Chapter 7 - TLR Ligand–Peptide Conjugate Vaccines: Toward Clinical Application

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Abstract

Approaches to treat cancer with therapeutic vaccination have made significant progress. In order to induce efficient antitumor immunity, a vaccine should target and activate antigen-presenting cells, such as the dendritic cell, while delivering the tumor-derived antigen of choice. Conjugates of synthetic peptides and ligands of pattern-recognition receptors (PRRs) combine these features and, given their synthetic nature, can be produced under GMP conditions. Therefore, conjugation of antigenic peptides to potent PRR ligands is a promising vaccination approach for the treatment of cancer. This review focuses on the different PRR families that can be exploited for the design of conjugates and explores the results obtained so far with PRR ligands conjugated to antigen. The uptake and processing of Toll-like receptor ligand–peptide conjugates are discussed in more detail, as well as future directions that may further enhance the immunogenicity of conjugates.

Introduction

Cancer is routinely treated by surgery, chemotherapy, and radiation. Although refinement of these therapies has resulted in considerably lower incidences of side effects with maintenance of efficacy, the call for better targeted therapies has become stronger. In recent years, considerable progress was achieved in the field of immunotherapy.

Several immunotherapeutic antibodies against cancer are on the market, while also tumor antigen-based specific vaccine formulations are currently being developed (Buonerba et al., 2011, Pedicord et al., 2011, Zarour and Ferrone, 2011).

Cancer patients often show detectable tumor-antigen specific T-cell immunity, but a process of tolerance seems to overpower the eradication of tumor cells. Several approaches to overcome or to modulate the tolerant or suppressed state of tumor-specific T-cells are in clinical studies now, like CTLA-4 and PD-1 blockade (Pedicord et al., 2011, Rosenblatt et al., 2011). Besides, there is much progress in optimizing vaccine formulations to more effectively prime or (re)activate tumor-specific T-cells. This review focuses on optimal vaccine formulations, in more detail on synthetically defined structures that harbor the right properties for specific T-cell activation.

To achieve a state of effective antitumor immunity, a triad of immune-related hallmarks can be defined. First, a therapy should be targeted against the central antigen-presenting cell (APC), the dendritic cell (DC). This goal can be met by making use of the broad array of receptors that DCs express. At the same time, a DC should be matured in such a way that a process is set into action that will ultimately lead to presentation of tumor antigens in their MHC class I or II molecules, combined with the upregulation of costimulatory molecules. Third, the antigen that is delivered to the DC should be highly tumor specific in order to achieve antitumor immunity and evade tolerance induction.

These three hallmarks can also potentially be combined in one molecule. Conjugating antigen to a targeting molecule, such as a Toll-like receptor ligand (TLR ligand), enables the efficient delivery of tumor-derived antigen to DCs while maturing these DCs to induce (cross-)presentation to tumor-specific T-helper cells (Th cells) and cytotoxic T-cells (CTLs) (Segura and Villadangos, 2009). It is well established that besides specific CTLs, also tumor-specific Th cells are essential for proper antitumor cellular immunity. This was already demonstrated in our group over a decade ago by immunizing mice with a peptide containing either a specific or an irrelevant Th epitope and subsequently inoculating these mice with a MHC class II negative tumor. Only mice that received the tumor-specific Th epitope-containing peptide were protected from tumor outgrowth. CD8+ T-cells were identified as the effector cells responsible for tumor eradication, while it was shown that CD4+ T-cells were not able to directly recognize the tumor cells but rather cross-presented tumor antigen by local MHC class II expressing APCs (Ossendorp et al., 1998). In the same period, it was firmly established in our and other groups that T help cells for CTL priming was mainly mediated by Th–DC cell–cell contact via the CD40–CD40L interaction (Bennett et al., 1998, Ridge et al., 1998, Schoenberger et al., 1998). Therefore, effective tumor-specific vaccines should include tumor antigen-specific Th and CTL epitope sequences.

Section snippets

Central role of DCs in vaccine development

DCs play a crucial role in the initiation and control of T-cell-mediated immune responses. In the peripheral tissues, DCs reside in an immature state where they sample antigens and pathogens from their surroundings. After antigen capture in the presence of a danger signal, such as bacterial unmethylated CpG DNA or LPS, DCs undergo a complex maturation process and in vivo the DCs home to the T-cell-rich areas of the lymphoid organs, where they present antigenic peptides to specific T-cells and

Synthetic Peptide Vaccination

From a historic vaccine development perspective, whole tumor cell lysates came to the attention of researchers as a putative novel treatment of cancer. Although enhanced T-cell responses and (temporary) remission of tumors were observed using tumor lysates or DCs pulsed with these lysates (Geiger et al., 2001, Ribas et al., 2010), the popularity of this technique has diminished as it lacks adequate specificity, and the obtained results have not led to a breakthrough. Also, vaccination with

Conjugation of Antigen to TLR Ligands

In a survey of the status of melanoma vaccines, the overall objective response rate in a series of 440 patients treated with various melanoma-specific vaccines was only 2.6% (Rosenberg et al., 2004). It was concluded that the immunotherapeutic approaches need drastic improvement. Since most peptide vaccination trials to date were carried out by injecting exact MHC class I binding peptides, often without TLR ligand, this evaluation is certainly justified. Measures for improved clinical results

Synergy between different PRR routes

A natural infection always brings forth a broad array of antigenic ligands, which can be recognized by divergent PRRs. For example, the bacterial cell wall harbors both TLR ligands, such as lipopeptides and lipoproteins, CLR ligands, such as (amino)sugars, as well as NLR ligands, such as muropeptides (MDP). Therefore, it seems plausible to combine multiple PRR ligands (PRR-Ls) in one molecule to even increase the potency of such conjugates.

References (114)

  • T.A. Kufer et al.

    Sensing of bacteria: NOD a lonely job

    Curr. Opin. Microbiol.

    (2007)
  • H.K. Lee et al.

    Double-stranded RNA-mediated TLR3 activation is enhanced by CD14

    Immunity

    (2006)
  • B. Lemaitre et al.

    The dorsoventral regulatory gene cassette spatzle/Toll/cactus controls the potent antifungal response in Drosophila adults

    Cell

    (1996)
  • Y.M. Loo et al.

    Immune signaling by RIG-I-like receptors

    Immunity

    (2011)
  • N. Lutzner et al.

    Quantifying cathepsin S activity in antigen presenting cells using a novel specific substrate

    J. Biol. Chem.

    (2008)
  • C.J. Melief et al.

    Strategies for immunotherapy of cancer

    Adv. Immunol.

    (2000)
  • I. Mellman et al.

    Dendritic cells: Specialized and regulated antigen processing machines

    Cell

    (2001)
  • E. Meylan et al.

    The RIP kinases: Crucial integrators of cellular stress

    Trends Biochem. Sci.

    (2005)
  • T.P. Monie et al.

    Activating immunity: Lessons from the TLRs and NLRs

    Trends Biochem. Sci.

    (2009)
  • M. Obert et al.

    Protection of mice against SV40 tumours by Pam3Cys, MTP-PE and Pam3Cys conjugated with the SV40 T antigen-derived peptide, K(698)-T(708)

    Vaccine

    (1998)
  • F. Osorio et al.

    Myeloid C-type lectin receptors in pathogen recognition and host defense

    Immunity

    (2011)
  • F. Ossendorp et al.

    Importance of CD4(+) T helper cell responses in tumor immunity

    Immunol. Lett.

    (2000)
  • E. Segura et al.

    Antigen presentation by dendritic cells in vivo

    Curr. Opin. Immunol.

    (2009)
  • R. Spohn et al.

    Synthetic lipopeptide adjuvants and Toll-like receptor 2—Structure-activity relationships

    Vaccine

    (2004)
  • R.M. Steinman

    Dendritic cells in vivo: A key target for a new vaccine science

    Immunity

    (2008)
  • O. Takeuchi et al.

    MDA5/RIG-I and virus recognition

    Curr. Opin. Immunol.

    (2008)
  • H. Tighe et al.

    Conjugation of immunostimulatory DNA to the short ragweed allergen amb a 1 enhances its immunogenicity and reduces its allergenicity

    J. Allergy Clin. Immunol.

    (2000)
  • A. Vambutas et al.

    Therapeutic vaccination with papillomavirus E6 and E7 long peptides results in the control of both established virus-induced lesions and latently infected sites in a pre-clinical cottontail rabbit papillomavirus model

    Vaccine

    (2005)
  • P. Ahmad-Nejad et al.

    Bacterial CpG-DNA and lipopolysaccharides activate Toll-like receptors at distinct cellular compartments

    Eur. J. Immunol.

    (2002)
  • Y. Asai et al.

    Toll-like receptor 2-mediated dendritic cell activation by a Porphyromonas gingivalis synthetic lipopeptide

    J. Med. Microbiol.

    (2007)
  • J. Asano et al.

    Nucleotide oligomerization binding domain-like receptor signaling enhances dendritic cell-mediated cross-priming in vivo

    J. Immunol.

    (2010)
  • J. Banchereau et al.

    Immunobiology of dendritic cells

    Annu. Rev. Immunol.

    (2000)
  • C.L. Baumann et al.

    CD14 is a coreceptor of Toll-like receptors 7 and 9

    J. Exp. Med.

    (2010)
  • S.R. Bennett et al.

    Induction of a CD8 + cytotoxic T lymphocyte response by cross-priming requires cognate CD4 + T cell help

    J. Exp. Med.

    (1997)
  • S.R. Bennett et al.

    Help for cytotoxic-T-cell responses is mediated by CD40 signalling

    Nature

    (1998)
  • C.E. Bryant et al.

    The molecular basis of the host response to lipopolysaccharide

    Nat. Rev. Microbiol.

    (2010)
  • C. Buonerba et al.

    Sipuleucel-T for prostate cancer: The immunotherapy era has commenced

    Expert Rev. Anticancer Ther.

    (2011)
  • A. Chaturvedi et al.

    How location governs toll-like receptor signaling

    Traffic

    (2009)
  • H.J. Cho et al.

    Immunostimulatory DNA-based vaccines induce cytotoxic lymphocyte activity by a T-helper cell-independent mechanism

    Nat. Biotechnol.

    (2000)
  • L. De Haan et al.

    Enhanced delivery of exogenous peptides into the class I antigen processing and presentation pathway

    Infect. Immun.

    (2002)
  • A. de Jong et al.

    Human papillomavirus type 16-positive cervical cancer is associated with impaired CD4 + T-cell immunity against early antigens E2 and E6

    Cancer Res.

    (2004)
  • P.J. de Vos van Steenwijk et al.

    An unexpectedly large polyclonal repertoire of HPV-specific T cells is poised for action in patients with cervical cancer

    Cancer Res.

    (2010)
  • K.M. Dennehy et al.

    Syk kinase is required for collaborative cytokine production induced through Dectin-1 and Toll-like receptors

    Eur. J. Immunol.

    (2008)
  • K. Deres et al.

    In vivo priming of virus-specific cytotoxic T lymphocytes with synthetic lipopeptide vaccine

    Nature

    (1989)
  • M.C. Feltkamp et al.

    Vaccination with cytotoxic T lymphocyte epitope-containing peptide protects against a tumor induced by human papillomavirus type 16-transformed cells

    Eur. J. Immunol.

    (1993)
  • T.W. Flinsenberg et al.

    Antigen cross-presentation: Extending recent laboratory findings to therapeutic intervention

    Clin. Exp. Immunol.

    (2011)
  • L. Franchi et al.

    Function of Nod-like receptors in microbial recognition and host defense

    Immunol. Rev.

    (2009)
  • I.H. Frazer

    Prevention of cervical cancer through papillomavirus vaccination

    Nat. Rev. Immunol.

    (2004)
  • J.H. Fritz et al.

    Synergistic stimulation of human monocytes and dendritic cells by Toll-like receptor 4 and NOD1- and NOD2-activating agonists

    Eur. J. Immunol.

    (2005)
  • N.J. Gay et al.

    Structure and function of Toll receptors and their ligands

    Annu. Rev. Biochem.

    (2007)
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