Modulation Of Antigen Presentation Research Articles

Advances in Polymeric Micelles: Responsive and Targeting Approaches for Cancer Immunotherapy in the Tumor Microenvironment.

In recent years, to treat a diverse array of cancer forms, considerable advancements have been achieved in the field of cancer immunotherapies. However, these therapies encounter multiple challenges in clinical practice, such as high immune-mediated toxicity, insufficient accumulation in cancer tissues, and undesired off-target reactions. To tackle these limitations and enhance bioavailability, polymer micelles present potential solutions by enabling precise drug delivery to the target site, thus amplifying the effectiveness of immunotherapy. This review article offers an extensive survey of recent progress in cancer immunotherapy strategies utilizing micelles. These strategies include responsive and remodeling approaches to the tumor microenvironment (TME), modulation of immunosuppressive cells within the TME, enhancement of immune checkpoint inhibitors, utilization of cancer vaccine platforms, modulation of antigen presentation, manipulation of engineered T cells, and targeting other components of the TME. Subsequently, we delve into the present state and constraints linked to the clinical utilization of polymeric micelles. Collectively, polymer micelles demonstrate excellent prospects in tumor immunotherapy by effectively addressing the challenges associated with conventional cancer immunotherapies.

Efek Suplemen Vitamin D untuk Pencegahan COVID-19

Vitamin D in the form of 1,25-dihydroxy vitamin D (1,25D) has the function of modulating antigen presentation as well as T cell proliferation and phenotype, with the overall effect of suppressing inflammation and enhancing immune tolerance. Interventional and observational epidemiological studies provide evidence that vitamin D deficiency can increase the risk of respiratory infections such as COVID-19. COVID-19 is an infection with the SARS-CoV-2 virus that attacks the respiratory system, resulting in severe Acute Respiratory Distress Syndrome (ARDS) symptoms that can cause death. Vitamin D can naturally be obtained from food or by sunbathing, but in an infected condition, a person needs additional vitamin D from supplements. Therefore, this Literature Review was compiled with the aim of knowing the effect of vitamin D supplements in preventing COVID-19 and knowing the effect of vitamin D supplements in reducing the severity of COVID-19 symptoms. The method used is an electronic database using NCBI and PubMed. The author uses the keywords supplement d3, COVID-19, prevention. The criteria for selecting journals are based on the publication year above January 1, 2020, experimental research design, there is a comparison of vitamin D administration with controls or placebo in COVID-19 patients, and the study has been completed. Based on the established criteria, 10 journals were obtained as the main reference. The results of the literature review show that vitamin D has an important role in the body's immunity and is useful for increasing serum vitamin D levels so as to prevent and accelerate the healing of COVID-19. The dose of vitamin D for the prevention of COVID-19 in the elderly is 50,000 IU/month while the therapeutic dose for reducing mild to moderate symptoms is 10,000 IU/day for a week and continued with 5000 IU/day until recovery. However, if the patient has severe symptoms, comorbid disease and vitamin D deficiency, administer 40,000 IU/day.

Inorganic nanosheets facilitate humoral immunity against medical implant infections by modulating immune co-stimulatory pathways

Strategies to manipulate immune cell co-inhibitory or co-activating signals have revolutionized immunotherapy. However, certain immunologically cold diseases, such as bacterial biofilm infections of medical implants are hard to target due to the complexity of the immune co-stimulatory pathways involved. Here we show that two-dimensional manganese chalcogenophosphates MnPSe3 (MPS) nanosheets modified with polyvinylpyrrolidone (PVP) are capable of triggering a strong anti-bacterial biofilm humoral immunity in a mouse model of surgical implant infection via modulating antigen presentation and costimulatory molecule expression in the infectious microenvironment (IME). Mechanistically, the PVP-modified MPS (MPS-PVP) damages the structure of the biofilm which results in antigen exposure by generating reactive oxidative species, while changing the balance of immune-inhibitory (IL4I1 and CD206) and co-activator signals (CD40, CD80 and CD69). This leads to amplified APC priming and antigen presentation, resulting in biofilm-specific humoral immune and memory responses. In our work, we demonstrate that pre-surgical neoadjuvant immunotherapy utilizing MPS-PVP successfully mitigates residual and recurrent infections following removal of the infected implants. This study thus offers an alternative to replace antibiotics against hard-to-treat biofilm infections.

Abstract 1371: Rho-GEF hampers CD8+T cells-mediated immunosurveillance by reducing antigen presentation

Abstract Immune response is a critical anti-tumor response to overcome tumorigenesis. In line with this, immune checkpoint blockade shows tremendous anti-tumor efficacy by enhancing cytotoxicity of CD8+ cytotoxic T lymphocytes (CTLs). However, cancer cells develop different mechanisms of immune evasion, among which suppression of immune recognition of somatic mutations via tumor antigen is prevalent. In fact, 65% to 90% of the cancers show reduced MHC-I antigen presentation. There is, nonetheless, little achievement toward the therapeutic approaches to restore antigen presentation on tumor cells. Colorectal cancer (CRC), the second deadliest cancer in U.S., shows increasing incidence and mortality rates over the past years. Standard conventional CRC treatments, surgery, chemotherapy and radiotherapy, often lead to many side effects due to their non-specificity and cytotoxicity. While immunotherapy is very promising, only a small population of CRC patients respond to the current immune checkpoint inhibitors. In this study, our objective was to harness a novel immunological approach to target CRC tumors. We developed a bioinformatics tool to create a pool of genes whose expression negatively correlates with cytotoxicity of CD8+ CTLs in the tumor microenvironment of CRC patients. Given the central role of antigen presentation in activating CD8+ CTLs, we further screened these genes based on the scope of their effects on antigen presentation. To this end, we developed stable clones of OVA expressing MC38 cells (MC38OVA) where OVA-derived peptide, SIINFEKL, will be bound to MHC-I complex for cell surface presentation. 4 genes with highest capacity to alter MHC-I cell surface levels were identified. Our consequent in vivo experiments and in vitro cytotoxicity assays identified that “Rho-GEF” gene was the top actionable target with striking suppressive effects on tumor growth. TCGA database analysis showed Rho-GEF is upregulated in 22% of CRC patients accompanied by a poor prognosis. Rho-GEF knockdown (KD) significantly inhibited tumor growth in immunocompetent mice whereas it only showed minor effects on immunocompromised mice, suggesting that the Rho-GEF may modulate tumor growth by regulating the interaction of tumor cells with non-tumor cells such as immune cells. Consistent with the major contribution of antigen presentation in promoting CD8+ CTLs activity, TNFα, IFNγ, and GZMB levels in CD8+ T cells isolated from Rho-GEF KD MC38-derived tumors showed a significant increase compared to the wild type tumors. Taken together, we introduced Rho-GEF as a potential clinical target involved in CRC immune evasion by modulating antigen presentation and CD8+ CTLs anti-tumor responses. Citation Format: Haniyeh Eyvani, Xinna Zhang. Rho-GEF hampers CD8+T cells-mediated immunosurveillance by reducing antigen presentation [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 1371.

Abstract LB098: Integrative approaches to modulate antigen presentation and boost cancer immune response

Abstract Immune checkpoint blockade (ICB) therapy revolutionized cancer treatment, but patients with impaired MHC-I and/or MHC-II expression show inferior response. We observed differential expression patterns for MHC-I and MHC-II in cancer cells and applied multiple approaches to examine their regulatory mechanisms. To identify the modulators of MHC-I, we combined FACS-based genome-wide CRISPR screens with data-mining from public data. We identified TRAF3, a suppressor of the NFkB pathway, as a negative regulator of MHC-I. The Traf3-knockout gene expression signature is associated with better survival in ICB-naïve patients with cancer and better ICB response. We then screened for drugs with similar transcriptional effects as this signature and identified Second Mitochondria-derived Activator of Caspase (SMAC) mimetics. We experimentally validated that the SMAC mimetic birinapant upregulates MHC-I, sensitizes cancer cells to T cell-dependent killing, and adds to ICB efficacy. In contrast to MHC-I, the expression of MHC-II shows dramatic intra- and inter-sample heterogeneity. To identify the regulators of MHC-II, we conducted data-mining of the transcriptomic and proteomic data from Cancer Cell Line Encyclopedia (CCLE) and multiple melanoma clinical cohorts. We found that a higher cancer-cell-intrinsic MHC-II level is significantly associated with better anti-PD-1 response, and that the Hippo signaling pathway can regulate MHC-II expression in melanoma cells. Our findings provide preclinical rationales for increasing cancer cell MHC-I/MHC-II expression to enhance sensitivity to immunotherapy. Citation Format: Shengqing Gu, Wubing Zhang, Xiaoqing Wang, Peng Jiang, Gordon J. Freeman, Scott J. Rodig, Henry Long, Benjamin E. Gewurz, F. Stephen Hodi, X. Shirley Liu, Myles Brown. Integrative approaches to modulate antigen presentation and boost cancer immune response [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 LB098.

Regulatory role of Transcription factor-EB (TFEB) in parasite control through alteration of antigen presentation in visceral leishmaniasis

Leishmania donovani, an obligate intracellular parasite, the causative agent of visceral leishmaniasis is known to subvert the host immune system for its own survival. Although the precise mechanism is still unknown, emerging evidences indicate that L. donovani efficiently suppress MHC I mediated antigen presentation, rendering inadequate CD8+T cell activation and weakening host defense against parasite. The role of transcription factor EB (TFEB) was recognized in modulating antigen presentation besides its role in lysosomal biogenesis and function. Here, we investigated the regulatory role of TFEB in the modulation of presentation of Leishmania antigen in host tissue. Our results showed an increased expression of TFEB after Leishmania infection both in vitro and in vivo and there was a decrease in the expression of Th-1 cytokine IFNγ along with MHC class I and CD8+T cells indicating attenuation of cell mediated immunity and possibly MHC I restricted antigen presentation. Silencing of TFEB resulted in increased expression of IFNγ and MHC I along with increased CD8+T cells population without any significant change in CD4+T cell number. We also observed a decreased parasite burden in TFEB silenced condition which indicates enhanced parasite clearance by alteration of immunological response possibly through induction of presentation of Leishmania antigen through MHC I. The present study explains the role of TFEB silencing in parasite clearance through regulating the antigen presentation of Leishmania antigen thereby promises to formulate a potential therapeutic strategy against visceral leishmaniasis.

HPV E5 Mediates Resistance to PD-1 Checkpoint Blockade Via Inhibition of MHC and IFN Pathway

<h3>Purpose/Objective(s)</h3> Objective response rates to PD-1 blockade in human papillomavirus (HPV) mediated Head and Neck Squamous cell carcinoma (HNSCC) are low and resistance mechanisms are unclear. HPV oncogenes are known to modulate immune responses; however, the role that they play in limiting responses to PD-1 blockade is poorly understood. Here we investigated HPV oncogenes and uncovered a novel mechanism by which HPV E5 suppresses immune responses and diminishes the activity of PD-1 blockade in HNSCC. <h3>Materials/Methods</h3> Human cell lines were engineered to express HPV E5 and RNAseq was performed to elucidate E5 mediated alterations in transcriptome. MHC class I pull downs and tandem MS/MS was performed to characterize the immunopeptidome and investigate the effect of HPV E5 on the repertoire of presented tumor antigens. Syngeneic murine models were used to dissect molecular mechanisms by which E5 modulates antigen presentation and IFN signaling pathways. Finally, a curated database of tumor RNAseq from 35 HPV-positive HNSCC patients was analyzed to determine the impact of E5 on HLA expression and patient outcomes. <h3>Results</h3> RNAseq revealed dramatic downregulation of antigen processing and type I interferon pathways in E5-expressing human cell lines. Immunopeptidome analysis revealed that E5-expressing cells have a significantly restricted antigen repertoire, indicating that E5 may help HPV mediated tumors escape from host immune surveillance. Remarkably, syngeneic murine tumors expressing HPV E5 were rendered entirely resistant to PD-1 blockade compared to responding parental lines without E5 expression. Mechanistically HPV E5 was demonstrated to suppress phosphorylation of IRF3 and type I interferon production, while directly binding MHC and preventing translocation to the cell surface. Ultimately, we observed a striking improvement in disease free survival (DFS) and overall survival (OS) in patients with low E5 and high HLA expression [Median DFS 50mo in E5 high/HLA-A low versus not reached in E5 low/HLA-A high; p=0.039]. <h3>Conclusion</h3> Our findings establish HPV E5 as a mediator of resistance to PD-1 checkpoint blockade via inhibition of HLA expression and IFN response pathways. These results have broad clinical relevance beyond HNSCC to other HPV-associated malignancies and reveal a powerful mechanism of HPV E5-mediated immunosuppression which can be exploited to improve response rates to PD-1 checkpoint blockade.

Targeting Antigen-Presenting Cells in Multiple Sclerosis Treatment

Multiple sclerosis (MS) is common neurological disease of the central nervous system (CNS) affecting mostly young adults. Despite decades of studies, its etiology and pathogenesis are not fully unraveled and treatment is still insufficient. The vast majority of studies suggest that the immune system plays a major role in MS development. This is also supported by the effectiveness of currently available MS treatments that target immunocompetent cells. In this review, the role of antigen-presenting cells (APC) in MS development as well as the novel therapeutic options targeting those cells in MS are presented. It is known that in MS, peripheral self-antigen-specific immune cells are activated during antigen presentation process and they enter the CNS through the disrupted blood–brain barrier (BBB). Myelin-reactive CD4+ T-cells can be activated by dendritic cells, infiltrating macrophages, microglia cells, or B-cells, which all express MHC class II molecules. There are also suggestions that brain endothelial cells may act as non-professional APCs and present myelin-specific antigens with MHC class II. Similarly, astrocytes, the major glial cells in the CNS, were shown to act as non-professional APCs presenting myelin antigens to autoreactive T-cells. Several currently available MS drugs such as natalizumab, fingolimod, alemtuzumab, and ocrelizumab may modulate antigen presentation in MS. Another way to use this mechanism in MS treatment may be the usage of specific tolerogenic dendritic cells or the induction of tolerance to myelin antigens by peptide vaccines.

Autophagy drives plasticity and functional polarization of tumor-associated macrophages.

Tumor-associated macrophages (TAMs) are a major component of the tumor microenvironment (TME) and are key cells in regulating tumor development, metastasis, immune responses, inflammation, and chemoresistance. In response to TME stimulation, circulating monocytes are recruited and differentiated as TAMs. Most TAMs are defined as alternatively activated (M2) phenotype to create immunosuppressive TME and support tumor progression. In contrast, classically activated (M1) TAMs can produce pro-inflammatory cytokines and enhance immune responses against tumor development. Autophagy is a conserved catabolic process to control cellular homeostasis and biological function. Emerging evidence reveals crucial contribution of autophagy in modulating TAM plasticity and functional polarization in TME. In this review, we introduce the current understanding of autophagy-regulated TAM function in development of cancer. We focus on how autophagy modulates antigen presentation, LC3-associated phagocytosis, cytokine secretion, inflammasome regulation, recruitment, differentiation, and polarization of TAMs and suggest strategies for potential therapeutics by targeting autophagy in TAMs. We expect this review can provide a new notion of future cancer immunotherapy.

Abstract 1661: Immune modulation by the dual-mechanism ERK inhibitor, ASTX029, in MAPK-activated tumor models

Abstract Whilst mitogen-activated protein kinase (MAPK) pathway inhibitors are approved therapies in mutant-BRAF driven cancers and have demonstrated a high response rate in the clinic, the duration of response is often short-lived. Approaches targeting the immune system have elicited durable responses and led to the approval of checkpoint inhibitors such as the anti-PD1 therapy, pembrolizumab, in indications where MAPK pathway activation is often observed, such as melanoma. Activation of the MAPK pathway has been associated with an immunosuppressive tumor microenvironment (TME). Further, preclinical studies have demonstrated that in addition to inhibiting MAPK activity in tumor cells, MAPK pathway inhibitors such as the BRAFV600E inhibitor dabrafenib or MEK inhibitor trametinib have promoted a more proinflammatory TME leading to upregulated antigen presentation on tumor cells, increased CD8+ T cell infiltration and tumor cell killing. Similar preclinical results were recently reported for a KRASG12C inhibitor, AMG 510, where treatment of in vivo models led to an increase in tumor infiltrating lymphocytes, macrophages, dendritic cells and an increase in active immune gene signatures leading to tumor immunity. We have recently described the discovery of ASTX029, which is currently undergoing clinical development in advanced solid tumors (NCT03520075). ASTX029 is a dual-mechanism ERK1/2 (ERK) inhibitor, inhibiting both the catalytic activity and phosphorylation of ERK, and shows potent inhibition of MAPK-activated tumor growth in preclinical models. Previous studies have demonstrated a difference in regulation of genes involved in response to type I interferon following treatment with dual-mechanism compared to catalytic ERK inhibitors. We investigated whether treatment with ASTX029 modulates antigen presentation and the TME in MAPK-activated tumors. Following treatment of cell lines in vitro, we observed ASTX029-dependent changes consistent with increased antigen presentation, including an increase in cell surface expression of MHC class I and the increase in gene expression of tumor-specific antigens gp100 and MART-1 following treatment of melanoma cells. We have previously demonstrated that ASTX029 has good bioavailability following oral dosing in mice. To further investigate the effect of ASTX029 on the TME, syngeneic tumors grown in immunocompetent mice dosed with ASTX029 were characterized in terms of immune cell composition of the TME and gene expression. Our results were consistent with increased immune activation, including increased interferon signaling and a change in the immune cell composition of the TME. These data demonstrate that treatment with ASTX029 leads to modulation of the TME and we hypothesize that to optimize therapeutic activity, ASTX029 could be partnered either with an immunomodulatory or tumor-directed agent. Citation Format: Chris Hindley, Andrea Biondo, Kim-Hien Dao, Matthew Davis, Lynsey Fazal, Roberta Ferraldeschi, Keisha Hearn, Vanessa Martins, Harpreet Saini, Martin Sims, Nicola Wallis, Nicola Wilsher, Harold Keer, John Lyons, Joanne Munck. Immune modulation by the dual-mechanism ERK inhibitor, ASTX029, in MAPK-activated tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1661.

Tolerogenic effects of 1,25-dihydroxyvitamin D on dendritic cells involve induction of fatty acid synthesis

The active form of vitamin D, 1,25-dihydroxyvitamin D (1,25D) is a potent regulator of immune function, promoting anti-inflammatory, tolerogenic T cell responses by modulating antigen presentation by dendritic cells (DC). Transcriptomic analyses indicate that DC responses to 1,25D involve changes in glycolysis, oxidative phosphorylation, electron transport and the TCA cycle. To determine the functional impact of 1,25D-mediated metabolic remodelling, human monocyte-derived DC were differentiated to immature (+vehicle, iDC), mature (+LPS, mDC), and immature tolerogenic DC (+1,25D, itolDC) and characterised for metabolic function. In contrast to mDC which showed no change in respiration, itolDC showed increased basal and ATP-linked respiration relative to iDC. Tracer metabolite analyses using 13C -labeled glucose showed increased lactate and TCA cycle metabolites. Analysis of lipophilic metabolites of 13C-glucose revealed significant incorporation of label in palmitate and palmitoleate, indicating that 1,25D promotes metabolic fatty acid synthesis in itolDC. Inhibition of fatty acid synthesis in itolDC altered itolDC morphology and suppressed expression of CD14 and IL-10 by these cells. These data indicate that the ability of 1,25D to induce tolerogenic DC involves metabolic remodelling leading to synthesis of fatty acids.

Mycobacterium smegmatis Bacteria Expressing Mycobacterium tuberculosis-Specific Rv1954A Induce Macrophage Activation and Modulate the Immune Response

Mycobacterium tuberculosis (M. tb), the intracellular pathogen causing tuberculosis, has developed mechanisms that endow infectivity and allow it to modulate host immune response for its survival. Genomic and proteomic analyses of non-pathogenic and pathogenic mycobacteria showed presence of genes and proteins that are specific to M. tb. In silico studies predicted that M.tb Rv1954A is a hypothetical secretory protein that exhibits intrinsically disordered regions and possess B cell/T cell epitopes. Treatment of macrophages with Rv1954A led to TLR4-mediated activation with concomitant increase in secretion of pro-inflammatory cytokines, IL-12 and TNF-α. In vitro studies showed that rRv1954A protein or Rv1954A knock-in M. smegmatis (Ms_Rv1954A) activates macrophages by enhancing the expression of CD80 and CD86. An upregulation in the expression of CD40 and MHC I/II was noted in the presence of Rv1954A, pointing to its role in enhancing the association of APCs with T cells and in the modulation of antigen presentation, respectively. Ms_Rv1954A showed increased infectivity, induction of ROS and RNS, and apoptosis in RAW264.7 macrophage cells. Rv1954A imparted protection against oxidative and nitrosative stress, thereby enhancing the survival of Ms_Rv1954A inside macrophages. Mice immunized with Ms_Rv1954A showed that splenomegaly and primed splenocytes restimulated with Rv1954A elicited a Th1 response. Infection of Ms_Rv1954A in mice through intratracheal instillation leads to enhanced infiltration of lymphocytes in the lungs without formation of granuloma. While Rv1954A is immunogenic, it did not cause adverse pathology. Purified Rv1954A or Rv1954A knock-in M. smegmatis (Ms_Rv1954A) elicited a nearly two-fold higher titer of IgG response in mice, and PTB patients possess a higher IgG titer against Rv1954A, also pointing to its utility as a diagnostic marker for TB. The observed modulation of innate and adaptive immunity renders Rv1954A a vital protein in the pathophysiology of this pathogen.

Abstract 6615: Peroxynitrite mediates immune escape of tumor cells from cytotoxic T cells in situ

Abstract Despite improved ability to generate strong tumor-specific T cell responses, clinical benefits remain relatively moderate. Only a small proportion of predicted neoepitopes was shown to induce specific cytotoxic T cells (CTLs) or serve as an efficient target for T cell-based therapy. We suggest here that low efficacy of CTLs could be at least partially explained by the fact that tumor microenvironment (TME) modulates antigen presentation and epitope profile expressed by tumor. As a result, tumor escapes recognition by CTLs. TME is enriched in peroxynitrite (PNT), a potent oxidant. It is mostly produced by infiltrating myeloid cells, but also by some tumors (as melanoma). We hypothesized that PNT is able to affect antigen presentation on tumor cells and facilitates tumor immune escape. To check this hypothesis, we treated murine EG7 tumor cells with PNT, isolated MHC I peptides and compared their expression on treated versus non-treated cells using SILAC mass spectrometry. We found that PNT treatment significantly decreased expression of a portion of MHC I peptides presented by tumor cells, whereas other peptides remained relatively intact. We found that PNT-sensitive and resistant peptides demonstrated similar binding capacity to MHC I. However, the off-rate of PNT-sensitive peptides was significantly higher. PNT strongly affected proteasomal activity of tumor cells suggesting the mechanism for under-representation of MHC I peptides with high off-rate level. To investigate the biological role of this effect, we generated CTLs specific to a pool of PNT-sensitive or resistant peptides. In vitro we observed that both types of CTLs effectively killed tumor cells. Pre-treatment of tumor cells with PNT significantly reduced killing only by CTLs specific to PNT-sensitive peptides. By ELISPOT we showed that most of antitumor-specific CTL responses in mice with different tumors were induced against PNT-resistant, but not PNT-sensitive species. Moreover, the adoptive transfer of CTLs specific to PNT-resistant peptides combined with immune checkpoint inhibition (ICI) was able to induce tumor rejection in 70% of mice, whereas similar setting for CTLs specific to PNT-sensitive peptides didn't affect tumor growth. PNT inhibition combined with ICI significantly delayed the tumor growth in mice. In addition, we showed that PNT had similar effect on MHC I peptide profile for human melanoma cells. Finally, we measured nitrotyrosine (NT) level (marker of PNT presence) in tumor tissues resected from melanoma patients before the start of ICI therapy. We retrospectively correlated NT levels with patient ability to respond to ICI therapy. We found that high NT level was a predictor of poor prognosis and patient un-responsiveness to ICI. Overall, our study demonstrates PNT ability to affect antigen presentation in tumor site. In addition, we suggest PNT as a promising target for ICI-combined therapy as well as a biomarker for resistance to ICI. Citation Format: Evgenii N. Tcyganov, Dmitry I. Gabrilovich. Peroxynitrite mediates immune escape of tumor cells from cytotoxic T cells in situ [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6615.

Transplantation-Induced Ischemia-Reperfusion Injury Modulates Antigen Presentation by Donor Renal CD11c+F4/80+ Macrophages through IL-1R8 Regulation.

In donor kidneys subjected to ischemia-reperfusion injury during kidney transplant, phagocytes coexpressing the F4/80 and CD11c molecules mediate proinflammatory responses and trigger adaptive immunity in transplantation through antigen presentation. After injury, however, resident renal macrophages coexpressing these surface markers acquire a proreparative phenotype, which is pivotal in controlling inflammation and fibrosis. No data are currently available regarding the effects of transplant-induced ischemia-reperfusion injury on the ability of donor-derived resident renal macrophages to act as professional antigen-presenting cells. We evaluated the phenotype and function of intragraft CD11c+F4/80+ renal macrophages after cold ischemia. We also assessed the modifications of donor renal macrophages after reversible ischemia-reperfusion injury in a mouse model of congeneic renal transplantation. To investigate the role played by IL-1R8, we conducted in vitro and in vivo studies comparing cells and grafts from wild-type and IL-R8-deficient donors. Cold ischemia and reversible ischemia-reperfusion injury dampened antigen presentation by renal macrophages, skewed their polarization toward the M2 phenotype, and increased surface expression of IL-1R8, diminishing activation mediated by toll-like receptor 4. Ischemic IL-1R8-deficient donor renal macrophages acquired an M1 phenotype, effectively induced IFNγ and IL-17 responses, and failed to orchestrate tissue repair, resulting in severe graft fibrosis and aberrant humoral immune responses. IL-1R8 is a key regulator of donor renal macrophage functions after ischemia-reperfusion injury, crucial to guiding the phenotype and antigen-presenting role of these cells. It may therefore represent an intriguing pathway to explore with respect to modulating responses against autoantigens and alloantigens after kidney transplant.

Bacterial extracellular vesicle-coated multi-antigenic nanovaccines protect against drug-resistant Staphylococcus aureus infection by modulating antigen processing and presentation pathways.

Background: Vaccination provides an alternative to antibiotics in addressing drug-resistant Staphylococcus aureus (S. aureus) infection. However, vaccine potency is often limited by a lack of antigenic breadth and a demand on the generation of antibody responses alone.Methods: In this study, bacterial extracellular vesicles (EVs) coating indocyanine green (ICG)-loaded magnetic mesoporous silica nanoparticles (MSN) were constructed as multi-antigenic vaccines (EV/ICG/MSN) with the ability to modulate antigen presentation pathways in dendritic cells (DCs) to induce cellular immune responses.Results: Exposing the EV/ICG/MSNs to a laser could promote DC maturation and enhance the proteasome-dependent antigen presentation pathway by facilitating endolysosomal escape, improving proteasome activity, and elevating MHC-I expression. Immunization by EV/ICG/MSNs with laser irradiation in vivo triggered improved CD8+ T cell responses while maintaining CD4+ T cell responses and humoral immunity. In addition, in vivo tracking data revealed that the vaccine could be efficiently transported from the injection site into lymph nodes. Skin infection experiments showed that the vaccine not only prevented and treated superficial infection but also decreased bacterial invasiveness, thus strongly suggesting that EV/ICG/MSNs were effective in preventing complications resulting from the introduction of S. aureus infections.Conclusion: This multi-antigenic nanovaccine-based modulation of antigen presentation pathways provides an effective strategy against drug-resistant S. aureus infection.

Let-7 MicroRNAs Regulate Microglial Function and Suppress Glioma Growth through Toll-Like Receptor 7

Microglia express Toll-like receptors (TLRs) that sense pathogen- and host-derived factors, including single-stranded RNA. In the brain, let-7 microRNA (miRNA) family members are abundantly expressed, and some have recently been shown to serve as TLR7 ligands. We investigated whether let-7 miRNA family members differentially control microglia biology in health and disease. We found that a subset of let-7 miRNA family members function as signaling molecules to induce microglial release of inflammatory cytokines, modulate antigen presentation, and attenuate cell migration in a TLR7-dependent manner. The capability of the let-7 miRNAs to control microglial function is sequence specific, mapping to a let-7 UUGU motif. In human and murine glioblastoma/glioma, let-7 miRNAs are differentially expressed and reduce murine GL261 glioma growth in the same sequence-specific fashion through microglial TLR7. Taken together, these data establish let-7 miRNAs as key TLR7 signaling activators that serve to regulate the diverse functions of microglia in health and glioma.

Peri-Transplant Steroids Enhance GVL and Attenuate GVHD By Redistributing Alloreactive Donor T Cells from the Gut into the Bone Marrow

Leukemia relapse represents a failure of graft-versus-leukemia (GVL) and remains the major limitation of allogeneic stem cell/bone marrow transplantation (BMT). Graft-versus-host disease (GVHD) within the gastrointestinal (GI) tract is the principal determinant of transplant-related mortality and is initiated by a network of alloantigen presentation by professional and non-professional APC that prime donor T cells in the GI tract and related lymphoid structures. Since GVL and lethal GVHD are mediated by donor T cells at spatially distinct sites; bone marrow (BM) and the GI tract respectively, we sought tractable approaches to spatially separate alloreactive responses at these two locations. The administration of high dose steroids in the peri-transplant period is permissive of T cell replete HLA-haploidentical BMT and significant GVL effects (Ogawa H, et al. BBMT. 2006). We utilized murine haploidentical BMT models (B6D2F1 → B6C3F1, B6 → B6D2F1) with recipient background MLL/AF9 primary acute myeloid leukemia (AML), with or without dexamethasone (Dex) administration (5 mg/kg/day i.p., days -1 to +5). Dex-treatment improved transplant survival (from 25% to 68% at day 100, P=0.0012) with significant reductions in GVHD histopathology specifically in the colon (histopathology scores 8.7±1.0 vs 4.6±0.8, P&lt; 0.05), despite excellent leukemia control. To understand this paradox, we analyzed the kinetics of donor T cell expansion after BMT. In the mesenteric lymph node (mLN), Dex treatment significantly suppressed the expansion of both CD4 and CD8 T cells (3.3±0.3 x 105 vs 1.4±0.3 x 105, P&lt; 0.001 and 4.2±0.4 x 105 vs 2.1±0.4 x 105, P&lt; 0.01 respectively) and the activation of CD4 T cells (CD25 MFI: 2021±146 vs 1056±102, P&lt; 0.01). In contrast, donor effector/memory CD44+ CD8 T cells were expanded in the BM of Dex treated recipients (1.9±0.3 x 105 vs 3.1±0.4 x 105, P&lt; 0.05) that demonstrated high per cell cytolytic activity against leukemia (specific lysis: 65±2.4 % vs 62±2.6 % in untreated vs Dex-treated, P&gt; 0.05). Surprisingly, there was no difference in proliferation (cell tracking dye dilution: 63±5.5 % vs 57±5.5 % in untreated vs Dex-treated, P&gt; 0.05) or apoptosis (caspase-3: 6.6±0.4 % vs 6.1±0.6 %, caspase-8: 20±1.6 % vs 17±3.3 % in untreated vs Dex-treated, respectively, P&gt; 0.05) of CD4 T cells in the mLN between the two groups. We undertook experiments with luciferase expressing T cells and noted that Dex-treatment preferentially inhibited T cell accumulation in the GI tract, but not marrow after BMT. Thus, it appeared that Dex treatment preferentially re-distributed donor T cells from the GI tract to the bone marrow. We next determined if Dex exerted effects via direct signaling to the donor T cell. We thus transplanted glucocorticoid receptor (GR)-deficient or intact T cells (GRfl/fl lck-Cre mice). Dex-treatment reduced donor CD4 T cell expansion in the mLN independent of their expression of the GR (untreated vs Dex-treated: 2.8±0.6 x 105 vs 1.2±0.3 x 105, lckCREGRfl/fl and 2.4±0.3 x 105 vs 1.4±0.4 x 105, GRfl/fl littermates, P&lt; 0.05 both groups). Thus steroid effects were mediated indirectly, putatively via effects on recipient alloantigen presentation. There was a marked reduction in recipient dendritic cells (DC) and macrophages expressing the Ea peptide within MHC class II in the GI tract of Dex-treated recipients (terminal Ileum YAe+ DC number 896±93 vs 356±40, P&lt; 0.01, YAe+ macrophage number 1035±136 vs 355±97, P&lt; 0.01). In conjunction with this, expression of the gut homing integrin a4b7 expression was reduced in CD4 T cells from Dex treated recipient mLN (25±1.6 % vs 17±1.7 %, P&lt; 0.01), while the marrow homing integrin VLA-4 (a4b1) was increased (a4: 62±2.2 % vs 75±1.6 %, P&lt; 0.001, b1: 52±2.5 % vs 61±1.6 %, P&lt; 0.05) in donor CD8 T cells from Dex treated recipient BM. Finally, Dex treatment enhanced GVL against a second primary AML (BCR/ABL-NUP98/HOXA9) relative to untreated recipients and those receiving post-transplant cyclophosphamide (PT-Cy) (relapse rate: 0% vs 40% vs 100% at day 35 in Dex vs untreated vs PT-Cy, PT-Cy vs Dex-treated, P&lt; 0.0001; untreated vs Dex-treated, P=0.029). These data suggest a potential therapeutic strategy to modulate antigen presentation in the GI tract and consequent integrin imprinting that minimizes GVHD lethality whilst enhancing GVL within BM. Disclosures No relevant conflicts of interest to declare.

DUX4 Suppresses MHC Class I to Promote Cancer Immune Evasion and Resistance to Checkpoint Blockade

Advances in cancer immunotherapies make it critical to identify genes that modulate antigen presentation and tumor-immune interactions. We report that DUX4, an early embryonic transcription factor that is normally silenced in somatic tissues, is re-expressed in diverse solid cancers. Both cis-acting inherited genetic variation and somatically acquired mutations in trans-acting repressors contribute to DUX4 re-expression in cancer. Although many DUX4 target genes encode self-antigens, DUX4-expressing cancers were paradoxically characterized by reduced markers of anti-tumor cytolytic activity and lower major histocompatibility complex (MHC) class I gene expression. We demonstrate that DUX4 expression blocks interferon-γ-mediated induction of MHC classI, implicating suppressed antigen presentation in DUX4-mediated immune evasion. Clinical data in metastatic melanoma confirmed that DUX4 expression was associated with significantly reduced progression-free and overall survival in response to anti-CTLA-4. Our results demonstrate that cancers can escape immune surveillance by reactivating a normal developmental pathway and identify a therapeutically relevant mechanism of cell-intrinsic immune evasion.

Immunobiology of Varicella-Zoster Virus Infection.

Varicella-zoster virus (VZV) causes clinically significant illness during acute and recurrent infection accompanied by robust innate and acquired immune responses. Innate immune cells in skin and ganglion secrete type I interferon (IFN-I) and proinflammatory cytokines to control VZV. Varicella-zoster virus subverts pattern recognition receptor sensing to modulate antigen presentation and IFN-I production. During primary infection, VZV hijacks T cells to disseminate to the skin and establishes latency in ganglia. Durable T- and B-cell memory formed within a few weeks of infection is boosted by reactivation or re-exposure. Antigen-specific T cells are recruited and potentially retained in VZV-infected skin to counteract reactivation. In latently VZV-infected ganglia, however, virus-specific T cells have not been recovered, suggesting that local innate immune responses control VZV latency. Antibodies prevent primary VZV infection, whereas T cells are fundamental to resolving disease, limiting severity, and preventing reactivation. In this study, we review current knowledge on the interactions between VZV and the human immune system.

Shaping the humoral immune response: Actin regulators modulate antigen presentation and influence B-T interactions

B cells are an integral part of the adaptive immune system. During an immune response, the actin cytoskeleton plays a central role in regulating B cell antigen uptake, polarization and presentation as well as B cell migration and interaction with T cells. Genetic defects affecting actin regulators can result in reduced B cell activation, limited antibody production and hence cause disease. In this review, we discuss molecular mechanisms of actin regulation and their involvement in antigen polarisation and presentation, as well as their role in influencing interactions between B and T cells. Improved understanding of these mechanisms is necessary for the development of new therapeutic options modulating humoral immune responses.