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Atay C, Medina-Echeverz J, Hochrein H, Suter M, Hinterberger M. Armored modified vaccinia Ankara in cancer immunotherapy. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2023; 379:87-142. [PMID: 37541728 DOI: 10.1016/bs.ircmb.2023.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/06/2023]
Abstract
Cancer immunotherapy relies on unleashing the patient´s immune system against tumor cells. Cancer vaccines aim to stimulate both the innate and adaptive arms of immunity to achieve durable clinical responses. Some roadblocks for a successful cancer vaccine in the clinic include the tumor antigen of choice, the adjuvants employed to strengthen antitumor-specific immune responses, and the risks associated with enhancing immune-related adverse effects in patients. Modified vaccinia Ankara (MVA) belongs to the family of poxviruses and is a versatile vaccine platform that combines several attributes crucial for cancer therapy. First, MVA is an excellent inducer of innate immune responses leading to type I interferon secretion and induction of T helper cell type 1 (Th1) immune responses. Second, it elicits robust and durable humoral and cellular immunity against vector-encoded heterologous antigens. Third, MVA has enormous genomic flexibility, which allows for the expression of multiple antigenic and costimulatory entities. And fourth, its replication deficit in human cells ensures a excellent safety profile. In this review, we summarize the current understanding of how MVA induces innate and adaptive immune responses. Furthermore, we will give an overview of the tumor-associated antigens and immunomodulatory molecules that have been used to armor MVA and describe their clinical use. Finally, the route of MVA immunization and its impact on therapeutic efficacy depending on the immunomodulatory molecules expressed will be discussed.
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Affiliation(s)
- Cigdem Atay
- Bavarian Nordic GmbH, Fraunhoferstr.13, Planegg, Germany
| | | | | | - Mark Suter
- Prof. em. University of Zurich, Switzerland
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Hinterberger M, Endt K, Bathke B, Habjan M, Heiseke A, Schweneker M, Von Rohrscheidt J, Atay C, Chaplin P, Kalla M, Hausmann J, Schmittwolf C, Lauterbach H, Volkmann A, Hochrein H, Medina-Echeverz J. Preclinical development of a first-in-class vaccine encoding HER2, Brachyury and CD40L for antibody enhanced tumor eradication. Sci Rep 2023; 13:5162. [PMID: 36997583 PMCID: PMC10060934 DOI: 10.1038/s41598-023-32060-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 03/21/2023] [Indexed: 04/03/2023] Open
Abstract
The induction of antiviral innate immunity by systemic immunization with live virus can be employed to positively impact the response to therapeutic vaccination. We previously demonstrated that systemic immunization with a non-replicating MVA encoding CD40 ligand (CD40L) enhances innate immune cell activation and function, and triggers potent antitumor CD8+ T cell responses in different murine tumor models. Antitumor efficacy was increased when combined with tumor targeting antibodies. Here we report the development of TAEK-VAC-HerBy (TVH), a first-in-class human tumor antibody enhanced killing (TAEK) vaccine based on the non-replicating MVA-BN viral vector. It encodes the membrane bound form of human CD40L, HER2 and the transcription factor Brachyury. TVH is designed for therapeutic use in HER2- or Brachyury-expressing cancer patients in combination with tumor targeting antibodies. To preclude possible oncogenic activities in infected cells and to prevent binding of vaccine-encoded HER2 by monoclonal antibodies trastuzumab and pertuzumab, genetic modifications of HER2 were introduced in the vaccine. Brachyury was genetically modified to prevent nuclear localization of the protein thereby inhibiting its transcriptional activity. CD40L encoded in TVH enhanced human leukocyte activation and cytokine secretion in vitro. Lastly, TVH intravenous administration to non-human primates was proven immunogenic and safe in a repeat-dose toxicity study. Nonclinical data presented here highlight TVH as a first-in-class immunotherapeutic vaccine platform currently under clinical investigation.
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Affiliation(s)
| | - Kathrin Endt
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | - Barbara Bathke
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | - Matthias Habjan
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | - Alexander Heiseke
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
- GlaxoSmithKline GmbH, Prinzregentenpl. 9, 81675, Munich, Germany
| | - Marc Schweneker
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | - Julia Von Rohrscheidt
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
- Origenis GmbH, Am Klopferspitz 19A, 82152, Planegg, Germany
| | - Cigdem Atay
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | - Paul Chaplin
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | - Markus Kalla
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | - Jürgen Hausmann
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | | | - Henning Lauterbach
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
- Hookipa Pharma Inc, 350 Fifth Avenue, Room/Suite 7240, New York City, NY, USA
| | - Ariane Volkmann
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
| | | | - José Medina-Echeverz
- Bavarian Nordic GmbH, Fraunhoferstr.13, 82152, Planegg, Germany
- Affimed, Im Neuenheimer Feld 582, 69120, Heidelberg, Germany
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Hinterberger M, Giessel R, Fiore G, Graebnitz F, Bathke B, Wennier S, Chaplin P, Melero I, Suter M, Lauterbach H, Berraondo P, Hochrein H, Medina-Echeverz J. Intratumoral virotherapy with 4-1BBL armed modified vaccinia Ankara eradicates solid tumors and promotes protective immune memory. J Immunother Cancer 2021; 9:jitc-2020-001586. [PMID: 33579736 PMCID: PMC7883866 DOI: 10.1136/jitc-2020-001586] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2020] [Indexed: 12/12/2022] Open
Abstract
Background Human cancers are extraordinarily heterogeneous in terms of tumor antigen expression, immune infiltration and composition. A common feature, however, is the host′s inability to mount potent immune responses that prevent tumor growth effectively. Often, naturally primed CD8+ T cells against solid tumors lack adequate stimulation and efficient tumor tissue penetration due to an immune hostile tumor microenvironment. Methods To address these shortcomings, we cloned tumor-associated antigens (TAA) and the immune-stimulatory ligand 4-1BBL into the genome of modified vaccinia Ankara (MVA) for intratumoral virotherapy. Results Local treatment with MVA-TAA-4-1BBL resulted in control of established tumors. Intratumoral injection of MVA localized mainly to the tumor with minimal leakage to the tumor-draining lymph node. In situ infection by MVA-TAA-4-1BBL triggered profound changes in the tumor microenvironment, including the induction of multiple proinflammatory molecules and immunogenic cell death. These changes led to the reactivation and expansion of antigen-experienced, tumor-specific cytotoxic CD8+ T cells that were essential for the therapeutic antitumor effect. Strikingly, we report the induction of a systemic antitumor immune response including tumor antigen spread by local MVA-TAA-4-1BBL treatment which controlled tumor growth at distant, untreated lesions and protected against local and systemic tumor rechallenge. In all cases, 4-1BBL adjuvanted MVA was superior to MVA. Conclusion Intratumoral 4-1BBL-armed MVA immunotherapy induced a profound reactivation and expansion of potent tumor-specific CD8+ T cells as well as favorable proinflammatory changes in the tumor microenvironment, leading to elimination of tumors and protective immunological memory.
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Affiliation(s)
| | | | | | | | | | | | | | - Ignacio Melero
- Program of Immunology and Immunotherapy, Cima Universidad de Navarra, Pamplona, Spain.,IdiSNA, Navarra Institute for Health Research, Pamplona, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Pamplona, Spain.,Department of Oncology, Clínica Universidad de Navarra, Pamplona, Spain
| | - Mark Suter
- Bavarian Nordic GmbH, Planegg, Germany.,Vetsuisse Fakultät, Dekanat, Bereich Immunologie, Universität Zürich, Zürich, Switzerland
| | - Henning Lauterbach
- Bavarian Nordic GmbH, Planegg, Germany.,Present address: Hookipa Pharma Inc, 350 Fifth Avenue, Room/Suite 7240, New York City, New York, USA
| | - Pedro Berraondo
- Program of Immunology and Immunotherapy, Cima Universidad de Navarra, Pamplona, Spain.,IdiSNA, Navarra Institute for Health Research, Pamplona, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Pamplona, Spain
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Synergistic cancer immunotherapy combines MVA-CD40L induced innate and adaptive immunity with tumor targeting antibodies. Nat Commun 2019; 10:5041. [PMID: 31695037 PMCID: PMC6834557 DOI: 10.1038/s41467-019-12998-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 10/10/2019] [Indexed: 12/11/2022] Open
Abstract
Virus-based vaccines and appropriate costimulation potently enhance antigen-specific T cell immunity against cancer. Here we report the use of recombinant modified vaccinia virus Ankara (rMVA) encoding costimulatory CD40L against solid tumors. Therapeutic treatment with rMVA-CD40L-expressing tumor-associated antigens results in the control of established tumors. The expansion of tumor-specific cytotoxic CD8+ T cells is essential for the therapeutic antitumor effects. Strikingly, rMVA-CD40L also induces strong natural killer (NK) cell activation and expansion. Moreover, the combination of rMVA-CD40L and tumor-targeting antibodies results in increased therapeutic antitumor efficacy relying on the presence of Fc receptor and NK cells. We describe a translationally relevant therapeutic synergy between systemic viral vaccination and CD40L costimulation. We show strengthened antitumor immune responses when both rMVA-CD40L-induced innate and adaptive immune mechanisms are exploited by combination with tumor-targeting antibodies. This immunotherapeutic approach could translate into clinical cancer therapies where tumor-targeting antibodies are employed. CD40 agonists have been investigated as a strategy to awaken the immune system against cancers. Here, the authors use a virus encoding CD40L and tumour-associated antigens to enhance innate and adaptive immunity that together with tumour targeting antibodies controls the growth of tumours in mice.
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Bathke B, Pätzold J, Kassub R, Giessel R, Lämmermann K, Hinterberger M, Brinkmann K, Chaplin P, Suter M, Hochrein H, Lauterbach H. CD70 encoded by modified vaccinia virus Ankara enhances CD8 T-cell-dependent protective immunity in MHC class II-deficient mice. Immunology 2018; 154:285-297. [PMID: 29281850 PMCID: PMC5980220 DOI: 10.1111/imm.12884] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 11/28/2017] [Accepted: 12/03/2017] [Indexed: 12/13/2022] Open
Abstract
The immunological outcome of infections and vaccinations is largely determined during the initial first days in which antigen-presenting cells instruct T cells to expand and differentiate into effector and memory cells. Besides the essential stimulation of the T-cell receptor complex a plethora of co-stimulatory signals not only ensures a proper T-cell activation but also instils phenotypic and functional characteristics in the T cells appropriate to fight off the invading pathogen. The tumour necrosis factor receptor/ligand pair CD27/CD70 gained a lot of attention because of its key role in regulating T-cell activation, survival, differentiation and maintenance, especially in the course of viral infections and cancer. We sought to investigate the role of CD70 co-stimulation for immune responses induced by the vaccine vector modified vaccinia virus Ankara-Bavarian Nordic® (MVA-BN® ). Short-term blockade of CD70 diminished systemic CD8 T-cell effector and memory responses in mice. The dependence on CD70 became even more apparent in the lungs of MHC class II-deficient mice. Importantly, genetically encoded CD70 in MVA-BN® not only increased CD8 T-cell responses in wild-type mice but also substituted for CD4 T-cell help. MHC class II-deficient mice that were immunized with recombinant MVA-CD70 were fully protected against a lethal virus infection, whereas MVA-BN® -immunized mice failed to control the virus. These data are in line with CD70 playing an important role for vaccine-induced CD8 T-cell responses and prove the potency of integrating co-stimulatory molecules into the MVA-BN® backbone.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Mark Suter
- Vetsuisse Fakultät, Dekanat, Bereich Immunologie, Universität Zürich, Zurich, Switzerland
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Sanos SL, Kassub R, Testori M, Geiger M, Pätzold J, Giessel R, Knallinger J, Bathke B, Gräbnitz F, Brinkmann K, Chaplin P, Suter M, Hochrein H, Lauterbach H. NLRC4 Inflammasome-Driven Immunogenicity of a Recombinant MVA Mucosal Vaccine Encoding Flagellin. Front Immunol 2018; 8:1988. [PMID: 29416534 PMCID: PMC5787573 DOI: 10.3389/fimmu.2017.01988] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 12/21/2017] [Indexed: 01/12/2023] Open
Abstract
Bacterial flagellin enhances innate and adaptive immune responses and is considered a promising adjuvant for the development of vaccines against infectious diseases and cancer. Antigen-presenting cells recognize flagellin with the extracellular TLR5 and the intracellular NLRC4 inflammasome-mediated pathway. The detailed cooperation of these innate pathways in the induction of the adaptive immune response following intranasal (i.n.) administration of a recombinant modified vaccinia virus Ankara (rMVA) vaccine encoding flagellin (rMVA-flagellin) is not known. rMVA-flagellin induced enhanced secretion of mucosal IL-1β and TNF-α resulting in elevated CTL and IgG2c antibody responses. Importantly, mucosal IgA responses were also significantly enhanced in both bronchoalveolar (BAL) and intestinal lavages accompanied by the increased migration of CD8+ T cells to the mesenteric lymph nodes (MLN). Nlrc4−/− rMVA-flagellin-immunized mice failed to enhance pulmonary CTL responses, IgG2c was lower, and IgA levels in the BAL or intestinal lavages were similar as those of control mice. Our results show the favorable adjuvant effect of rMVA-flagellin in the lung as well as the intestinal mucosa following i.n. administration with NLRC4 as the essential driver of this promising mucosal vaccine concept.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Mark Suter
- University of Zurich, Zurich, Switzerland
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Poxvirus-based active immunotherapy synergizes with CTLA-4 blockade to increase survival in a murine tumor model by improving the magnitude and quality of cytotoxic T cells. Cancer Immunol Immunother 2016; 65:537-49. [PMID: 26961085 PMCID: PMC4840227 DOI: 10.1007/s00262-016-1816-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 02/23/2016] [Indexed: 01/01/2023]
Abstract
The dramatic clinical benefit of immune checkpoint blockade for a fraction of cancer patients suggests the potential for further clinical benefit in a broader cancer patient population by combining immune checkpoint inhibitors with active immunotherapies. The anti-tumor efficacy of MVA-BN-HER2 poxvirus-based active immunotherapy alone or in combination with CTLA-4 checkpoint blockade was investigated in a therapeutic CT26-HER-2 lung metastasis mouse model. MVA-BN-HER2 immunotherapy significantly improved the median overall survival compared to untreated controls or CTLA-4 blockade alone (p < 0.001). Robust synergistic efficacy was achieved with the combination therapy (p < 0.01). Improved survival following MVA-BN-HER2 administration was accompanied by increased tumor infiltration by HER-2-specific cytotoxic T lymphocytes (CTL). These tumor-specific CTL had characteristics similar to antiviral CTL, including strong expression of activation markers and co-expression of IFNγ and TNFα. Combination with CTLA-4 blockade significantly increased the magnitude of HER-2-specific T cell responses, with a higher proportion co-expressing TNFα and/or IL-2 with IFNγ. Furthermore, in mice treated with MVA-BN-HER2 (alone or in combination with CTLA-4 blockade), the inducible T cell co-stimulator (ICOS) protein was expressed predominantly on CD4 and CD8 effector T cells but not on regulatory T cells (T(reg)). In contrast, mice left untreated or treated solely with CTLA-4 blockade harbored elevated ICOS(+) Treg, a phenotype associated with highly suppressive activity. In conclusion, poxvirus-based active immunotherapy induced robust tumor infiltration by highly efficient effector T cells. Combination with CTLA-4 immune checkpoint blockade amplified this response resulting in synergistically improved efficacy. These hypothesis-generating data may help elucidate evidence of enhanced clinical benefit from combining CTLA-4 blockade with poxvirus-based active immunotherapy.
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Generation of a soluble recombinant trimeric form of bovine CD40L and its potential use as a vaccine adjuvant in cows. Vet Immunol Immunopathol 2015; 168:1-13. [PMID: 26553560 DOI: 10.1016/j.vetimm.2015.09.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 09/11/2015] [Accepted: 09/22/2015] [Indexed: 11/24/2022]
Abstract
Vaccination is the most cost-effective way to control infectious diseases in cattle. However, many infectious diseases leading to severe economical losses worldwide still remain for which a really effective and safe vaccine is not available. These diseases are most often due to intracellular pathogens such as bacteria or viruses, which are, by their localization, protected from antibiotics and/or CD4(+) T cell-dependent humoral responses. We therefore postulated that strategies leading to induction of not only CD4(+) T cell responses but also CD8(+) cytotoxic T lymphocyte (CTL) responses against infected cells should be privileged in the development of new vaccines against problematic intracellular pathogens in bovines. CD40 signaling in antigen-presenting cells may lead to the induction of robust CD4-independent CTL responses and several studies, especially in mice, have used CD40 stimulation to promote CD8(+) T cell-mediated immunity. For example, we have recently shown that immunization of mice with heat-killed Staphylococcus aureus (HKSA) and agonistic anti-CD40 monoclonal antibodies elicits strong CTL responses capable of protecting mice from subsequent staphylococcal mastitis. Unfortunately, there is at present no tool available to efficiently stimulate CD40 in cattle. In this study, we therefore first produced a soluble recombinant trimeric form of the natural bovine CD40 ligand (sboCD40LT). We then observed that sboCD40LT was able to potently stimulate bovine cells in vitro. Finally, we provide evidence that immunization of cows with sboCD40LT combined with HKSA was able to significantly increase the number of both HKSA-specific CD4(+) and CD8(+) T cells in the draining lymph nodes. In conclusion, we suggest that this new molecular tool could help in the development of vaccine strategies against bovine diseases caused by intracellular pathogens.
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García-Arriaza J, Esteban M. Enhancing poxvirus vectors vaccine immunogenicity. Hum Vaccin Immunother 2015; 10:2235-44. [PMID: 25424927 DOI: 10.4161/hv.28974] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Attenuated recombinant poxvirus vectors expressing heterologous antigens from pathogens are currently at various stages in clinical trials with the aim to establish their efficacy. This is because these vectors have shown excellent safety profiles, significant immunogenicity against foreign expressed antigens and are able to induce protective immune responses. In view of the limited efficacy triggered by some poxvirus strains used in clinical trials (i.e, ALVAC in the RV144 phase III clinical trial for HIV), and of the restrictive replication capacity of the highly attenuated vectors like MVA and NYVAC, there is a consensus that further improvements of these vectors should be pursuit. In this review we considered several strategies that are currently being implemented, as well as new approaches, to improve the immunogenicity of the poxvirus vectors. This includes heterologous prime/boost protocols, use of co-stimulatory molecules, deletion of viral immunomodulatory genes still present in the poxvirus genome, enhancing virus promoter strength, enhancing vector replication capacity, optimizing expression of foreign heterologous sequences, and the combined use of adjuvants. An optimized poxvirus vector triggering long-lasting immunity with a high protective efficacy against a selective disease should be sought.
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Affiliation(s)
- Juan García-Arriaza
- a Department of Molecular and Cellular Biology; Centro Nacional de Biotecnología; Consejo Superior de Investigaciones Científicas (CSIC); Madrid, Spain
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Immunogenicity and protective efficacy of an Eimeria vaccine candidate based on Eimeria tenella immune mapped protein 1 and chicken CD40 ligand. Vet Parasitol 2015; 210:19-24. [DOI: 10.1016/j.vetpar.2015.03.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2015] [Revised: 03/07/2015] [Accepted: 03/15/2015] [Indexed: 11/19/2022]
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Mandl SJ, Rountree RB, Dela Cruz TB, Foy SP, Cote JJ, Gordon EJ, Trent E, Delcayre A, Franzusoff A. Elucidating immunologic mechanisms of PROSTVAC cancer immunotherapy. J Immunother Cancer 2014; 2:34. [PMID: 25328681 PMCID: PMC4201731 DOI: 10.1186/s40425-014-0034-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 08/21/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND PROSTVAC®, an active immunotherapy currently studied for the treatment of metastatic castration-resistant prostate cancer (mCRPC), consists of a heterologous prime-boost regimen with two different poxvirus-based vectors to provoke productive immune responses against prostate specific antigen (PSA) as the target tumor antigen. A Phase 2 study of PROSTVAC immunotherapy showed significantly improved median overall survival by 8.5 months and is currently being validated in a global Phase 3 study (PROSPECT; NCT01322490). Here, preclinical models were explored to investigate the mechanism of action and immune signatures of anti-tumor efficacy with PROSTVAC immunotherapy with the goal to identify potential immune correlates of clinical benefit. METHODS PROSTVAC-induced immune responses and anti-tumor efficacy were studied in male BALB/c mice. Functionality of the induced T cell response was characterized by interferon-gamma (IFNγ) ELISPOT, cytotoxic degranulation, multi-cytokine intracellular staining, and in vivo T cell depletion. Tumor infiltrating lymphocytes (TILs) were evaluated phenotypically by flow cytometry. RESULTS The heterologous prime-boost regimen of the two PROSTVAC vectors significantly enhanced the magnitude and quality of activated PSA-specific CD4 and CD8 T cell responses compared to homologous, single vector regimens. PROSTVAC-activated CD4 and CD8 T cells were highly functional as evidenced by expression of activation markers, production of multiple cytokines, and amplified cytotoxic T cell activity. Importantly, PROSTVAC immunotherapy resulted in significant anti-tumor efficacy in a transplantable prostate cancer mouse model. Antigen-spreading occurred in PROSTVAC-treated animals that rejected PSA-expressing tumors, as shown by subsequent rejection of PSA-negative tumors. In vivo CD4 and CD8 depletion revealed that both T cell subsets contributed to anti-tumor efficacy. Characterization of TILs demonstrated that PROSTVAC immunotherapy greatly increased the intra-tumoral ratio of activated effector to regulatory T cells. CONCLUSIONS PROSTVAC immunotherapy activates broad, highly functional T cell immunity to PSA and to endogenous tumor antigens via immune-mediated antigen spreading. These preclinical results further elucidate the mode of action of PROSTVAC immunotherapy and its potential causal relationship to extended overall survival as observed in the PROSTVAC Phase 2 study. The clinical validation is ongoing in the PROSPECT Phase 3 clinical study.
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Affiliation(s)
- Stefanie J Mandl
- Bavarian Nordic, Inc, 2425 Garcia Ave, Mountain View, CA 94043 USA
| | - Ryan B Rountree
- Bavarian Nordic, Inc, 2425 Garcia Ave, Mountain View, CA 94043 USA
| | | | - Susan P Foy
- Bavarian Nordic, Inc, 2425 Garcia Ave, Mountain View, CA 94043 USA
| | - Joseph J Cote
- Bavarian Nordic, Inc, 2425 Garcia Ave, Mountain View, CA 94043 USA
| | - Evan J Gordon
- Bavarian Nordic, Inc, 2425 Garcia Ave, Mountain View, CA 94043 USA
| | - Erica Trent
- Bavarian Nordic, Inc, 2425 Garcia Ave, Mountain View, CA 94043 USA
| | - Alain Delcayre
- Bavarian Nordic, Inc, 2425 Garcia Ave, Mountain View, CA 94043 USA ; ExoThera LLC, 675 Olive Street, Menlo Park, CA 94025 USA
| | - Alex Franzusoff
- Bavarian Nordic, Inc, 2425 Garcia Ave, Mountain View, CA 94043 USA
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