Combination anti-CD2 and anti-CD3 monoclonal antibodies induce tolerance while altering interleukin-2, interleukin-4, tumor necrosis factor, and transforming growth factor-beta production

Targeting memory T cells in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease that leads to progressive destruction of pancreatic beta cells. Compared to healthy controls, a characteristic feature of patients with T1D is the presence of self-reactive T cells with a memory phenotype. These autoreactive memory T cells in both the CD4(+) and CD8(+) compartments are likely to be long-lived, strongly responsive to antigenic stimulation with less dependence on costimulation for activation and clonal expansion, and comparatively resistant to suppression by regulatory T cells (Tregs) or downregulation by immune-modulating agents. Persistence of autoreactive memory T cells likely contributes to the difficulty in preventing disease progression in new-onset T1D and maintaining allogeneic islet transplants by regular immunosuppressive regimens. The majority of immune interventions that have demonstrated some success in preserving beta cell function in the new-onset period have been shown to deplete or modulate memory T cells. Based on these and other considerations, preservation of residual beta cells early after diagnosis or restoration of beta cell mass by use of stem cell or transplantation technology will require a successful strategy to control the autoreactive memory T cell compartment, which could include depletion, inhibition of homeostatic cytokines, induction of hyporesponsiveness, or a combination of these approaches.

Induction of transplantation tolerance in non-human primate preclinical models

Short-term outcomes following organ transplantation have improved considerably since the availability of cyclosporine ushered in the modern era of immunosuppression. In spite of this, many of the current limitations to progress in the field are directly related to the existing practice of relatively non-specific immunosuppression. These include increased risks of opportunistic infection and cancer, and toxicity associated with long-term immunosuppressive drug exposure. In addition, long-term graft loss continues to result in part from a failure to adequately control the anti-donor immune response. The development of a safe and reliable means of inducing tolerance would ameliorate these issues and improve the lives of transplant recipients, yet given the improving clinical standard of care, the translation of new therapies has become appropriately more cautious and dependent on increasingly predictive preclinical models. While convenient and easy to use, rodent tolerance models have not to date been reliably capable of predicting a therapy's potential efficacy in humans. Non-human primates possess an immune system that more closely approximates that found in humans, and have served as a more rigorous preclinical testing ground for novel therapies. Prior to clinical adaptation therefore, tolerance regimens should be vetted in non-human primates to ensure that there is sufficient potential for efficacy to justify the risk of its application.

Alpha CD 2 mAb treatment safely attenuates adoptive transfer colitis

Increased proliferation, defective apoptosis, and cytokine dysregulation of T lymphocytes are thought to be important for the pathogenesis of inflammatory bowel disease. Since these phenomena can be corrected by alpha CD 2 mAb, we asked whether CD2 directed immunotherapy safely prevents and/or ameliorates adoptive transfer colitis. Colitis was induced by transfer of CD4(+) T cell blasts to syngenic RAG 1(-/-) mice or CD 45 RB(high) CD4(+) T cells to SCID mice. The alpha CD 2 mAb 12-15 or rat IgG was given, starting either initially or upon first signs of colitis. Disease activity was assessed by clinical monitoring, microscopic scoring, hemoccult, endoscopy, and blood count analysis. Cytokine production of stimulated LPL was measured by ELISA and cell proliferation by [(3)H]-thymidine incorporation. Parasite control was analyzed in a murine model of infection with Toxoplasma gondii. The alpha CD 2 mAb significantly increased mean survival time when starting at transfer of blasts (survival >35 days: alpha CD 2 69% vs 0% of controls, P<0.001). In the SCID colitis model hematochezia and macroscopic colitis were delayed. When used in established T-cell blast colitis, the benefit was less pronounced, even in combination with dexamethasone (mean survival+/-s.e.m.: alpha CD 2+dexa: 13.5+/-2.9 vs dexa+IgG: 6.3+/-1.0, P<0.05). In the preventive experiment the alpha CD 2 mAb markedly reduced IL-2 secretion and T-cell proliferation. The immune response towards Toxoplasma gondii was not impaired. These studies show for the first time that CD2 directed immunotherapy can attenuate or delay adoptive transfer colitis and ameliorate established colitis. Most likely inhibition of IL-2 secretion and T-cell proliferation are responsible for these effects. Still, immune defence towards T. gondii is maintained.

CD2 and CD3 receptor-mediated tolerance: constraints on T cell activation

BACKGROUND

Antigen specific allograft tolerance is induced in mice by anti-CD2 plus anti-CD3epsilon monoclonal antibody (mAb) treatment. Because anti-CD2 mAb inhibits several aspects of anti-CD3epsilon driven T cell activation, we investigated what components of T cell activation are required or may be dispensed with for tolerance induction. Anti-CD3epsilon-mediated T cell activation depends on FcgammaR interactions.

METHODS

To assess the role of FcgammaR-mediated T cell activation in tolerance induction, FcgammaR binding IgG or non-binding IgG3 anti-CD3epsilon mAbs were examined.

RESULTS

These mAbs, administered in conjunction with anti-CD2, were equally effective in inducing tolerance. Moreover, in vivo administration of a blocking mAb directed against the FcgammaR, or the use of allograft recipients deficient in FcgammaR, had no effect on tolerance induction. Blocking IL-2 using mAb directed against IL-2 or IL-2R also did not prevent the induction of tolerance. These results suggest that complete T cell activation was not required for tolerance induction. However, substitution of a partially activating mAb, directed against the T cell receptor (TCR) beta subunit for anti-CD3epsilon, failed to synergize with anti-CD2 mAb to induce tolerance. The anti-TCRbeta mAb and anti-CD3epsilon mAb were found to differentially down modulate expression of TCR/CD3 complex subunits. In particular, anti-CD3epsilon caused transient down modulation of the TCRbeta receptor subunit and the TCRzeta signaling module, and this pattern was enhanced and prolonged by anti-CD2. Anti-TCRbeta caused persistent TCRzeta modulation but no TCRbeta modulation, and anti-CD2 did not influence this pattern.

CONCLUSIONS

These results suggest that, although full T cell activation is not required for the induction of tolerance by anti-CD2 plus anti-CD3epsilon mAb, a signal transduction pathway that is associated with TCRbeta and TCRzeta expression, and, specifically, is perturbed by mAb binding of the CD3epsilon epitope, is critical.

Tolerance Induction by Anti-CD2 Plus Anti-CD3 Monoclonal Antibodies: Evidence for an IL-4 Requirement

Anti-CD2 mAb plus anti-CD3 mAb induce alloantigen specific tolerance. We sought to determine whether Th2 cytokines are involved in the induction of tolerance in this model. Addition of anti-IL-4 mAb or anti-IL-10 mAb to anti-CD2 plus anti-CD3 treatment abrogated tolerance and resulted in graft survivals of 26 ± 4 and 25 ± 5 days, respectively. Splenocytes from the anti-IL-4 mAb and anti-IL-10 groups had greater proliferation in response to alloantigen than either tolerant or naive groups. Cytokine analysis of MLR supernatants showed increased IL-10 in the tolerant group and increased IFN-γ in the anti-IL-4 mAb treated group. Donor-specific alloantibody responses in untreated immune animals had a predominantly Th1 (IgG2a) alloantibody response, while the tolerogenic regimen reduced the ratio of IgG2a:IgG1 titers. The addition of anti-IL-4 mAb to the tolerogenic regimen partly restored the Th1-related IgG2a response. Tolerance did not develop in IL-4 knockout animals treated with anti-CD2 plus anti-CD3 (mean graft survival, 27 ± 5 days). Restoration of IL-4 to IL-4 knockout animals by gene transfer with plasmid DNA resulted in prolongation of survival to 46 ± 7 days, while adoptive transfer of wild-type splenocytes into IL-4 knockout recipients resulted in indefinite graft survival (&gt;60 days) and indefinite survival of second donor-type grafts. IL-10 gene transfer to IL-4 knockout recipients did not prolong graft survival (28 ± 4). These results demonstrate that tolerance in this model is mediated at least in part by Th2-type cells that secrete IL-4, promote IL-10 and IgG1 production, and inhibit alloantigen reactivity.

Anti-transferrin receptor monoclonal antibody: a novel immunosuppressant

BACKGROUND

Transferrin receptor is a widely distributed cell surface receptor present on most proliferating and highly specialized quiescent cells. Expression of transferrin receptor on the surface of immune cells is up-regulated during T-cell activation after the interaction of the antigen-MHC with the T cell receptor. The role of transferrin receptor in T-cell activation has not been well-established. Since transferrin receptor is physically associated with the CD3 zeta-chain, blockade of transferrin receptor has the potential to interfere with the T-cell signals important in transplant rejection.

METHODS

Anti-transferrin receptor monoclonal antibody (mAb) was administered in vivo and in vitro to determine whether this agent was effective in prolonging allograft survival and altering cell-mediated immunity.

RESULTS

Using donor C57BL/6J (H2b) hearts transplanted to CBA/J (H2k) recipients, anti-transferrin receptor mAb at the time of transplantation prolonged cardiac allograft mean survival time to 25.7+/-0.9 days compared with untreated (13.3+/-0.6 days, P < 0.05) or isotype-matched (10.7+/-0.4 days, P < 0.05) controls. Anti-transferrin receptor mAb administered in vivo failed to suppress the subsequent allogeneic responses. However, when added to culture, anti-transferrin receptor mAb suppressed the allogeneic cytotoxic T lymphocyte response by 79-100% but not the mixed lymphocyte response.

CONCLUSIONS

These studies are the first to suggest that transferrin receptor is a potential therapeutic target for clinical transplantation. Future studies will determine the most efficacious dose and time for maximal immunosuppression and the mechanisms responsible for the immunosuppression exhibited by antitransferrin receptor mAb.

Down-modulation of CD2 delays deletion of superantigen-responsive T cells

CD2 is a cell surface glycoprotein expressed on most T lymphocytes that is generally viewed as a cell adhesion molecule and, in this capacity, contributes to T cell receptor (TCR) signaling. CD2 has a relatively long cytoplasmic tail which associates with the src family tyrosine kinases, p56(lck) and p59(fyn), and could potentially signal directly. Down-modulation of CD2 on T cells has been shown to result in diminished proliferative capacity and interleukin (IL)-2 production. Furthermore, re-expression of CD2 can result in the restoration of these functions. This suggests that CD2 can influence the intensity of TCR signaling. As TCR signal intensity is pivotal to the induction of T cell apoptosis, we considered the hypothesis that the level of CD2 on the T cell surface may influence its propensity toward apoptosis. Using an anti-CD2 antibody, CD2 was down-modulated in vivo on mouse T lymphocytes without affecting the levels of surface CD3, TCR alphabeta, CD4 or CD8. Deletion of superantigen-responsive T cells was delayed in mice with down-modulated CD2 following the administration of staphylococcal enterotoxin B (SEB). This was paralleled by diminished apoptosis of SEB-responsive cells. The findings suggest a model whereby the level of CD2 expression influences the intensity of TCR signaling and the ability to undergo apoptosis.

A dimeric form of soluble recombinant sheep LFA-3(CD58) inhibits human T-cell proliferation by generating regulatory T cells

We recently observed that the soluble recombinant from of sheep LFA-3, termed sLFA-3 is biologically active as determined by E-rosette inhibition and inhibition of human T-cell proliferation in response to the recall antigen. In the present study, we examined the immunosuppressive properties of a derivative of sLFA-3, a dimeric form of the first domain (D1) of sLFA-3, named sD1Hcys dimer which was made by oxidative binding of the two D1 molecules through disulfide bonds formed between the SH side chains of a cysteine which was added to the C-terminal of the D1 domain. By investigating the suppressive properties of the sD1Hcys dimer, we obtained evidence that antigen-stimulated T-cell proliferation was inhibited by the suppressor T cell, mainly CD4 + CD45RA - CD45RO + and CD8 + CD45RA - CD45RO + T cells, generated by incubating PBLs with a low dose (0.5 microgram/ml) of sD1Hcys dimer in the presence of a low dose of IL-2 and GM-CSF. Flow cytometric analysis showed that the expression of some surface molecules on T cells were modulated by a high dose (5 micrograms/ml) of sD1Hcys dimer such as downregulation of CD3 and upregulation of IL-2R, but were not modulated by a low dose (0.5 microgram/ml) of the sD1Hcys dimer. These findings suggest that the sD1Hcys dimer exerts its suppressive effects on the antigen-induced proliferation assay by generating suppressor T cells. The sD1Hcys dimer might therefore have potential as an immunotherapeutic agent to inhibit and/or anergize antigen-specific T-cell responses.

CD2 Rescues T Cells From T-Cell Receptor/CD3 Apoptosis: A Role for the Fas/Fas-L System

Anti-CD3 monoclonal antibodies (MoAbs) and glucocorticoid hormones induce apoptosis in immature thymocytes and peripheral T lymphocytes. This process is inhibited by a number of growth factors, including interleukin-2 (IL-2), IL-3, and IL-4, as well as by triggering of the adhesion molecule CD44, which would indicate that signals generated by membrane receptors can modulate the survival of lymphoid cells. To investigate whether triggering of CD2 may also affect apoptosis in lymphoid cells, we analyzed the effect of stimu-lation with anti-CD2 MoAbs on T-cell apoptosis induced by two stimuli, anti-CD3 MoAbs and dexamethasone (DEX), using a hybridoma T-cell line and a T-helper cell clone. The results show that CD2 engagement decreased anti-CD3 MoAb-induced apoptosis, but did not influence DEX-induced cell death. Furthermore, the decrease appeared to be related to the expression of Fas/APO-1 (CD95) and Fas-ligand (Fas-L). In fact, we show that CD2 stimulation inhibits apoptosis by preventing the CD3-induced upregulation of Fas and Fas-L in a Fas-dependent experimental system. These data suggest that a costimulatory molecule may control a deletion pathway and may therefore contribute to the regulation of peripheral tolerance.

CD2 Rescues T Cells From T-Cell Receptor/CD3 Apoptosis: A Role for the Fas/Fas-L System

Anti-CD3 monoclonal antibodies (MoAbs) and glucocorticoid hormones induce apoptosis in immature thymocytes and peripheral T lymphocytes. This process is inhibited by a number of growth factors, including interleukin-2 (IL-2), IL-3, and IL-4, as well as by triggering of the adhesion molecule CD44, which would indicate that signals generated by membrane receptors can modulate the survival of lymphoid cells. To investigate whether triggering of CD2 may also affect apoptosis in lymphoid cells, we analyzed the effect of stimu-lation with anti-CD2 MoAbs on T-cell apoptosis induced by two stimuli, anti-CD3 MoAbs and dexamethasone (DEX), using a hybridoma T-cell line and a T-helper cell clone. The results show that CD2 engagement decreased anti-CD3 MoAb-induced apoptosis, but did not influence DEX-induced cell death. Furthermore, the decrease appeared to be related to the expression of Fas/APO-1 (CD95) and Fas-ligand (Fas-L). In fact, we show that CD2 stimulation inhibits apoptosis by preventing the CD3-induced upregulation of Fas and Fas-L in a Fas-dependent experimental system. These data suggest that a costimulatory molecule may control a deletion pathway and may therefore contribute to the regulation of peripheral tolerance.

Blockade of multiple costimulatory receptors induces hyporesponsiveness: inhibition of CD2 plus CD28 pathways

T-lymphocyte activation requires engagement of the T cell receptor with antigen-major histocompatibility complex, and simultaneous ligation of costimulatory pathways via the lymphocyte receptors CD2 and CD28/ CTLA4. Anti-CD2 monoclonal antibody (mAb) blocks the interaction of the antigen-presenting cell receptor CD48 with its ligand CD2, whereas CTLA4Ig binds with high affinity to the antigen-presenting cell ligands B7-1 and B7-2, blocking their interaction with CD28/CTLA4. We tested the immunosuppressive effects of simultaneously blocking both costimulatory pathways. Using donor C57BL/6J (H2b) hearts transplanted to CBA/J (H2k) recipients, anti-CD2 mAb plus CTLA4Ig administered at the time of transplantation prolonged cardiac allograft mean survival time to >120 days compared with untreated controls (12.2+/-0.5 days, P<0.01), anti-CD2 mAb alone (24.8+/-1.0 days, P<0.01), or CTLA4Ig alone (55.0+/-2.0 days, P<0.01). Retransplantation of these recipients with donor-specific and third-party grafts demonstrated that hyporesponsiveness and tolerance were achieved. In vitro stimulation of lymphocytes from tolerant recipients with donor-specific alloantigen resulted in normal cytotoxic T lymphocyte and mixed lymphocyte reaction responses, showing that clonal deletion or anergy did not occur, but that graft adaptation or suppression likely helped to maintain long-term graft survival. In vitro combinations of anti-CD2 mAb and CTLA4Ig suppressed the generation of allogeneic cytotoxic T lymphocytes (58%) and the mixed lymphocyte reaction (36%); CTLA4Ig was more effective in this regard and the two agents were not synergistic. Anti-CD2 mAb and CTLA4Ig suppressed mitogen-driven proliferation in differential fashions, suggesting that they affected independent signaling pathways. Anti-CD2 mAb and CTLA4Ig also inhibited interleukin (IL)-2, IL-4, and IL-2 receptor (CD25). These data indicate that anti-CD2 mAb plus CTLA4Ig induces hyporesponsiveness and tolerance. The mechanism is likely related to the initial disruption of independent pathways of T-lymphocyte activation leading to antigen-specific long-term graft survival.

Gene transfer for transplantation. Prolongation of allograft survival with transforming growth factor-beta 1

OBJECTIVE

The authors tested the ability of plasmid gene transfer to express transforming growth factor-beta 1 (TGF-beta 1), prolong allograft survival, and evaluate promoter effects on gene expression.

SUMMARY BACKGROUND DATA

Delivery of immunosuppressants directly to allografts using gene transfer and gene therapy approaches may inhibit immune activation while avoiding the systemic toxicity of conventional immunosuppression. Candidate genes include soluble cytokines, which could be expressed at low levels throughout the graft while inducing a local immunosuppressive effect. Transforming growth factor-beta 1 is a soluble cytokine that has pleiotropic immunosuppressive effects.

METHODS

Cardiac grafts from syngeneic (CBA/J, H-2k) or allogenic (C57BL/6, H-2b) donors were placed into CBA/J recipients. Purified plasmid DNA-encoding murine TGF-beta 1 or beta-galactosidase (Lac Z) under the control of RSV, SV40, MMTV, or pancreatic elastase promoters was injected into grafts at surgery. The Lac Z expression was determined by histologic examination and TGF-beta 1 expression by graft survival. Cytotoxic T lymphocyte and flow cytometric analyses were performed to evaluate the immunosuppressive effects of TGF-beta 1 in vitro.

RESULTS

Plasmid DNA-encoding TGF-beta 1 prolonged survival from 12.6 +/- 1.1 days to 26.3 +/- 2.5 days (p < 0.02, Student's t test). The SV40 promoter was superior to the MMTV promoter in its ability to prolong survival. The effects of the plasmids were specific because Lac Z, antisense TGF-beta 1 inserts, or pancreatic elastase promoter did not prolong allograft survival. Histologic examination demonstrated Lac Z expression at least 14 days post-transplant in myocardial cells. Both RSV and SV40 promoters were effective in this respect, while a control null promoter was not. Toxicity testing showed that gene transfer of TGF-beta 1 did not alter survival or histology of syngeneic grafts. In addition, plasmids and purified TGF-beta 1 protein were not toxic to myoblasts in vitro. Recombinant TGF-beta 1 inhibited cytotoxic T lymphocyte generation and altered T cell surface receptor expression and subset expansion in vitro.

CONCLUSION

Gene transfer/therapy with plasmid DNA encoding TGF-beta 1 in vivo achieves immunologic effects that prolong allograft survival. Multiple promoters effectively induce plasmid expression, which is achieved in cardiac myocytes for at least 2 weeks without toxicity or adverse systemic effects. Transforming growth factor-beta 1 inhibits immune responses by different mechanisms, revealed by in vitro analysis of T cell cytolytic function, subset distribution, and receptor display.