Development of a New Off-the-Shelf Plasmacytoid Dendritic Cell-Based Approach for the Expansion and Characterization of SARS-CoV-2-Specific T Cells

Global vaccination against COVID-19 has been widely successful; however, there is a need for complementary immunotherapies in severe forms of the disease and in immunocompromised patients. Cytotoxic CD8+ T cells have a crucial role in disease control, but their function can be dysregulated in severe forms of the disease. We report here a cell-based approach using a plasmacytoid dendritic cell line (PDC*line) to expand in vitro specific CD8+ responses against COVID-19 Ags. We tested the immunogenicity of eight HLA-A*02:01 restricted peptides derived from diverse SARS-Cov-2 proteins, selected by bioinformatics analyses in unexposed and convalescent donors. Higher ex vivo frequencies of specific T cells against these peptides were found in convalescent donors compared with unexposed donors, suggesting in situ T cell expansion upon viral infection. The peptide-loaded PDC*line induced robust CD8+ responses with total amplification rates that led up to a 198-fold increase in peptide-specific CD8+ T cell frequencies for a single donor. Of note, six of eight selected peptides provided significant amplifications, all of which were conserved between SARS-CoV variants and derived from the membrane, the spike protein, the nucleoprotein, and the ORF1ab. Amplified and cloned antiviral CD8+ T cells secreted IFN-γ upon peptide-specific activation. Furthermore, specific TCR sequences were identified for two highly immunogenic Ags. Hence, PDC*line represents an efficient platform to identify immunogenic viral targets for future immunotherapies.

Maternal imprinting and determinants of neonates' immune function in the SEPAGES mother-child cohort

Introduction

Immune function in pregnancy is influenced by host-specific and environmental factors. This may impact fetal immune development, but the link between maternal and neonatal immune function is still poorly characterized. Here, we investigate the relationship between maternal and neonatal immune function, and identify factors affecting the association between maternal and child cytokine secretion.

Methods

In the French prospective cohort SEPAGES, blood samples were obtained from pregnant women (n=322) at gestational week 20 ± 4 and from their child at birth (n=156). Maternal and cord blood cytokine and chemokine (CK) levels were measured at baseline in all subjects and after T cell or dendritic cell activation with phytohemagglutinin or R848 (in total 29 and 27 measures in maternal and cord blood samples, respectively). Associations between environmental, individual factors and CK level were estimated by linear regression modeling. The maternal-cord blood CK relations were assessed by Pearson correlation and regression models.

Results

We observed that pregnant women and neonates displayed specific CK secretion profiles in the innate and adaptive compartments at baseline and upon activation. Activation of T cells in cord blood induced high levels of IL-2, but low levels of IFNγ, IL-13 or IL-10, in comparison to maternal blood samples. Elsewhere, neonatal innate immune responses were characterized by low production of IFNα, while productions of IL-1β, IL-6, IL-8, IL-10 and TNFα were higher than maternal responses. Strong correlations were observed between most CK after activation in maternal and cord blood samples. Strikingly, a statistical association between global mother and child cytokine profiles was evidenced. Correlations were observed between some individual CK of pregnant women and their children, both at baseline (MCP1, RANTES) and after activation with R848 (IL-6, IL-8 and IL-10). We looked for factors which could influence cytokine secretion in maternal or cord blood, and found that leucocyte counts, maternal age, pre-conception BMI, smoking and season were associated with the levels of several CK in mothers or children.

Discussion

Our study reveals in utero immune imprinting influencing immune responses in infants, opening the way to investigate the mechanisms responsible for this imprinting. Whether such influences have long lasting effects on children health warrants further investigation.

Behçet's disease risk-variant HLA-B51/ERAP1-Hap10 alters human CD8 T cell immunity

OBJECTIVES

The endoplasmic reticulum aminopeptidase (ERAP1) haplotype Hap10 encodes for a variant allotype of the endoplasmic reticulum (ER)-resident peptide-trimming aminopeptidase ERAP1 with low enzymatic activity. This haplotype recessively confers the highest risk for Behçet's diseases (BD) currently known, but only in carriers of HLA-B*51, the classical risk factor for the disease. The mechanistic implications and biological consequences of this epistatic relationship are unknown. Here, we aimed to determine its biological relevance and functional impact.

METHODS

We genotyped and immune phenotyped a cohort of 26 untreated Turkish BD subjects and 22 healthy donors, generated CRISPR-Cas9 ERAP1 KOs from HLA-B*51 ⁺ LCL, analysed the HLA class I-bound peptidome for peptide length differences and assessed immunogenicity of genome-edited cells in CD8 T cell co-culture systems.

RESULTS

Allele frequencies of ERAP1-Hap10 were similar to previous studies. There were frequency shifts between antigen-experienced and naïve CD8 T cell populations of carriers and non-carriers of ERAP1-Hap10 in an HLA-B*51 background. ERAP1 KO cells showed peptidomes with longer peptides above 9mer and significant differences in their ability to stimulate alloreactive CD8 T cells compared with wild-type control cells.

CONCLUSIONS

We demonstrate that hypoactive ERAP1 changes immunogenicity to CD8 T cells, mediated by an HLA class I peptidome with undertrimmed peptides. Naïve/effector CD8 T cell shifts in affected carriers provide evidence of the biological relevance of ERAP1-Hap10/HLA-B*51 at the cellular level and point to an HLA-B51-restricted process. Our findings suggest that variant ERAP1-Hap10 partakes in BD pathogenesis by generating HLA-B51-restricted peptides, causing a change in immunodominance of the ensuing CD8 T cell response.

Impaired Antitumor Immune Response in MYCN-amplified Neuroblastoma Is Associated with Lack of CCL2 Secretion and Poor Dendritic Cell Recruitment

In neuroblastoma, MYCN amplification is associated with sparse immune infiltrate and poor prognosis. Dendritic cells (DC) are crucial immune sentinels but their involvement in neuroblastoma pathogenesis is poorly understood. We observed that the migration of monocytes, myeloid and plasmacytoid DC induced by MYCN-nonamplified neuroblastoma supernatants was abrogated by the addition of anti-CCL2 antibodies, demonstrating the involvement of the CCR2/CCL2 axis in their recruitment by these tumors. Using public RNA sequencing and microarray datasets, we describe lower level of expression of CCL2 in MYCN-amplified neuroblastoma tumors, and we propose a working model for T-cell recruitment in neuroblastoma tumors in which CCL2 produced by neuroblastoma cells initiates the recruitment of monocytes, myeloid and plasmacytoid DCs. Among these cells, the CD1c⁺ subset may recruit T cells by means of CCL19/CCL22 secretion. In vitro, supernatants from DCs cocultured with neuroblastoma cell lines and activated contain CCL22 and CCL19, and are chemotactic for both CD4⁺ and CD8⁺ T cells. We also looked at immunomodulation induced by neuroblastoma cell lines, and found MYCN-nonamplified neuroblastoma cell lines were able to create a microenvironment where DC activation is enhanced. Overall, our findings highlight a major role for CCL2/CCR2 axis in monocytes, myeloid and plasmacytoid cells recruitment toward MYCN-nonamplified neuroblastoma, allowing further immune cell recruitment, and show that these tumors present a microenvironment that can favor DC responses.

Significance

In MYCN-nonamplified neuroblastoma, CCL2 produced by neuroblastoma cells induces the recruitment of antigen-presenting cells (DCs and monocytes/macrophages), allowing infiltration by T cells, in link with CCL19 and CCL22 production, hence favoring immune responses.

Dysfunctional BTN3A together with deregulated immune checkpoints and type I/II IFN dictate defective interplay between pDCs and γδ T cells in melanoma patients, which impacts clinical outcomes

Objectives

pDCs and γδ T cells emerge as potent immune players participating in the pathophysiology of cancers, yet still remaining enigmatic while harbouring a promising potential for clinical translations. Despite strategic and closed missions, crosstalk between pDCs and γδ T cells has not been deciphered yet in cancers, especially in melanoma where the long‐term control of the tumor still remains a challenge.

Methods

This prompted us to explore the interplay between pDCs and γδ T cells in the context of melanoma, investigating the reciprocal features of pDCs or γδ T cells, the underlying molecular mechanisms and its impact on clinical outcomes.

Results

TLRL‐activated pDCs from the blood and tumor infiltrate of melanoma patients displayed an impaired ability to activate, to modulate immune checkpoints and trigger the functionality of γδ T cells. Conversely, γδ T cells from the blood or tumor infiltrate of melanoma patients activated by PAg were defective in triggering pDCs’ activation and modulation of immune checkpoints, and failed to elicit the functionality of pDCs. Reversion of the dysfunctional cross‐talks could be achieved by specific cytokine administration and immune checkpoint targeting. Strikingly, we revealed an increased expression of BTN3A on circulating and tumor‐infiltrating pDCs and γδ T cells from melanoma patients, but stressed out the potential impairment of this molecule.

Conclusion

Our study uncovered that melanoma hijacked the bidirectional interplay between pDCs and γδ T cells to escape from immune control, and revealed BTN3A dysfunction. Such understanding will help harness and synergise the power of these potent immune cells to design new therapeutic approaches exploiting their antitumor potential while counteracting their skewing by tumors to improve patient outcomes.

BDCA1+ cDC2s, BDCA2+ pDCs and BDCA3+ cDC1s reveal distinct pathophysiologic features and impact on clinical outcomes in melanoma patients

Objectives

Dendritic cells play a pivotal but still enigmatic role in the control of tumor development. Composed of specialised subsets (cDC1s, cDC2s, pDCs), DCs are critical in triggering and shaping antitumor immune responses. Yet, tumors exploit plasticity of DCs to subvert their functions and escape from immune control. This challenging controversy prompted us to explore the pathophysiological role of cDCs and pDCs in melanoma, where their precise and coordinated involvement remains to be deciphered.

Methods

We investigated in melanoma patients the phenotypic and functional features of circulating and tumor‐infiltrating BDCA1⁺ cDC2s, BDCA2⁺ pDCs and BDCA3⁺ cDC1s and assessed their clinical impact.

Results

Principal component analyses (PCA) based on phenotypic or functional parameters of DC subsets revealed intra‐group clustering, highlighting specific features of DCs in blood and tumor infiltrate of patients compared to healthy donors. DC subsets exhibited perturbed frequencies in the circulation and actively infiltrated the tumor site, while harbouring a higher activation status. Whereas cDC2s and pDCs displayed an altered functionality in response to TLR triggering, circulating and tumor‐infiltrating cDC1s preserved potent competences associated with improved prognosis. Notably, the proportion of circulating cDC1s predicted the clinical outcome of melanoma patients.

Conclusion

Such understanding uncovers critical and distinct impact of each DC subset on clinical outcomes and unveils fine‐tuning of interconnections between DCs in melanoma. Elucidating the mechanisms of DC subversion by tumors could help designing new therapeutic strategies exploiting the potentialities of these powerful immune players and their cross‐talks, while counteracting their skewing by tumors, to achieve immune control and clinical success.

OP0032 ERAP1-MEDIATED IMMUNOGENICITY AND IMMUNE-PHENOTYPES IN HLA-B51+ BEHÇET’S DISEASE POINT TO PATHOGENIC CD8 T CELL EFFECTOR RESPONSES

Background:

HLA-B51 is a definite risk factor for Behçet’s disease (BD). A coding variant of ERAP1, Hap10 – with low peptide-trimming activity – vastly potentiates this risk, but is mechanistically unclear1,2).

Objectives:

To test the hypothesis that low or absent ERAP1 activity alters CD8 T cell immunogenicity through changes in the HLA-B51 peptidome and shapes the CD8 T cell immune response in affected subjects.

Methods:

We generated HLA-B51+ERAP1 KO LCL clones using CRISPR-Cas9, performed mass spectrometry of the immunoprecipitated MHC-class I peptidome with subsequent computational deconvolution for HLA-B51-binding peptides. We then assessed single cell (ICS), bulk (ELISA) and proliferative (CFSE) CD8 effector (IFNg, granzyme B, perforin) T cell responses through stimulation of allogeneic donor cells with WT vs KO LCL and determined ERAP1 haplotypes in 49 untreated Turkish BD subjects with ocular and/ or major vascular involvement as well as healthy donors (HD) whose PBMC were profiled using 6 multicolour flow cytometry panels.

Results:

WT and KO peptidomes differed significantly (p<0.0005 Fisher’s exact test) with a distinctive shift of peptide length frequencies exceeding 9-mer (binding optimum) in the KO vs WT. This held true for computationally deconvoluted HLA-B51 binders. IFNg secretion from CD8 T cells stimulated with KO LCL was significantly different from WT (ICS, p=0.0006; ELISA, p=0.0059) as were CD8 T cell proliferation and ICS of perforin/granzyme B+CD8 T cells. Analysis of 133 T, B, NK and monocyte cell populations revealed predominance of CD8 T and NKT cell subset in HLA-B51+/Hap10+ BD vs HLA-B51+/Hap10- BD and HD, accounting for 80% of all populations reaching significance (p<0.05, Mann-Whitney). Naive and effector memory CD8 T cell subsets were inversely correlated. Cohen’s effect sizes were large (>0.8) or very large (>1.2).

Conclusion:

We show that absence of functional ERAP1 alters human CD8 T cell immunogenicity. This is mediated by an HLA-class I peptidome with propensity for longer peptides above 9mer and suggests loss or de-novo presentation of peptide-HLA-B51 complexes to cognate CD8 TCR. The reciprocal changes in antigen- experienced vs naive CD8 T cell subsets in affected subjects point to biologic significance of HLA-B51/Hap10 in BD. Collectively, our findings suggest that an altered HLA-B51 peptidome modulates immunogenicity of CD8 effector T cells in ERAP1-Hap10 carriers with BD and identify targets for future drug development.

References:

[1]Kirino, Y., G. Bertsias, Y. Ishigatsubo, N. Mizuki, I. Tugal-Tutkun, E. Seyahi, Y. Ozyazgan, F. S. Sacli, B. Erer, H. Inoko, Z. Emrence, A. Cakar, N. Abaci, D. Ustek, C. Satorius, A. Ueda, M. Takeno, Y. Kim, G. M. Wood, M. J. Ombrello, A. Meguro, A. Gul, E. F. Remmers, and D. L. Kastner. 2013. ‘Genome-wide association analysis identifies new susceptibility loci for Behcet’s disease and epistasis between HLA-B*51 and ERAP1’,Nat Genet, 45: 202-7.

[2]Takeuchi, M., M. J. Ombrello, Y. Kirino, B. Erer, I. Tugal-Tutkun, E. Seyahi, Y. Ozyazgan, N. R. Watts, A. Gul, D. L. Kastner, and E. F. Remmers. 2016. ‘A single endoplasmic reticulum aminopeptidase-1 protein allotype is a strong risk factor for Behcet’s disease in HLA-B*51 carriers’,Ann Rheum Dis, 75: 2208-11.

Disclosure of Interests:

Arshed F. Al-Obeidi: None declared, Ann Cavers: None declared, Yesim Ozguler: None declared, Olivier Manches: None declared, Hua Zhong: None declared, Berna Yurttas: None declared, Beatrix Ueberheide: None declared, Gulen Hatemi Grant/research support from: BMS, Celgene Corporation, Silk Road Therapeutics – grant/research support, Consultant of: Bayer, Eli Lilly – consultant, Speakers bureau: AbbVie, Mustafa Nevzat, Novartis, UCB – speaker, Matthias Kugler: None declared, Johannes Nowatzky: None declared

Generation of Human Regulatory T Cell Clones

Human regulatory T cells (Treg) are notoriously difficult to isolate in high purity given the current methods of Treg enrichment. These methods are based on the identification of Treg through several activation-dependent cellular surface markers with varying expression levels in different physiologic and pathologic conditions. Populations isolated as "Treg" therefore often contain considerable numbers of non-Treg effector cells (i.e., Teff) which hamper the precise phenotypic and functional characterization of these cells, their genomic and proteomic characterization, their reliable enumeration in different states of health and disease, as well as their isolation and expansion for therapeutic purposes. The latter, in particular, remains a major hurdle, as the inadvertent expansion of effector cells homing in Treg-relevant cellular compartments (e.g., CD4⁺CD25⁺ T cells) may render Treg-based immunotherapy ineffective, or even harmful. This work presents a method that circumvents the problems associated with population-based isolation and expansion of Treg and shows that the generation of Treg candidate clones with the subsequent selection, culture, and expansion of only carefully vetted, monoclonal cells, enables the generation of an ultrapure Treg cell product that can be kept in culture for many months, enabling downstream investigation of these cells, including for possible therapeutic applications.

An innovative plasmacytoid dendritic cell line-based cancer vaccine primes and expands antitumor T-cells in melanoma patients in a first-in-human trial

The efficacy of immune checkpoint inhibitors has been shown to depend on preexisting antitumor immunity; thus, their combination with cancer vaccines is an attractive therapeutic approach. Plasmacytoid dendritic cells (PDC) are strong inducers of antitumor responses and represent promising vaccine candidates. We developed a cancer vaccine approach based on an allogeneic PDC line that functioned as a very potent antigen-presenting cell in pre-clinical studies. In this phase Ib clinical trial, nine patients with metastatic stage IV melanoma received up to 60 million irradiated PDC line cells loaded with 4 melanoma antigens, injected subcutaneously at weekly intervals. The primary endpoints were safety and tolerability. The vaccine was well tolerated and no serious vaccine-induced side effects were recorded. Strikingly, there was no allogeneic response toward the vaccine, but a significant increase in the frequency of circulating anti-tumor specific T lymphocytes was observed in two patients, accompanied by a switch from a naïve to memory phenotype, thus demonstrating priming of antigen-specific T-cells. Signs of clinical activity were observed, including four stable diseases according to IrRC and vitiligoïd lesions. Four patients were still alive at week 48. We also demonstrate the in vitro enhancement of specific T cell expansion induced by the synergistic combination of peptide-loaded PDC line with anti-PD-1, as compared to peptide-loaded PDC line alone. Taken together, these clinical observations demonstrate the ability of the PDC line based-vaccine to prime and expand antitumor CD8+ responses in cancer patients. Further trials should test the combination of this vaccine with immune checkpoint inhibitors.

Photopheresis efficacy in the treatment of rheumatoid arthritis: a pre-clinical proof of concept

BACKGROUND

Despite major advances in rheumatoid arthritis outcome, not all patients achieve remission, and there is still an unmet need for new therapeutic approaches. This study aimed at evaluating in a pre-clinical murine model the efficacy of extracorporeal photopheresis (ECP) in the treatment of rheumatoid arthritis, and to provide a relevant study model for dissecting ECP mechanism of action in autoimmune diseases.

METHODS

DBA/1 mice were immunized by subcutaneous injection of bovine collagen type II, in order to initiate the development of collagen-induced arthritis (CIA). Arthritic mice received 3 ECP treatments every other day, with psoralen + UVA-treated (PUVA) spleen cells obtained from arthritic mice. Arthritis score was measured, and immune cell subsets were monitored.

RESULTS

ECP-treated mice recovered from arthritis as evidenced by a decreasing arthritic score over time. Significant decrease in the frequency of Th17 cells in the spleen of treated mice was observed. Interestingly, while PUVA-treated spleen cells from healthy mouse had no effect, PUVA-treated arthritic mouse derived-spleen cells were able to induce control of arthritis development.

CONCLUSIONS

Our results demonstrate that ECP can control arthritis in CIA-mice, and clarifies ECP mechanisms of action, showing ECP efficacy and Th17 decrease only when arthritogenic T cells are contained within the treated sample. These data represent a pre-clinical proof of concept supporting the use of ECP in the treatment of RA in Human.

Flow Plex-A tool for unbiased comprehensive flow cytometry data analysis

Introduction

The information content of multiparametric flow cytometry experiments is routinely underexploited given the paucity of adequate tools for unbiased comprehensive data analysis that can be applied successfully and independently by immunologists without computational training.

Methods

We aimed to develop a tool that allows straightforward access to the entire information content of any given flow cytometry panel for immunologists without special computational expertise. We used a data analysis approach which accounts for all mathematically possible combinations of markers in a given panel, coded the algorithm and applied the method to mined and self‐generated data sets.

Results

We developed Flow Plex, a straightforward computational tool that allows unrestricted access to the information content of a given flow cytometry panel, enables classification of human samples according to distinct immune phenotypes, such as different forms of autoimmune uveitis, acute myeloid leukemia vs “healthy”, “old” vs “young”, and facilitates the identification of cell populations with potential biologic relevance to states of disease and health.

Conclusions

We provide a tool that allows immunologists and other flow cytometry users with limited bioinformatics skills to extract comprehensive, unbiased information from flow cytometry data sets.

The features of circulating and tumor-infiltrating γδ T cells in melanoma patients display critical perturbations with prognostic impact on clinical outcome

γδT cells hold a pivotal role in tumor immunosurveillance through their prompt activation and cytokine secretion, their ability to kill tumor cells in an Human Leukocyte Antigen (HLA)-unrestricted manner, and their combination of features of both innate and adaptive immunity. These unique properties and functional plasticity render them very attractive both as targets and vectors for cancer immunotherapy. Yet, these potent and fascinating antitumor effectors have not been extensively explored in melanoma. We provided here a detailed investigation of the phenotypic and functional properties of circulating and tumor-infiltrating γδT cells in melanoma patients, and their impact on clinical evolution. High proportions of circulating- and tumor-infiltrating γδT and δ2+ subset were associated with better clinical outcome. We reported however that circulating and tumor-infiltrating γδT cells from melanoma patients displayed an altered expression of NCR, KIR, and immune checkpoints, and identified NKp44, PD1, 41BB/41BBL, TIM3, and LAG3 as crucial checkpoints allowing immune escape and tumor progression. Notably, melanoma drastically impaired the ability of γδT cells to exhibit activation molecules, secrete cytokines, and display cytotoxicity toward melanoma in response to stimulation with phosphoantigens. It drove them toward regulatory and Th17 profiles associated with poor clinical outcomes. Our study highlights that melanoma hijacked γδT cells to escape from immune control, and revealed that circulating and tumor-infiltrating γδT cell features are promising potential biomarkers of clinical evolution. Such understanding of the physiopathology of γδT cells may help designing new therapeutic approaches exploiting the antitumor potential of γδT cells while counteracting their skewing by tumors to improve patient outcomes.

Multi-organ failure induced by Nivolumab in the context of allo-stem cell transplantation

Background

Immune checkpoint inhibitors have radically changed the landscape of anti-tumor therapies in several malignancies. However the adverse events associated with immune checkpoint blockade in combination with other treatments remains to be thoroughly documented. Here we report the case of a 33-year-old male with classical Hodgkin lymphoma who was successfully treated for lymphoma but experienced serious and eventually fatal multisystem organ failure following nivolumab administration and allogeneic stem cell transplantation.

Case presentation

The patient was diagnosed with stage IIIa nodular sclerosing Hodgkin lymphoma. Originally treated by chemotherapy and autologous stem cell transplantation, he subsequently received two allogeneic stem cell transplants from matched and haplo-identical siblings upon successive disease recurrences. Nivolumab treatment was administered prior to the second allograft, after which complete remission of lymphoma was achieved (year 10), as evidenced by clinical and radiographic examination. However within the next 3 months, the patient went on to develop a constellation of symptoms affecting multiple organs, including acute pneumonia with no evidence of bacterial infection, widespread cutaneous eruptions on trunk and lower limbs, mucosal ulcerations, myositis, diarrhea and colitis. Further complications included hepatic cytolysis, acute renal failure, pancreatitis, as well as complete heart block. Some of these injuries being suggestive of graft-versus-host disease, the patient was administered immunosuppressive therapy (mycophenolate, steroids and polyvalent immunoglobulins), but died shortly afterwards. Tissue biopsies revealed extensive lymphocytic infiltration (mostly CD3 + T cells) in skin, liver, and most peculiarly in muscles, including the myocardium. Massive lymphoid-histiocytic infiltration of muscle fibers was accompanied by acute necrotizing myositis and endomysial inflammation.

Conclusions

Multi-organ failure represents a rare but potentially fatal outcome of immune checkpoint blockade in patients receiving allogeneic stem cell grafts. Nivolumab may induce atypical immune-mediated tissue inflammation and damage, such as the extensive muscular polymyositis described here in a patient with Hodgkin lymphoma. Nivolumab might also worsen GVHD symptoms in the context of allogeneic stem cell transplantation. Irrespective of the actual pathological mechanisms, clinicians should be alerted to these fatal drug-related toxicities.

Modulation of human Th17 cell responses through complement receptor 3 (CD11 b/CD18) ligation on monocyte-derived dendritic cells

OBJECTIVE

Apoptotic cell receptors contribute to the induction of tolerance by modulating dendritic cell function following the uptake of apoptotic cells or microparticles. Dendritic cells that have bound or ingested apoptotic cells produce only low amounts of pro-inflammatory cytokines and fail to prime effector T cell responses. Specifically, ligation of the apoptotic cell receptor CR3 (CD11 b/CD18) on human monocyte-derived dendritic cells (moDC) down-modates proinflammatory cytokine secretion, but the consequences for human Th17 cell homeostasis and effector responses remain unknown. Here, we aimed to establish whether CD11b-ligated moDC modulate Th17 cell effector reponses to assess their potential for future use in moDC-based suppressive immunotherapy.

METHODS

We generated a bead-based surrogate system to target CD11b on monocyte-derived human dendritic cells and examined the effects of CD11b ligation on Th17-skewing cytokine secretion, priming, expansion and functional plasticity in DC/T cell co-culture systems at the poly- and monoclonal level.

RESULTS

We show that Th17 cell expansion within the human memory CD4⁺ T cell compartment was efficiently constricted by targeting the CD11b receptor on moDC. This tolerogenic capacity was primarily dependent on cytokine skewing. Furthermore, ligation of CD11b on healthy homozygous carriers of the rs11143679 (ITGAM) variant - a strong genetic susceptibility marker for human systemic lupus erythematosus - also down-modulated the secretion of Th17-skewing cytokines.

CONCLUSION

Overall, our findings underline the potential of targeted CD11b ligation on human dendritic cells for the engineering of suppressive immunotherapy for Th17-related autoimmune disorders.

High output flow cytometry array profiling facilitates discriminant phenotyping of peripheral blood cells from patients with different forms of autoimmune uveitis

The information content of multi-parametric flow cytometry-based immune-phenotyping experiments is often underexploited given the paucity of adequate tools and strategies for large-scale unbiased data analysis. Here, we developed and applied a data analysis approach taking into account all mathematically possible combinations of markers in a given flow cytometry panel. We analyzed flow cytometry data generated from peripheral blood samples of healthy humans and patients with autoimmune uveitis in the setting of 2 different autoimmune diseases: Behcet’s disease and sarcoidosis. Original FACS data files were mined from Dryad Digital Repository http://dx.doi.org/10.5061/dryad.v6ste with reference to http://dx.doi.org/10.1371/journal.pcbi.1003215, and gated in bivariate plots. We employed combinatory mathematics to generate a matrix quantifying the representation of all possible cell populations using a given set of markers within the respective starting population and coded the algorithm to create a Java-based platform enabling the computation of large numbers of markers. Resulting metadata were visualized in a heat map approach. Our method enabled clustering of healthy vs diseased subjects using only 4 common markers (CD3, C8, CD197, and CD45), and of sarcoid vs Behcet’s patients with minimal error. Our approach demonstrates that multi-dimensional analysis of flow cytometry data allows meaningful large-scale screening of biologically relevant markers enabling classification and characterization of states of health and autoimmune disease. The approach is unbiased and has the potential to facilitate the discovery of cell populations with relevance as potential biomarkers or biological research targets.

CD4 Receptor is a Key Determinant of Divergent HIV-1 Sensing by Plasmacytoid Dendritic Cells

Plasmacytoid dendritic cells (pDC) are innate immune cells that sense viral nucleic acids through endosomal Toll-like receptor (TLR) 7/9 to produce type I interferon (IFN) and to differentiate into potent antigen presenting cells (APC). Engagement of TLR7/9 in early endosomes appears to trigger the IRF7 pathway for IFN production whereas engagement in lysosomes seems to trigger the NF-κB pathway for maturation into APC. We showed previously that HIV-1 (HIV) localizes predominantly to early endosomes, not lysosomes, and mainly stimulate IRF7 rather than NF-κB signaling pathways in pDC. This divergent signaling may contribute to disease progression through production of pro-apoptotic and pro-inflammatory IFN and inadequate maturation of pDCs. We now demonstrate that HIV virions may be re-directed to lysosomes for NF-κB signaling by either pseudotyping HIV with influenza hemagglutinin envelope or modification of CD4 mediated-intracellular trafficking. These data suggest that HIV envelope-CD4 receptor interactions drive pDC activation toward an immature IFN producing phenotype rather than differentiation into a mature dendritic cell phenotype.

Plasmacytoid dendritic cells (pDC) are innate immune cells that are specialized to produce type I interferon (IFN) and to activate adaptive immune responses. Although IFN is an anti-viral cytokine, it may contribute more to pathogenesis than to protection during chronic viral infections, including chronic HIV infection. pDC sense HIV to produce abundant IFN but minimal NF- κB–dependent production of TNFα and minimal up-regulation of co-stimulatory molecules, suggesting that HIV promotes pDC to become interferon producing cells (IPC) rather than antigen presenting cells (APC). Here, we use florescent HIV virions pseudotyped with influenza hemagglutinin (HA) envelope and a cell system expressing CD4 molecules with modified intracellular trafficking. We found that HIV virions pseudotyped with HA stimulate pDC to mature, similar to influenza-stimulated pDC, and traffic intracellularly similarly to influenza. We also find that CD4-mediated intracellular trafficking guides HIV trafficking and downstream signaling. Our study presents new and important findings which demonstrate that divergent HIV sensing by pDC to produce IFN, rather than to become mature antigen presenting cells, is mediated specifically by CD4-HIV envelope interactions.

Massive monoclonal expansion of functionally stable human regulatory T cells (THER5P.826)

Adoptive Treg transfer is a promising therapeutic strategy for autoimmune diseases. Most current approaches rely on the enrichment and in vitro expansion of non-clonal, presumably thymus-derived Treg cells. Limitations include low expansion rates, contaminating effector cells, and unstable suppressive activity. Here, we hypothesized that cloning of human CD4+CD127lowCD25highFoxP3+HELIOS+ cells yields a highly pure cellular product with stable suppressor function throughout repeated re-expansion cycles. Cloning was performed through selection for CD4+CD127lowCD25+ cells by magnetic bead isolation and expansion in limiting dilution conditions. Suppressor function was tested in suppression assays of CD3/CD28-stimulated allogeneic Teff cells. Clonality was assessed by Vbeta staining. To demonstrate validity of our approach for a human autoimmune disease we also cloned Treg from a patient with Behcet's disease, a multisystem vasculitis. Cloning efficiency was 2-5/100 seeded cells. Treg clones were homogenously CD4+CD127lowCD25highFoxP3+HELIOS+, and clonality was confirmed by staining for a unique TCR Vbeta chain. Clones maintained at least 80% suppression at a 1:4 Treg:Teff ratio over 8 weeks in in vitro culture. Expansion rate was up to 9.8 billion-fold. Our results indicate that massive expansion of human antigen-specific Treg clones is a feasible approach for the generation of large numbers of functionally stable regulatory T cells for preclinical and clinical testing.

Dendritic cells in progression and pathology of HIV infection

Although the major targets of HIV infection are CD4⁺ T cells, dendritic cells (DCs) represent a crucial subset in HIV infection because they influence viral transmission and target cell infection and presentation of HIV antigens. DCs are potent antigen-presenting cells that can modulate antiviral immune responses. Through secretion of inflammatory cytokines and interferons (IFNs), DCs also alter T cell proliferation and differentiation, participating in the immune dysregulation characteristic of chronic HIV infection. Their wide distribution in close proximity with the mucosal epithelia makes them one of the first cell types to encounter HIV during sexual transmission. We discuss here the multiple roles that DCs play at different stages of HIV infection, emphasizing their relevance to HIV pathology and progression.

Abstract 457: Matrix metalloproteinase-2 modulates antitumor immunity

Background: Cancer cells, including melanoma, can be highly resistant to traditional treatments such as chemotherapy and radiotherapy. As a result, a lot of effort has been put into developing immune therapies to treat cancer patients. The main barrier to design effective immunotherapies is the immunosuppression induced by the tumor. Matrix metalloproteinase-2 (MMP-2) is over-expressed in most cancers including melanoma, and its expression is associated with increased dissemination and poorer survival/prognosis. Here, we not only uncovered an immunosuppressive role of MMP-2 in inducing ineffective/detrimental TH2 immune responses, but also the underlying mechanisms.

Methods: Human dendritic cells (DCs) were cultured in the presence of MMP-2 and/or various TLR agonists. DCs responses were monitored using immunostaining, ELISA or cytometric bead array methods. Autologous CD4+ T cells were stimulated using these conditioned tumor-associated antigen (TAA)-pulsed DCs. TAA-specific CD4+ T cells were cloned and characterized using mainly the same techniques as for DCs.

Results: Here we showed that MMP-2-conditioned human DCs primed naïve CD4+ T cells to differentiate into an inflammatory TH2 phenotype, i.e. mainly secreting TNFα, IL-4 and IL-13 and expressing GATA3. Accordingly, we detected MMP-2-specific CD4+ T cells displaying the same inflammatory TH2 profile in tumor-infiltrating lymphocytes from melanoma patients. We revealed the underlying mechanisms: on the one hand, MMP-2 was found to degrade the type-I IFN receptor IFNAR1, thereby preventing STAT1 phosphorylation, which is necessary for IL-12 production. On the other hand, MMP-2 triggers the Toll-like receptor (TLR)-2 on DCs, which leads to NF-κB activation and OX40L expression. Both lack of IL-12 and over-expression of OX40L were found responsible for skewing T cell responses towards a detrimental TH2 phenotype.

Conclusions: MMP-2, therefore, acts as an endogenous TH2 "conditioner" and may underlie the prevalence of detrimental TH2 responses in cancer. Our findings also described the responsible MMP-2-dependent mechanisms, which open the way to novel therapeutic strategies and/or targets to skew anti-tumor CD4+ T cell responses towards a more efficient anti-tumor TH1 phenotype to treat cancer patients.

Citation Format: Emmanuelle Godefroy, Anne Gallois, Olivier Manches, Shaheen Ensanyat, Francine Jotereau, Nina Bhardwaj. Matrix metalloproteinase-2 modulates antitumor immunity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 457. doi:10.1158/1538-7445.AM2013-457

Inhibition of both BRAF and MEK in BRAF(V600E) mutant melanoma restores compromised dendritic cell (DC) function while having differential direct effects on DC properties

PURPOSE

Dendritic cells (DCs) can induce strong tumor-specific T-cell immune responses. Constitutive upregulation of the mitogen-activated protein kinase (MAPK) pathway by a BRAF(V600) mutation, which is present in about 50 % of metastatic melanomas, may be linked to compromised function of DCs in the tumor microenvironment. Targeting both MEK and BRAF has shown efficacy in BRAF(V600) mutant melanoma.

METHODS

We co-cultured monocyte-derived human DCs with melanoma cell lines pretreated with the MEK inhibitor U0126 or the BRAF inhibitor vemurafenib. Cytokine production (IL-12 and TNF-α) and surface marker expression (CD80, CD83, and CD86) in DCs matured with the Toll-like receptor 3/Melanoma Differentiation-Associated protein 5 agonist polyI:C was examined. Additionally, DC function, viability, and T-cell priming capacity were assessed upon direct exposure to U0126 and vemurafenib.

RESULTS

Cytokine production and co-stimulation marker expression were suppressed in polyI:C-matured DCs exposed to melanoma cells in co-cultures. This suppression was reversed by MAPK blockade with U0126 and/or vemurafenib only in melanoma cell lines carrying a BRAF(V600E) mutation. Furthermore, when testing the effect of U0126 directly on DCs, marked inhibition of function, viability, and DC priming capacity was observed. In contrast, vemurafenib had no effect on DC function across a wide range of dose concentrations.

CONCLUSIONS

BRAF(V600E) mutant melanoma cells modulate DC through the MAPK pathway as its blockade can reverse suppression of DC function. MEK inhibition negatively impacts DC function and viability if applied directly. In contrast, vemurafenib does not have detrimental effects on important functions of DCs and may therefore be a superior candidate for combination immunotherapy approaches in melanoma patients.

Plasma factors during chronic HIV-1 infection impair IL-12 secretion by myeloid dendritic cells via a virus-independent pathway

OBJECTIVE

Myeloid dendritic cell (mDC) dysfunction during HIV infection may hinder the formation of both innate and adaptive immune responses and contribute to pathogenesis. Our objective was to determine whether circulating factors during chronic HIV infection impair mDC function with respect to secretion of IL-12, a pro-Th1 cytokine, and T-cell stimulatory capacity. Particular focus was placed on the effect of combination antiretroviral therapy (cART) and the role of HIV itself on mDC function.

METHODS

Monocyte-derived DC (moDC) from uninfected donors were exposed to plasma from HIV-infected individuals before Toll-like receptor (TLR) stimulation. Cytokine secretion was measured via cytokine bead arrays, and T-cell proliferation and IFNγ secretion was evaluated after coculture with naive CD4 T cells. Expression of genes central to TLR-mediated signal transduction was analyzed via quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) arrays and western blot.

RESULTS

Exposure of monocyte-derived DC to plasma from untreated HIV-infected donors suppressed secretion of IL-12, and impaired Th1-skewing of CD4 T cells. The suppressive effect was less by plasma donors receiving cART. Removal of virus from plasma did not relieve suppression nor was IL-12 secretion decreased on addition of HIV to control plasma. On a transcriptional level, decreased expression of IKKβ, a key regulator in the TLR/NF-kappaB signaling pathway, corresponded to suppressed cytokine secretion.

CONCLUSIONS

Plasma factors during chronic HIV infection impair mDC function in a manner that likely impacts the formation of immune responses to HIV, opportunistic pathogens, and vaccines. Despite partial alleviation by cART, this suppression was not directly mediated by HIV.

Activation of the noncanonical NF-κB pathway by HIV controls a dendritic cell immunoregulatory phenotype

HIV modulates plasmacytoid dendritic cell (pDC) activation via Toll-like receptor 7, inducing type I IFN and inflammatory cytokines. Simultaneously, pDCs up-regulate the expression of indoleamine 2,3 dioxygenase (IDO), which is essential for the induction of regulatory T cells (Tregs), which function to down-modulate immune activation. Here we demonstrate the crucial importance of the noncanonical NF-κB pathway in the establishment of this immunoregulatory phenotype in pDCs. In response to HIV, the noncanonical NF-κB pathway directly induces IDO and involves the recruitment of TNF receptor-associated factor-3 to the Toll-like receptor/MyD88 complex, NF-κB-inducing kinase-dependent IκB kinase-α activation, and p52/RelB nuclear translocation. We also show that pDC-induced Tregs can inhibit conventional DC (cDC) maturation partially through cytotoxic T-lymphocyte antigen (CTLA)-4 engagement. Furthermore, CTLA-4 induces IDO in cDCs in a NF-κB-inducing kinase-dependent way. These CTLA-4-conditioned cDCs can in turn induce Treg differentiation in an IDO-dependent manner. Thus, the noncanonical NF-κB pathway is integral in controlling immunoregulatory phenotypes of both pDCs and cDCs.

Effect of matrix metalloproteinase-2 on CD8+ T cell and NK cell responses

e21081

Background: Matrix metalloproteinase 2 (MMP-2) cleaves many components of the extracellular matrix and is over-expressed in several cancers including melanoma. High levels of MMP-2 expressed by tumors are associated with later tumor stages, increased dissemination and poorer survival/prognosis. We recently identified a pathway whereby MMP-2 functions as a human endogenous “conditioner” that skews CD4+ T cells towards a detrimental/inefficient TH2 phenotype through OX40L expression and inhibition of IL-12p70 production. We unraveled the underlying mechanism: MMP-2 degrades the type I IFN receptor (IFNAR1), thereby preventing STAT1 phosphorylation necessary for IL-12 production. Here, we described IFNAR1 as a novel MMP-2 substrate. This finding opens the way to characterize a possible new immunosuppressive effect of MMP-2 on other IFNAR1+ immune cells such as NK cells and CD8+ T cells. Methods: CD8+ T cells and NK cells were purified from PBMCs and incubated with MMP-2 overnight. IFNAR1 expression was assessed by FACS and Western Blot. Granzyme B, TNF alpha and IFN gamma expression was determined by intracellular staining of memory T cells. NK cells cytotoxicity was measured by Lamp-1 expression after 4h of coculture with K562 cells. Results: We first found that IFNAR1 is expressed by NK and CD8+ T cells and confirmed that MMP-2 degraded it. Memory CD8+ T cells significantly down-regulate granzyme B expression in the presence of MMP-2. Furthermore, memory CD8+ T cells pre-incubated with MMP-2 were significantly impaired with respect to IFN-gamma and TNF-alpha production. Finally, our data suggest that NK cells’ cytotoxicity might also be affected by MMP-2 through modulation of Granzyme B production. Conclusions: Our data strongly suggest that MMP-2 regulates memory CD8+ T cells not only by down regulating cytolytic activity through inhibition of granzyme B, but also by inhibiting cytokine production such as IFN-gamma and TNF-alpha. Elucidating the underlying mechanisms of MMP-2-dependent immune regulation should lead to the development of innovative immune therapies bypassing tumor escape to treat cancer patients.

Effect of matrix metalloproteinase-2 on antitumor immunity

2570

Background: Cancer cells, including melanoma, can be highly resistant to traditional treatments such as chemotherapy and radiotherapy. As a result, a lot of effort has been put into developing immune therapies to treat cancer patients. The main barrier to design effective immunotherapies is the immunosuppression induced by the tumor. Matrix metalloproteinase-2 (MMP-2) is over-expressed in most cancers including melanoma, and its expression is associated with increased dissemination and poorer survival/prognosis. Here, we uncovered an immunosuppressive role of MMP-2 in inducing ineffective/detrimental TH2 immune responses and its underlying mechanisms. Methods: Human dendritic cells (DCs) were cultured in the presence of MMP-2 or various TLR agonists. DCs responses were monitored using immunostaining, ELISA or cytometric bead array methods. Autologous CD4+ T cells were stimulated using these conditioned tumor-associated antigen (TAA)-pulsed DCs. TAA-specific CD4+ T cells were cloned and characterized using the same techniques as for DCs. Results: Herewe showed that MMP-2-conditioned human DCs primed naïve CD4+ T cells into an inflammatory TH2 phenotype, i.e. mainly secreting TNFα, IL-4 and IL-13 and expressing GATA3. Accordingly, we detected MMP-2-specific CD4+ T cells displaying the same inflammatory TH2 profile in tumor-infiltrating lymphocytes from melanoma patients. We revealed the underlying mechanisms: on the one hand, MMP-2 was found to degrade the type-I IFN receptor IFNAR1, thereby preventing STAT1 phosphorylation, which is necessary for IL-12 production. On the other hand, MMP-2 triggers the Toll-like receptor (TLR)-2 on DCs, which leads to NF-kB activation and OX40L expression. Both lack of IL-12 and over-expression of OX40L were found responsible for skewing T cell responses towards a detrimental TH2 phenotype. Conclusions: MMP-2, therefore, acts as an endogenous TH2 "conditioner" and may underlie the prevalence of detrimental TH2 responses in cancer. Our findings also described the responsible MMP-2-dependent mechanisms, which open the way to novel therapeutic strategies and/or targets to skew anti-tumor CD4+ T cell responses towards a more efficient anti-tumor TH1 phenotype to treat cancer patients.

CD11b/CD18 ligation on monocyte-derived dendritic cells dampens human Th17 cell responses (52.6)

Manipulating monocyte-derived DC (moDC) to alter effector T cell responses is an important strategy for the development of suppressive immunotherapy. We have previously shown that the ligation of CD11b/CD18 on moDC decreases the secretion of the Th17-skewing inflammatory cytokines IL-1β and IL-6, but maintains “immunosuppressive” TGF-β1. Here, we hypothesized that this “tolerogenic” DC-profile would diminish Th17 responses in peripheral human T cell populations. Healthy donor PBMC were differentiated into moDC in IL-4, GM CSF-supplemented media for 5 days. CD11b/CD18 on moDC was targeted via a bead-based surrogate system developed in our lab. Irrelevant IgG, or avb5, and beads without antibodies were used as controls. DC were stimulated with LPS and MDP or PGN or not stimulated, and then co-cultured with enriched CD4+ human T memory cells. IL-17 secretion was monitored per CBA after 24 hours and/or 4 days, and Th17 frequency assessed by ICS following restimulation with PMA/Ionomycin after 2 weeks. LPS/MDP or PGN-stimulated moDC induced significant increases in co-culture supernatant IL-17 levels and CD4+ Th17 cell frequencies (up to15%). Strikingly, these changes were significantly reduced in CD11b/CD18-ligated DC/T cell conditions, showing reversal of this NOD2/TLR4 or TLR2-mediated expansion effect though ligation of CD11b/CD18 on moDC.

Abstract SY40-02: Interplay between microenvironment and cancers

Tumors are highly adept at evading the immune system through a multitude of mechanisms, including the secretion of factors that modulate both innate and adaptive immunity. Matrix metalloproteinase-2 (MMP-2) is a proteolytic enzyme that degrades the extracellular matrix and is over expressed by many tumors, including melanoma. We recently documented the presence of MMP-2-specific CD4(+) T cells in tumor-infiltrating lymphocytes (TILs) in several melanoma patients (Cancer Cell 19:333, 2011). Strikingly, MMP-2-specific CD4(+) T cells displayed an inflammatory T(H)2 profile, mainly TNF-α, IL-4, and IL-13 and expressing GATA-3. When exposed to MMP-2, immature human dendritic cells (DCs) primed naïve CD4(+) T cells to differentiate into an inflammatory T(H)2 phenotype through OX40L expression and inhibition of IL-12p70 production. MMP-2 was subsequently found to degrade the type I IFN receptor, thereby preventing STAT1 phosphorylation, which is necessary for IL-12p35 production, and the subsequent formation of bioactive IL-12. More recently we have explored the mechanisms underlying the up regulation of OX40L and have identified signaling pathways and potential receptors that lead to this modulation. Active MMP-2, therefore, acts as an endogenous type 2 “conditioner” providing an explanation for the observed prevalence of detrimental type 2 responses in melanoma. Novel properties of MMP-2 on other components of the immune system, and on tumor progression, will be discussed along with DC-based strategies to alleviate immune suppression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr SY40-02. doi:1538-7445.AM2012-SY40-02

TLR4 engagement during TLR3-induced proinflammatory signaling in dendritic cells promotes IL-10-mediated suppression of antitumor immunity

Toll-like receptor (TLR) agonists are promising adjuvants for immune therapy of cancer, but their potential efficacy as single or combinatorial agents has yet to be fully evaluated. Here, we report that among all TLR agonists tested, dendritic cells (DC) stimulated with the TLR3 agonist polyI:C displayed the strongest activity in stimulating proinflammatory responses and the production of melanoma antigen-specific CD8(+) T cells. Simultaneous treatment with TLR7/8 agonists further improved these responses, but the inclusion of bacterial lipopolysaccharide (LPS), a TLR4 agonist, suppressed proinflammatory cytokine production. This inhibition was contingent upon rapid induction of the suppressive cytokine interleukin (IL)-10 by LPS, leading to dysregulated immune responses and it could be reversed by signal transducers and activators of transcription 3 knockdown, p38 blockade or antibodies to IL-10 and its receptor. Our findings show how certain TLR agonist combinations can enhance or limit DC responses associated with antitumor immunity, through their relative ability to induce IL-10 pathways that are immune suppressive.

Matrix metalloproteinase-2 conditions human dendritic cells to prime inflammatory T(H)2 cells via an IL-12- and OX40L-dependent pathway

Matrix metalloproteinase-2 (MMP-2) is a proteolytic enzyme degrading the extracellular matrix and overexpressed by many tumors. Here, we documented the presence of MMP-2-specific CD4(+) T cells in tumor-infiltrating lymphocytes (TILs) from melanoma patients. Strikingly, MMP-2-specific CD4(+) T cells displayed an inflammatory T(H)2 profile, i.e., mainly secreting TNF-α, IL-4, and IL-13 and expressing GATA-3. Furthermore, MMP-2-conditioned dendritic cells (DCs) primed naïve CD4(+) T cells to differentiate into an inflammatory T(H)2 phenotype through OX40L expression and inhibition of IL-12p70 production. MMP-2 degrades the type I IFN receptor, thereby preventing STAT1 phosphorylation, which is necessary for IL-12p35 production. Active MMP-2, therefore, acts as an endogenous type 2 "conditioner" and may play a role in the observed prevalence of detrimental type 2 responses in melanoma.

Spatiotemporal trafficking of HIV in human plasmacytoid dendritic cells defines a persistently IFN-α-producing and partially matured phenotype

Plasmacytoid DCs (pDCs) are innate immune cells that are specialized to produce IFN-α and to activate adaptive immune responses. Although IFN-α inhibits HIV-1 replication in vitro, the production of IFN-α by HIV-activated pDCs in vivo may contribute more to HIV pathogenesis than to protection. We have now shown that HIV-stimulated human pDCs allow for persistent IFN-α production upon repeated stimulation, express low levels of maturation molecules, and stimulate weak T cell responses. Persistent IFN-α production by HIV-stimulated pDCs correlated with increased levels of IRF7 and was dependent upon the autocrine IFN-α/β receptor feedback loop. Because it has been shown that early endosomal trafficking of TLR9 agonists causes strong activation of the IFN-α pathway but weak activation of the NF-κB pathway, we sought to investigate whether early endosomal trafficking of HIV, a TLR7 agonist, leads to the IFN-α-producing phenotype we observed. We demonstrated that HIV preferentially traffics to the early endosome in human pDCs and therefore skews pDCs toward a partially matured, persistently IFN-α-secreting phenotype.

Resolution of immune activation defines nonpathogenic SIV infection

Natural nonhuman primate hosts of SIV do not succumb to AIDS despite significant viral replication, a phenomenon attributed to reduced levels of chronic and deleterious "immune activation." Two studies in this issue of the JCI, by Bosinger et al. and Jacquelin et al., now show that SIV induces vigorous immune activation and upregulation of IFN-stimulated genes in both natural and susceptible hosts, but strikingly, the responses resolve only in the former (see the related articles, beginning on pages 3556 and 3544, respectively). Thus, natural hosts for SIV actively engage mechanisms to abort sustained immune activation and its associated harmful effects.

Whole lymphoma B cells allow efficient cross-presentation of antigens by dendritic cells

BACKGROUND

In order to compensate for the paucity of defined tumor antigens (Ag) in non-Hodgkin's lymphomas, a promising approach might be the use of whole tumor cells as a source of tumor Ag to pulse antigen-presenting cells (APC). However, it is not presently known how the tumor cells should be delivered to APC to optimize the cross-presentation of tumor Ag to anti-tumor CD8 T cells. We aimed to compare CD20-opsonized, apoptotic and necrotic human tumor cells for their capacity to induce endocytosis and cross-presentation of tumor-associated Ag by dendritic cells (DC) or macrophages.

METHODS

Endocytosis of human tumor-derived material by macrophages or DC was monitored by flow cytometry. We used a previously described influenza model and studied cross-presentation of viral Ag as cellular surrogate tumor-associated Ag by APC after endocytosis of lymphoma B cells treated by inactivated influenza virus.

RESULTS

Optimal endocytosis was obtained when tumor cells were opsonized by an anti-CD20 antibody and, as expected, macrophages were more phagocytic than DC. However, Ag from opsonized, apoptotic and live cells, but not from necrotic lymphoma cells, were efficiently cross-presented by DC but not by macrophages.

DISCUSSION

We have developed a new model with human primary lymphoma cells to study the cross-presentation of tumor-associated Ag by APC. The results we have obtained support the use of whole lymphoma cells from patients to pulse DC to induce an anti-tumor immune response.

HIV-activated human plasmacytoid DCs induce Tregs through an indoleamine 2,3-dioxygenase-dependent mechanism

Plasmacytoid DCs (pDCs) have been implicated as crucial cells in antiviral immune responses. On recognizing HIV, they become activated, secreting large amounts of IFN-alpha and inflammatory cytokines, thereby potentiating innate and adaptive antiviral immune responses. Here, we have shown that HIV-stimulated human pDCs can also induce the differentiation of naive CD4+ T cells into Tregs with suppressive function. This differentiation was independent of pDC production of IFN-alpha and primarily dependent on pDC expression of indoleamine 2,3-dioxygenase, which was induced through the TLR/MyD88 pathway, following binding of HIV to CD4 and triggering of TLR7 by HIV genomic RNA. Functionally, the Tregs induced by pDCs were shown to inhibit the maturation of bystander conventional DCs. This study therefore reveals what we believe to be a novel mechanism by which pDC may regulate and potentially limit anti-HIV immune responses.

Immunization of malignant melanoma patients with full-length NY-ESO-1 protein using TLR7 agonist imiquimod as vaccine adjuvant

T cell-mediated immunity to microbes and to cancer can be enhanced by the activation of dendritic cells (DCs) via TLRs. In this study, we evaluated the safety and feasibility of topical imiquimod, a TLR7 agonist, in a series of vaccinations against the cancer/testis Ag NY-ESO-1 in patients with malignant melanoma. Recombinant, full-length NY-ESO-1 protein was administered intradermally into imiquimod preconditioned sites followed by additional topical applications of imiquimod. The regimen was very well tolerated with only mild and transient local reactions and constitutional symptoms. Secondarily, we examined the systemic immune response induced by the imiquimod/NY-ESO-1 combination, and show that it elicited both humoral and cellular responses in a significant fraction of patients. Skin biopsies were assessed for imiquimod's in situ immunomodulatory effects. Compared with untreated skin, topical imiquimod induced dermal mononuclear cell infiltrates in all patients composed primarily of T cells, monocytes, macrophages, myeloid DCs, NK cells, and, to a lesser extent, plasmacytoid DCs. DC activation was evident. This study demonstrates the feasibility and excellent safety profile of a topically applied TLR7 agonist used as a vaccine adjuvant in cancer patients. Imiquimod's adjuvant effects require further evaluation and likely need optimization of parameters such as formulation, dose, and timing relative to Ag exposure for maximal immunogenicity.

Imiquimod: A TLR-7 agonist as adjuvant for a recombinant protein cancer vaccine

8545

Purpose: This clinical trial evaluates the safety and adjuvant activity of imiquimod, a toll-like receptor (TLR)-7 agonist, when given with a NY-ESO-1 protein vaccine. Imiquimod, by locally activating and recruiting dendritic cells (DCs) into the skin, is expected to stimulate antigen uptake by DCs, induce maturation and migration to draining lymph nodes, and to induce antigen-specific T and B cell immunity. Methods: Pilot study; 9 patients with resected stage 2B-3C malignant melanoma. Four 21 day cycles consisted of topical imiquimod cream (250 mg) on days 1–5 and id. injected NY-ESO-1 protein (100 mcg) into the site on day 3. Blood was drawn at several time points for immune monitoring; skin punch biopsies were obtained from control, imiquimod and vaccination sites 48 hours after the last vaccination. Results: The regimen was tolerated well, all patients completed four vaccinations. AEs were mild and transient and included injection site reactions (8/9 patients), fatigue (4/9 patients) and fever (2/9 patients). Significant levels of antigen-specific CD4+ or CD8+ T cell responses were not detected in ex-vivo ELISPOT assays. However, intracellular cytokine staining assays after in vitro pre-stimulation indicated that 6 of 8 subjects developed NY-ESO-1 CD4+ T cell responses. Humoral immunity was manifest by the induction of anti-NY-ESO-1 antibodies in 7/9 patients post-vaccination. Histochemistry of skin sections showed significant dermal mononuclear cell infiltrates in Imiquimod treated skin, whereas none were seen in untreated skin (p<0.01). IHC revealed markedly increased numbers of CD3+ (T-cells), CD68+ (macrophages/monocytes), CD123+ (plasmacytoid DCs) and DC-LAMP+ (mature myeloid DCs) immune cells in Imiquimod treated skin when compared with control skin of the same patients (p<0.05). Conclusion: Imiquimod, a topical immune response modifier, generated clear inflammatory infiltrates in the dermis, with significant increases in antigen-presenting cells and T cells. Imiquimod was well tolerated when used as an adjuvant to an NY-ESO-1 protein vaccine. Systemic immunity of both humoral and cellular types was induced in the majority of patients; however, responses were weak and the vaccine combination needs to be optimized in future studies.

No significant financial relationships to disclose.

Development of autologous cytotoxic CD4+T clones in a human model of B-cell non-Hodgkin follicular lymphoma

Immunotherapy for cancer aims to generate cytotoxic cells that are capable of eradicating tumour cells. It has been well demonstrated that helper, non-cytotoxic CD4(+) T cells are important for the induction and maintenance of anti-tumour immunity exerted by cytotoxic CD8(+) T cells. In contrast, the existence of direct anti-tumour, effector cytotoxic CD4(+) T cells remains elusive, mainly due to the paucity of reliable experimental data, especially in human B-cell non-Hodgkin lymphomas. This study developed an appropriate, autologous follicular B-cell non-Hodgkin follicular lymphoma model, including the in vitro establishment of a malignant, human leucocyte antigen class I (HLA-I) deficient B-cell line, and the generation of three autologous anti-tumour cytotoxic CD4(+) T-cell clones originating from the peripheral blood of the same patient. These three clones were considered as tumour specific, because they were capable of killing the malignant, HLA-I-deficient B-cell line through a classical HLA-II restricted perforin-mediated pathway, but did not lyse the Epstein-Barr virus-infected autologous normal B lymphocytes. All three CD4(+)clones were T-cell receptor Vbeta17-Dbeta1-Jbeta1.2 and exhibited an identical complementarity-determining region 3, suggesting the immunodominance of a single peptide antigen presented by tumour cells. Such lymphoma models would provide a useful tool for in vivo expansion and the adoptive transfer of selected CD4(+) cytotoxic cells in immunotherapeutic strategies.

Virus or TLR agonists induce TRAIL-mediated cytotoxic activity of plasmacytoid dendritic cells

Among dendritic cells, plasmacytoid dendritic cells (PDC) represent a functionally distinct lineage. Regarding innate immunity, PDC secrete large amounts of type I IFN upon viral exposure or stimulation by microbial products such as unmethylated CpG-motif containing oligo-DNA due to their selective expression of TLR7 and TLR9. We asked whether they could acquire cytotoxic functions during the early phases of infection or after activation with TLR7 or TLR9 agonists. In the present study, we describe a human PDC cell line called GEN2.2, derived from leukemic PDC, that shares most of the phenotypic and functional features of normal PDC. We show that after contact with the influenza virus, GEN2.2, as well as normal PDC, acquires TRAIL and killer activity against TRAIL-sensitive target cells. Moreover, we show that activation of GEN2.2 cells by CpG-motif containing oligo-DNA or R848 also induces TRAIL and endows them with the ability to kill melanoma cells. Therefore, PDC may represent a major component of innate immunity that could participate to the clearance of infected cells and tumor cells. This phenomenon could be relevant for the efficacy of TLR7 or TLR9 agonists in the therapy of infectious disease and cancer.

Endocytosis of HIV-1 activates plasmacytoid dendritic cells via Toll-like receptor-viral RNA interactions

HIV-1 directly activates human plasmacytoid DCs (pDCs) by upregulating the expression of costimulatory and MHC molecules and maturation markers, increasing T cell stimulatory activity, and inducing the production of type I interferons and TNF-alpha. A consequence of this activation is the bystander maturation of myeloid DCs and overall enhancement of antigen-presenting function. However, little is known about the mechanism(s) of pDC activation by HIV-1. Here we demonstrate by in vitro studies that IFN-alpha production by pDC in response to HIV-1 requires at least 2 interactions between the cell and virus. Initially, envelope-CD4 interactions mediate endocytosis of HIV-1, as demonstrated through the use of inhibitors of binding, fusion, endocytosis, and endosomal acidification. Subsequently, endosomally delivered viral nucleic acids, particularly RNA, stimulate pDCs through TLRs, as activation is reproduced with purified genomic RNA but not viral RNA packaging-deficient HIV-1 and blocked with different inhibitory TLR ligands. Finally, by using genetic complementation, we show that TLR7 is the likely primary target. Viral RNA rather than DNA in early retrotranscripts appears to be the active factor in HIV-1 that induces IFN-alpha secretion by pDCs. Since the decline in pDCs in chronic HIV-1 infection is associated with high viral loads and opportunistic infections, exploiting this natural adjuvant activity of HIV-1 RNA might be useful in the development of vaccines for the prevention of AIDS.

Human cytomegalovirus downregulates complement receptors (CR3, CR4) and decreases phagocytosis by macrophages

Human cytomegalovirus (HCMV) infection is associated with an increased susceptibility to opportunistic infections. Although the subversion of adaptive immune responses has been extensively studied, the consequences of HCMV infection on natural immune responses are not well documented. A striking selective downmodulation of CD11b/CD18 (CR3) or CD11c/CD18 (CR4) was found upon HCMV infection, on two models, the monocytic THP-1 cell line and monocyte- derived macrophages. HCMV-infected macrophages have an altered adhesion/phagocytic capacity to Candida albicans, a pathogen responsible for some opportunistic infections in immunocompromised patients. These results suggest a new mechanism implicated in the augmentation of opportunistic infections in HCMV patients.

Anti-Gal-mediated targeting of human B lymphoma cells to antigen-presenting cells: a potential method for immunotherapy using autologous tumor cells

BACKGROUND AND OBJECTIVES

The residual tumor cells remaining after completion of standard chemotherapy and radiation treatment in B lymphoma patients, may be eradicated by active immunotherapy that stimulates tumor-specific T lymphocytes. Irradiated autologous lymphoma cells expressing tumor-associated antigens (TAA) may serve as a potential tumor vaccine, provided that they are effectively targeted to the antigen-presenting cells (APC). We propose exploiting the natural anti-Gal antibody in order to target vaccinating tumor cells to APC. Anti-Gal constitutes 1% of IgG in human serum and interacts specifically with the alpha-gal epitope (Galalpha1-3Galphalbeta1-4GlcNAc-R).

DESIGN AND METHODS

Alpha-gal epitopes were synthesized in vitro on the membrane of primary lymphoma cells by using the recombinant glycosylation enzyme alpha1,3galactosyltransferase (alpha1,3GT). Processed tumor cells were opsonized by purified anti-Gal antibodies and studied for uptake (phagocytosis) by APC including monocyte-derived macrophages and dendritic cells. Cross-presentation of tumor antigens after phagocytosis of processed MHC-I negative lymphoma cells was measured by activation of a tumor-specific CD8+ T-cell line.

RESULTS

We demonstrate synthesis of alpha-gal epitopes on freshly isolated B lymphoma cells of various types following the use of the recombinant enzyme alpha1,3GT. The subsequent binding of anti-Gal to the de novo synthesized alphagal epitopes opsonizes these tumor cells for effective uptake by macrophages and dendritic cells, through phagocytosis mediated by FcgammaR1 (CD64). Moreover, anti-Gal-mediated phagocytosis resulted in cross-presentation of TAA by dendritic cells.

INTERPRETATION AND CONCLUSIONS

This study suggests that immunization with irradiated autologous lymphoma cells processed to express alpha-gal epitopes will result in anti-Gal-mediated, in vivo targeting of the autologous tumor vaccine to APC.

Preparation of purified lymphoma cells suitable for therapy

BACKGROUND

Very few tumoral Ags have yet been isolated in NHL B cells. It is nevertheless possible to use whole tumor cells as a source of tumor Ags. We describe the purification of large numbers of human NHL B cells directly from lymph node or spleen biopsies, and different preparations allowing their use in a clinical setting.

METHODS

The purification procedure consists of the negative selection of tumor B cells: cells to be eliminated are opsonized by CD2 Abs, and then coupled to magnetic beads for separation by the Isolex 300 magnetic separator.

RESULTS

The mean yield of the purification was 74% for CD19+ cells, with a mean purity of 87%, dependent on the initial fraction of tumor cells in the biopsy. Using this procedure, a large number of purified tumor cells can be recovered from a biopsy in sterile conditions. We also describe treatments of B cells that can enhance their uptake by APCs, a critical step in anti-tumor immunotherapy strategies. Cells were opsonized by rituximab, or induced in apoptosis by irradiation, or necrosis by heating. Cell lysates were directly prepared from purified tumor cells.

DISCUSSION

These procedures were reproducible on every lymphoma cell, and treated cells were phagocytosed by APCs. The methodology described here allows the evaluation of the immunological potential of apoptotic, necrotic, opsonized lymphoma cells, or their lysates, in a clinical setting.

Nelfinavir Induces Necrosis of 3T3F44-2A Adipocytes by Oxidative Stress

Protease inhibitor treatment strongly diminishes mortality in HIV-infected patients. This treatment has also been associated with lipodystrophy and has been shown to alter adipocyte differentiation. The protease inhibitor nelfinavir has been indirectly implicated in the appearance and development of lipodystrophic syndrome, as well as in adipocyte cell death. The aim of this study was to evaluate the effects of nelfinavir on the 3T3-F442A adipocyte cell line. Nelfinavir (30 microM) induced cell death of 3T3-F442A adipocytes by a necrotic process that was not mediated by TNF-alpha. Treatment of cells with this protease inhibitor led to a significant increase in expression of the heme oxygenase-1 gene that could be reduced by 100 microM of the antioxidant ascorbate. Moreover, ascorbate had a protective effect on nelfinavir-induced necrosis, decreasing the percentage of necrotic cells by 70%. Our results show that nelfinavir induces necrosis of adipocytes mediated by a cellular increase of reactive oxygen species. This deleterious effect could be counterbalanced by ascorbate.

Mechanisms of action of extracorporeal photochemotherapy in the control of GVHD: involvement of dendritic cells

Despite the fact that extracorporal photochemotherapy (ECP) is now broadly used for the treatment of graft versus host disease or T-cell lymphomas, the mechanisms of its action remain enigmatic. This work provides a synthesis of the main results suggesting the initiation by ECP of an immune reaction responsible for the down modulation of pathogenic T-cell functions, with a special focus on the role of dendritic cells in this phenomenon.

Quality control for the validation of extracorporeal photopheresis process using the Vilbert-Lourmat UV-A irradiation's system

In agreement with good practices for therapeutic use of human cells, quality control has to be performed to valid the process of extracorporeal photopheresis (ECP) with the Vilbert-Lourmat system. Since no protocol exists, we evaluated a technique based on the measurement of the inhibition of mitogen (PHA, Con-A, OKT3)-induced proliferation, in 164 procedures from 16 patients. Whatever the pathology, we observed a high proliferation rate in most samples, and we obtained over 90% ECP-induced inhibition in as many as 94% of the cases. Since this approach proved to be relevant regarding our objective, a protocol for the ECP process validation is proposed.