Flow cytometry-based high-throughput RNAi screening for miRNAs regulating MHC class II HLA-DR surface expression.

HLA-DR isotype is a MHC-II cell-surface receptor found on APCs and plays a key role in initiating immune responses. In severely immunocompromised patients with conditions like sepsis, the number of HLA-DR molecules expressed on leukocytes is considered to correlate with infectious complications and patients' probability of survival. The underlying regulatory mechanisms of HLA-DR expression remain largely unknown. One probable path to regulation is through microRNAs (miRNAs), which have been implicated as regulatory elements of both innate and adaptive immune system development and function. In our study, flow cytometry-based high-throughput miRNA screening was performed in a stable HLA-DR-expressing human melanoma cell line, MelJuSo, for either up- or downregulating miRNAs of the surface HLA-DR expression. By the end of the screening, the top ten upregulators and top five downregulators were identified, and both the HLA-DR protein and mRNA regulations were further verified and validated. In-silico approaches were applied for functional miRNA-mRNA interaction prediction. The potential underlying gene regulations of different miRNAs were proposed. Our results promote the study of miRNA-mediated HLA-DR regulation under both physiological and pathological conditions, and may pave the way for potential clinical applications.

Mycobacterium tuberculosis Ag85b:hfcγ1 recombinant fusion protein as a selective receptor-dependent delivery system for antigen presentation.

Introducing an effective vaccine for tuberculosis (TB) is an urgent need. Mycobacterium tuberculosis (Mtb) Ag85 complex is suggested for making protective immunodominant antigens for design and development of novel TB vaccine. In the present study, a pDR2EF1-Fcγ1 vector has been used to make Ag85B:hFcγ1 recombinant fusion protein. Briefly, specific XbaI and NotI site incorporated primers were used to amplify Mtb-fbpB gene by PCR, TA-cloned and amplified in E.coli DH5α. The resulting vector then subcloned into the pDR2EF1.Fcγ1 vector and transferred to Chinese hamster ovary (CHO) cell line. DNA sequencing was performed to confirm that Ag85B:hFcγ1 construct is precise and in-frame. Then, Ag85B:hFcγ1 protein was produced by CHO expression system and recombinant protein was purified using HiTrap rProtein A Sepharose Fast Flow column. The presence of recombinant fusion protein confirmed by immunofluorescence (IFA) and Western blotting (WB). This fusion protein containing Fc fragment of human IgG1, apart from stability and adjuvanticity potential, could bind to FcRγI (CD64) on the surface of antigen-presenting cells (APCs) and induce cross-presentation in favour of host immune response and can be used as a potential candidate along with other subunit vaccines against Mtb.

Depletion of donor dendritic cells ameliorates immunogenicity of both skin and hind limb transplants.

Acute cellular rejection remains a significant obstacle affecting successful outcomes of organ transplantation including vascularized composite tissue allografts (VCA). Donor antigen presenting cells (APCs), particularly dendritic cells (DCs), orchestrate early alloimmune responses by activating recipient effector T cells. Employing a targeted approach, we investigated the impact of donor-derived conventional DCs (cDCs) and APCs on the immunogenicity of skin and skin-containing VCA grafts, using mouse models of skin and hind limb transplantation. By post-transplantation day 6, skin grafts demonstrated severe rejections, characterized by predominance of recipient CD4 T cells. In contrast, hind limb grafts showed moderate rejection, primarily infiltrated by CD8 T cells. Notably, the skin component exhibited heightened immunogenicity when compared to the entire VCA, evidenced by increased frequencies of pan (CD11b-CD11c+), mature (CD11b-CD11c+MHCII+) and active (CD11b-CD11c+CD40+) DCs and cDC2 subset (CD11b+CD11c+ MHCII+) in the lymphoid tissues and the blood of skin transplant recipients. While donor depletion of cDC and APC reduced frequencies, maturation and activation of DCs in all analyzed tissues of skin transplant recipients, reduction in DC activities was only observed in the spleen of hind limb recipients. Donor cDC and APC depletion did not impact all lymphocyte compartments but significantly affected CD8 T cells and activated CD4 T in lymph nodes of skin recipients. Moreover, both donor APC and cDC depletion attenuated the Th17 immune response, evident by significantly reduced Th17 (CD4+IL-17+) cells in the spleen of skin recipients and reduced levels of IL-17E and lymphotoxin-α in the serum samples of both skin and hind limb recipients. In conclusion, our findings underscore the highly immunogenic nature of skin component in VCA. The depletion of donor APCs and cDCs mitigates the immunogenicity of skin grafts while exerting minimal impact on VCA.

PKHB1 peptide induces antiviral effects through induction of immunogenic cell death in herpes simplex keratitis.

Herpes simplex keratitis (HSK) is a severe, infectious corneal disease caused by herpes simplex virus type 1 (HSV-1) infection. The increasing prevalence of acyclovir resistance, the side effects of hormonal drugs, and the ease of recurrence after surgery have made it crucial to develop new methods of treating HSK. HSV-1 evades the host immune response through various mechanisms. Therefore, we explored the role of the immunogenic cell death inducer PKHB1 peptide in HSK. After subconjunctival injection of PKHB1 peptide, we observed the ocular surface lesions and survival of HSK mice and detected the virus levels in tear fluid, corneas, and trigeminal ganglions. We found that PKHB1 peptide reduced HSV-1 levels in the eye and alleviated the severity of HSK. Moreover, it increased the number of corneal infiltrating antigen-presenting cells (APCs), such as macrophages and dendritic cells, and CD8+ T cells in ocular draining lymph nodes. We further observed that PKHB1 peptide promoted the exposure of calreticulin, as well as the release of ATP and high-mobility group box 1 in HSV-1-infected cells in vitro. Our findings suggested that PKHB1 peptide promoted the recruitment and maturation of APCs by inducing the release of large amounts of damage-associated molecular patterns from infected cells. APCs then phagocytized antigenic materials and translocated to the lymph nodes, triggering a cytotoxic T lymphocyte-dependent immune response that ultimately alleviated HSK.

Review: Development of SARS-CoV-2 immuno-enhanced COVID-19 vaccines with nano-platform.

Vaccination is the most effective way to prevent coronavirus disease 2019 (COVID-19). Vaccine development approaches consist of viral vector vaccines, DNA vaccine, RNA vaccine, live attenuated virus, and recombinant proteins, which elicit a specific immune response. The use of nanoparticles displaying antigen is one of the alternative approaches to conventional vaccines. This is due to the fact that nano-based vaccines are stable, able to target, form images, and offer an opportunity to enhance the immune responses. The diameters of ultrafine nanoparticles are in the range of 1-100 nm. The application of nanotechnology on vaccine design provides precise fabrication of nanomaterials with desirable properties and ability to eliminate undesirable features. To be successful, nanomaterials must be uptaken into the cell, especially into the target and able to modulate cellular functions at the subcellular levels. The advantages of nano-based vaccines are the ability to protect a cargo such as RNA, DNA, protein, or synthesis substance and have enhanced stability in a broad range of pH, ambient temperatures, and humidity for long-term storage. Moreover, nano-based vaccines can be engineered to overcome biological barriers such as nonspecific distribution in order to elicit functions in antigen presenting cells. In this review, we will summarize on the developing COVID-19 vaccine strategies and how the nanotechnology can enhance antigen presentation and strong immunogenicity using advanced technology in nanocarrier to deliver antigens. The discussion about their safe, effective, and affordable vaccines to immunize against COVID-19 will be highlighted.

Immune Modulation by Antigenic Peptides and Antigenic Peptide Conjugates for Treatment of Multiple Sclerosis.

The immune system defends our body by fighting infection from pathogens utilizing both the innate and adaptive immune responses. The innate immune response is generated rapidly as the first line of defense. It is followed by the adaptive immune response that selectively targets infected cells. The adaptive immune response is generated more slowly, but selectively, by targeting a wide range of foreign particles (i.e., viruses or bacteria) or molecules that enter the body, known as antigens. Autoimmune diseases are the results of immune system glitches, where the body's adaptive system recognizes self-antigens as foreign. Thus, the host immune system attacks the self-tissues or organs with a high level of inflammation and causes debilitation in patients. Many current treatments for autoimmune diseases (i.e., multiple sclerosis (MS), rheumatoid arthritis (RA)) have been effective but lead to adverse side effects due to general immune system suppression, which makes patients vulnerable to opportunistic infections. To counter these negative effects, many different avenues of antigen specific treatments are being developed to selectively target the autoreactive immune cells for a specific self-antigen or set of self-antigens while not compromising the general immune system. These approaches include soluble antigenic peptides, bifunctional peptide inhibitors (BPI) including IDAC and Fc-BPI, polymer conjugates, and peptide-drug conjugates. Here, various antigen-specific methods of potential treatments, their efficacy, and limitations will be discussed along with the potential mechanisms of action.

Intranasal vaccines for SARS-CoV-2: From challenges to potential in COVID-19 management.

Unlike conventional Coronavirus 2019 (COVID-19) vaccines, intranasal vaccines display a superior advantage because the nasal mucosa is often the initial site of infection. Preclinical and clinical studies concerning intranasal immunization elicit high neutralizing antibody generation and mucosal IgA and T cell responses that avoid severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in both; the upper and lower respiratory tract. A nasal formulation is non-invasive with high appeal to patients. Intranasal vaccines enable self-administration and can be designed to survive at ambient temperatures, thereby simplifying logistical aspects of transport and storage. In this review, we provide an overview of nasal vaccines with a focus on formulation development as well as ongoing preclinical and clinical studies for SARS-CoV-2 intranasal vaccine products.

Recent Advances and Future Perspectives in Polymer-Based Nanovaccines.

Vaccination is the most valuable and cost-effective health measure to prevent and control the spread of infectious diseases. A significant number of infectious diseases and chronic disorders are still not preventable by existing vaccination schemes; therefore, new-generation vaccines are needed. Novel technologies such as nanoparticulate systems and adjuvants can enable safe and effective vaccines for difficult target populations such as newborns, elderly, and the immune-compromised. More recently, polymer-based particles have found application as vaccine platforms and vaccine adjuvants due to their ability to prevent antigen degradation and clearance, coupled with enhanced uptake by professional antigen-presenting cells (APCs). Polymeric nanoparticles have been applied in vaccine delivery, showing significant adjuvant effects as they can easily be taken up by APCs. In other words, polymer-based systems offer a lot of advantages, including versatility and flexibility in the design process, the ability to incorporate a range of immunomodulators/antigens, mimicking infection in different ways, and acting as a depot, thereby persisting long enough to generate adaptive immune responses. The aim of this review is to summarize the properties, the characteristics, the added value, and the limitations of the polymer-based nanovaccines, as well as the process of their development by the pharmaceutical industry.

Exosomes Recovered From the Plasma of COVID-19 Patients Expose SARS-CoV-2 Spike-Derived Fragments and Contribute to the Adaptive Immune Response.

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by beta-coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that has rapidly spread across the globe starting from February 2020. It is well established that during viral infection, extracellular vesicles become delivery/presenting vectors of viral material. However, studies regarding extracellular vesicle function in COVID-19 pathology are still scanty. Here, we performed a comparative study on exosomes recovered from the plasma of either MILD or SEVERE COVID-19 patients. We show that although both types of vesicles efficiently display SARS-CoV-2 spike-derived peptides and carry immunomodulatory molecules, only those of MILD patients are capable of efficiently regulating antigen-specific CD4+ T-cell responses. Accordingly, by mass spectrometry, we show that the proteome of exosomes of MILD patients correlates with a proper functioning of the immune system, while that of SEVERE patients is associated with increased and chronic inflammation. Overall, we show that exosomes recovered from the plasma of COVID-19 patients possess SARS-CoV-2-derived protein material, have an active role in enhancing the immune response, and possess a cargo that reflects the pathological state of patients in the acute phase of the disease.

Loss of the virulence plasmid by Shigella sonnei promotes its interactions with CD207 and CD209 receptors.

Introduction. Shigella sonnei, the cause of bacillary dysentery, belongs to Gram-negative enteropathogenic bacteria. S. sonnei contains a 210 kb virulence plasmid that encodes an O-antigen gene cluster of LPSs. However, this virulence plasmid is frequently lost during replication. It is well-documented that after losing the O-antigen and becoming rough strains, the Gram-negative bacteria may express an LPS core on its surface. Previous studies have suggested that by using the LPS core, Gram-negative bacteria can interact with several C-type lectin receptors that are expressed on antigen-presenting cells (APCs).Hypothesis/Gap Statement. S. sonnei by losing the virulence plasmid may hijack APCs via the interactions of LPS-CD209/CD207.Aim. This study aimed to investigate if the S. sonnei rough strain, by losing the virulence plasmid, interacted with APCs that express C-type lectins of human CD207, human CD209a and mouse CD209b.Methodology. SDS-PAGE silver staining was used to examine the O-antigen expression of S. sonnei WT and its rough strain. Invasion assays and inhibition assays were used to examine the ability of S. sonnei WT and its rough strain to invade APCs and investigate whether CD209 and CD207 are receptors for phagocytosis of rough S. sonnei. Animal assays were used to observe the dissemination of S. sonnei.Results. S. sonnei did not express O-antigens after losing the virulence plasmid. The S. sonnei rough strain invades with APCs, including human dendritic cells (DCs) and mouse macrophages. CD209 and CD207 are receptors for phagocytosis of rough S. sonnei. Expression of the O-antigen reduces the ability of the S. sonnei rough strain to be disseminated to mesenteric lymph nodes and spleens.Conclusion. This work demonstrated that S. sonnei rough strains - by losing the virulence plasmid - invaded APCs through interactions with CD209 and CD207 receptors.

Bio-Inorganic Hybrid Nongenetically Modified Viruses as an Immune Agonist for Systemic Elimination of Cancer Cells.

Microbial-based cancer therapy is nowadays considered as an interesting approach, especially with viruses which are attracting more attention owing to their simple structure and nanoscale. However, because of the need for cumbersome genetic modification and poor biosafety, its application is seriously limited. Here, nonpathogenic natural Sendai viruses (SEVs) are used as an alternative immune agonist after being mineralized by calcium ions. Both in vitro and in vivo studies indicated that virus-inorganic hybrids can effectively excite antigen-presenting cells (APCs). Then, the tumor antigens were released in large amounts by photothermal damage. Meanwhile, these released antigens were presented to lymph nodes to mature antitumor T lymphocytes via the peritumoral APCs previously recruited by the SEV. Our results demonstrated that even after administration at one point, the nanohybrids could still effectively stimulate systemic antitumor immune response to suppress the potential cancer metastatic spread. The bio-inorganic hybrid nongenetically modified virus-inorganic nanocomposites might serve as an alternative strategy for synergistic immune therapy.

A case series and literature review of multiple sclerosis and COVID-19: Clinical characteristics, outcomes and a brief review of immunotherapies.

BACKGROUND: In view of the emerging coronavirus pandemic, the demand for knowledge about the impact of SARS-CoV-2 on people with Multiple Sclerosis (MS) continues to grow. Patients receiving disease modifying therapy (DMT) for MS have a higher background risk of infection-related health care utilization when compared to the general population. Therefore, there is a need of evidence-based recommendations to reduce the risk of infection and also managing MS patients with SARS-CoV-2. CASE DESCRIPTION: We present three patients with history of Multiple Sclerosis (MS) on DMTs presenting with worsening MS symptoms likely pseudo exacerbation who were diagnosed with COVID-19. DISCUSSION: An extensive review of 7 articles was performed, in addition to a brief review on DMTs use in MS patients with COVID-19. In our cases, all patients were on DMT and severe course of disease was noted in 2 cases. No fatality was observed. CONCLUSIONS: This review provides a base on the clinical characteristics, outcomes and the roles of DMTs in MS patients suffering from n-cov-2. Physicians need to be vigilant about considering COVID-19 infection related relapse in the MS patients, especially in this COVID-19 pandemic era and look for pseudo-exacerbation. As most cases are found to have mild course and full recovery on DMTs, further research is needed to formulate evidence-based guidelines. This review will particularly be helpful for the researchers and registries to collect future data on MS and COVID-19.

RNA-loaded dendritic cells: more than a tour de force in cancer therapeutics.

A wide array of therapeutic strategies has been implemented against cancers, yet their clinical benefit is limited. The lack of clinical efficacy of the conventional treatment options might be due to the inept immune competency of the patients. Dendritic cells (DCs) have a vital role in initiating and directing immune responses and have been frequently used as delivery vehicles in clinical research. The recent clinical data suggest the potential use of DCs pulsed with nucleic acid, especially with RNA holds a great potential as an immunotherapeutic measure with compare to other cancer therapeutics. This review mainly deals with the DCs and their role in transfection with RNA in cancer immunotherapy.

Fingolimod Suppresses the Proinflammatory Status of Interferon-γ-Activated Cultured Rat Astrocytes.

Astroglia, the primary homeostatic cells of the central nervous system, play an important role in neuroinflammation. They act as facultative immunocompetent antigen-presenting cells (APCs), expressing major histocompatibility complex (MHC) class II antigens upon activation with interferon (IFN)-γ and possibly other proinflammatory cytokines that are upregulated in disease states, including multiple sclerosis (MS). We characterized the anti-inflammatory effects of fingolimod (FTY720), an established drug for MS, and its phosphorylated metabolite (FTY720-P) in IFN-γ-activated cultured rat astrocytes. The expression of MHC class II compartments, ß2 adrenergic receptor (ADR-ß2), and nuclear factor kappa-light-chain enhancer of activated B cells subunit p65 (NF-κB p65) was quantified in immunofluorescence images acquired by laser scanning confocal microscopy. In addition, MHC class II-enriched endocytotic vesicles were labeled by fluorescent dextran and their mobility analyzed in astrocytes subjected to different treatments. FTY720 and FTY720-P treatment significantly reduced the number of IFN-γ-induced MHC class II compartments and substantially increased ADR-ß2 expression, which is otherwise small or absent in astrocytes in MS. These effects could be partially attributed to the observed decrease in NF-κB p65 expression, because the NF-κB signaling cascade is activated in inflammatory processes. We also found attenuated trafficking and secretion from dextran-labeled endo-/lysosomes that may hinder efficient delivery of MHC class II molecules to the plasma membrane. Our data suggest that FTY720 and FTY720-P at submicromolar concentrations mediate anti-inflammatory effects on astrocytes by suppressing their action as APCs, which may further downregulate the inflammatory process in the brain, constituting the therapeutic effect of fingolimod in MS.

Metabolic Targets for Improvement of Allogeneic Hematopoietic Stem Cell Transplantation and Graft-vs.-Host Disease.

Utilization of the adaptive immune system against malignancies, both by immune-based therapies to activate T cells in vivo to attack cancer and by T-cell therapies to transfer effector cytolytic T lymphocytes (CTL) to the cancer patient, represent major novel therapeutic advancements in oncologic therapy. Allogeneic hematopoietic stem cell (HSC) transplantation (HSCT) is a form of cell-based therapy, which replaces the HSC in the patient's bone marrow but also serves as a T-cell therapy due to the Graft-vs.-leukemia (GVL) effect mediated by donor T cells transferred with the graft. Allogeneic HSCT provides one potentially curative option to patients with relapsed or refractory leukemia but Graft-vs.-Host-Disease (GVHD) is the main cause of non-relapse mortality and limits the therapeutic benefit of allogeneic HSCT. Metabolism is a common cellular feature and has a key role in the differentiation and function of T cells during the immune response. Naïve T cells and memory T cells that mediate GVHD and GVL, respectively, utilize distinct metabolic programs to obtain their immunological and functional specification. Thus, metabolic targets that mediate immunosuppression might differentially affect the functional program of GVHD-mediating or GVL-mediating T cells. Components of the innate immune system that are indispensable for the activation of alloreactive T cells are also subjected to metabolism-dependent regulation. Metabolic alterations have also been implicated in the resistance to chemotherapy and survival of malignant cells such as leukemia and lymphoma, which are targeted by GVL-mediating T cells. Development of novel approaches to inhibit the activation of GVHD-specific naïve T cell but maintain the function of GVL-specific memory T cells will have a major impact on the therapeutic benefit of HSCT. Here, we will highlight the importance of metabolism on the function of GVHD-inducing and GVL-inducing alloreactive T cells as well as on antigen presenting cells (APC), which are required for presentation of host antigens. We will also analyze the metabolic alterations involved in the leukemogenesis which could differentiate leukemia initiating cells from normal HSC, providing potential therapeutic opportunities. Finally, we will discuss the immuno-metabolic effects of key drugs that might be repurposed for metabolic management of GVHD without compromising GVL.

Genetic variations of TLRs and their association with HPV/EBV, co-infection along with nicotine exposure in the development of premalignant/malignant lesions of the oral cavity in Indian population.

BACKGROUND: Despite being most preventable malignancies associated with smoked and smokeless tobacco products, squamous cell carcinoma of oral cavity is one of the most common malignancy in India. The aim of the present study was to evaluate the role of TLRs in oral pre-cancerous, cancerous cases and their genotypic correlation with HPV/EBV, co-infection & lifestyle habits in Indian population. METHODS: The present study was conducted on 300 subjects (100 OSCC, 50 pre-cancer & 150 controls). The amplification of TLRs gene and HPV/EBV co-infection was assessed by Nested PCR, PCR-RFLP and further confirmation by direct sequencing. RESULTS: The TLR 9(-1486 T/C), revealed that the TT vs. CT + CC genotype had a ˜5-fold increased risk for the development of pre-cancerous lesions as compared to controls (p = 0.0001). Further analysis showed that the risk of cancer was extremely pronounced in HPV/EBV, co-infection (p = 0.0141), implicating the possible interaction between TLR 9(-1486T/C) genotype and HPV infection in increasing cancer/pre-cancer risk. The 'G' allele of TLR 4(+896A/G) was also a higher risk of developing pre-cancerous lesions with 4.5 fold and statistically significant (p = 0.0001). The genotypic association of TLR 9(-1486T/C) in OSMF cases showed ˜8 fold increased risk and TLR 4(+896A/G) showed fourteen fold higher risk for leukoplakia (p < 0.0001, OR = 14.000). CONCLUSION: Genetic polymorphism of TLR 9(-1486 T/C) and TLR 4(+896A/G) may influence the effects of HPV/EBV, co-infection and play the significant role in development of the disease. The significance of these TLRs seemed to be enhanced by tobacco chewing and smoking habits also, which act as an important etiological risk factor for OSCC.

Functions of the WNT Signaling Network in Shaping Host Responses to Infection.

It is well-established that aberrant WNT expression and signaling is associated with developmental defects, malignant transformation and carcinogenesis. More recently, WNT ligands have emerged as integral components of host responses to infection but their functions in the context of immune responses are incompletely understood. Roles in the modulation of inflammatory cytokine production, host cell intrinsic innate defense mechanisms, as well as the bridging of innate and adaptive immunity have been described. To what degree WNT responses are defined by the nature of the invading pathogen or are specific for subsets of host cells is currently not well-understood. Here we provide an overview of WNT responses during infection with phylogenetically diverse pathogens and highlight functions of WNT ligands in the host defense against infection. Detailed understanding of how the WNT network orchestrates immune cell functions will not only improve our understanding of the fundamental principles underlying complex immune response, but also help identify therapeutic opportunities or potential risks associated with the pharmacological targeting of the WNT network, as currently pursued for novel therapeutics in cancer and bone disorders.

Yersinia pestis Interacts With SIGNR1 (CD209b) for Promoting Host Dissemination and Infection.

Yersinia pestis, a Gram-negative bacterium and the etiologic agent of plague, has evolved from Yersinia pseudotuberculosis, a cause of a mild enteric disease. However, the molecular and biological mechanisms of how Y. pseudotuberculosis evolved to such a remarkably virulent pathogen, Y. pestis, are not clear. The ability to initiate a rapid bacterial dissemination is a characteristic hallmark of Y. pestis infection. A distinguishing characteristic between the two Yersinia species is that Y. pseudotuberculosis strains possess an O-antigen of lipopolysaccharide (LPS) while Y. pestis has lost the O-antigen during evolution and therefore exposes its core LPS. In this study, we showed that Y. pestis utilizes its core LPS to interact with SIGNR1 (CD209b), a C-type lectin receptor on antigen presenting cells (APCs), leading to bacterial dissemination to lymph nodes, spleen and liver, and the initiation of a systemic infection. We therefore propose that the loss of O-antigen represents a critical step in the evolution of Y. pseudotuberculosis into Y. pestis in terms of hijacking APCs, promoting bacterial dissemination and causing the plague.

Extrinsic Phagocyte-Dependent STING Signaling Dictates the Immunogenicity of Dying Cells.

The ability of dying cells to activate antigen-presenting cells (APCs) is carefully controlled to avoid unwarranted inflammatory responses. Here, we show that engulfed cells containing cytosolic double-stranded DNA species (viral or synthetic) or cyclic di-nucleotides (CDNs) are able to stimulate APCs via extrinsic STING (stimulator of interferon genes) signaling, to promote antigen cross-presentation. In the absence of STING agonists, dying cells were ineffectual in the stimulation of APCs in trans. Cytosolic STING activators, including CDNs, constitute cellular danger-associated molecular patterns (DAMPs) only generated by viral infection or following DNA damage events that rendered tumor cells highly immunogenic. Our data shed insight into the molecular mechanisms that drive appropriate anti-tumor adaptive immune responses, while averting harmful autoinflammatory disease, and provide a therapeutic strategy for cancer treatment.