Human CLEC9A antibodies deliver Wilms' tumor 1 (WT1) antigen to CD141+ dendritic cells to activate naïve and memory WT1‐specific CD8+ T cells

Objectives Vaccines that prime Wilms' tumor 1 (WT1)‐specific CD8+ T cells are attractive cancer immunotherapies. However, immunogenicity and clinical response rates may be enhanced by delivering WT1 to CD141+ dendritic cells (DCs). The C‐type lectin‐like receptor CLEC9A is expressed exclusively by CD141+ DCs and regulates CD8+ T‐cell responses. We developed a new vaccine comprising a human anti‐CLEC9A antibody fused to WT1 and investigated its capacity to target human CD141+ DCs and activate naïve and memory WT1‐specific CD8+ T cells. Methods WT1 was genetically fused to antibodies specific for human CLEC9A, DEC‐205 or β‐galactosidase (untargeted control). Activation of WT1‐specific CD8+ T‐cell lines following cross‐presentation by CD141+ DCs was quantified by IFNγ ELISPOT. Humanised mice reconstituted with human immune cell subsets, including a repertoire of naïve WT1‐specific CD8+ T cells, were used to investigate naïve WT1‐specific CD8+ T‐cell priming. Results The CLEC9A‐WT1 vaccine promoted cross‐presentation of WT1 epitopes to CD8+ T cells and mediated priming of naïve CD8+ T cells more effectively than the DEC‐205‐WT1 and untargeted control‐WT1 vaccines. Conclusions Delivery of WT1 to CD141+ DCs via CLEC9A stimulates CD8+ T cells more potently than either untargeted delivery or widespread delivery to all Ag‐presenting cells via DEC‐205, suggesting that cross‐presentation by CD141+ DCs is sufficient for effective CD8+ T‐cell priming in humans. The CLEC9A‐WT1 vaccine is a promising candidate immunotherapy for malignancies that express WT1

Dendritic cells and cancer immunotherapy

Dendritic cells (DC) play an essential role in the induction and regulation of immune responses, including the generation of cytotoxic T lymphocytes (CTL) for the eradication of cancers. DC-based cancer vaccines are well tolerated with few side effects and can generate anti-tumour immune responses, but overall they have been of limited benefit. Recent studies have demonstrated that CD141 DC play an important role in anti-tumour responses. These are now attractive targets for the development of vaccines that directly target DC in vivo. An understanding of the functional specialisations of DC subsets, strategies for the delivery of tumour Ag to DC and for enhancing immune responses, point to promising new avenues for the design of more effective DC-based cancer vaccines

Activation of human CD141+ and CD1c+ dendritic cells in vivo with combined TLR 3 and TLR 7/8 ligation

Mice reconstituted with human hematopoietic stem cells are valuable models to study aspects of the human immune system in vivo. We describe a humanized mouse model (hu mice) in which fully functional human CD141+ and CD1c+ myeloid and CD123+ plasmacytoid dendritic cells (DC) develop from human cord blood CD34+ cells in immunodeficient mice. CD141+ DC are the human equivalents of murine CD8+ /CD103+ DC which are essential for the induction of tumor-inhibitory cytotoxic T lymphocyte (CTL) responses, making them attractive targets to exploit for the development of new cancer immunotherapies. We used CD34+ -engrafted NSG-A2 mice to investigate activation of DC subsets by synthetic dsRNA or ssRNA analogues polyinosinic-polycytidylic acid/poly I:C and Resiquimod/R848, agonists for TLR3 and TLR8 respectively, both of which are expressed by CD141+ DC. Injection of hu mice with these agonists resulted in upregulation of costimulatory molecules CD80, CD83 and CD86 by CD141+ and CD1c+ DC alike, and their combination further enhanced expression of these molecules by both subsets. When combined, poly I:C and R848 enhanced serum levels of key cytokines associated with cross-presentation and the induction of CTL responses including IFN-α, IFN-β, IL-12 and CXCL10. These data advocate a combination of poly I:C and R848 TLR agonists as means of activating human DC for immunotherapy. This article is protected by copyright. All rights reserved

Targeting CLEC9A delivers antigen to human CD141⁺ DC for CD4⁺ and CD8⁺ T cell recognition

DC-based vaccines that initiate T cell responses are well tolerated and have demonstrated efficacy for tumor immunotherapy, with the potential to be combined with other therapies. Targeting vaccine antigens (Ag) directly to the DCs in vivo is more effective than cell-based therapies in mouse models and is therefore a promising strategy to translate to humans. The human CD141(+) DCs are considered the most clinically relevant for initiating CD8(+) T cell responses critical for killing tumors or infected cells, and they specifically express the C-type lectin-like receptor CLEC9A that facilitates presentation of Ag by these DCs. We have therefore developed a human chimeric Ab that specifically targets CLEC9A on CD141(+) DCs in vitro and in vivo. These human chimeric Abs are highly effective at delivering Ag to DCs for recognition by both CD4(+) and CD8(+) T cells. Given the importance of these cellular responses for antitumor or antiviral immunity, and the superior specificity of anti-CLEC9A Abs for this DC subset, this approach warrants further development for vaccines

Human CLEC9A antibodies deliver NY-ESO-1 antigen to CD141+ dendritic cells to activate naïve and memory NY-ESO-1-specific CD8+ T cells

Background Dendritic cells (DCs) are crucial for the efficacy of cancer vaccines, but current vaccines do not harness the key cDC1 subtype required for effective CD8+ T-cell-mediated tumor immune responses. Vaccine immunogenicity could be enhanced by specific delivery of immunogenic tumor antigens to CD141+ DCs, the human cDC1 equivalent. CD141+ DCs exclusively express the C-type-lectin-like receptor CLEC9A, which is important for the regulation of CD8+ T cell responses. This study developed a new vaccine that harnesses a human anti-CLEC9A antibody to specifically deliver the immunogenic tumor antigen, NY-ESO-1 (New York esophageal squamous cell carcinoma 1), to human CD141+ DCs. The ability of the CLEC9A-NY-ESO-1 antibody to activate NY-ESO-1-specific naïve and memory CD8+ T cells was examined and compared with a vaccine comprised of a human DEC-205-NY-ESO-1 antibody that targets all human DCs.Methods Human anti-CLEC9A, anti-DEC-205 and isotype control IgG4 antibodies were genetically fused to NY-ESO-1 polypeptide. Cross-presentation to NY-ESO-1-epitope-specific CD8+ T cells and reactivity of T cell responses in patients with melanoma were assessed by interferon γ (IFNγ) production following incubation of CD141+ DCs and patient peripheral blood mononuclear cells with targeting antibodies. Humanized mice containing human DC subsets and a repertoire of naïve NY-ESO-1-specific CD8+ T cells were used to investigate naïve T cell priming. T cell effector function was measured by expression of IFNγ, MIP-1β, tumor necrosis factor and CD107a and by lysis of target tumor cells.Results CLEC9A-NY-ESO-1 antibodies (Abs) were effective at mediating delivery and cross-presentation of multiple NY-ESO-1 epitopes by CD141+ DCs for activation of NY-ESO-1-specific CD8+ T cells. When benchmarked to NY-ESO-1 conjugated to an untargeted control antibody or to anti-human DEC-205, CLEC9A-NY-ESO-1 was superior at ex vivo reactivation of NY-ESO-1-specific T cell responses in patients with melanoma. Moreover, CLEC9A-NY-ESO-1 induced priming of naïve NY-ESO-1-specific CD8+ T cells with polyclonal effector function and potent tumor killing capacity in vitro.Conclusions These data advocate human CLEC9A-NY-ESO-1 Ab as an attractive strategy for specific targeting of CD141+ DCs to enhance tumor immunogenicity in NY-ESO-1-expressing malignancies

Self-adjuvanting nanoemulsion targeting dendritic cell receptor Clec9A enables antigen-specific immunotherapy

Bijun Zeng, Anton P.J. Middelberg, Adrian Gemiarto, Kelli MacDonald, Alan G. Baxter, Meghna Talekar, Davide Moi, Kirsteen M. Tullett, Irina Caminschi, Mireille H. Lahoud, Roberta Mazzieri, Riccardo Dolcetti and Ranjeny ThomasNon–antigen-specific stimulatory cancer immunotherapies are commonly complicated by off-target effects. Antigen-specific immunotherapy, combining viral tumor antigen or personalized neoepitopes with immune targeting, offers a solution. However, the lack of flexible systems targeting tumor antigens to cross-presenting dendritic cells (DCs) limits clinical development. Although antigen–anti-Clec9A mAb conjugates target cross-presenting DCs, adjuvant must be codelivered for cytotoxic T lymphocyte (CTL) induction. We functionalized tailored nanoemulsions encapsulating tumor antigens to target Clec9A (Clec9A-TNE). Clec9A-TNE encapsulating OVA antigen targeted and activated cross-presenting DCs without additional adjuvant, promoting antigen-specific CD4⁺ and CD8⁺ T cell proliferation and CTL and antibody responses. OVA-Clec9A-TNE-induced DC activation required CD4 and CD8 epitopes, CD40, and IFN-α. Clec9A-TNE encapsulating HPV E6/E7 significantly suppressed HPV-associated tumor growth, while E6/E7-CpG did not. Clec9A-TNE loaded with pooled B16-F10 melanoma neoepitopes induced epitope-specific CD4⁺ and CD8⁺ T cell responses, permitting selection of immunogenic neoepitopes. Clec9A-TNE encapsulating 6 neoepitopes significantly suppressed B16-F10 melanoma growth in a CD4⁺ T cell-dependent manner. Thus, cross-presenting DCs targeted with antigen-Clec9A-TNE stimulate therapeutically effective tumor-specific immunity, dependent on T cell help

Human CLEC9A antibodies deliver NY-ESO-1 antigen to CD141+ dendritic cells to activate naïve and memory NY-ESO-1-specific CD8+ T cells

Dendritic cells (DCs) are crucial for the efficacy of cancer vaccines, but current vaccines do not harness the key cDC1 subtype required for effective CD8+ T-cell-mediated tumor immune responses. Vaccine immunogenicity could be enhanced by specific delivery of immunogenic tumor antigens to CD141+ DCs, the human cDC1 equivalent. CD141+ DCs exclusively express the C-type-lectin-like receptor CLEC9A, which is important for the regulation of CD8+ T cell responses. This study developed a new vaccine that harnesses a human anti-CLEC9A antibody to specifically deliver the immunogenic tumor antigen, NY-ESO-1 (New York esophageal squamous cell carcinoma 1), to human CD141+ DCs. The ability of the CLEC9A-NY-ESO-1 antibody to activate NY-ESO-1-specific naïve and memory CD8+ T cells was examined and compared with a vaccine comprised of a human DEC-205-NY-ESO-1 antibody that targets all human DCs. Human anti-CLEC9A, anti-DEC-205 and isotype control IgG4 antibodies were genetically fused to NY-ESO-1 polypeptide. Cross-presentation to NY-ESO-1-epitope-specific CD8+ T cells and reactivity of T cell responses in patients with melanoma were assessed by interferon γ (IFNγ) production following incubation of CD141+ DCs and patient peripheral blood mononuclear cells with targeting antibodies. Humanized mice containing human DC subsets and a repertoire of naïve NY-ESO-1-specific CD8+ T cells were used to investigate naïve T cell priming. T cell effector function was measured by expression of IFNγ, MIP-1β, tumor necrosis factor and CD107a and by lysis of target tumor cells. CLEC9A-NY-ESO-1 antibodies (Abs) were effective at mediating delivery and cross-presentation of multiple NY-ESO-1 epitopes by CD141+ DCs for activation of NY-ESO-1-specific CD8+ T cells. When benchmarked to NY-ESO-1 conjugated to an untargeted control antibody or to anti-human DEC-205, CLEC9A-NY-ESO-1 was superior at ex vivo reactivation of NY-ESO-1-specific T cell responses in patients with melanoma. Moreover, CLEC9A-NY-ESO-1 induced priming of naïve NY-ESO-1-specific CD8+ T cells with polyclonal effector function and potent tumor killing capacity in vitro. These data advocate human CLEC9A-NY-ESO-1 Ab as an attractive strategy for specific targeting of CD141+ DCs to enhance tumor immunogenicity in NY-ESO-1-expressing malignancies

Human CLEC9A antibodies deliver NY-ESO-1 antigen to CD141+ dendritic cells to activate naïve and memory NY-ESO-1-specific CD8+ T cells

BACKGROUND: Dendritic cells (DCs) are crucial for the efficacy of cancer vaccines, but current vaccines do not harness the key cDC1 subtype required for effective CD8+ T-cell-mediated tumor immune responses. Vaccine immunogenicity could be enhanced by specific delivery of immunogenic tumor antigens to CD141+ DCs, the human cDC1 equivalent. CD141+ DCs exclusively express the C-type-lectin-like receptor CLEC9A, which is important for the regulation of CD8+ T cell responses. This study developed a new vaccine that harnesses a human anti-CLEC9A antibody to specifically deliver the immunogenic tumor antigen, NY-ESO-1 (New York esophageal squamous cell carcinoma 1), to human CD141+ DCs. The ability of the CLEC9A-NY-ESO-1 antibody to activate NY-ESO-1-specific naïve and memory CD8+ T cells was examined and compared with a vaccine comprised of a human DEC-205-NY-ESO-1 antibody that targets all human DCs. METHODS: Human anti-CLEC9A, anti-DEC-205 and isotype control IgG4 antibodies were genetically fused to NY-ESO-1 polypeptide. Cross-presentation to NY-ESO-1-epitope-specific CD8+ T cells and reactivity of T cell responses in patients with melanoma were assessed by interferon γ (IFNγ) production following incubation of CD141+ DCs and patient peripheral blood mononuclear cells with targeting antibodies. Humanized mice containing human DC subsets and a repertoire of naïve NY-ESO-1-specific CD8+ T cells were used to investigate naïve T cell priming. T cell effector function was measured by expression of IFNγ, MIP-1β, tumor necrosis factor and CD107a and by lysis of target tumor cells. RESULTS: CLEC9A-NY-ESO-1 antibodies (Abs) were effective at mediating delivery and cross-presentation of multiple NY-ESO-1 epitopes by CD141+ DCs for activation of NY-ESO-1-specific CD8+ T cells. When benchmarked to NY-ESO-1 conjugated to an untargeted control antibody or to anti-human DEC-205, CLEC9A-NY-ESO-1 was superior at ex vivo reactivation of NY-ESO-1-specific T cell responses in patients with melanoma. Moreover, CLEC9A-NY-ESO-1 induced priming of naïve NY-ESO-1-specific CD8+ T cells with polyclonal effector function and potent tumor killing capacity in vitro. CONCLUSIONS: These data advocate human CLEC9A-NY-ESO-1 Ab as an attractive strategy for specific targeting of CD141+ DCs to enhance tumor immunogenicity in NY-ESO-1-expressing malignancies