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Persistence of an immunosuppressive state plays a role in septic patient morbidity and late mortality. Both innate and adaptive pathways are impaired, pointing toward the need for immune interventions targeting both arms of the immune system. We developed a virotherapy using the nonpropagative modified vaccinia virus Ankara (MVA), which harbors the intrinsic capacity to stimulate innate immunity, to deliver IL-7, a potent activator of adaptive immunity. The rMVA–human IL-7 (hIL-7)–Fc encoding the hIL-7 fused to the human IgG2-Fc was engineered and shown to express a dimeric, glycosylated, and biologically active cytokine. Following a single i.v. injection in naive mice, the MVA–hIL-7–Fc increased the number of total and activated B, T, and NK cells but also myeloid subpopulations (Ly6Chigh, Ly6Cint, and Ly6Cneg cells) in both lung and spleen. It triggered differentiation of T cells in central memory, effector memory, and acute effector phenotypes and enhanced polyfunctionality of T cells, notably the number of IFN-γ–producing cells. The MVA vector contributed significantly to immune cell activation, particularly of NK cells. The MVA–hIL-7–Fc conferred a significant survival advantage in the cecal ligation and puncture (CLP) and Candida albicans sepsis models. It significantly increased cell numbers and activation in both spleen and lung of CLP mice. Comparatively, in naive and CLP mice, the rhIL-7–Fc soluble counterpart overall induced less vigorous, shorter lasting, and narrower immune activities than did the MVA–hIL-7–Fc and favored TNF-α–producing cells. The MVA–hIL-7–Fc represents a novel class of immunotherapeutic with clinical potential for treatment of septic patients.

Virus-based therapies show promise in inducing systemic anti-tumor immunity. Over the past years, modified poxviruses were developed to induce a sustained antitumoral immune response. Several studies confirm this hypothesis and report induction of T cell response against the antigen targeted by these vaccines. We previously reported MVA induced T-cell response against HPV oncoviral antigens E6 and E7 in HPV anogenital cancers (NCT03260023) and against private tumor neoantigen in ovarian and head and neck cancer. Despite these promising results the molecular and cellular mechanisms involved in vaccine response remains to be elucidated. In this work, we inquired whether EVs, well known for mediating intercellular communication, play a role in these therapeutic vaccination process. We first asked whether poxviral infection of human primary cells modifies their EV secretion properties. To this end, peripheral blood mononuclear cells (PBMCs) from healthy donors were infected with poxviral vectors, cell culture supernatants were harvested, and different isolation methods were compared for their ability to separate EVs from viral particles: ultracentrifugation, immunocapture, density gradient, velocity gradient, size exclusion chromatography and filtration. EVs size distribution and concentration were determined by nanoparticle tracking analysis (NTA) and the presence of infectious viral particles was titrated by plaque assays. Our data showed that 0.1µm filtration allowed the complete separation of EVs from infectious viral particles. All other methods showed co-isolation of EVs and infectious viral particles. Using this method, we demonstrate that infection of PBMCs with the poxviruses VACV, MVA and PCPV significantly increased the amount of secreted EVs. Next, we investigated the molecular content of EVs isolated from MVA-infected PBMCs by mass spectrometry. We observed differences in the abundance of at least 57 human proteins between EVs from infected and non-infected cells. In addition, several viral proteins, including virus-encoded payloads were detected in EVs from infected cells. We are now confirming those data with flow cytometry to detect virus-encoded payloads like tumor antigens, antigen-presenting molecules, and EV markers such as tetraspanins. The RNA content of EVs from infected and non-infected cells will be compared. Finally, EVs were isolated from murine dendritic cells infected with therapeutic pox vaccines. We are now evaluating the effects of local and systemic application of EVs in murine tumor models. Citation Format: Lucas Walther, Caroline Tosch, Jules Deforges, Christine Carapito, Magali Rompais, Marie-Christine Claudepierre, Nathalie Silvestre, Kaïdre Bendjama, Eric Quemeneur, Jacky Goetz, Vincent Hyenne, Karola Rittner. Extracellular vesicles (EV) - mediators of therapeutic vaccination? In vivo and in vitro characterization of EVs generated after infection of human and murine cells with therapeutic poxviruses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 697.

Background: Single domain antibodies (sdAbs) isolated after immunization of camelids are particularly attractive formats for their high modularity and small size allowing a better diffusion into tumors. However, the short in vivo half-life of sdAbs, related to the lack of a Fc domain, limits their clinical application. By replicating specifically into tumor cells, the oncolytic vaccinia virus (VACV) is an optimal vector to deliver and maintain high intra-tumoral concentrations of therapeutic sdAb. Moreover, sdAb targeting immunological targets, such as PD-L1, may synergize the anti-tumoral activity of VACV. Randox and Transgene report the selection and characterization of a sdAb targeting the human PD-L1 and the design of optimal formats, including bispecific anti-PD-L1-CD40 ligand, for vectorization into VACV. Methods: Alpacas were immunized with human PD-L1 protein and sdAb coding sequences were isolated by PCR. Anti-PD-L1 sdAb binders were selected by phage display and sdAb blockers of PD-L1/PD-1 interaction were identified by ELISA. The ability of the selected sdAb to disrupt the PD-L1/PD-1 interaction was verified on transformed and primary cells. To fine-tune an optimal anti-PD-L1, several sdAb formats were designed and vectorized into VACV. The sdAb format exhibiting the best PD-L1/PD-1 blocking activity was selected by the screening of culture supernatants of several VACV-sdAb infected tumor cells. Finally, anti-PD-L1 sdAb-CD40L fusions were designed to generate a strong CD40 agonist active only in a PD-L1 positive environment. Results: SdAb clone 1A1 exhibited the best PD-L1/PD-1 blocking activity which remained unchanged after extensive humanization (latterly becoming named GS542). GS542 was vectorized in VACV as monomeric single chain homodimer, and fused to Fc domain or antibody hinge domain to foster dimerization together with full length IgG1 avelumab as anti-PD-L1 benchmark. All constructs were expressed by infected tumor cells. The single chain homodimer displayed the best PD-L1/PD-1 blocking activity, superior to that of avelumab. Moreover, GS542-CD40L fusions were designed to take advantage of the natural trimerization of CD40L to increase the avidity for PD-L1 while clustering CD40L at the surface of PD-L1+ cells to trans-activate the CD40 pathway. Evaluation of these GS542-CD40L fusions showed strong CD40 agonist activity depending on the presence of PD-L1+ cells making these constructs safer CD40 agonists. Conclusion: An anti-PD-L1 sdAb with a strong blocking activity was selected, humanized and evaluated under different VACV-vectorized formats. The single chain homodimeric sdAb expressed by VACV was identified as the best PD-L1/PD-1 blocking format. Furthermore, bispecific anti-PD-L1 sdAb-CD40L fusions that exhibited strong CD40 agonist activity was charactered within a PD-L1+ environment. Citation Format: Jean-Baptiste Marchand, Elodie Pintado, Marshall Dunlop, Christelle Remy, Patricia Kleinpeter, Shirley Shön, Fend Laetitia, Renée Brandely, Delphine Suhner, Eline Winter, Nathalie Silvestre, Claire Huguet, Peter Fitzgerald, Eric Quéméneur. Selection of an optimal anti-PD-L1 single domain antibody format for the vectorization into oncolytic vaccinia virus and the generation of bispecific immunomodulators [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1885.

BackgroundImmune checkpoint blockade (ICB) is a clinically proven concept to treat cancer. Still, a majority of patients with cancer including those with poorly immune infiltrated ‘cold’ tumors are resistant to currently available ICB therapies. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is one of few clinically validated targets for ICB, but toxicities linked to efficacy in approved αCTLA-4 regimens have restricted their use and precluded full therapeutic dosing. At a mechanistic level, accumulating preclinical and clinical data indicate dual mechanisms for αCTLA-4; ICB and regulatory T cell (Treg) depletion are both thought to contribute efficacy and toxicity in available, systemic, αCTLA-4 regimens. Accordingly, strategies to deliver highly effective, yet safe αCTLA-4 therapies have been lacking. Here we assess and identify spatially restricted exposure to a novel strongly Treg-depleting, checkpoint-blocking, vectorized αCTLA-4, as a highly efficacious and potentially safe strategy to target CTLA-4.MethodsA novel human IgG1 CTLA-4 antibody (4-E03) was identified using function-first screening for monoclonal antibodies (mAbs) and targets associated with superior Treg-depleting activity. A tumor-selective oncolytic vaccinia vector was then engineered to encode this novel, strongly Treg-depleting, checkpoint-blocking, αCTLA-4 antibody or a matching surrogate antibody, and Granulocyte-macrophage colony-stimulating factor (GM-CSF) (VVGM-αCTLA-4).ResultsThe identified 4-E03 antibody showed significantly stronger Treg depletion, but equipotent checkpoint blockade, compared with clinically validated αCTLA-4 ipilimumab against CTLA-4-expressing Treg cells in a humanized mouse model in vivo. Intratumoral administration of VVGM-αCTLA-4 achieved tumor-restricted CTLA-4 receptor saturation and Treg depletion, which elicited antigen cross-presentation and stronger systemic expansion of tumor-specific CD8+ T cells and antitumor immunity compared with systemic αCTLA-4 antibody therapy. Efficacy correlated with FcγR-mediated intratumoral Treg depletion. Remarkably, in a clinically relevant mouse model resistant to systemic ICB, intratumoral VVGM-αCTLA-4 synergized with αPD-1 to reject cold tumors.ConclusionOur findings demonstrate in vivo proof of concept for spatial restriction of Treg depletion-optimized immune checkpoint blocking, vectorized αCTLA-4 as a highly effective and safe strategy to target CTLA-4. A clinical trial evaluating intratumoral VVGM-αhCTLA-4 (BT-001) alone and in combination with αPD-1 in metastatic or advanced solid tumors has commenced.

Background Immune checkpoint blockade (ICB) is a clinically proven concept to treat cancer. Still, a majority of patients with cancer including those with poorly immune infiltrated ‘cold’ tumors are resistant to currently available ICB therapies. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is one of few clinically validated targets for ICB, but toxicities linked to efficacy in approved αCTLA-4 regimens have restricted their use and precluded full therapeutic dosing. At a mechanistic level, accumulating preclinical and clinical data indicate dual mechanisms for αCTLA-4; ICB and regulatory T cell (Treg) depletion are both thought to contribute efficacy and toxicity in available, systemic, αCTLA-4 regimens. Accordingly, strategies to deliver highly effective, yet safe αCTLA-4 therapies have been lacking. Here we assess and identify spatially restricted exposure to a novel strongly Treg-depleting, checkpoint-blocking, vectorized αCTLA-4, as a highly efficacious and potentially safe strategy to target CTLA-4. Methods A novel human IgG1 CTLA-4 antibody (4-E03) was identified using function-first screening for monoclonal antibodies (mAbs) and targets associated with superior Treg-depleting activity. A tumor-selective oncolytic vaccinia vector was then engineered to encode this novel, strongly Treg-depleting, checkpoint-blocking, αCTLA-4 antibody or a matching surrogate antibody, and Granulocyte-macrophage colony-stimulating factor (GM-CSF) (VVGM-αCTLA-4). Results The identified 4-E03 antibody showed significantly stronger Treg depletion, but equipotent checkpoint blockade, compared with clinically validated αCTLA-4 ipilimumab against CTLA-4-expressing Treg cells in a humanized mouse model in vivo. Intratumoral administration of VVGM-αCTLA-4 achieved tumor-restricted CTLA-4 receptor saturation and Treg depletion, which elicited antigen cross-presentation and stronger systemic expansion of tumor-specific CD8+ T cells and antitumor immunity compared with systemic αCTLA-4 antibody therapy. Efficacy correlated with FcγR-mediated intratumoral Treg depletion. Remarkably, in a clinically relevant mouse model resistant to systemic ICB, intratumoral VVGM-αCTLA-4 synergized with αPD-1 to reject cold tumors. Conclusion Our findings demonstrate in vivo proof of concept for spatial restriction of Treg depletion-optimized immune checkpoint blocking, vectorized αCTLA-4 as a highly effective and safe strategy to target CTLA-4. A clinical trial evaluating intratumoral VVGM-αhCTLA-4 (BT-001) alone and in combination with αPD-1 in metastatic or advanced solid tumors has commenced.

Antitumor viral vaccines, and more particularly poxviral vaccines, represent an active field for clinical development and translational research. To improve the efficacy and treatment outcome, new viral vectors are sought, with emphasis on their abilities to stimulate innate immunity, to display tumor antigens and to induce a specific T-cell response.We screened for a new poxviral backbone with improved innate and adaptive immune stimulation using IFN-α secretion levels in infected PBMC cultures as selection criteria. Assessment of virus effectiveness was madeThe bovine pseudocowpox virus (PCPV) stood out among several poxviruses for its ability to induce significant secretion of IFN-α. PCPV produced efficient activation of human monocytes and dendritic cells, degranulation of NK cells and reversed MDSC-induced T-cell suppression, without being offensive to activated T cells. A PCPV-based vaccine, encoding the HPV16 E7 protein (PCPV-E7), stimulated strong antigen-specific T-cell responses in TC1 tumor-bearing mice. Complete regression of tumors was obtained in a CD8We propose PCPV as a viral vector suitable for vaccination in the field of personalised cancer vaccines, in particular for heterologous prime-boost regimens.

Background: Cancer mutations acquired during carcinogenesis are not subject to central tolerance and thus, are cornerstone in cancer immunosurveillance. The use of mutation-derived neoepitopes to design cancer vaccines is an unprecedented opportunity to target efficient antigens, but the stochastic occurrence of mutations implies that a tailored vaccine needs to be designed and manufactured for each patient. We used next generation sequencing, machine learning based genomic data analysis and advances in genome editing to systematically identify private neoepitopes in high-risk HPV negative HNSCC and relapsing OvC patients. Methods: Mutations were identified by DNA and RNA sequencing and putative epitopes were selected for vaccine design on their likelihood to elicit a class I or II response based on HLA binding, allelic frequency, prediction of processing and expression at RNA level. The vaccine was a recombinant virus of the modified Vaccinia Ankara (MVA) strain encoding for up to 30 sequences of 29 amino acids centred on the predicted epitope and flanked with the normal germline sequence in case of missense mutations, and of the mutated protein sequence in case of frameshift mutations. The viral vaccine was amplified under GMP conditions and administered to patients after curative intent treatment in two phase I trials. Treatment was started for OvC patients at relapse defined as elevation of CA-125 or onset of suspicious radiological findings and, after first line therapy for HNSCC patients with locally advanced disease with either extracapsular extension or positive resection margins following upfront surgery. The vaccine was administered for 6 weeks and a booster dose every three weeks over a year, in absence of other cancer therapy. Results: Six patients (4 OvC and 2 HNSCC) were treated and experienced only mild related adverse events. After 6 doses of vaccine, we measured immunoreactive T cells in PBMCs against each of the targeted epitopes using an ex vivo IFNγ ELISPOT showed robust responses in all evaluable patients. Positive responses to vaccination were observed for a total of 46 epitopes over 115 tested with a median of 11 epitopes (6 to 18) per patient. Responses were directed against both class I and II epitopes and were either de novo responses (64%) or amplification of pre-existing responses (36%). In parallel, phenotyping of patient PBMCs showed, in all treated patients, a decline in naïve CD4 and CD8 cells and the onset of effector CD27- CD4 and CD27-/CD57+ CD8; similarly, CD56dim NK cells increased suggesting a stimulation of antitumor innate immunity. In one ovarian cancer patient, these immune changes correlated with a normalization of CA-125 that lasted 7 months. Conclusions: These data show that the personalized approach with TG4050 is feasible, safe and immunogenic. The two phase I trials are ongoing. Citation Format: Matthew S. Block, Jean-Pierre Delord, Christian H. Ottensmeier, Christophe Le Tourneau, Ana Lalanne, Olivier Lantz, Keith L. Knutson, Gisèle Lacoste, Annette Tavernaro, Maud Brandely, Nathalie Silvestre, Benoit Grellier, Yoshiko Yamashita, Onoue Kousuke, Naoko Yamagata, Eric Quemeneur, Kaidre Bendjama. Phase I trials of personalized cancer vaccine TG4050 in surgically treated high-risk head and neck squamous cell carcinoma (HNSCC) and relapsing ovarian cancer (OvC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT182.

Background Immune checkpoint blockade (ICB) is a clinically proven concept to treat cancer. Still, a majority of cancer patients including those with poorly immune infiltrated “cold” tumors are resistant to currently available ICB therapies. Oncolytic viruses are natural immunomodulators able to turn “cold” tumors “hot” and, for some of them, to deliver therapeutic payloads intratumorally. Payloads of choice are those with tolerability and/or pharmacokinetic/biodistribution issues, such as @CTLA4 antibodies and GM-CSF respectively. Here, Transgene and BioInvent present a preclinical characterization of a highly efficacious and potentially safe strategy to target CTLA-4 and GM-CSF using vectorization in an oncolytic vaccinia virus. Methods A novel human IgG1 CTLA-4 antibody (4-E03) was identified using function-first screening for mAbs and targets associated with checkpoint blocking and superior Treg depleting activity. A tumor-selective oncolytic Vaccinia vector was then engineered to encode this novel αCTLA-4 as full-length antibody (i.e. distinct transgenes for light and heavy chains) and GM-CSF (VVGM-αhCTLA4, BT-001). Viruses encoding matching mouse surrogate payloads were additionally generated, enabling proof-of-concept studies in syngeneic immune competent mouse tumor models. Results Our studies demonstrate that two chains cloning approach allowed to express @CTLA4 at a high level in numerous infected human tumor cell lines without affecting replication, oncolytic activity or genetic stability of the virus. Intratumoral (i.t.) administration of VVGM-αCTLA4 achieved tumor-restricted CTLA-4 receptor saturation at least for 10 days, Treg-depletion antigen cross-presentation, stronger systemic expansion of tumor-specific CD8+ T cells and antitumor immunity compared with systemic αCTLA-4 antibody or unarmed virus therapies. Remarkably, in a clinically relevant mouse model resistant to systemic immune checkpoint blockade, i.t. VVGM-αCTLA4 synergized with αPD-1 to reject “cold” tumors. Conclusion Our findings demonstrate in vivo proof-of-concept for tumor delivery by Vaccinia virus of GM-CSF and strongly Treg-depleting, immune checkpoint blocking, vectorized αCTLA-4. This vector-based delivery is a highly effective and safe strategy to target CTLA-4 which overcomes current limitations of approved αCTLA-4 regimens. A clinical trial evaluating i.t. VVGM-αhCTLA4 (BT-001) alone and in combination with αPD-1 in metastatic or advanced solid tumors has been initiated. Citation Format: Jean-Baptiste Marchand, Monika Semmrich, Christelle Ziller, Matilda Rehn, Laetitia Fend, Petra Holmkvist, Nathalie Silvestre, Carolin Svensson, Kleinpeter Patricia, Jules Deforges, Fred Junghus, Linda Mårtensson, Johann Foloppe, Ingrid Teige, Björn Frendéus, Eric Quéméneur. Comprehensive preclinical studies of BT-001: An oncolytic vaccinia virus armed with Treg-depleting @CTLA4 and GM-CSF [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3567.

2637 Background: Mutation-associated neoantigens (MANAs) constitute attractive antigens for the design of cancer vaccines. However, clinical implementation remains challenging because of the patient specific nature of MANAs, hereby requiring that a bespoke vaccine is designed for each subject. We developed a pipeline for the genomic characterization and the design of tailored vaccine using a modified vaccinia Ankara viral vector. Methods: Immunogenicity, safety and early clinical activity of personalized cancer vaccines are being assessed in two phase I trials, respectively in high grade serous OC and HPV-negative HNSCC. Patients (Pts) at high risk of relapse are enrolled in the study being in remission following surgical primary treatment. High risk is defined as stage IIIC or IVA for OC and stage III or IVA for HNSCC. A vaccine is manufactured for each patient. OC pts are treated at asymptomatic relapse based on radiological finding or elevation of CA-125 with the vaccine alone; HNSCC pts in complete remission after surgery and adjuvant therapy are randomized to receive the vaccine either at the end of locoregional treatment or in combination with standard of care at relapse. The vaccine was administered weekly for 6 weeks and a booster dose every three weeks over a year or until progression, whichever occurred first. Results: At the time of the data cut-off, a total of 8 pts were treated: 4 relapsing OC pts, 3 HNSCC pts in complete remission and 1 relapsing HNSCC pt. AE attributable to the vaccine were mainly grade 1 injection site reactions and fatigue. One OC pt displayed an objective response 6 weeks after initiation of vaccine and for 9 months with a normalization of CA-125 until death from an unrelated cause; 1 other OC pt remains on treatment with a stable radiological disease for 11 months. The 2 other OC progressed at the first evaluation on day 43. HNSCC pts treated in complete remission received respectively 20, 15 and 4 doses, and remain on treatment and disease free. One HNSCC patient received 9 doses of vaccine after relapse in conjunction with chemotherapy and anti-PD-1 therapy and remains on treatment with stable disease after 5 months. Immune monitoring demonstrates priming of a polyepitopic T cell response against class I and II antigens. Responses were observed regardless of HLA and without cross-reactivity to the germline protein. Adaptive response was associated with a shift of CD4 and CD8 T cells toward an effector phenotype and innate cellular immunity was activated with a strong maturation and activation of NK cells. Immune changes were stronger in pts with controlled disease versus progressors. Conclusions: Data demonstrate that TG4050 is safe, well tolerated and able to induce T cell responses whatever the HLA haplotype. Early signs of clinical activity were observed in OC pt. These data pave the way for further development and synergistic immunotherapeutic combinations. Clinical trial information: NCT04183166.

International audience; As a live biologic agent, oncolytic vaccinia virus has the ability to target and selectively amplify at tumor sites. We have previously reported that deletion of thymidine kinase and ribonucleotide reductase genes in vaccinia virus can increase the safety and efficacy of the virus. Here, to allow direct visualization of the viral genome in living cells, we incorporated the ANCH target sequence and the OR3-Santaka gene in the double-deleted vaccinia virus. Infection of human tumor cells with ANCHOR3-tagged vaccinia virus enables visualization and quantification of viral genome dynamics in living cells. The results show that the ANCHOR technology permits the measurement of the oncolytic potential of the double deleted vaccinia virus. Quantitative analysis of infection kinetics and of viral DNA replication allow rapid and efficient identification of inhibitors and activators of oncolytic activity. Our results highlight the potential application of the ANCHOR technology to track vaccinia virus and virtually any kind of poxvirus in living cells.

Background Checkpoint inhibitor antibodies have improved survival in a variety of cancers, however, a great unmet need remains since only a small fraction of patients responds. Reasons for lack of efficacy are believed to include lack of tumor infiltrating immune cells, a notion supported by improved efficacy observed following combined checkpoint blockade with tumor oncolytic virotherapy which promotes intratumoral T cell infiltration. Oncolytic vaccinia viruses (oVV) also allow genetic encoding of transgenes. This is of special interest for therapeutic proteins exhibiting toxicological limitation or pharmacokinetic issues. Here, BioInvent and Transgene present a potentially safe and more efficacious strategy to combine checkpoint inhibition in the context of oncolytic virotherapy. Methods Using the F.I.R.S.T™ discovery platform we have isolated a human recombinant Treg-depleting antibody that has been vectorized alongside GM-CSF into the Invir.IO® oVV. This product named BT-001 consists of a Copenhagen double deleted vaccinia virus encoding the human CTLA4-specific antibody 4-E03 IgG1, which shows improved Treg-depletion compared with ipilimumab in a human PBMC-based NOG/SCID-transfer model. BT-001 also encodes GM-CSF, the cytokine expressed in clinically approved products. A surrogate murine mAb was vectorized into the same oVV (mBT-1) allowing for functional and mechanistic in vivo studies. Results Our studies demonstrate that 4-E03 and GM-CSF were expressed as functional molecules after infection by BT-001 of human tumor cell lines in vitro. Moreover, following intratumoral administration in immune competent and immune deficient mice transplanted with mouse or human tumors, transgene expression was sustained at levels associated with receptor saturation for days to weeks. In contrast, and supporting the tumor-selective nature of oVV, blood concentrations of anti-CTLA4 mAb were lower compared to those observed following i.v. administration of therapeutic doses of mAb. The in vivo anti-tumor activity of mBT-1 was assessed in multiple syngeneic mouse tumor models including CT26, EMT6, A20 and C38. Murine surrogate mBT-1 conferred cures in the majority of challenged mice irrespective of tumor origin. The excellent anti-tumoral profile depends on anti-CTLA4 expression and could be boosted by co-administration of anti-PD-1 mAb. Intratumoral treatment with mBT-1 also induces abscopal anti-tumor responses and protects against tumor rechallenge demonstrating a long-lasting systemic anti-tumor activity. Conclusions A clinical batch of BT-001 has been produced and toxicological evaluation is ongoing. Transgene and BioInvent have applied for a clinical trial targeting injectable superficial tumors. Here, the tumor-localized delivery of anti-CTLA4 may allow a better tolerated and more effective combination therapy with antibodies targeting the PD-1/PDL1 axis.

BackgroundCancer is characterized by an accumulation of somatic mutations, of which a significant subset can generate cancer-specific neoepitopes that are recognized by autologous T cells. Such neoepitopes are emerging as important targets for cancer immunotherapy, including personalized cancer vaccination strategies.MethodsWe used whole-exome and RNA sequencing analysis to identify potential neoantigens for a patient with non-small cell lung cancer. Thereafter, we assessed the autologous T-cell reactivity to the candidate neoantigens using a long peptide approach in a cultured interferon gamma ELISpot and tracked the neoantigen-specific T-cells in the tumor by T-cell receptor (TCR) sequencing. In parallel, identified gene variants were incorporated into a Modified Vaccinia Ankara-based vaccine, which was evaluated in the human leucocyte antigen A*0201 transgenic mouse model (HHD).ResultsSequencing revealed a tumor with a low mutational burden: 2219 sequence variants were identified from the primary tumor, of which 23 were expressed in the transcriptome, involving 18 gene products. We could demonstrate spontaneous T-cell responses to 5/18 (28%) mutated gene variants, and further analysis of the TCR repertoire of neoantigen-specific CD4+ and CD8+ T cells revealed TCR clonotypes that were expanded in both blood and tumor tissue. Following vaccination of HHD mice, de novo T-cell responses were generated to 4/18 (22%) mutated gene variants; T cells reactive against two variants were also evident in the autologous setting. Subsequently, we determined the major histocompatibility complex restriction of the T-cell responses and used in silico prediction tools to determine the likely neoepitopes.ConclusionsOur study demonstrates the feasibility of efficiently identifying tumor-specific neoantigens that can be targeted by vaccination in tumors with a low mutational burden, promising successful clinical exploitation, with trials currently underway., publishedVersion

Pre-clinical models mimicking persistent hepatitis B virus (HBV) expression are seldom, do not capture all features of a human chronic infection and due to their complexity, are subject to variability. We report a meta-analysis of seven experiments performed with TG1050, an HBV-targeted immunotherapeutic,1 in an HBV-persistent mouse model based on the transduction of mice by an adeno-associated virus coding for an infectious HBV genome (AAV-HBV). To mimic the clinical diversity seen in HBV chronically infected patients, AAV-HBV transduced mice displaying variable HBsAg levels were treated with TG1050. Overall mean percentages of responder mice, displaying decrease in important clinical parameters i.e. HBV-DNA (viremia) and HBsAg levels, were 52% and 51% in TG1050 treated mice, compared with 8% and 22%, respectively, in untreated mice. No significant impact of HBsAg level at baseline on response to TG1050 treatment was found. TG1050-treated mice displayed a significant shorter Time to Response (decline in viral parameters) with an Hazard Ratio (HR) of 8.3 for viremia and 2.6 for serum HBsAg. The mean predicted decrease for TG1050-treated mice was 0.5 log for viremia and 0.8 log for HBsAg, at the end of mice follow-up, compared to no decrease for viremia and 0.3 log HBsAg decrease for untreated mice. For mice receiving TG1050, a higher decline of circulating viremia and serum HBsAg level over time was detected by interaction term meta-analysis with a significant treatment effect (p = 0.002 and p

BackgroundImmune checkpoint blockade (ICB) is a clinically proven concept to treat cancer. Still, a majority of cancer patients including those with poorly immune infiltrated “cold” tumors are resistant to currently available ICB therapies. CTLA-4 is one of few clinically validated targets for ICB, but toxicities linked to efficacy in approved anti-CTLA-4 regimens have restricted their use and precluded full therapeutic dosing. At a mechanistic level, accumulating preclinical and clinical data indicate dual mechanisms for anti-CTLA-4; immune checkpoint blockade and Treg depletion are both thought to contribute efficacy and toxicity in available, systemic, anti-CTLA-4 regimens. Accordingly, strategies to deliver highly effective, yet safe, anti-CTLA-4 therapies have been lacking. Here, BioInvent and Transgene present and preclinically characterize a highly efficacious and potentially safe strategy to target CTLA-4 in the context of oncolytic virotherapy.MethodsA novel human IgG1 CTLA-4 antibody (4-E03) was identified using function-first screening for mAbs and targets associated with superior Treg depleting activity. A tumor-selective oncolytic Vaccinia vector was then engineered to encode this novel, strongly Treg-depleting, checkpoint-blocking, anti-CTLA-4 antibody and GM-CSF (VVGM-ahCTLA4, BT-001). Viruses encoding a matching Treg-depleting mouse surrogate antibody were additionally generated, enabling proof-of-concept studies in syngeneic immune competent mouse tumor models.ResultsOur studies demonstrate that intratumoral (i.t.) administration of VVGM-aCTLA4 achieved tumor-restricted CTLA-4 receptor saturation and Treg-depletion, which elicited antigen cross-presentation and stronger systemic expansion of tumor-specific CD8+ T cells and antitumor immunity compared with systemic anti-CTLA-4 antibody therapy. Efficacy correlated with FcgR-mediated intratumoral Treg-depletion and the reduction of exhausted CD8+ T cells. Remarkably, in a clinically relevant mouse model resistant to systemic immune checkpoint blockade, i.t. VVGM-aCTLA4 synergized with anti-PD-1 to reject “cold” tumors.ConclusionsOur findings demonstrate in vivo proof-of-concept for spatial restriction of strongly Treg-depleting, immune checkpoint blocking, vectorized anti-CTLA-4 as a highly effective and safe strategy to target CTLA-4 which is able to overcome current limitations of approved anti-CTLA-4 regimens. A clinical trial evaluating i.t. VVGM-ahCTLA4 (BT-001) alone and in combination with anti-PD-1 in metastatic or advanced solid tumors has commenced.Ethics ApprovalAll mouse experiments were approved by the local ethical committee for experimental animals (Malmö/Lunds djurförsöksetiska nämnd); at BioInvent under permit numbers 17196/2018 or 2934/2020; or at Transgene APAFIS Nr21622 project 2019072414343465 and performed in accordance with local ethical guidelines.

Tuberculosis (TB) still is the principal cause of death from infectious disease and improved vaccination strategies are required to reduce the disease burden and break TB transmission. Here, we investigated different routes of administration of vectored subunit vaccines based on chimpanzee-derived adenovirus serotype-3 (ChAd3) for homologous prime-boosting and modified vaccinia virus Ankara (MVA) for heterologous boosting with both vaccine vectors expressing the same antigens from Mycobacterium tuberculosis (Ag85B, ESAT6, Rv2626, Rv1733, RpfD). Prime-boost strategies were evaluated for immunogenicity and protective efficacy in highly susceptible rhesus macaques. A fully parenteral administration regimen was compared to exclusive respiratory mucosal administration, while parenteral ChAd3-5Ag prime-boosting and mucosal MVA-5Ag boosting were applied as a push-and-pull strategy from the periphery to the lung. Immune analyses corroborated compartmentalized responses induced by parenteral versus mucosal vaccination. Despite eliciting TB-specific immune responses, none of the investigational regimes conferred a protective effect by standard readouts of TB compared to non-vaccinated controls, while lack of protection by BCG underpinned the stringency of this non-human primate test modality. Yet, TB manifestation after full parenteral vaccination was significantly less compared to exclusive mucosal vaccination.

The vaccinia virus harbors in its genome several genes dedicated to the inhibition of the host immune response. Among them, M2L was reported to inhibit the intracellular NF-κB pathway. We report here several new putative immunosuppressive activities of M2 protein. M2 protein is secreted and binds cornerstone costimulatory molecules (CD80/CD86). M2 binding to CD80/CD86 blocks their interaction with soluble CD28/CTLA4 but also favors the soluble PD-L1-CD80 association. These findings open the way for new investigations deciphering the immune system effects of soluble M2 protein. Moreover, a vaccinia virus with a deletion of its M2L has been generated and characterized as a new oncolytic platform. The replication and oncolytic activities of the M2L-deleted vaccinia virus are indistinguishable from those of the parental virus. More investigations are needed to characterize in detail the immune response triggered against both the tumor and the virus by this M2-defective vaccinia virus., In this article we report that the M2 protein encoded by the vaccinia virus is secreted as a homo-oligomer by infected cells and binds two central costimulation molecules, CD80 (B7-1) and CD86 (B7-2). These interactions block the ligation of the two B7 proteins to both soluble CD28 and soluble cytotoxic T-lymphocyte associated protein 4 (CTLA4) but favor the binding of soluble PD-L1 to soluble CD80. M2L gene orthologues are found in several other poxviruses, and the B7-CD28/CTLA4 blocking activity has been identified for several culture supernatants of orthopoxvirus-infected cells and for a recombinant myxoma virus M2 protein homolog (i.e., Gp120-like protein, or Gp120LP). Overall, these data indicate that the M2 poxvirus family of proteins may be involved in immunosuppressive activities broader than the NF-κB inhibition already reported (R. Gedey, X. L. Jin, O. Hinthong, and J. L. Shisler, J Virol 80:8676–8685, 2006, https://doi.org/10.1128/JVI.00935-06). A Copenhagen vaccinia virus with a deletion of the nonessential M2L locus was generated and compared with its parental virus. This M2L-deleted vaccinia virus, unlike the parental virus, does not generate interference with the B7-CD28/CTLA4/PD-L1 interactions. Moreover, this deletion did not affect any key features of the virus (in vitro replication, oncolytic activities in vitro and in vivo, and intratumoral expression of a transgene in an immunocompetent murine model). Altogether, these first results suggest that the M2 protein has the potential to be used as a new immunosuppressive biotherapeutic and that the M2L-deleted vaccinia virus represents an attractive new oncolytic platform with an improved immunological profile. IMPORTANCE The vaccinia virus harbors in its genome several genes dedicated to the inhibition of the host immune response. Among them, M2L was reported to inhibit the intracellular NF-κB pathway. We report here several new putative immunosuppressive activities of M2 protein. M2 protein is secreted and binds cornerstone costimulatory molecules (CD80/CD86). M2 binding to CD80/CD86 blocks their interaction with soluble CD28/CTLA4 but also favors the soluble PD-L1-CD80 association. These findings open the way for new investigations deciphering the immune system effects of soluble M2 protein. Moreover, a vaccinia virus with a deletion of its M2L has been generated and characterized as a new oncolytic platform. The replication and oncolytic activities of the M2L-deleted vaccinia virus are indistinguishable from those of the parental virus. More investigations are needed to characterize in detail the immune response triggered against both the tumor and the virus by this M2-defective vaccinia virus.

Oncolytic virotherapy is a clinically validated class of immune modulatory drugs with activity in solid cancer. The mode of action of armed oncolytic Vaccinia viruses (oVV) includes cell death induction following selective replication in tumor cells, local inflammation and priming of adaptive immune responses, and intra-tumoral delivery of therapeutic modalities e.g. antibodies, cytokines, enzymes and engineered receptor ligands. BioInvent and Transgene are collaborating in the development of a next generation armed oncolytic viruses, bringing respectively their n-CoDeR F.I.R.S.T antibody (mAb) discovery and Invir.IO oVV platforms. The first product, named BT-001, consists of the Copenhagen oVV strain deleted in J2R and I4L viral genes allowing restricted replication in proliferating cells, and the human IgG1 4-E03 recognizing human CTLA4. 4-E03 shows improved Treg-depleting activity compared with ipilimumab. BT-001 also encodes GM-CSF, the cytokine expressed in clinically advanced products like T-Vec (Imlygic) or Pexa-Vec. A surrogate mAb with similar pronounced Treg-depleting properties to 4-E03 was vectorized into the same oVV (mBT-1) allowing for functional and mechanistic in vivo studies. Since virus replication and expression of recombinant transgenes are tightly linked, the armed oVV is an interesting design for intra-tumoral delivery of therapeutic proteins exhibiting toxicological limitation (e.g. anti-CTLA4) and/or pharmacokinetic issues (e.g. GM-CSF). Oncoviral tumor-localized delivery of anti-CTLA4 may also allow better tolerated and more effective combination therapy with approved antibodies targeting the PD-1/PDL1 axis. Our studies demonstrate that 4-E03 and GM-CSF were expressed at high level as functional molecules after infection by BT-001 of several human tumoral cell lines in vitro. Moreover, following intratumoral administration in immune competent and immune deficient mice transplanted with mouse or human tumors, transgene expression was sustained at levels associated with receptor saturation for days to weeks. In contrast, and supporting the tumor-selective nature of oVV, blood concentrations of anti-CTLA4 mAb were lower compared to those observed following I.V. administration of therapeutic doses (3 mg/kg) of mAb. The in vivo anti-tumor activity of mBT-1 was assessed in multiple syngeneic mouse tumor models including CT26, EMT6, A20, and C38. mBT-1 conferred cures in the majority of challenged mice irrespective of tumor origin. The excellent anti-tumoral profile depends on anti-CTLA4 expression and could be boosted by co-administration of anti-PD-1 mAb. A clinical batch of BT-001 has been produced and toxicological evaluation is ongoing. Transgene and BioInvent are preparing CTA and IND filings for a multicentre clinical trial targeting injectable superficial tumors. Citation Format: Jean-Baptiste Marchand, Monika Semmrich, Laetitia Fend, Matilda Rehn, Nathalie Silvestre, Ingrid Teige, Johann Foloppe, Linda Mårtensson, Eric Quéméneur, Björn Frendeus. BT-001, an oncolytic vaccinia virus armed with a Treg-depletion-optimized recombinant human anti-CTLA4 antibody and GM-CSF to target the tumor microenvironment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5602.

The recombinant Vaccinia virus Copenhagen strain deleted in Thymidine Kinase and Ribonucleotide Reductase (VVCOPTK−RR−) is a potent and versatile oncolytic platform that has demonstrated strong activity in various preclinical models. The deletion of such VV genes inhibits viral replication in normal cells, while retaining therapeutic replication in tumor cells. TG6002, a VVCOPTK−RR− expressing the suicide gene FCU1, is under investigation in Phase I trials in patients with advanced gastrointestinal tumors. We have developed a new product based on the VVCOPTK−RR− vector, named TG6010, expressing the human cytidine deaminase (CDA) that efficiently catalyzes the deamination of cytidine and deoxycytidine to uridine and deoxyuridine, respectively. The tumor specific expression of CDA by the VV leads to a depletion of cytidine and deoxycytidine. This cytidine/deoxycytidine depletion resulting from CDA overexpression, activated a DNA damage response highlighted by an induction of H2AX phosphorylation. Next, to validate the potential therapeutic use of TG6010, we analyzed the effects of the virus on human xenograft tumors implanted in mice. We observed, after systemic injection of TG6010, high expression of CDA in the tumors with a significant increase in DNA damage in vivo as revealed by the γH2AX foci assay. In addition, intraperitoneal administration of TG6010 in a xenograft model of human ovarian carcinomatosis resulted in significantly prolonged animal survival. In conclusion, the oncolytic vaccinia virus expressing the cytidine deaminase (TG6010) has shown potent anti-tumor effects. Mechanistically, due to the cytidine deaminase overexpression, we observed induction of a DNA damage response. These are data encouraging of clinical development for this highly potent oncolytic Vaccinia virus TG6010 against ovarian cancer. Citation Format: Johann Foloppe, Juliette Kempf, Christelle Pichon, Annie Findeli, Isabelle Farine, Julie Hortelano, Baptiste Moreau, Michèle Klein, Sandrine Cochin, Renée Brandely, Véronique Koerper, Nathalie Silvestre, Christelle Machon, Jérôme Guitton, Eric Quéméneur, Philippe Erbs. Oncolytic vaccinia virus TG6010 expressing cytidine deaminase induces DNA damage and shows potent anti-tumor effects [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4576.

Despite the existence of the prophylactic Bacille Calmette-Guérin (BCG) vaccine, infection by Mycobacterium tuberculosis (Mtb) remains a major public health issue causing up to 1.8 million annual deaths worldwide. Increasing prevalence of Mtb strains resistant to antibiotics represents an urgent threat for global health that has prompted a search for alternative treatment regimens not subject to development of resistance. Immunotherapy constitutes a promising approach to improving current antibiotic treatments through engagement of the host’s immune system. We designed a multi-antigenic and multiphasic vaccine, based on the Modified Vaccinia Ankara (MVA) virus, denoted MVATG18598, which expresses ten antigens classically described as representative of each of different phases of Mtb infection. In vitro analysis coupled with multiple-passage evaluation demonstrated that this vaccine is genetically stable, i.e. fit for manufacturing. Using different mouse strains, we show that MVATG18598 vaccination results in both Th1-associated T-cell responses and cytolytic activity, targeting all 10 vaccine-expressed Mtb antigens. In chronic post-exposure mouse models, MVATG18598 vaccination in combination with an antibiotic regimen decreases the bacterial burden in the lungs of infected mice, compared with chemotherapy alone, and is associated with long-lasting antigen-specific Th1-type T cell and antibody responses. In one model, co-treatment with MVATG18598 prevented relapse of the disease after treatment completion, an important clinical goal. Overall, results demonstrate the capacity of the therapeutic MVATG18598 vaccine to improve efficacy of chemotherapy against TB. These data support further development of this novel immunotherapeutic in the treatment of Mtb infections.

Objective To assess a new adenovirus-based immunotherapy as a novel treatment approach to chronic hepatitis B (CHB). Methods TG1050 is a non-replicative adenovirus serotype 5 encoding a unique large fusion protein composed of a truncated HBV Core, a modified HBV Polymerase and two HBV Envelope domains. We used a recently described HBV-persistent mouse model based on a recombinant adenovirus-associated virus encoding an over length genome of HBV that induces the chronic production of HBsAg, HBeAg and infectious HBV particles to assess the ability of TG1050 to induce functional T cells in face of a chronic status. Results In in vitro studies, TG1050 was shown to express the expected large polyprotein together with a dominant, smaller by-product. Following a single administration in mice, TG1050 induced robust, multispecific and long-lasting HBV-specific T cells detectable up to 1 year post-injection. These cells target all three encoded immunogens and display bifunctionality (ie, capacity to produce both interferon γ and tumour necrosis factor α as well as cytolytic functions). In addition, control of circulating levels of HBV DNA and HBsAg was observed while alanine aminotransferase levels remain in the normal range. Conclusions Injection of TG1050 induced both splenic and intrahepatic functional T cells producing cytokines and displaying cytolytic activity in HBV-naive and HBV-persistent mouse models together with significant reduction of circulating viral parameters. These results warrant clinical evaluation of TG1050 in the treatment of CHB.

Women showing normal cytology but diagnosed with a persistent high-risk human papillomavirus (HR-HPV) infection have a higher risk of developing high-grade cervical intraepithelial neoplasia and cervical cancer than noninfected women. As no therapeutic management other than surveillance is offered to these women, there is a major challenge to develop novel targeted therapies dedicated to the treatment of these patients. As such, E1 and E2 antigens, expressed early in the HPV life cycle, represent very interesting candidates. Both proteins are necessary for maintaining coordinated viral replication and gene synthesis during the differentiation process of the epithelium and are essential for the virus to complete its normal and propagative replication cycle. In the present study, we evaluated a new active targeted immunotherapeutic, a modified vaccinia virus Ankara (MVA) vector containing the E1 sequence of HPV16, aimed at inducing cellular immune responses with the potential to help and clear persistent HPV16-related infection. We carried out an extensive comparative time course analysis of the cellular immune responses induced by different schedules of immunization in C57BL/6 mice. We showed that multiple injections of MVA-E1 allowed sustained HPV16 E1-specific cellular immune responses in vaccinated mice and had no impact on the exhaustion phenotype of the generated HPV16 E1-specific CD8+T cells, but they led to the differentiation of multifunctional effector T cells with high cytotoxic capacity. This study provides proof of concept that an MVA expressing HPV16 E1 can induce robust and long-lasting E1-specific responses and warrants further development of this candidate.

Engineered viral vectors are effective approaches to stimulate anti-tumor immunity, and change the tumor immune environment. Several viruses and strains have been developed to express tumor antigens and cytokines, and corresponding products are in advanced clinical trials. However, novel viral strains with improved immunogenic properties are sought. In this perspective, we screened a variety of poxviridae potentially usable in humans: Cowpox (CPX), Pseudocowpox (PCPV), Parapoxvirus Ovis (ORF), Myxoma virus (MYX), Swinepox (SWP), Yaba-like disease virus (YLDV), Raccoonpox (RCN), Cotia virus (CTV), and compared them to the well-established vaccine strain Modified Virus Ankara (MVA), and oncolytic Vaccinia Virus, strain Copenhagen (VV). Both in vitro with human primary immune cells, and in vivo with syngeneic mouse tumor models, PCPV proved to be a very promising vector for immunotherapy. Compared with MVA, PCPV induced a 1000-fold higher expression of IFN-alpha in human PBMCs, whereas SWPV and ORF displayed a lower 10 to 100-fold induction. Other viruses (i.e. VV, RCN, CTV, or MYX) did not raise the IFN-alpha level. PCPV was also shown to increase the level of GM-CSF, and to be safe for PBMCs, in contrast to ORF which displayed some cytotoxic effects. When tested for its capacity to trigger the expression of CD86, a co-stimulatory factor for T-cell activation, PCPV was shown to be superior than MVA in primary moDCs. Furthermore, PCPV treatment increased CD86 expression in human CD163+CD206+ “M2”-type macrophages derived from CD14+ monocytes, suggesting a shift to an antigen-presenting phenotype. In these cells, PCPV increased significantly the secretion of IL-18, IL-6 and IP-10, signing a conversion towards a less suppressive macrophage phenotype. Last, incubation of PCPV in a co-culture model overcame the immunosuppressive effect of MDSCs on human autologous CD8+ T. A GFP-encoding recombinant PCPV vector was generated, and we could demonstrate that PCPV was capable of infecting human primary immune cells, comparably to recombinant MVA vectors, except for activated T cells. A recombinant PCPV encoding for the HPV E7 protein was generated to assess the anti-tumor activity and immunogenicity in a syngeneic murine tumor model. Like MVA-E7, PCPV-E7 induced a strong cellular response (ELISPOT on splenocytes, and frequency of antigen-specific short-lived effector cells), but PCPV-E7 displayed a different cytokine/chemokine profile at the site of injection, with increased levels of pro-immune cytokines including IP-10, IFN-gamma, GM-CSF, IL-18, MIP-1 alpha, MIP-1 beta, IL-12 and IL-6. When injected intratumorally into fast growing MC-38 tumors, PCPV led to tumor control. Analysis of tumors infiltrates showed that PCPV treatment led to higher levels of neutrophils and decreased the frequency of MHCIIlo TAMs. Our data demonstrate that PCPV might display better properties than current viral vectors, in terms of local response and priming activity, of ability to induce effector T cells and to reshape the tumor infiltration profiles. It has the same capacity as other poxviruses to encode and deliver large genetic payload, which will be useful for designing advanced anti-tumor vaccines. Citation Format: Karola Rittner, Marine Ricordel, Caroline Tosch, Christine Thioudellet, Christelle Remy-Ziller, Marie-Christine Claudepierre, Chantal Hoffmann, Doris Schmitt, Benoit Sansas, Johann Foloppe, Philippe Erbs, Nathalie Silvestre, Kaïdre Bendjama, Eric Quemeneur. Pseudocowpox: A next generation viral vector for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-287.

We report here the successful vectorization of a hamster monoclonal IgG (namely J43) recognizing the murine Programmed cell death-1 (mPD-1) in Western Reserve (WR) oncolytic vaccinia virus. Three forms of mPD-1 binders have been inserted into the virus: whole antibody (mAb), Fragment antigen-binding (Fab) or single-chain variable fragment (scFv). MAb, Fab and scFv were produced and assembled with the expected patterns in supernatants of cells infected by the recombinant viruses. The three purified mPD-1 binders were able to block the binding of mPD-1 ligand to mPD-1 in vitro. Moreover, mAb was detected in tumor and in serum of C57BL/6 mice when the recombinant WR-mAb was injected intratumorally (IT) in B16F10 and MCA 205 tumors. The concentration of circulating mAb detected after IT injection was up to 1,900-fold higher than the level obtained after a subcutaneous (SC) injection (i.e., without tumor) confirming the virus tropism for tumoral cells and/or microenvironment. Moreover, the overall tumoral accumulation of the mAb was higher and lasted longer after IT injection of WR-mAb1, than after IT administration of 10 µg of J43. The IT injection of viruses induced a massive infiltration of immune cells including activated lymphocytes (CD8+ and CD4+). Interestingly, in the MCA 205 tumor model, WR-mAb1 and WR-scFv induced a therapeutic control of tumor growth similar to unarmed WR combined to systemically administered J43 and superior to that obtained with an unarmed WR. These results pave the way for next generation of oncolytic vaccinia armed with immunomodulatory therapeutic proteins such as mAbs.

A 100-fold increase in luciferase activity was observed in 293 cells, stably expressing Epstein-Barr nuclear antigen 1 (EBNA1; 293-EBNA1 cells), that had been transiently transfected with plasmids carrying Epstein-Barr virus (EBV) oriP sequences. This increase was observed in comparison to reporter gene activity obtained after transfection with a plasmid carrying no oriP sequences. The luciferase gene on these plasmids was under the control of either the cytomegalovirus immediate-early 1 gene enhancer-promoter (CMV IE1) or the Rous sarcoma virus promoter. The increase of reporter gene activity was not due to plasmid replication, since a similar enhancement was observed in the presence of aphidicolin, an inhibitor of replicative DNA synthesis, or after deletion of the dyad symmetry ( DS ) element within oriP . Luciferase production was not increased in the presence of only the DS element. Microinjection of plasmids carrying the CMV IE1 promoter-driven luciferase gene with or without oriP sequences into the nuclei of 293-EBNA1 cells resulted in a 17-fold increase in luciferase activity. Cytoplasmic injection of these plasmids led to an enhancement of luciferase activity of up to 100-fold. This difference in the factor of activation after nuclear or cytoplasmic injection could be ascribed to increased transport of plasmids carrying oriP from the cytoplasm to the nucleus in the presence of EBNA1. These data suggest the possibility of substantially increasing the apparent expression of a gene under the control of a strong constitutive promoter in the presence of oriP sequences and EBNA1. This improvement in expression is due to intranuclear enhancement of gene expression. oriP -specific transport of plasmid DNA from the cytoplasm of 293-EBNA1 cells to the nucleus seems to contribute to the observed effect.

Development of active targeted immunotherapeutics is a rapid developing field in the arena of chronic infectious diseases. The question of repeated, closely spaced administration of immunotherapeutics to achieve a rapid impact on the replicating agent is an important one. We analyzed here, using a prototype adenovirus-based immunotherapeutic encoding Core and Polymerase from the hepatitis B virus (Ad-HBV), the influence of closely spaced repeated immunizations on the level and quality of induced HBV-specific and vector-specific immune responses in various mouse models. Ad-HBV, whether injected once or multiple times, was able to induce HBV- and adeno-specific T cells both in HBV-free mice and in a HBV tolerant mouse model. Adenovirus-specific T cell responses and titers of neutralizing anti-Ad5 antibodies increased from time of the 3rd injection. Interestingly, single or multiple Ad-HBV injections resulted in detection of Polymerase-specific functional T cells in HBV tolerant mice. Overall no modulation of the levels of HBV-specific cytokine-producing (IFNγ/TNFα) and cytolytic T cells was observed following repeated administrations (3 or 6 weekly injections) when compared with levels detected after a single injection with the exception of two markers: 1. the proportion of HBV-specific IFNγ-producing cells bearing the CD27+/CD43+ phenotype appeared to be sustained in C57BL/6J mice following 6 weekly injections; 2. the percentage of IFNγ/TNFα Core-specific producing cells observed in spleens of HLA-A2 mice as well as of that specific of Polymerase observed in livers of HBV tolerant mice was maintained. In addition, percentage of HBV-specific T cells expressing PD-1 was not increased by multiple injections. Overall these data show that, under experimental conditions used, rapid, closely spaced administrations of an adenovirus-based HBV immunotherapeutics does not inhibit induced T-cell responses including in a HBV-tolerant environment.

We report here the successful vectorization of a hamster monoclonal IgG (namely J43) recognizing the murine Programmed cell death-1 (mPD-1) in Western Reserve (WR) oncolytic vaccinia virus. Three forms of mPD-1 binders have been inserted in the virus: whole antibody (mAb), Fragment antigen-binding (Fab) or single-chain variable fragment (scFv). MAb, Fab and scFv were produced and assembled with the expected patterns in supernatants of cells infected by the recombinant viruses. The 3 purified mPD-1 binders were able to block the binding of mPD-1 ligand to mPD-1 in vitro. Moreover, mAb was detected in tumor and in serum of C57BL/6 mice when the recombinant WR-mAb was injected intratumorally (IT) in B16F10 and MCA 205 tumors. The concentration of circulating mAb detected after IT injection was up to 1900-fold higher than the level obtained after a subcutaneous (SC) injection (i.e. without tumor) confirming the virus tropism for tumoral cells and/or that tumoral microenvironment allows virus escape from immune surveillance. Moreover, the overall tumoral accumulation of the mAb was higher and lasted longer after IT injection of WR-mPD-1, than after IT administration of 10 μg of J43. Interestingly, in the MCA 205 tumor model, WR-mPD-1 (both mAb and scFv) induced a therapeutic control of tumor growth similar to unarmed WR combined to systemically administered J43 and superior to that provided by an unarmed WR. These results pave the way for next generation of oncolytic vaccinia armed with immunomodulatory therapeutic proteins such as mAbs. New generation of oncolytic vaccinia virus that will express several transgenes simultaneously may also be designed with the goal of providing to the patients enhanced therapeutic/toxicity ratio. Citation Format: Jean-Baptiste Marchand, Patricia Kleinpeter, Laetitia Fend, Christine Thioudellet, Michel Geist, Nathalie Sfrontato, Véronique Koerper, Renée Brandely, Dominique Villeval, Karola Rittner, Nathalie Silvestre, Philippe Erbs, Laurence Zitvogel, Eric Quemeneur, Xavier Preville. Vectorization in an oncolytic vaccinia virus of an antibody, a Fab and a scFv against programmed cell death -1 (PD-1) allow their intratumoral delivery and an improved tumor-growth inhibition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2352.

Recombinant vaccinia virus with tumor cell specificity may provide a versatile tool either for direct lysis of cancer cells or for the targeted transfer of genes encoding immunomodulatory or toxic molecules. We report the expression of a tumor-specific single-chain antibody on the surface of intracellular mature vaccinia virus particles (IMV). The wild-type p14 externally membrane-associated protein p14 (A27L gene), which is not required for viral binding and replication, was replaced by p14 fusion molecules carrying a single-chain antibody directed against the tumor-associated antigen MUC-1. MUC-1 mucin is an epithelial cell antigen whose aberrant expression plays a role in autoimmunity and tumor immunity in the majority of human carcinomas and multiple myeloma. Fusion protein carrying the single-chain antibody at the NH2-terminal position was expressed and exposed at the envelope of the corresponding recombinant virus. The construct containing the antibody was able to bind a MUC-1 specific 60mer peptide. Moreover, targeted virus infects MUC-1-expressing cells in vitro more efficiently.

We designed and evaluated in HLA-class I transgenic mouse models a hepatitis C virus (HCV) T cell-based MVA vectored vaccine expressing three viral antigens known to be targets of potent CD8+- and CD4+-mediated responses. An accelerated (3 week-based) vaccination induced specific CD8+ T cells harboring two effector functions (cytolytic activity - both in vitro and in vivo- and production of IFNgamma) as well as specific CD4+ T cells recognizing all three vaccine antigens. Responses were long lasting (6 months), boostable by a fourth MVA vaccination and in vivo cross-reactive as demonstrated in a surrogate Listeria-based challenge assay. This candidate vaccine has now moved into clinical trials.

Bacille Calmette-Guérin (BCG) vaccination of new born babies can protect children against tuberculosis (TB), but fails to protect adults consistently against pulmonary TB underlying the urgent need to develop novel TB vaccines. Majority of first generation TB vaccine candidates have relied on a very limited number of antigens typically belonging to the active phase of infection. We have designed a multi-antigenic and multiphasic vaccine, based on the Modified Vaccinia Ankara virus (MVA). Up to fourteen antigens representative of the three phases of TB infection (active, latent and resuscitation) were inserted into MVA. Using three different strains of mouse (BALB/c, C57BL/6 and C3H/HeN), we show that a single vaccination results in induction of both CD4 and CD8 T cells, displaying capacity to produce multiple cytokines together with cytolytic activity targeting a large array of epitopes. As expected, dominance of responses was linked to the mouse haplotype although for a given haplotype, responses specific of at least one antigen per phase could always be detected. Vaccination of non-human primates with the 14 antigens MVA-TB candidate resulted in broad and potent cellular-based immunogenicity. The remarkable plasticity of MVA opens the road to development of a novel class of highly complex recombinant TB vaccines to be evaluated in both prophylactic and therapeutic settings.

s / Journal of Clinical Virology 69 (2015) 223–246 227 evaluated with serial dilutions (106–100 IU/mL; Roche). The quantitative correlation and lower limit of detection were evaluated by use of clinical samples. Findings: Picodroplet digital PCR showed a high degree of linearity (R2 =0.9891) and accuracy (SD≤0.31 log copies/mL; CV≤15%) across their detectable ranges. The quantitative correlation between the picodroplet digital PCR and the Roche TaqMan HCV test was high (R2 =0.9439) across their detectable ranges (106–15 IU/mL). We also found discordance in detection of low HCVRNA samples between the twomethods. In 18 clinical samples (HCV RNA 15 copies/mL, 44.4% with an HCV RNA levels < 15 copies/mL, and in 33.3% of samples the target was not detected. The discordance in low RNA samples needs to be verified using a large sample size. Interpretation: Picodroplet digital PCR could provide a useful method for HCV quantification, especially for low HCV RNA levels, but the approach needs to be further optimised. http://dx.doi.org/10.1016/j.jcv.2015.06.018

Methods: We infected mice with a hepatotropic virus and challenged these mice by injecting TNF. Using knockout mice, as well as biochemical and multiparametric histological methods we analyzed the influence of different pattern recognition receptors. Additionally, we isolated mitochondria from virus-infected mice and performed metabolomic investigations to analyze the role of mitochondria in virus recognition as well as their role in apoptosis execution. Results: We demonstrate that viral infection in hepatocytes is recognized even in the absence of classical pattern recognition receptor signaling. Rather, viral infection of hepatocytes modulates metabolic processes, leads to increased levels of the pro-apoptotic BCL-2 family members Bax and Bad that cause damage to mitochondria. This leads to a downregulation of the anti-apoptotic protein XIAP (X-chromosome linked inhibiting of apoptosis protein). Downregulation of XIAP facilitates TNF-induced activation of the initiator caspase 8 that together with increased mitochondrial sensitivity to activated caspase 8 is responsible for TNF-induced cell death in virus-infected hepatocytes. Conclusions: We have identified a novel immune-sensing mechanisms in virus-infected hepatocytes that links effector molecules generated by virus-specific T cells to cell-autonomous induction of death selectively in virus-infected hepatocytes.

391 PRE-CLINICAL PROOF-OF-CONCEPT STUDIES EXPLORING SCHEDULES OF ADMINISTRATION OF AN ADENOVIRUSBASED HBV IMMUNOTHERAPEUTIC SHOW WIDE POTENTIAL FOR INDUCTION OF ROBUST AND LONG-LASTING T-CELL RESPONSES H. Boukhebza, C. Dubois, Y. Schlesinger, V. Koerper, R. Brandely, M. Geist, T. Menguy, N. Silvestre, R. Schirmbeck, G. Inchauspe, P. Martin. Infectious Diseases Department, TRANSGENE SA, Lyon, Molecular Immunology Department, TRANSGENE SA, Illkirch-Graffenstaden, France; Ulm University Hospital, Ulm, Germany E-mail: perrine.martin@transgene.fr

P =0.0049; A vs C P < 0.0001; B vs C P =0.0001). Forty seven percent of patients in group A and B were HLA-A2 positive. Tim-3/PD-1 HBV-specific CD8 T cells were 61.95% (median, range 18.7%-95.5%), Tim-3/PD-1 were 3.135% (median, range 0.00–43.6%) and Tim-3/PD-1 were 16.6% (median, range 3.37%70.2%). The frequency of Tm-3/PD-1 HBV-specific CD8 T cells in ACLF (69.1%±17.71%) were significantly higher than that in CHB (56.33%±19.74%, P =0.0112). The level of IFN-g in PBMC culture medium had no statistical differences in ACLF (median 306.1 pg/ml) and CHB (median 302.1 pg/ml). Conclusions: Tim-3 and PD-1 expressions were significantly upregulated in patients with HBV infection, especially in ACLF patients. The majority of HBV-specific CD8 T cells coexpressed Tim-3 and PD-1, which may be play an important role in HBV infection persistent and pathogenesis of liver damage in patients with HBV chronic infection.

We investigated the prevalence of neutralizing antibodies (NA) to human Adenovirus (Ad) 5 both in healthy subjects (HS) and Chronic Hepatitis B (CHB) patients in Shanghai. Detection of anti-Ad5 NA (percentage of detection and titers) was similar between HS and CHB patients. A high percentage of subjects harbored no detectable antibodies (32.2 %) while proportion of subjects displaying very high antibody titers was low (4 %). Neither demographic factors (gender, age, health) nor AST/ALT or HBV circulating DNA titers affected detection of Ad5-specific NA. These observations pave the ground for development of Ad5-based immunotherapeutics aiming at treating CHB patients in China.