Functional Specialty of CD40 and Dendritic Cell Surface Lectins for Exogenous Antigen Presentation to CD8(+) and CD4(+) T Cells

Engineered Bacteriophage-Based In Situ Vaccine Remodels a Tumor Microenvironment and Elicits Potent Antitumor Immunity

In situ vaccines (ISVs) utilize the localized delivery of chemotherapeutic agents or radiotherapy to stimulate the release of endogenous antigens from tumors, thereby eliciting systemic and persistent immune activation. Recently, a bioinspired ISV strategy has attracted tremendous attention due to its features such as an immune adjuvant effect and genetic plasticity. M13 bacteriophages are natural nanomaterials with intrinsic immunogenicity, genetic flexibility, and cost-effectiveness for large-scale production, demonstrating the potential for application in cancer vaccines. In this study, we propose an ISV based on the engineered M13 bacteriophage targeting CD40 (M13CD40) for dendritic cell (DC)-targeted immune stimulation, named H-GM-M13CD40. We induce immunogenic cell death and release tumor antigens through local delivery of (S)-10-hydroxycamptothecin (HCPT), followed by intratumoral injection of granulocyte-macrophage colony stimulating factor (GM-CSF) and M13CD40 to enhance DC recruitment and activation. We demonstrate that this ISV strategy can result in significant accumulation and activation of DCs at the tumor site, reversing the immunosuppressive tumor microenvironment. In addition, H-GM-M13CD40 can synergize with the PD-1 blockade and induce abscopal effects in cold tumor models. Overall, our study verifies the immunogenicity of the engineered M13CD40 bacteriophage and provides a proof of concept that the engineered M13CD40 phage can function as an adjuvant for ISVs.

Next-generation CD40 agonists for cancer immunotherapy

INTRODUCTION

There is a need for new therapies that can enhance response rates and broaden the number of cancer indications where immunotherapies provide clinical benefit. CD40 targeting therapies provide an opportunity to meet this need by promoting priming of tumor-specific T cells and reverting the suppressive tumor microenvironment. This is supported by emerging clinical evidence demonstrating the benefits of immunotherapy with CD40 antibodies in combination with standard of care chemotherapy.

AREAS COVERED

This review is focused on the coming wave of next-generation CD40 agonists aiming to improve efficacy and safety, using new approaches and formats beyond monospecific antibodies. Further, the current understanding of the role of different CD40 expressing immune cell populations in the tumor microenvironment is reviewed.

EXPERT OPINION

There are multiple promising next-generation approaches beyond monospecific antibodies targeting CD40 in immuno-oncology. Enhancing efficacy is the most important driver for this development, and approaches that maximize the ability of CD40 to both remodel the tumor microenvironment and boost the anti-tumor T cell response provide great opportunities to benefit cancer patients. Enhanced understanding of the role of different CD40 expressing immune cells in the tumor microenvironment may facilitate more efficient clinical development of these compounds.

A vaccine targeting antigen-presenting cells through CD40 induces protective immunity against Nipah disease

Nipah virus (NiV) has been recently ranked by the World Health Organization as being among the top eight emerging pathogens likely to cause major epidemics, whereas no therapeutics or vaccines have yet been approved. We report a method to deliver immunogenic epitopes from NiV through the targeting of the CD40 receptor of antigen-presenting cells by fusing a selected humanized anti-CD40 monoclonal antibody to the Nipah glycoprotein with conserved NiV fusion and nucleocapsid peptides. In the African green monkey model, CD40.NiV induces specific immunoglobulin A (IgA) and IgG as well as cross-neutralizing responses against circulating NiV strains and Hendra virus and T cell responses. Challenge experiments using a NiV-B strain demonstrate the high protective efficacy of the vaccine, with all vaccinated animals surviving and showing no significant clinical signs or virus replication, suggesting that the CD40.NiV vaccine conferred sterilizing immunity. Overall, results obtained with the CD40.NiV vaccine are highly promising in terms of the breadth and efficacy against NiV.

XFab-α4-1BB/CD40L fusion protein activates dendritic cells, improves expansion of antigen-specific T cells, and exhibits antitumour efficacy in multiple solid tumour models

BACKGROUND

Additional immunotherapies are still warranted for non-responders to checkpoint inhibitors with refractory or relapsing cancers, especially for patients with "cold" tumours lacking significant immune infiltration at treatment onset. We developed XFab-α4-1BB/CD40L, a bispecific antibody targeting 4-1BB and CD40 for dendritic cell activation and priming of tumour-reactive T cells to inhibit tumours.

METHODS

XFab-α4-1BB/CD40L was developed by engineering an anti-4-1BB Fab arm into a CD40L trimer based on XFab® platform. Characterisation of the bispecific antibody was performed by cell-based reporter assays, maturation of dendritic cell assays, and mixed lymphocyte reactions. The abilities of antigen-specific T-cell expansion and antitumour efficacy were assessed in syngeneic mouse tumour models. Toxicological and pharmacodynamic profiles were investigated in non-human primates.

RESULTS

XFab-α4-1BB/CD40L demonstrated independent CD40 agonistic activity and conditional 4-1BB activity mediated by CD40 crosslinking, leading to dendritic cell maturation and T-cell proliferation in vitro. We confirmed the expansion of antigen-specific T cells in the vaccination model and potent tumour regression induced by the bispecific antibody alone or in combination with gemcitabine in vivo, concomitant with improved tumour-reactive T-cell infiltration. XFab-α4-1BB/CD40L showed no signs of liver toxicity at doses up to 51 mg/kg in a repeated-dose regimen in non-human primates.

CONCLUSIONS

XFab-α4-1BB/CD40L is capable of enhancing antitumour immunity by modulating dendritic cell and T-cell functions via targeting 4-1BB agonism to areas of CD40 expression. The focused, potent, and safe immune response induced by the bispecific antibody supports further clinical investigations for the treatment of solid tumours.

Controlling Antigen Fate in Therapeutic Cancer Vaccines by Targeting Dendritic Cell Receptors

Antigen-presenting cells (APCs) orchestrate immune responses and are therefore of interest for the targeted delivery of therapeutic vaccines. Dendritic cells (DCs) are professional APCs that excel in presentation of exogenous antigens toward CD4+ T helper cells, as well as cytotoxic CD8+ T cells. DCs are highly heterogeneous and can be divided into subpopulations that differ in abundance, function, and phenotype, such as differential expression of endocytic receptor molecules. It is firmly established that targeting antigens to DC receptors enhances the efficacy of therapeutic vaccines. While most studies emphasize the importance of targeting a specific DC subset, we argue that the differential intracellular routing downstream of the targeted receptors within the DC subset should also be considered. Here, we review the mouse and human receptors studied as target for therapeutic vaccines, focusing on antibody and ligand conjugates and how their targeting affects antigen presentation. We aim to delineate how targeting distinct receptors affects antigen presentation and vaccine efficacy, which will guide target selection for future therapeutic vaccine development.

The therapeutic potential of immunotherapy in the treatment of breast cancer: Rational strategies and recent progress

The second leading cause of cancer death in women worldwide is breast cancer (BC), and despite significant advances in BC therapies, a significant proportion of patients develop metastasis and disease recurrence. Currently used treatments, like radiotherapy, chemotherapy, and hormone replacement therapy, result in poor responses and high recurrence rates. Alternative therapies are therefore needed for this type of cancer. Cancer patients may benefit from immunotherapy, a novel treatment strategy in cancer treatment. Even though immunotherapy has been successful in many cases, some patients do not respond to the treatment or those who do respond relapse or progress. The purpose of this review is to discuss several different immunotherapy approaches approved for the treatment of BC, as well as different strategies for immunotherapy for the treatment of BC.

Recent advances in antigen targeting to antigen-presenting cells in veterinary medicine

Advances in antigen targeting in veterinary medicine have gained traction over the years as an alternative approach for diseases that remain a challenge for traditional vaccines. In addition to the nature of the immunogen, antigen-targeting success relies heavily on the chosen receptor for its direct influence on the elicited response that will ensue after antigen uptake. Different approaches using antibodies, natural or synthetic ligands, fused proteins, and DNA vaccines have been explored in various veterinary species, with pigs, cattle, sheep, and poultry as the most frequent models. Antigen-presenting cells can be targeted using a generic approach, such as broadly expressed receptors such as MHC-II, CD80/86, CD40, CD83, etc., or focused on specific cell populations such as dendritic cells or macrophages (Langerin, DC-SIGN, XCR1, DC peptides, sialoadhesin, mannose receptors, etc.) with contrasting results. Interestingly, DC peptides show high specificity to DCs, boosting activation, stimulating cellular and humoral responses, and a higher rate of clinical protection. Likewise, MHC-II targeting shows consistent results in enhancing both immune responses; an example of this strategy of targeting is the approved vaccine against the bovine viral diarrhea virus in South America. This significant milestone opens the door to continuing efforts toward antigen-targeting vaccines to benefit animal health. This review discusses the recent advances in antigen targeting to antigen-presenting cells in veterinary medicine, with a special interest in pigs, sheep, cattle, poultry, and dogs.

Nano-adjuvants and immune agonists promote antitumor immunity of peptide amphiphiles

Immunostimulatory cues play an important role in priming antitumor immunity and promoting the efficacy of subunit cancer vaccines. However, the clinical use of many immunostimulatory agents is often hampered by their inefficient in vivo delivery which may decrease immune response to the vaccination. To promote vaccine efficacy, we develop vaccine formulations which integrate three key elements: (1) a nano-adjuvant formulated by conjugating an agonistic anti-CD40 monoclonal antibody (αCD40) to the surface of a polyIC-loaded lipid nanoparticle, (2) a peptide amphiphile containing an optimized CD8⁺ T-cell epitope that derived from a melanoma antigen gp100, (3) an agonistic anti-4-1BB monoclonal antibody (α4-1BB) that boosts the efficacy of vaccinations. In a syngeneic mouse model of melanoma, the vaccine formulations enhanced innate immunity and activated multiple innate immune signaling pathways within draining lymph nodes, as well as promoted antigen-specific immune responses and reduced immunosuppression in the tumor microenvironment, leading to profound tumor growth inhibition and prolonged survival. Thus, our vaccine formulations represent an attractive strategy to stimulate antitumor immunity and control tumor progression. STATEMENT OF SIGNIFICANCE: The clinical use of many immunostimulatory agents is often hampered by their inefficient in vivo delivery which may decrease immune response to the vaccination. To promote the antitumor immunity of subunit vaccines, we develop novel vaccine formulations that integrate multifunctional modalities including (1) a nano-adjuvant containing anti-CD40 monoclonal antibody (αCD40) and TLR3 agonist which activate innate immunity through diverse signaling pathways, (2) a peptide amphiphile containing an optimized CD8⁺ T-cell epitope from tumor antigen, (3) an anti-4-1BB monoclonal antibody (α4-1BB) that boosts the efficacy of vaccinations. In this study, our vaccine formulations stimulate superior antitumor immunity and control tumor progression. The above nano-engineered platform and immunogenic biomacromolecules can be further applied to other T-cell-inducing vaccines.

Bispecific antibodies targeting CD40 and tumor-associated antigens promote cross-priming of T cells resulting in an antitumor response superior to monospecific antibodies

BACKGROUND

Indications with poor T-cell infiltration or deficiencies in T-cell priming and associated unresponsiveness to established immunotherapies represent an unmet medical need in oncology. CD40-targeting therapies designed to enhance antigen presentation, generate new tumor-specific T cells, and activate tumor-infiltrating myeloid cells to remodel the tumor microenvironment, represent a promising opportunity to meet this need. In this study, we present the first in vivo data supporting a role for tumor-associated antigen (TAA)-mediated uptake and cross-presentation of tumor antigens to enhance tumor-specific T-cell priming using CD40×TAA bispecific antibodies, a concept we named Neo-X-Prime.

METHODS

Bispecific antibodies targeting CD40 and either of two cell-surface expressed TAA, carcinoembryonic antigen-related cell adhesion molecule 5 (CEA) or epithelial cell adhesion molecule (EpCAM), were developed in a tetravalent format. TAA-conditional CD40 agonism, activation of tumor-infiltrating immune cells, antitumor efficacy and the role of delivery of tumor-derived material such as extracellular vesicles, tumor debris and exosomes by the CD40×TAA bispecific antibodies were demonstrated in vitro using primary human and murine cells and in vivo using human CD40 transgenic mice with different tumor models.

RESULTS

The results showed that the CD40×TAA bispecific antibodies induced TAA-conditional CD40 activation both in vitro and in vivo. Further, it was demonstrated in vitro that they induced clustering of tumor debris and CD40-expressing cells in a dose-dependent manner and superior T-cell priming when added to dendritic cells (DC), ovalbumin (OVA)-specific T cells and OVA-containing tumor debris or exosomes. The antitumor activity of the Neo-X-Prime bispecific antibodies was demonstrated to be significantly superior to the monospecific CD40 antibody, and the resulting T-cell dependent antitumor immunity was directed to tumor antigens other than the TAA used for targeting (EpCAM).

CONCLUSIONS

The data presented herein support the hypothesis that CD40×TAA bispecific antibodies can engage tumor-derived vesicles containing tumor neoantigens to myeloid cells such as DCs resulting in an improved DC-mediated cross-priming of tumor-specific CD8⁺ T cells. Thus, this principle may offer therapeutics strategies to enhance tumor-specific T-cell immunity and associated clinical benefit in indications characterized by poor T-cell infiltration or deficiencies in T-cell priming.

Refining the DC-targeting vaccination for preventing emerging infectious diseases

The development of safe, long-term, effective vaccines is still a challenge for many infectious diseases. Thus, the search of new vaccine strategies and production platforms that allow rapidly and effectively responding against emerging or reemerging pathogens has become a priority in the last years. Targeting the antigens directly to dendritic cells (DCs) has emerged as a new approach to enhance the immune response after vaccination. This strategy is based on the fusion of the antigens of choice to monoclonal antibodies directed against specific DC surface receptors such as CD40. Since time is essential, in silico approaches are of high interest to select the most immunogenic and conserved epitopes to improve the T- and B-cells responses. The purpose of this review is to present the advances in DC vaccination, with special focus on DC targeting vaccines and epitope mapping strategies and provide a new framework for improving vaccine responses against infectious diseases.

Chimeric Antigen by the Fusion of SARS-CoV-2 Receptor Binding Domain with the Extracellular Domain of Human CD154: A Promising Improved Vaccine Candidate

COVID-19 is a respiratory viral disease caused by a new coronavirus called SARS-CoV-2. This disease has spread rapidly worldwide with a high rate of morbidity and mortality. The receptor-binding domain (RBD) of protein spike (S) mediates the attachment of the virus to the host's cellular receptor. The RBD domain constitutes a very attractive target for subunit vaccine development due to its ability to induce a neutralizing antibody response against the virus. With the aim of boosting the immunogenicity of RBD, it was fused to the extracellular domain of CD154, an immune system modulator molecule. To obtain the chimeric protein, stable transduction of HEK-293 was carried out with recombinant lentivirus and polyclonal populations and cell clones were obtained. RBD-CD was purified from culture supernatant and further characterized by several techniques. RBD-CD immunogenicity evaluated in mice and non-human primates (NHP) indicated that recombinant protein was able to induce a specific and high IgG response after two doses. NHP sera also neutralize SARS-CoV-2 infection of Vero E6 cells. RBD-CD could improve the current vaccines against COVID-19, based in the enhancement of the host humoral and cellular response. Further experiments are necessary to confirm the utility of RBD-CD as a prophylactic vaccine and/or booster purpose.

Design, immunogenicity, and efficacy of a pan-sarbecovirus dendritic-cell targeting vaccine

BACKGROUND

There is an urgent need of a new generation of vaccine that are able to enhance protection against SARS-CoV-2 and related variants of concern (VOC) and emerging coronaviruses.

METHODS

We identified conserved T- and B-cell epitopes from Spike (S) and Nucleocapsid (N) highly homologous to 38 sarbecoviruses, including SARS-CoV-2 VOCs, to design a protein subunit vaccine targeting antigens to Dendritic Cells (DC) via CD40 surface receptor (CD40.CoV2).

FINDINGS

CD40.CoV2 immunization elicited high levels of cross-neutralizing antibodies against SARS-CoV-2, VOCs, and SARS-CoV-1 in K18-hACE2 transgenic mice, associated with viral control and survival after SARS-CoV-2 challenge. A direct comparison of CD40.CoV2 with the mRNA BNT162b2 vaccine showed that the two vaccines were equally immunogenic in mice. We demonstrated the potency of CD40.CoV2 to recall in vitro human multi-epitope, functional, and cytotoxic SARS-CoV-2 S- and N-specific T-cell responses that are unaffected by VOC mutations and cross-reactive with SARS-CoV-1 and, to a lesser extent, MERS epitopes.

INTERPRETATION

We report the immunogenicity and antiviral efficacy of the CD40.CoV2 vaccine in a preclinical model providing a framework for a pan-sarbecovirus vaccine.

FUNDINGS

This work was supported by INSERM and the Investissements d'Avenir program, Vaccine Research Institute (VRI), managed by the ANR and the CARE project funded from the Innovative Medicines Initiative 2 Joint Undertaking (JU).

Anti-CD40 Antibody Fused to CD40 Ligand Is a Superagonist Platform for Adjuvant Intrinsic DC-Targeting Vaccines

CD40 is a potent activating receptor expressed on antigen-presenting cells (APCs) of the immune system. CD40 regulates many aspects of B and T cell immunity via interaction with CD40L expressed on activated T cells. Targeting antigens to CD40 via agonistic anti-CD40 antibody fusions promotes both humoral and cellular immunity, but current anti-CD40 antibody-antigen vaccine prototypes require co-adjuvant administration for significant in vivo efficacy. This may be a consequence of dulling of anti-CD40 agonist activity via antigen fusion. We previously demonstrated that direct fusion of CD40L to anti-CD40 antibodies confers superagonist properties. Here we show that anti-CD40-CD40L-antigen fusion constructs retain strong agonist activity, particularly for activation of dendritic cells (DCs). Therefore, we tested anti-CD40-CD40L antibody fused to antigens for eliciting immune responses in vitro and in vivo. In PBMC cultures from HIV-1-infected donors, anti-CD40-CD40L fused to HIV-1 antigens preferentially expanded HIV-1-specific CD8⁺ T cells versus CD4⁺ T cells compared to analogous anti-CD40-antigen constructs. In normal donors, anti-CD40-CD40L-mediated delivery of Influenza M1 protein elicited M1-specific T cell expansion at lower doses compared to anti-CD40-mediated delivery. Also, on human myeloid-derived dendritic cells, anti-CD40-CD40L-melanoma gp100 peptide induced more sustained Class I antigen presentation compared to anti-CD40-gp100 peptide. In human CD40 transgenic mice, anti-CD40-CD40L-HIV-1 gp140 administered without adjuvant elicited superior antibody responses compared to anti-CD40-gp140 antigen without fused CD40L. In human CD40 mice, compared to the anti-CD40 vehicle, anti-CD40-CD40L delivery of Eα 52-68 peptide elicited proliferating of TCR I-Eα 52-68 CD4⁺ T cells producing cytokine IFNγ. Also, compared to controls, only anti-CD40-CD40L-Cyclin D1 vaccination of human CD40 mice reduced implanted EO771.LMB breast tumor cell growth. These data demonstrate that human CD40-CD40L antibody fused to antigens maintains highly agonistic activity and generates immune responses distinct from existing low agonist anti-CD40 targeting formats. These advantages were in vitro skewing responses towards CD8⁺ T cells, increased efficacy at low doses, and longevity of MHC Class I peptide display; and in mouse models, a more robust humoral response, more activated CD4⁺ T cells, and control of tumor growth. Thus, the anti-CD40-CD40L format offers an alternate DC-targeting platform with unique properties, including intrinsic adjuvant activity.

Cancer vaccines as a targeted immunotherapy approach for breast cancer: an update of clinical evidence

INTRODUCTION

Breast cancer (BC) is the first common neoplastic malignancy and the second leading cause of death in women worldwide. Conventional treatments for BC are often associated with severe side effects and may even lead to late recurrence. For this reason, in recent years, cancer immunotherapy (e.g., cancer vaccines), a novel approach based on the specificity and amplification of acquired immune responses, has been considered as a potential candidate in particular to treat metastatic BC.

AREAS COVERED

In this review, we summarize and discuss the recent development of therapeutic vaccines for BC, use of specific BC cellular antigens, antigen selection, and probable causes for their insufficient effectiveness.

EXPERT OPINION

Despite development of several different BC vaccines strategies including protein/peptide, dendritic cell, and genetic vaccines, until now, no BC vaccine has been approved for clinical use. Most of the current BC vaccines themselves fail to bring clinical benefit to BC patients and are applied in combination with radiotherapy, chemotherapy, or targeted therapy. It is hoped that with advances in our knowledge about tumor microenvironment and the development of novel combination strategies, the tumor immunosuppressive mechanisms can be overcome and prolonged immunologic and effective anti-tumor response can be developed in patients.

A Framework to Identify Antigen-Expanded T Cell Receptor Clusters Within Complex Repertoires

Common approaches for monitoring T cell responses are limited in their multiplexity and sensitivity. In contrast, deep sequencing of the T Cell Receptor (TCR) repertoire provides a global view that is limited only in terms of theoretical sensitivity due to the depth of available sampling; however, the assignment of antigen specificities within TCR repertoires has become a bottleneck. This study combines antigen-driven expansion, deep TCR sequencing, and a novel analysis framework to show that homologous ‘Clusters of Expanded TCRs (CETs)’ can be confidently identified without cell isolation, and assigned to antigen against a background of non-specific clones. We show that clonotypes within each CET respond to the same epitope, and that protein antigens stimulate multiple CETs reactive to constituent peptides. Finally, we demonstrate the personalized assignment of antigen-specificity to rare clones within fully-diverse uncultured repertoires. The method presented here may be used to monitor T cell responses to vaccination and immunotherapy with high fidelity.

Targeting SARS-CoV-2 receptor-binding domain to cells expressing CD40 improves protection to infection in convalescent macaques

Achieving sufficient worldwide vaccination coverage against SARS-CoV-2 will require additional approaches to currently approved viral vector and mRNA vaccines. Subunit vaccines may have distinct advantages when immunizing vulnerable individuals, children and pregnant women. Here, we present a new generation of subunit vaccines targeting viral antigens to CD40-expressing antigen-presenting cells. We demonstrate that targeting the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein to CD40 (αCD40.RBD) induces significant levels of specific T and B cells, with long-term memory phenotypes, in a humanized mouse model. Additionally, we demonstrate that a single dose of the αCD40.RBD vaccine, injected without adjuvant, is sufficient to boost a rapid increase in neutralizing antibodies in convalescent non-human primates (NHPs) exposed six months previously to SARS-CoV-2. Vaccine-elicited antibodies cross-neutralize different SARS-CoV-2 variants, including D614G, B1.1.7 and to a lesser extent B1.351. Such vaccination significantly improves protection against a new high-dose virulent challenge versus that in non-vaccinated convalescent animals.

In this study, Marlin et al. provide insights into the potential use of subunit vaccines that induce a high level of protection against SARS-CoV-2 in animal models.

Rationale and clinical development of CD40 agonistic antibodies for cancer immunotherapy

Introduction: CD40 signaling activates dendritic cells leading to improved T cell priming against tumor antigens. CD40 agonism expands the tumor-specific T cell repertoire and has the potential to increase the fraction of patients that respond to established immunotherapies.Areas covered: This article reviews current as well as emerging CD40 agonist therapies with a focus on antibody-based therapies, including next generation bispecific CD40 agonists. The scientific rationale for different design criteria, binding epitopes, and formats are discussed.Expert opinion: The ability of CD40 agonists to activate dendritic cells and enhance antigen cross-presentation to CD8⁺ T cells provides an opportunity to elevate response rates of cancer immunotherapies. While there are many challenges left to address, including optimal dose regimen, CD40 agonist profile, combination partners and indications, we are confident that CD40 agonists will play an important role in the challenging task of reprogramming the immune system to fight cancer.

TLR9- and CD40-Targeting Vaccination Promotes Human B Cell Maturation and IgG Induction via pDC-Dependent Mechanisms in Humanized Mice

Mice reconstituted with a human immune system (humanized mice) provide a robust model to study human immunology, vaccinology, and human infectious diseases. However, the development and function of B cells in humanized mice is impaired. B cells from humanized mice are immature and are impaired in IgM to IgG isotype switch in response to infection or vaccination. In the present study we report that Toll-like receptor 9 (TLR9) agonist CpG-B combined with CD40-targeting vaccination triggered human B cell immunoglobin class-switch from IgM⁺ to IgG⁺ B cells in humanized mice. Human B cells from mice vaccinated with CpG-B as adjuvant were more mature in phenotype and produced significant levels of both total IgG and antigen-specific IgG. We found that CpG-B treatment activated human pDCs (plasmacytoid dendritic cells) in vivo to induce interferon-alpha (IFN-α)expression in humanized mice. Pre-depletion of human pDC in vivo abrogated the adjuvant effect of CpG-B. Our results indicate that TLR9 and CD40-targeting vaccination triggers human B cell maturation and immunoglobulin class-switch in a pDC-dependent manner in humanized mice. The findings also shed light on induction of human IgG antibodies in humanized mouse models.

The human anti-CD40 agonist antibody mitazalimab (ADC-1013; JNJ-64457107) activates antigen-presenting cells, improves expansion of antigen-specific T cells, and enhances anti-tumor efficacy of a model cancer vaccine in vivo

Non-responders to checkpoint inhibitors generally have low tumor T cell infiltration and could benefit from immunotherapy that activates dendritic cells, with priming of tumor-reactive T cells as a result. Such therapies may be augmented by providing tumor antigen in the form of cancer vaccines. Our aim was to study the effects of mitazalimab (ADC-1013; JNJ-64457107), a human anti-CD40 agonist IgG1 antibody, on activation of antigen-presenting cells, and how this influences the priming and anti-tumor potential of antigen-specific T cells, in mice transgenic for human CD40. Mitazalimab activated splenic CD11c⁺ MHCII⁺ dendritic cells and CD19⁺ MHCII⁺ B cells within 6 h, with a return to baseline within 1 week. This was associated with a dose-dependent release of proinflammatory cytokines in the blood, including IP-10, MIP-1α and TNF-α. Mitazalimab administered at different dose regimens with ovalbumin protein showed that repeated dosing expanded ovalbumin peptide (SIINFEKL)-specific CD8⁺ T cells and increased the frequency of activated ICOS⁺ T cells and CD44^hi CD62L^- effector memory T cells in the spleen. Mitazalimab prolonged survival of mice bearing MB49 bladder carcinoma tumors and increased the frequency of activated granzyme B⁺ CD8⁺ T cells in the tumor. In the ovalbumin-transfected tumor E.G7-OVA lymphoma, mitazalimab administered with either ovalbumin protein or SIINFEKL peptide prolonged the survival of E.G7-OVA tumor-bearing mice, as prophylactic and therapeutic treatment. Thus, mitazalimab activates antigen-presenting cells, which improves expansion and activation of antigen-specific T cells and enhances the anti-tumor efficacy of a model cancer vaccine.

Cancer Vaccines: Adjuvant Potency, Importance of Age, Lifestyle, and Treatments

Although the discovery and characterization of multiple tumor antigens have sparked the development of many antigen/derived cancer vaccines, many are poorly immunogenic and thus, lack clinical efficacy. Adjuvants are therefore incorporated into vaccine formulations to trigger strong and long-lasting immune responses. Adjuvants have generally been classified into two categories: those that ‘depot’ antigens (e.g. mineral salts such as aluminum hydroxide, emulsions, liposomes) and those that act as immunostimulants (Toll Like Receptor agonists, saponins, cytokines). In addition, several novel technologies using vector-based delivery of antigens have been used. Unfortunately, the immune system declines with age, a phenomenon known as immunosenescence, and this is characterized by functional changes in both innate and adaptive cellular immunity systems as well as in lymph node architecture. While many of the immune functions decline over time, others paradoxically increase. Indeed, aging is known to be associated with a low level of chronic inflammation—inflamm-aging. Given that the median age of cancer diagnosis is 66 years and that immunotherapeutic interventions such as cancer vaccines are currently given in combination with or after other forms of treatments which themselves have immune-modulating potential such as surgery, chemotherapy and radiotherapy, the choice of adjuvants requires careful consideration in order to achieve the maximum immune response in a compromised environment. In addition, more clinical trials need to be performed to carefully assess how less conventional form of immune adjuvants, such as exercise, diet and psychological care which have all be shown to influence immune responses can be incorporated to improve the efficacy of cancer vaccines. In this review, adjuvants will be discussed with respect to the above-mentioned important elements.

Fusion of Bacterial Flagellin to a Dendritic Cell-Targeting αCD40 Antibody Construct Coupled With Viral or Leukemia-Specific Antigens Enhances Dendritic Cell Maturation and Activates Peptide-Responsive T Cells

Conventional dendritic cell (DC) vaccine strategies, in which DCs are loaded with antigens ex vivo, suffer biological issues such as impaired DC migration capacity and laborious GMP production procedures. In a promising alternative, antigens are targeted to DC-associated endocytic receptors in vivo with antibody–antigen conjugates co-administered with toll-like receptor (TLR) agonists as adjuvants. To combine the potential advantages of in vivo targeting of DCs with those of conjugated TLR agonists, we generated a multifunctional antibody construct integrating the DC-specific delivery of viral- or tumor-associated antigens and DC activation by TLR ligation in one molecule. We validated its functionality in vitro and determined if TLR ligation might improve the efficacy of such a molecule. In proof-of-principle studies, an αCD40 antibody containing a CMV pp65-derived peptide as an antigen domain (αCD40^CMV) was genetically fused to the TLR5-binding D0/D1 domain of bacterial flagellin (αCD40.Flg^CMV). The analysis of surface maturation markers on immature DCs revealed that fusion of flagellin to αCD40^CMV highly increased DC maturation (3.4-fold elevation of CD80 expression compared to αCD40^CMV alone) by specifically interacting with TLR5. Immature DCs loaded with αCD40.Flg^CMV induced significantly higher CMV_NLV-specific T cell activation and proliferation compared to αCD40^CMV in co-culture experiments with allogeneic and autologous T cells (1.8-fold increase in % IFN-γ/TNF-α⁺ CD8⁺ T cells and 3.9-fold increase in % CMV_NLV-specific dextramer⁺ CD8⁺ T cells). More importantly, we confirmed the beneficial effects of flagellin-dependent DC stimulation using a tumor-specific neoantigen as the antigen domain. Specifically, the acute myeloid leukemia (AML)-specific mutated NPM1 (mNPM1)-derived neoantigen CLAVEEVSL was delivered to DCs in the form of αCD40^mNPM1 and αCD40.Flg^mNPM1 antibody constructs, making this study the first to investigate mNPM1 in a DC vaccination context. Again, αCD40.Flg^mNPM1-loaded DCs more potently activated allogeneic mNPM1_CLA-specific T cells compared to αCD40^mNPM1. These in vitro results confirmed the functionality of our multifunctional antibody construct and demonstrated that TLR5 ligation improved the efficacy of the molecule. Future mouse studies are required to examine the T cell-activating potential of αCD40.Flg^mNPM1 after targeting of dendritic cells in vivo using AML xenograft models.

TLR-9 agonist and CD40-targeting vaccination induces HIV-1 envelope-specific B cells with a diversified immunoglobulin repertoire in humanized mice

The development of HIV-1 vaccines is challenged by the lack of relevant models to accurately induce human B- and T-cell responses in lymphoid organs. In humanized mice reconstituted with human hematopoietic stem cells (hu-mice), human B cell-development and function are impaired and cells fail to efficiently transition from IgM B cells to IgG B cells. Here, we found that CD40-targeted vaccination combined with CpG-B adjuvant overcomes the usual defect of human B-cell switch and maturation in hu-mice. We further dissected hu-B cell responses directed against the HIV-1 Env protein elicited by targeting Env gp140 clade C to the CD40 receptor of antigen-presenting cells. The anti-CD40.Env gp140 vaccine was injected with CpG-B in a homologous prime/boost regimen or as a boost of a NYVAC-KC pox vector encoding Env gp140 clade C. Both regimens elicited Env-specific IgG-switched memory hu-B cells at a greater magnitude in hu-mice primed with NYVAC-KC. Single-cell RNA-seq analysis showed gp140-specific hu-B cells to express polyclonal IgG1 and IgG3 isotypes and a broad Ig VH/VL repertoire, with predominant VH3 family gene usage. These cells exhibited a higher rate of somatic hypermutation than the non-specific IgG⁺ hu-B-cell counterpart. Both vaccine regimens induced splenic GC-like structures containing hu-B and hu-Tfh-like cells expressing PD-1 and BCL-6. We confirmed in this model that circulating ICOS⁺ memory hu-Tfh cells correlated with the magnitude of gp140-specific B-cell responses. Finally, the NYVAC-KC heterologous prime led to a more diverse clonal expansion of specific hu-B cells. Thus, this study shows that CD40-targeted vaccination induces human IgG production in hu-mice and provides insights for the development of a CD40-targeting vaccine to prevent HIV-1 infection in humans.

Mice reconstituted with human hematopoietic stem cells (hu-mice) are a powerful tool for the study of human immune function in vivo and can be useful as a pre-clinical model to rank vaccination strategies. However, in hu-mice, human B cell-development and function are impaired and cells fail to efficiently transition from IgM B cells to IgG B cells. One finding of our study is that CD40-targeted vaccination combined with CpG-B adjuvant overcomes the usual defect of human B-cell switch and maturation in hu-mouse models. We further reported that the HIV-1 envelope-specific IgG⁺ hu-B cells elicited in hu-mice by the anti-CD40.Env vaccine used more VH3 and VH4 family genes and displayed higher rates of somatic hypermutations than the non-specific IgG⁺ hu-B-cell counterpart. VH3 antibodies are essential for antiviral immunity. We also showed that monitoring ICOS⁺ circulating Tfh cells seven days after the last booster immunization is a surrogate marker for vaccine-induced HIV-1-specific B-cell responses. Overall, we report important results, both in the setting of this hu-mouse model and for a prophylactic HIV vaccine.

Correlation of tumor-infiltrating immune cells of melanoma with overall survival by immunogenomic analysis

AIMS

Different types of tumor-infiltrating immune cells not only augment but also dampen antitumor immunity in the microenvironment of melanoma. Therefore, it is critical to provide an overview of tumor-infiltrating immune cells in melanoma and explore a novel strategy for immunotherapies.

METHODS

We analyzed the immune states of different stages in melanoma patients by the immune, stromal, and estimation of stromal and immune cells in malignant tumor tissues using expression data (ESTIMATE) scores. Immune cell types were identified by the estimating relative subsets of RNA transcripts (CIBERSORTx) algorithm in 471 melanoma and 324 healthy tissues. Moreover, we performed a gene set variation analysis (GSVA) to determine the differentially regulated pathways in the tumor microenvironment.

RESULTS

In melanoma cohorts, we found that ESTIMATE and immune scores were involved in survival or tumor clinical stage. Among the 22 immune cells, CD8⁺ T cells, M2 macrophages, and regulatory T cells (Tregs) showed significant differences using the CIBERSORTx algorithm. Furthermore, GSVA identified the immune cell-related pathways; the primary immunodeficiency pathway, intestinal immune network for IgA, and TGF-β pathways were identified as participants of the crosstalk in CD8⁺ T cells, Tregs, and M2 macrophages in the melanoma microenvironment.

CONCLUSION

These results reveal the cellular and molecular characteristics of immune cells in melanoma, providing a method for selecting targets of immunotherapies and promoting the efficacy of therapies for the treatment of melanoma.

Development of CD40L-modified tumor small extracellular vesicles for effective induction of antitumor immune response

Aim: Tumor-derived small extracellular vesicles (TEVs) are considered for use in inducing tumor antigen-specific immune responses as they contain tumor antigens. The delivery of tumor antigens to the antigen presentation cells (especially dendritic cells [DCs]), and the activation of DCs are the main challenges of TEV therapy. Materials & methods: TEVs were modified with CD40 ligand (CD40L), which can target CD40 expressed on the surface of DCs and can activate them via CD40L-CD40 interactions. Results: It was found that CD40L-TEVs were efficiently taken up by DCs and also activated them. Moreover, tumor antigens were efficiently presented to the T cells by DCs treated with CD40L-TEVs. Conclusion: This study proved that CD40L-modification of TEVs will be helpful for further development of TEV-based tumor vaccination.

Vitamin D status and the immune assessment in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2DS) is characterized by a heterogeneous phenotype, including alterations in phospho-calcium metabolism and immunodeficiency. We analyzed vitamin D status and the immune assessment, focusing on T cell subpopulations and dendritic cells (DCs) in a cohort of 17 pediatric 22q11.2DS patients and 17 age-matched healthy subjects. As antigen-presenting cells, DCs are the main target of vitamin D, promoting a tolerogenic T cell response. Patients were subdivided into three groups according to the parameters of phospho-calcium metabolism and serum levels of 25OHD: normal values, vitamin D deficiency and hypoparathyroidism. Different degrees of T cell deficiency, ranging from normal to partial T cell numbers, were observed in the cohort of patients. The group with vitamin D deficiency showed a significant reduction of naive T cells and a significant increase of central memory T cells compared to controls. In this group the number of circulating DCs was significantly reduced. DC decrease affected both myeloid and plasmacytoid DC subsets (mDCs and pDCs), with the most relevant reduction involving pDCs. A direct correlation between 25OHD levels and recent thymic emigrant (RTE) and DC number was identified. Despite the limited cohort analyzed, our results show that deficiency of the pDC subset in patients with 22q11.2DS may be included among the causative factors of the progressive increase of risk of autoimmune diseases in these patients. As most patients suffer from increased susceptibility to infections and heightened prevalence of autoimmune disorders, we suggest a potential role of vitamin D supplementation in preventing autoimmune or proinflammatory diseases in 22q11.2DS.

Dendritic Cells in Anticancer Vaccination: Rationale for Ex Vivo Loading or In Vivo Targeting

Dendritic cells (DCs) have shown great potential as a component or target in the landscape of cancer immunotherapy. Different in vivo and ex vivo strategies of DC vaccine generation with different outcomes have been proposed. Numerous clinical trials have demonstrated their efficacy and safety in cancer patients. However, there is no consensus regarding which DC-based vaccine generation method is preferable. A problem of result comparison between trials in which different DC-loading or -targeting approaches have been applied remains. The employment of different DC generation and maturation methods, antigens and administration routes from trial to trial also limits the objective comparison of DC vaccines. In the present review, we discuss different methods of DC vaccine generation. We conclude that standardized trial designs, treatment settings and outcome assessment criteria will help to determine which DC vaccine generation approach should be applied in certain cancer cases. This will result in a reduction in alternatives in the selection of preferable DC-based vaccine tactics in patient. Moreover, it has become clear that the application of a DC vaccine alone is not sufficient and combination immunotherapy with recent advances, such as immune checkpoint inhibitors, should be employed to achieve a better clinical response and outcome.

MWCNT-mediated combinatorial photothermal ablation and chemo-immunotherapy strategy for the treatment of melanoma

DOX and CpG loaded MWCNT with NIR irradiation could destroy tumor cells by photothermal and chemotherapy and release tumor-associated antigens, thus generating melanoma specific immune response to achieve synergistic therapeutic effect.

Anti-HIV potency of T-cell responses elicited by dendritic cell therapeutic vaccination

Identification and characterization of CD8+ and CD4+ T-cell epitopes elicited by HIV therapeutic vaccination is key for elucidating the nature of protective cellular responses and mechanism of the immune evasion of HIV. Here, we report the characterization of HIV-specific T-cell responses in cART (combination antiretroviral therapy) treated HIV-1 infected patients after vaccination with ex vivo-generated IFNα Dendritic Cells (DCs) loaded with LIPO-5 (HIV-1 Nef 66-97, Nef 116-145, Gag 17-35, Gag 253-284 and Pol 325-355 lipopeptides). Vaccination induced and/or expanded HIV-specific CD8+ T cells producing IFNγ, perforin, granzyme A and granzyme B, and also CD4+ T cells secreting IFNγ, IL-2 and IL-13. These responses were directed against dominant and subdominant epitopes representing all vaccine regions; Gag, Pol and Nef. Interestingly, IL-2 and IL-13 produced by CD4+ T cells were negatively correlated with the peak of viral replication following analytic treatment interruption (ATI). Epitope mapping confirmed that vaccination elicited responses against predicted T-cell epitopes, but also allowed to identify a set of 8 new HIV-1 HLA-DR-restricted CD4+ T-cell epitopes. These results may help to better design future DC therapeutic vaccines and underscore the role of vaccine-elicited CD4+ T-cell responses to achieve control of HIV replication.

Intradermal vaccination prevents anti-MOG autoimmune encephalomyelitis in macaques

Background

Autoimmune demyelinating diseases (ADD) are a major cause of neurological disability due to autoreactive cellular and humoral immune responses against brain antigens. A cure for chronic ADD could be obtained by appropriate immunomodulation.

Methods

We implemented a preclinical scheme to foster immune tolerance to myelin oligodendrocyte glycoprotein (MOG), in a cynomolgus-macaque model of experimental autoimmune encephalomyelitis (EAE), in which administration of recombinant human MOG (rhMOG) elicits brain inflammation mediated by MOG-autoreactive CD4⁺ lymphocytes and anti-MOG IgG. For immunotherapy, we used a recombinant antibody (Ab) directed against the dendritic cell-asialoglycoprotein receptor (DC-ASGPR) fused either to MOG or a control antigen PSA (prostate-specific antigen).

Findings

rhMOG and the anti-DC-ASGPR-MOG were respectively detected in CD1a⁺ DCs or CD163⁺ cells in the skin of macaques. Intradermal administration of anti-DC-ASGPR-MOG, but not control anti-DC-ASGPR-PSA, was protective against EAE. The treatment prevented the CD4⁺ T cell activation and proinflammatory cytokine production observed in controls. Moreover, the administration of anti-DC-ASGPR-MOG induced MOG-specific CD4⁺CD25⁺FOXP3⁺CD39⁺ regulatory lymphocytes and favoured an upsurge in systemic TGFβ and IL-8 upon rhMOG re-administration in vivo.

Interpretation

We show that the delivery of an anti-DC-ASGPR-MOG allows antigen-specific adaptive immune modulation to prevent the breach of immune tolerance to MOG. Our findings pave the way for therapeutic vaccines for long-lasting remission to grave encephalomyelitis with identified autoantigens, such as ADD associated with anti-MOG autoantibodies.

Fund

Work supported by the French ANR (ANR-11-INBS-0008 and ANR-10-EQPX-02-01), NIH (NIH 1 R01 AI 105066), the Baylor Scott and White Healthcare System funding and Roche Research Collaborative grants.

Dendritic cells in cancer immunology and immunotherapy

Dendritic cells (DCs) are a diverse group of specialized antigen-presenting cells with key roles in the initiation and regulation of innate and adaptive immune responses. As such, there is currently much interest in modulating DC function to improve cancer immunotherapy. Many strategies have been developed to target DCs in cancer, such as the administration of antigens with immunomodulators that mobilize and activate endogenous DCs, as well as the generation of DC-based vaccines. A better understanding of the diversity and functions of DC subsets and of how these are shaped by the tumour microenvironment could lead to improved therapies for cancer. Here we will outline how different DC subsets influence immunity and tolerance in cancer settings and discuss the implications for both established cancer treatments and novel immunotherapy strategies.

DC Subsets Regulate Humoral Immune Responses by Supporting the Differentiation of Distinct Tfh Cells

To determine the contribution of skin DC subsets in the regulation of humoral immunity, we used a well-characterized antigen targeting system to limit antigen availability and presentation to certain skin-derived DC subsets. Here we show that delivery of foreign antigen to steady state Langerhans cells (LCs) and cDC1s through the same receptor (Langerin) led to, respectively, robust vs. minimal-to-null humoral immune response. LCs, unlike cDC1s, supported the formation of germinal center T follicular helper cells (GC-Tfh) antigen dose-dependently and then, likely licensed by these T cells, some of the LCs migrated to the B cell area to initiate B cell responses. Furthermore, we found that the cDC1s, probably through their superior T cell activation capacity, prevented the LCs from inducing GC-Tfh cells and humoral immune responses. We further show that targeted delivery of cytokines to DCs can be used to modulate DC-induced humoral immune responses, which has important therapeutic potential. Finally, we show that human LCs, unlike monocyte-derived DCs, can support GC Tfh generation in an in vitro autologous system; and in agreement with mouse data, we provide evidence in NHP studies that targeting LCs without adjuvants is an effective way to induce antibody responses, but does not trigger CD8⁺ T cell responses. Our findings suggest that the major limitations of some relatively ineffective vaccines currently in use or in development might be that (1) they are not formulated to specifically target a certain subset of DCs and/or (2) the antigen dose is not tailored to maximize the intrinsic/pre-programmed capabilities of the specific DC subset. This new and substantial departure from the status quo is expected to overcome problems that have hindered our ability to generate effective vaccines against some key pathogens.

HIV-1 T cell epitopes targeted to Rhesus macaque CD40 and DCIR: A comparative study of prototype dendritic cell targeting therapeutic vaccine candidates

HIV-1 infection can be controlled by anti-retroviral drug therapy, but this is a lifetime treatment and the virus remains latent and rapidly rebounds if therapy is stopped. HIV-1-infected individuals under this drug regimen have increased rates of cancers, cardiovascular diseases, and autoimmunity due to compromised immunity. A therapeutic vaccine boosting cellular immunity against HIV-1 is therefore desirable and, possibly combined with other immune modulating agents, could obviate the need for long-term drug therapies. An approach to elicit strong T cell-based immunity is to direct virus protein antigens specifically to dendritic cells (DCs), which are the key cell type for controlling immune responses. For eliciting therapeutic cellular immunity in HIV-1-infected individuals, we developed vaccines comprised of five T cell epitope-rich regions of HIV-1 Gag, Nef, and Pol (HIV5pep) fused to monoclonal antibodies that bind either, the antigen presenting cell activating receptor CD40, or the endocytic dendritic cell immunoreceptor DCIR. The study aimed to demonstrate vaccine safety, establish efficacy for broad T cell responses in both primed and naïve settings, and identify one candidate vaccine for human therapeutic development. The vaccines were administered to Rhesus macaques by intradermal injection with poly-ICLC adjuvant. The animals were either i) naïve or, ii) previously primed with modified vaccinia Ankara vector (MVA) encoding HIV-1 Gag, Pol, and Nef (MVA GagPolNef). In the MVA-primed groups, both DC-targeting vaccinations boosted HIV5pep-specific blood CD4⁺ T cells producing multiple cytokines, but did not affect the MVA-elicited CD8⁺ T cell responses. In the naive groups, both DC-targeting vaccines elicited antigen-specific polyfunctional CD4⁺ and CD8⁺ T cell responses to multiple epitopes and these responses were unchanged by a subsequent MVA GagPolNef boost. In both settings, the T cell responses elicited via the CD40-targeting vaccine were more robust and were detectable in all the animals, favoring further development of the CD40-targeting vaccine for therapeutic vaccination of HIV-1-infected individuals.

TLR3 agonist and CD40-targeting vaccination induces immune responses and reduces HIV-1 reservoirs

Activation of HIV-1 reservoirs and induction of anti-HIV-1 T cells are critical to control HIV-1 rebound after combined antiretroviral therapy (cART). Here we evaluated in humanized mice (hu-mice) with persistent HIV-1 infection the therapeutic effect of TLR3 agonist and a CD40-targeting HIV-1 vaccine, which consists of a string of 5 highly conserved CD4+ and CD8+ T cell epitope-rich regions of HIV-1 Gag, Nef, and Pol fused to the C-terminus of a recombinant anti-human CD40 antibody (αCD40.HIV5pep). We show that αCD40.HIV5pep vaccination coadministered with poly(I:C) adjuvant induced HIV-1-specific human CD8+ and CD4+ T cell responses in hu-mice. Interestingly, poly(I:C) treatment also reactivated HIV-1 reservoirs. When administrated in therapeutic settings in HIV-1-infected hu-mice under effective cART, αCD40.HIV5pep with poly(I:C) vaccination induced HIV-1-specific CD8+ T cells and reduced the level of cell-associated HIV-1 DNA (or HIV-1 reservoirs) in lymphoid tissues. Most strikingly, the vaccination significantly delayed HIV-1 rebound after cART cessation. In summary, the αCD40.HIV5pep with poly(I:C) vaccination approach both activates replication of HIV-1 reservoirs and enhances the anti-HIV-1 T cell response, leading to a reduced level of cell-associated HIV-1 DNA or reservoirs. Our proof-of-concept study has significant implication for the development of CD40-targeting HIV-1 vaccine to enhance anti-HIV-1 immunity and reduce HIV-1 reservoirs in patients with suppressive cART.

Activities of stromal and immune cells in HPV-related cancers

The immune system is composed of immune as well as non-immune cells. As this system is a well-established component of human papillomavirus- (HPV)-related carcinogenesis, high risk human papillomavirus (hrHPV) prevents its routes and mechanisms in order to cause the persistence of infection. Among these mechanisms are those originated from stromal cells, which include the cancer-associated fibroblasts (CAFs), the myeloid-derived suppressor cells (MDSCs) and the host infected cells themselves, i.e. the keratinocytes. These types of cells play central role since they modulate immune cells activities to create a prosperous milieu for cancer development, and the knowledge how such interactions occur are essential for prognostic assessment and development of preventive and therapeutic approaches. Nevertheless, the precise mechanisms are not completely understood, and this lack of knowledge precluded the development of entirely efficient immunotherapeutic strategies for HPV-associated tumors. As a result, an intense work for attaining how host immune response works, and developing of effective therapies has been applied in the last decade. Based on this, this review aims to discuss the major mechanisms of immune and non-immune cells modulated by hrHPV and the potential and existing immunotherapies involving such mechanisms in HPV-related cancers. It is noticed that the combination of immunotherapies has been demonstrated to be essential for obtaining better results, especially because the possibility of increasing the modulating capacity of the HPV-tumor microenvironment has been shown to be central in strengthening the host immune system.

Modular MLV-VLPs co-displaying ovalbumin peptides and GM-CSF effectively induce expansion of CD11b+ APC and antigen-specific T cell responses in vitro

The development of novel vaccination strategies is a persistent challenge to provide effective prophylactic treatments to encounter viral infections. In general, the physical conjugation of selected vaccine components, e.g. antigen and adjuvant, has been shown to enhance the immunogenicity and hence, can increase effectiveness of the vaccine. In our proof-of-concept study, we generated non-infectious, replication deficient Murine Leukemia Virus (MLV)-derived virus-like particles (VLPs) that physically link antigen and adjuvant in a modular fashion by co-displaying them on their surface. For this purpose, we selected the immunodominant peptides of the model antigen ovalbumin (OVA) and the cytokine granulocyte macrophage-colony stimulating factor (GM-CSF) as non-classical adjuvant. Our results show that murine GM-CSF displayed on MLV-VLPs mediates expansion and proliferation of CD11b⁺ cells within murine bone marrow and total spleen cells. Moreover, we show increased immunogenicity of modular VLPs co-displaying OVA peptides and GM-CSF by their elevated capacity to induce OVA-specific T cell-activation and -proliferation within OT-I and OT-II splenocyte cultures. These enhanced effects were not achieved by using an equimolar mixture of VLPs displaying either OVA or GM-CSF. Taken together, OVA and GM-CSF co-displaying MLV-VLPs are able to target and expand antigen presenting cells which in turn results in enhanced antigen-specific T cell activation and proliferation in vitro. These data suggest MLV-VLPs to be an attractive platform to flexibly combine antigen and adjuvant for novel modular vaccination approaches.

Improved vaccine-induced immune responses via a ROS-triggered nanoparticle-based antigen delivery system

Subunit vaccines that are designed based on recombinant antigens or peptides have shown promising potential as viable substitutes for traditional vaccines due to their better safety and specificity. However, the induction of adequate in vivo immune responses with appropriate effectiveness remains a major challenge for vaccine development. More recently, the implementation of a nanoparticle-based antigen delivery system has been considered a promising approach to improve the in vivo efficacy for subunit vaccine development. Thus, we have designed and prepared a nanoparticle-based antigen delivery system composed of three-armed PLGA, which is conjugated to PEG via the peroxalate ester bond (3s-PLGA-PO-PEG) and PEI as a cationic adjuvant (PPO NPs). It is known that during a foreign pathogen attack, NADPH, an oxidase, of the host organism is activated and generates an elevated level of reactive oxygen species, hydrogen peroxide (H2O2) primarily, as a defensive mechanism. Considering the sensitivity of the peroxalate ester bond to H2O2 and the cationic property of PEI for the induction of immune responses, this 3s-PLGA-PO-PEG/PEI antigen delivery system is expected to be both ROS responsive and facilitative in antigen uptake without severe toxicity that has been reported with cationic adjuvants. Indeed, our results demonstrated excellent loading capacity and in vitro stability of the PPO NPs encapsulated with the model antigen, ovalbumin (OVA). Co-culturing of bone marrow dendritic cells with the PPO NPs also led to enhanced dendritic cell maturation, antigen uptake, enhanced lysosomal escape, antigen cross-presentation and in vitro CD8+ T cell activation. In vivo experiments using mice further revealed that the administration of the PPO nanovaccine induced robust OVA-specific antibody production, upregulation of splenic CD4+ and CD8+ T cell proportions as well as an increase in memory T cell generation. In summary, we report here a ROS-triggered nanoparticle-based antigen delivery system that could be employed to promote the in vivo efficacy of vaccine-induced immune responses.

Development of an epitope-based HIV-1 vaccine strategy from HIV-1 lipopeptide to dendritic-based vaccines

INTRODUCTION

Development of a safe, effective and globally affordable Human Immunodeficiency Virus strain 1 (HIV-1) vaccine offers the best hope for future control of the HIV-1 pandemic. However, with the exception of the recent RV144 trial, which elicited a modest level of protection against infection, no vaccine candidate has shown efficacy in preventing HIV-1 infection or in controlling virus replication in humans. There is also a great need for a successful immunotherapeutic vaccine since combination antiretroviral therapy (cART) does not eliminate the reservoir of HIV-infected cells. But to date, no vaccine candidate has proven to significantly alter the natural history of an individual with HIV-1 infection. Areas covered: For over 25 years, the ANRS (France Recherche Nord&Sud Sida-HIV hépatites) has been committed to an original program combining basic science and clinical research developing an epitope-based vaccine strategy to induce a multiepitopic cellular response against HIV-1. This review describes the evolution of concepts, based on strategies using HIV-1 lipopeptides towards the use of dendritic cell (DC) manipulation. Expert commentary: Understanding the crucial role of DCs in immune responses allowed moving from the non-specific administration of HIV-1 sequences with lipopeptides to DC-based vaccines. These DC-targeting strategies should improve HIV-1 vaccine efficacy.

Dendritic cells as cancer therapeutics

The ability of immune therapies to control cancer has recently generated intense interest. This therapeutic outcome is reliant on T cell recognition of tumour cells. The natural function of dendritic cells (DC) is to generate adaptive responses, by presenting antigen to T cells, hence they are a logical target to generate specific anti-tumour immunity. Our understanding of the biology of DC is expanding, and they are now known to be a family of related subsets with variable features and function. Most clinical experience to date with DC vaccination has been using monocyte-derived DC vaccines. There is now growing experience with alternative blood-derived DC derived vaccines, as well as with multiple forms of tumour antigen and its loading, a wide range of adjuvants and different modes of vaccine delivery. Key insights from pre-clinical studies, and lessons learned from early clinical testing drive progress towards improved vaccines. The potential to fortify responses with other modalities of immunotherapy makes clinically effective "second generation" DC vaccination strategies a priority for cancer immune therapists.

Nanoparticles: augmenting tumor antigen presentation for vaccine and immunotherapy treatments of cancer

The major goal of immunity is maintaining host survival. Toward this, immune cells recognize and eliminate targets that pose a danger. Primarily, these are external invaders (pathogens) and internal invaders (cancers). Their recognition relies on distinguishing foreign components (antigens) from self-antigens. Since cancer cells are the host's own cells that are harmfully altered, they are difficult to distinguish from normal self. Furthermore, the antigens least resembling the host are often sequestered in parts of the tumor least accessible to immune responses. Therefore, to sufficiently boost immunity, these tumor antigens must be exposed to the immune system. Toward this, nanoparticles provide an innovating means of tumor antigen presentation and are destined to become an integral part of cancer immunotherapy.

Dendritic cell analysis in primary immunodeficiency

Purpose of review

Dendritic cells are specialized antigen-presenting cells which link innate and adaptive immunity, through recognition and presentation of antigen to T cells. Although the importance of dendritic cells has been demonstrated in many animal models, their contribution to human immunity remains relatively unexplored in vivo.

Given their central role in infection, autoimmunity, and malignancy, dendritic cell deficiency or dysfunction would be expected to have clinical consequences.

Recent findings

Human dendritic cell deficiency disorders, related to GATA binding protein 2 (GATA2) and interferon regulatory factor 8 (IRF8) mutations, have highlighted the importance of dendritic cells and monocytes in primary immunodeficiency diseases and begun to shed light on their nonredundant roles in host defense and immune regulation in vivo. The contribution of dendritic cell and monocyte dysfunction to the pathogenesis of primary immunodeficiency disease phenotypes is becoming increasingly apparent. However, dendritic cell analysis is not yet a routine part of primary immunodeficiency disease workup.

Summary

Widespread uptake of dendritic cell/monocyte screening in clinical practice will facilitate the discovery of novel dendritic cell and monocyte disorders as well as advancing our understanding of human dendritic cell biology in health and disease.

Targeting interferon-alpha to dendritic cells enhances a CD8+ T cell response to a human CD40-targeted cancer vaccine

Targeting antigens to antigen presenting cells (APC) enhances the potency of recombinant protein CD8⁺ T cell vaccines. Recent comparisons of recombinant protein-based dendritic cell (DC) targeting vaccines revealed differences in cross-presentation and identified CD40 as a potent human DC receptor target for antigen cross-presentation. Contrary to in vitro-derived monocyte (mo)DC, we found that interferon-alpha (IFNα) stimulation of human blood-derived DC was necessary for an antigen-specific IFNγ CD8⁺ T cell response to a CD40 targeted cancer vaccine. Importantly, targeting an adjuvant in the form of IFNα to DC increased their potency to elicit antigen-specific production of IFNγ by CD8⁺ T cells. Thus, we introduce the concept of DC adjuvant targeting to enhance the potency of vaccination.

Superiority in Rhesus Macaques of Targeting HIV-1 Env gp140 to CD40 versus LOX-1 in Combination with Replication-Competent NYVAC-KC for Induction of Env-Specific Antibody and T Cell Responses

We compared the HIV-1-specific immune responses generated by targeting HIV-1 envelope protein (Env gp140) to either CD40 or LOX-1, two endocytic receptors on dendritic cells (DCs), in rhesus macaques primed with a poxvirus vector (NYVAC-KC) expressing Env gp140. The DC-targeting vaccines, humanized recombinant monoclonal antibodies fused to Env gp140, were administered as a boost with poly-ICLC adjuvant either alone or coadministered with the NYVAC-KC vector. All the DC-targeting vaccine administrations with poly-ICLC increased the low-level serum anti-Env IgG responses elicited by NYVAC-KC priming significantly more (up to a P value of 0.01) than in a group without poly-ICLC. The responses were robust and cross-reactive and contained antibodies specific to multiple epitopes within gp140, including the C1, C2, V1, V2, and V3, C4, C5, and gp41 immunodominant regions. The DC-targeting vaccines also elicited modest serum Env-specific IgA responses. All groups gave serum neutralization activity limited to tier 1 viruses and antibody-dependent cytotoxicity responses (ADCC) after DC-targeting boosts. Furthermore, CD4⁺ and CD8⁺ T cell responses specific to multiple Env epitopes were strongly boosted by the DC-targeting vaccines plus poly-ICLC. Together, these results indicate that prime-boost immunization via NYVAC-KC and either anti-CD40.Env gp140/poly-ICLC or anti-LOX-1.Env gp140/poly-ICLC induced balanced antibody and T cell responses against HIV-1 Env. Coadministration of NYVAC-KC with the DC-targeting vaccines increased T cell responses but had minimal effects on antibody responses except for suppressing serum IgA responses. Overall, targeting Env to CD40 gave more robust T cell and serum antibody responses with broader epitope representation and greater durability than with LOX-1.IMPORTANCE An effective vaccine to prevent HIV-1 infection does not yet exist. An approach to elicit strong protective antibody development is to direct virus protein antigens specifically to dendritic cells, which are now known to be the key cell type for controlling immunity. In this study, we have tested in nonhuman primates two prototype vaccines engineered to direct the HIV-1 coat protein Env to dendritic cells. These vaccines bind to either CD40 or LOX-1, two dendritic cell surface receptors with different functions and tissue distributions. We tested the vaccines described above in combination with attenuated virus vectors that express Env. Both vaccines, but especially that delivered via CD40, raised robust immunity against HIV-1 as measured by monitoring potentially protective antibody and T cell responses in the blood. The safety and efficacy of the CD40-targeted vaccine justify further development for future human clinical trials.

Dendritic cell targeting vaccine for HPV-associated cancer

Dendritic cells (DCs) are major antigen presenting cells that can efficiently prime and activate cellular immune responses. Delivering antigens to in vivo DCs has thus been considered as a promising strategy that could allow us to mount T cell-mediated therapeutic immunity against cancers in patients. Successful development of such types of cancer vaccines that can target in vivo DCs, however, requires a series of outstanding questions that need to be addressed. These include the proper selection of which DC surface receptors, specific DC subsets and DC activators that can further enhance the efficacy of vaccines by promoting effector T cell infiltration and retention in tumors and their actions against tumors. Supplementing these areas of research with additional strategies that can counteract tumor immune evasion mechanisms is also expected to enhance the efficacy of such therapeutic vaccines against cancers. After more than a decade of study, we have concluded that antigen targeting to DCs via CD40 to evoke cellular responses is more efficient than targeting antigens to the same types of DCs via eleven other DC surface receptors tested. In recent work, we have further demonstrated that a prototype vaccine (anti-CD40-HPV16.E6/7, a recombinant fusion protein of anti-human CD40 and HPV16.E6/7 protein) for HPV16-associated cancers can efficiently activate HPV16.E6/7-specific T cells, particularly CD8+ T cells, from the blood of HPV16+ head-and-neck cancer patients. Moreover, anti-CD40-HPV16.E6/7 plus poly(I:C) can mount potent therapeutic immunity against TC-1 tumor expressing HPV16.E6/7 protein in human CD40 transgenic mice. In this manuscript, we thus highlight our recent findings for the development of novel CD40 targeting immunotherapeutic vaccines for HPV16-associated malignancies. In addition, we further discuss several of key questions that still remain to be addressed for enhancing therapeutic immunity elicited by our prototype vaccine against HPV16-associated malignancies.

Therapeutic HPV Cancer Vaccine Targeted to CD40 Elicits Effective CD8+ T-cell Immunity

Human papillomavirus (HPV), particularly HPV16 and HPV18, can cause cancers in diverse anatomical sites, including the anogenital and oropharyngeal (throat) regions. Therefore, development of safe and clinically effective therapeutic vaccines is an important goal. Herein, we show that a recombinant fusion protein of a humanized antibody to CD40 fused to HPV16.E6/7 (αCD40-HPV16.E6/7) can evoke HPV16.E6/7-specific CD8⁺ and CD4⁺ T-cell responses in head-and-neck cancer patients in vitro and in human CD40 transgenic (hCD40Tg) mice in vivo The combination of αCD40-HPV16.E6/7 and poly(I:C) efficiently primed HPV16.E6/7-specific T cells, particularly CD8⁺ T cells, in hCD40Tg mice. Inclusion of montanide enhanced HPV16.E6/7-specific CD4⁺, but not CD8⁺, T-cell responses. Poly(I:C) plus αCD40-HPV16.E6/7 was sufficient to mount both preventative and therapeutic immunity against TC-1 tumors in hCD40Tg mice, significantly increasing the frequency of HPV16-specific CD8⁺ CTLs in the tumors, but not in peripheral blood. In line with this, tumor volume inversely correlated with the frequency of HPV16.E6/7-specific CD8⁺ T cells in tumors, but not in blood. These data suggest that CD40-targeting vaccines for HPV-associated malignancies can provide a highly immunogenic platform with a strong likelihood of clinical benefit. Data from this study offer strong support for the development of CD40-targeting vaccines for other cancers in the future. Cancer Immunol Res; 4(10); 823-34. ©2016 AACR.

Synthesis and immunostimulatory activity of substituted TLR7 agonists

Fifteen new substituted adenines were synthesized as potential TLR7 agonists. These compounds, along with 9 previously reported compounds, were analyzed for TLR7 activity and for the selective stimulation of B cell proliferation. Several functionalized derivatives exhibit significant activity, suggesting their potential for use as vaccine adjuvants.