Cancer Cells Promote Immune Regulatory Function of Macrophages by Upregulating Scavenger Receptor MARCO Expression

Expression of macrophage receptor with collagenous structure (MARCO) by tumor-associated macrophages is associated with poor prognosis of multiple types of cancer. In this article, we report that cancer cells (e.g., breast cancer and glioblastoma cell lines) can upregulate surface MARCO expression on human macrophages not only via IL-6-induced STAT3 activation but also via sphingosine-1-phosphate receptor (S1PR)-mediated IL-6 and IL-10 expression followed by STAT3 activation. We further found that MARCO ligation induces activation of the MEK/ERK/p90RSK/CREB signaling cascade, leading to IL-10 expression followed by STAT3-dependent PD-L1 upregulation. Such MARCO-induced macrophage polarization is accompanied by increased expression of PPARG, IRF4, IDO1, CCL17, and CCL22. Ligation of surface MARCO can thus result in decreased T cell responses mainly by reduction of their proliferation. Taken together, cancer cell-induced MARCO expression and its intrinsic regulatory function within macrophages are, to our knowledge, new aspects of cancer immune evasion mechanisms that need to be further studied in the future.

Antibody-Mediated Targeting of a Hybrid Insulin Peptide Toward Neonatal Thymic Langerin-Positive Cells Enhances T-Cell Central Tolerance and Delays Autoimmune Diabetes

Thymic presentation of self-antigens is critical for establishing a functional yet self-tolerant T-cell population. Hybrid peptides formed through transpeptidation within pancreatic β-cell lysosomes have been proposed as a new class of autoantigens in type 1 diabetes (T1D). While the production of hybrid peptides in the thymus has not been explored, due to the nature of their generation, it is thought to be highly unlikely. Therefore, hybrid peptide-reactive thymocytes may preferentially escape thymic selection and contribute significantly to T1D progression. Using an antibody-peptide conjugation system, we targeted the hybrid insulin peptide (HIP) 2.5HIP toward thymic resident Langerin-positive dendritic cells to enhance thymic presentation during the early neonatal period. Our results indicated that anti-Langerin-2.5HIP delivery can enhance T-cell central tolerance toward cognate thymocytes in NOD.BDC2.5 mice. Strikingly, a single dose treatment with anti-Langerin-2.5HIP during the neonatal period delayed diabetes onset in NOD mice, indicating the potential of antibody-mediated delivery of autoimmune neoantigens during early stages of life as a therapeutic option in the prevention of autoimmune diseases.

Modelling the response to vaccine in non-human primates to define SARS-CoV-2 mechanistic correlates of protection

The definition of correlates of protection is critical for the development of next-generation SARS-CoV-2 vaccine platforms. Here, we propose a model-based approach for identifying mechanistic correlates of protection based on mathematical modelling of viral dynamics and data mining of immunological markers. The application to three different studies in non-human primates evaluating SARS-CoV-2 vaccines based on CD40-targeting, two-component spike nanoparticle and mRNA 1273 identifies and quantifies two main mechanisms that are a decrease of rate of cell infection and an increase in clearance of infected cells. Inhibition of RBD binding to ACE2 appears to be a robust mechanistic correlate of protection across the three vaccine platforms although not capturing the whole biological vaccine effect. The model shows that RBD/ACE2 binding inhibition represents a strong mechanism of protection which required significant reduction in blocking potency to effectively compromise the control of viral replication.

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.

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.

Anti-CD40 Antibodies Fused to CD40 Ligand Have Superagonist Properties

CD40 is a potent activating receptor within the TNFR family expressed on APCs of the immune system, and it regulates many aspects of B and T cell immunity via interaction with CD40 ligand (CD40L; CD154) expressed on the surface of activated T cells. Soluble CD40L and agonistic mAbs directed to CD40 are being explored as adjuvants in therapeutic or vaccination settings. Some anti-CD40 Abs can synergize with soluble monomeric CD40L. We show that direct fusion of CD40L to certain agonistic anti-CD40 Abs confers superagonist properties, reducing the dose required for efficacy, notably greatly increasing total cytokine secretion by human dendritic cells. The tetravalent configuration of anti-CD40-CD40L Abs promotes CD40 cell surface clustering and internalization and is the likely mechanism of increased receptor activation. CD40L fused to either the L or H chain C termini, with or without flexible linkers, were all superagonists with greater potency than CD40L trimer. The increased anti-CD40-CD40L Ab potency was independent of higher order aggregation. Moreover, the anti-CD40-CD40L Ab showed higher potency in vivo in human CD40 transgenic mice compared with the parental anti-CD40 Ab. To broaden the concept of fusing agonistic Ab to natural ligand, we fused OX40L to an agonistic OX40 Ab, and this resulted in dramatically increased efficacy for proliferation and cytokine production of activated human CD4⁺ T cells as well as releasing the Ab from dependency on cross-linking. This work shows that directly fusing antireceptor Abs to ligand is a useful strategy to dramatically increase agonist potency.

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.

Contribution of a Hybrid Insulin Peptide-reactive T cell to Diabetes progression in the NOD mouse

Type 1 Diabetes (T1D) is a T cell-mediated autoimmune disease characterized by the immune destruction of pancreatic β cells. The search for natural equivalents to the mimetopes that can stimulate diabetogenic T cell clones from the Non-Obese Diabetic (NOD) mouse model of T1D led to the realization that hybrid peptides (HP) formed by the joining of β cell granule protein-derived peptide fragments are highly stimulatory to some clones. These hybrid peptides were later identified in vivo and proposed as a new class of post-translationally modified autoantigens mediating this disease. Recent data suggest high concentrations of these proteins in β cell lysosomes during granule turnover can lead to the hybridization of peptide fragments which may then be presented on MHC molecules. In the thymus, medullary thymic epithelial cells (mTECs) mediate T cell tolerance through promiscuous gene expression, but may not mediate HP-reactive T cell tolerance. We hypothesize that HP-reactive T cells preferentially escape the thymus and contribute significantly to T1D progression. We attempted to enhance T cell central tolerance to 2.5HIP, a hybrid insulin peptide formed from Proinsulin and Chromogranin A, the only two antigens known to be critical for T1D progression in the NOD mice, to better understand its impact on T1D incidence. Using an antibody-peptide conjugation system, we targeted 2.5HIP to a subset of thymic resident DCs to enhance presentation of 2.5HIP in early neonatal thymus. In neonatal BDC2.5 TCR-transgenic mice we found that a single dose of antibody-2.5HIP enhanced antigen-specific thymocyte apoptosis and regulatory T cell development. Importantly, a single dose in wild-type neonates resulted in a significant delay of diabetes onset.

GC-Tfh cell induction by Langerhans cells in steady-state is antigen-dose dependent and IL-6 independent

We previously compared the contributions of different skin dendritic cell subsets in the induction of humoral immune responses. We found that antigen delivery without adjuvants to Langerhans cells (LCs) through the c-type lectin receptor Langerin, unlike cDC1, induces germinal center T follicular helper cells (GC-Tfhs), GC B cells, and high antibody titers.

We also showed that targeting LCs with higher antigen dose induced significantly lower B cell responses and antibody titers. To better understand the role of antigen dose in this response, we assessed the T cell responses following targeting of LCs with different amounts of antigen. In accordance with the B cell responses, we found that GC-Tfh cell formation was also antigen dose-dependent. Using two-complementary approaches targeting IL-6-deficient LCs and targeting LCs in mice treated with neutralizing anti-IL-6 antibody, we showed that LCs induced GC-Tfh cells’ formation is an IL-6 independent fashion.

In summary, this study shows that targeting LCs at steady-state induces the formation of GC-Tfh cells through an antigen-dose dependent and IL-6 independent mechanism.

Screening for SARS-CoV-2 via PCR and serological testing in asymptomatic healthcare workers

The prevalence and seroconversion rate of SARS-CoV-2 infection among asymptomatic health care workers in the US is unclear. Our study utilized real-time polymerase chain reaction (RT-PCR) SARS-CoV-2 testing and serological evaluation to detect IgG antibodies specific to SARS-CoV-2 antigens in asymptomatic health care workers. A total of 197 subjects with a mean age of 35 years were recruited into the study. While most (67%) reported prolonged contact with known COVID-19 patients, only 8 (4.2%) tested positive on RT-PCR and 23 (11.7%) had detectable levels of IgG antibody to SARS-CoV-2. Out of 19 subjects with detectable IgG antibody at week 1, 11 (57.9%) lost their antibody response by week 3. No statistically significant difference was found in baseline characteristics or exposure status between subjects with positive and negative results on RT-PCR or antibody positivity. In conclusion, we found a low incidence of PCR positivity for SARS-CoV-2 in a high-risk group. This likely demonstrates the effectiveness of proper personal protective equipment use and low transmission risk in health care settings. The detectable IgG antibody titer was low, and a significant portion of subjects lost their antibody response on repeat testing. This may mean that antibody response in asymptomatic patients is categorically different than in symptomatic hospitalized patients with COVID-19.

Dendritic cell targeting anti-CD40 antibody-CD40L-HIV-1 vaccines are adjuvant intrinsic

Soluble CD40L and agonistic anti-CD40 monoclonal antibody are adjuvants used in vaccination settings. Vaccines based on anti-CD40 antibodies fused to HIV-1 antigens are in clinical development. Studies with current anti-CD40-based dendritic cell (DC) targeting vaccines show that co-administration of an adjuvant is needed for maximal immune responses. We show that by fusing CD40L to CD40-targeting antibodies, activation of DCs concomitant with antigen uptake and processing is maximized, and this provides a context CD40-targeting vaccines with intrinsic adjuvant activity. Direct fusion of CD40L to L or H chain C-termini results in CD40 agonists with ‘superagonist’ properties. Especially on DCs, both potency and efficacy for induction of cytokine secretion and activation markers is greatly enhanced compared to known strong agonists like Pfizer’s anti-CD40 CP-870-89 antibody. This potency was maintained by anti-CD40-CD40L constructs fused to HIV-1 antigens from Gag, Nef, and Pol regions (HIV5pep). Anti-CD40-CD40L-HIV5pep preferentially expanded CD8+ T cells from HIV-1+ donor PBMCs compared to the same antibody-antigen fusions without attached CD40L. Anti-CD40-CD40L-TEα and anti-CD40-TEα both evoked robust proliferation of TEα-specific CD4+ T cells in human CD40 transgenic mice, but only anti-CD40-CD40L-TEα vaccine elicited TEα-specific CD4+ T cells producing IFNγ. Also, anti-CD40-CD40L-Env gp140 vaccine without adjuvant in human CD40 transgenic mice elicited stronger anti-Env gp140 antibody responses than anti-CD40-Env gp140 vaccine. Thus superagonist anti-CD40 antibodies directly fused to the natural ligand show great advantage in inducing immune responses without the use of an extrinsic adjuvant.

Abstract P5-04-10: Immune and transcriptional signatures of dendritic cell (DC) vaccination combined with chemotherapy in locally advanced, triple-negative breast cancer (TNBC) patients

Women with triple-negative breast cancer (TNBC) have an increased pathologic complete response rate (pCR; residual disease after neoadjuvant chemotherapy) as compared to women with non-TNBC, and those with pCR have a 90% disease-free survival. However, women with TNBC who do not achieve a pCR have an increased risk of recurrence, decreased overall survival, and post-recurrence survival as compared to women with non-TNBC who do not achieve a pCR. A high priority for clinical research is therefore to increase the pCR rate in breast and axilla with preoperative therapy, as therapeutic options for patients who do not have a pCR are limited. Immunotherapy is an attractive strategy as human BCs can be immunogenic and enhancing the immune effector function may augment the cytotoxic effects of standard therapies. Immunity against tumor antigens can be boosted in cancer patients by vaccination with ex vivo-generated tumor antigen-loaded DCs. Here, we report the extended analysis of a clinical trial on 10 TNBC pts assessing the feasibility of combining cyclin B1/WT1/CEF (antigen)-loaded DC vaccination with preoperative chemotherapy in patients with locally advanced TNBC. Combination of preoperative chemotherapy and intratumoral and subcutaneous autologous DC vaccination led to 70% of combined rate of pCR and residual cancer burden 1 (RCB1). To assess expansion of antigen-specific T cell responses, IFN-g-ELISpot was carried out with PBMCs from baseline (BL) and several time points during vaccine treatment that were cultured with control peptides or with peptide libraries covering vaccine antigens. The expansion of antigen-specific immune responses could be detected at various time points post treatment. Transciptional profiling on blood (Nanostring) and tumors (RNAseq) revealed profound changes in immune transcription signatures. T cell and DC signatures in blood and T cell, inflammation, cytotoxic and cell cycle signatures in pre-chemotherapy breast cancer biopsies were linked with pathological responses in definitive surgery specimens. Taken together, differential gene and immunologic signatures of the pre-treatment breast cancer biopsies distinguish pts who have a pCR vs no pCR and can identify potential therapeutic targets for pts with TNBC.

Citation Format: Te-Chia Wu, Joyce O’Shaughnessy, Lee K. Roberts, Jennifer L. Smith, Susan B. Burkeholder, Jennifer Finholt, Jessica Tarnowski, Tuoc Dao, Jeffrey Lamont, Sandra M. Zurawski, Phuong Nguyen, Yuanyuan Wang, Kyung In Kim, Derek Blankenship, Jacob Turner, Xuan Wang, Florentina Marches, Maren K. Levin, Michael Grant, Gerard Zurawski, Virginia Pascual, Jacques Banchereau, Karolina Palucka. Immune and transcriptional signatures of dendritic cell (DC) vaccination combined with chemotherapy in locally advanced, triple-negative breast cancer (TNBC) patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-04-10.

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.

Novel cyclin D1-based DC vaccine inhibits TNBC tumor growth

Triple-negative breast cancer (TNBC) is an aggressive histological subtype with limited treatment options and very poor prognosis after the failure of standard chemotherapeutic regimens. Immunotherapies activating the patient’s own immune system to fight various types of cancer are emerging as a powerful alternative and complement to standard chemotherapy and radiation therapy. Since dendritic cells (DCs) regulate every aspect of adaptive immune responses, we sought to generate DC vaccines that target TNBC. Recently, we found that targeting CD40 on DCs induced superior anti-tumor cytotoxic T cell responses compared to targeting other DC receptors. In the quest to find tumor-specific (overexpressed) antigens, we recently identified the cell cycle protein, cyclin D1, as a potential antigen for a DC-targeting-based vaccine against TNBC. Cyclin D1 is overexpressed in many tumors, including TNBC, and we found that cyclin D1-specific effector T cells could be readily expanded from the blood of TNBC patients or normal human donors. To test whether targeting cyclin D1 to DCs through CD40 can control tumor growth, we implemented a novel TNBC mouse model in our laboratory. This consists of a transgenic mouse expressing human CD40 in a C57BL/6 background and a recently characterized syngeneic EO771-LMB metastatic breast cancer cell line with TNBC characteristics. We found that in a therapeutic setting, targeting cyclin D1 (highly conserved between mice and humans) to DCs through CD40 led to significant inhibition of tumor growth in mice.

Thus, these data suggest that cyclin D1-based DC-targeting vaccines could be a novel immunotherapeutic candidate for TNBC.

Thymic development of regulatory T cells by dendritic cells presenting modified peripheral beta cell antigens

Type I Diabetes (T1D) is a T cell-mediated autoimmune disease that destroys insulin producing β cells found within the pancreatic islets of Langerhans. Insulin and Chromogranin A (ChgA) are the only currently known β cell antigens (βAg) necessary to initiate autoimmune diabetes in the non-obese diabetic (NOD) mice; however, expression of ChgA within medullary thymic epithelial cells (mTECs) has not yet been detected. Therefore, tolerance to ChgA may be due in part to peripheral dendritic cells (DCs) presenting ChgA to developing thymocytes and naïve T cells. For example, post-translational modification (PTM) of ChgA by fusion with an insulin peptide increases epitope immunogenicity by forming the neo-antigen, insulin-ChgA fusion peptide (2.5HIP). Pathogenic T cells that are specific for 2.5HIP, which is uniquely expressed in the pancreas, may escape thymic selection due to immunologic ignorance. The relative contribution of thymic and peripheral derived Ag in the selection of βAg specific CD4+ T cells and regulatory T cells (Tregs) remains unclear. To test the role of peripheral Ag exposure on thymic development of βAg specific Tregs, we generated a 50:50 mixed bone marrow chimera using NOD WT (CD45.2 × CD45.1) and BDC2.5 TCR Tg (CD45.1) bone marrow to study the role of peripheral DCs (CD45.2) on developing ChgA T cells. Next, we targeted thymic Langerin+ DCs with anti-Langerin linked to ChgA peptides in BDC2.5 TCR Tg mice. In both experiments, we found robust increase in the ratio and number of ChgA specific Tregs in the presence of the 2.5HIP, in adult and neonatal mice. The results suggest thymic exposure to PTM peptides by DCs enhances β cell specific Treg development and may alter T1D pathogenesis.

DC subsets are functionally specialized to induce GC-dependent or -independent humoral immune responses

Our knowledge of humoral immunity mainly comes from experimental vaccine models that use high antigen doses injected into the periphery in combination with adjuvants. This allows extended exposure to antigen/adjuvant by all of the immune cells. Thus, the contribution of a specific immune cell to humoral immune responses cannot be easily determined. To better understand the roles of different dendritic cell (DC) subsets in regulating humoral immunity, we developed a system to limit antigen availability and presentation to certain skin DC subsets. We found that antigen delivery without adjuvants to Langerhans cells (LCs) through the c-type lectin Langerin led to higher antibody titers and affinity, involved GC formation and was dependent on antigen dose and CD40 and IL-10 signaling, unlike the response initiated by CD103+DCs that produced lower antibody titers in a GC-independent manner and was characterized by long-lived PC formation. Interestingly, co-delivery of IFNa or poly-IC enabled CD103+DCs to drive GC-dependent humoral immune responses. Surprisingly, when both DC subsets had the antigen, the humoral immune response was like the one induced by the CD103+DCs alone but was dominated by memory/PB formation. Consistent with the B cell responses, the LC-induced Tfh cells were CD69+ S1PR1low and efficiently migrated to the B cell area, while the ones induced by the CD103+DCs were CD69− S1PR1high and localized mainly to the T cell zone. CD69 expression on Th cells inversely correlated with the antigen presentation capacity of the DCs. LCs, unlike CD103+DCs, migrated into the B cell area including B cell follicles and GCs.

Thus, pre-programmed DC-intrinsic features allow DC subsets to induce distinct B cell responses.

Abstract P3-05-01: Immune and transcriptional signatures of dendritic dell (DC) vaccination combined with chemotherapy in locally advanced, triple-negative breast cancer (TNBC) patients

BACKGROUND: Women with TNBC who do not achieve a pathologic complete response (pCR) with preoperative (preop) chemotherapy have a high risk of recurrence and death from BC. Immunotherapy is an attractive strategy as human BCs can be immunogenic, and enhancing the immune effector function may augment the cytotoxic effects of standard therapies.

CLINICAL TRIAL: Following IRB-approved informed consent, 10 pts with locally advanced TNBC received preop dose-dense doxorubicin/cyclophosphamide (AC) followed by paclitaxel and carboplatin (TCb) chemotherapy, combined with antigen-loaded (TNBC antigens: Cyclin B1, WT1, and control viral antigens: CEF) autologous monocyte-derived DC vaccinations administered intratumorally and subcutaneously. DCs were generated with GM-CSF and type I interferon, loaded with antigen in the form of long peptides and activated with innate ligands (LPS and Clo75) and CD40 ligand. Vaccines were given at 4 time points prior to definitive surgery, and 3 times post-surgery, pre- and post-radiation therapy (RT). Safety was the primary study endpoint, and pCR rate in breast and axilla was a secondary endpoint. Correlative studies included assessment of immune response via ELISpot and transcriptional profiling of blood samples collected over time.

RESULTS: All pts received the 4 vaccines during preop chemotherapy, and 7/10 received all 7 vaccines. At the time of definitive surgery, 4 pts achieved a pCR, 3 pts had macroscopic residual disease in the breast and axillary lymph nodes, and 3 pts had residual cancer burden scores of 1. As of June 1, 2017, all pts have been in follow-up for at least 1 year s/p completion of all vaccines, and 7/10 patients have no evidence of disease.

To assess immune signatures with IFN-γ-ELISpot, PBMCs from baseline (BL) and several time points during vaccine treatment were cultured with control peptides or with peptide libraries covering vaccine antigens. Using a linear mixed model to account for repeated and missing observations we found statistically significant (α = 0.05) increases in Cyclin B1, WT1, and CEF ELISpots in at least 1 time point post-DC vaccination and in follow-up. Compared to BL, Cyclin B1 and WT1 increased at 3 day pre-RT in 8/10 and 7/10 pts, respectively. To assess transcriptional signatures, a linear mixed model was utilized to determine statistically significant differences in fold-change over time compared to the BL and healthy controls. Modular analysis of differentially expressed transcripts at BL revealed downregulation of transcripts related to the monocyte lineage in 7/10 pts. Longitudinal analysis revealed profound transcriptional changes during AC with downregulation of lymphocyte modules and upregulation of innate and inflammation modules. While the latter ones have normalized during TCb and follow-up, T cell module remained substantially downregulated throughout treatment and follow-up.

CONCLUSIONS: Combination of preop chemotherapy and intratumoral and subcutaneous autologous DC vaccination is safe in locally advanced TNBC pts and is linked with profound changes in immune transcription signatures and with expansion of antigen-specific immune responses that can be detected in IFN-γ ELISpot.

Citation Format: Palucka AK, Roberts LK, Zurawski SM, Tarnowski J, Turner J, Wang X, Blankenship D, Smith JL, Levin MK, Finholt JP, Burkeholder SB, Timis R, Muniz LS, Dao T, Grant M, Banchereau J, Zurawski G, Pascual V, O'Shaughnessy JA. Immune and transcriptional signatures of dendritic dell (DC) vaccination combined with chemotherapy in locally advanced, triple-negative breast cancer (TNBC) patients [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-05-01.

Human innate responses and adjuvant activity of TLR ligands in vivo in mice reconstituted with a human immune system

TLR ligands (TLR-Ls) represent a class of novel vaccine adjuvants. However, their immunologic effects in humans remain poorly defined in vivo. Using a humanized mouse model with a functional human immune system, we investigated how different TLR-Ls stimulated human innate immune response in vivo and their applications as vaccine adjuvants for enhancing human cellular immune response. We found that splenocytes from humanized mice showed identical responses to various TLR-Ls as human PBMCs in vitro. To our surprise, various TLR-Ls stimulated human cytokines and chemokines differently in vivo compared to that in vitro. For example, CpG-A was most efficient to induce IFN-α production in vitro. In contrast, CpG-B, R848 and Poly I:C stimulated much more IFN-α than CpG-A in vivo. Importantly, the human innate immune response to specific TLR-Ls in humanized mice was different from that reported in C57BL/6 mice, but similar to that reported in nonhuman primates. Furthermore, we found that different TLR-Ls distinctively activated and mobilized human plasmacytoid dendritic cells (pDCs), myeloid DCs (mDCs) and monocytes in different organs. Finally, we showed that, as adjuvants, CpG-B, R848 and Poly I:C can all enhance antigen specific CD4+ T cell response, while only R848 and Poly I:C induced CD8+ cytotoxic T cells response to a CD40-targeting HIV vaccine in humanized mice, correlated with their ability to activate human mDCs but not pDCs. We conclude that humanized mice serve as a highly relevant model to evaluate and rank the human immunologic effects of novel adjuvants in vivo prior to testing in humans.

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.

SIX INDEPENDENT LOSSES OF THE CHLOROPLAST DNA rpl2 INTRON IN DICOTYLEDONS: MOLECULAR AND PHYLOGENETIC IMPLICATIONS

Previous studies have shown that in several angiosperms and the liverwort Marchantia the chloroplast gene rpl2, encoding ribosomal protein L2, is interrupted by an intron, but that in spinach (Spinacia oleracea, Caryophyllales) this intron has been lost. We have determined the distribution of the rpl2 intron for 390 species representing 116 angiosperm families. Filter hybridizations reveal that the intron is absent from the chloroplast genomes of all examined families of the Caryophyllales, suggesting that the intron was lost in the common ancestor of the order. Sequencing of the rpl2 gene in five genera of the Caryophyllales and in Rumex (Polygonales) not only confirms the filter hybridization results, but also shows that for all taxa lacking the intron, the rpl2 gene has undergone a precise deletion of the intron. In all cases, it is the original rpl2 gene that has sustained loss of its intron. This implies that in chloroplast DNA, integration of exogenous genes (e.g., a reverse transcript of a spliced mRNA) occurs mainly by homologous, replacement recombination, rather than by illegitimate recombination elsewhere in the genome. Filter hybridizations also reveal that the rpl2 intron was lost independently in the common ancestors of at least five other lineages of dicotyledons: Saxifragaceae (s.s.), Convolvulaceae (including Cuscuta), Menyanthaceae, two genera of Geraniaceae, and one genus of Droseraceae. The molecular and phylogenetic implications of these independent intron losses are discussed.

Dendritic cell CD40 targeting vaccines elicit CD8+ T cell-mediated therapeutic immunity against cancers

Dendritic cells (DCs) are major antigen-presenting cells that can efficiently cross-prime antigen-specific cytotoxic T lymphocytes (CTLs). Antigen targeting to DCs through surface receptors is therefore a promising strategy to mount CD8+ CTL-mediated immunity against viral infections and cancers. We have previously reported that viral (Influenza HA and NP) and tumor antigen (MART-1) targeting to human DCs via CD40 resulted in greater antigen-specific functional CD8+ CTL responses in vitro. In this study, we have tested CD40 targeting prototype vaccines for HPV16-associated malignancies (anti-CD40-HPV16.E6/7) and prostate cancer (anti-CD40-PSA). Our data show that both anti-CD40-HPV16.E6/7 and anti-CD40-PSA prototype vaccines are able to activate antigen-specific CD8+ T cells in the blood of head-and-neck and prostate cancer patients, respectively. We further demonstrate that the in vivo administration of anti-CD40-HPV16.E6/7 or anti-CD40-PSA plus poly(I:C) can mount tumor-specific CTL-mediated therapeutic and preventive immunity against the respective tumors in human CD40 transgenic mice. Data from this study support the clinical development of CD40 targeting vaccines against cancers and viral infections.

Cross-dressing and antigen transfer after DC targeting induce robust T cell response

Cutaneous dendritic cells (DC) are critical in protecting host from environmental insults as well as maintaining skin homeostasis. Using mouse models that are lack certain subset of cutaneous DC, studies have showed the distinct function of different subsets of skin DC, However, the interaction between skin DC subsets is less known. By targeting antigen to Langerhans cells (LC), we showed that endogenous CD4+ T cell response is independent of MHC II expression on LC. We also showed that LC handed over antigen to CD11b+ dDC and DN dDC. At the same time, MHC II deficient LC acquired MHC-II in the lymph node through cross-dressing. We demonstrated unexpected collaboration between cutaneous DC subsets, and provided insight on DC targeted vaccine design.

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.

A novel therapeutic vaccination delays cART-resistant HIV-1 reservoir rebound in HIV-1 infected humanized mice

Highly active anti-retroviral therapy (HAART) prevents disease progression but does not eradiate HIV, and this therapy often does not fully restore HIV patients’ immune status. Thus, there remains an unmet need to develop new stratagies to “cure” (eradication or control of HIV-1 with no ART) individuals of HIV infection. Modulating host’s cellular immune response is a promising way to cure HIV infection. We have developed a prototype vaccine with a string of 5 highly conserved T cell epitope rich regions of HIV-1 Gag, Nef and Pol fused to a monoclonal antibody that bind the antigen presenting cell activating receptor CD40(aCD40.HIV5pep). Here we use the humanized mouse model to evaluate the therapeutic effect of the aCD40.HIV5pep vaccine to chronic HIV infection. We first screened a batch of novel TLR adjuvants which have the potential to enhance the immunogenicity of aCD40.HIV5pep in vivo and showed that when vaccinated with Poly I:C as adjuvants, aCD40.HIV5pep can induce human CD8+ CTL response in humanized mice. Interestingly, we found that Poly I:C treatment can activate cART-resistant HIV-1 reservoir in in the presence of cART in chronically infected humanized mice. Finally, we showed that Poly I:C plus aCD40.HIV5pep therapeutic vaccination significantly delayed HIV virus rebound in HIV-1 infected humanized mice after withdraw of cART treatment. Our proof-of-concept study in humanized mice has significant implication for the development of therapeutic vaccine to cue HIV infection.

Targeting HIV-1 Env gp140 to LOX-1 Elicits Immune Responses in Rhesus Macaques

Improved antigenicity against HIV-1 envelope (Env) protein is needed to elicit vaccine-induced protective immunity in humans. Here we describe the first tests in non-human primates (NHPs) of Env gp140 protein fused to a humanized anti-LOX-1 recombinant antibody for delivering Env directly to LOX-1-bearing antigen presenting cells, especially dendritic cells (DC). LOX-1, or 1ectin-like oxidized low-density lipoprotein (LDL) receptor-1, is expressed on various antigen presenting cells and endothelial cells, and is involved in promoting humoral immune responses. The anti-LOX-1 Env gp140 fusion protein was tested for priming immune responses and boosting responses in animals primed with replication competent NYVAC-KC Env gp140 vaccinia virus. Anti-LOX-1 Env gp140 vaccination elicited robust cellular and humoral responses when used for either priming or boosting immunity. Co-administration with Poly ICLC, a TLR3 agonist, was superior to GLA, a TLR4 agonist. Both CD4+ and CD8+ Env-specific T cell responses were elicited by anti-LOX-1 Env gp140, but in particular the CD4+ T cells were multifunctional and directed to multiple epitopes. Serum IgG and IgA antibody responses induced by anti-LOX-1 Env gp140 against various gp140 domains were cross-reactive across HIV-1 clades; however, the sera neutralized only HIV-1 bearing sequences most similar to the clade C 96ZM651 Env gp140 carried by the anti-LOX-1 vehicle. These data, as well as the safety of this protein vaccine, justify further exploration of this DC-targeting vaccine approach for protective immunity against HIV-1.

Opposing Roles of Dectin-1 Expressed on Human Plasmacytoid Dendritic Cells and Myeloid Dendritic Cells in Th2 Polarization

Dendritic cells (DCs) can induce and control host immune responses. DC subset-dependent functional specialties and their ability to display functional plasticity, which is mainly driven by signals via pattern recognition receptors, identify DCs as immune orchestrators. A pattern recognition receptor, Dectin-1, is expressed on myeloid DCs and known to play important roles in Th17 induction and activation during fungal and certain bacterial infections. In this study, we first demonstrate that human plasmacytoid DCs express Dectin-1 in both mRNA and protein levels. More interestingly, Dectin-1-activated plasmacytoid DCs promote Th2-type T cell responses, whereas Dectin-1-activated myeloid DCs decrease Th2-type T cell responses. Such contrasting outcomes of Th2-type T cell responses by the two DC subsets are mainly due to their distinct abilities to control surface OX40L expression in response to β-glucan. This study provides new insights for the regulation of host immune responses by Dectin-1 expressed on DCs.

Targeting antigen to CD40 reinforces dendritic cells to cross-prime antigen-specific CD8+ T cells (APP3P.110)

Dendritic cells are major antigen-presenting cells that can efficiently cross-prime antigen-specific CD8+ T cells. Thus, targeting antigen to dendritic cells via surface receptors is an appealing strategy to mount CD8+ T cell-mediated immunity against intracellular pathogens and cancers. Nonetheless, which targeted receptor is the most efficient at priming CD8+ T cells remains elusive. Herein, we report the superior function of CD40 over nine different lectins and scavenger receptors at priming antigen-specific CD8+ T cells. A quantitative analysis of intracellular trafficking of antibody-bound receptors revealed that αCD40 monoclonal antibody localized mainly at the plasma membrane and subsequently accumulated at early endocytic compartments whereas αLOX-1 and αDectin-1 monoclonal antibodies localized at both early and late endocytic compartments in dendritic cells. Regardless of the differences in their subcellular localizations, targeting antigen to CD40 and lectins resulted in the same pattern of peptide epitope-specific IFNg+CD8+ T cell responses. We also report that poly(I:C) can significantly enhance both CD8+ and CD4+ T cell responses elicited by targeting antigen to CD40 in both human in vitro and in human CD40 transgenic mouse in vivo settings. This study provides key information for the rational design of DC-targeting vaccines against cancers and intracellular pathogens.

Toll-like receptor ligands differentially activate human innate immune system and distinctively enhance antigen-specific T cell response to vaccination in humanized mice (VAC4P.1105)

TLR-Ls represent a new class of novel vaccine adjuvant. However, their immunologic effects in humans remain poorly defined in vivo. Here we investigated how TLR-Ls stimulated human immune system in vivo and their application as immune adjuvant using the humanized mouse model. To our surprise, we found that various TLR-Ls (CpG-A/CpG-B/CpG-C, R848, R837, MPLA and Poly I:C) stimulated human cytokines very differently in humanized mice in vivo compared to that in human PBMCs in vitro. The different in vivo response to TLR-Ls was not due to the improper development of human immune cells in vivo because splenocytes from humanized mice showed identical responses as human PBMC in vitro to various TLR-Ls. Importantly, the human innate immune response to specific TLR-Ls in humanized mice in vivo was different from that reported in C57/BL6 mice, but similar to that reported in nonhuman primates. Furthermore, we showed that distinct TLR-Ls differentially activated and mobilized human pDCs, mDCs and monocytes in different organs in vivo. Finally, we showed that Poly I:C and R848 were superior to CpG-B, for enhancing antigen specific CD4+ and CD8+ T cell responses to a CD40-targeting HIV candidate vaccine in humanized mice, which correlated with their ability to activate human CD141+ mDCs and IL-12 induction. Thus, we conclude that humanized mice serve as a highly relevant model to evaluate and rank the human immunologic effects of novel adjuvants in vivo prior to testing in humans.

Candida albicans morphology and DC subsets determines T helper differentiation (MUC2P.920)

Candida albicans is a dimorphic fungus responsible for chronic mucocutaneous and often fatal systemic infections. Mucocutaneous immunity to C. albicans requires Th17 differentiation that is thought to depend on recognition of filamentous C. albicans while systemic resistance is considered T cell independent. Using a murine skin infection model, we compared in vivo T helper responses to yeast and filamentous C. albicans. Unexpectedly, we found that only yeast induced Th17 responses through a mechanism that required Dectin-1 mediated expression of IL-6 by Langerhans cells. Filamentous forms induced Th1 without Th17 due to the absence of Dectin-1 ligation. Notably, Th17 responses provided selective protection against secondary cutaneous infection while Th1 provided protection against systemic infection. Thus, C. albicans morphology drives distinct Th responses that provide tissue specific protection. These findings provide novel insight into compartmentalization of Th responses, C. albicans pathogenesis and have critical implications for vaccine strategies.

Skin dendritic cells induce follicular helper T cells and protective humoral immune responses (VAC4P.1101)

Skin-resident dendritic cells (DC) play a crucial role in initiation of adaptive immune responses against cutaneous pathogens as well as in the maintenance of peripheral tolerance. Recent studies have suggested that steady-state Langerhans cells (LC) induce regulatory T cells against self-antigens. However, the immune response induced by skin DC against foreign antigen in the absence of adjuvants has not been addressed. Here we report that, using anti-huLangerin/ muLangerin antibodies, we could specifically target antigens to LC or CD103+ dermal DC. Presentation of the foreign peptide 2W1S by either LC or CD103+ dDC was sufficient for expansion of naïve CD4+ T cells and induction of T follicular helper cell (Tfh) differentiation. Notably, topical application of peptide or protein also efficiently induced Tfh. The expansion of Tfh specific to foreign peptide was accompanied by activation and expansion of antigen-specific B cells and the development of a robust antibody response that provided systemic protection against influenza infection. This study not only reveals a major unappreciated function of skin DC in humoral response, but also provides insight into DC-targeted vaccine design.

Dectin-1 expressed on pDCs and mDCs displays opposing roles in TH2 polarization (INC6P.321)

Dendritic cells (DCs) can induce and control host immune responses. DC subset-dependent functional specialties and their ability to display functional plasticity, which is mainly driven by signals via pattern-recognition receptors (PRRs), identify DCs as immune orchestrators. A PRR, Dectin-1 is expressed on myeloid DCs (mDCs) and is known to play an important role in TH17 responses. Here, we demonstrate that human plasmacytoid DCs (pDCs) express Dectin-1. Interestingly, Dectin-1-activated pDCs promote TH2 induction and activation, whereas Dectin-1-activated mDCs decrease both. This counter-regulation of TH2 by the two DC subsets is mainly due to their distinct abilities to control OX40L expression through different mechanisms. This study provides new insights for the regulation of host immune responses by DCs during microbial infections.

A novel vaccine for mantle cell lymphoma based on targeting cyclin D1 to dendritic cells via CD40

Background

Mantle cell lymphoma (MCL) is a distinct clinical pathologic subtype of B cell non-Hodgkin’s lymphoma often associated with poor prognosis. New therapeutic approaches based on boosting anti-tumor immunity are needed. MCL is associated with overexpression of cyclin D1 thus rendering this molecule an interesting target for immunotherapy.

Methods

We show here a novel strategy for the development of recombinant vaccines carrying cyclin D1 cancer antigens that can be targeted to dendritic cells (DCs) via CD40.

Results

Healthy individuals and MCL patients have a broad repertoire of cyclin D1-specific CD4⁺ and CD8⁺ T cells. Cyclin D1-specific T cells secrete IFN-γ. DCs loaded with whole tumor cells or with selected peptides can elicit cyclin D1-specific CD8⁺ T cells that kill MCL tumor cells. We developed a recombinant vaccine based on targeting cyclin D1 antigen to human DCs via an anti-CD40 mAb. Targeting monocyte-derived human DCs in vitro with anti-CD40-cyclin D1 fusion protein expanded a broad repertoire of cyclin D1-specific CD4⁺ and CD8⁺ T cells.

Conclusions

This study demonstrated that cyclin D1 represents a good target for immunotherapy and targeting cyclin D1 to DCs provides a new strategy for mantle cell lymphoma vaccine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0131-7) contains supplementary material, which is available to authorized users.

Candida albicans morphology and dendritic cell subsets determine T helper cell differentiation

Candida albicans is a dimorphic fungus responsible for chronic mucocutaneous and systemic infections. Mucocutaneous immunity to C. albicans requires T helper 17 (Th17) cell differentiation that is thought to depend on recognition of filamentous C. albicans. Systemic immunity is considered T cell independent. Using a murine skin infection model, we compared T helper cell responses to yeast and filamentous C. albicans. We found that only yeast induced Th17 cell responses through a mechanism that required Dectin-1-mediated expression of interleukin-6 (IL-6) by Langerhans cells. Filamentous forms induced Th1 without Th17 cell responses due to the absence of Dectin-1 ligation. Notably, Th17 cell responses provided protection against cutaneous infection while Th1 cell responses provided protection against systemic infection. Thus, C. albicans morphology drives distinct T helper cell responses that provide tissue-specific protection. These findings provide insight into compartmentalization of Th cell responses and C. albicans pathogenesis and have critical implications for vaccine strategies.

Facile syntheses of functionalized toll-like receptor 7 agonists

Protein conjugates of toll-like receptor 7 agonists have been shown to elicit powerful immune responses. In order to facilitate our studies in this area our group has developed efficient syntheses for a number of functionalized derivatives that retain immune stimulatory activity.

Transcriptional fingerprints of antigen-presenting cell subsets in the human vaginal mucosa and skin reflect tissue-specific immune microenvironments

Background

Dendritic cells localize throughout the body, where they can sense and capture invading pathogens to induce protective immunity. Hence, harnessing the biology of tissue-resident dendritic cells is fundamental for the rational design of vaccines against pathogens.

Methods

Herein, we characterized the transcriptomes of four antigen-presenting cell subsets from the human vagina (Langerhans cells, CD14^- and CD14⁺ dendritic cells, macrophages) by microarray, at both the transcript and network level, and compared them to those of three skin dendritic cell subsets and blood myeloid dendritic cells.

Results

We found that genomic fingerprints of antigen-presenting cells are significantly influenced by the tissue of origin as well as by individual subsets. Nonetheless, CD14⁺ populations from both vagina and skin are geared towards innate immunity and pro-inflammatory responses, whereas CD14^- populations, particularly skin and vaginal Langerhans cells, and vaginal CD14^- dendritic cells, display both Th2-inducing and regulatory phenotypes. We also identified new phenotypic and functional biomarkers of vaginal antigen-presenting cell subsets.

Conclusions

We provide a transcriptional database of 87 microarray samples spanning eight antigen-presenting cell populations in the human vagina, skin and blood. Altogether, these data provide molecular information that will further help characterize human tissue antigen-presenting cell lineages and their functions. Data from this study can guide the design of mucosal vaccines against sexually transmitted pathogens.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-014-0098-y) contains supplementary material, which is available to authorized users.

C-type lectin-like receptor LOX-1 promotes dendritic cell-mediated class-switched B cell responses

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a pattern-recognition receptor for a variety of endogenous and exogenous ligands. However, LOX-1 function in the host immune response is not fully understood. Here, we report that LOX-1 expressed on dendritic cells (DCs) and B cells promotes humoral responses. On B cells LOX-1 signaling upregulated CCR7, promoting cellular migration toward lymphoid tissues. LOX-1 signaling on DCs licensed the cells to promote B cell differentiation into class-switched plasmablasts and led to downregulation of chemokine receptor CXCR5 and upregulation of chemokine receptor CCR10 on plasmablasts, enabling their exit from germinal centers and migration toward local mucosa and skin. Finally, we found that targeting influenza hemagglutinin 1 (HA1) subunit to LOX-1 elicited HA1-specific protective antibody responses in rhesus macaques. Thus, LOX-1 expressed on B cells and DC cells has complementary functions to promote humoral immune responses.

Macrophage- and neutrophil-derived TNF-α instructs skin langerhans cells to prime antiviral immune responses

Dendritic cells are major APCs that can efficiently prime immune responses. However, the roles of skin-resident Langerhans cells (LCs) in eliciting immune responses have not been fully understood. In this study, we demonstrate for the first time, to our knowledge, that LCs in cynomolgus macaque skin are capable of inducing antiviral-specific immune responses in vivo. Targeting HIV-Gag or influenza hemagglutinin Ags to skin LCs using recombinant fusion proteins of anti-Langerin Ab and Ags resulted in the induction of the viral Ag-specific responses. We further demonstrated that such Ag-specific immune responses elicited by skin LCs were greatly enhanced by TLR ligands, polyriboinosinic polyribocytidylic acid, and R848. These enhancements were not due to the direct actions of TLR ligands on LCs, but mainly dependent on TNF-α secreted from macrophages and neutrophils recruited to local tissues. Skin LC activation and migration out of the epidermis are associated with macrophage and neutrophil infiltration into the tissues. More importantly, blocking TNF-α abrogated the activation and migration of skin LCs. This study highlights that the cross-talk between innate immune cells in local tissues is an important component for the establishment of adaptive immunity. Understanding the importance of local immune networks will help us to design new and effective vaccines against microbial pathogens.

Induction and activation of human Th17 by targeting antigens to dendritic cells via dectin-1

Recent compelling evidence indicates that Th17 confer host immunity against a variety of microbes, including extracellular and intracellular pathogens. Therefore, understanding mechanisms for the induction and activation of Ag-specific Th17 is important for the rational design of vaccines against pathogens. To study this, we employed an in vitro system in which influenza hemagglutinin (HA) 1 was delivered to dendritic cells (DCs) via Dectin-1 using anti-human Dectin-1 (hDectin-1)-HA1 recombinant fusion proteins. We found that healthy individuals maintained broad ranges of HA1-specific memory Th17 that were efficiently activated by DCs targeted with anti-hDectin-1-HA1. Nonetheless, these DCs were not able to induce a significant level of HA1-specific Th17 responses even in the presence of the Th17-promoting cytokines IL-1β and IL-6. We further found that the induction of surface IL-1R1 expression by signals via TCRs and common γ-chain receptors was essential for naive CD4(+) T cell differentiation into HA1-specific Th17. This process was dependent on MyD88, but not IL-1R-associated kinase 1/4. Thus, interruptions in STAT3 or MyD88 signaling led to substantially diminished HA1-specific Th17 induction. Taken together, the de novo generation of pathogen-specific human Th17 requires complex, but complementary, actions of multiple signals. Data from this study will help us design a new and effective vaccine strategy that can promote Th17-mediated immunity against microbial pathogens.

Targeting concatenated HIV antigens to human CD40 expands a broad repertoire of multifunctional CD4+ and CD8+ T cells

OBJECTIVE

Targeting HIV antigens directly to dendritic cells using monoclonal antibodies against cell-surface receptors has been shown to evoke potent cellular immunity in animal models. The objective of this study was to configure an anti-human CD40 antibody fused to a string of five highly conserved CD4 and CD8 T-cell epitope-rich regions of HIV-1 Gag, Nef and Pol (αCD40.HIV5pep), and then to demonstrate the capacity of this candidate therapeutic vaccine to target these HIV peptide antigens to human dendritic cells to expand functional HIV-specific T cells.

METHODS

Antigen-specific cytokine production using intracellular flow cytometry and multiplex bead-based assay, and suppression of viral inhibition, were used to characterize the T cells expanded by αCD40.HIV5pep from HIV-infected patient peripheral blood mononuclear cell (PBMC) and dendritic cell/T-cell co-cultures.

RESULTS

This candidate vaccine expands memory CD4 and CD8 T cells specific to multiple epitopes within all five peptide regions across a wide range of major histocompatibility complex (MHC) haplotypes from HIV-infected patient PBMC and dendritic cell/T-cell co-cultures. These in vitro expanded HIV antigen-specific CD4 and CD8 T cells produce multiple cytokines and chemokines. αCD40.HIV5pep-expanded CD8 T cells have characteristics of cytotoxic effector cells and are able to kill autologous target cells and suppress HIV-1 replication in vitro.

CONCLUSION

Our data demonstrate the therapeutic potential of this CD40-targeting HIV candidate vaccine in inducing a broad repertoire of multifunctional T cells in patients.

Serum from patients with SLE instructs monocytes to promote auto-antigen specific IgG and IgA responses (P4028)

The persistent development of autoantibodies is a hallmark of systemic lupus erythematosus (SLE). Previous work using SLE serum demonstrated that monocyte differentiation into dendritic cells (DCs) is a type I IFN-dependent manner and such SLE-DCs activate T cells. However, whether SLE-DCs promote B cell responses has not been elucidated. Here, we demonstrate that SLE-DCs can efficiently stimulate naïve and memory B cells to differentiate into polyclonal IgG- and IgA-plasmablasts (PBs) resembling those found in the blood of SLE patients. More importantly, when SLE-DCs were stimulated with SLE neutrophils, these SLE-DCs were able to induce ss-DNA specific IgG and IgA from naïve B cells. SLE-DC-mediated IgG-PB differentiation is dependent on BAFF and IL-10, whereas IgA-PB differentiation is mainly dependent on APRIL. Moreover, SLE-DCs as well as monocytes from SLE patients express CD138 and thus can trans-present CD138-bound APRIL to B cells, which is crucial for inducing IgA switching and PB differentiation. The expression of CD138-bound APRIL is not dependent of IFNα, explaining why DCs generated with IFNα (IFN-DCs) are less efficient at inducing IgA responses. Nonetheless, both SLE-DCs and IFN-DCs induce the expression of Bcl-XL in PBs and support their survival, thereby leading to increased Ig production. Taken together, our study suggests that a direct interplay between SLE-DCs and peripheral B cells contribute to SLE pathogenic autoantibody responses.

Langerhans cell and CD103+ dermal dendritic cell promote Tfh in the steady-state (P1094)

Directing antigen to dendritic cells via antibody/antigen conjugates that target antigen-uptake receptors is a highly efficient vaccination technique and also allows for in vivo examination of the effect of antigen presentation by particular DC subsets. Classic experiments determined that antigen presentation in the absence of DC activation led to deletional tolerance. To study the effects of antigen presentation isolated to LC or CD103+ dDC in the steady-state, we performed a series of experiments in which either 1) transgenic mice that express human Langerin only in LC were immunized with anti-human Langerin/antigen complexes or 2) mice lacking LC were immunized with anti-mouse Langerin/antigen complexes. In both cases the DC remained unactivated and antigen was exclusively found on either LC or CD103+ dDC, respectively. Both DC subsets, were able to promote proliferation of MHC-II tetramer binding endogenous CD4 T cells that peaked at day 7 and slowly declined over time without evidence of deletion. Both subsets induced strong expansion of a population of antigen-specific CXCR5+, PD-1+ CD4 T cells that expressed IFNγ, IL-21 and IL-4 which is most consistent with follicular helper T cells (Tfh). In addition, immunization led to the formation of germinal centers in regional LN and was accompanied with a robust humoral response. Thus, presentation in the steady-state by LC and CD103+ dDC promotes Tfh and humoral responses but not deletional tolerance.

Dendritic cells and vaccine design for sexually-transmitted diseases

Dendritic cells (DCs) are major antigen presenting cells (APCs) that can initiate and control host immune responses toward either immunity or tolerance. These features of DCs, as immune orchestrators, are well characterized by their tissue localizations as well as by their subset-dependent functional specialties and plasticity. Thus, the level of protective immunity to invading microbial pathogens can be dependent on the subsets of DCs taking up microbial antigens and their functional plasticity in response to microbial products, host cellular components and the cytokine milieu in the microenvironment. Vaccines are the most efficient and cost-effective preventive medicine against infectious diseases. However, major challenges still remain for the diseases caused by sexually-transmitted pathogens, including HIV, HPV, HSV and Chlamydia. We surmise that the establishment of protective immunity in the female genital mucosa, the major entry and transfer site of these pathogens, will bring significant benefit for the protection against sexually-transmitted diseases. Recent progresses made in DC biology suggest that vaccines designed to target proper DC subsets may permit us to establish protective immunity in the female genital mucosa against sexually-transmitted pathogens.

Noncovalent assembly of anti-dendritic cell antibodies and antigens for evoking immune responses in vitro and in vivo

Targeting of Ags directly to dendritic cells (DCs) through anti-DC receptor Ab fused to Ag proteins is a promising approach to vaccine development. However, not all Ags can be expressed as a rAb directly fused to a protein Ag. In this study, we show that noncovalent assembly of Ab-Ag complexes, mediated by interaction between dockerin and cohesin domains from cellulose-degrading bacteria, can greatly expand the range of Ags for this DC-targeting vaccine technology. rAbs with a dockerin domain fused to the rAb H chain C terminus are efficiently secreted by mammalian cells, and many Ags not secreted as rAb fusion proteins are readily expressed as cohesin directly fused to Ag either via secretion from mammalian cells or as soluble cytoplasmic Escherichia coli products. These form very stable and homogeneous complexes with rAb fused to dockerin. In vitro, these complexes can efficiently bind to human DC receptors followed by presentation to Ag-specific CD4⁺ and CD8⁺ T cells. Low doses of the HA1 subunit of influenza hemagglutinin conjugated through this means to anti-Langerin rAbs elicited Flu HA1-specific Ab and T cell responses in mice. Thus, the noncovalent assembly of rAb and Ag through dockerin and cohesin interaction provides a useful modular strategy for development and testing of prototype vaccines for elicitation of Ag-specific T and B cell responses, particularly when direct rAb fusions to Ag cannot be expressed.

CD34-derived dendritic cells transfected ex vivo with HIV-Gag mRNA induce polyfunctional T-cell responses in nonhuman primates

The pivotal role of DCs in initiating immune responses led to their use as vaccine vectors. However, the relationship between DC subsets involved in antigen presentation and the type of elicited immune responses underlined the need for the characterization of the DCs generated in vitro. The phenotypes of tissue-derived APCs from a cynomolgus macaque model for human vaccine development were compared with ex vivo-derived DCs. Monocyte/macrophages predominated in bone marrow (BM) and blood. Myeloid DCs (mDCs) were present in all tested tissues and were more highly represented than plasmacytoid DCs (pDCs). As in human skin, Langerhans cells (LCs) resided exclusively in the macaque epidermis, expressing CD11c, high levels of CD1a and langerin (CD207). Most DC subsets were endowed with tissue-specific combinations of PRRs. DCs generated from CD34(+) BM cells (CD34-DCs) were heterogeneous in phenotype. CD34-DCs shared properties (differentiation and PRR) of dermal and epidermal DCs. After injection into macaques, CD34-DCs expressing HIV-Gag induced Gag-specific CD4(+) and CD8(+) T cells producing IFN-γ, TNF-α, MIP-1β, or IL-2. In high responding animals, the numbers of polyfunctional CD8(+) T cells increased with the number of booster injections. This DC-based vaccine strategy elicited immune responses relevant to the DC subsets generated in vitro.

Serum from patients with SLE instructs monocytes to promote IgG and IgA plasmablast differentiation

Monocytes exposed to serum from SLE patients promote B cell differentiation to IgG and IgA plasmablasts dependent on BAFF and IL-10 or APRIL, respectively.

The development of autoantibodies is a hallmark of systemic lupus erythematosus (SLE). SLE serum can induce monocyte differentiation into dendritic cells (DCs) in a type I IFN–dependent manner. Such SLE-DCs activate T cells, but whether they promote B cell responses is not known. In this study, we demonstrate that SLE-DCs can efficiently stimulate naive and memory B cells to differentiate into IgG- and IgA-plasmablasts (PBs) resembling those found in the blood of SLE patients. SLE-DC–mediated IgG-PB differentiation is dependent on B cell–activating factor (BAFF) and IL-10, whereas IgA-PB differentiation is dependent on a proliferation-inducing ligand (APRIL). Importantly, SLE-DCs express CD138 and trans-present CD138-bound APRIL to B cells, leading to the induction of IgA switching and PB differentiation in an IFN-α–independent manner. We further found that this mechanism of providing B cell help is relevant in vivo, as CD138-bound APRIL is expressed on blood monocytes from active SLE patients. Collectively, our study suggests that a direct myeloid DC–B cell interplay might contribute to the pathogenesis of SLE.

TSLP driven inflammation fosters breast tumor development (74.2)

Solid tumors are often associated with aseptic inflammation. There are two types of inflammation that have opposing effects on tumors, chronic inflammation that promotes cancer survival and metastasis, and acute inflammation which triggers cancer destruction. Chronic inflammation is often linked with the presence of type 2-polarized macrophages induced by Th2 cytokines, IL-4 and IL-13. Our studies have demonstrated the presence in breast cancer tumors of inflammatory Th2 cells, which produce IL-13, IL-4, and TNF. These CD4+ T cells appear to play a key role in the disease as they accelerate breast tumor development in a xenograft model through the production of IL-13. Breast tumors appear to play a critical role in conditioning the infiltrating myeloid DCs (mDCs) to induce such inflammatory Th2 cells. Our recent results suggest that thymic stromal lymphopoetin (TSLP) plays a role in mDCs conditioning. Breast cancer cell lines and primary tumors from patients show TSLP protein expression. TSLP-neutralizing antibodies block the upregulation of OX40L by mDCs exposed to tumor supernatant and consequently block mDCs capacity to generate inflammatory Th2 cells in vitro. Targeting pattern recognition receptors on mDCs renders them resistant to TSLP signal. These mDCs don't phosphorylate STAT6, don't express OX40L and turn on the secretion of IL12p70. The final outcome is the block of inflammatory Th2 and tumor rejection. Thus, TSLP could serve as therapeutic target in breast cancer.