The Fusion Protein rFlaA:Betv1 Modulates DC Responses by a p38-MAPK and COX2-Dependent Secretion of PGE2 from Epithelial Cells

Developing new adjuvants/vaccines and better understanding their mode-of-action is an important task. To specifically improve birch pollen allergy treatment, we designed a fusion protein consisting of major birch pollen allergen Betv1 conjugated to the TLR5-ligand flagellin (rFlaA:Betv1). This study investigates the immune-modulatory effects of rFlaA:Betv1 on airway epithelial cells. LA-4 mouse lung epithelial cells were stimulated with rFlaA:Betv1 in the presence/absence of various inhibitors with cytokine- and chemokine secretion quantified by ELISA and activation of intracellular signaling cascades demonstrated by Western blot (WB). Either LA-4 cells or LA-4-derived supernatants were co-cultured with BALB/c bone marrow-derived myeloid dendritic cells (mDCs). Compared to equimolar amounts of flagellin and Betv1 provided as a mixture, rFlaA:Betv1 induced higher secretion of IL-6 and the chemokines CCL2 and CCL20 from LA-4 cells and a pronounced MAPK- and NFκB-activation. Mechanistically, rFlaA:Betv1 was taken up more strongly and the induced cytokine production was inhibited by NFκB-inhibitors, while ERK- and p38-MAPK-inhibitors only suppressed IL-6 and CCL2 secretion. In co-cultures of LA-4 cells with mDCs, rFlaA:Betv1-stimulated LA-4 cells p38-MAPK- and COX2-dependently secreted PGE2, which modulated DC responses by suppressing pro-inflammatory IL-12 and TNF-α secretion. Taken together, these results contribute to our understanding of the mechanisms underlying the strong immune-modulatory effects of flagellin-containing fusion proteins.

A Pan-Cancer Analysis of the Oncogenic and Immunogenic Role of m6Am Methyltransferase PCIF1

BackgroundPhosphorylated CTD-interacting factor 1 (PCIF1) is identified as the only known methyltransferase of N6,2′-O-dimethyladenosine (m6Am) in mRNA. However, its oncogenic and immunogenic role in cancer research is at an initial stage.MethodsHerein, we carried out a pan-cancer analysis of PCIF1, with a series of datasets (e.g., TIMER2.0, GEPIA2, cBioPortal).ResultsPCIF1 expression was higher in most cancers than normal tissues and was discrepant across pathological stages. Highly expressed PCIF1 was positively correlated with overall survival (OS) or disease-free survival (DFS) of some tumors. PCIF1 expression had a positive correlation with CD4+ T-cell infiltration in kidney renal clear cell carcinoma (KIRC), CD8+ T cells, macrophages, and B cells in thyroid carcinoma (THCA), and immune checkpoint genes (ICGs) in LIHC but a negative correlation with CD4+ T cells, neutrophils, myeloid dendritic cells, and ICGs in THCA. It also affected tumor mutational burden (TMB) and microsatellite instability (MSI) of most tumors.ConclusionPCIF1 expression was correlated with cancer prognosis and immune infiltration, suggesting it to be a potential target for cancer therapy.

Isoform specific anti-TGFβ therapy enhances antitumor efficacy in mouse models of cancer

TGFβ is a potential target in cancer treatment due to its dual role in tumorigenesis and homeostasis. However, the expression of TGFβ and its inhibition within the tumor microenvironment has mainly been investigated in stroma-heavy tumors. Using B16 mouse melanoma and CT26 colon carcinoma as models of stroma-poor tumors, we demonstrate that myeloid/dendritic cells are the main sources of TGFβ1 and TGFβ3. Depending on local expression of TGFβ isoforms, isoform specific inhibition of either TGFβ1 or TGFβ3 may be effective. The TGFβ signature of CT26 colon carcinoma is defined by TGFβ1 and TGFβ1 inhibition results in tumor delay; B16 melanoma has equal expression of both isoforms and inhibition of either TGFβ1 or TGFβ3 controls tumor growth. Using T cell functional assays, we show that the mechanism of tumor delay is through and dependent on enhanced CD8+ T cell function. To overcome the local immunosuppressive environment, we found that combining TGFβ inhibition with immune checkpoint blockade results in improved tumor control. Our data suggest that TGFβ inhibition in stroma poor tumors shifts the local immune environment to favor tumor suppression.

Pyruvate Kinase M2 Regulates Hif-1alpha Activity in Myeloid Dendritic Cells from Patients with Severe Aplastic Anemia

Hypoxia-inducible factor 1 (HIF-1) is a nuclear protein with transcriptional activity. HIF-1 can be activated by immune cells exposed to hypoxia and regulate glycolysis. In this regulation, pyruvate kinase M2 (PKM2), a key enzyme in the cell glycolytic pathway, is an important regulatory site. Our previous studies suggest that PKM expression is increased in myeloid dendritic cells (mDCs) in SAA patients. Therefore, we investigated the expression level of HIF-1α in mDCs and its interaction with PKM2 in SAA patients. The HIF-1α expression of mRNA and protein on mDCs in SAA untreated patients was significantly higher than that in SAA remission patients and normal controls. In the SAA patients, the HIF-1α expression on mDCs was positively correlated with the numbers of mDCs (p < 0.01), CD80+mDC/mDC (r = 0.689, p < 0.01), and CD86+mDC/mDC in PB (p < 0.05). In SAA patients, the HIF-1α expression on mDCs was negatively correlated with the CD4+T/CD8+T ratio in peripheral blood (PB) (p < 0.05), the percentage of granulocytoid and erythroid cells in bone marrow (p < 0.05), the WBC count in PB (p < 0.05), ANC in PB (p < 0.05), and the percentage of Rets in the PB (p < 0.05); was positively correlated with the percentage of lymphoid cells in bone marrow(p < 0.05); and was not statistically correlated with the megakaryocyte number in bone marrow, absolute PBL count, HGB in PB, absolute Ret count in PB, or PLT count in PB. In the correlation analysis we observed that there was a positively correlation between HIF-1α and PKM2 expression on mDCs in SAA patients (p < 0.001). To evaluate whether there is a mutual adjustment relationship between HIF-1α and PKM2, we successfully reduced PKM2 gene expression in this cell population via siRNA transfection. This process resulted in significantly lower levels of PKM2 protein expression relative to cells transfected with siControl which were evaluated by western blotting. We observed that the relative expression levels of HIF-1α mRNA in mDCs transfected with PKM2 siRNA was lower than siControl group（P< 0.01）. Conclusions In this study, we found that untreated patients with SAA had higher HIF-1α expression on mDCs compared with recovering SAA patients and normal controls. The expression of HIF-1α was correlated with the number and function in mDCs and the severity of pancytopenia of SAA. The results indicated that the mRNA expression level of HIF-1α in mDC of SAA patients at the onset was significantly higher than that of the remission group and the control group, and was significantly positively correlated with the expression of PKM2. The mRNA expression level of HIF-1α in mDC of SAA patients at the onset was significantly higher than that of the remission group and the control group, and was significantly positively correlated with the expression of PKM2. The above experimental results confirmed that HIF-1α plays an important role in the abnormal immune response in patients with severe aplastic anemia, mainly by regulating the activity of PKM2 and thereby affecting the energy metabolism in immune cells. Disclosures No relevant conflicts of interest to declare.

Impaired Dendritic Cell Homing in COVID-19

The high mortality of COVID-19 is mostly attributed to acute respiratory distress syndrome (ARDS), whose histopathological correlate is diffuse alveolar damage (DAD). Furthermore, severe COVID-19 is often accompanied by a cytokine storm and a disrupted response of the adaptive immune system. Studies aiming to depict this dysregulation have mostly investigated the peripheral cell count as well as the functionality of immune cells. We investigated the impact of SARS-CoV-2 on antigen-presenting cells using multiplexed immunofluorescence. Similar to MERS-CoV and SARS-CoV, SARS-CoV-2 appears to be impairing the maturation of dendritic cells (DCs). DC maturation involves a switch in surface antigen expression, which enables the cells' homing to lymph nodes and the subsequent activation of T-cells. As quantitative descriptions of the local inflammatory infiltrate are still scarce, we compared the cell population of professional antigen-presenting cells (APC) in the lungs of COVID-19 autopsy cases in different stages of DAD. We found an increased count of myeloid dendritic cells (mDCs) in later stages. Interestingly, mDCs also showed no significant upregulation of maturation markers in DAD-specimens with high viral load. Accumulation of immature mDCs, which are unable to home to lymph nodes, ultimately results in an inadequate T-cell response.

378 Efficacy, safety and ancillary analyses of pembrolizumab in combination with nintedanib for the treatment of patients with relapsed advanced mesothelioma

BackgroundWe report the results from the advanced malignant mesothelioma (aMM) expansion cohort of the PEMBIB Phase Ib trial (NCT02856425) evaluating the safety, efficacy & biomarkers of an antiangiogenic tyrosine kinase inhibitor (nintedanib) with an anti-PD1 immunotherapy (pembrolizumab).MethodsPatients with aMM relapsing after at least one line of platinum doublet chemotherapy and not previously pre-exposed to IO were treated with a combination of oral nintedanib (150mg BID) & IV pembrolizumab (200mg Q3W) with a 7 days nintedanib lead-in preceding pembrolizumab initiation. Baseline and on-treatment (cycle D2, day 1 [C2D1]) fresh tumor & blood samples were prospectively phenotyped by flow cytometry (FC). RNAseq was run on tumor samples. Immune factors were titrated on tumor secretome and plasma.Results30 aMM patients were treated and 29 evaluable for response. Median age was 68 years old (38–85) and 86% of aMM were epithelioid. The most frequent adverse events (AE) (grades 1–3) related to the combination were liver enzymes increase, fatigue, nausea, and diarrhea. 4 (13.3%) patients developed grade 3–5 immune- related AE. Patients died of cancer progression (n=14, 46.7%), myocarditis with thrombo-embolic event (n=1, 3.3%) and COVID-19 (n=1, 3.3%). Median follow-up was 14.8 months (95%CI [9.70–18.2]). Best Overall Response Rates (BORR) per RECISTv1.1 were Partial Response (PR, n=7/29; 24.1%), Stable Disease (SD, n=17/29; 58.6%) and Progressive Disease (n=5/29; 17.2%). Disease Control Rate (DCR) (defined as PR + SD) was 46.6% at 6 months. Patients with DCR at 6 months had significantly higher percentage of PDL1 expression on tumor cells (by Immuno-Histo-Chemistry, antibody clone SP263) and higher CD8+ T cells infiltrate in tumor biopsies (by FC) at screening. Upon treatment, soluble plasma rate of CXCL9 and CXCL13 increased in all patients, as well as tumor immune infiltrates estimated by deconvolution of tumor biopsies RNA-seq. But deconvoluted estimates of NK cells, T cells and myeloid dendritic cells infiltrates on baseline tumors and C2D1 biopsies were higher in patients with DCR at 6 months. Pre & on-treatment IL6 and IL8 rates in tumor secretome & plasma were higher in patients without DCR. Gene Set Enrichment Analyses on RNA-seq from screening biopsies highlighted an enrichment in E2F, MYC and KRAS gene pathways and lower expression of type 1 interferon signature in patients without DCR than those with DCR at 6 months.ConclusionsWith a BORR of 24% and a DCR of 47% at 6 months, pembrolizumab and nintedanib combination provided valuable therapeutic benefits for patients with aMM.Trial RegistrationClinicalTrialsgov, NCT02856425. Registered August 4, 2016 — Prospectively registered,https://clinicaltrials.gov/ct2/show/NCT02856425?term=PEMBIB&draw=2&rank=1.Ethics ApprovalThe protocol was first approved by the Agence Nationale de Sécurité du Médicament (ANSM) on June 24th 2016 (Ref #160371A-12). The protocol was also approved by the Ethical Committee (Comité de Protection des Personnes Ile de France 1) on Jul 12th 2016 (Ref #2016-mai-14236ND).

Unraveling the Effects of a Talimogene Laherparepvec (T-VEC)-Induced Tumor Oncolysate on Myeloid Dendritic Cells

T-VEC, a HSV-1 derived oncolytic virus, is approved for the treatment of advanced melanoma. The mechanisms that underly the systemic anti-tumor effect that is seen following intratumoral injection have not yet been studied but are likely to be mediated by myeloid dendritic cells (myDC) that initiate an adaptive immune response. In this study we could demonstrate that T-VEC is non-toxic for human myDC. T-VEC and a T-VEC oncolysate of melanoma cell lines were able to mature human myDC. myDC were able to take up lysed melanoma cells and cross-present melanoma-derived tumor antigens to antigen-specific T cells. Our results support the possible role of myDC as mediators of an adaptive anti-tumor effect and intratumoral co-administration of T-VEC plus autologous myDC could be a complementary treatment option. A clinical trial that investigates this hypothesis is currently ongoing.

An innate immune activation state prior to vaccination predicts responsiveness to multiple vaccines

Many factors determine whether an individual responding to vaccination will generate an immune response that can lead to protection. Several studies have shown that the pre-vaccination immune state associate with the antibody response to vaccines. However, the generalizability and mechanisms that underlie this association remain poorly defined. Here, we sought to identify a common pre-vaccination signature and mechanisms that could predict the immune response across a wide variety of vaccines. We leveraged the "Immune Signatures Data Resource" created by the NIH Human Immunology Project Consortium (HIPC) to integrate data from 28 studies involving 13 different vaccines and associate the blood transcriptional status of 820 healthy young adults with their responses. An unsupervised analysis of blood transcriptional profiles across studies revealed three distinct pre-vaccination states, characterized by the differential expression of genes associated with a pro-inflammatory response, cell proliferation, and metabolism alterations downstream of NFκB and IRF7. Innate and adaptive immune cell subset-specific genes were also associated with the three pre-vaccination states. Importantly, individuals whose pre-vaccination state was enriched in pro-inflammatory response genes known to be downstream of NFκB tended to have higher serum antibody responses one month after vaccination. A supervised analysis of the same data resulted in a single classifier, also enriched for NFκB regulated genes, that predicted the antibody response across most of the vaccines. Projection into single-cell RNA-sequencing data suggested that this pre-vaccination state was attributable to the signature of activation of non-classical monocytes and myeloid dendritic cells. Transcriptional signatures of recent exposure to bacterial and not viral infections were enriched in the high pro-inflammatory pre-vaccination state and also included NFκB regulated genes. The pro-inflammatory pre-vaccination state was highly reminiscent of the innate activation state triggered by TLR ligands or adjuvants. These results demonstrate that wide variations in the transcriptional state of the immune system in humans can be a key determinant of responsiveness to vaccination. They also define a transcriptional signature NFκB activation at baseline, that is associated with a greater magnitude of antibody response to 13 different vaccines, and suggest that modulation of the innate immune system by next-generation adjuvants targeting NFκB before vaccine administration may improve vaccine responsiveness.

Quercetin Administration Suppresses the Cytokine Storm in Myeloid and Plasmacytoid Dendritic Cells

Dendritic cells (DCs) can be divided by lineage into myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs). They both are present in mucosal tissues and regulate the immune response by secreting chemokines and cytokines. Inflammatory bowel diseases (IBDs) are characterized by a leaky intestinal barrier and the consequent translocation of bacterial lipopolysaccharide (LPS) to the basolateral side. This results in DCs activation, but the response of pDCs is still poorly characterized. In the present study, we compared mDCs and pDCs responses to LPS administration. We present a broad panel of DCs secreted factors, including cytokines, chemokines, and growth factors. Our recent studies demonstrated the anti-inflammatory effects of quercetin administration, but to date, there is no evidence about quercetin’s effects on pDCs. The results of the present study demonstrate that pDCs can respond to LPS and that quercetin exposure modulates soluble factors release through the same molecular pathway used by mDCs (Slpi, Hmox1, and AP-1).