Multiplexed, quantitative serological profiling of COVID-19 from blood by a point-of-care test

Highly sensitive, specific, and point-of-care (POC) serological assays are an essential tool to manage coronavirus disease 2019 (COVID-19). Here, we report on a microfluidic POC test that can profile the antibody response against multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens-spike S1 (S1), nucleocapsid (N), and the receptor binding domain (RBD)-simultaneously from 60 μl of blood, plasma, or serum. We assessed the levels of antibodies in plasma samples from 31 individuals (with longitudinal sampling) with severe COVID-19, 41 healthy individuals, and 18 individuals with seasonal coronavirus infections. This POC assay achieved high sensitivity and specificity, tracked seroconversion, and showed good concordance with a live virus microneutralization assay. We can also detect a prognostic biomarker of severity, IP-10 (interferon-γ-induced protein 10), on the same chip. Because our test requires minimal user intervention and is read by a handheld detector, it can be globally deployed to combat COVID-19.

Resetting the tumor microenvironment to favor anti-tumor immunity after local ablation

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Background: Percutaneous tumor ablation is a non-surgical method of tumor destruction that leaves necrotic tumor debris in situ. Tumor associated antigens released after ablation have the potential to initiate a systemic anti-tumor immune response, however the hostile tumor microenvironment hinders antigen presentation and T cell activity. We hypothesized that resetting the tumor microenvironment with oral sodium bicarbonate to decrease tumor acidity and low-dose cyclophosphamide to deplete pro-tumor immune cells would improve the ability of ablation to initiate anti-tumor immunity. Methods: Tumor growth, overall survival, and metastatic burden was assessed in orthotopic tumor models of triple-negative breast cancer (67NR, 4T1, and E0771). Tumor ablation was performed on palpable tumors using percutaneous ethanol injection (PEI) with 6% ethylcellulose to improve retention in the tumor. Surgical excision was used as a negative control to test the role of in situ tumor debris. Before ablation mice were placed on 200 mM of sodium bicarbonate (SB) in their drinking water and received a single intraperitoneal injection of 200 mg/kg of cyclophosphamide (CP). Mice surviving to 60 days after tumor implant without a primary tumor or signs of metastases were considered "cured" and re-challenged with 50e5 tumor cells in the contralateral mammary pad. T cell dependance was assessed with in vivo CD8 depletions. Results: The combination of PEI+SB+CP produced a potent anti-tumor response, curing a majority of mice (5/7 of E0771, 8/12 of 67NR, 7/12 of 4T1). No mice were cured using PEI alone, SB alone, CP alone, or any combination of two therapies (0/51 of E0771, 0/73 of 67NR, 0/75 of 4T1,). Re-challenge tumor growth was hindered in mice cured with PEI+SB+CP. Mice receiving PEI+SB+CP had significantly less metastases and lived longer than mice receiving surgical excision alone or surgical excision with SB+CP. Additionally the anti-metastatic response of PEI+SB+CP was undone when CD8+ T cells were depleted. Conclusions: Here the anti-tumor response of local ablation produced by PEI was enhanced by priming the tumor with low-dose CP and oral SB in metastatic breast cancer. These results suggest that tumor ablation with CP and SB can create a T cell dependent, personalized immune response to a tumor using only low-cost, easily accessible supplies, and the host’s own tumor.

Phase I trial of intratumoral PVSRIPO in patients with unresectable, treatment-refractory melanoma

BACKGROUND

While programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) antagonists have improved the prognosis for many patients with melanoma, around 60% fail therapy. PVSRIPO is a non-neurovirulent rhinovirus:poliovirus chimera that facilitates an antitumor immune response following cell entry via the poliovirus receptor CD155, which is expressed on tumor and antigen-presenting cells. Preclinical studies show that oncolytic virus plus anti-PD-1 therapy leads to a greater antitumor response than either agent alone, warranting clinical investigation.

METHODS

An open-label phase I trial of intratumoral PVSRIPO in patients with unresectable melanoma (American Joint Committee on Cancer V.7 stage IIIB, IIIC, or IV) was performed. Eligible patients had disease progression on anti-PD-1 and V-raf murine sarcoma viral oncogene homolog B (BRAF)/mitogen activated protein kinase kinase (MEK) inhibitors (if BRAF mutant). The primary objective was to characterize the safety and tolerability of PVSRIPO. Twelve patients in four cohorts received a total of 1, 2 or 3 injections of PVSRIPO monotherapy, with 21 days between injections.

RESULTS

PVSRIPO injections were well tolerated with no serious adverse events (SAEs) or dose-limiting toxicities (DLTs) reported. All adverse events (AEs) were grade (G) 1 or G2 (G1 pruritus most common at 58%); all but two PVSRIPO-treatment related AEs were localized to the injected or adjacent lesions (n=1 G1 hot flash, n=1 G1 fatigue). Four out of 12 patients (33%) achieved an objective response per immune-related response criteria (two observations, 4 weeks apart), including 4/6 (67%) who received three injections. In the four patients with in-transit disease, a pathological complete response (pCR) was observed in two (50%) patients. Following study completion, 11/12 patients (92%) reinitiated immune checkpoint inhibitor-based therapy, and 6/12 patients (50%) remained without progression at a median follow-up time of 18 months.

CONCLUSION

Intratumoral PVSRIPO was well tolerated. Despite the limited number of PVSRIPO treatments relative to the overall lesion burden (67% patients>5 lesions), intratumoral PVSRIPO showed promising antitumor activity, with pCR in injected as well as non-injected lesions in select patients.

TRIAL REGISTRATION NUMBER

NCT03712358.

Key Pathogenic Factors in Coronavirus Disease 2019-Associated Coagulopathy and Acute Lung Injury Highlighted in a Patient With Copresentation of Acute Myelocytic Leukemia: A Case Report

The role of concurrent illness in coronavirus disease 2019 (COVID-19) is unknown. Patients with leukemia may display altered thromboinflammatory responses. We report a 53-year-old man presenting with acute leukemia and COVID-19 who developed thrombotic complications and acute respiratory distress syndrome. Multiple analyses, including rotational thromboelastometry and flow cytometry on blood and bronchoalveolar lavage, are reported to characterize coagulation and immune profiles. The patient developed chemotherapy-induced neutropenia that may have protected his lungs from granulocyte-driven hyperinflammatory acute lung injury. However, neutropenia also alters viral clearing, potentially enabling ongoing viral propagation. This case depicts a precarious equilibrium between leukemia and COVID-19.

Viral infection of cells within the tumor microenvironment mediates antitumor immunotherapy via selective TBK1-IRF3 signaling

Activating intra-tumor innate immunity might enhance tumor immune surveillance. Virotherapy is proposed to achieve tumor cell killing, while indirectly activating innate immunity. Here, we report that recombinant poliovirus therapy primarily mediates antitumor immunotherapy via direct infection of non-malignant tumor microenvironment (TME) cells, independent of malignant cell lysis. Relative to other innate immune agonists, virotherapy provokes selective, TBK1-IRF3 driven innate inflammation that is associated with sustained type-I/III interferon (IFN) release. Despite priming equivalent antitumor T cell quantities, MDA5-orchestrated TBK1-IRF3 signaling, but not NFκB-polarized TLR activation, culminates in polyfunctional and Th1-differentiated antitumor T cell phenotypes. Recombinant type-I IFN increases tumor-localized T cell function, but does not mediate durable antitumor immunotherapy without concomitant pattern recognition receptor (PRR) signaling. Thus, virus-induced MDA5-TBK1-IRF3 signaling in the TME provides PRR-contextualized IFN responses that elicit functional antitumor T cell immunity. TBK1-IRF3 innate signal transduction stimulates eventual function and differentiation of tumor-infiltrating T cells.

Abstract P102: Elevated Von Willebrand Factor in Patients Presenting With Large-Vessel Occlusion Stroke as First Symptom of COVID-19 Mirrors Levels in Patients With COVID-19 Requiring ICU-Level Care

Introduction: COVID-19 is a coagulopathic disease marked by elevated d-dimers, fibrinogen, and von Willebrand factor (vWF) levels accompanying arterial and venous thrombosis. While the majority of thrombotic events associated with COVID-19 occur in hospitalized patients, a subset of patients with minimal risk factors for CVA but with positive SARS-CoV-2 testing present with stroke as presumed first manifestation of infection. It is unclear if the pro-coagulant milieu present in patients requiring hospitalization for the respiratory complications of COVID-19 is the same as that of patients who present with stroke as first symptom of disease.

Methods: Following emergent revascularization, clinical vWF levels were measured in patients presenting with stroke who tested positive for COVID-19. In parallel, plasma vWF levels from 28 patients with COVID-19 requiring ICU-level care and 8 healthy volunteers were measured via ELISA.

Results: Three otherwise healthy patients between the ages of 45-55 years with positive test for SARS-CoV-2 presented with large-vessel stroke. By comparison, the average age of non-COVID stroke patients was 66 years. The consistency of the clots extracted through the aspirating catheter was dark, gelatinous throughout, without evidence of calcification, and distal thrombosis was noted minutes after revascularization. The vWF level for one patient was 345%, while the other two patients had vWF levels >400% of normal, exceeding the upper limit of detection of clinical assays. In the ICU cohort, 12 of 28 had thrombotic events during hospitalization. vWF levels were elevated by a mean of 800% over healthy controls with a range of 230-1670%.

Conclusions: vWF levels were markedly elevated in both ICU patients and stroke patients with COVID-19 with an overlapping range of elevation over healthy controls. This suggests that widespread endothelial inflammation accompanies infection with SARS-CoV-2 even in the absence of respiratory symptoms.

Controlling cancer-induced inflammation with a nucleic acid scavenger prevents lung metastasis in murine models of breast cancer

Tumor cells release nucleic acid-containing proinflammatory complexes, termed nucleic acid-containing damage-associated molecular patterns (NA DAMPs), passively upon death and actively during stress. NA DAMPs activate pattern recognition receptors on cells in the tumor microenvironment leading to prolonged and intensified inflammation that potentiates metastasis. No strategy exists to control endogenous or therapy-induced inflammation in cancer patients. We discovered that the generation 3.0 polyamidoamine dendrimer (PAMAM-G3) scavenges NA DAMPs and mitigates their proinflammatory effects. In this study, we tested if the nucleic acid scavenger (NAS) PAMAM-G3 reduces lung metastasis in murine models of breast cancer. Our data indicate that PAMAM-G3 treatment decreases cell-free DNA levels and reduces lung metastasis in the experimental intravenous tumor-injection model and the postsurgical tumor-resection model of 4T1 breast cancer. Reduction in lung metastasis is associated with reduction in inflammatory immune cell subsets and proinflammatory cytokine levels in the tumor and the periphery. This study is the first example of NAS-mediated inhibition of metastasis to the lung. The study results provide a strong rationale for inclusion of NAS therapy in women with breast cancer undergoing standard-of-care surgery.

Characterization of Sentinel Lymph Node Immune Signatures and Implications for Risk Stratification for Adjuvant Therapy in Melanoma

BACKGROUND

Although sentinel lymph node (SLN) biopsy is a standard procedure used to identify patients at risk for melanoma recurrence, it fails to risk-stratify certain patients accurately. Because processes in SLNs regulate anti-tumor immune responses, the authors hypothesized that SLN gene expression may be used for risk stratification.

METHODS

The Nanostring nCounter PanCancer Immune Profiling Panel was used to quantify expression of 730 immune-related genes in 60 SLN specimens (31 positive [pSLNs], 29 negative [nSLNs]) from a retrospective melanoma cohort. A multivariate prediction model for recurrence-free survival (RFS) was created by applying stepwise variable selection to Cox regression models. Risk scores calculated on the basis of the model were used to stratify patients into low- and high-risk groups. The predictive power of the model was assessed using the Kaplan-Meier and log-rank tests.

RESULTS

During a median follow-up period of 6.3 years, 20 patients (33.3%) experienced recurrence (pSLN, 45.2% [14/31] vs nSLN, 20.7% [6/29]; p = 0.0445). A fitted Cox regression model incorporating 12 genes accurately predicted RFS (C-index, 0.9919). Improved RFS was associated with increased expression of TIGIT (p = 0.0326), an immune checkpoint, and decreased expression of CXCL16 (p = 0.0273), a cytokine important in promoting dendritic and T cell interactions. Independent of SLN status, the model in this study was able to stratify patients into cohorts at high and low risk for recurrence (p < 0.001, log-rank).

CONCLUSIONS

Expression profiles of the SLN gene are associated with melanoma recurrence and may be able to identify patients as high or low risk regardless of SLN status, potentially enhancing patient selection for adjuvant therapy.

Multiplexed, quantitative serological profiling of COVID-19 from a drop of blood by a point-of-care test

Highly sensitive, specific, and point-of-care (POC) serological assays are an essential tool to manage the COVID-19 pandemic. Here, we report on a microfluidic, multiplexed POC test that can profile the antibody response against multiple SARS-CoV-2 antigens - Spike S1 (S1), Nucleocapsid (N), and the receptor binding domain (RBD) - simultaneously from a 60 microliter drop of blood, plasma, or serum. We assessed the levels of anti-SARS-CoV-2 antibodies in plasma samples from 19 individuals (at multiple time points) with COVID-19 that required admission to the intensive care unit and from 10 healthy individuals. This POC assay shows good concordance with a live virus microneutralization assay, achieved high sensitivity (100%) and specificity (100%), and successfully tracked the longitudinal evolution of the antibody response in infected individuals. We also demonstrated that we can detect a chemokine, IP-10, on the same chip, which may provide prognostic insight into patient outcomes. Because our test requires minimal user intervention and is read by a handheld detector, it can be globally deployed in the fight against COVID-19 by democratizing access to laboratory quality tests.

Abstract B16: The immune profile of sentinel lymph nodes in melanoma

Background: Immune cell composition and immune-mediated processes occurring in the sentinel lymph node (SLN) of melanoma patients regulate generation of tumor-specific effector T-cell responses and ultimately tumor control. We hypothesized that comprehensive analysis of these immune-associated processes in the SLN biopsy may identify patients at high risk of melanoma recurrence.

Methods: We analyzed 38 formalin-fixed, paraffin-embedded sentinel lymph nodes from melanoma patients undergoing SLN biopsy from 2009-2012 using the NanoString nCounter® PanCancer Immune Profiling panel. The panel included 770 immune related genes.

Results: Of 38 patients, 19 were SLN negative and 19 were SLN positive. Among SLN-negative patients (n=19), the median Breslow depth was 1.25 mm, and 21% (n=4) had developed recurrence at median follow-up of 6.2 years. Among SLN-positive patients, the median Breslow depth was 3.35 mm and 37% (n=7) had developed recurrence at median follow-up of 6.5 years. There were 31 genes significantly differentially expressed (P&lt;0.01) in SLN positive compared to SLN negative, including higher relative expression of B-cell signaling markers (CD19, CD22, Pax5, CXCR5, CD79B). Among all 38 patients, there were 13 genes differentially expressed (P&lt;0.05) between patients with and without recurrence, including higher relative expression of IL6 in patients with recurrence compared to no recurrence. Further analysis is ongoing.

Conclusion: In this retrospective series, we found the immunologic gene expression profile of melanoma SLNs was significantly different in SLN negative versus SLN positive. There were also significant differences in the profile between patients who developed melanoma recurrence versus no recurrence regardless of SLN status. We aim to build on these pilot data. The goal is to use this profile to predict patients at high risk of recurrence after SLNB who may benefit from adjuvant therapy.

Citation Format: Georgia M. Beasley, Eda K. Holl, Norma E. Farrow, Margaret G. Leddy, April K. Salama, Brent A. Hanks, Smita K. Nair. The immune profile of sentinel lymph nodes in melanoma [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr B16.

Antigen-loaded monocyte administration induces potent therapeutic antitumor T cell responses

Efficacy of dendritic cell (DC) cancer vaccines is classically thought to depend on their antigen-presenting cell (APC) activity. Studies show, however, that DC vaccine priming of cytotoxic T lymphocytes (CTLs) requires the activity of endogenous DCs, suggesting that exogenous DCs stimulate antitumor immunity by transferring antigens (Ags) to endogenous DCs. Such Ag transfer functions are most commonly ascribed to monocytes, implying that undifferentiated monocytes would function equally well as a vaccine modality and need not be differentiated to DCs to be effective. Here, we used several murine cancer models to test the antitumor efficacy of undifferentiated monocytes loaded with protein or peptide Ag. Intravenously injected monocytes displayed antitumor activity superior to DC vaccines in several cancer models, including aggressive intracranial glioblastoma. Ag-loaded monocytes induced robust CTL responses via Ag transfer to splenic CD8+ DCs in a manner independent of monocyte APC activity. Ag transfer required cell-cell contact and the formation of connexin 43-containing gap junctions between monocytes and DCs. These findings demonstrate the existence of an efficient gap junction-mediated Ag transfer pathway between monocytes and CD8+ DCs and suggest that administration of tumor Ag-loaded undifferentiated monocytes may serve as a simple and efficacious immunotherapy for the treatment of human cancers.

Oncolytic poliovirus immunotherapy for breast cancer

Oncolytic poliovirus PVSRIPO is a recombinant, non-pathogenic polio:rhinovirus chimera that enters cells via the poliovirus receptor CD155. CD155 expression is virtually universal in solid cancers, including breast cancer. CD155 is also expressed on myeloid cells. PVSRIPO infection of antigen-presenting cells (APC), including dendritic cells (DC) and macrophages, induces type I interferon and APC activation. Intratumor injection of PVSRIPO results in robust T cell infiltration and generates an immune-engaged tumor microenvironment. PVSRIPO is therefore an ideal therapeutic complement to immune checkpoint inhibitors, such as anti-PD1/PDL1.

We tested the hypothesis that blocking PD1/PDL1 in conjunction with PVSRIPO will potentiate durable antitumor immunity in the murine E0771 orthotopic breast cancer immunotherapy model. Intratumor injection of PVSRIPO in 5–7 mm orthotopic tumors induces rapid recruitment of neutrophils followed by infiltration of DC, T cells and B cells. Next, we investigated PVSRIPO with PD1/PDL1 blockade. All treatment groups significantly inhibited tumor growth compared to PBS. There were no significant differences in tumor growth inhibition between PVSRIPO and anti-PD1/PDL1 monotherapies. Combination PVSRIPO+PD1/PDL1 blockade was significantly more effective than the monotherapies at controlling tumor growth.

We also tested neoadjuvant PVSRIPO in E0771-tumor bearing mice. We observed that intratumor PVSRIPO followed by surgery effectively controls tumor growth and prevents tumor regrowth following tumor rechallenge, suggesting induction of a systemic immune response. We are now testing neoadjuvant PVSRIPO with anti-PD1/PDL1 in murine models of cancer.

Synthetic long peptide vaccines possessing a universal helper epitope can unmask the therapeutic effects of MHC I-restricted neoepitopes

Synthetic long peptide (SLP) vaccines targeting neoantigens arising from patient-specific missense mutations may offer a means to address the antigenic heterogeneity of glioblastoma (GBM) tumors by simultaneously targeting a multitude of tumor-specific antigens expressed throughout these heterogenous tumors. This approach is challenged by uncertainties pertaining to vaccine design, including peptide composition required for immunogenicity and efficacy. To this end, we investigated the mechanism of an efficacious SLP vaccine targeting the neoantigen Odc1, expressed within the mouse astrocytoma SMA560. This led to the identification of three generalizable principles governing the effectiveness of neoantigen-targeting SLPs: (1) SLPs containing an MHC I-restricted neoepitope may activate neoantigen-reactive CD8+ T cells, which drive direct antitumor effects; (2) to induce robust neoantigen-reactive CD8+ T-cell responses, CD40L-mediated T cell "help" is required; and, (3) CD40L interactions are conferred by an SLP only when a “helper” epitope is physically conjoined to an MHC I-restricted neoepitope. To leverage these findings for clinical translation, we developed a rationally-designed vaccine comprised of an MHC I-restricted neoepitope linked to a universal “helper” epitope. This design was capable of maintaining the effects of the Odc1 vaccine and, remarkably, unmasked the therapeutic effects of, otherwise, poorly immunogenic MHC I-restricted neoepitopes. Together, these findings are significant because they elucidate mechanisms required for efficacious SLP vaccines and demonstrate a clinically-tractable approach with the potential to expand the therapeutic breadth of neoantigen vaccines.

Abstract A90: Blocking proinvasive signaling and inflammatory activation in triple-negative breast cancer with nucleic-acid scavengers (NAS)

Breast cancers (BC) remain the most lethal malignancies among women worldwide and the second leading cause of cancer-related mortalities in the US. Subtype heterogeneity and aggressive invasive potential are believed to be the major contributors of these outcomes. BC lacking canonical histologic receptors (i.e., ER/PR/HER2), called triple negative (TNBC), are notoriously aggressive, difficult to treat, and metastatic. It has been observed that the degree of inflammation-driven tumorigenesis tends to correlate with increased levels of cell free DNA (cfDNA) and other damage-associated molecular patterns (DAMPs) in cancer patient sera. Our lab has previously shown that nucleic-acid scavengers (NAS) can block proinflammatory and proinvasive/metastatic signals elicited by nucleic acid-containing DAMP activation of innate immune sensors such as of the Toll-like receptors (TLRs). Recently, we showed that treatment with the nucleic acid-binding polymer, PAMAM-G3, resulted in a drastic reduction in metastatic tumor burden to the liver in an immunocompetent murine model of pancreatic cancer (Naqvi I, Gunaratne R, et al., Mol Ther 2018;26). Ongoing work has shown that chemotherapy-derived TNBC-conditioned media (CM) and TNBC patient sera greatly increase TNBC cell invasion in vitro and that treatment with the NAS PAMAM-G3 significantly inhibits this effect. Treatment of the human monocyte cell line, THP-1, with TNBC CM elicited a very strong proinflammatory response comparable to known innate immune stimulants such as poly(I:C), LPS, and CpG, with elevated levels of IL-8, IL-6, MCP-1 (CCL2), IL-18, and IL-1β. Other biologically relevant immune responders such as isolated human PBMCs and whole blood will be tested to determine the potential impact on the tumor immune microenvironment during tumorigenesis and treatment. To elucidate the mechanism by which this NAS works in these tumor settings, our lab has developed several PAMAM-G3 derivatives, including biotin, IR-, and near-IR fluorophore-labeled molecules. These molecules will allow us to conduct DAMP capture and characterization experiments, as well as perform in vitro and in vivo live imaging experiments to gain insight into NAS PK/PD properties. Mechanistic insight into NAS antimetastatic and anti-inflammatory capabilities will enhance our understanding of metastatic progression and its interplay with the immune system. Moreover, these principles will aid in the development of novel of antimetastatic therapies to improve TNBC patient outcomes.

Citation Format: Elias O.U. Eteshola, Karenia Landa, E. Shelley Hwang, Angelo Moreno, Smita K. Nair, Bruce A. Sullenger. Blocking proinvasive signaling and inflammatory activation in triple-negative breast cancer with nucleic-acid scavengers (NAS) [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A90.

Genetically stable poliovirus vectors activate dendritic cells and prime antitumor CD8 T cell immunity

Viruses naturally engage innate immunity, induce antigen presentation, and mediate CD8 T cell priming against foreign antigens. Polioviruses can provide a context optimal for generating antigen-specific CD8 T cells, as they have natural tropism for dendritic cells, preeminent inducers of CD8 T cell immunity; elicit Th1-promoting inflammation; and lack interference with innate or adaptive immunity. However, notorious genetic instability and underlying neuropathogenicity has hampered poliovirus-based vector applications. Here we devised a strategy based on the polio:rhinovirus chimera PVSRIPO, devoid of viral neuropathogenicity after intracerebral inoculation in human subjects, for stable expression of exogenous antigens. PVSRIPO vectors infect, activate, and induce epitope presentation in DCs in vitro; they recruit and activate DCs with Th1-dominant cytokine profiles at the injection site in vivo. They efficiently prime tumor antigen-specific CD8 T cells in vivo, induce CD8 T cell migration to the tumor site, delay tumor growth and enhance survival in murine tumor models.

Experimental PVSRIPO oncolytic virus therapy of glioblastoma has shown long-term efficacy in a subset of patients. Here the authors engineer the virus to enable incorporation of tumor-specific antigens, and show proof-of-principle evidence that this modification increases anti-tumor immunity and extends survival in mice.

Immune expression in children with Wilms tumor: a pilot study

BACKGROUND

Given improvements in multimodality therapy, survival among children with Wilms tumor (WT) exceeds 90%. However, 15% of children with favorable histology and 50% of children with anaplastic WT experience recurrence or progression. Of patients with advanced disease, only 50% survive to adulthood. In adult malignancies (including renal tumors), patient survival has improved with the advent of immunotherapy. However, little is known about the immune microenvironment of WT, making the potential role of immunotherapy unclear.

OBJECTIVE

The objective of the study is to perform an exploratory, descriptive analysis of the immune milieu in WT.

STUDY DESIGN

Between 2016 and 2017, all pediatric patients with WT, some of whom received neoadjuvant chemotherapy, underwent ex vivo wedge biopsy at the time of nephrectomy. The fresh tumor tissue and peripheral blood samples were analyzed for infiltrating immune infiltrate and effector cells using flow cytometry. Immunohistochemistry was performed for CD4, CD8, and PD-L1 expression. Matched blood samples were obtained for each patient, and circulating immune cells were analyzed by flow cytometry.

RESULTS

A total of six patients were enrolled. One patient with neuroblastoma was excluded. The remaining five patients included the following: two with unilateral WT (resected before chemotherapy), two with bilateral WT (resected after neoadjuvant chemotherapy), and one with Denys-Drash syndrome, end-stage renal disease, and history of WT in the contralateral kidney. Immune analysis showed that WT were infiltrated by immune cells regardless of chemotherapy status. CD8 and CD4 T cells were present in the tumor tissue and exhibited an activated phenotype. Elevated levels of natural killer (NK) cells were observed in the tumors (Figure). Immune checkpoint PD-L1 was also found expressed in one of the tumors stained.

DISCUSSION

In this pilot study, it was found that WTs were infiltrated by immune cells (CD45+) both before and after chemotherapy. Elevated levels of NK cells infiltrating the tumor specimens, which were quantitatively increased compared with levels of NK cells circulating in the blood, were noted. T cells, particularly CD4+ and CD8+ T cells, were present in tumor specimens. Tumor-infiltrating CD4 and CD8 T cells displayed an activated phenotype as defined by increased expression of human leukocyte antigen-DR isotype (HLA-DR), programmed cell death protein 1 (PD1), and CD57. Together, these findings suggest that WT microenvironment is immune engaged and may be susceptible to immunotherapy similar to other malignancies.

CONCLUSIONS

These pilot data suggest an immune-engaged tumor microenvironment is present within WT. This implies that WT may be susceptible to immunotherapy similar to adult renal tumors and other adult malignancies. Follow-up studies are currently underway.

Recombinant Poliovirus for Cancer Immunotherapy

Mechanisms to elicit antiviral immunity, a natural host response to viral pathogen challenge, are of eminent relevance to cancer immunotherapy. "Oncolytic" viruses, naturally existing or genetically engineered viral agents with cell type-specific propagation in malignant cells, were ostensibly conceived for their tumor cytotoxic properties. Yet, their true therapeutic value may rest in their ability to provoke antiviral signals that engage antitumor immune responses within the immunosuppressive tumor microenvironment. Coopting oncolytic viral agents to instigate antitumor immunity is not an easy feat. In the course of coevolution with their hosts, viruses have acquired sophisticated strategies to block inflammatory signals, intercept innate antiviral interferon responses, and prevent antiviral effector responses, e.g., by interfering with antigen presentation and T cell costimulation. The resulting struggle of host innate inflammatory and antiviral responses versus viral immune evasion and suppression determines the potential for antitumor immunity to occur. Moreover, paradigms of early host:virus interaction established in normal immunocompetent organisms may not hold in the profoundly immunosuppressive tumor microenvironment. In this review, we explain the mechanisms of recombinant nonpathogenic poliovirus, PVSRIPO, which is currently in phase I clinical trials against recurrent glioblastoma. We focus on an unusual host:virus relationship defined by the simple and cytotoxic replication strategy of poliovirus, which generates inflammatory perturbations conducive to tumor antigen-specific immune priming.

Examining Peripheral and Tumor Cellular Immunome in Patients With Cancer

Immunotherapies are rapidly being integrated into standard of care (SOC) therapy in conjunction with surgery, chemotherapy, and radiotherapy for many cancers and a large number of clinical studies continue to explore immunotherapy alone and as part of combination therapies in patients with cancer. It is evident that clinical effectiveness of immunotherapy is limited to a subset of patients and improving immunotherapy related outcomes remains a major scientific and clinical effort. Understanding the immune cell subset phenotype and activation/functional status (cellular immunome) prior to and post therapy is therefore critical to develop biomarkers that (1) will predict if a patient will respond to immunotherapy and (2) are a result of immunotherapy. In this study, we investigated local (tumor) and peripheral (blood) cellular immunome of patients with melanoma, breast cancer, and brain cancer using a rapid and reliable standardized, multiparameter flow cytometry assay. We used this approach to monitor changes in the peripheral cellular immunome in women with breast cancer undergoing SOC therapy. Our analysis is unique because it is conducted using matched fresh tumor tissue and blood from patients in real-time, within 2–3 h of sample acquisition, and provides insight into the innate and adaptive immune cell profile in blood and tumor. Specific to blood, this approach involves no manipulation and evaluates all immune subsets such as T cells, B cells, natural killer (NK) cells, monocytes, dendritic cells (DCs), neutrophils, eosinophils, and basophils using 0.5 ml of blood. Analysis of the corresponding tumor provides much needed insight into the phenotype and activation status of immune cells, especially T and B cells, in the tumor microenvironment vs. the periphery. This analysis will be used to assess baseline and therapy-mediated changes in local and peripheral cellular immunome in patients with glioblastoma, breast cancer, and melanoma in planned immunotherapy clinical studies.

Abstract 4515: Utilizing nucleic-acid scavengers (NASs) to inhibit proinflammatory and proinvasive signaling in triple-negative breast cancer

Breast cancers (BC) remain the most lethal malignancies amongst women worldwide and the second leading cause of cancer-related mortalities in the US. Subtype heterogeneity and aggressive invasive potential are believed to be the major contributors of these outcomes. BC lacking canonical histological receptors (i.e. ER/PR/HER2), called triple-negative (TNBC), are notoriously aggressive, difficult-to-treat, and metastatic. It has been observed that the degree of inflammation-driven tumorigenesis tends to correlate with increased levels of cell-free DNA (cfDNA) in cancer patient sera. Our lab had previously shown that nucleic-acid scavengers (NASs) could be used to block the pro-inflammatory and pro-invasive/metastatic signals (e.g. DAMPs) elicited by these cfDNA/RNA likely through innate immune sensors such as of the toll-like receptors (TLRs). Recently, we showed that treatment with the cationic polymer NAS, PAMAM-G3, elicited a drastic reduction in metastatic tumor burden to the liver in an immune-competent murine model of pancreatic cancer (I. Naqvi & R. Gunaratne et al., Molecular Therapy 26, 2018). Ongoing work has shown that both chemotherapy-derived TNBC conditioned media and a TLR9 agonist greatly increased TNBC in vitro invasion and was significantly inhibited upon treatment with PAMAM-G3. To elucidate the mechanism by which this NAS works in these tumor settings, our lab has developed several PAMAM-G3 derivatives, including biotin, IR-, and near-IR fluorophore labeled molecules. These molecules will allow us to conduct DAMP capture and characterization experiments, as well as perform in vitro and in vivo live imaging experiments to gain better insights into NAS PK/PD properties. Mechanistic insight into NAS anti-metastatic and anti-inflammatory capabilities will enhance our basic understanding of metastatic progression and its interplay with the immune system. Moreover, these principles will aid in the development of novel of anti-metastatic therapies to improve TNBC patient outcomes.

Citation Format: Elias O. Eteshola, Ibtehaj A. Naqvi, Ruwan Gunaratne, Angelo Moreno, Smita K. Nair, Bruce A. Sullenger. Utilizing nucleic-acid scavengers (NASs) to inhibit proinflammatory and proinvasive signaling in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4515.

Improved efficacy against malignant brain tumors with EGFRwt/EGFRvIII targeting immunotoxin and checkpoint inhibitor combinations

BACKGROUND

D2C7-IT is a novel immunotoxin (IT) targeting wild-type epidermal growth factor receptor (EGFRwt) and mutant EGFR variant III (EGFRvIII) proteins in glioblastoma. In addition to inherent tumoricidal activity, immunotoxins induce secondary immune responses through the activation of T cells. However, glioblastoma-induced immune suppression is a major obstacle to an effective and durable immunotoxin-mediated antitumor response. We hypothesized that D2C7-IT-induced immune response could be effectively augmented in combination with αCTLA-4/αPD-1/αPD-L1 therapies in murine models of glioma.

METHODS

To study this, we overexpressed the D2C7-IT antigen, murine EGFRvIII (dmEGFRvIII), in established glioma lines, CT-2A and SMA560. The reactivity and therapeutic efficacy of D2C7-IT against CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII cells was determined by flow cytometry and in vitro cytotoxicity assays, respectively. Antitumor efficacy of D2C7-IT was examined in immunocompetent, intracranial murine glioma models and the role of T cells was assessed by CD4+ and CD8+ T cell depletion. In vivo efficacy of D2C7-IT/αCTLA-4/αPD-1 monotherapy or D2C7-IT+αCTLA-4/αPD-1 combination therapy was evaluated in subcutaneous unilateral and bilateral CT-2A-dmEGFRvIII glioma-bearing immunocompetent mice. Further, antitumor efficacy of D2C7-IT+αCTLA-4/αPD-1/αPD-L1/αTim-3/αLag-3/αCD73 combination therapy was evaluated in intracranial CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII glioma-bearing mice. Pairwise differences in survival curves were assessed using the generalized Wilcoxon test.

RESULTS

D2C7-IT effectively killed CT-2A-dmEGFRvIII (IC₅₀ = 0.47 ng/mL) and SMA560-dmEGFRvIII (IC₅₀ = 1.05 ng/mL) cells in vitro. Treatment of intracranial CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII tumors with D2C7-IT prolonged survival (P = 0.0188 and P = 0.0057, respectively), which was significantly reduced by the depletion of CD4+ and CD8+ T cells. To augment antitumor immune responses, we combined D2C7-IT with αCTLA-4/αPD-1 in an in vivo subcutaneous CT-2A-dmEGFRvIII model. Tumor-bearing mice exhibited complete tumor regressions (4/10 in D2C7-IT+αCTLA-4 and 5/10 in D2C7-IT+αPD-1 treatment groups), and combination therapy-induced systemic antitumor response was effective against both dmEGFRvIII-positive and dmEGFRvIII-negative CT-2A tumors. In a subcutaneous bilateral CT-2A-dmEGFRvIII model, D2C7-IT+αCTLA-4/αPD-1 combination therapies showed dramatic regression of the treated tumors and measurable regression of untreated tumors. Notably, in CT-2A-dmEGFRvIII and SMA560-dmEGFRvIII intracranial glioma models, D2C7-IT+αPD-1/αPD-L1 combinations improved survival, and in selected cases generated cures and protection against tumor re-challenge.

CONCLUSIONS

These data support the development of D2C7-IT and immune checkpoint blockade combinations for patients with malignant glioma.

Can Exercise-Induced Modulation of the Tumor Physiologic Microenvironment Improve Antitumor Immunity?

The immune system plays an important role in controlling cancer growth. However, cancers evolve to evade immune detection. Immune tolerance and active immune suppression results in unchecked cancer growth and progression. A major contributor to immune tolerance is the tumor physiologic microenvironment, which includes hypoxia, hypoglucosis, lactosis, and reduced pH. Preclinical and human studies suggest that exercise elicits mobilization of leukocytes into circulation (also known as "exercise-induced leukocytosis"), especially cytotoxic T cells and natural killer cells. However, the tumor physiologic microenvironment presents a significant barrier for these cells to enter the tumor and, once there, properly function. We hypothesize that the effect of exercise on the immune system's ability to control cancer growth is linked to how exercise affects the tumor physiologic microenvironment. Normalization of the microenvironment by exercise may promote more efficient innate and adaptive immunity within the tumor. This review summarizes the current literature supporting this hypothesis.

Targeting DAMP-induced inflammation to prevent breast cancer metastasis and improve anti-tumor immunity

Biomarkers associated with systemic inflammation correlate with poor prognosis in cancer patients. Circulating cell-free DNA (cfDNA) is released passively and actively by both tumor cells and host cells and cfDNA levels in blood correlate with tumor burden in many tumor types. Notably, studies in breast cancer have shown that inhibition of cfDNA has a significant effect in reducing invasion and migration in vitro and metastatic disease in vivo. We have previously demonstrated that nucleic acid binding polymers (NABPs) bind and inhibit the proinflammatory effects of cfDNA in a murine model of pancreatic cancer.

We observed that levels of cfDNA in blood increase with tumor burden in an orthotopic immunocompetent murine model of breast cancer. Moreover, treatment of mice with the NABP, PAMAM-G3, following surgical removal of primary tumor results in decreased lung metastasis. This decrease in lung metastasis is associated with reduction in the levels of cfDNA in blood.

In addition, treatment of mice with NABPs in an intravenous experimental metastasis breast cancer model results in reduced seeding of tumor cells in lungs and lung metastasis. Analysis of immune infiltrates in lungs of PAMAM-G3- and control-treated mice demonstrates NABP-mediated transition of immune cell composition in lungs from innate to adaptive immune cells. Collectively, these data suggest that NABPs can be used to target cfDNA and inhibit DAMPs associated pathological inflammation. The use of NABPs is an innovative approach to treat cancer progression and metastasis, particularly in a clinical setting following standard of care surgical tumor resection.

This work is funded by the Department of Defense Breast Cancer Research Program award (PI, Smita Nair).

Abstract A79: Cancer immunotherapy with recombinant poliovirus induces IFN-dominant activation of antigen-presenting cells and tumor antigen-specific CTLs

The tumor microenvironment favors tumor immune escape by suppressing production, activation and/or function of antitumor T cells. Our group has developed a recombinant Rhino-Poliovirus chimera, PVSRIPO, currently being evaluated in Phase-II clinical trial against recurrent glioma. PVSRIPO therapy has afforded durable clinical responses in recurrent glioma patients. Clinical and pre-clinical findings suggest that PVSRIPO primarily acts through an immunological mechanism, rather than via cancer selective cytotoxicity. Here we define the immune adjuvant potential of intratumoral-delivered PVSRIPO that ultimately leads to the engagement/production of antitumor T cells. Sub-lethal infection of human dendritic cells (DCs) with PVSRIPO yields potent, sustained type I interferon dominant activation. PVSRIPO infection of macrophages induces similar activation; however, virus translation and the resulting type I Interferon/TNF-α production by macrophages is strongly enhanced in the presence of the Th2 cytokine IL-4. Compared to conventional adjuvants, e.g. poly(I:C) and LPS, PVSRIPO stimulation of APCs withstands tumor-associated immunosuppression, particularly in macrophages, and achieves more durable activation of DCs. Therapy of B16 melanoma tumors with PVSRIPO led to early production of type I interferon, IL-12, and IFN-γ; which was associated with the recruitment of neutrophils to the tumor site. Neutrophil influx was followed by DC and T cell infiltration. Mice treated with PVSRIPO developed tumor-antigen specific, cytotoxic T cells that were present in both tumor draining lymph nodes and spleens. These events correlated with delay in tumor growth and increase in survival following PVSRIPO therapy. Thus, PVSRIPO’s immune adjuvancy stimulates canonical innate inflammatory responses within the tumor microenvironment that culminates in tumor antigen-specific T cell responses.

Citation Format: Michael C. Brown, Eda K. Holl, David Boczkowski, Elena Dobrikova, Mubeen Mosaheb, Vidya Chandramohan, Darell D. Bigner, Matthias Gromeier, Smita K. Nair. Cancer immunotherapy with recombinant poliovirus induces IFN-dominant activation of antigen-presenting cells and tumor antigen-specific CTLs [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A79.

Targeting inflammation to prevent breast cancer metastasis

Biomarkers associated with systemic inflammation correlate with poor prognosis in cancer patients. Circulating cell-free DNA (cfDNA) is released passively and actively by both tumor cells and host cells and cfDNA levels in blood correlate with tumor burden in many tumor types. Notably, studies in breast cancer have shown that inhibition of cfDNA has a significant effect in reducing invasion and migration in vitro. We have previously demonstrated the ability of nucleic acid binding polymers (NABPs) to bind and inhibit the pro-inflammatory effects of cfDNA and RNA in models of systemic lupus erythematosus and influenza. Herein, we demonstrate that in tumor bearing mice, levels of cfDNA increase with tumor burden and decline post NABP in vivo administration. Using an orthotopic breast cancer murine model we demonstrate that NABP treatment, following surgical resection, results in reduced or completely absent lung metastasis. In addition, intravenous delivery of breast cancer cells in the presence of NABPs also results in decreased tumor cell lung seeding and lung metastasis. Taken together, our data suggest that NABPs can be used to target cfDNA and inhibit such DAMPs from activating pathological inflammation, an innovative approach to treat cancer progression and metastasis. In particular, NABPs may be useful in the clinical setting following standard of care surgical tumor resection.

Recombinant oncolytic poliovirus, PVSRIPO, has potent cytotoxic and innate inflammatory effects, mediating therapy in human breast and prostate cancer xenograft models

Intratumoral inoculation of viruses with tumor-selective cytotoxicity may induce cancer cell death and, thereby, shrink neoplastic lesions. It is unlikely, however, that viral tumor cell killing alone could produce meaningful, durable clinical responses, as clinically suitable ‘oncolytic’ viruses are severely attenuated and their spread and propagation are opposed by host immunity. Thus, a more propitious event in this context is the innate antiviral response to intratumoral virus administration, in particular for recruiting durable adaptive immune effector responses. It may represent a double-edged sword, as innate immune activation may eliminate infected tumor cells early, intercept viral spread and block any meaningful therapeutic response. The innate response to viral infection of tumors may be very different from that in non-malignant target tissues, owing to the unusual composition/tissue properties of tumor stroma. In this work, we report investigations of the innate immune response to the oncolytic poliovirus recombinant, PVSRIPO, in two mouse xenotransplantation models for breast and prostate cancer. Our observations indicate short-term virus persistence in infected tumors and virus recovery indicative of modest intratumoral propagation and persistence. Yet, a powerful innate inflammatory response coincided with chemokine induction and myeloid cell infiltration into tumors that was, interestingly, dominated by neutrophils. The combined effect of PVSRIPO tumor infection and the innate response it elicits was significant tumor regression in both models.