Treatment-enhanced CD4+Foxp3+ glucocorticoid-induced TNF receptor family related high regulatory tumor-infiltrating T cells limit the effectiveness of cytokine-based immunotherapy

IL-12 and IL-4 activate a CD39-dependent intrinsic peripheral tolerance mechanism in CD8(+) T cells

Immune responses to protein antigens involve CD4(+) and CD8(+) T cells, which follow distinct programs of differentiation. Naïve CD8 T cells rapidly develop cytotoxic T-cell (CTL) activity after T-cell receptor stimulation, and we have previously shown that this is accompanied by suppressive activity in the presence of specific cytokines, i.e. IL-12 and IL-4. Cytokine-induced CD8(+) regulatory T (Treg) cells are one of several Treg-cell phenotypes and are Foxp3(-) IL-10(+) with contact-dependent suppressive capacity. Here, we show they also express high level CD39, an ecto-nucleotidase that degrades extracellular ATP, and this contributes to their suppressive activity. CD39 expression was found to be upregulated on CD8(+) T cells during peripheral tolerance induction in vivo, accompanied by release of IL-12 and IL-10. CD39 was also upregulated during respiratory tolerance induction to inhaled allergen and on tumor-infiltrating CD8(+) T cells. Production of IL-10 and expression of CD39 by CD8(+) T cells was independently regulated, being respectively blocked by extracellular ATP and enhanced by an A2A adenosine receptor agonist. Our results suggest that any CTL can develop suppressive activity when exposed to specific cytokines in the absence of alarmins. Thus negative feedback controls CTL expansion under regulation from both nucleotide and cytokine environment within tissues.

Partial CD4 depletion reduces regulatory T cells induced by multiple vaccinations and restores therapeutic efficacy

PURPOSE

A single vaccination of intact or reconstituted-lymphopenic mice (RLM) with a granulocyte macrophage colony-stimulating factor-secreting B16BL6-D5 melanoma cell line induces protective antitumor immunity and T cells that mediate the regression of established melanoma in adoptive immunotherapy studies. We wanted to study if multiple vaccinations during immune reconstitution of the lymphopenic host would maintain a potent antitumor immune response.

EXPERIMENTAL DESIGN

RLM were vaccinated multiple times over a 40-day period. Spleens were isolated from these mice, activated in vitro, and adoptively transferred into mice bearing 3-day experimental pulmonary metastases.

RESULTS

Multiple vaccinations, rather than boosting the immune response, significantly reduced therapeutic efficacy of adoptive immunotherapy and were associated with an increased frequency and absolute number of CD3+CD4+Foxp3+ T regulatory (T(reg)) cells. Anti-CD4 administration reduced the absolute number of T(reg) cells 9-fold. Effector T-cells generated from anti-CD4-treated mice were significantly (P < 0.0001) more therapeutic in adoptive transfer studies than T cells from multiply vaccinated animals with a full complement of CD4+ cells.

CONCLUSION

These results suggest that CD4+ T(reg) cells limit the efficacy of multiple vaccinations and that timed partial depletion of CD4+ T cells may reduce suppression and "tip-the-balance" in favor of therapeutic antitumor immunity. The recent failure of large phase III cancer vaccine clinical trials, wherein patients received multiple vaccines, underscores the potential clinical relevance of these findings.

Glucocorticoid treatment restores the impaired suppressive function of regulatory T cells in patients with relapsing-remitting multiple sclerosis

Patients relapsing from multiple sclerosis (MS) are treated with high-dose, short-term intravenous injection of glucocorticoid (GC), although its mechanism of action remains only partly understood. We evaluated the ex vivo and in vitro effects of GC on regulatory T cell (T(reg)) function in 14 relapsing-remitting MS (RR-MS) patients in acute phase and 20 healthy controls (HC). T(reg) function was enhanced significantly after 5 days of GC treatment. Furthermore, there was a trend towards increasing proportions of CD4(+)CD25(+)forkhead box P3(+) T cells and interleukin-10 secretion with GC treatment when compared with HC. In conclusion, GC treatment restores the impaired T(reg) function in patients with RR-MS in its acute phase.

Expression of ICOS on human melanoma-infiltrating CD4+CD25highFoxp3+ T regulatory cells: implications and impact on tumor-mediated immune suppression

OBJECTIVE

Interaction of ICOS with its ligand (ICOSL, B7-H2) promotes T cell responses. As CD4+CD25highFoxp3+ naturally occurring T regulatory cells in melanoma patients express ICOS, we investigated the impact of ICOS on naturally occurring T regulatory cell function.

METHODS

Expression of ICOS and T regulatory (Treg) cell markers was determined on CD4+CD25high T cells in PBMC and tumor-infiltrating lymphocytes from melanoma patients (n=10) and PBMC of normal controls (n=10) by multicolor flow cytometry. Suppression mediated by sorted ICOShigh and ICOSlow Treg was assessed in CFSE-based suppression assays with autologous CD4+CD25- responder cells (RC). Transwell inserts separating Treg from RC were used to evaluate suppression mechanisms used by Treg. ICOShigh or ICOSlow Treg were coincubated with RC+/-TCR and IL-2 stimulation. ICOShigh and ICOS- Treg were also expanded under conditions previously shown to induce Tr1 from RC.

RESULTS

Treg in tumor-infiltrating lymphocytes expressed ICOS (mean fluorescence intensity=70+/-10), while Treg in PBMC had low ICOS expression (mean fluorescence intensity=3.5+/-2.5, p<or=0.001). ICOShigh Treg up-regulated Treg markers (p<or=0.0016) and mediated stronger suppression (p<or=0.001) relative to ICOSlow Treg. ICOShigh Treg induced Tr1 cells in nonactivated RC and Th2 cells in preactivated RC. ICOShigh Treg exposed to Tr1 cytokines expressed IL-10 and suppressed RC (92+/-12%) in contrast to ICOSlow Treg, which mediated low suppression (21+/-15%; p<or=0.0028).

CONCLUSION

ICOShigh Treg can induce diverse immune responses in RC, depending on activation signals and cytokines present. ICOShigh Treg induce Tr1 or Th2 cells depending on the activation state of RC. In a "Tr1" cytokine milieu, ICOShigh Treg transit to Tr1.

Regulatory T cells and treatment of cancer

CD4+CD25+FOXP3+ regulatory T cells (Tregs) are elevated in cancers and can thwart protective antitumor immunity. Recent human cancer trials suggest that depleting Tregs can be clinically beneficial. Additional types of deleterious regulatory cells are also increased in cancer. Tregs also play unanticipated roles in cancer therapy in that some drugs unexpectedly increase (e.g. cancer vaccines or IL-2 treatment) or decrease (e.g. antineoangiogenesis agents or receptor tyrosine kinase inhibitors) their numbers or function. Managing deleterious effects of regulatory cells represents a novel and potentially effective way to give immunotherapy for cancer. New insights into molecular mechanisms governing trafficking, differentiation, and function of these cells suggest novel approaches to manipulating them as treatment strategies.

Induction of immunosuppressive molecules and regulatory T cells counteracts the antitumor effect of interleukin-12-based gene therapy in a transgenic mouse model of liver cancer

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) often lacks curative treatment; therefore new efficient therapies are needed. In this work we aimed at evaluating the antitumor effect of interleukin-12 (IL-12)-based gene therapy on HCC occurring spontaneously in mice.

METHODS

A plasmid-vector expressing IL-12 in a liver-specific and doxycycline (Dox)-inducible manner was transferred by hydrodynamic injection to the liver of L-PK/c-myc mice with HCC. IL-12 expression was induced by administering Dox (3 cycles of 1 month duration separated by 1 month rest).

RESULTS

Dox administration increased serum IL-12 and IFN-gamma and induced tumor lymphocytic infiltration in all treated mice which was accompanied by tumor stabilization or regression in 40% of animals. The antitumor effect did not correlate with levels of IL-12 or IFN-gamma nor with the intensity of tumor mononuclear infiltration. However, tumors from non-responder mice showed more abundance of Foxp3+ regulatory T cells and higher expression of the immunosuppressive molecules PD-1, PD-L1, VEGF, CTLA-4, IDO, and IL-10 than those that responded to therapy.

CONCLUSIONS

Although long-term induction of IL-12 expression in the liver can inhibit HCC growth, the efficacy of the treatment appears to be limited by the activation of immunosuppressive mechanisms.