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Blockade of CTLA-4 on both effector and regulatory T cell compartments contributes to the antitumor activity of anti-CTLA-4 antibodies.

Peggs KS, Quezada SA, Chambers CA, Korman AJ, Allison JP - J. Exp. Med. (2009)

Bottom Line: The data show that although blockade on effector cells significantly improves tumor protection, unicompartmental blockade on regulatory cells completely fails to enhance antitumor responses.However, concomitant blockade of both compartments leads to a synergistic effect and maximal antitumor activity.We conclude that the combination of direct enhancement of T(eff) cell function and concomitant inhibition of T reg cell activity through blockade of CTLA-4 on both cell types is essential for mediating the full therapeutic effects of anti-CTLA-4 antibodies during cancer immunotherapy.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Immunology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.

ABSTRACT
Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical negative regulator of immune responses. Uniquely among known inhibitory receptors, its genetic ablation results in a fulminating and fatal lymphoproliferative disorder. This central regulatory role led to the development of antibodies designed to block CTLA-4 activity in vivo, aiming to enhance immune responses against cancer. Despite their preclinical efficacy and promising clinical activity against late stage metastatic melanoma, the critical cellular targets for their activity remains unclear. In particular, debate has focused on whether the effector T cell (T(eff)) or regulatory T cell (T reg cell) compartment is the primary target of antibody-mediated blockade. We developed a mouse expressing human instead of mouse CTLA-4, allowing us to evaluate the independent contributions of CTLA-4 blockade of each T cell compartment during cancer immunotherapy in an in vivo model of mouse melanoma. The data show that although blockade on effector cells significantly improves tumor protection, unicompartmental blockade on regulatory cells completely fails to enhance antitumor responses. However, concomitant blockade of both compartments leads to a synergistic effect and maximal antitumor activity. We conclude that the combination of direct enhancement of T(eff) cell function and concomitant inhibition of T reg cell activity through blockade of CTLA-4 on both cell types is essential for mediating the full therapeutic effects of anti-CTLA-4 antibodies during cancer immunotherapy.

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Unicompartmental blockade with aMuCTLA-4 during in vitro suppressor assays suggests both cell autonomous and non–cell autonomous activities of CTLA-4. Suppressor assays were performed using mixtures of WT and HuTg cells. (a and b) Proliferation of 50,000 purified WT or HuTg CD4+CD25− and CD4+CD25+ T cells in response to T cell–depleted splenocytes and anti-CD3 and in the presence of control IgG or aMuCTLA-4, confirming the species specificity of the CTLA-4 blockade. (c) Unicompartmental blockade of 50,000 WT CD4+CD25− T cells with aMuCTLA-4, compared with control IgG during in vitro suppression by addition of increasing numbers of HuTg CD4+CD25+ T reg cells. (d) Unicompartmental blockade of WT CD4+CD25+ T reg cells with aMuCTLA-4, compared with control IgG during in vitro suppression of 50,000 HuTg CD4+CD25− T cells. (e) Bicompartmental blockade of both WT CD4+CD25− Teff and CD4+CD25+ T reg cells with aMuCTLA-4, compared with control IgG during in vitro suppressor assays. Data in a–e represent three or more independent experiments, and in each group replicates were performed as quintuplets. Error bars indicate SD.
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fig2: Unicompartmental blockade with aMuCTLA-4 during in vitro suppressor assays suggests both cell autonomous and non–cell autonomous activities of CTLA-4. Suppressor assays were performed using mixtures of WT and HuTg cells. (a and b) Proliferation of 50,000 purified WT or HuTg CD4+CD25− and CD4+CD25+ T cells in response to T cell–depleted splenocytes and anti-CD3 and in the presence of control IgG or aMuCTLA-4, confirming the species specificity of the CTLA-4 blockade. (c) Unicompartmental blockade of 50,000 WT CD4+CD25− T cells with aMuCTLA-4, compared with control IgG during in vitro suppression by addition of increasing numbers of HuTg CD4+CD25+ T reg cells. (d) Unicompartmental blockade of WT CD4+CD25+ T reg cells with aMuCTLA-4, compared with control IgG during in vitro suppression of 50,000 HuTg CD4+CD25− T cells. (e) Bicompartmental blockade of both WT CD4+CD25− Teff and CD4+CD25+ T reg cells with aMuCTLA-4, compared with control IgG during in vitro suppressor assays. Data in a–e represent three or more independent experiments, and in each group replicates were performed as quintuplets. Error bars indicate SD.

Mentions: In accordance with the species-specific binding of anti–CTLA-4 mAb (Fig. 1, a and b), functional blockade with an aMuCTLA-4 (clone 9H10) was also species specific (Fig. 2, a and b). Purified populations of either CD4+CD25− or CD4+CD25+ WT T cells proliferated to a significantly greater degree in the presence of aMuCTLA-4 than control IgG in thymidine incorporation assays (Fig. 2 a), whereas neither population of purified cells from HuTg mice showed enhanced proliferation in the presence of aMuCTLA-4 (Fig. 2 b). The direct effect on purified effector and regulatory WT cells highlights the cell autonomous role of CTLA-4 in inhibiting T cell proliferation. The demonstration that aMuCTLA-4 produces functional blockade in a species-specific manner allowed us to examine the effects of unicompartmental blockade of either the T reg or non–T reg cell populations.


Blockade of CTLA-4 on both effector and regulatory T cell compartments contributes to the antitumor activity of anti-CTLA-4 antibodies.

Peggs KS, Quezada SA, Chambers CA, Korman AJ, Allison JP - J. Exp. Med. (2009)

Unicompartmental blockade with aMuCTLA-4 during in vitro suppressor assays suggests both cell autonomous and non–cell autonomous activities of CTLA-4. Suppressor assays were performed using mixtures of WT and HuTg cells. (a and b) Proliferation of 50,000 purified WT or HuTg CD4+CD25− and CD4+CD25+ T cells in response to T cell–depleted splenocytes and anti-CD3 and in the presence of control IgG or aMuCTLA-4, confirming the species specificity of the CTLA-4 blockade. (c) Unicompartmental blockade of 50,000 WT CD4+CD25− T cells with aMuCTLA-4, compared with control IgG during in vitro suppression by addition of increasing numbers of HuTg CD4+CD25+ T reg cells. (d) Unicompartmental blockade of WT CD4+CD25+ T reg cells with aMuCTLA-4, compared with control IgG during in vitro suppression of 50,000 HuTg CD4+CD25− T cells. (e) Bicompartmental blockade of both WT CD4+CD25− Teff and CD4+CD25+ T reg cells with aMuCTLA-4, compared with control IgG during in vitro suppressor assays. Data in a–e represent three or more independent experiments, and in each group replicates were performed as quintuplets. Error bars indicate SD.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2722174&req=5

fig2: Unicompartmental blockade with aMuCTLA-4 during in vitro suppressor assays suggests both cell autonomous and non–cell autonomous activities of CTLA-4. Suppressor assays were performed using mixtures of WT and HuTg cells. (a and b) Proliferation of 50,000 purified WT or HuTg CD4+CD25− and CD4+CD25+ T cells in response to T cell–depleted splenocytes and anti-CD3 and in the presence of control IgG or aMuCTLA-4, confirming the species specificity of the CTLA-4 blockade. (c) Unicompartmental blockade of 50,000 WT CD4+CD25− T cells with aMuCTLA-4, compared with control IgG during in vitro suppression by addition of increasing numbers of HuTg CD4+CD25+ T reg cells. (d) Unicompartmental blockade of WT CD4+CD25+ T reg cells with aMuCTLA-4, compared with control IgG during in vitro suppression of 50,000 HuTg CD4+CD25− T cells. (e) Bicompartmental blockade of both WT CD4+CD25− Teff and CD4+CD25+ T reg cells with aMuCTLA-4, compared with control IgG during in vitro suppressor assays. Data in a–e represent three or more independent experiments, and in each group replicates were performed as quintuplets. Error bars indicate SD.
Mentions: In accordance with the species-specific binding of anti–CTLA-4 mAb (Fig. 1, a and b), functional blockade with an aMuCTLA-4 (clone 9H10) was also species specific (Fig. 2, a and b). Purified populations of either CD4+CD25− or CD4+CD25+ WT T cells proliferated to a significantly greater degree in the presence of aMuCTLA-4 than control IgG in thymidine incorporation assays (Fig. 2 a), whereas neither population of purified cells from HuTg mice showed enhanced proliferation in the presence of aMuCTLA-4 (Fig. 2 b). The direct effect on purified effector and regulatory WT cells highlights the cell autonomous role of CTLA-4 in inhibiting T cell proliferation. The demonstration that aMuCTLA-4 produces functional blockade in a species-specific manner allowed us to examine the effects of unicompartmental blockade of either the T reg or non–T reg cell populations.

Bottom Line: The data show that although blockade on effector cells significantly improves tumor protection, unicompartmental blockade on regulatory cells completely fails to enhance antitumor responses.However, concomitant blockade of both compartments leads to a synergistic effect and maximal antitumor activity.We conclude that the combination of direct enhancement of T(eff) cell function and concomitant inhibition of T reg cell activity through blockade of CTLA-4 on both cell types is essential for mediating the full therapeutic effects of anti-CTLA-4 antibodies during cancer immunotherapy.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Immunology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.

ABSTRACT
Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical negative regulator of immune responses. Uniquely among known inhibitory receptors, its genetic ablation results in a fulminating and fatal lymphoproliferative disorder. This central regulatory role led to the development of antibodies designed to block CTLA-4 activity in vivo, aiming to enhance immune responses against cancer. Despite their preclinical efficacy and promising clinical activity against late stage metastatic melanoma, the critical cellular targets for their activity remains unclear. In particular, debate has focused on whether the effector T cell (T(eff)) or regulatory T cell (T reg cell) compartment is the primary target of antibody-mediated blockade. We developed a mouse expressing human instead of mouse CTLA-4, allowing us to evaluate the independent contributions of CTLA-4 blockade of each T cell compartment during cancer immunotherapy in an in vivo model of mouse melanoma. The data show that although blockade on effector cells significantly improves tumor protection, unicompartmental blockade on regulatory cells completely fails to enhance antitumor responses. However, concomitant blockade of both compartments leads to a synergistic effect and maximal antitumor activity. We conclude that the combination of direct enhancement of T(eff) cell function and concomitant inhibition of T reg cell activity through blockade of CTLA-4 on both cell types is essential for mediating the full therapeutic effects of anti-CTLA-4 antibodies during cancer immunotherapy.

Show MeSH
Related in: MedlinePlus