Induction Of Antigen-specific CD8 Research Articles

Impaired B Cell Recall Memory and Reduced Antibody Avidity but Robust T Cell Response in CVID Patients After COVID-19 Vaccination

PurposeHumoral and cellular immune responses were described after COVID-19 vaccination in patients with common variable immunodeficiency disorder (CVID). This study aimed to investigate SARS-CoV-2-specific antibody quality and memory function of B cell immunity as well as T cell responses after COVID-19 vaccination in seroresponding and non-responding CVID patients.MethodsWe evaluated antibody avidity and applied a memory B cell ELSPOT assay for functional B cell recall memory response to SARS-CoV-2 after COVID-19 vaccination in CVID seroresponders. We comparatively analyzed SARS-CoV-2 spike reactive polyfunctional T cell response and reactive peripheral follicular T helper cells (pTFH) by flow cytometry in seroresponding and non-seroresponding CVID patients. All CVID patients had previously failed to mount a humoral response to pneumococcal conjugate vaccine.ResultsSARS-CoV-2 spike antibody avidity of seroresponding CVID patients was significantly lower than in healthy controls. Only 30% of seroresponding CVID patients showed a minimal memory B cell recall response in ELISPOT assay. One hundred percent of CVID seroresponders and 83% of non-seroresponders had a detectable polyfunctional T cell response. Induction of antigen-specific CD4+CD154+CD137+CXCR5+ pTFH cells by the COVID-19 vaccine was higher in CVID seroresponder than in non-seroresponder. Levels of pTFH did not correlate with antibody response or avidity.ConclusionReduced avidity and significantly impaired recall memory formation after COVID-19 vaccination in seroresponding CVID patients stress the importance of a more differentiated analysis of humoral immune response in CVID patients. Our observations challenge the clinical implications that follow the binary categorization into seroresponder and non-seroresponder.

CAF08 adjuvant enables single dose protection against respiratory syncytial virus infection in murine newborns

Respiratory syncytial virus is a leading cause of morbidity and mortality in children, due in part to their distinct immune system, characterized by impaired induction of Th 1 immunity. Here we show application of cationic adjuvant formulation CAF08, a liposomal vaccine formulation tailored to induce Th 1 immunity in early life via synergistic engagement of Toll-like Receptor 7/8 and the C-type lectin receptor Mincle. We apply quantitative phosphoproteomics to human dendritic cells and reveal a role for Protein Kinase C-δ for enhanced Th1 cytokine production in neonatal dendritic cells and identify signaling events resulting in antigen cross-presentation. In a murine in vivo model a single immunization at birth with CAF08-adjuvanted RSV pre-fusion antigen protects newborn mice from RSV infection by induction of antigen-specific CD8+ T-cells and Th1 cells. Overall, we describe a pediatric adjuvant formulation and characterize its mechanism of action providing a promising avenue for development of early life vaccines against RSV and other respiratory viral pathogens.

The generation of stem cell-like memory cells early after BNT162b2 vaccination is associated with durability of memory CD8+ Tcell responses.

COVID-19 vaccines elicit humoral and cellular immune responses. Durable maintenance of vaccine-induced immunity is required for long-term protection of the host. Here, we examine activation and differentiation of vaccine-induced CD8+ T cells using MHC class I (MHC-I) multimers and correlations between early differentiation and the durability of CD8+ T cell responses among healthcare workers immunized with two doses of BNT162b2. The frequency of MHC-I multimer+ cells is robustly increased by BNT162b2 but decreases 6 months post-second vaccination to 2.4%–65.6% (23.0% on average) of the peak. MHC-I multimer+ cells dominantly exhibit phenotypes of activated effector cells 1–2 weeks post-second vaccination and gradually acquire phenotypes of long-term memory cells, including stem cell-like memory T (TSCM) cells. Importantly, the frequency of TSCM cells 1–2 weeks post-second vaccination significantly correlates with the 6-month durability of CD8+ T cells, indicating that early generation of TSCM cells determines the longevity of vaccine-induced memory CD8+ T cell responses.

A single immunization with CAF08 provides newborns with Th1-mediated protection against Respiratory Syncytial Virus infection

Abstract Respiratory Syncytial Virus (RSV) is a leading cause of morbidity and mortality in children, due in part to their distinct immune system, characterized by impaired induction of T-helper 1 (Th1)□immunity. Here we describe cationic adjuvant formulation (CAF)-08, a liposomal vaccine formulation tailored to induce Th1 immunity in early life via synergistic engagement of Toll-like Receptor 7/8 and the C-type lectin receptor Mincle. Quantitative phosphoproteomics applied to human dendritic cells revealed a key role for Protein Kinase C-d for enhanced Th1 cytokine production in neonatal dendritic cells and identified signaling events resulting in antigen cross-presentation. In vivo, a single immunization at birth with CAF08-adjuvanted RSV pre-fusion antigen protected newborn mice from RSV infection through induction of antigen-specific CD8+ and Th1 cells. Overall, we describe a novel pediatric adjuvant formulation and characterize its mechanism of action providing a promising avenue for development of early life vaccines against RSV and other intracellular pathogens.

CD8+ T Cells Directed Against a Peptide Epitope Derived From Peptidoglycan-Associated Lipoprotein of Legionella pneumophila Confer Disease Protection

Legionella pneumophila, an intracellular bacterium, may cause life-threatening pneumonia in immunocompromised individuals. Mononuclear cells and antibodies have been reported to be associated with the host defense response against L. pneumophila. This study is to determine whether Legionella peptidoglycan-associated lipoprotein (PAL)-specific CD8+ T cells are directly associated with protection against L. pneumophila, with a focus on potential epitopes. Synthetic peptides derived from PAL of L. pneumophila were obtained and tested through in vitro and in vivo cytotoxic T lymphocyte (CTL) assays for immunogenicity. PAL DNA vaccines or a peptide epitope with or without CpG-oligodeoxynucleotides (ODN) was evaluated for protection against L. pneumophila infection in animal models. When mice were immunized with DNA vaccines expressing the PAL of L. pneumophila, they were significantly protected against a lethal challenge with L. pneumophila through induction of antigen-specific CD8+ CTLs. Of the 13 PAL peptides tested, PAL92-100 (EYLKTHPGA) was the most immunogenic and induced the strongest CTL responses. When mice were immunized with the PAL92-100 peptide plus CpG-ODN, they were protected against the lethal challenge, while control mice died within 3–6 days after the challenge. Consistent with lung tissue histological data, bacterial counts in the lungs of immunized mice were significantly lower than those in control mice. Also, the amino acid sequence of PAL92-100 peptides is conserved among various Legionella species. To our knowledge, this study is the first to demonstrate that PAL92-100-specific CD8+ T cells play a central role in the host defense response against L. pneumophila.

Induction of antigen specific CD8+ T cell infiltration by a novel neoadjuvant vaccine containing HSP70 and GPC3 peptides plus soluble LAG-3 and Poly-IC:LC: Interim results of a Phase I study.

e14306 Background: Even with curative resection, the recurrence rate of HCC is still high, and no effective adjuvant therapy is currently available. Our previous Phase I study with novel therapeutic peptides and immune adjuvants demonstrated the safety, antigen specific CTL induction in PBMC and a sign of efficacy (ASCO 2017 Abstract # 3086); thus, we started Phase I study of the same therapy as a perioperative immunotherapy setting in patients with resectable HCC (UMIN000029991). Methods: Two mg each of HLA-A*24:02, 02:01, or 02:06 restricted HSP70- and GPC3-derived peptides, in combination with hLAG-3Ig (1.0 mg) + Poly-IC:LC (1.4 mg) were injected intradermally at four sites of the inguinal and axillary regions every week for 6 weeks before surgery. Patients subsequently received 10 injections of adjuvant immunotherapy over 4 months. Surgical specimens and PBMCs were analyzed by mass cytometry (CyTOF), using 66 antibodies to monitor T cell exhaustion, T cell activation, Effector Treg induction, etc. Tumor specimens were also subjected to immunohistochemical staining of CD3, CD8, PD1, HSP70, and GPC3. The reason for early reporting is the interesting findings at the foci of HCC, and the interim analyses was approved by the Data and Safety Monitoring Committee. Results: Of the 11 screened patients, 5 completed the treatments and were analyzed. We found massive CD8+ T lymphocyte infiltration in the intratumor foci of HCC, which is usually accompanied by peritumoral lymphocytic infiltration. Moreover, the density of lymphocytes was markedly higher in areas of HSP70 or GPC3 antigen expression. One case out of five recurred 5 month after surgery and it showed low CD8+ and PD1+ cell infiltration and high effector Treg (CD4+/CD25+/CD45RA-/FoxP3 +) infiltration. This trend was not observed in PBMC, suggesting the importance of TIL analysis. The high PD1 expression was accompanied by massive intratumoral infiltration of CD8+ lymphocytes. Conclusions: The novel therapeutic peptide and immune adjuvant combination induced sustained immune cell infiltration into tumor microenvironments, especially those presenting target tumor-associated antigens. Our novel immunotherapy may convert cold tumors into hot tumors containing PD1+ lymphocytes. Thus, the combination of this novel strategy with PD (L) 1 antibody is warranted. Clinical trial information: 000029991.

The STING ligand cGAMP potentiates the efficacy of vaccine-induced CD8+ T cells.

Pathogen recognition receptor (PRR) agonists are currently being developed and tested as adjuvants in various formulations to optimize the immunogenicity and efficacy of vaccines. Using an original in vitro approach to prime naive precursors from unfractionated human peripheral blood mononuclear cells, we assessed the influence of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), a ligand for the stimulator of interferon genes (STING), on the induction of antigen-specific CD8+ T cells. We found that 2'3'-cGAMP and 3'3'-cGAMP were especially potent adjuvants in this system, driving the expansion and maturation of functionally replete antigen-specific CD8+ T cells via the induction of type I IFNs. The biological relevance of these findings was confirmed in vivo using two mouse models, in which 2'3'-cGAMP-adjuvanted vaccination elicited protective antitumor or antiviral CD8+ T cell responses. These results identify particular isoforms of cGAMP as effective adjuvants that may find utility in the development of novel immunotherapies and vaccines.

Highlights of This Issue

Sipuleucel-T is an FDA-approved autologous cellular immunotherapy with established efficacy in metastatic castration-resistant prostate cancer (mCRPC); elucidation of its mechanism of action continues to evolve. Peripheral cellular and humoral immune responses to PAP and the immunogen PA2024 demonstrated long-lived, antigen-specific immune responses to sipuleucel-T that correlate with overall survival (OS). The current study shows persistent antigen-specific peripheral CD4+ T-cell responses and the induction of antigen specific CD8+ T cells with potential lytic function following sipuleucel-T. Moreover, a positive correlation between OS and PAP- as well as PA2024-specific cytotoxic T lymphocytes (CTLs) phenotype was found. Sipuleucel-T–induced antigen-specific CTL activity could provide a biologic basis for the OS benefit observed in mCRPC.Radiotherapy is an integral component in the adjuvant treatment of breast cancer, but reliable biomarkers predictive of radiotherapy benefit have been lacking. In this work, Cui and colleagues developed gene expression signatures reflecting two distinct biological processes: intrinsic radiosensitivity and antitumor immunity. Both radiosensitivity and immunological signatures were shown to be predictive of radiotherapy benefit, and integration of the two further improved patient stratification. The integrated gene signatures may be used to select patients who are most likely to benefit from radiotherapy, or to identify patients who may not respond well to standard radiotherapy and will need alternative therapies.LncRNAs are promising diagnostic markers, prognostic factors and therapeutic targets in tumorigenesis. Bian and colleagues revealed that LncRNA—FEZF1-AS1 is frequently upregulated in colorectal cancer (CRC) and was associated with poor prognosis. The in vitro and in vivo functional assays demonstrated that FEZF1-AS1 promotes CRC cell growth and metastasis. Mechanistically, FEZF1-AS1 could bind and increase the stability of PKM2 protein, resulting in the activating of STAT3 signaling and the increasing of aerobic glycolysis. Targeting FEZF1-AS1/PKM2 signaling appears to be a promising treatment for CRC.The glycosaminoglycan hyaluronan (HA) accumulates in the tumor microenvironment (TME) of many solid tumors, with HA accumulation linked to aggressive malignancy. To further elucidate the biological and physical changes associated with tumor HA accumulation, Li and colleagues used two different methods to modulate HA in mouse tumor models. Experiments compared xenografts from parental cells with cells engineered to overexpress hyaluronan synthase. Additionally, a PEGylated hyaluronidase (PEGPH20) was used to enzymatically degrade HA. Higher tumor HA was accompanied by increased collagen, reduced perfusion, increased hypoxia, and increased α-SMA. PEGPH20 treatment reversed these changes and depleted tumor-associated VEGF-A165. Data support continued investigation of strategies to target HA in the TME.

Abstract IA22: Reprogramming the tumor microenvironment and T cells for ovarian cancer immunotherapy

Abstract Immunologic destruction of tumors is a multistep, coordinated process that can be modulated or targeted at several critical points to elicit tumor rejection. These steps in the cancer immunity cycle include: (i) generation of sufficient numbers of effector T cells with high avidity recognition of tumor antigens in vivo; (ii) trafficking and infiltration into the tumor; (iii) overcoming inhibitory networks in the tumor microenvironment; (iv) direct recognition of tumor antigens and generation of an effector antitumor response; and (v) persistence of the antitumor T cells. Although several immune-based interventions have gained regulatory approval in many solid tumors and hematologic malignancies, there are currently no approved immune therapies for ovarian cancer. A major barrier to successful deployment of cancer immunotherapy for ovarian cancer patients is the immunosuppressive tumor microenvironment. Even if large numbers of tumor-specific T cells are generated in patients by active immunization or adoptive transfer, these T cells may not persist to readily destroy tumor targets in vivo. Previous studies by our group have defined some of the dominant immune resistance mechanisms in ovarian cancer to include extrinsic suppression of CD8+ effector cells by regulatory T cells (Tregs) (1, 2); metabolic deregulation via tryptophan catabolism by the immunoregulatory enzyme indoleamine-2,3-dioxygenase (IDO) (3, 4); engagement of inhibitory receptors such as PD-1 by the ligand PD-L1/B7-H1 (5-7); development of antigen loss variants (8); myeloid-derived suppressor cells (9); and inhibitory cytokines such as TGF-β. Collectively, this redundant immunosuppressive network facilitates tumor progression by actively restraining antitumor immunity and must be overcome in order to implement efficacious immunotherapeutic strategies. This presentation will be focused on our efforts at: (i) overcoming IDO-mediated innate and adaptive immune resistance as a strategy to reprogram the ovarian tumor microenvironment and (ii) novel “next-generation” strategies for reprograming T cells for adoptive immunotherapy of ovarian cancer.

Interleukin-5 Mediates Parasite-Induced Protection against Experimental Autoimmune Encephalomyelitis: Association with Induction of Antigen-Specific CD4+CD25+ T Regulatory Cells.

To examine if the protective effect of parasite infection on experimental autoimmune encephalomyelitis (EAE) was due to interleukin (IL)-5, a cytokine produced by a type-2 response that induces eosinophilia. We hypothesize that, in parasite infections, IL-5 also promotes expansion of antigen-specific T regulatory cells that control autoimmunity. Nippostrongylus brasiliensis larvae were used to infect Lewis rats prior to induction of EAE by myelin basic protein. Animals were sham treated, or given blocking monoclonal antibodies to interleukin 4 or 5 or to deplete CD25+ T cells. Reactivity of CD4+CD25+ T regulatory cells from these animals was examined. Parasite-infected hosts had reduced severity and length of EAE. The beneficial effect of parasitic infection was abolished with an anti-IL-5 or an anti-CD25 monoclonal antibody (mAb), but not anti-IL-4 mAb. Parasite-infected animals with EAE developed antigen-specific CD4+CD25+ T regulatory cells earlier than EAE controls and these expressed more Il5ra than controls. Treatment with IL-5 also reduced the severity of EAE and induced Il5ra expressing CD4+CD25+ T regulatory cells. The results of this study suggested that IL-5 produced by the type-2 inflammatory response to parasite infection promoted induction of autoantigen-specific CD25+Il5ra+ T regulatory cells that reduced the severity of autoimmunity. Such a mechanism may explain the protective effect of parasite infection in patients with multiple sclerosis where eosinophilia is induced by IL-5, produced by the immune response to parasites.

Cancer peptide vaccine to suppress postoperative recurrence in esophageal SCC patients with induction of antigen-specific CD8+ T cell.

e14635 Background: This is a following report of the exploratory phase II study of adjuvant peptide vaccine for thoracic esophageal squamous cell carcinoma (TESCC) (abstract #3087 in ASCO2016), focusing on an association of immunological responses with clinical outcomes. Three HLA-A-24-restricted epitope peptides derived from cancer-testis antigens, up-regulated lung cancer 10 (URLC10), cell division cycle associated 1 (CDCA1) and KH domain-containing protein overexpressed in cancer 1 (KOC1), were used in this study. Methods: TESCC patients who underwent neoadjuvant therapy followed by curative resection (Dec./2009 to Sep./2014) and were found LN metastasis were enrolled. One mg each of three peptides mixed with Montanide was injected to patients with HLA-A*2402 20 times in a 6-months period. No other adjuvant therapy was given until recurrence occurred. Primary endpoint is relapse-free survival (RFS). Immunological responses were examined by ELISPOT assay and immunohistochemistry (IHC). Results: 33 patients were enrolled in the vaccine group (VG) and 30 with non-HLA-A*2402 were used as controls (CG). There was no significant difference in clinical backgrounds between the two groups. 5-year RFS in the VG was 44.6% while that in the CG group was 31.6% (p = 0.207); patients who showed CD8+ CTL induction to multiple peptides tend to show better RFS rate [3/2/1 peptides = 69.0(n = 20)/46.8(n = 11)/0%(n = 2), respectively]. Five-year esophageal cancer-specific survival (ECSS) were 58.4% in the VG compared with 35.4% in the CG (p = 0.156); 90.0% (n = 11) vs. 50.0% (n = 15) and 43.8% (n = 22) vs. 24.0%(n = 15) in pN1 and pN2-3 groups, respectively. Regarding the CD8+ positivity, ECSS was improved only in the negative group (56.6% in VG vs. 26.7% in CG). Classification by T cell positivity and PD-L1 expression [type I(+/+), II(-/-), III(-/+) and IV(+/-)] showed 5-year ECSS to be 100%(n = 3), 66.4%(n = 19), 20.0%(n = 5) and 44.4%(n = 6). Conclusions: Our cancer peptide vaccines induced the antigen-specific CD8+ T cell highly and efficiently, and suppressed recurrence with the strong immune responses. Clinical trial information: UMIN000003557.

Immature myeloid-derived suppressor cells: A bridge between inflammation and cancer (Review).

Chronic inflammation is considered to be one of the hallmarks of tumor initiation and progression. Changes occurring in the microenvironment of progressing tumors resemble the process of chronic inflammation, which begins with ischemia followed by interstitial and cellular edema, appearance of immune cells, growth of blood vessels and tissue repair, and development of inflammatory infiltrates. Moreover, long‑term production and accumulation of inflammatory factors lead to local and systemic immunosuppression associated with cancer progression. Of the several mechanisms described to explain this anergy, the accumulation of myeloid cells in the tumor, spleen, and peripheral blood of cancer patients has gained considerable interest. A population of suppressive CD11b+Gr-1+cells has in fact been designated as myeloid-derived suppressor cells (MDSCs). MDSCs are a unique category of the myeloid lineage, and they induce the prevention of the development of cytotoxic T lymphocytes(CTLs) invitro, and the induction of antigen-specific CD8+T-cell tolerance invivo. Therapeutic approaches directed toward the manipulation of the MDSC population and their function may improve chemoimmune-enhancing therapy for advanced malignancies.

Hepatic AAV Gene Transfer of Cytoplasmic Transgene Induces Transgene Product-Specific T Cell Activation Initially in the Liver and Celiac Lymph Node Preceding Treg Induction

In several published studies, we have shown induction of immune tolerance to coagulations factors by hepatic gene transfer to animals with hemophilia. Tolerance induction is influenced by a number of complex factors, most notably T cell activation and induction of antigen-specific CD4+CD25+FoxP3+ regulatory T cells (Treg). We sought to better understand antigen presentation to CD4+ T cells and the dynamics of the resulting T cell response. To characterize the interaction of adeno-associated virus (AAV) antigen expression in the liver with immune cells, we used an AAV8 vector, which have a high tropism for murine liver, expressing cytoplasmic ovalbumin (AAV8-Cyto-Ova) from the EF1α promoter. Use of AAV8-Cyto-Ova allowed us to eliminate effects from systemic antigen delivery. Vector was injected into the tail vein of DO11.10-transgenic RAG-/- mice, which contain exclusively Ova-specific CD4+ T cells and lack Treg. AAV8-Cyto-Ova caused upregulation of the very early activation marker CD69 on the CD4+ T cells as early as 2 weeks after gene transfer, with induced Treg emerging at about 3 weeks. CD69+CD4+ T cells were first observed in greatest numbers in the liver and celiac lymph node (LN), one of the liver-draining LN. This T cell activation persisted for several weeks. To better define the sites of T cell activation, we used the compound FTY720, which is an agonist of sphingosine-1-phosphate receptors and prevents migration of lymphocytes but does not alter T cell function. Two weeks after AAV8-Cyto-Ova, FTY720 sequestered activated T cells mostly in the liver and celiac LN, when compared to other lymphoid organs, indicating that these are the initial sites of T cell activation. At the 3-week time point, there were fewer activated T cells in the liver and celiac LN in mice that received FTY720, while instead accumulating in the blood. Most likely, activated T cells were prevented from reentering the lymphoid organs from the circulation, where they were sequestered. We conclude that T cells are first activated by AAV8-Cyto-Ova in the liver and celiac LN after two weeks, where they subsequently egress into the circulation and re-enter lymphoid tissues, with many returning to the liver and celiac LN. FTY720 given at 2 weeks prevented the newly activated T cells from leaving the liver and celiac LN. These results strongly suggest that antigen presentation and CD4+ T cell activation occur first in the liver and celiac LN, beginning about 2 weeks after vector administration. Consistent with this conclusion, adoptively transferred Ova-specific CD4+ T cells proliferated first and to a much greater degree in the celiac LN of AAV8-Cyto-Ova transduced mice. Inactiviating Kupffer cells with gadolinium chloride significantly reduced antigen-specific proliferation, illustrating the requirement for professional resident liver antigen-presenting cells. Furthermore, we show that - in contrast to the AAV expression of secreted Ova - Treg are exclusively extrathymically induced after AAV8-Cyto-Ova vector administration. These Treg are found in high numbers in the blood after 2 weeks in mice given the FTY720 compound, suggesting that these peripherally induced Treg quickly enter the circulation. In conclusion, the liver and its draining celiac LN are key sites for antigen presentation and T cell activation in response to transgene expression directed by hepatic gene transfer. Presentation of antigen derived from a non-secreted transgene product induces FoxP3+ Treg that rapidly distribute through the circulation. DisclosuresHerzog:Novo Nordisk: Research Funding; Spark Therapeutics: Patents & Royalties: Patent licenses.

Abstract B36: mRNA and dendritic cell based immunotherapy

Abstract Modification of dendritic cells (DC) with mRNA allows the loading of these cells with tumor antigens and the functional modification of the cellular vaccine. To reprogram immature DC towards potent and immunostimulatory antigen presenting cells, we provide three different molecular adjuvants to DCs with mRNA coding for caTLR4, mimicking TLR-activation, CD40L, mimicking the ‘licensing’ of DCs by Th cells, and CD70 to provide an extra stimulus for the priming of CD8+ T cells. The mixture of these three mRNA's (caTLR4, CD40L and CD70) is referred to as ‘TriMix’ The programming of DC with mRNA can be performed either in vitro, by electroporation, or even in vivo after injection of mRNA into lymph nodes or at the tumor site. At our institution, clinical trials in advanced melanoma patients are being performed using ex vivo modified DCs. These patients are treated with TriMixDC-MEL, a mixture of TriMix-DC co-electroporated with mRNA encoding a fusion of DC.LAMP and 1 of 4 melanoma associated antigens (TAA) (gp100, tyrosinase, MAGE-C2 or MAGE-A3). In a first pilot clinical trial, 24.106 TriMixDC-MEL cells were administrated solely by the intradermal (ID) route. Subsequently, a phase IB was conducted to investigate the safety of administrating TriMixDC-MEL by the intravenous (IV) and ID-route. ID administration of TriMixDC-MEL was found to be feasible, safe, effectively stimulating CD8+ T-cell responses, but did not result in objective tumor responses. In contrast, the combined ID/IV administration is associated with distinct but manageable side-effects and has seemingly superior clinical activity as compared to DC administered solely ID in patients with pretreated advanced melanoma. We also investigated the safety and activity of TriMixDC-MEL combined with check-point blockade (ipilimumab). Thirty nine AJCC stage IIIc/IV melanoma pts initiated study treatment). Following DC-administration, gr2 skin injection site reactions were observed in all pts, post-infusion chills (< gr2) in 15 (38%), and transient flu-like symptoms (< gr2) in 33 pts (85%). Most frequent grade 3/4 adverse events of special interest were: dermatitis, diarrhea/colitis, hypophysitis, hepatitis, and pneumonitis. Systemic corticotherapy was used to treat irAE in 18 pts (46%). Best overall tumor response by irRC: 8 CR, and 7 PR (BORR 38%), 6 SD and 18 PD. All CR, and 3 PR are ongoing after a median duration of 19 mths (range 3-29 mths). The 6-mths DCR by irRC is 50% (95% CI 34-66). Median PFS and OS are respectively 6.2 (95% CI 3-9), and 14.4 mths (95%CI 10-18). These encouraging clinical responses indicate that further clinical development of TriMixDC-MEL in combination with immune checkpoint modulators is warranted. Furthermore, more recent pre-clinical studies indicate that this cellular therapy with ex vivo modified DCs could evolve towards a less complex approach via the direct in vivo modification of DCs. We evaluated whether intranodal (IN) and intratumoral (IT) delivery of TriMix mRNA together or not with TAA mRNA, results in the in situ modification and maturation of DCs hence priming of TAA-specific T-cells. Upon IN and IT delivery of mRNA, we could demonstrate the selective uptake and translation of mRNA by lymph node- and tumor-resident CD11c+ cells, respectively. This process was hampered by co-delivery of classical maturation stimuli but not by TriMix mRNA. Importantly, injection of TriMix mRNA induced a T-cell attracting and stimulatory environment. Enhanced induction of antigen-specific CD4+ and CD8+ T-cells was demonstrated using TriMix mRNA and mRNA's several antigens upon IN immunization. Intranodal mRNA immunization was shown to be as efficient in induction of CTLs and in therapy as vaccination with ex vivo mRNA electroporated DCs in several mouse tumor models. Upon IT injection of TriMix mRNA, the tumor-resident DCs become activated, migrate to lymph nodes and activate CD8+ cytotoxic T lymphocyte responses against several cancer-antigens, including a cancer-testis antigen and a neoepitope. Since no TAA encoding mRNA was added, these results indicate that the tumor-resident DCs are loaded with tumor antigens, can be activated in situ and can be tuned into an auto-vaccine. Intratumoral injection of TriMix mRNA only showed curative potential against disseminated tumors. In conclusion, IN and IT administration of TAA mRNA together with mRNA encoding DC modulating molecules is a promising vaccination strategy that could evolve towards an off-the-shelf anti-cancer vaccine. Citation Format: Kris Thielemans. mRNA and dendritic cell based immunotherapy. [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 B36.

Abstract 2505: Therapeutic efficacy of the ZVex™ and GLAAS™ platforms in a B16-F10/hCAIX melanoma mouse model

Abstract ZVex™ and GLAAS™ are two dendritic-cell (DC) targeting platform technologies designed to enhance immune responses through the in vivo induction of antigen specific CD8 and CD4 T-cells, respectively. ZVex™ is a lentiviral vector pseudotyped with a modified Sindbis virus envelope engineered to deliver tumor antigen-encoding nucleic acids to dendritic cells in vivo. GLAAS™(Glucopyranosyl Lipid A Adjuvant System) activates DC by binding to the TLR-4 receptor and inducing strong Th1 type CD4 responses against co-delivered recombinant proteins. Currently both platform technologies are being investigated in phase I clinical trials in cancer patients. Human carbonic anhydrase 9 (hCAIX) is a tumor-associated transmembrane antigen that is over-expressed on various cancer cell types. We mapped hCAIX specific, multi-functional CD8 and CD4 T-cell epitopes within the extracellular and transmembrane regions of the protein for the mouse haplotype H-2b by intracellular cytokine staining. Mice lethally challenged s.c. on the flank with a B16-F10 tumor cell line expressing the hCAIX protein (designated BC.12) fully controlled large tumors (>100 mm2) when therapeutically immunized (subcutaneously at the base of tail) with ZVex™ encoding hCAIX or the recombinant hCAIX protein with GLAAS™ (either s.c. or i.m.). In both models, tumor control was dose-dependent. Additionally, the presence of a strong transmembrane H-2b restricted CD8 T-cell epitope was required for tumor control and regression. hCAIX-specific CD8 T-cell responses were detectable as far out as day 67 post challenge in mice displaying full regression of tumor. These results demonstrate proof of concept for ZVex™ and GLAAS™ platform technologies in an aggressive murine melanoma model. Citation Format: David J. Campbell, Rebecca S. Reeves, Patrick A. Flynn, Scott H. Robbins, Peter Berglund, Jan H. ter Meulen. Therapeutic efficacy of the ZVex™ and GLAAS™ platforms in a B16-F10/hCAIX melanoma mouse model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2505. doi:10.1158/1538-7445.AM2015-2505

Induction of antigen specific CD4+CD25+Foxp3+T regulatory cells from naïve natural thymic derived T regulatory cells

CD4+CD25+FOXP3+T regulatory cells (Treg) play a major role in prevention of induction and control of immune responses, and contribute to induction of immune tolerance. Natural or thymic Treg (tTreg) have non-antigen specific suppressor action. Tolerance to a specific antigen is also mediated by CD4+CD25+FOXP3+Treg, but the source of these cells is disputed. Many suggest that they are derived from effector lineage CD4+CD25−FOXP3−T cells and are induced Treg (iTreg). Our work shows that tTreg with specific TCR for the antigen can be activated to more potent antigen specific Treg. We have demonstrated that initial activation of tTreg with antigen and IL-2 induces antigen specific Treg that express receptors for the late Th1 cytokines IFN-γ and IL-12. These antigen specific Treg suppress effector lineage T cells at much lower ratios than tTreg, and we call these Ts1 cells as they are activated by Th1 cytokines and express receptors for Th1 cytokines. Further activation of Ts1 cells with specific antigen and late Th1 cytokines such as IL-12 induces very potent Th1-like Treg, that express t-bet, the transcription factor for Th1 cells, as well as the Th1 cytokine IFN-γ. Similar Th1-like Treg can be induced in IL-2 activated tTreg, by IFN-γ or IL-27. tTreg activated by antigen in the presence of IL-4 induces antigen specific Treg that express the IL-5 receptor, and these Ts2 cells can be induced to Th2-like Treg by IL-5 and antigen. tTreg can be activated to antigen specific Tregs that induce tolerance and have therapeutic potential.

Protective Antibody and CD8+ T-Cell Responses to the Plasmodium falciparum Circumsporozoite Protein Induced by a Nanoparticle Vaccine

BackgroundThe worldwide burden of malaria remains a major public health problem due, in part, to the lack of an effective vaccine against the Plasmodium falciparum parasite. An effective vaccine will most likely require the induction of antigen specific CD8+ and CD4+ T-cells as well as long-lasting antibody responses all working in concert to eliminate the infection. We report here the effective modification of a self-assembling protein nanoparticle (SAPN) vaccine previously proven effective in control of a P. berghei infection in a rodent model to now present B- and T-cell epitopes of the human malaria parasite P. falciparum in a platform capable of being used in human subjects.Methodology/Principal FindingsTo establish the basis for a SAPN-based vaccine, B- and CD8+ T-cell epitopes from the P. falciparum circumsporozoite protein (PfCSP) and the universal CD4 T-helper epitope PADRE were engineered into a versatile small protein (∼125 amino acids) that self-assembles into a spherical nanoparticle repetitively displaying the selected epitopes. P. falciparum epitope specific immune responses were evaluated in mice using a transgenic P. berghei malaria parasite of mice expressing the human malaria full-length P. falciparum circumsporozoite protein (Tg-Pb/PfCSP). We show that SAPN constructs, delivered in saline, can induce high-titer, long-lasting (1 year) protective antibody and poly-functional (IFNγ+, IL-2+) long-lived central memory CD8+ T-cells. Furthermore, we demonstrated that these Ab or CD8+ T–cells can independently provide sterile protection against a lethal challenge of the transgenic parasites.ConclusionThe SAPN construct induces long-lasting antibody and cellular immune responses to epitope specific sequences of the P. falciparum circumsporozoite protein (PfCSP) and prevents infection in mice by a transgenic P. berghei parasite displaying the full length PfCSP.

666. Type-I IFN Signaling Is Required for the Induction of Antigen-Specific CD8+ T Cell Responses by Adenovirus Vector Vaccine in the Gut-Mucosal Compartment

666. Type-I IFN Signaling Is Required for the Induction of Antigen-Specific CD8+ T Cell Responses by Adenovirus Vector Vaccine in the Gut-Mucosal Compartment

Trypanosoma cruzias an effective cancer antigen delivery vector

One of the main challenges in cancer research is the development of vaccines that induce effective and long-lived protective immunity against tumors. Significant progress has been made in identifying members of the cancer testis antigen family as potential vaccine candidates. However, an ideal form for antigen delivery that induces robust and sustainable antigen-specific T-cell responses, and in particular of CD8(+) T lymphocytes, remains to be developed. Here we report the use of a recombinant nonpathogenic clone of Trypanosoma cruzi as a vaccine vector to induce vigorous and long-term T cell-mediated immunity. The rationale for using the highly attenuated T. cruzi clone was (i) the ability of the parasite to persist in host tissues and therefore to induce a long-term antigen-specific immune response; (ii) the existence of intrinsic parasite agonists for Toll-like receptors and consequent induction of highly polarized T helper cell type 1 responses; and (iii) the parasite replication in the host cell cytoplasm, leading to direct antigen presentation through the endogenous pathway and consequent induction of antigen-specific CD8(+) T cells. Importantly, we found that parasites expressing a cancer testis antigen (NY-ESO-1) were able to elicit human antigen-specific T-cell responses in vitro and solid protection against melanoma in a mouse model. Furthermore, in a therapeutic protocol, the parasites expressing NY-ESO-1 delayed the rate of tumor development in mice. We conclude that the T. cruzi vector is highly efficient in inducing T cell-mediated immunity and protection against cancer cells. More broadly, this strategy could be used to elicit a long-term T cell-mediated immunity and used for prophylaxis or therapy of chronic infectious diseases.

Messenger RNA-based Vaccines With Dual Activity Induce Balanced TLR-7 Dependent Adaptive Immune Responses and Provide Antitumor Activity

Direct vaccination with messenger RNA (mRNA) molecules encoding tumor-associated antigens is a novel and promising approach in cancer immunotherapy. The main advantage of using mRNA for vaccination is that the same molecule not only provides an antigen source for adaptive immunity, but can simultaneously bind to pattern recognition receptors, thus stimulating innate immunity. However, achieving both features remains challenging, as the complexation of mRNA required for immune-stimulating activity may inhibit its translatability. In this study, we present a new and more effective vaccine design: a two-component mRNA-based tumor vaccine that supports both: antigen expression and immune stimulation, mediated by Toll like receptor 7 (TLR7). The two-component mRNA vaccines, containing free and protamine-complexed mRNA, induce balanced adaptive immune responses providing humoral as well as T cell mediated immunity. This balanced immune response is based on the induction of antigen-specific CD4(+) T helper cells and cytotoxic CD8(+) T cells. Once activated, these CD4(+) and CD8(+) T cells secrete a wide set of cytokines, which drive a TH1 response. Immunization with the two-component vaccines induces sustained memory responses, mediated by antigen-specific memory T cells. Moreover, treatment of mice with the two-component mRNA vaccine mediates a strong antitumor response against OVA-expressing tumor cells, not only in a prophylactic but also in a therapeutic setting. In conclusion, two-component mRNA vaccines with self-adjuvanting activity induce balanced adaptive immune responses and mediate sustained antitumor activity.