BACKGROUND:Durvalumab plus perioperative fluorouracil, leucovorin, oxaliplatin, and docetaxel (FLOT) previously improved event-free survival and pathological complete response in resectable gastric and gastro-oesophageal junction adenocarcinoma. We aimed to examine its effect on overall survival. METHODS:MATTERHORN is a global, randomised, double-blind, placebo-controlled, multicentre, phase 3 trial that took place in 147 medical centres in 20 countries (representing Asia, Europe, North America, and South America). Adults with histologically documented resectable gastric or gastro-oesophageal junction adenocarcinoma (eligible for radical surgery; stage II-IVa) not previously treated with anticancer therapy were eligible. Participants were randomly assigned (1:1) to perioperative durvalumab plus FLOT or placebo plus FLOT. Blocked randomisation (unique randomisation number via an interactive response technology system and randomisation and trial supply management system) was stratified by geographical region, clinical lymph node status, and PD-L1 expression. Participants were centrally assigned using the interactive response technology system and randomisation and trial supply management system. Participants received durvalumab 1500 mg or placebo intravenously every 4 weeks on day 1 of each cycle plus FLOT intravenously every 2 weeks on days 1 and 15 of each cycle for four cycles (two neoadjuvant and two adjuvant), followed by durvalumab 1500 mg or placebo intravenously every 4 weeks on day 1 of each cycle for ten additional cycles. Participants, investigators, and those assessing outcomes were masked. The previously reported primary outcome was event-free survival; overall survival in the intention-to-treat population was a key secondary endpoint and is the main endpoint reported here. Safety data were collected throughout treatment and the follow-up period (up to and including 90 days after the last dose of the trial drug) and were analysed in participants who received at least one dose of trial treatment; these data were reported previously and are summarised here. MATTERHORN is closed to recruitment but is ongoing and registered with ClinicalTrials.gov (NCT04592913). FINDINGS:From Nov 17, 2020, to Sept 2, 2022, 1258 participants were enrolled and 948 were randomly assigned; 474 were randomly assigned to durvalumab and 474 to placebo. In a total of 948 participants, the median age was 62 years (IQR 54-68), 682 (72%) were male, and 266 (28%) were female. Overall survival significantly improved in the durvalumab versus placebo group (hazard ratio 0·78, 95% CI 0·63-0·96; p=0·021; significance threshold p<0·0499). Adverse events with the outcome of death possibly related to any trial treatment occurred in 6 (1%) of 475 participants in the durvalumab group and 2 (<1%) of 469 participants in the placebo group. INTERPRETATION:Perioperative durvalumab plus FLOT improved overall survival versus placebo plus FLOT and is a new standard treatment option for patients with resectable gastric or gastro-oesophageal junction adenocarcinoma. FUNDING:AstraZeneca.

Advanced or metastatic esophageal squamous cell carcinoma (ESCC) is associated with poor prognosis; new first‐line systemic treatment options are needed. Combining immuno‐oncology therapies with standard chemotherapy may represent a promising approach for the treatment of solid tumors. Results from a Phase Ib study evaluating durvalumab with tremelimumab and chemotherapy in patients with advanced or metastatic ESCC are reported.

Background: There are no immunological biomarkers that predict control of chronic hepatitis B (CHB). The lack of immune biomarkers raises concerns for therapies targeting PD-1/PD-L1 because they have the potential for immune-related adverse events. Defining specific immune functions associated with control of HBV replication could identify patients likely to respond to anti-PD-1/PD-L1 therapies and achieve a durable functional cure. Methods: We enrolled immunotolerant, HBeAg+ immune-active (IA+), HBeAg− immune-active (IA−), inactive carriers, and functionally cured patients to test ex vivo PD-1 blockade on HBV-specific T cell functionality. Peripheral blood mononuclear cells were stimulated with overlapping peptides covering HBV proteins +/−α-PD-1 blockade. Functional T cells were measured using a 2-color FluoroSpot assay for interferon-γ and IL-2. Ex vivo functional restoration was compared to the interferon response capacity assay, which predicts overall survival in cancer patients receiving checkpoint inhibitors. Results: Ex vivo interferon-γ+ responses did not differ across clinical phases. IL-2+ responses were significantly higher in patients with better viral control and preferentially restored with PD-1 blockade. Inactive carrier patients displayed the greatest increase in IL-2 production, which was dominated by CD4 T cell and response to the HBcAg. The interferon response capacity assay significantly correlated with the degree of HBV-specific T cell restoration. Conclusions: IL-2 production was associated with better HBV control and superior to interferon-γ as a marker of T cell restoration following ex vivo PD-1 blockade. Our study suggests that responsiveness to ex vivo PD-1 blockade, or the interferon response capacity assay, may support stratification for α-PD-1 therapies.

TPS4151 Background: Gastric and gastroesophageal junction cancers (GC, GEJC) are the fifth most common cancer types and the third leading cause of cancer-related deaths globally (Globocan 2020). Standard of care for resectable GC/GEJC includes neoadjuvant-adjuvant FLOT chemotherapy (5-fluorouracil + leucovorin + oxaliplatin + docetaxel) combined with surgery and lymph node dissection for some regions of the world. While treatment advances have improved survival, the 5-year recurrence rate remains high and 5-year overall survival (OS) is poor for patients with resectable disease. Evidence suggests cytotoxic chemotherapy can promote antitumor immunity, thus the combination of immune checkpoint inhibitors, such as durvalumab (an anti–PD-L1 antibody), with cytotoxic chemotherapy may result in increased efficacy (Yu et al. Cancer Lett. 2019; Li et al. Mol Cancer. 2021). MATTERHORN (NCT04592913) is a phase 3, multicenter study evaluating the efficacy and safety of neoadjuvant-adjuvant durvalumab or placebo with FLOT followed by adjuvant durvalumab or placebo in patients with resectable GC/GEJC. Methods: Approximately 900 adult patients will be randomized 1:1 to Arm A or Arm B for 2 neoadjuvant and 2 adjuvant cycles (single cycle defined as durvalumab or placebo every 4 weeks [Q4W] + FLOT [Q2W × 2]); followed by durvalumab or placebo Q4W for 10 cycles. Eligible patients must have histologically confirmed, resectable, stage II or higher GC or GEJC not treated with anticancer therapy, ECOG performance status 0 or 1, and adequate organ function. Complete surgical resection of the primary tumor must be achievable. A tumor tissue sample will be taken at screening or <3 months prior to enrollment. Key exclusion criteria are any prior immune-mediated therapy, peritoneal dissemination or distant metastasis, (adeno)squamous cell carcinoma, or gastrointestinal stromal tumor. The primary endpoint is event-free survival (EFS) assessed by blinded independent central radiology review (BICR) and/or local pathology testing. Secondary endpoints include OS and pathological complete response rate (pCR). Safety and tolerability will be evaluated by adverse events, vital signs, laboratory parameters, and electrocardiogram. Enrollment is ongoing. Funding: AstraZeneca. Clinical trial information: NCT04592913.

TPS373 Background: Esophageal cancer is the eighth most common cancer type and the sixth leading cause of cancer-related death worldwide, and esophageal squamous cell carcinoma (ESCC) is the most common type of esophageal cancer. For patients with locally advanced, unresectable ESCC (AJCC 8th Stage II–IVA), definitive chemoradiotherapy (dCRT) is the current standard of care; however, up to half of patients will experience disease progression within two years of dCRT, and overall survival rates remain suboptimal. The combination of immune checkpoint inhibitors with CRT has demonstrated synergistic antitumor activity in pre-clinical models, and recent clinical data has demonstrated clinical benefit of combined programmed cell death-1 inhibition and preoperative CRT in patients with locally advanced ESCC. KUNLUN (NCT04550260) is a Phase 3, multicenter, global study evaluating the efficacy and safety of durvalumab, a programmed cell death ligand-1 (PD-L1) inhibitor, given concurrently with, and after, dCRT in patients with locally advanced, unresectable ESCC. Methods: Approximately 600 patients will be randomized 2:1 to receive either durvalumab with dCRT (cisplatin plus fluorouracil or cisplatin plus capecitabine, with a total dose of 50–64 Gy radiation), followed by durvalumab for up to approximately 24 months, or placebo with dCRT, followed by placebo for up to approximately 24 months. Eligible patients will have histologically or cytologically confirmed ESCC, and present with locally advanced, unresectable ESCC that is deemed suitable for dCRT. Patients must have an Eastern Cooperative Oncology Group performance status of 0 or 1, and have not received prior anti-cancer treatment. The co-primary endpoint of the study is progression-free survival according to RECIST v1.1 as assessed by blinded independent central review in all randomized patients and in patients with PD-L1-high tumors. Additional endpoints include overall survival and safety. Study enrollment is ongoing. Funding: This study was sponsored by AstraZeneca. References: Hong MH, et al. J Clin Oncol 2019;37(15 suppl). Abs 4027. Clinical trial information: NCT04550260.

Standard-of-care for resectable gastric/gastroesophageal junction cancer includes surgery and neoadjuvant-adjuvant 5-fluorouracil-leucovorin-oxaliplatin-docetaxel (FLOT) chemotherapy. Early-phase clinical studies support further clinical development of the immune checkpoint inhibitor (ICI); durvalumab, an anti-PD-L1 antibody, in patients with gastric/gastroesophageal junction cancer. Accumulating evidence indicates that ICIs combined with FLOT chemotherapy improve clinical outcomes in patients with advanced or metastatic cancer. We describe the rationale for and the design of MATTERHORN, a randomized, double-blind, placebo-controlled, phase III study investigating the efficacy and safety of neoadjuvant-adjuvant durvalumab and FLOT chemotherapy followed by adjuvant durvalumab monotherapy in patients with resectable gastric/gastroesophageal junction cancer. The planned sample size is 900 patients, the primary end point is event-free survival and safety and tolerability will be evaluated. Clinical trial registration: NCT04592913 ( ClinicalTrials.gov )

BackgroundA functional cure for chronic HBV could be achieved by boosting HBV-specific immunity. In vitro studies show that immunotherapy could be an effective strategy. However, these studies include strategies to enrich HBV-specific CD8 T cells, which could alter the expression of the anti-PD-1/anti-PD-L1 antibody targets. Our aim was to determine the efficacy of PD-L1 blockade ex vivo.MethodsHBV-specific CD8 T cells were characterized ex vivo by flow cytometry for the simultaneous analysis of six immune populations and 14 activating and inhibitory receptors. Ex vivo functionality was quantified by ELISpot and by combining peptide pool stimulation, dextramers and intracellular flow cytometry staining.ResultsThe functionality of HBV-specific CD8 T cells is associated with a higher frequency of cells with low exhaustion phenotype (LAG3-TIM3-PD-1+), independently of the clinical parameters. The accumulation of HBV-specific CD8 T cells with a functionally exhausted phenotype (LAG3+TIM3+PD-1+) is associated with lack of ex vivo functionality. PD-L1 blockade enhanced the HBV-specific CD8 T cell response only in patients with lower exhaustion levels, while response to PD-L1 blockade was abrogated in patients with higher frequencies of exhausted HBV-specific CD8 T cells.ConclusionHigher levels of functionally exhausted HBV-specific CD8 T cells are associated with a lack of response that cannot be restored by blocking the PD-1:PD-L1 axis. This suggests that the clinical effectiveness of blocking the PD-1:PD-L1 axis as a monotherapy may be restricted. Combination strategies, potentially including the combination of anti-LAG-3 with other anti-iR antibodies, will likely be required to elicit a functional cure for patients with high levels of functionally exhausted HBV-specific CD8 T cells.

Flow cytometry data presented in tabular form. (XLSX 48 kb)

Despite considerable efforts at developing therapeutic vaccines for cancer, clinical translation of preclinical successes has been challenging, largely due to the difficulty of inducing strong and sustained cytotoxic T lymphocyte (CTL) responses in patients. Several peptide-based cancer vaccines have failed to show sustainable tumor regression in the clinic, possibly because of a lack of optimization of both the adjuvant and antigen components of the preparations. Here, we aimed to develop and optimize a vaccine format utilizing a synthetic long peptide (SLP) containing the human papilloma virus 16 (HPV16) E7 antigen, with a centrally located defined MHC class I epitope, and evaluate its immunogenicity and efficacy in combination with various adjuvant formulations. E731–73 SLP was tested alone or in combination with toll-like receptor (TLR)3, TLR4, TLR7/8 and TLR9 agonists and formulated in oil-in-water (o/w) or water-in-oil (w/o) emulsions to determine a vaccine format inducing a robust CD8 T cell response in murine models. Once a lead vaccine format was determined, we examined its ability to inhibit tumor growth in the murine TC-1 model that expresses HPV16 E7 antigen. We identified the TLR9 agonist CpG formulated in a squalene-based o/w emulsion as the most potent adjuvant, inducing the expansion of multifunctional antigen specific CD8 T cells with cytolytic potential. We also demonstrated that SLP E731–73 + CpG + o/w emulsion vaccine can provide prophylactic and more importantly, therapeutic benefit in the TC-1 murine tumor model. Our results demonstrate that the novel vaccine format E7 SLP + CpG delivered in an o/w emulsion holds potential for the promotion of strong CTL responses and tumor eradication and encourages further development of peptide/adjuvant vaccines in cancer immunotherapy strategies.

Background & Aims: Current therapies for chronic hepatitis B virus (HBV) infection control viral replication but do not eliminate the risk of progression to hepatocellular carcinoma. HBV-specific CD8 T cells are necessary for viral control, but they are rare and exhausted during chronic infection. Preclinical studies have shown that blockade of the PD-1:PD-L1 axis can restore HBV-specific T cell functionality. The aim of this study was to analyze how the clinical and treatment status of patients impacts the ability of HBV-specific T cells to respond to PD-L1 blockade. Methods: Expression patterns of the PD-1:PD-L1/PD-L2 axis were analyzed in healthy donors and chronically infected patients in different clinical phases of disease. A functional assay was performed to quantify baseline HBV-specific T cell responses in chronically infected patients. Baseline responses were then compared to those attained in the presence of an anti-PD-L1 monoclonal antibody (MEDI2790). Results: Chronically infected patients were characterized by the upregulation of PD-1 within the T cell compartment and a concomitant upregulation of PD-L1 on myeloid dendritic cells. The upregulation was maximal in HBV e antigen (HBeAg)-positive patients but persisted after HBeAg negativization and was not restored by long-term treatment. HBV reactivity, measured as frequency of HBV-specific T cells, was significantly higher in HBeAg-negative patients with lower HBV DNA levels, independently of HBV surface antigen or alanine aminotransferase levels. Anti-PD-L1 blockade with MEDI2790 increased both the number of IFN-gamma-producing T cells and the amount of IFN-gamma produced per cell in 97% of patients with detectable HBV reactivity, independently of patients' clinical or treatment status. Conclusion: Patients with lower levels of HBV DNA and the absence of HBeAg have more intact HBV-specific T cell immunity and may benefit the most from PD-L1 blockade as a monotherapy. (C) 2019 The Author(s). Published by Elsevier B.V. on behalf of European Association for the Study of the Liver (EASL).

Background The expansion of antigen-specific CD8 T cells is important in generating an effective and long-lasting immune response to tumors and viruses. Glucocorticoid-induced tumor necrosis factor receptor family-related receptor (GITR) is a co-stimulatory receptor that binds the GITR ligand (GITRL). Agonism of GITR can produce important signals that drive expansion of effector T cell populations. Methods We explored two separate murine tumor models, CT26 and TC-1, for responsiveness to GITR Ligand Fusion Protein(GITRL-FP) monotherapy. In TC-1, GITRL-FP was also combined with concurrent administration of an E7-SLP vaccine. We evaluated tumor growth inhibition by tumor volume measurements as well as changes in CD8 T cell populations and function including cytokine production using flow cytometry. Additionally, we interrogated how these therapies resulted in tumor antigen-specific responses using MHC-I dextramer staining and antigen-specific restimulations. Results In this study, we demonstrate that a GITR ligand fusion protein (GITRL-FP) is an effective modulator of antigen-specific CD8 T cells. In a CT26 mouse tumor model, GITRL-FP promoted expansion of antigen-specific T cells, depletion of regulatory T cells (Tregs), and generation of long-lasting CD8 T cell memory. This memory expansion was dependent on the dose of GITRL-FP and resulted in complete tumor clearance and protection from tumor rechallenge. In contrast, in TC-1 tumor–bearing mice, GITRL-FP monotherapy could not prime an antigen-specific CD8 T cell response and was unable to deplete Tregs. However, when combined with a vaccine targeting E7, treatment with GITRL-FP resulted in an augmentation of the vaccine-induced antigen-specific CD8 T cells, the depletion of Tregs, and a potent antitumor immune response. In both model systems, GITR levels on antigen-specific CD8 T cells were higher than on all other CD8 T cells, and GITRL-FP interacted directly with primed antigen-specific CD8 T cells. Conclusions When taken together, our results demonstrate that the delivery of GITRL-FP as a therapeutic can promote anti-tumor responses in the presence of tumor-specific CD8 T cells. These findings support further study into combination partners for GITRL-FP that may augment CD8 T-cell priming as well as provide hypotheses that can be tested in human clinical trials exploring GITR agonists including GITRL-FP.

Background/objectives: There is currently no licensed prophylactic or therapeutic vaccine for HSV-2 infection.Methods: We developed a novel preclinical vaccine candidate, G103, consisting of three recombinantly expressed HSV-2 proteins (gD and the UL19 and UL25 gene products) adjuvanted with the potent synthetic TLR4 agonist glucopyranosyl lipid A (GLA) formulated in stable emulsion. The vaccine was tested for immunogenicity and efficacy in pre-clinical models for preventative and therapeutic vaccination.Results: Vaccination of mice with G103 elicited antigen-specific binding and neutralizing antibody responses, as well as robust CD4 and CD8 effector and memory T cells. The T cell responses were further boosted by subsequent challenge with live virus. Prophylactic immunization completely protected against lethal intravaginal HSV-2 infection in mice, with only transient replication of virus in the genital mucosa and sterilizing immunity in dorsal root ganglia. Supporting the use of G103 therapeutically, the vaccine expanded both CD4 and CD8 T cells induced in mice by previous infection with HSV-2. In the guinea pig model of recurrent HSV-2 infection, therapeutic immunization with G103 was approximately 50% effective in reducing the number of lesions per animal as well as the overall lesions score.Conclusions: Taken together, the data show that G103 is a viable candidate for development of a novel prophylactic and therapeutic HSV-2 vaccine. (C) 2015 Elsevier Ltd. All rights reserved.

Dendritic cells (DCs) are essential antigen-presenting cells for the initiation of cytotoxic T-cell responses and therefore attractive targets for cancer immunotherapy. We have developed an integration-deficient lentiviral vector termed ID-VP02 that is designed to deliver antigen-encoding nucleic acids selectively to human DCs in vivo. ID-VP02 utilizes a genetically and glycobiologically engineered Sindbis virus glycoprotein to target human DCs through the C-type lectin DC-SIGN (CD209) and also binds to the homologue murine receptor SIGNR1. Specificity of ID-VP02 for antigen-presenting cells in the mouse was confirmed through biodistribution studies showing that following subcutaneous administration, transgene expression was only detectable at the injection site and the draining lymph node. A single immunization with ID-VP02 induced a high level of antigen-specific, polyfunctional effector and memory CD8 T-cell responses that fully protected against vaccinia virus challenge. Upon homologous readministration, ID-VP02 induced a level of high-quality secondary effector and memory cells characterized by stable polyfunctionality and expression of IL-7Rα. Importantly, a single injection of ID-VP02 also induced robust cytotoxic responses against an endogenous rejection antigen of CT26 colon carcinoma cells and conferred both prophylactic and therapeutic antitumor efficacy. ID-VP02 is the first lentiviral vector which combines integration deficiency with DC targeting and is currently being investigated in a phase I trial in cancer patients.

It is a current regulatory requirement to demonstrate absence of detectable replication-competent lentivirus (RCL) in lentiviral vector products prior to use in clinical trials. Immune Design previously described an HIV-1-based integration-deficient lentiviral vector for use in cancer immunotherapy (VP02). VP02 is enveloped with E1001, a modified Sindbis virus glycoprotein which targets dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) expressed on dendritic cells in vivo. Vector enveloped with E1001 does not transduce T-cell lines used in standard HIV-1-based RCL assays, making current RCL testing formats unsuitable for testing VP02. We therefore developed a novel assay to test for RCL in clinical lots of VP02. This assay, which utilizes a murine leukemia positive control virus and a 293F cell line expressing the E1001 receptor DC-SIGN, meets a series of evaluation criteria defined in collaboration with US regulatory authorities and demonstrates the ability of the assay format to amplify and detect a hypothetical RCL derived from VP02 vector components. This assay was qualified and used to test six independent GMP production lots of VP02, in which no RCL was detected. We propose that the evaluation criteria used to rationally design this novel method should be considered when developing an RCL assay for any lentiviral vector.

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

Dendritic cells (DCs) are essential for the initiation of T cell responses and are therefore an attractive target for cancer immunotherapy. The DC vaccine, Provenge®, as well as a number of on-going clinical trials, have in principle validated this concept. However, the currently pursued strategy of ex vivo immunization of DCs is time-consuming and costly. We have developed a 3rd generation, integration-deficient lentivector platform, DCVex(TM), which is designed to deliver tumor antigen-encoding genes directly to DCs in vivo by targeting the DC-SIGN receptor. Mice immunized with DCVex(TM) vectors expressing a variety of model antigens developed strong, dose-dependent poly-functional and cytotoxic antigen-specific CD8 T cell responses, as assessed by intracellular cytokine staining and in vitro cytotoxic T lymphocyte assays. Repeated immunizations resulted in boosting of the T cell responses, indicating the absence of induction of inhibitory anti-vector immunity. Importantly, in stringent therapeutic tumor models (e.g., B16F10 footpad melanoma and CT26 lung metastasis models), immunization with tumor antigen-encoding vectors protected the majority of animals from death in a dose-dependent manner. These findings demonstrate the potential of DCVex(TM) as a novel cancer vaccine platform suitable for in vivo DC immunization. Citation Format: Tina C. Albershardt, Semih U. Tareen, Jared M. Odegard, David J. Campbell, Patrick Flynn, Scott H. Robbins, Peter Berglund, Jan H. ter Meulen. DCVex(TM): A novel DC-targeted vector platform for cancer immunotherapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2817. doi:10.1158/1538-7445.AM2014-2817

Abstract With the goal of creating antigen-directed immunotherapeutics that can be safely administered directly to patients, Immune Design has developed a platform of novel integration-deficient lentiviral vectors that target and deliver antigen-encoding nucleic acids to dendritic cells (DCs) in order to promote the activation of antigen-specific effector CD8 T cells. This platform, termed DCVex(TM), utilizes a novel genetic variant of a Sindbis virus envelope glycoprotein with post-translational carbohydrate modifications in combination with Vpx, a SIVmac viral accessory protein, to achieve efficient targeting and transduction of DCs. In addition, DCVex(TM) incorporates safety features in its design that include redundant mechanisms to render DCVex(TM) integration-deficient, as well as genetic modifications that eliminate psi-gag recombination between split genome components. The characteristics that allow DCVex(TM) to specifically transduce human DCs and the advances that DCVex(TM) brings to conventional third-generation lentiviral vector design demonstrate its potential as a vaccine designed to utilize DCs for cancer immunotherapy. Citation Format: Semih U. Tareen, Brenna Kelley-Clarke, Christopher J. Nicolai, Megan M. Slough, Chintan D. Vin, Neal Van Hoeven, Scott H. Robbins, Jan H. ter Meulen, Peter Berglund. DCVex(TM): A novel integration-deficient lentivector technology that incorporates genetic and post-translational elements to target dendritic cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 702. doi:10.1158/1538-7445.AM2014-702

Type I interferons (IFNs) are central to antiviral defense, but how they orchestrate immune cell function is incompletely understood. We determined that IFNs produced during murine cytomegalovirus (MCMV) infection differentially affect dendritic cells (DCs) and natural killer (NK) cells. IFNs induce cell-intrinsic responses in DCs, activating antiproliferative, antiviral, and lymphocyte-activating gene networks, consistent with high activity of the transcription factor STAT1 in these cells. By comparison, NK cells exhibit lower STAT1 expression and reduced IFN responsiveness. Rather, IFNs indirectly affect NK cells by inducing IL-15, which activates the transcription factor E2F and stimulates genes promoting cell expansion. IFN cell-intrinsic responses are necessary in DCs, but not NK cells, for MCMV resistance. Thus, sensitivity to IFN-induced cytokines and differences in IFN receptor signaling program immune cells to mount distinct responses that promote viral control.