ionomycin in the presence or absence of calcitriol. Human Th cell clones were stimulated with either Bet v 1 allergen or anti-CD3 antibodies and PMA. Cytokines were measured in the supernatants by ELISA, and at single-cell level by FACS.

RESULTS

Calcitriol significantly inhibited the production of IL-2, IFN-gamma and IL-12 by PBMC, as well as the percentage of CD4+ T cells containing intracytoplasmic IL-2 and IFN-gamma. Interestingly, calcitriol-treated PBMC induced the production of IL-10 and IL-5, but not of IL-4. The effect of calcitriol was maximal at 10(-7) to 10(-9) and noneffective at 10(-11) M. Calcitriol diminished the secretion of IL-1, TNF-alpha, and MG-CSF in PBMC. Furthermore, calcitriol also decreased the secretion of IL-2 and IFN-gamma by Th1 clones, and of IL-4 by Th2 clones.

CONCLUSIONS

Our data strongly support the notion that calcitriol modulates the production of cytokines in a time- and concentration-dependent manner, and suggest that nonhypercalcemic derivatives of 1alpha,25-dihydroxyvitamin D(3) may be used for new immunosuppressive therapies.

Effect of contaminating red blood cells on OKT3-mediated polyclonal activation of peripheral blood mononuclear cells

Erythrocytes are typically present as impurities in the majority of peripheral blood mononuclear cell (PBMC) preparations. This study was undertaken to investigate the effects of contaminating red blood cells (RBC) on the ability of OKT3 to activate CD4(+) and CD8(+) T cells. Surprisingly, the levels of gamma interferon, tumor necrosis factor alpha, and interleukin-1 beta (IL-1 beta) produced by PBMC upon stimulation by OKT3 were increased (P < 0.05) in a dose-dependent manner when increasing amounts of autologous RBC (RBC-to-PBMC ratios of 2:1, 10:1, and 50:1) were spiked into PBMC preparations. The OKT3-driven induction of the IL-2 receptor (CD25) and the proliferation of T lymphocytes in response to phorbol myristate acetate were not affected by the addition of RBC.

Expression and characterization of recombinant soluble human CD3 molecules: presentation of antigenic epitopes defined on the native TCR-CD3 complex

The TCR-CD3 complex consists of the clonotypic disulfide-linked TCRalphabeta or TCRdeltagamma heterodimers, and the invariant CD3delta, epsilon, gamma and zeta chains. We generated plasmid constructs expressing the extracellular domains of the CD3delta, epsilon or gamma subunits fused to human IgG1 Fc. Recombinant fusion proteins consisting of individual CD3delta, epsilon or gamma subunits reacted poorly with anti-CD3 mAb including G19-4, BC3, OKT3 and 64.1. Co-expression of the CD3epsilon-Ig with either the CD3delta-Ig (CD3epsilondelta-Ig) or the CD3gamma-Ig (CD3epsilongamma-Ig) resulted in fusion proteins with much increased binding to G19-4. A brief acid treatment of the purified CD3epsilondelta-Ig fusion protein substantially improved its binding to BC3, OKT3 and 64.1. Surface plasmon resonance analysis revealed that the dissociation constants for CD3epsilondelta-Ig and anti-CD3 mAb ranged from 10(-8) to 10(-9) M. Based on these results, a single-chain (sc) construct encoding the CD3delta chain linked to the CD3epsilon chain with a flexible linker followed by human IgG1 Fc was expressed. The sc CD3deltaepsilon-scIg reacted with anti-CD3 mAb without requiring acid treatment. Moreover, anti-CD3 mAb bound CD3epsilondelta-Ig at a higher affinity than CD3epsilongamma-Ig, suggesting potential structural differences between the CD3epsilondelta and CD3epsilongamma subunits. In summary, we report the expression of soluble recombinant CD3 proteins that demonstrate structural characteristics of the native CD3 complex expressed on the T cell surface. These CD3 fusion proteins can be used to further analyze the structure of the TCR-CD3 complex, and to identify molecules that can interfere with TCR-CD3-mediated signal transduction by disrupting the interaction between CD3 and TCR subunits.

Efficient gene transfer into human primary blood lymphocytes by surface-engineered lentiviral vectors that display a T cell-activating polypeptide

In contrast to oncoretroviruses, lentiviruses such as human immunodeficiency virus 1 (HIV-1) are able to integrate their genetic material into the genome of nonproliferating cells that are metabolically active. Likewise, vectors derived from HIV-1 can transduce many types of nonproliferating cells, with the exception of some particular quiescent cell types such as resting T cells. Completion of reverse transcription, nuclear import, and subsequent integration of the lentivirus genome do not occur in these cells unless they are activated via the T-cell receptor (TCR) or by cytokines or both. However, to preserve the functional properties of these important gene therapy target cells, only minimal activation with cytokines or TCR-specific antibodies should be performed during gene transfer. Here we report the characterization of HIV-1-derived lentiviral vectors whose virion surface was genetically engineered to display a T cell-activating single-chain antibody polypeptide derived from the anti-CD3 OKT3 monoclonal antibody. Interaction of OKT3 IgGs with the TCR can activate resting peripheral blood lymphocytes (PBLs) by promoting the transition from G(0) to G(1) phases of the cell cycle. Compared to unmodified HIV-1-based vectors, OKT3-displaying lentiviral vectors strongly increased gene delivery in freshly isolated PBLs by up to 100-fold. Up to 48% transduction could be obtained without addition of PBL activation stimuli during infection. Taken together, these results show that surface-engineered lentiviral vectors significantly improve transduction of primary lymphocytes by activating the target cells. Moreover these results provide a proof of concept for an approach that may have utility in various gene transfer applications, including in vivo gene delivery.

Recombinant chimeric OKT3/IgM antibodies for immune suppression: evaluation in a human CD3 transgenic mouse model

ScOKT3-gammaDeltaIgM VAEVD is a recombinant chimeric anti-CD3 antibody variant consisting of the light and heavy variable binding domains of the OKT3 monoclonal antibody and the CH3 and CH4 domains of a human IgM mutation linked by a human IgG3 hinge region. Due to the IgM Fc domains, scOKT3-gammaDeltaIgM VAEVD antibodies are able to form polymeric structures. Independent of their polymerization state, they possess in vitro CD3 modulating and immunosuppressive properties while inducing only minimal T cell activation compared to their monoclonal counterpart. To evaluate the in vivo efficacy of the antibodies, an adjuvant-induced chronic inflammation was established in human CD3 transgenic mice. Administration of four doses of 15 microg of isolated scOKT3-gammaDeltaIgM VAEVD monomers and pentamers significantly reduced diameters of inflamed ankle joints in a manner comparable to the monoclonal antibody OKT3. Additionally, the antibody treatment lead to a significant reduction of the cytokine levels (IL-2, TNF-alpha and INF-gamma) in the mice's sera. These results suggest that scOKT3-gammaDeltaIgM VAEVD antibodies may provide a useful alternative to the OKT3 mAb for clinical immunosuppressive treatment for auto-aggressive diseases or for organ-transplantation.

Naive CD4 T cells inhibit CD28-costimulated R5 HIV replication in memory CD4 T cells

Stimulation with antibodies to CD3 and CD28 coimmobilized on beads can be used to significantly expand T cells ex vivo. With CD4 T cells from HIV-infected patients, this expansion usually is accompanied by complete suppression of viral replication, presumed to be caused by down-regulation of the viral coreceptor CCR5 and up-regulation of CCR5 ligands. Here we show that this suppression occurs in total CD4 T cells acutely infected with R5 HIV, but not in purified CD62L(-) memory CD4 T cells. The lack of complete suppression in these memory cells, typically comprising 10-40% of total CD4 T cells, occurs despite high levels of CCR5 ligand secretion and down-regulation of CCR5. Significantly, adding back naive or CD62L(+) memory CD4 T cells inhibits the viral replication in the CD62L(-) cells, with the naive cells capable of completely repressing the virus. Although this inhibition was previously thought to be specific to bead-bound anti-CD3/CD28 stimulation, we show that the same suppression is obtained with sufficiently strong anti-CD3/B7.1 stimulation. Our results show that inhibitory mechanisms, expressed predominantly by strongly stimulated naive CD4 T cells and mediated independently of CCR5-binding chemokines, play a role in the inhibition of R5 HIV replication in CD4 T cells upon CD28 costimulation.

Use of anti-CD3 x anti-HER2/neu bispecific antibody for redirecting cytotoxicity of activated T cells toward HER2/neu+ tumors

Relapse after adjuvant chemotherapy or high-dose chemotherapy with stem cell transplant for high-risk breast cancer remains high and new strategies that provide additional antitumor effects are needed. This report describes methods to generate highly effective HER2/neu-specific cytotoxic T cells by arming activated T cells with anti-CD3 x anti-HER2/neu bispecific antibody (BsAb). OKT3 and 9184 (anti-HER2) monoclonal antibodies (mAb) were conjugated and used to arm T cells that were subsequently tested in binding, cytotoxicity, and cytokine secretion assays. Armed T cells aggregated and specifically killed HER2/neu(+) breast cancer cells. Cytotoxicity emerged after 6 days of culture, was higher in armed T cells than unarmed T cells at all effector to target ratios (E/T) tested, and increased as the arming dose was increased. At an E/T of 20:1, the mean cytotoxicity of armed activated T cells (ATC) from 10 normal subjects increased by 59 +/- 11% (+/-SD) over that seen in unarmed ATC (p < 0.001) and the mean cytotoxicity of armed ATC from 6 cancer patients increased by 32 +/- 9% above that seen for unarmed ATC (p < 0.0004). After arming, the BsAb persisted on ATC up to 72 h and armed ATC continued to be cytotoxic up to 54 h. The amount of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and granulocyte-macrophage colony-stimulating factor (GM-CSF) secreted was 1699, 922, and 3092 pg/ml/10(6) cells per 24 h, respectively, when armed T cells were exposed to a HER2/neu(+) breast carcinoma cell line. These studies show the feasibility and clinical adaptability of this approach for generating large numbers of anti-HER2-specific, cytotoxic T cells for clinical trials.

Non FcR-binding murine antihuman CD3 monoclonal antibody is capable of productive TCR signalling and induces proliferation in the presence of costimulation

CLB T3/4.A is a non FcR-binding CD3 mAb of the murine IgA isotype, which may be used as an alternative for the mitogenic OKT3 mAb in the treatment of acute cellular rejection after organ transplantation. We studied TCR signalling and T cell activation in response to T3/4.A in normal human PBMC in vitro. T3/4.A induced a rapid rise in free cytoplasmic Ca(2+), not different from the response to mitogenic CD3 mAb. However, protein tyrosine phosphorylation and, particularly, MAPK activation, were reduced as compared to mitogenic CD3 mAb. T3/4.A enhanced expression of both CD69 and CD25, but proliferation and detectable cytokine production did not occur. Addition of either CD28 mAb or IL-2 induced a strong proliferative response, which was accompanied by cytokine production. At higher mAb concentrations, T cell activation decreased, which correlated with TCR downmodulation. To exclude the possibility that activation by T3/4.A depends on interaction of murine IgA Fc with as yet unknown FcR, we showed that also with CD3 mAb F(ab')2 fragments upregulation of activation molecules occurred, as well as proliferation in the presence of costimulation. We conclude that the non FcR-binding murine IgA mAb T3/4.A acts as a partial agonist and leads to proliferation and cytokine production only in the presence of appropriate costimuli. These findings may explain the mitigated cytokine release syndrome observed in vivo with some nonmitogenic CD3 mAbs.

Generation of cytotoxic effector lymphocytes by MLTC using tumor cells genetically modified to secrete interleukin-2

The in vitro generation of effector lymphocytes cytotoxic to cancer cells, was investigated with a mixed lymphocyte-tumor culture (MLTC) system using genetically modified human cancer cells, followed by stimulation with the interleukin (IL)-2 plus immobilized anti-CD3 antibody (IL-2/CD3) system. A gastric cancer cell line, GC022588 (HLA-A2, 24, B35, 55, C1,3), was retrovirally transduced with the human interleukin (IL)-2 gene (GC/IL-2) or the neomycin-resistance gene (GC/Neo). The secretion of biologically active IL-2 was detectable in GC/IL-2 cells but not in GC/Neo or parental GC022588 cells. The cytotoxic activity against the parental GC022588 cells of peripheral blood mononuclear cells (PBMC) was greater among PBMC activated with MLTC using GC/IL-2 than among those activated with MLTC using GC/Neo or without MLTC. The IL-2/CD3 stimulation could efficiently expand the effector lymphocytes without any reduction of the cytotoxic activity generated. The cytotoxic activity generated by this system was reproducible in several HLA-A2- or A24-positive donors. The effector lymphocytes could kill the other adenocarcinoma cells expressing HLA-A2 or A24. The phenotypes of the effector lymphocytes generated with the system were 40% CD4+ and 70% CD8+. Both phenotypes may have been responsible for the cytotoxicity. The removal of adherent cells from PBMC before the MLTC did not affect the generation of cytotoxicity, whereas neutralization of tumor-derived IL-2 with a specific antibody during the MLTC significantly inhibited the generation of cytotoxicity. These results suggest that IL-2 gene-transduction augments the immunogenicity of the tumor cells that efficiently stimulate lymphocytes to be cytotoxic, and that the IL-2/CD3 system may be practical for the expansion of effector lymphocytes for use in adoptive immunotherapy for cancer. The mechanism by which IL-2 gene-modified tumor cells stimulate immune reactivity was discussed.

Recombinant chimeric OKT3 scFv IgM antibodies mediate immune suppression while reducing T cell activation in vitro

OKT3, a mouse anti-human CD3 monoclonal antibody (mAb), is a potent immunosuppressive agent used in clinical transplantation to treat allograft rejection. Two major drawbacks of this therapy are the systemic release of several cytokines due to cross-linking mediated by the mAb between T cells and FcgammaR-bearing cells and the human anti-mouse antibody (HAMA) response. To overcome these side effects, three chimeric OKT3 single chain variable fragment (scFv) IgM antibodies, scOKT3-gamma DeltaIgM wt, scOKT3-gamma DeltaIgM C575S and scOKT3-gamma DeltaIgM VAEVD, were generated. They consist of the light and heavy variable binding domains of OKT3 mAb as well as the CH3 and CH4 domains of different human IgM variants linked with a human IgG3 hinge region to provide more flexibility and stability. Like the native IgM, scOKT3-gamma DeltaIgM antibodies are able to form polymeric structures, which lead to an increase in binding affinity and immunosuppressive potential compared with the parental OKT3 mAb. However, independently of their polymerization, all scOKT3-gamma DeltaIgM constructs do not induce any significant T cell proliferation or cytokine release (IL-2, TNF-alpha and IFN-gamma) in in vitro assays, while their CD3-modulating properties are retained. These results suggest that the use of scOKT3-gamma DeltaIgM antibodies may offer significant advantages over the OKT3 mAb in improving clinical immunosuppressive treatment.

Neonatal (cord blood) T cells can competently raise type 1 and 2 immune responses upon polyclonal activation

In the neonate, cellular immunity has generally been hypothesized as being incompetent. Accumulating evidence from several recent studies, together with our present report, contradicts this hypothesis. T-helper cell and T cytotoxic type 1 and 2 (Th1/Th2 and Tc1/Tc2, respectively) cytokine responses to polyclonal T cell receptor (TCR) activation were assessed in medium-term cultures of human cord blood T cells using intracellular cytokine staining, which could measure the frequencies of cytokine-producing cells. In this study, we examined the responses of cord blood CD4(+) and CD8(+) T cells in regard to the production of interferon (IFN)-gamma and interleukin (IL)-4 and compared the responses with those obtained from T cells of healthy adults. We found that the responses in cord blood T cells activated with TCR stimulation were comparable to those of their adult counterparts. Moreover, the Th/Tc cells that developed in cord blood were as competent as adult cells for both IFN-gamma and IL-4 secretion. In addition, IL-12 production, which is critical for both Th1 and Tc1 responses, was equally comparable in the two groups. The production of two major cross-regulatory cytokines, tumor necrosis factor-alpha and IL-10, was similarly comparable and not significantly different between the two groups. Taken together, these results indicate that, though naive, the neonatal T cell is competent to respond to TCR-mediated stimulation and to produce both type 1 and type 2 cytokines.

MAPK/ERK signaling in activated T cells inhibits CD95/Fas-mediated apoptosis downstream of DISC assembly

When T cells are activated, the expression of the CD95 ligand is elevated, with the purpose of inducing apoptosis in target cells and to later eliminate the activated T cells. We have shown previously that mitogen-activated protein kinase (MAPK or ERK) signaling suppresses CD95-mediated apoptosis in different cellular systems. In this study we examined whether MAPK signaling controls the persistence and CD95-mediated termination of an immune response in activated T cells. Our results show that activation of Jurkat T cells through the T cell receptor immediately suppresses CD95-mediated apoptosis, and that this suppression is mediated by MAPK activation. During the phase of elevated MAPK activity, the activation of caspase-8 and Bid is inhibited, whereas the assembly of a functional death-inducing signaling complex (DISC) is not affected. These results explain the resistance to CD95 responses observed during the early phase of T cell activation and suggest that MAPK-activation deflects DISC signaling from activating caspase-8 and Bid. The physiological relevance of the results was confirmed in activated primary peripheral T cells, in which inhibition of MAPK signaling markedly sensitized the cells to CD95-mediated apoptosis.

Six-year disease-free survival of a patient with metastatic eyelid squamous cell carcinoma and colon adenocarcinoma after repeated postoperative adoptive immunotherapy

A 74-year-old male was affected concurrently with squamous cell carcinoma of the left eyelid and adenocarcinoma of the colon, both with lymph node metastasis. He underwent exenteration of the left orbit with left modified radical neck dissection and subsequently resection of the transverse colon with regional lymph node dissection. The patient has been treated by an adoptive immunotherapy as a sole postoperative modality without receiving any chemotherapeutic agents causing immunosuppression. For the adoptive immunotherapy, autologous peripheral blood lymphocytes were activated with an immobilized anti-CD3 antibody and IL-2 for 14 days (the CD3-AT cells). The infusion with 1.38 x 10(10) CD3-AT cells has been repeated 150 times in total at the time of writing. Neither recurrence nor additional metastasis has been detected for 6 years after surgery.

A pilot study of autologous cancer cell vaccination and cellular immunotherapy using anti-CD3 stimulated lymphocytes in patients with recurrent grade III/IV astrocytoma

The study objectives were to determine; (1) whether activated T cells could be generated from peripheral blood of patients immunized with their own cancer cells, (2) whether adoptive transfer of the activated T cells to patients had toxic effects and (3) whether the infused cells produced clinical responses. Study patients had recurrent, surgically accessible grade III/IV astrocytomas. The patients were tapered off steroids after total surgical resection and immunized with autologous cancer cells plus Bacillus, Calmette and Guerin (BCG). Peripheral blood mononuclear cells were activated with anti-CD3, expanded with interleukin-2 (IL-2) and reinfused to patients. The number of activated T cells that was given back to patients varied between 10(10) and 10(11). Side effects that were observed following immunization and adoptive cell transfer included mainly transient flu-like symptoms. One patient's tumor partially regressed, but there was no effect on survival. Two other patients' tumors regressed, and the patients are apparently disease-free more than 5 and 4 years later. The other six patients' tumors were apparently unaffected by the treatment. Patient age, tumor grade and CD4/CD8 composition of infused cells were positively correlated with clinical responses. Cellular immunotherapy is feasible and is associated with minimal toxicity. Additional appropriately controlled studies will be required to determine whether cellular immunotherapy could be used as a treatment for central nervous system malignancy. Additional studies also will be required to determine the underlying immunological mechanisms.

In vitro characterization of five humanized OKT3 effector function variant antibodies

Orthoclone OKT 3 (mOKT3) is a highly effective agent for the reversal of steroid-resistant renal allograft rejection. However, its wider use has been limited by the development of a human anti-mouse antibody response (HAMA) and by the "cytokine release syndrome" (CRS). CRS has been associated with T cell/monocyte activation and, secondarily, with activation of the complement cascade. These processes are mediated through Abs' Fc regions by their abilities to cross-link T cells and mononuclear cells and to activate complements. To alleviate these problems, a group of five huIgG1- and huIgG4-based OKT3 wild-type antibodies and their corresponding Fc mutants with altered residues at amino acids 234, 235, and 318, reported to be required for FcgammaRI and FcgammaRII binding and complement fixation, were constructed. Characterization of these humanized OKT3 Abs, denoted huOKT3gamma1, huOKT3gamma4, huOKT3gamma1(A(234), A(235)), huOKT3gamma4(A(234), A(235)), and huOKT3gamma1(A(318)), has demonstrated that huOKT3gamma1(A(234), A(235)) and huOKT3gamma4(A(234), A(235)), and have at least a 100-fold reduced binding to FcgammaRI and FcgammaRII. As expected, they are much less potent in the induction of T cell activation and cytokine release, yet retain in vitro immunosuppressive effects as potent as those of mOKT3. Unexpectedly, while huOKT3gamma1(A(318)) did not show any reduction in its ability to bind C1q and to fix a complement, huOKT3gamma1(A(234), A(235)) was completely inactive. The in vitro characteristics of huOKT3gamma1(A(234), A(235)) are consistent with recent in vivo studies, in which this Ab showed greatly reduced HAMA and CRS with the retention of its ability to reverse ongoing graft rejection in man.

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.

Expansion and fibronectin-enhanced retroviral transduction of primary human T lymphocytes for adoptive immunotherapy

Human lymphocytes remain among the most promising target cells for gene therapy. Gene-modified lymphocytes have been used successfully to treat adenosine deaminase (ADA)-deficient patients and to control GvHD after allogeneic BMT. Because activation and proliferation of T cells are necessary for efficient retrovirus-mediated gene transfer and subsequent selection of transduced cells, mononuclear cells (MNC) from steady-state and G-CSF-stimulated peripheral blood were activated by short exposure to the mitogen PHA, the anti-CD3 antibody OKT3, or both in the presence of different concentrations of recombinant IL-2. Using OKT3 (10 or 30 ng/ml) and IL-2 (100 U/ml), T cells expanded efficiently during a 14-day culture period. Cell expansion was similar under serum-free conditions. The immunophenotypic profile over time showed a marked increase in CD8+ cells, leading to a reversed CD4/CD8 ratio of 1:2 and a slight increase in CD56+ cells. Supernatant-based centrifugal transduction of primary human T lymphocytes was compared with supernatant transduction on the extracellular matrix protein fibronectin. Transduction with cell-free retrovirus-containing supernatant in tissue culture flasks coated with human plasma fibronectin led to significantly higher transduction efficiencies (20% +/- 7.5%) than centrifugal transduction in uncoated culture flasks (13.6% +/- 5.1%)(p = 0.041). To both rapidly characterize transduced cells and isolate these from residual nontransduced but biologically equivalent cells, an amphotropic Moloney murine leukemia virus (MoMuLV)-based retroviral vector containing the intracytoplasmically truncated human low-affinity nerve growth factor receptor (deltaLNGFR) cDNA as a marker gene was used. FACS sorting of T cells after transduction resulted in >90% LNGFR+ cells and was much faster than enrichment of transduced cells through growth in G418-selection medium. These results show that supernatant-based retroviral gene transfer into primary human T lymphocytes can be enhanced by fibronectin. Ectopic expression of a cell surface protein can be used to rapidly and conveniently quantitate transduction efficiency through FACS analysis and to efficiently enrich transduced cells through FACS sorting.

Augmentation of antigen receptor-mediated responses by histamine H1 receptor signaling

Histamine is considered one of the important mediators of immediate hypersensitivity and inflammation, and acts via G protein-coupled receptors. Here, we report that histamine may affect antigen receptor-mediated immune responses of T and B cells via a signal(s) from histamine H1 receptors (H1Rs). Histamine exhibited enhancing effects on the in vitro proliferative responses of anti-CD3epsilon- or anti-IgM-stimulated spleen T and B cells, respectively, at the culture condition that the fetal calf serum was dialyzed before culture and c-kit-positive cells were depleted from the spleen cells. In studies of histamine H1R knockout mice, H1R-deficient T cells had low proliferative responses to anti-CD3epsilon cross-linking or antigen stimulation in vitro. B cells from H1R-deficient mice were also affected, demonstrating low proliferative responses to B cell receptor cross-linking. Antibody production against trinitrophenyl-Ficoll was reduced in H1R-deficient mice. Other aspects of T and B cell function were normal in the H1R knockout mice. H1R-deficient T and B cells showed normal responses upon stimulation with interleukin (IL)-2, IL-4, CD40 ligand, CD40 ligand plus IL-4, and lipopolysaccharide. Collectively, these results imply that the signal generated by histamine through H1R augments antigen receptor-mediated immune responses, suggesting cross-talk between G protein-coupled receptors and antigen receptor-mediated signaling.

Interferon-gamma production by T lymphocytes from renal cell carcinoma patients: evidence of impaired secretion in response to interleukin-12

Interleukin-12 (IL-12) is a heterodimeric cytokine that enhances the cytolytic activity, proliferation, and interferon-gamma (IFN-gamma) production by T lymphocytes and natural killer cells, and has significant antitumor activity in a variety of murine tumor models. The induction of interferon (IFN)-gamma by IL-12 in tumor-bearing mice plays an important role in its antitumor activity. We therefore examined the effects of IL-12 on IFN-gamma production by T cells derived from patients with renal cell carcinoma (RCC), including freshly isolated tumor infiltrating lymphocytes (T-TIL), matched peripheral blood T cells (T-PBL), and RCC-specific TIL lines. IL-12 alone induced IFN-gamma secretion by T cells from normal individuals and appeared to act synergistically with either IL-2 or anti-CD3 antibody. In contrast, it failed to stimulate significant IFN-gamma secretion by T-PBL and T-TIL from RCC patients. This unresponsive state in T-PBL appeared selective because IFN-gamma was produced when cells were stimulated with either phytohemagglutinin or anti-CD3 antibody. Moreover, costimulation through the T-cell receptor (TCR)/CD3 complex or with IL-2 made T-PBL from RCC patients responsive to IL-12, possibly secondary to the upregulation of IL-12R (beta chain). A selective loss of IL-12-dependent production of IFN-gamma was also consistently observed in two of three established RCC-specific TIL lines. Although these cell lines did not respond to any concentration of IL-12, they did produce IFN-gamma after ligation of the TCR/CD3 or stimulation with IL-2, IL-12 also acted either syngeristically or additively with IL-2, anti-CD3 antibody, or autologous tumor cells to induce IFN-gamma production. The observed decreases in IFN-gamma production in response to IL-12 may have a negative effect on the development of T-cell immunity. The clinical importance of these findings during in vivo administration of IL-12 remains to be determined.

Antibody-mediated thrombosis: relation to the antiphospholipid syndrome

Various forms of antibody-mediated thrombosis are presented and the mechanisms involved in their pathogenesis are discussed. Antibody-mediated thrombosis includes heparin-induced thrombocytopenia and thrombosis, autoantibodies to von Willebrand factor mimicking an antiphospholipid syndrome, thrombosis following injection of the murine monoclonal antibody OKT3, hyperacute and acute xenograft rejection, and varicella-associated antibody against protein S. In several of these entities the pathogenesis of thrombosis is closely related to development of cellular procoagulant activity through tight occupancy of Fc receptors, or through complement activation, or through cell-cell interactions. Integrating the antiphospholipid syndrome into the more general category of antibody-mediated thrombosis may provide some hints as to how we could approach the study of those intriguing patients who have the clinical features of the antiphospholipid syndrome but lack those antibodies that currently characterize it.

Epithelial ion transport and barrier abnormalities evoked by superantigen-activated immune cells are inhibited by interleukin-10 but not interleukin-4

Many studies have indicated an association between bacteria and the severity of enteric secretory or inflammatory disorders. We previously showed that monolayers of human T84 epithelial cells display altered ion transport and permeability after coculture with Staphylococcus aureus enterotoxin B (SEB, a model superantigen)-activated immune cells, where interferon-gamma and tumor necrosis factor-alpha were key mediators in the pathophysiology. Here we examined whether the regulatory Th2-type cytokines, interleukin (IL)-10 and IL-4, could prevent these epithelial irregularities. T84 monolayers were cocultured with human peripheral blood mononuclear cells (PBMC) or T cell-enriched, monocyte-depleted PBMC (T + B cells) +/- SEB for 20 hr in the presence or absence of IL-10 or IL-4. Subsequently, T84 monolayers were mounted in Ussing chambers and ion transport (short-circuit current (Isc) and DeltaIsc evoked by forskolin) and permeability (ion resistance and probe fluxes) were assessed. IL-10 dose-dependently inhibited the increased T84 permeability and the reduced responsiveness to forskolin that were evoked by coculture with SEB-activated PBMC or T + B cells. Similar changes in T84 function occurred in response to conditioned medium from SEB-activated immune cells; however, addition of IL-10 to the conditioned medium did not prevent the changes in epithelial function. In contrast, when PBMC were stimulated with SEB in the presence of IL-10, the subsequent conditioned medium was less effective in evoking altered epithelial function. These data suggest that the affect of IL-10 was due to effects on the immune cells and not directly on the epithelium. In contrast to IL-10, IL-4 did not ameliorate any of the immune-mediated changes in T84 function. We conclude that IL-10 can reduce the epithelial functional changes caused by SEB-activated immune cells and this data adds further support for IL-10 immunotherapy in the treatment of intestinal secretory or inflammatory disorders.

Mycophenolate mofetil, together with cyclosporin A, prevents anti-OKT3 antibody response in kidney transplant recipients

OKT3 monoclonal antibody, a murine IgG2a monoclonal antibody targeting the T cell CD3 antigen, elicits a neutralizing humoral response in 20 to 50% of kidney transplant recipients when the concomitant immunosuppression consists of CsA-Sandimmun (SAND) and azathioprine (AZA). In the present study, we investigated the impact of the newer agents, CsA-Neoral (NEO) and mycophenolate mofetil (MMF) on OKT3 sensitization. Sixty-two consecutive kidney transplant recipients received prophylactic OKT3 (5 mg/d) from days 0 to 13, together with steroids. Concomitant immunosuppression consisted of either AZA + SAND (n=20), AZA + NEO (n=31), or MMF + NEO (n=11). The following doses were used: AZA, 2 mg/kg per d from days 0 to 13, then 1 mg/kg per d; MMF, 2 g/d starting on day 1; and CsA, either SAND or NEO, 6 mg/kg per d from day 6. At least two serum samples per month were available during the initial 3 mo for each patient. IgG anti-OKT3 antibodies were first evaluated by enzyme-linked immunosorbent assay. Patients were considered sensitized if their serum scored positive at a dilution > or = 1/1000. Peak titers of IgG anti-OKT3 antibodies and the incidence of patients harboring neutralizing anti-idiotypic antibodies were also determined. A first reduction in OKT3 sensitization was seen in patients receiving Neoral instead of Sandimmun (AZA + SAND: 10 of 20 [50%] patients sensitized versus 6 of 31 [19%] in the AZA + NEO group; P=0.03). This was probably related to the achievement of higher mean CsA trough blood levels in the NEO group during the first month (253+/-44 versus 186+/-49 ng/ml in SAND patients). Peak antibody titers and the proportion of patients with anti-idiotypic antibodies were similar in the AZA + SAND and AZA + NEO groups. A further reduction in the sensitization rate was observed with the replacement of AZA by MMF (MMF + NEO: 0% sensitized patients; P=0.0013). It is concluded that the combination of CsA-Neoral and MMF efficiently prevents sensitization against OKT3.