Donor Peripheral Blood Mononuclear Cells Research Articles

Assessing the Immunomodulatory Effect of Size on the Uptake and Immunogenicity of Influenza- and Hepatitis B Subunit Vaccines In Vitro.

Viral subunit vaccines are a safer and more tolerable alternative to whole inactivated virus vaccines. However, they often come with limited efficacy, necessitating the use of adjuvants. Using free and particle-bound viral antigens, we assessed whether size affects the uptake of those antigens by human monocyte-derived dendritic cells (Mo-DCs) and whether differences in uptake affect their capacity to stimulate cytokine production by T cells. To this end, influenza antigens and hepatitis B surface antigen (HBsAg) were covalently conjugated to polystyrene particles of 500 nm and 3 μm. Cellular uptake of the antigens, either unconjugated or conjugated, and their capacity to stimulate T cells within a population of human peripheral blood mononuclear cells (PBMCs) were measured by flow cytometry. Conjugation of both antigens to particles significantly increased their uptake by Mo-DCs. Moreover, both the 500 nm and 3 μm influenza conjugates induced significantly higher numbers of cytokine-producing CD4+ T cells and induced increased production of the pro-inflammatory cytokines IFNγ and TNFα. In contrast, conjugation of HBsAg to particles did not notably affect the T cell response. In conclusion, conjugation of antigen to 500 nm and 3 μm particles leads to increased antigen uptake by human Mo-DCs, although the capacity of such conjugates to induce T cell stimulation likely depends on the immunological status of the PBMC donor.

The Neonatal Fc Receptor Is Elevated in Monocyte-Derived Immune Cells in Pancreatic Cancer.

The neonatal Fc receptor (FcRn) is responsible for recycling of IgG antibodies and albumin throughout the body. This mechanism has been exploited for pharmaceutic delivery across an array of diseases to either enhance or diminish this function. Monoclonal antibodies and albumin-bound nanoparticles are examples of FcRn-dependent anti-cancer therapeutics. Despite its importance in drug delivery, little is known about FcRn expression in circulating immune cells. Through time-of-flight mass cytometry (CyTOF) we were able to characterize FcRn expression in peripheral blood mononuclear cell (PBMC) populations of pancreatic ductal adenocarcinoma (PDAC) patients and non-cancer donors. Furthermore, we were able to replicate these findings in an orthotopic murine model of PDAC. Altogether, we found that in both patients and mice with PDAC, FcRn was elevated in migratory and resident classical dendritic cell type 2 (cDC2) as well as monocytic and granulocytic myeloid-derived suppressor cell (MDSC) populations compared to tumor-free controls. Furthermore, PBMCs from PDAC patients had elevated monocyte, dendritic cells and MDSCs relative to non-cancer donor PBMCs. Future investigations into FcRn activity may further elucidate possible mechanisms of poor efficacy of antibody immunotherapies in patients with PDAC.

P634: MHC-BASED LARGE-SCALE SCREENING FOR ANTI-TUMOR T CELLS IN CHRONIC LYMPHOCYTIC LEUKEMIA REVEALS CD8+ T CELLS WITH SPECIFICITY AGAINST THE CLONOTYPIC B-CELL RECEPTOR IMMUNOGLOBULIN

Background: Chronic lymphocytic leukemia (CLL) is currently incurable, indicating a need for novel strategies towards disease eradication, including reinvigoration of anti-tumor immune responses. T cells in CLL appear selected by restricted antigens, with evidence suggesting that the selecting epitopes may lie within the clonotypic B-cell receptor immunoglobulins (BcR IG). Aims: We previously performed ad hoc prediction of putative T-cell class I neoepitopes contained within the clonotypic BcR IG of CLL patients. Here, we performed major histocompatibility complex (MHC)-based large-scale screening to identify autologous CD8+ T cells recognizing the predicted neoepitopes. Methods: We evaluated 653 peptides derived from the clonotypic BcR IG of 25 CLL patients (median 21 predicted neoepitopes/patient, across 13 MHC-I alleles). Considering the MHC-I typing of each patient, we constructed patient-specific peptide-MHC multimers labeled with a unique DNA barcode plus a fluorochrome (PE). We generated MHC-specific multimer libraries which we then mixed with respective autologous T-cell enriched peripheral blood mononuclear cells (PBMCs). Duplicate samples/patient were analyzed. In addition, known viral peptide-MHC multimers labeled with a different fluorochrome (APC) as well as three MHC-matched healthy donor PBMCs were used as controls. PE- and APC-positive multimer-binding CD8+ T cells were sorted for each cell sample; subsequently, DNA barcode amplification and sequencing was performed. Sequencing data were processed (Barracoda software) to obtain the number of clonally reduced barcode reads assigned to a given sample and peptide-MHC specificity. The number of clonally reduced reads for a given pMHC specificity was used to estimate the frequency of T cells specific for a given epitope, based on the average number of T cell receptor–MHC multimer interactions detected in the total MHC multimer-binding T cell pool in a given cell sample. Peptides with a log fold change >2 were considered as significant [log fold change: (number of DNA barcode reads associated with a specific pMHC)/3x (number of total barcode reads derived from the same sample)]. Results: Overall, 3 peptide-MHC multimers were recognized by CD8+ T cells: (i) VTVADTAVYY (peptide A) and (ii) INLNPSLKRR (peptide B), both within the context of the A03*01 allele, and (iii) YSFTSYWINW (peptide C) within the context of the A24*02 allele. Peptide A derived from the IGHV4-34 FR3 region of a somatically hypermutated clonotypic BcR IG, containing a single A to V somatic hypermutation (SHM) at position 96. Peptide B derived from the IGHV4-39 CDR2-FR3 junction of a somatically hypermutated clonotypic BcR IG, containing 3 SHMs (T to I at position 65, Y to L at position 67 and S to R at position 74). Peptide C derived from the IGHV5-10-1 CDR1-FR2 junction of a clonotypic BcR IG assigned to stereotyped subset #1, containing the sole SHM of the IG (S to N at position 40). The immunogenicity of these peptides was further corroborated by the fact that they were recognized not only by the autologous T cells of the patient from whom the peptide derived, but also by T cells of other patients as well as a healthy donor sharing the respective MHC allele. Summary/Conclusion: In conclusion, we offer proof of concept that the targeted SHM which shapes the CLL BcR IG repertoire may produce idiotypic targets for T cell-based therapy or peptide vaccine design. Characterization of the epitope-binding T cells is currently underway by our group, aiming to provide further insight on how these cells could be recruited into effective anti-tumor responses.

Abstract 559: Targeting hematological malignancies and solid tumors with switchable chimeric antigen receptor-engineered iPSC-derived natural killer cells

Abstract Switchable chimeric antigen receptors (sCAR) provide an important new strategy to precisely regulate CAR-mediated anti-tumor activity. The sCAR system combines a CAR that recognizes peptide neoepitope (PNE) with an injectable “switch” molecule that consists of an anti-tumor Fab linked to PNE. Configurating PNE at different location or chain of the Fab enables us to identify best switches optimal for tumor targeting. Previous studies demonstrate that this sCAR system expressed in T cells provides tight control over anti-tumor activity. Here, we translated this approach to engineer natural killer (NK) cells with the sCAR to provide a universal, targeted cell-therapy approach in a patient-nonspecific manner. First, we engineered human induced pluripotent stem cells (iPSCs) with the sCAR combining the PNE-specific CAR scFv with our previously described NK cell optimized CAR4 signaling motifs consisting of the NKG2D transmembrane domain, 2B4 co-stimulatory domain and the CD3ζ chain. We selected clones that maintained highest level of pluripotency and most stable expression of the sCAR4 on the surface. Next, we generated mature sCAR4-expressing iPSC-derived NK cells that expressed common surface receptors similar to that of donor peripheral blood mononuclear cell-derived NK cells. We then used three panels of switches with specificity to CD19 (consisting of 9 different configurations), to CD33, CD123 and CLL1 (1 configuration each), and to FRIZZLED7 (FZD7; 6 configurations) to target CD19+ B cell lymphoma, acute myeloid leukemia (AML), and ovarian cancer, respectively. All three targets demonstrated switch-specific dose response in killing tumor cell lines. Different configurations conferred variable efficiencies in switch-mediating tumor cell killings and the optimal switch concentrations were found to be different from what was observed previously with sCAR-expressing T cells. In a comparison with the “conventional” (non-switchable) CARs (cCARs), iPSC-NK cells expressing either sCAR4 and treated with an anti-CD19 switch or iPSC-NK cells with an anti-CD19-cCAR4 demonstrated similar level of cytotoxicity against B cell leukemia cells. Finally, we have built a mouse model and are currently testing the iPSC-NK-sCAR system in vivo. Together, this iPSC-NK-sCAR strategy enables close control over CAR-mediated activity with flexibility to target multiple tumor types and a potential to become a novel off-the-shelf therapy. Citation Format: Xiao-Hua Li, Benjamin Goldenson, Jaya Lakshmi Thangaraj, Matthew Gynn, Diana Gumber, Myan Do, Karl Willert, Dan S. Kaufman. Targeting hematological malignancies and solid tumors with switchable chimeric antigen receptor-engineered iPSC-derived natural killer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 559.

DAP10 integration in CAR-T cells enhances the killing of heterogeneous tumors by harnessing endogenous NKG2D

Although chimeric antigen receptor T (CAR-T) cells have achieved remarkable successes in hematological malignancies, the efficacies of CAR-T cells against solid tumors remains unsatisfactory. Heterogeneous antigen expression is one of the obstacles on its effective elimination of solid cancer cells. DNAX-activating protein 10 (DAP10) interacts with natural killer group 2D (NKG2D), acting as an adaptor that targets various malignant cells for surveillance. Here, we designed a DAP10 chimeric receptor that utilized native NKG2D on T cells to target NKG2D ligand-expressing cancer cells. We then tandemly incorporated it with anti-glypican 3 (GPC3) single-chain variable fragment (scFv) to construct a dual-antigen-targeting system. T cells expressing DAP10 chimeric receptor (DAP10-T cells) displayed with an enhancement on both cytotoxicity and cytokine secretion against solid cancer cell lines, and its tandem connection with anti-GPC3 scFv (CAR GPC3-DAP10-T cells) exhibited a dual-antigen-targeting capacity on eliminating heterogeneous cancer cells in vitro and suppressing the growth of heterogeneous cancer in vivo. Thus, this novel dual-targeting system enabled a high efficacy on killing cancer cells and extended the recognition profile of CAR-T cells toward tumors, which providing a potential strategy on treatment of solid cancer clinically.

Tumor-Derived Exosomes Regulate Apoptosis of CD45+EpCAM+ Cells in Lung Cancer.

Lung cancer has the highest mortality rate among human cancers, and the majority of deaths result from metastatic spread. The tumor microenvironment plays an important role in suppressing the immune surveillance and elimination of tumor cells. A few studies have reported the presence of CD45+EpCAM+ double-positive cells in cancer, but the underlying mechanism remains unclear with respect to how these cells originate and their function in cancer biology. In this study, we analyzed 25 lung tumor samples. We confirmed the presence of CD45+EpCAM+ cells in lung cancer, and these cells exhibited higher apoptosis than CD45+EpCAM− cells. Using co-culture of lung cancer cell-derived exosomes with healthy donor peripheral blood mononuclear cells, we recapitulated CD45+EpCAM+ cell formation and increased apoptosis that occurs in patients with primary lung cancer. Further analysis suggested that microRNAs in lung cancer cell-derived exosomes may alter the gene expression profile of CD45+EpCAM+ cells, resulting in elevated TP53 expression and increased apoptosis. To our knowledge, this is the first report of cancer cell-derived exosomes that can inhibit the immune system by promoting immune cell apoptosis.

Soluble HLA peptidome of pleural effusions is a valuable source for tumor antigens

BackgroundSoluble human leucocyte antigen (sHLA) molecules, released into the plasma, carry their original peptide cargo and provide insight into the protein synthesis and degradation schemes of their source cells and...

Abstract 525: Uncovering Mechanisms Between Oligosaccharide Galactose-alpha 1,3-galactose (alpha-gal) Sensitization And Atherosclerosis

Recent work by our group and others have shown individuals with IgE to the oligosaccharide allergen present in mammalian products (α-gal) have increased atheroma burden with increased necrosis and calcification compared to those without α -gal specific IgE. These data suggest α -gal specific IgE increase plaque severity and vulnerability, yet the mechanisms that promote production of IgE to α -gal are unknown. Previous work from our group utilized multi-omics single cell analysis of circulating PBMCs from subjects with coronary angiography at UVA and showed subjects with IgE α -gal sensitization had a higher frequency of CCR6hi switched memory (SWM) B cells and that the CCR6 ligand, CCL20, increased class switching to IgE. To determine mechanisms whereby CCR6 may mediated class switching to IgE, we enriched total B cells from healthy donor peripheral blood mononuclear cells and stimulated with 20ng/ml human IL-4 and 10μg/ml agnostic anti-human CD40 with or without 20ng/ml CCL20 for 3 days. After 3 days of treatment, cells were collected and stained with a 15-color panel and analyzed via flow cytometry. Cells were analyzed for surface expression of CD20 and CD3 to gate total B cells. Gated B cells were further separated into CD27+/IgM-/IgD- to define SWM B cell population. CCL20 treatment did not increase the total percent of SWM B cells; however, there was a 2-3-fold increase in CCR6+ SWM B cells compared to CCR6- SWM B cells. CCL20 treated CCR6+ SWM B cells have an average of 7% increase of phosphorylated mTOR in total SWM B cells compared to nonCCL20 treated CCR6+ SWM B cells. These results suggest CCL20 stimulation induces mTOR phosphorylation and activation. Thus, mTOR activation and downstream mediators may be necessary for α -gal induced B cell class switching. From these preliminary studies, we conclude that CCL20 stimulation increases the percent pmTOR+ SWM B cells. We will continue to investigate downstream mTOR mediators in regard to B cell class switching after CCL20 stimulation and how α-gal sensitization augments B cell IgE class switching and increases atherosclerosis with our novel α -gal-/- Apoe-/- mouse.

Molecular mechanisms of dexamethasone-mediated modulation of inflammatory and interferon responses in severe COVID-19 patients.

Abstract Severe COVID-19 is characterized by cytokine storm, an excessive production of pro-inflammatory cytokines, which results in acute lung damage and death. Dexamethasone (Dex), a corticosteroid administered as a standard of care for severe COVID-19, has been shown to reduce the onset of severe complications in these patients. However, the mechanisms underlying the beneficial effects of Dex are poorly understood. We conducted a transcriptomic analysis (NanoString) of peripheral blood mononuclear cells (PBMCs) from COVID-19 patients with mild (no hospitalization) and severe (on ventilator in the ICU) disease. The latter group included patients ± Dex. Treatment of severe COVID-19 patients with Dex inhibited pro-inflammatory pathways, circulating cytotoxic and Th1 cells, interferon (IFN) signaling and the genes involved in cytokine storm (IL-1, IL-6 and IFN-γ), which were altered in severe vs mild disease. Pro-inflammatory immune cell functions are regulated by calcium signaling, which in turn is under the control of Kv1.3 potassium channels, but their role in the complications associated with COVID-19 remains elusive. RT-qPCR experiments in PBMCs from COVID-19 patient cohorts showed an increase in Kv1.3 expression in severe patients that was significantly reduced by Dex treatment. In agreement with these findings, in vitro treatment with Dex reduced Kv1.3 protein abundance in CD3+, CD4+, CD8+ T cell and CD56dim NK cells in healthy donor (HD) PBMC, while NanoString showed inhibition of pro-inflammatory genes and cytokines. Functional studies showed that Dex significantly reduced Kv1.3 activity and IFN-γ in HD T cells. Thus, our findings suggest that Kv1.3 inhibition contributes to the immunosuppression by Dex. This work was supported by Senior Pilot Grant, University of Cincinnati, Department of Internal Medicine to LC, NIH (R38HL155775 to MC) and Biospecimens and associated data were provided by the Cincinnati COVID-19 Repository at the University of Cincinnati and Cincinnati Children’s Hospital Medical Center.

Rapid Generation of TCR and CD8αβ Transgenic Virus Specific T Cells for Immunotherapy of Leukemia.

BackgroundVirus-specific T cells (VSTs) are an attractive cell therapy platform for the delivery of tumor-targeted transgenic receptors. However, manufacturing with conventional methods may require several weeks and intensive handling. Here we evaluated the feasibility and timelines when combining IFN-γ cytokine capture (CC) with retroviral transduction for the generation of T cell receptor (TCR) and CD8αβ (TCR8) transgenic VSTs to simultaneously target several viral and tumor antigens in a single product.MethodsHealthy donor peripheral blood mononuclear cells were stimulated with cytomegalovirus (CMV) and Epstein-Barr-Virus (EBV) peptide mixtures derived from immunogenic viral proteins, followed by CC bead selection. After 3 days in culture, cells were transduced with a retroviral vector encoding four genes (a survivin-specific αβTCR and CD8αβ). TCR8-transgenic or control VSTs were expanded and characterized for their phenotype, specificity and anti-viral and anti-tumor functions.ResultsCC selected cells were efficiently transduced with TCR8. Average fold expansion was 269-fold in 10 days, and cells contained a high proportion of CD8+ T central memory cells. TCR8+ VSTs simultaneously expressed native anti-viral and transgenic anti-survivin TCRs on their cell surface. Both control and TCR8+ VSTs produced cytokines to and killed viral targets, while tumor targets were only recognized and killed by TCR8+ VSTs.ConclusionsIFN-γ cytokine capture selects and activates CMV and EBV-specific memory precursor CD8+ T cells that can be efficiently gene-modified by retroviral transduction and rapidly ex vivo expanded. Our multi-specific T cells are polyfunctional and recognize and kill viral and leukemic targets expressing the cognate antigens.

SARS-CoV-2 Humoral and Cellular Immune Responses of Patients With HIV After Vaccination With BNT162b2 mRNA COVID-19 Vaccine in the Tel-Aviv Medical Center.

BackgroundLittle is known about vaccine efficacy and sustainability among people with HIV (PWH). We estimated humoral and cellular immune responses postvaccination with BNT162b2 mRNA coronavirus disease 2019 (COVID-19) vaccine among PWH in Tel-Aviv Medical Center.MethodsThe vaccine humoral response was evaluated by measuring immunoglobulin G (IgG) titers of antispike receptor-binding domain antibodies (anti-RBD IgG). Cellular response was assessed by stimulating donor peripheral blood mononuclear cells with pooled complete S-peptide mix.ResultsOne hundred thirty-six PWH who completed 2 doses of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine were tested for anti-RBD IgG and compared with 61 vaccinated health care workers (HCWs). The antibody titers were similar between the groups (median, 118 BAU/mL for PWH and 101.4 BAU/mL for HCWs; P = .231), although the mean time from second vaccine was 4.5 months in PWH and 6.7 months in HCWs (P < .0001). Longer time from second vaccine dose was associated with decreased antibody level, as were CD4 counts <300 cells/µL compared with higher CD4 counts (25.1 BAU/mL vs 119.3 BAU/mL, respectively; P = .047). There was no difference in cellular immune response between vaccinated PWH, convalescent unvaccinated PWH, and vaccinated HCWs.ConclusionsThe humoral immune response of PWH was comparable to that of HCWs after BNT162b2 mRNA vaccination. Cellular immune response did not differ between vaccinated PWH, convalescent PWH, and vaccinated HCWs. PWH with CD4 counts <300 cells/µL (n = 9) had lower antibody titers compared with patients with counts >300 cells/µL (n = 127).

Ingestion of hemozoin by peripheral blood mononuclear cells alters temporal gene expression of ubiquitination processes

Plasmodium falciparum (Pf) malaria is among the leading causes of childhood morbidity and mortality worldwide. During a natural infection, ingestion of the malarial parasite product, hemozoin (PfHz), by circulating phagocytic cells induces dysregulation in innate immunity and enhances malaria pathogenesis. Treatment of cultured peripheral blood mononuclear cells (PBMCs) from healthy, malaria-naïve donors with physiological concentrations of PfHz can serve as an in vitro model to investigate cellular processes. Although disruptions in host ubiquitination processes are central to the pathogenesis of many diseases, this system remains unexplored in malaria. As such, we investigated the impact of PfHz on the temporal expression patterns of 84 genes involved in ubiquitination processes. Donor PBMCs were cultured in the absence or presence of PfHz for 3-, 9-, and 24 h. Stimulation with PfHz for 3 h did not significantly alter gene expression. Incubation for 9 h, however, elicited significant changes for 6 genes: 4 were down-regulated (FBXO4, NEDD8, UBE2E3, and UBE2W) and 2 were up-regulated (HERC5 and UBE2J1). PfHz treatment for 24 h significantly altered expression for 14 genes: 12 were down-regulated (ANAPC11, BRCC3, CUL4B, FBXO4, MIB1, SKP2, TP53, UBA2, UBA3, UBE2G1, UBE2G2, and WWP1), while 2 were up-regulated (UBE2J1 and UBE2Z). Collectively, these results demonstrate that phagocytosis of PfHz by PBMCs elicits temporal changes in the transcriptional profiles of genes central to host ubiquitination processes. Results presented here suggest that disruptions in ubiquitination may be a previously undiscovered feature of malaria pathogenesis.

Restimulation-Induced Cell Death (RICD): Methods for Modeling, Investigating, and Quantifying RICD Sensitivity in Primary Human T Cells via Flow Cytometric Analysis.

When the body mounts an immune response against a foreign pathogen, the adaptive arm of the immune system relies upon clonal expansion of antigen-specific T cell populations to exercise acquired effector and cytotoxic functions to clear it. However, T cell expansion must be modulated to effectively combat the perceived threat without inducing excessive collateral damage to host tissues. Restimulation-induced cell death (RICD) is an apoptotic program triggered in activated T cells when an abundance of antigen and IL-2 are present, imposing a negative feedback mechanism that constrains the growing T cell population. This autoregulatory process can be detected via increases in caspase activation, Annexin V binding, and loss of mitochondrial membrane potential. However, simple changes in T cell viability through flow cytometric analysis can reliably measure RICD sensitivity in response to T-cell receptor (TCR) restimulation. This protocol describes the in vitro polyclonal activation, expansion, and restimulation of human primary T cells isolated from donor peripheral blood mononuclear cells (PBMC). This simple procedure allows for accurate quantification of RICD via flow cytometry. We also describe strategies for interrogating the role of specific proteins and pathways that may alter RICD sensitivity. This straightforward protocol provides a quick and dependable tool to track RICD sensitivity in culture over time while probing critical factors that control the magnitude and longevity of an adaptive immune response. Graphic abstract: In-vitro simulation of restimulation-induced cell death in activated human T cells.

The Novel Dual Topoisomerase Inhibitor P8-D6 Shows Anti-myeloma Activity In Vitro and In Vivo.

P8-D6 is a novel dual inhibitor of human topoisomerase I (TOP1) and II (TOP2) with broad pro-apoptotic antitumor activity. NCI-60 screening revealed markedly improved cytotoxicity of P8-D6 against solid and leukemia cell lines compared with other single and dual topoisomerase inhibitors, for example, irinotecan, doxorubicin, or pyrazoloacridine. In this study, we investigated the capacity of P8-D6 to inhibit myeloma cell growth in vitro and in vivo Growth inhibition assays demonstrated significant anti-myeloma effects against different myeloma cell lines with IC50 values in the low nanomolar range. Freshly isolated plasma cells of patients with multiple myeloma were killed by P8-D6 with similar doses. P8-D6 activated caspase 3/7 and induced significant apoptosis of myeloma cells. Supportive effects of bone marrow stromal cells on IL6-dependent INA-6 myeloma cells were abrogated by P8-D6 and apoptosis occurred in a time- and dose-dependent manner. Of note, healthy donor peripheral blood mononuclear cells and human umbilical vein endothelial cells were not affected at concentrations toxic for malignant plasma cells. Treatment of myeloma xenografts in immunodeficient SCID/beige mice by intravenous and, notably, also oral application of P8-D6 markedly inhibited tumor growths, and significantly prolonged survival of tumor-bearing mice.

Anti-C1q autoantibodies from systemic lupus erythematosus patients enhance CD40-CD154-mediated inflammation in peripheral blood mononuclear cells in vitro.

ObjectivesSystemic lupus erythematosus (SLE) is a clinically heterogeneous autoimmune disease with complex pathogenic mechanisms. Complement C1q has been shown to play a major role in SLE, and autoantibodies against C1q (anti‐C1q) are strongly associated with SLE disease activity and severe lupus nephritis suggesting a pathogenic role for anti‐C1q. Whereas C1q alone has anti‐inflammatory effects on human monocytes and macrophages, C1q/anti‐C1q complexes favor a pro‐inflammatory phenotype. This study aimed to elucidate the inflammatory effects of anti‐C1q on peripheral blood mononuclear cells (PBMCs).MethodsIsolated monocytes, isolated T cells and bulk PBMCs of healthy donors with or without concomitant T cell activation were exposed to C1q or complexes of C1q and SLE patient‐derived anti‐C1q (C1q/anti‐C1q). Functional consequences of C1q/anti‐C1q on cells were assessed by determining cytokine secretion, monocyte surface marker expression, T cell activation and proliferation.ResultsExposure of isolated T cells to C1q or C1q/anti‐C1q did not affect their activation and proliferation. However, unspecific T cell activation in PBMCs in the presence of C1q/anti‐C1q resulted in increased TNF, IFN‐γ and IL‐10 secretion compared with C1q alone. Co‐culture and inhibition experiments showed that the inflammatory effect of C1q/anti‐C1q on PBMCs was due to a direct CD40–CD154 interaction between activated T cells and C1q/anti‐C1q‐primed monocytes. The CD40‐mediated inflammatory reaction of monocytes involves TRAF6 and JAK3‐STAT5 signalling.ConclusionIn conclusion, C1q/anti‐C1q have a pro‐inflammatory effect on monocytes that depends on T cell activation and CD40–CD154 signalling. This signalling pathway could serve as a therapeutic target for anti‐C1q‐mediated inflammation.

BpOmpW Antigen Stimulates the Necessary Protective T-Cell Responses Against Melioidosis.

Melioidosis is a potentially fatal bacterial disease caused by Burkholderia pseudomallei and is estimated to cause 89,000 deaths per year in endemic areas of Southeast Asia and Northern Australia. People with diabetes mellitus are most at risk of melioidosis, with a 12-fold increased susceptibility for severe disease. Interferon gamma (IFN-γ) responses from CD4 and CD8 T cells, but also from natural killer (NK) and natural killer T (NKT) cells, are necessary to eliminate the pathogen. We previously reported that immunization with B. pseudomallei OmpW (BpOmpW antigen) protected mice from lethal B. pseudomallei challenge for up to 81 days. Elucidating the immune correlates of protection of the protective BpOmpW vaccine is an essential step prior to clinical trials. Thus, we immunized either non-insulin-resistant C57BL/6J mice or an insulin-resistant C57BL/6J mouse model of type 2 diabetes (T2D) with a single dose of BpOmpW. BpOmpW induced strong antibody responses, stimulated effector CD4+ and CD8+ T cells and CD4+ CD25+ Foxp3+ regulatory T cells, and produced higher IFN-γ responses in CD4+, CD8+, NK, and NKT cells in non-insulin-resistant mice. The T-cell responses of insulin-resistant mice to BpOmpW were comparable to those of non-insulin-resistant mice. In addition, as a precursor to its evaluation in human studies, humanized HLA-DR and HLA-DQ (human leukocyte antigen DR and DQ isotypes, respectively) transgenic mice elicited IFN-γ recall responses in an enzyme-linked immune absorbent spot (ELISpot)-based study. Moreover, human donor peripheral blood mononuclear cells (PBMCs) exposed to BpOmpW for 7 days showed T-cell proliferation. Finally, plasma from melioidosis survivors with diabetes recognized our BpOmpW vaccine antigen. Overall, the range of approaches used strongly indicated that BpOmpW elicits the necessary immune responses to combat melioidosis and bring this vaccine closer to clinical trials.

An In Vitro Assessment of Immunostimulatory Responses to Ten Model Innate Immune Response Modulating Impurities (IIRMIs) and Peptide Drug Product, Teriparatide.

Understanding, predicting, and minimizing the immunogenicity of peptide-based therapeutics are of paramount importance for ensuring the safety and efficacy of these products. The so-called anti-drug antibodies (ADA) may have various clinical consequences, including but not limited to the alteration in the product’s distribution, biological activity, and clearance profiles. The immunogenicity of biotherapeutics can be influenced by immunostimulation triggered by the presence of innate immune response modulating impurities (IIRMIs) inadvertently introduced during the manufacturing process. Herein, we evaluate the applicability of several in vitro assays (i.e., complement activation, leukocyte proliferation, and cytokine secretion) for the screening of innate immune responses induced by ten common IIRMIs (Bacillus subtilis flagellin, FSL-1, zymosan, ODN2006, poly(I:C) HMW, poly(I:C) LMW, CLO75, MDP, ODN2216, and Escherichia coli O111:B4 LPS), and a model biotherapeutic Forteo™ (teriparatide). Our study identifies cytokine secretion from healthy human donor peripheral blood mononuclear cells (PBMC) as a sensitive method for the in vitro monitoring of innate immune responses to individual IIRMIs and teriparatide (TP). We identify signature cytokines, evaluate both broad and narrow multiplex cytokine panels, and discuss how the assay logistics influence the performance of this in vitro assay.

209.4: Characterizing the Therapeutic Potential of Human Pluripotent Stem Cell-derived Islet-like Cells Lacking Cell-Surface HLA Expression

Introduction: While islet or pancreas transplantation remains the optimal way of restoring physiologic blood glucose control in patients with Type 1 diabetes, these therapies are limited by a scarcity of organs available for transplantation and the requirement for immunosuppression to prevent rejection. Recently, effective methods to generate functional islet-like cells (ILCs) from human pluripotent stem cells (hPSCs) have been developed, which opens the possibility for organ replacement without the limitation of scarcity. However, hPSC-derived ILCs would still be expected to be rejected without immunosuppression, which would increase the toxicity associated with this therapy. Because HLA proteins are considered to be primary triggers of allorecognition and rejection, we sought to determine whether hPSCs deficient for cell-surface HLA class I and II expression could differentiate into ILCs less prone to allorejection. Methods: We differentiated HLA-control and HLA-deficient hPSCs into ILCs using an optimized 23 day differentiation protocol. Cells were characterized for pancreatic islet markers, cell surface HLA antigens, and co-stimulatory ligands by flow cytometry. The allo-immunogenicity of control and HLA-deficient ILCs was determined by their ability to induce proliferation, as assessed by CFSE dilution, in allogeneic CD4+ and CD8+ T cells isolated from healthy donor peripheral blood mononuclear cells. Results: We found that HLA-deficient hPSCs exhibited no impairment in their differentiation into ILCs, with both control and HLA-deficient hPSCs generating populations with >90% expression of the endocrine marker Chromogranin A, as assessed by flow cytometry (Figure 1). Unexpectedly, HLA-deficient hPSCs contained a higher proportion of NKX6.1+CPEP+ beta-like cells compared with control hPSCs (p = 0.03). HLA-control ILCs, HLA-deficient ILCs, and primary human islets had similar cell-surface expression of immunomodulatory ligands, with the notable exception that only HLA-deficient ILCs did not express any HLA class I. Upon co-culture with primary allogeneic T cells, control ILCs induced robust activation of CD8+ T cells isolated from 3 out of 4 healthy donors, while HLA-deficient ILCs were not able to induce activation in any of the 4 donors (Figure 2).Discussion/Conclusion: We have found that HLA-deficient hPSCs exhibit no impairment in the ability to differentiate into ILC, and that HLA-deficient ILCs have advantageous immunologic properties. This suggests that patients treated with these cells may not require as much immunosuppression to avoid allorejection. HLA-deficient ILCs may thus be superior candidates for clinical translation for the treatment of type 1 diabetes.

Manufacture and Immunological Characterization of GMP-Compliant Functional Sars-COV-2 Cytotoxic T Lymphocytes (CTLs) Utilizing the Clinimacs ® Cytokine Capture System

Background: The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a pandemic that has taken millions of lives around the globe. Treatment of patients with moderate and severe COVID-19 disease has included dexamethasone, tocilizumab, Remdesivir, convalescent plasma, and targeted antibodies, however, currently, there are no FDA approved targeted cellular therapies in the treatment of mild or moderate SARS-CoV-2 disease. Virus-specific cytotoxic T cell lymphocytes (vCTLs) have shown therapeutic efficacy in immunocompromised patients with viral infections. We developed a multicenter and multidisciplinary Viral Cytotoxic T-Cell Consortium (VIRCTLC) to investigate the use of vCTLs manufactured by direct enrichment using the Cytokine Capture System (CCS) on the CliniMACS® Prodigy device. SARS-CoV-2 specific PepTivator Peptides consist of overlapping peptides that span the entire sequence of the protein (Protein N and M), or the length of its immunodominant domain (Protein S). The peptides can bind to either MHC class I or MHC class II molecules and are therefore able to target both CD4 and CD8 T cells.Objective: To screen, manufacture, and characterize SARS-CoV-2 vCTLs generated from convalescent COVID-19 donors using the CliniMACS® Cytokine Capture System on the CliniMACS® Prodigy device.Methods: Donor screening was done utilizing PBMNCs from 15 convalescent COVID-19 donors after informed consent. PBMNCs were stimulated with a mix of PepTivator peptides (Miltenyi Biotech®) contained in the S, M and N proteins. IFN-γ levels were examined in CD3, CD4, and CD8 T cells by flow cytometry analysis. After informed consent, PBMNCs from three convalescent COVID-19 donors who screened positively to the PepTivator® peptide pools of SARS-CoV-2 Proteins M, N and S were collected by apheresis using the SPECTRA Optia® apheresis instrument. PBMNCs were incubated with the PepTivator® peptide pools for 4 hours. After incubation, the SARS-CoV-2 vCTLs were enriched using the CliniMACS Cytokine Capture System as we have previously described (Flower/Cairo, et al, ASTCT, 2020). Samples were taken from the enriched vCTLs and tested in gram stains, sterility cultures, cell counts, viability and IFN-γ cytokine staining (CD3/CD4/CD8/IFN-γ marker panel) by flow cytometry. Amplification and sequencing of TCRβ CDR3 regions of pre-stimulated PBMNC, stimulated PBMNCs samples taken from the QC bag (QC samples) and the enriched SARS-CoV-2 vCTLs were performed on the ImmunoSEQ platform using ImmunoSEQ® TCRB Assay kit (Adaptive Biotechnologies, Seattle, WA, USA). Characterization of immune subsets was done by mass cytometry analysis with 41 Immunophenotypic markers. Transcriptome of the immune landscape of QC samples, and enriched vCTLs was compared with the pre samples using the human nCounter PanCancer Immune Profiling Panel on the nCounter system.Results: We demonstrate that 93.3% of convalescent donor blood samples passed the screening criteria for clinical manufacture. Three validation runs resulted in enriched T cells that consisted of 79% + 21% (mean + SEM) IFNγ + T cells (Fig.1). TCRβ sequencing showed that convalescent COVID-19 donors have a highly diverse TCR repertoire and we identified TCRβ CDR3 clones that are known to be associated with SARS-CoV-2 T cell responses. Immunophenotyping analysis demonstrated more CD4 T cells than CD8 T cells in the SARS CoV-2 vCTLs, an increase in memory CD8 and CD4 cells, especially CD8 T EM, CD4 T cm and CD4 T EMRA cells (Fig.2) and an increase DC cells in the SARS CoV-2 vCTL products as compared to pre-stimulated PBMNCs. Expression of the exhaustion markers was not enhanced in the SARS CoV-2 vCTLs as compared to pre-stimulated PBMNCs. Transcriptome analysis showed increased gene expression in T-cell function, interleukin, pathogen defense, and TNF superfamily pathway genes in the SARS CoV-2 vCTLs as compared to pre-stimulated PBMNCs.Conclusion: Our study demonstrates that highly functional SARS-CoV-2 vCTLs can be rapidly generated by direct cytokine enrichment from convalescent donor peripheral blood mononuclear cells. These data serve as pre-clinical validation for an ongoing clinical trial utilizing related HLA-matched and haplo-identical SARS CoV-2 vCTLs for the treatment of patients with mild and moderate SARS-CoV-2 disease (IND #27260, NCT# 04896606). [Display omitted] DisclosuresLee: Kiadis Pharma: Divested equity in a private or publicly-traded company in the past 24 months, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Courier Therapeutics: Current holder of individual stocks in a privately-held company. Johnson: Miltenyi Biotec: Research Funding. Cairo: Jazz Pharmaceutical: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Speakers Bureau; Sanofi: Speakers Bureau; Servier: Speakers Bureau; Sobi: Speakers Bureau; Omeros: Membership on an entity's Board of Directors or advisory committees; Nektar: Membership on an entity's Board of Directors or advisory committees.

Off-the-Shelf, Multiplexed-Engineered iPSC-Derived NK Cells Mediate Potent Multi-Antigen Targeting of B-Cell Malignancies with Reduced Cytotoxicity Against Healthy B Cells

Off-the-Shelf, Multiplexed-Engineered iPSC-Derived NK Cells Mediate Potent Multi-Antigen Targeting of B-Cell Malignancies with Reduced Cytotoxicity Against Healthy B Cells