Browsing by Subject "cGAMP"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Open Access Dual-adjuvant effect of pH-sensitive liposomes loaded with STING and TLR9 agonists regress tumor development by enhancing Th1 immune response(Elsevier, 2020) Bayyurt-Kocabaş, Banu; Almacıoğlu, Kübra; Alpdundar-Bulut, E.; Güçlüler, Gözde; Tincer, Gizem; Bayık, D.; Gürsel, M.; Gürsel, İhsanNucleic acid-based pattern recognition receptor agonists are effective adjuvants and immunotherapeutic agents. Rather than single applications, ligand combinations could synergistically potentiate immune responses by elevating cytokine and chemokine production via triggering multiple signaling pathways. However, short half-lives of such labile ligands due to nuclease attack and limited cellular uptake due to their structure significantly hamper their in vivo performances. More importantly, simultaneous delivery and activity presentation of protein antigen and nucleic acid ligands critically limit the clinical development of these constructs. In this work, we approached this problem by co-encapsulating a model antigen ovalbumin along with TLR9 and STING ligands within liposomes, a well-established drug delivery system that enables payload stability and enhanced cellular activity upon internalization. Moreover, by loading dual ligands we postulated to achieve heightened Th-1 immune response that would yield pronounced protective vaccine efficacy. We show that, pH-sensitive liposomes co-encapsulating CpG ODN and cGAMP induced synergistic innate immune response by elevating type I and type II interferon levels. Most importantly, this vaccine formulation led to ~70% regression of established melanoma tumor. pH-sensitive liposomal vaccine administration elevated IgG2c/IgG1 antibody ratio, indicative of augmented OVA-specific Th1-biased immunity. Importantly, while the frequency of tumor-specific IFN-γ producing CD8+ T-cells was significantly increased, the M2-type anti-inflammatory macrophage levels were decreased in the tumor bed. In conclusion, our strategy induces reversal of immunosuppressive tumor microenvironment, while enhancing effective anti-tumor immune-response. We propose that this could be coupled with standard therapies during combating tumor eradication.Item Open Access In vivo applications of liposomal vaccines encapsulating single or dual pathogenassociated molecular patterns(Bilkent University, 2017-03) Bayyurt Kocabaş, BanuNucleic 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.Item Open Access Investigation of the role of cGAMP in differentiation of T lymphocytes(Bilkent University, 2016-10) Yıldız, BegümSTING 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.Item Open Access 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.