Daily subcutaneous injections of peptide induce CD4+ CD25+ T regulatory cells

Continuous Antigenic Stimulation of DO11.10 TCR Transgenic Mice in the Presence or Absence of IL-1β: Possible Implications for Mechanisms of T Cell Depletion in HIV Disease

Untreated HIV disease is associated with chronic immune activation and CD4(+) T cell depletion. A variety of mechanisms have been invoked to account for CD4(+) T cell depletion in this setting, but the quantitative contributions of these proposed mechanisms over time remain unclear. We turned to the DO11.10 TCR transgenic mouse model, where OVA is recognized in the context of H-2(d), to explore the impact of chronic antigenic stimulation on CD4(+) T cell dynamics. To model dichotomous states of persistent Ag exposure in the presence or absence of proinflammatory stimulation, we administered OVA peptide to these mice on a continuous basis with or without the prototypic proinflammatory cytokine, IL-1β. In both cases, circulating Ag-specific CD4(+) T cells were depleted. However, in the absence of IL-1β, there was limited proliferation and effector/memory conversion of Ag-specific T cells, depletion of peripheral CD4(+) T cells in hematolymphoid organs, and systemic induction of regulatory Foxp3(+)CD4(+) T cells, as often observed in late-stage HIV disease. By contrast, when OVA peptide was administered in the presence of IL-1β, effector/memory phenotype T cells expanded and the typical symptoms of heightened immune activation were observed. Acknowledging the imperfect and incomplete relationship between Ag-stimulated DO11.10 TCR transgenic mice and HIV-infected humans, our data suggest that CD4(+) T cell depletion in the setting of HIV disease may reflect, at least in part, chronic Ag exposure in the absence of proinflammatory signals and/or appropriate APC functions.

Immunosuppressive drugs on inducing Ag-specific CD4(+)CD25(+)Foxp3(+) Treg cells during immune response in vivo

A variety of immunosuppressive drugs are currently used in patients with allo-grafts or autoimmune diseases. Though the effects of rapamycin (RPM) and other immunosuppressant on the CD4(+)CD25(+)Foxp3(+) T regulatory cells (Tregs) were studied, their impact on Ag-specific Tregs during immune response was not well defined. In our studies, we adoptively transferred TCR-transgenic CD4(+)KJ1-26(+) T cells, CD4(+)KJ1-26(+)CD25(-) naïve T cells or CD4(+)KJ1-26(+)CD25(+) Tregs into syngeneic BALB/c mice. 24h later, we treated the recipients with OVA immunization and immunosuppressant including rapamycin (RPM), fingolimod (FTY720), cyclosporin A (CsA), mycophenolate mofetil (MMF), leflunomide (LEF), cyclophosphamide (Cy) or none, respectively. The levels and function of CD4(+)KJ1-26(+)CD25(+)Foxp3(+) Tregs in draining lymph nodes (dLNs) and spleens were determined at different time points. Significantly higher percentage and cell number of Ag-specific CD4(+)KJ1-26(+)CD25(+)Foxp3(+) Tregs were observed in OVA immunized mice treated with RPM or FTY720 compared with mice that received OVA immunization alone. Furthermore, RPM augmented the population of functional iTregs in dLNs and spleens whereas inhibited nTregs during immune response. In contrast to RPM and FTY720, MMF, LEF, CsA, and Cy markedly decreased the levels of Ag-specific CD4(+)KJ1-26(+)CD25(+)Foxp3(+) Tregs during immune response. Thus, different immunosuppressive drugs have distinct effects on the Ag-specific CD4(+)CD25(+)Foxp3(+) Tregs during immune response. The stronger inhibiting effects of MMF, LEF, CsA and Cy on CD4(+)CD25(+)Foxp3(+) Tregs than on T effectors may block the host immune tolerance potentiality.

Role of regulatory T-cells in immunization strategies involving a recombinant alphavirus vector system

BACKGROUND

Regulatory T-cells (Treg) hamper immune responses elicited by cancer vaccines. Therefore, depletion of Treg is being used to improve the outcome of vaccinations.

METHODS

We studied whether an alphavirus vector-based immunotherapeutic vaccine changes the number and/or activity of Treg and if Treg depletion improves the efficacy of this vaccine against tumours. The vaccine is based on a Semliki Forest virus (SFV). The recombinant SFV replicon particles encode a fusion protein of E6 and E7 from human papillomavirus (HPV) type 16 (SFVeE6,7).

RESULTS

We demonstrated that SFVeE6,7 immunization did not change Treg levels and their suppressive activity. Depletion of Treg in mice, using the novel anti-folate receptor 4 antibody, did not enhance the immune response induced by SFVeE6,7 immunization. Both the priming and the proliferation phases of the HPV-specific response elicited with SFVeE6,7 were not affected by the immune-suppressive activity of Treg. Moreover, Treg depletion did not improve the therapeutic antitumour response of SFVeE6,7 in a murine tumour model.

CONCLUSIONS

The efficacy of the SFVeE6,7 vaccine was not hampered by Treg. Therefore, SFVeE6,7 seems a very promising candidate for the treatment of HPV-induced disease, as it may not require additional immune interventions to modulate Treg activity.

Gene related to anergy in lymphocytes (GRAIL) expression in CD4+ T cells impairs actin cytoskeletal organization during T cell/antigen-presenting cell interactions

GRAIL (gene related to anergy in lymphocytes), is an E3 ubiquitin ligase with increased expression in anergic CD4+ T cells. The expression of GRAIL has been shown to be both necessary and sufficient for the induction of T cell (T) anergy. To date, several subsets of anergic T cells have demonstrated altered interactions with antigen-presenting cells (APC) and perturbed TCR-mediated signaling. The role of GRAIL in mediating these aspects of T cell anergy remains unclear. We used flow cytometry and confocal microscopy to examine T/APC interactions in GRAIL-expressing T cells. Increased GRAIL expression resulted in reduced T/APC conjugation efficiency as assessed by flow cytometry. Examination of single T/APC conjugates by confocal microscopy revealed altered polarization of polymerized actin and LFA-1 to the T/APC interface. When GRAIL expression was knocked down, actin polarization to the T/APC interface was restored, demonstrating that GRAIL is necessary for alteration of actin cytoskeletal rearrangement under anergizing conditions. Interestingly, proximal TCR signaling including calcium flux and phosphorylation of Vav were not disrupted by expression of GRAIL in CD4+ T cells. In contrast, interrogation of distal signaling events demonstrated significantly decreased JNK phosphorylation in GRAIL-expressing T cells. In sum, GRAIL expression in CD4+ T cells mediates alterations in the actin cytoskeleton during T/APC interactions. Moreover, in this model, our data dissociates proximal T cell signaling events from functional unresponsiveness. These data demonstrate a novel role for GRAIL in modulating T/APC interactions and provide further insight into the cell biology of anergic T cells.

Recurrent superantigen exposure in vivo leads to highly suppressive CD4+CD25+ and CD4+CD25- T cells with anergic and suppressive genetic signatures

Staphylococcal enterotoxin B (SEB) activates T cells via non-canonical signalling through the T cell receptor and is an established model for T cell unresponsiveness in vivo. In this study, we sought to characterize the suppressive qualities of SEB-exposed CD4(+) T cells and correlate this with genetic signatures of anergy and suppression. SEB-exposed CD25(+) and CD25(-)Vbeta8(+)CD4(+) T cells expressed forkhead box P3 (FoxP3) at levels comparable to naive CD25(+) T regulatory cells and were enriched after exposure in vivo. Gene related to anergy in lymphocytes (GRAIL), an anergy-related E3 ubiquitin ligase, was up-regulated in the SEB-exposed CD25(+) and CD25(-)FoxP3(+)Vbeta8(+)CD4(+) T cells and FoxP3(-)CD25(-)Vbeta8(+)CD4(+) T cells, suggesting that GRAIL may be important for dominant and recessive tolerance. The SEB-exposed FoxP3(+)GRAIL(+) T cells were highly suppressive and non-proliferative independent of CD25 expression level and via a glucocorticoid-induced tumour necrosis factor R-related protein-independent mechanism, whereas naive T regulatory cells were non-suppressive and partially proliferative with SEB activation in vitro. Lastly, adoptive transfer of conventional T cells revealed that induction of FoxP3(+) regulatory cells is not operational in this model system. These data provide a novel paradigm for chronic non-canonical T cell receptor engagement leading to highly suppressive FoxP3(+)GRAIL(+)CD4(+) T cells.