Browsing by Subject "STING"

Now showing 1 - 4 of 4

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In vivo applications of liposomal vaccines encapsulating single or dual pathogenassociated molecular patterns
(2017-03) Bayyurt Kocabaş, Banu
Nucleic acid-based pattern recognition receptor (PRR) agonists are promising adjuvants and immunotherapeutic agents. Combination of PRR ligands potentiates immune response by providing synergistic immune activity via triggering different signaling pathways and may impact antigen dependent T-cell immune memory. However, the duration of short circulation due to nuclease attacks is hampering their clinical performance. Liposomes enable protein and nucleic acid based compounds to have high encapsulation efficiency. Herein, we aimed to develop liposomal carrier systems that co-encapsulating single TLR9 or combinations with TLR3 or STING ligands and assess their potential as adjuvants and immunostimulatory agents in in vivo applications. Liposomal dual nucleic acid formulations induced synergistic innate immune activation, enhanced cytokine production along with internalization capacity of ligands. In anti-cancer vaccine study, CpG ODN and poly(I:C) coencapsulation significantly increased OVA-specific Th1-biased immune even after eight months post-booster injection. Challenge with OVA-expressing tumor cell line, E.G7, demonstrated that mice immunized with liposomes co-encapsulating CpG ODN and poly(I:C) had significantly slower tumor progression dependent on OVAspecific cytotoxic memory T-cells. In our second in vivo application, liposomal CDN and TLR9 therapy led to 80% remission of established melanoma tumor. Increased IgG2c/IgG1 ratio in mice treated with liposomal formulations indicating the development of antigen specific Th1-biased immunity was observed. Furthermore, along with the treatment, IFN-dual ligands into liposomes enhanced the anti-tumor activity of single ligands. In the third part, immunization with CpG ODN loaded liposomal formulations together with antigens increased antigen-specific humoral response against FMDV and Helicobacter. In addition, the liposomal CpG ODN reduced bacterial gastric colonization by antigen-dependent Th1 and Th17 immune responses after helicobacter challenging.
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Investigation of the role of cGAMP in differentiation of T lymphocytes
(2016-10) Yıldız, Begüm
STING is the pivotal mediator for the recognition of host and pathogenic cytosolic dsDNA as well as cyclic di-nucleotides metabolites from microbes. STING can either recognize DNA itself or sense the presence of cGAMP, which is converted from ATP and GTP upon DNA binding to cGAS enzyme. Not only strategy against intracellular pathogens makes STING an ideal target, but also the recognition of DNA from host cells has a significant role in tumor immunity. Previous studies demonstrated that DNA released from cancerous cells are internalized by innate immune cells such as macrophages and dendritic cells in tumor microenvironment and trigger the production of IFN-β and other pro-inflammatory cytokines including IL-6, TNF-α, and IL-12 through STING triggered signaling pathway. These cytokines then enhance cytotoxic activity of CD8+ T cells by further increasing IFNγ production. Since enhanced T cell immunity is the hallmark of vaccine adjuvants, cyclic di-nucleotides such as cGAMP become an important and effective vaccine adjuvants against intracellular pathogens and malignant cells. Although STING activating cyclic di-nucleotides are envisioned as novel and potent vaccine adjuvants, more thorough research is needed to unearth the mechanism of action of STING on different immune cells. Therefore, it will pave the way for the initiation of successful human trials. The important criteria while developing vaccine adjuvant are the magnitude, and the quality of an immune response and its toxic side effects. To identify these, members of the both innate and adaptive immune system should be taken into account. However, previous studies merely focus on the function and effect of cGAMP in innate immune cells such as macrophages, monocytes and dendritic cells. However, to date there is no explicit study investigating the effect of STING signaling cascade on T-cells. In the light of these findings, we aimed to investigate the direct effect and function of cGAMP on T lymphocytes. Since there were not any preliminary data, we firstly stimulated Pan T cells with cGAMP alone or together with various TLR ligands and then, checked the cytokine profiles and the viability of cells. Surprisingly, 2.5µg/ml dose of cGAMP had a toxic effect on T cell but not on bone marrow derived dendritic cells and macrophages. While cGAMP triggered cell death, interestingly IL-17 secretion from both CD4+ and CD8+ T cells was dramatically increased. Beside, cGAMP stimulation drastically increased CD4+ /CD8+ T cells ratio of Pan T cells population. Next, we sought to identify the source of IL-17. The IL17 inductive capacity of cGAMP was investigated on purified CD4+ T cells from mice. Unexpectedly, data revealed that cGAMP elicited apoptosis of CD4+ T cells. Moreover, there was no significant induction of IL-17 secretion. Next, we aimed to find a condition that will reduce the toxic effect of cGAMP, while maintaining IL-17 secretion. When Pan T cells were stimulated with cGAMP and R848 (a TLR7 ligand), the toxic action of cGAMP decreased while IL-17 secretion was enhanced. Lastly, the potency of T cells stimulated with cGAMP was investigated. According to our results, macrophages were activated in the presence of conditioned medium obtained from T cells stimulated with cGAMP. When taken together our findings point out that STING dependent direct activation of T-cells via cGAMP and its subsequent effect on macrophages might be utilized as an immunotherapeutic approach where IL17 induction is important and could be harnessed as vaccine adjuvants against mucosal infections or against cancer.
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Involvement of sting-activating cyclic Di-nucleotides on T-cell differentiation and function: an unresolved issue
(Turkish Society of Immunology, 2016) Yıldız, B.; Gürsel, İ.
STING is the pivotal mediator for the recognition of host and pathogenic cytosolic dsDNA as well as cyclic di-nucleotide metabolites from microbes. Studies demonstrated that DNA released from cancerous cells are internalized by innate immune cells such as macrophages and dendritic cells in tumor microenvironment and trigger the production of interferon beta and other pro-inflammatory cytokines including interleukin 6, tumor necrosis factor alpha, and interleukin 12 through STING triggered signaling pathway. Later, these cytokines increase the cytotoxic activity of CD8+ T-cells by increasing the production of interferon gamma. This review discusses the importance of the involvement of STING during the establishment of immunity against intracellular pathogens and its direct effect on T-cells. © 2016 Turkish Journal of Immunology. All rights reserved.
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Leishmania kinetoplast DNA contributes to parasite burden in infected macrophages: Critical role of the cGAS-STING-TBK1 signaling pathway in macrophage parasitemia
(Frontiers Media S.A., 2022-11-02) Yilmaz, Ismail Cem; Dunuroglu, Emre; Ayanoglu, Ihsan Cihan; Ipekoglu, Emre Mert; Yıldırım, Muzaffer; Girginkardesler, Nogay; Ozbel, Yusuf; Toz, Seray; Ozbilgin, Ahmet; Aykut, Gamze; Gursel, Ihsan
Leishmania parasites harbor a unique network of circular DNA known as kinetoplast DNA (kDNA). The role of kDNA in leishmania infections is poorly understood. Herein, we show that kDNA delivery to the cytosol of Leishmania major infected THP-1 macrophages provoked increased parasite loads when compared to untreated cells, hinting at the involvement of cytosolic DNA sensors in facilitating parasite evasion from the immune system. Parasite proliferation was significantly hindered in cGAS- STING- and TBK-1 knockout THP-1 macrophages when compared to wild type cells. Nanostring nCounter gene expression analysis on L. major infected wild type versus knockout cells revealed that some of the most upregulated genes including, Granulysin (GNLY), Chitotriosidase-1 (CHIT1), Sialomucin core protein 24 (CD164), SLAM Family Member 7 (SLAMF7), insulin-like growth factor receptor 2 (IGF2R) and apolipoprotein E (APOE) were identical in infected cGAS and TBK1 knockout cells, implying their involvement in parasite control. Amlexanox treatment (a TBK1 inhibitor) of L. major infected wild type cells inhibited both the percentage and the parasite load of infected THP-1 cells and delayed footpad swelling in parasite infected mice. Collectively, these results suggest that leishmania parasites might hijack the cGAS-STING-TBK1 signaling pathway to their own advantage and the TBK1 inhibitor amlexanox could be of interest as a candidate drug in treatment of cutaneous leishmaniasis. Copyright © 2022 Yilmaz, Dunuroglu, Ayanoglu, Ipekoglu, Yildirim, Girginkardesler, Ozbel, Toz, Ozbilgin, Aykut, Gursel and Gursel.