Durable Immune Responses Research Articles

Recent Advances and Methodological Considerations on Vaccine Candidates for Human Schistosomiasis.

Schistosomiasis remains a neglected tropical disease of major public health concern with high levels of morbidity in various parts of the world. Although considerable efforts in implementing mass drug administration programs utilizing praziquantel have been deployed, schistosomiasis is still not contained. A vaccine may therefore be an essential part of multifaceted prevention control efforts. In the 1990s, a joint United Nations committee promoting parasite vaccines shortlisted promising candidates including for schistosomiasis discussed below. After examining the complexity of immune responses in human hosts infected with schistosomes, we review and discuss the antigen design and preclinical and clinical development of the four leading vaccine candidates: Sm-TSP-2 in Phase 1b/2b, Sm14 in Phase 2a/2b, Sm-p80 in Phase 1 preparation, and Sh28GST in Phase 3. Our assessment of currently leading vaccine candidates revealed some methodological issues that preclude a fair comparison between candidates and the rationale to advance in clinical development. These include (1) variability in animal models - in particular non-human primate studies - and predictive values of each for protection in humans; (2) lack of consensus on the assessment of parasitological and immunological parameters; (3) absence of reliable surrogate markers of protection; (4) lack of well-designed parasitological and immunological natural history studies in the context of mass drug administration with praziquantel. The controlled human infection model - while promising and unique - requires validation against efficacy outcomes in endemic settings. Further research is also needed on the impact of advanced adjuvants targeting specific parts of the innate immune system that may induce potent, protective and durable immune responses with the ultimate goal of achieving meaningful worm reduction.

Hydrogel/nanoadjuvant-mediated combined cell vaccines for cancer immunotherapy

Combined cell vaccines of tumor whole cells and dendritic cells (DCs) provide an effective individualized immunotherapy for malignant tumors. We propose an innovative strategy termed “biomaterial-mediated combined cell vaccines for immunotherapy,” which combines tumor cell and DC vaccines with a cyclodextrin-polyethylene glycol hydrogel and a cytosine-phosphate-guanine (CpG) nanoadjuvant. The nanoadjuvant promotes antigen presentation and amplifies immune-eliciting potency by co-delivery of antigens and adjuvants. The hydrogel scaffold provides a better growth microenvironment for injected exogenous DCs and recruits endogenous DCs to maintain their viability for synergistic effect. The results indicated that, relative to live tumor cells, the immunogenically dying tumor cells activated DC maturation effectively with the auxiliary effect of immune adjuvant CpG nanoparticles. The increased T cell percentage, proliferation ability, cytokine secretion, and cytotoxic effect revealed the enhanced immunogenicity of the combined cell vaccines. The combined hydrogel/nanoadjuvant system showed the best efficiency in inhibiting tumor growth. Moreover, vaccination with a single dose of hydrogel-based combined vaccines significantly delayed the development of tumors. The biomaterial-mediated combined cell vaccines remarkably increased the infiltration of effector T cells, alleviated the intratumoral immunosuppressive microenvironment, and maximized the immune effect of the vaccines, thus improving cancer immunotherapy. Statement of significanceCell-based vaccines, including tumor whole-cell vaccine or DC vaccine, have attracted wide attention as an effective method for cancer immunotherapy. However, it is difficult to gain satisfactory outcomes in clinical trials because of the low immunogenicity of tumor whole cell vaccine and the short-term survival of transferred DC vaccine. Therefore, improving the ability of cell-based vaccines to induce a strong and durable immune response is the primary objective for vaccine development. Biomaterial-mediated combined cell vaccines is an innovative strategy for cancer immunotherapy. The combined hydrogel/ nanoadjuvant system comprises immunogenically dying tumor cells, DCs, and nanoadjuvants. Nanoadjuvant-loaded immunogenically dying tumor cells can induce efficient immune response as the tumor cell vaccine. The hydrogel-based combined tumor cell/DC vaccine could be used for individualized immunotherapy.

Multistage Cooperative Nanodrug Combined with PD-L1 for Enhancing Antitumor Chemoimmunotherapy.

Combinatorial CpG oligonucleotide (CPG) and chemotherapy drug represent a promising approach to reactivate immune system. However, these two agents possess different physicochemical properties, hindering the application of direct self-assembly of these two cargos into a single nanostructure. Here, a multistage cooperative nanodrug is developed by the direct self-assembly of cis-platinum (CDDP, Pt), l-arginine (l-Arg, R), and CPG (defined as PtR/CPG) for antitumor chemoimmunotherapy. First, the CDDP can induce cell apoptosis. Meanwhile, CDDP also promotes the production of H2 O2 , catalyzing the conversion of l-Arg into nitric oxide (NO). The generated NO decreases the multidrug resistance of cells toward CDDP. Thus, the synergistic effects of CDDP and NO can trigger immunogenic cell death to produce tumor-associated antigens (TAAs). The TAAs and CPG will induce the maturation of dendritic cells (DCs) and enhance antigen presentation ability of DCs. In this way, the PtR/CPG can reverse the immunosuppressive microenvironment, sensitizing tumors to immune checkpoint inhibitors mediated by the programmed death-ligand 1 (PD-L1) antibody. Furthermore, the PtR/CPG combined with the PD-L1 antibody decreases the exhaustion and dysfunction of cytotoxic T lymphocytes to elicit durable systemic immune response. As a result, the prepared PtR/CPG nanodrug in combination with PD-L1 may be highly significant for cancer immunotherapy.

Hydrogel-By-Design: Smart Delivery System for Cancer Immunotherapy.

Immunotherapy has emerged as a promising strategy for cancer treatment, in which durable immune responses were generated in patients with malignant tumors. In the past decade, biomaterials have played vital roles as smart drug delivery systems for cancer immunotherapy to achieve both enhanced therapeutic benefits and reduced side effects. Hydrogels as one of the most biocompatible and versatile biomaterials have been widely applied in localized drug delivery systems due to their unique properties, such as loadable, implantable, injectable, degradable and stimulus responsible. Herein, we have briefly summarized the recent advances on hydrogel-by-design delivery systems including the design of hydrogels and their applications for delivering of immunomodulatory molecules (e.g., cytokine, adjuvant, checkpoint inhibitor, antigen), immune cells and environmental regulatory substances in cancer immunotherapy. We have also discussed the challenges and future perspectives of hydrogels in the development of cancer immunotherapy for precision medicine at the end.

Solid stress impairs lymphocyte infiltration into lymph-node metastases.

Strong and durable anticancer immune responses are associated with the generation of activated cancer-specific T cells in the draining lymph nodes. However, cancer cells can colonize lymph nodes and drive tumour progression. Here, we show that lymphocytes fail to penetrate metastatic lesions in lymph nodes. In tissue from patients with breast, colon, and head and neck cancers, as well as in mice with spontaneously developing breast-cancer lymph-node metastases, we found that lymphocyte exclusion from nodal lesions is associated with the presence of solid stress caused by lesion growth, that solid stress induces reductions in the number of functional high endothelial venules in the nodes, and that relieving solid stress in the mice increased the presence of lymphocytes in lymph-node lesions by about 15-fold. Solid-stress-mediated impairment of lymphocyte infiltration into lymph-node metastases suggests a therapeutic route for overcoming T-cell exclusion during immunotherapy.

Abstract 524: The novel STING agonist VB-85247 induces robust durable antitumor immune responses by intravesical administration in a non-muscle invasive bladder cancer model

Abstract Introduction: Bacillus Calmette-Guerin (BCG) unresponsive non-muscle invasive bladder cancer (NMIBC) patients are in great need of effective immunotherapies. STING (Stimulator of Interferon Genes) plays a central role in mounting innate and adaptive immune responses to tumor cells. Activation of the STING pathway leads to the induction of inflammatory cytokines (IFN-α/β, TNF-α, IL-6 and CXCL10), maturation and activation of dendritic cells (DC), and induction of anti-tumor T cells. Our group has developed a novel STING agonist, VB-85247. Here we use a murine NMIBC model to report the potent antitumor effect of VB-85247 compared to standard of care BCG and anti-PD1 checkpoint inhibitor therapy currently used in the management of NMIBC. Methods: We developed a mouse model of Non-Muscle Invasive Bladder Cancer (NMIBC) utilizing orthotopically implanted MB49-Luc cells, permitting BLI (Bioluminescence) measurement of tumor growth by In Vivo Imaging Systems (IVIS). Results: VB-85247 was found to bind to mouse STING and all major variants of human STING protein. VB-85247 induced high levels of IFN-β and other cytokines across cells from different species, including primary human bladder epithelial cells. VB-85247 treatment by intravesical instillation in the mouse model of NMIBC resulted in dose dependent tumor regression starting after the first treatment, achieving up to a 100% complete response rate at the 40 µg dose level after 5 weekly treatments. The treatment was well tolerated, eliciting strong and durable anti-tumor immune responses without any mortality. All cured mice rejected a re-challenge with MB49-Luc cells with no further treatment, demonstrating long-lasting anti-tumor immunity. By contrast, BCG treatment in the same model was not efficacious. Combination with anti-PD1 treatment reduced the dose of VB-85247 needed to achieve 100% complete responses to 20 µg, whereas anti-PD1 treatment alone resulted in only 25% complete responses. In addition, a single dose of 40 µg VB-85247 by bladder instillation in the NMIBC model induced systemic immune responses including serum cytokines demonstrating Type I IFN responses plus DC mobilization and activation in the blood, draining lymph nodes, and spleen within 24 hours. Conclusions: The STING agonist VB-85247 was well tolerated and displayed robust efficacy by bladder instillation in a mouse orthotopic tumor model of NMIBC, achieving up to 100% complete responses. All cured mice rejected fresh inoculations of tumor cells with no further treatment, demonstrating induction of immunologic memory. Treatment with BCG was not efficacious in the model. These results suggest the potential utility of the VB-85247 STING agonist in the treatment of BCG unresponsive NMIBC patients. Based on these data, VB-85247 is being advanced to clinical development. Citation Format: Miglena Prabagar, Venu Bommireddy, Rachael Siegel, Haihua Zheng, Lee Pellegrino, Stanley Nawoschik, Albert Uveges, Steven Paget, Ku Lu, Krista Saufler, Axel Metzger, David Diller, Jason Trama, Grant Gallagher, Chia-Yu Huang, Brian McGuinness, James R. Beasley, Michael McQueney, Martin Adelson, Gary L. Schieven, Eli Mordechai, Rukiye-Nazan Eraslan. The novel STING agonist VB-85247 induces robust durable antitumor immune responses by intravesical administration in a non-muscle invasive bladder cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 524.

CD137 and PD-L1 targeting with immunovirotherapy induces a potent and durable antitumor immune response in glioblastoma models

BackgroundGlioblastoma (GBM) is a devastating primary brain tumor with a highly immunosuppressive tumor microenvironment, and treatment with oncolytic viruses (OVs) has emerged as a promising strategy for these tumors. Our...

Abstract 2788: Deep characterization of tumor infiltrating leukocytes using a combination of flow cytometry and single-cell multiomics

Abstract Cancer immunotherapies have the potential to induce durable anti-tumor immune responses; however the efficacy of these treatments varies among patients and partially depends on the complex interplay between malignant cells and non-malignant cells within the tumor microenvironment. In the tumor microenvironment, T cells play a crucial role in eliminating tumor cells and orchestrating anti-tumor immune responses; in contrast immunosuppressive cell types such as myeloid-derived suppressor cells can support tumor progression. Here we harnessed recent advances in single-cell multiomics that allow high-resolution functional characterization of intratumoral immune cells to improve our understanding of their dynamic relationships. Specifically, we utilized a One Solution Workflow to dissociate a solid tumor followed by in-depth dissection of the immune composition of the tumor microenvironment using both flow cytometry and the BD Rhapsody™ Single-Cell Analysis System. We characterized the cellular composition of tumor microenvironment using flow cytometry analysis. Importantly, by examining the expression of mRNA and surface protein markers at single-cell resolution, we unraveled the complexities of the tumor microenvironment, elucidated cellular heterogeneity and identified cell-type specific gene signatures. We propose this One Solution Workflow can be adopted to understand the transcriptional and proteomic phenotypes of tumor infiltrating leukocytes for development of novel immune therapeutic strategies for cancer. For Research Use Only. Not for use in diagnostic or therapeutic procedures. Class 1 Laser Product.BD-23279 (v1.0) 1120BD, the BD Logo and Rhapsody are trademarks of Becton, Dickinson and Company or its affiliates. © 2020 BD. All rights reserved. Citation Format: Xiaoshan Shi, Margaret Nakamoto, Aaron Middlebrook, Wei Huang, Evelyn Lo, Patrick T. Neuhoefer, Scott Bornheimer, Smita Ghanekar. Deep characterization of tumor infiltrating leukocytes using a combination of flow cytometry and single-cell multiomics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2788.

Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells

SummaryEnding the COVID-19 pandemic will require long-lived immunity to SARS-CoV-2. Here, we evaluate 254 COVID-19 patients longitudinally up to 8 months and find durable broad-based immune responses. SARS-CoV-2 spike binding and neutralizing antibodies exhibit a bi-phasic decay with an extended half-life of >200 days suggesting the generation of longer-lived plasma cells. SARS-CoV-2 infection also boosts antibody titers to SARS-CoV-1 and common betacoronaviruses. In addition, spike-specific IgG+ memory B cells persist, which bodes well for a rapid antibody response upon virus re-exposure or vaccination. Virus-specific CD4+ and CD8+ T cells are polyfunctional and maintained with an estimated half-life of 200 days. Interestingly, CD4+ T cell responses equally target several SARS-CoV-2 proteins, whereas the CD8+ T cell responses preferentially target the nucleoprotein, highlighting the potential importance of including the nucleoprotein in future vaccines. Taken together, these results suggest that broad and effective immunity may persist long-term in recovered COVID-19 patients.

Severe Sepsis As Immune Stimulation and Protection from Relapse of Childhood Acute Lymphoblastic Leukemia (ALL): Results from a Pilot Study and Validation of Events in a National Administrative Dataset

Relapse remains the major clinical risk in children with ALL, and those with persistent minimal residual disease (MRD) after chemotherapy pose a particular therapeutic challenge given their chemoresistant cell population. We previously showed TLR agonists, an immune-stimulating drug class, generate durable memory immune responses against ALL cells in preclinical MRD models (Blood 2009; 114:2459). These drugs mimic the “danger” signal provided by severe sepsis/septic shock (SS) and may offer immunotherapeutic options for patients who fail or are not eligible for targeted immunotherapies. Demonstrating a protective effect of SS against ALL relapse would further support clinical development of TLR agonists. We hypothesize SS but not SIRS/sepsis (SIRS) will be associated with a decreased risk of ALL relapse, and this effect will be most pronounced in children with NCI high-risk (NCI-HR) disease who are more likely to have both SS exposures and relapses.We assembled and validated a cohort of over 13,000 children with newly diagnosed ALL using the Pediatric Health Information System (PHIS) database. SS exposures after start of induction chemotherapy were defined using ICD9 (NEJM 2003; 348:1546) and billing codes for blood cultures and resources indicating organ failures. ICD9 and pharmaceutical/procedure billing codes were also used to identify ALL relapses and blood/marrow transplantations (BMT). To determine the operating characteristics of these definitions of SS, relapse and BMT, we established a cohort of children from the Children's Hospital of Philadelphia (CHOP) including all patients diagnosed with ALL at CHOP from January 1, 2004 - December 31, 2013. Patients initially treated elsewhere or who left CHOP prior to the end of induction were excluded. Exposures and outcomes identified by manual chart review were considered the gold standard. Exposures were classified as SS or SIRS per the 2005 International Pediatric Sepsis Consensus Guidelines (Ped Crit Care Med 2005; 6:2) and documented until the first event or 3 years from diagnosis. Relapses and deaths were captured until 5 years from diagnosis. Patients were censored at BMT in first remission. We analyzed the data in this single-institution cohort as a pilot study to determine whether the effect of SS on relapse is in the direction we hypothesize. Demographics were evaluated using one-way ANOVA and chi-square. Cox regressions with time-dependent exposures were used to estimate hazard ratios (HR) for relapse by exposure: SS versus no SS, and any sepsis (SIRS + SS) versus none. We also present validation results for the identification of relapses and BMT in the PHIS cohort.Among 395 eligible CHOP patients with newly diagnosed ALL, there were 1736 total exposures (SIRS n=1696 and SS n=40). Demographics are presented in Table 1. SS occurred in 35 patients, SIRS was the maximum exposure in 318, and no sepsis was observed in 42. Exposure was associated with age and phenotype/NCI risk status. Median follow-up was 1826 days (IQR 28-1826), and median time to first SS 117 days (IQR 53-356). There were 521 organisms documented during sepsis episodes (Table 2). BMT in CR1 was the first event in 22 patients (5.6%) at median 174 days from diagnosis (IQR 143-240), relapse in 47 (11.9%; 580 days, 260-1106), and remission death in 5 (1.3%; median 252 days, 98-348). Unadjusted analysis showed a detrimental effect of SS on relapse (HR 2.45; 95%CI 1.04, 5.79). Adjusting for NCI-HR decreased the SS effect size (HR 1.74; 0.7, 4.29), and limiting to NCI-HR patients shifted the effect into a protective direction (crude HR 0.71; 0.09, 5.43). Any sepsis was not protective in any analysis (crude HR 1.86; 0.66, 5.25; adjusted HR 1.71; 0.61, 4.81; NCI-HR-only HR 2.47; 0.32, 19.1). Our relapse identification method within the national PHIS cohort had sensitivity 76% and positive predictive value (PPV) 91%, while BMT identification sensitivity was 93% and PPV 100%.Our CHOP pilot study demonstrated a detrimental effect of SS on the cohort as a whole, suggesting most children with ALL incur more risk than benefit from SS exposure; however, the hazard ratio for SS is in the direction of protection in the NCI-HR group. We have validated our approach to identifying relapse and BMT in PHIS and are validating our method to detect SS exposures in PHIS. Evaluation of the association between SS and relapse risk in the larger, multi-institutional PHIS cohort will provide more precise effect estimates. [Display omitted] DisclosuresFisher:Merck: Research Funding; Pfizer: Research Funding.

Anaphylaxis to the first dose of mRNA SARS‐CoV‐2 vaccines: Don't give up on the second dose!

Anaphylaxis to the first dose of mRNA SARS‐CoV‐2 vaccines: Don't give up on the second dose!

Fabrication and Characterization of a Biomaterial Based on Extracellular-Vesicle Functionalized Graphene Oxide

Mesenchymal stem cell (MSC) derived extracellular vesicles (EV) are emerging as acellular therapeutics for solid organ injury and as carriers for drug delivery. Graphene-based materials are novel two-dimensional crystal structure-based materials with unique characteristics of stiffness, strength and elasticity that are being explored for various structural and biological applications. We fabricated a biomaterial that would capture desirable properties of both graphene and stem cell derived EV. Metabolically engineered EV that express azide groups were cross-linked with alkyne-functionalized graphene oxide (GO) via a copper catalyzed alkyne-azide cycloaddition (CuAAC) reaction. The crosslinking between EV and GO was accomplished without the need for ligand expression on the metal. Scanning electron and fluorescence microscopy demonstrated excellent cross-linking between EV and GO. Biological effects were assessed by phagocytosis studies and cell viability studies. The uptake of GO or sonicated GO (sGO) resulted in a durable pro-inflammatory immune response. Cell studies further showed that crosslinked GO-EV scaffolds exhibited cell-type dependent cytotoxicity on liver cancer cells whereas there was minimal impact on healthy hepatocyte proliferation. In vitro, neither GO-EV nor sGO-EV induced DNA strand breaks. In vivo studies in zebrafish revealed gross developmental malformations but treatment-induced mortality was only seen with the highest doses of GO-EV and sGO-EV. With these advantages, this engineered biomaterial combining the versatility of graphene with the therapeutic effects of MSC-EV has potential for applications in tissue engineering and regenerative medicine.

IMPAIRED HUMORAL RESPONSE IN LYMPHOMA PATIENTS SURVIVING THE ACUTE PHASE OF COVID‐19

Introduction: The ability to generate an adequate and durable immune response to SARS-CoV-2 in B-cell lymphoma patients (pts) treated with immunochemotherapy is still unclear. We monitored antibody levels during convalescence in COVID-19 survivors with lymphoma, compared to other hematologic diseases (HemD) and healthy controls (Ctrls). Methods: Seventeen pts with non-Hodgkin lymphoma (NHL) [follicular (FL): 9; diffuse large B-cell (DLBCL): 8] surviving the acute phase of virologic-proven COVID-19 were evaluated at 3 timepoints (TP) after nasal swab negativity: +1 (TP1), +3 (TP3), and +6 (TP6) months; 28 pts affected by HemD (10 multiple myeloma, 8 chronic lymphoproliferative disorders, 10 myelodysplastic/chronic myeloproliferative syndromes) and 17 Ctrls were also evaluated at the same TP. Antibody (Ab) levels to nucleocapsid (N-Ab) and spike (S-Ab) virus proteins were measured using a highly sensitive luciferase-immunoprecipitation system (LIPS) assay. Positive levels were 125000 LU for N-Ab and 45000 LU for S-Ab. Results: Mean N- and S-Ab levels were lower in FL and DLBCL than in other HemD pts, both at TP1 (N-Ab 1217517 vs 2205610 LU, p = 0.03; S-Ab 580444 vs 1184453 LU, p = 0.049) and at TP3 (N-Ab 850510 vs 2094487 LU p = 0.012, S-Ab 605284 vs 1230946 LU, p = 0.074). At TP6 N-Ab levels declined in all subgroups, while S-Ab levels remained stable. At TP1, compared to HemD, significantly less FL and DLCBL pts reached positive levels of N-Ab (93% vs 59% p = 0.017) and of S-Ab (86% vs 47%; P: 0.008). Positive levels of N-Ab and S-Ab were also more frequent in Ctrls (100% and 87%; p = 0.007 and 0.028) than in NHL pts. Rates of seroprotection remained lower in NHL pts also at TP3 and TP6. Rituximab (RTX) had been given to 14/17 NHL pts, either ≥6 months in 5 (prior RTX) or <6 months in 9 pts (ongoing RTX) before Covid-19 diagnosis. Ongoing RTX had a markedly negative effect on S-Ab levels since none of 9 patients seroconverted at TP1 compared to 5/5 prior RTX pts (P = 0.0005). No changes occurred in the rate of seroprotected pts also at TP3 and TP6 except for 1 ongoing RTX pt who reached protective levels at TP6 (see figure). Overall seroprotective Ab at any TP were present in 2 of 18 determinations in ongoing RTX pts, despite RTX treatment discontinuation, and in 15 of 15 determination in prior RTX pts (p = 0.0001). Keywords: Aggressive B-cell non-Hodgkin lymphoma, Indolent non-Hodgkin lymphoma No conflicts of interests pertinent to the abstract.

Aqueous extracts from cultivated Cistanche deserticola Y.C. Ma as polysaccharide adjuvant promote immune responses via facilitating dendritic cell activation

Ethnopharmacological relevanceHerbal polysaccharides have exhibited great immune-enhancing potential. Adjuvants are a key tool for developing efficacious vaccines. In our previous study, a water-soluble polysaccharide extracted from wild Cistanche deserticola Y.C. Ma showed potent immunostimulatory activity. Aim of studyIn this study, the immune profiles and efficacy of aqueous extracts of cultivated Cistanche deserticola Y.C. Ma (AECCD) on ICR mice against ovalbumin (OVA) were investigated. In vitro experiments, the possible DC activation mechanism by AECCD was evaluated. Materials and methodsAECCD were extracted using hot water after which the crude polysaccharides were precipitated by ethanol. Mice were firstly immunized subcutaneously with OVA (10 μg per mouse) alone or OVA (10 μg per mouse) respectively containing different dose of AECCD (200, 400 and 800 μg per mouse) on Days 1 and 14 and the magnitude and kinetics of antibodies and cell-mediated responses were then assessed. ResultsAECCD elicited vigorous and long-term IgG responses with mixed Th1/Th2 responses and up-regulated levels of Th-associated cytokines (CD4+IL-4, CD4+IFN-γ and CD8+IFN-γ). Moreover, AECCD induced the strong cellular immune response characterized by increased splenocyte proliferation as well as the activated T cell response. Notably, AECCD significantly enhanced the maturation of dendritic cells (DCs) and inhibited Tregs. In vitro experiments, Preliminary tests indicated that AECCD induced DC activation by promoting phenotypic maturation, cytokine section and allostimulatory activity. Toll-like receptor 4 (TLR4) was an essential receptor for DCs to directly bind AECCD. The inhibitors of NF-κB decreased the expression levels of CD40, CD80, CD86 and MHC-II and the production of IFN-γ, TNF-α and IL-6 through DCs. ConclusionsFinally, these findings suggested that AECCD could elicit potent and durable antigen specific immune responses through DC activation, which was involved in the regulation of maturation markers and cytokine expression via TLR4-related NF-κB pathway. The study indicates that AECCD is a potential immunomodulator.

Sendai Virus-Vectored Vaccines That Express Envelope Glycoproteins of Respiratory Viruses.

Human respiratory syncytial virus (HRSV), human metapneumovirus (HMPV), and human parainfluenza viruses (HPIVs) are leading causes of respiratory disease in young children, the elderly, and individuals of all ages with immunosuppression. Vaccination strategies against these pneumoviruses and paramyxoviruses are vast in number, yet no licensed vaccines are available. Here, we review development of Sendai virus (SeV), a versatile pediatric vaccine that can (a) serve as a Jennerian vaccine against HPIV1, (b) serve as a recombinant vaccine against HRSV, HPIV2, HPIV3, and HMPV, (c) accommodate foreign genes for viral glycoproteins in multiple intergenic positions, (d) induce durable, mucosal, B-cell, and T-cell immune responses without enhanced immunopathology, (e) protect cotton rats, African green monkeys, and chimpanzees from infection, and (f) be formulated into a vaccine cocktail. Clinical phase I safety trials of SeV have been completed in adults and 3–6-year-old children. Clinical testing of SeVRSV, an HRSV fusion (F) glycoprotein gene recombinant, has also been completed in adults. Positive results from these studies, and collaborative efforts with the National Institutes of Health and the Serum Institute of India assist advanced development of SeV-based vaccines. Prospects are now good for vaccine successes in infants and consequent protection against serious viral disease.

P362 Longitudinal antibody response to SARS-CoV-2 infection and antibody responses to COVID-19 vaccination in Inflammatory Bowel Disease patients receiving biologics

BackgroundGiven that IBD patients were excluded from COVID-19 vaccine trials, there is a lack of vaccine efficacy data in this population. In this study, we evaluated longitudinal serological responses to SARS-CoV-2 infection as well as to COVID-19 vaccination in IBD patients.MethodsWe collected clinical data and sera from IBD patients enrolled in an observational SARS-CoV-2 sero-surveillance study at our large hospital center in New York City during routine infusions and clinic visits. To distinguish between infection and vaccination, sera was collected prior to vaccination where possible, and all sera was tested for both antibodies to SARS-CoV-2-specific RBD, the target of current available vaccines in the U.S., and nucleocapsid proteins.ResultsOur results reveal waning antibody titres in 13 of 16 (81%) patients infected with SARS-CoV-2 over a course of 6-7 months. Of 48 vaccinated patients, 16 patients completed vaccine schedules with two doses, and all 16 (100%) achieved seroconversion above the threshold required for convalescent plasma donation.ConclusionWhile antibody responses to infection in IBD patients have questionable stability, completion of the COVID-19 vaccine series in IBD patients results in robust serological responses. To our knowledge is the first data confirming adequate serological responses to COVID-19 vaccination in IBD patients with and without biologic medications. Studies are needed to assess adequacy of dosing schedules, medication effects, measurement of cell-mediated responses, durability of immune responses, and clinical efficacy of COVID-19 vaccines in IBD patients.

Enhancement of the Tolerogenic Phenotype in the Liver by ImmTOR Nanoparticles.

ImmTOR biodegradable nanoparticles encapsulating rapamycin have been shown to induce a durable tolerogenic immune response to co-administered biologics and gene therapy vectors. Prior mechanism of action studies have demonstrated selective biodistribution of ImmTOR to the spleen and liver following intravenous (IV) administration. In the spleen, ImmTOR has been shown to induce tolerogenic dendritic cells and antigen-specific regulatory T cells and inhibit antigen-specific B cell activation. Splenectomy of mice resulted in partial but incomplete abrogation of the tolerogenic immune response induced by ImmTOR. Here we investigated the ability of ImmTOR to enhance the tolerogenic environment in the liver. All the major resident populations of liver cells, including liver sinusoidal endothelial cells (LSECs), Kupffer cells (KC), stellate cells (SC), and hepatocytes, actively took up fluorescent-labeled ImmTOR particles, which resulted in downregulation of MHC class II and co-stimulatory molecules and upregulation of the PD-L1 checkpoint molecule. The LSEC, known to play an important role in hepatic tolerance induction, emerged as a key target cell for ImmTOR. LSEC isolated from ImmTOR treated mice inhibited antigen-specific activation of ovalbumin-specific OT-II T cells. The tolerogenic environment led to a multi-pronged modulation of hepatic T cell populations, resulting in an increase in T cells with a regulatory phenotype, upregulation of PD-1 on CD4+ and CD8+ T cells, and the emergence of a large population of CD4–CD8– (double negative) T cells. ImmTOR treatment protected mice in a concanavalin A-induced model of acute hepatitis, as evidenced by reduced production of inflammatory cytokines, infiltrate of activated leukocytes, and tissue necrosis. Modulation of T cell phenotype was seen to a lesser extent after administration by empty nanoparticles, but not free rapamycin. The upregulation of PD-1, but not the appearance of double negative T cells, was inhibited by antibodies against PD-L1 or CTLA-4. These results suggest that the liver may contribute to the tolerogenic properties of ImmTOR treatment.

Preliminary results from a phase 1/2 study of BDC-1001, a novel HER2 targeting TLR7/8 immune-stimulating antibody conjugate (ISAC), in patients (pts) with advanced HER2-expressing solid tumors.

2549 Background: BDC-1001 is a novel ISAC consisting of an investigational trastuzumab biosimilar chemically conjugated to a TLR 7/8 agonist with a non-cleavable linker. BDC-1001 was designed to activate the innate immune system, eliciting antibody-mediated effector functions (eg, antibody-dependent cellular phagocytosis) and a durable adaptive immune response. In preclinical tumor models resistant to anti-HER2 treatments, BDC-1001 demonstrated potent and durable immune-mediated antitumor efficacy. Methods: A 4-part, phase 1/2 dose-escalation/expansion study was initiated to evaluate BDC-1001 ± PD1 inhibitor pembrolizumab in pts with HER2-expressing solid tumors who had progressive disease on standard of care (NCT04278144). Preliminary results of the monotherapy dose escalation (Part 1) are reported. Pts with advanced metastatic HER2-expressing (IHC2/3+) or amplified solid tumors received BDC-1001 IV q3w in a 3+3 design w/ 12 pts/cohort backfill allowed. Primary objectives were to evaluate safety, tolerability, dose-limiting toxicities (DLTs) and determine a phase 2 dose; secondary objectives were to assess pharmacokinetics (PK), pharmacodynamics and preliminary anti-tumor activity. Results: As of Jan 29, 2021, 20 pts w/ a median age of 65 (46-85) have enrolled in 4 dose levels (0.15mg/kg to 5 mg/kg). Cancer types include breast, biliary, cervical, colorectal (CRC), lung, gastroesophageal, salivary, urinary tract and endometrial. Pts had received a median of 4 (1-7) prior therapies; 65% received &gt;1 prior anti-HER2 therapy. All pts completed the 21-day DLT period; no DLTs or drug-related serious adverse events (AEs) have been observed. AEs deemed related to BDC-1001 have been mild to moderate including infusion-related reactions. The MTD has not been reached (treatment duration 5-17+wk); enrollment is ongoing. PK evaluations showed Cmax levels consistent with predicted modeling based on non-human primates (NHP). One pt with microsatellite stable (MSS) HER2+ CRC with lung metastases had a confirmed partial response after 4 cycles and remains on study; 2 additional pts with metastatic MSS HER2+ CRC had stable disease (SD) and a pt with heavily pretreated MSS endometrial cancer with lung metastases had confirmed SD and remains on treatment 17+ wk; 3 of these pts had received 2 prior anti-HER2 therapies. Conclusions: In this first-in-human study, BDC-1001 appears to be well-tolerated up to the dose tested to date (5 mg/kg), with Cmax levels achieved as predicted by NHP modeling. Evidence of clinical activity have been observed, including in pts previously treated with anti-HER2 therapy. Dose escalation is ongoing and will be followed by combination dosing with CPI and the phase 2 component in selected tumors. Clinical trial information: NCT04278144.

Dendritic cell vaccine (DCVAC) combined with chemotherapy (CMT) in patients with newly diagnosed epithelial ovarian carcinoma (EOC) after primary debulking surgery (PDS): Biomarker exploratory analysis of a phase 2, open-label, randomized, multicenter trial.

5521 Background: Most patients with EOC relapse despite PDS and CMT. Autologous DCVAC can present tumor antigens to elicit a durable immune response. We hypothesized that adding DCVAC to CMT stimulates antitumor immunity and improves clinical outcomes. Methods: Key eligibility criteria were FIGO stage III EOC (serous, endometrioid, or mucinous), post-PDS with &lt; 1 cm maximal residuum, no prior systemic therapy, and ECOG 0-2. In part 1, patients were randomized up to 6 weeks after PDS, 1:1:1, into arm A (A; DCVAC concomitant with CMT), arm B (B; DCVAC sequential after CMT), and arm C (C; CMT). Patients were stratified by tumor residuum (0 or &lt; 1 cm). CMT consisted of 6 cycles of carboplatin (AUC 5-7) and paclitaxel (175 mg/m2). Patients in A and B received up to 10 doses of DCVAC (1×107 DCs/dose). The primary endpoint was radiologically assessed progression-free survival (PFS). The key secondary endpoint was overall survival (OS). Results presented refer to a protocol-defined modified intention-to-treat population (mITT) including patients who received ≥1 CMT dose in C or ≥1 DCVAC dose in A and B. Results: Between November 2013 and March 2016, 99 patients were randomized. At the final analysis, the mITT included 31 patients in A, 29 patients in B, and 30 patients in C. Key baseline characteristics and DCVAC exposure were comparable across treatment arms. Median PFS was 20.3 months in A, not reached in B, and 21.4 months in C, with corresponding HRs (95% CI) compared to C of 0.98 (0.48-2.00) in A and 0.39 (0.16-0.96) in B. The PFS benefit in B was statistically significant (p = 0.034) This was supported by a non-significant trend in OS in A and B. Median OS was not reached in any arm at the time of median follow-up of 66 months (34% of events). Patients with low CD8+ T-cell counts (CD8Lo) in tumor samples in A and B had significantly improved clinical outcomes compared to patients in C with CD8Lo: median PFS gain of 6 months (19 vs 13 months) and a more robust OS gain (median not reached vs 31 months), with minimal difference between A and B. This effect could not be attributed to statistical differences in high CD8+ T-cell counts (CD8Hi) density patients. These findings indicated the best clinical outcome in DCVAC patients with immunologically “cold” tumors in both DCVAC arms. DCVAC showed a good safety profile with only 8 DCVAC-related adverse events (Grade 1-2). Conclusions: DCVAC improved PFS and OS outcomes in patients with newly diagnosed EOC, predominantly in patients with immunologically “cold” tumors, thus representing a promising treatment option in this patient population. Clinical trial information: NCT02107937.

MDNA11 is a long-acting IL-2 superkine that potentiates durable immune response in mouse tumor models and non-human primates.

e14546 Background: The efficacy and safety of recombinant human IL-2 (rhIL-2; Proleukin) to treat certain cancers is limited by a short half-life, marked toxicity and selective high affinity binding to IL2Ra over IL2Rb, resulting in preferential activation of suppressive Tregs. In contrast, MDNA11 has been engineered as a long-acting IL-2 superkine with high affinity IL2Rb receptor selectivity, resulting in preferential anti-cancer effector immune cell activation. Methods: MDNA11 was characterized in both in vitro and in vivo studies including assessment of receptor binding kinetics using BLI/Octet, receptor-mediated signaling in human PMBCs, efficacy in syngeneic mouse tumor models including memory response, as well as safety and PK/PD assessments in non-human primates (NHP). Results: Unlike rhIL-2, MDNA11 does not bind to human IL2Ra but demonstrates a 30-fold higher affinity binding to human IL2Rb. This selectivity resulted in enhanced in vitro STAT5 signaling in human NK and resting CD8 T cells with diminished signaling in Tregs; validation studies in humanized mice are ongoing. In CT26 and MC38 syngeneic tumor models, MDNA11 demonstrates potent and durable efficacy as monotherapy following a Q1W dose schedule for 2 weeks. Synergy with anti-PD1 and anti-CTLA4 immune checkpoint inhibitors (ICIs) was observed and a robust immune memory response developed in all mice with complete tumor clearance. These mice were protected against relapse and tumor re-challenges for up to 8 months without any further treatment, and showed the presence of antigen-specific CD8 T cells. In binding studies with IL-2 receptors of different species, MDNA11 showed highly similar affinity towards human and cynomolgus IL2Rb, confirming the latter as a highly relevant model for toxicology study. MDNA11 was well tolerated in cynomolgus monkeys up to 0.6 mg/kg, while inducing durable (≥10 days) proliferation and expansion of NK and CD8 T cells. Effects on Tregs were minimal and there was no eosinophilia and hypotension (associated with vascular leak syndrome). At high doses of MDNA11, the most common clinical observations were transient loss of appetite and diarrhea. There was modest increase in levels of IFNg and TNFa, but no sign of cytokine release syndrome. Dosing did not trigger development of anti-drug antibodies or histopathologic evidence of pulmonary edema (a major IL-2 induced toxicity). Conclusions: MDNA11 is a long-acting IL-2 superkine that exhibits robust efficacy in mouse tumor models as a single agent and was synergistic in combination with ICIs (anti-CTLA4 and anti-PD1). In NHP, MDNA11 demonstrates selective immune effector cell activation and a favorable safety profile. These data constitute a strong framework for the design of a pivotal GLP toxicology study to further support the planned clinical study of MDNA11 either as a single agent or in combination with ICIs.