Expression Of Co-stimulatory Signals Research Articles

Simultaneous delivery of DNA vaccine and hydrophobic adjuvant using reducible polyethylenimine-functionalized graphene oxide for activation of dendritic cells

The activation and maturation of dendritic cells are critical in immunotherapy, and the potency of DCs is associated with high levels of antigen presentation on major histocompatibility complex (MHC) class I and II and the expression of costimulatory signals. Graphene oxide (GO) and its derivatives have many excellent physicochemical properties, including large and hydrophobic surface available for interacting with hydrophobic or aromatic drugs via π–π stacking forces, flexibility of the chemical modification on the surfaces, and capacity of DC activation. In this study, we designed a simple strategy to achieve the co-delivery of a DNA vaccine and hydrophobic immune adjuvant (R848) and to enhance the adjuvanticity of R848 via the synergistic effect of GO and R848. Thiolated low-molecular-weight polyethylenimine (TPEI1.8) was crosslinked with 4-aminothiophenol-modified GO (TGO) via the formation of disulfide bonds. Thus, TGO with its assembled TPEI1.8 could not only load R848 but also electrostatically interact with the DNA vaccine. Owing to the reducibility of the disulfide bond in the cellular environment, the DNA vaccine could be readily released. This system can significantly enhance the DNA transfection, the expression of the costimulatory signal, and the level of antigen presentation to MHC class I DCs for their activation and maturation.

Abstract B21: Combination of adenovirus and adoptive T-cell therapy breaks tumor tolerance by recruiting immune cells to and promoting their activity in the tumor

Abstract Background: Despite the fast growing rate in the development of novel adoptive T-cell therapies, the clinical benefit in established solid tumors has remained modest. Roadblocks to effective immune attack by infiltrating tumor-specific T-cells include several immune evasion mechanisms, which contribute to tumor tolerance. Oncolytic virotherapy on the other hand is the use of cancer cell specific, conditionally replicative viruses in the treatment of cancer. Oncolytic virotherapy has been suggested to enhance epitope spreading by direct oncolysis of tumor cells, leading to enhanced antigen presentation by dendritic cells and increased immunogenicity of the established tumor by providing virus mediated danger signal in the form of pathogen-associated molecular patterns, which are efficiently recognized by the immune system. Here, we studied the combination of these two established forms of immunotherapy in a highly resistant and poorly immunogenic B16.OVA mouse melanoma model. Methods: Immunocompetent B16.OVA bearing C57BL/6 female mice were adoptively transferred with CD8a+ enriched, OVA-specific OT-I lymphocytes and treated with intratumoral injections 5/3-fiber chimeric adenovirus (diluted in saline) on six consecutive days. Tumor growth of mice was monitored every 2-3 days by using electronic calipers. Mice were sacrificed on day 14 post-transfer and immune composition of harvested tumors was analyzed by flow cytometry. Results: Following adoptive transfer of OT-I lymphocytes, superior tumor growth control was observed in adenovirus-treated mice compared to control mice, even in the absence of active oncolysis. Significant increase in infiltration of CD45+ leukocytes, CD8+ lymphocytes and F4/80+ macrophages was seen adenovirus-treated tumors suggesting enhanced tumor immunogenicity. Pro-inflammatory tumor microenvironment mediated by adenovirus infection led to expression of co-stimulatory signals on CD11c+ antigen presenting cells and subsequent activation of T-cells, thus breaking the tumor-induced peripheral tolerance of T-cells. Moreover, epitope spreading in the form of endogenous anti-melanoma T-cells was detected in the combination treated mice indicating that the dual approach can lead to systemic anti-tumor immunity. Conclusions: Treatment with adenovirus can overcome resistance of B16.OVA murine melanoma tumors to T-cell therapy by recruitment and stimulation of tumor-infiltrating immune cells, thus improving the efficacy of adoptive T-cell therapy in solid tumors. Citation Format: Siri Tähtinen, Susanna Grönberg-Vähä-Koskela, Dave Lumen, Mikko Siurala, Anu J. Airaksinen, Markus Vähä-Koskela, Akseli Hemminki. Combination of adenovirus and adoptive T-cell therapy breaks tumor tolerance by recruiting immune cells to and promoting their activity in the tumor. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B21.

Requirement of CD80 + costimulation for rejection of ocular tumors and termination of immune privilege

Immune privilege in the anterior chamber of the eye is very effective at preventing elimination of ocular tumors that express weak tumor antigens. We previously demonstrated that DBA/2 mice immunized in the flank with a P815 tumor cell vaccine that expressed CD80/IL-12 was unable to terminate immune privilege and prevent tumor growth in the anterior chamber. In the present study, we determined whether expression of costimulatory signals on tumor cells injected via an ocular route would terminate immune privilege. We observed that CD80-positive tumors were always rejected from the anterior chamber. However, the pattern of tumor rejection was dramatically different depending upon whether the mice were either naïve, or immunized in flank against the tumor cells. Naïve mice that received an anterior chamber injection of CD80-positive tumors did not develop immune privilege and displayed strong delayed hypersensitivity (DH) against the tumor cells. Moreover, the ocular tumors were rejected by ischemic necrosis that induced atrophy of the eye and phthisis. When immunized mice received an identical injection of tumor cells in the anterior chamber, they also did not develop immune privilege and displayed strong DH. However, tumor rejection was considerably different and occurred without destruction of normal ocular tissue, or phthisis. To determine if immune privilege was restored in these eyes, mice received a second injection of P815 cells (CD80-negative) into the anterior chamber 2 weeks after the first CD80-positive tumors were eliminated. Surprisingly, immune privilege was not restored and the P815 tumors were eliminated completely, again without phthisis. We conclude that specific rejection of ocular tumors with minimal destruction of the eye requires systemic immunization and expression of CD80 costimulatory signals on tumors within the eye.

Lipopolysaccharide causes atrophy of Peyer's patches and an increased expression of CD28 and B7 costimulatory ligands.

Intestinal mucosal dysfunction appears to contribute to infectious complications in critically ill patients. The current study was undertaken to investigate whether endotoxin affects lymphocyte subpopulations and the expression of costimulatory signals in Peyer's patches (PP). Female Balb/c mice were given an intraperitoneal injection of 25 microg LPS and sacrified 24 h or 72 h later to determine total cell yield, lymphocyte subpopulations (B-cells, total T-cells, CD4+- and CD8+-cells), the costimulatory molecules CD28, B7.1 (CD80) and B7.2 (CD86) and the percentage of apoptotic cells in PP and in the spleen as well as small intestinal IgA concentration. Lipopolysaccharide (LPS) challenge caused a significant decrease of total cell yield in PP at both time-points (-50+/-28% and -43+/-25%, respectively; P < 0.001). This decrease was significant for all measured lymphocyte subpopulations. In contrast, total cell yield was increased (P < 0.001) in the spleen 24 h (+52+/-13%) and 72 h (+130+/-22%) after LPS. The decrease of lymphocyte numbers in the PP was accompanied by an increased percentage of lymphocytes expressing costimulatory molecules. In this respect, an increased percentage of CD40+CD80+, CD40+CD86+, and of CD4+CD28+ could be demonstrated after LPS administration. In the spleen, the percentage of CD4+CD28+ was also elevated after LPS bolus, however, the percentage of CD40+CD80+ was reduced, and that of CD40+CD86+ was unaltered. The influence of LPS on apoptosis of lymphocytes was time-dependent. The percentage of apoptotic cells 24 h after LPS was increased in PP (P < 0.01), but was unchanged in the spleen. Seventy-two hours after LPS injection, the percentage of apoptotic cells returned to normal in PP. Luminal IgA levels remained unchanged after LPS challenge. In conclusion, our data show that LPS causes atrophy of PP which seems to be counterregulated by an enhanced expression of costimulatory molecules.