Stability and safety key factors of the oncolytic protoparvovirus H-1 from manufacturing to human application.

The oncolytic rodent protoparvovirus H-1PV has been successfully used in phase I/II clinical trials to treat recurrent glioblastoma multiforme and pancreatic cancer. The present work focuses on the stability and environmental safety of the H-1PV drug product from production up to its use in patients. We identified hold-steps in manufacturing for up to 3 months and showed 7-years stability for the optimal product formulation. Stress testing via UV, temperature, and pH also determined that the drug product is stable. De- and rehydration for lyophilization simulation are possible without infectious virus loss. Furthermore, we prove in-use stability for 4 days at room temperature and show no virus adsorption to injection devices, guaranteeing the correct administration dose. Iodixanol in the formulation, resulting in high viscosity, protects H-1PV against UV and some disinfectants. Nonetheless, H-1PV is depleted with rapid heat deactivation, autoclavation, and nanofiltration. Assessment of chemical disinfectants that are currently recommended by the Robert Koch-Institute demonstrated that ethanol-based hand disinfectants are not effective; however, aldehyde-based disinfectants for surfaces and instruments demonstrate sufficient H-1PV deactivation in aqueous formulations by 4 to 6 log10. With these results, we could establish a specific hygiene plan for all involved facilities from manufacturing to patient application. Overall, using 48% Iodixanol in Visipaque/Ringer as a drug formulation stabilizes H-1PV infectivity over years and protects against virus loss from short-term UV, low pH, and temperature exposure. KEY POINTS: • Optimal formulation of drug product protects the H-1PV protoparvovirus against UV, temperatures up to 50 °C, and low pH (> 1.25), stabilizing the virus during manufacturing, storage, transport, and application. • H-1PV is stable during in-use and does not adsorb to injection devices during patient administration. • Hygiene plan for H-1PV with physicochemical methods has been established.

SUMOylation Targets Adeno-associated Virus Capsids but Mainly Restricts Transduction by Cellular Mechanisms.

Adeno-associated virus (AAV) has proven to be a promising candidate for gene therapy due to its nonpathogenic nature, ease of production, and broad tissue tropism. However, its transduction capabilities are not optimal due to the interaction with various host factors within the cell. In a previous study, we identified members of the small ubiquitin-like modifier (SUMO) pathway as significant restriction factors in AAV gene transduction. In the present study, we explored the scope of this restriction by focusing on the AAV capsid and host cell proteins as targets. We show that during vector production, the capsid protein VP2 becomes SUMOylated, as indicated by deletion and point mutations of VP2 or the obstruction of its N terminus via the addition of a tag. We observed that SUMOylated AAV capsids display higher stability than non-SUMOylated capsids. Prevention of capsid SUMOylation by VP2 mutations did not abolish transduction restriction by SUMOylation; however, it reduced activation of gene transduction by shutdown of the cellular SUMOylation pathway. This indicates a link between capsid SUMOylation and SUMOylation of cellular proteins in restricting gene transduction. Infection with AAV triggers general SUMOylation of cellular proteins. In particular, the DAXX protein, a putative host cell restriction factor that can become SUMOylated, is able to restrict AAV gene transduction by reducing the intracellular accumulation of AAV vectors. We also observe that the coexpression of a SUMOylation inhibitor with an AAV2 reporter gene vector increased gene transduction significantly.IMPORTANCE Host factors within the cell are the major mode of restriction of adeno-associated virus (AAV) and keep it from fulfilling its maximum potential as a gene therapy vector. A better understanding of the intricacies of restriction would enable the engineering of better vectors. Via a genome-wide short interfering RNA screen, we identified that proteins of the small ubiquitin-like modifier (SUMO) pathway play an important role in AAV restriction. In this study, we investigate whether this restriction is targeted to the AAV directly or indirectly through host cell factors. The results indicate that both targets act in concert to restrict AAV.

Upstream process optimization and micro- and macrocarrier screening for large-scale production of the oncolytic H-1 protoparvovirus.

The oncolytic virus H-1PV is a promising candidate for various cancer treatments. Therefore, production process needs to be optimized and scaled up for future market release. Currently, the virus is produced with minimum essential medium in 10-layer CellSTACK® chambers with limited scalability, requiring a minimum seeding density of 7.9E3 cells/cm2. Production also requires a 5% fetal bovine serum (FBS) supplementation and has a virus yield up to 3.1E7 plaque-forming units (PFU)/cm2. Using the animal-free cell culture medium VP-SFM™ and a new feeding strategy, we demonstrate a yield boost by a mean of 0.3 log while reducing seeding density to 5.0E3 cells/cm2 and cutting FBS supplementation by up to 40% during the production process. Additionally, FBS is completely removed at the time of harvest. Eleven commercial micro- and macrocarriers were screened regarding cell growth, bead-to-bead transfer capability, and virus yield. We present a proof-of-concept study for producing H-1PV on a large scale with the microcarrier Cytodex® 1 in suspension and a macrocarrier for a fixed-bed iCELLis® bioreactor. A carrier-based H-1PV production process combined with an optimized cell culture medium and feeding strategy can facilitate future upscaling to industrial-scale production. KEY POINTS: • Virus yield increase and FBS-free harvest after switching to cell culture medium VP-SFM™. • We screened carriers for cell growth, bead-to-bead transfer capability, and H-1PV yield. • High virus yield is achieved with Cytodex® 1 and macrocarrier for iCellis® in Erlenmeyer flasks.

Oncolytic H-1 Parvovirus Shows Safety and Signs of Immunogenic Activity in a First Phase I/IIa Glioblastoma Trial.

Oncolytic virotherapy may be a means of improving the dismal prognosis of malignant brain tumors. The rat H-1 parvovirus (H-1PV) suppresses tumors in preclinical glioma models, through both direct oncolysis and stimulation of anticancer immune responses. This was the basis of ParvOryx01, the first phase I/IIa clinical trial of an oncolytic parvovirus in recurrent glioblastoma patients. H-1PV (escalating dose) was administered via intratumoral or intravenous injection. Tumors were resected 9 days after treatment, and virus was re-administered around the resection cavity. Primary endpoints were safety and tolerability, virus distribution, and maximum tolerated dose (MTD). Progression-free and overall survival and levels of viral and immunological markers in the tumor and peripheral blood were also investigated. H-1PV treatment was safe and well tolerated, and no MTD was reached. The virus could cross the blood-brain/tumor barrier and spread widely through the tumor. It showed favorable pharmacokinetics, induced antibody formation in a dose-dependent manner, and triggered specific T cell responses. Markers of virus replication, microglia/macrophage activation, and cytotoxic T cell infiltration were detected in infected tumors, suggesting that H-1PV may trigger an immunogenic stimulus. Median survival was extended in comparison with recent meta-analyses. Altogether, ParvOryx01 results provide an impetus for further H-1PV clinical development.

A non-controlled, single arm, open label, phase II study of intravenous and intratumoral administration of ParvOryx in patients with metastatic, inoperable pancreatic cancer: ParvOryx02 protocol.

BACKGROUND: Metastatic pancreatic cancer has a dismal prognosis, with a mean six-month progression-free survival of approximately 50% and a median survival of about 11 months. Despite intensive research, only slight improvements of clinical outcome could be achieved over the last decades. Hence, new and innovative therapeutic strategies are urgently required. ParvOryx is a drug product containing native parvovirus H-1 (H-1PV). Since H-1PV was shown to exert pronounced anti-neoplastic effects in pre-clinical models of pancreatic cancer, the drug appears to be a promising candidate for treatment of this malignancy. METHODS: ParvOryx02 is a non-controlled, single arm, open label, dose-escalating, single center trial. In total seven patients with pancreatic cancer showing at least one hepatic metastasis are to be treated with escalating doses of ParvOryx according to the following schedule: i) 40% of the total dose infused intravenously in equal fractions on four consecutive days, ii) 60% of the total dose injected on a single occasion directly into the hepatic metastasis at varying intervals after intravenous infusions. The main eligibility criteria are: age ≥ 18 years, disease progression despite first-line chemotherapy, and at least one hepatic metastasis. Since it is the second trial within the drug development program, the study primarily explores safety and tolerability after further dose escalation of ParvOryx. The secondary objectives are related to the evaluation of certain aspects of anti-tumor activity and clinical efficacy of the drug. DISCUSSION: This trial strongly contributes to the clinical development program of ParvOryx. The individual hazards for patients included in the current study and the environmental risks are addressed and counteracted adequately. Besides information on safety and tolerability of the treatment after further dose escalation, thorough evaluations of pharmacokinetics and intratumoral spread as well as proof-of-concept (PoC) in pancreatic cancer will be gained in the course of the trial. TRIAL REGISTRATION: ClinicalTrials.gov-ID: NCT02653313 , Registration date: Dec. 4th, 2015.

A novel scalable, robust downstream process for oncolytic rat parvovirus: isoelectric point-based elimination of empty particles.

The rodent protoparvovirus H-1PV, with its oncolytic and oncosuppressive properties, is a promising anticancer agent currently under testing in clinical trials. This explains the current demand for a scalable, good manufacturing practice-compatible virus purification process yielding high-grade pure infectious particles and overcoming the limitations of the current system based on density gradient centrifugation. We describe here a scalable process offering high purity and recovery. Taking advantage of the isoelectric point difference between full and empty particles, it eliminates most empty particles. Full particles have a significantly higher cationic charge than empty ones, with an isoelectric point of 5.8-6.2 versus 6.3 (as determined by isoelectric focusing and chromatofocusing). Thanks to this difference, infectious full particles can be separated from empty particles and most protein impurities by Convective interaction media® diethylaminoethyl (DEAE) anion exchange chromatography: applying unpurified H-1PV to the column in 0.15 M NaCl leaves, the former on the column and the latter in the flow through. The full particles are then recovered by elution with 0.25 M NaCl. The whole large-scale purification process involves filtration, single-step DEAE anion exchange chromatography, buffer exchange by cross-flow filtration, and final formulation in Visipaque/Ringer solution. It results in 98% contaminating protein removal and 96% empty particle elimination. The final infectious particle concentration reaches 3.5E10 plaque forming units (PFU)/ml, with a specific activity of 6.8E11 PFU/mg protein. Overall recovery is over 40%. The newly established method is suitable for use in commercial production.

Identification of NY-BR-1-specific CD4(+) T cell epitopes using HLA-transgenic mice.

Breast cancer represents the second most common cancer type worldwide and has remained the leading cause of cancer-related deaths among women. The differentiation antigen NY-BR-1 appears overexpressed in invasive mammary carcinomas compared to healthy breast tissue, thus representing a promising target antigen for T cell based tumor immunotherapy approaches. Since efficient immune attack of tumors depends on the activity of tumor antigen-specific CD4(+) effector T cells, NY-BR-1 was screened for the presence of HLA-restricted CD4(+) T cell epitopes that could be included in immunological treatment approaches. Upon NY-BR-1-specific DNA immunization of HLA-transgenic mice and functional ex vivo analysis, a panel of NY-BR-1-derived library peptides was determined that specifically stimulated IFNγ secretion among splenocytes of immunized mice. Following in silico analyses, four candidate epitopes were determined which were successfully used for peptide immunization to establish NY-BR-1-specific, HLA-DRB1*0301- or HLA-DRB1*0401-restricted CD4(+) T cell lines from splenocytes of peptide immunized HLA-transgenic mice. Notably, all four CD4(+) T cell lines recognized human HLA-DR-matched dendritic cells (DC) pulsed with lysates of NY-BR-1 expressing human tumor cells, demonstrating natural processing of these epitopes also within the human system. Finally, CD4(+) T cells specific for all four CD4(+) T cell epitopes were detectable among PBMC of breast cancer patients, showing that CD4(+) T cell responses against the new epitopes are not deleted nor inactivated by self-tolerance mechanisms. Our results present the first NY-BR-1-specific HLA-DRB1*0301- and HLA-DRB1*0401-restricted T cell epitopes that could be exploited for therapeutic intervention against breast cancer.

Oncolytic effects of parvovirus H-1 in medulloblastoma are associated with repression of master regulators of early neurogenesis.

Based on extensive pre-clinical studies, the oncolytic parvovirus H-1 (H-1PV) is currently applied to patients with recurrent glioblastoma in a phase I/IIa clinical trial (ParvOryx01, NCT01301430). Cure rates of about 40% in pediatric high-risk medulloblastoma (MB) patients also indicate the need of new therapeutic approaches. In order to prepare a future application of oncolytic parvovirotherapy to MB, the present study preclinically evaluates the cytotoxic efficacy of H-1PV on MB cells in vitro and characterizes cellular target genes involved in this effect. Six MB cell lines were analyzed by whole genome oligonucleotide microarrays after treatment and the results were matched to known molecular and cytogenetic risk factors. In contrast to non-transformed infant astrocytes and neurons, in five out of six MB cell lines lytic H-1PV infection and efficient viral replication could be demonstrated. The cytotoxic effects induced by H-1PV were observed at LD50s below 0.05 p. f. u. per cell indicating high susceptibility. Gene expression patterns in the responsive MB cell lines allowed the identification of candidate target genes mediating the cytotoxic effects of H-1PV. H-1PV induced down-regulation of key regulators of early neurogenesis shown to confer poor prognosis in MB such as ZIC1, FOXG1B, MYC, and NFIA. In MB cell lines with genomic amplification of MYC, expression of MYC was the single gene most significantly repressed after H-1PV infection. H-1PV virotherapy may be a promising treatment approach for MB since it targets genes of functional relevance and induces cell death at very low titers of input virus.

Retargeting of rat parvovirus H-1PV to cancer cells through genetic engineering of the viral capsid.

The rat parvovirus H-1PV is a promising anticancer agent given its oncosuppressive properties and the absence of known side effects in humans. H-1PV replicates preferentially in transformed cells, but the virus can enter both normal and cancer cells. Uptake by normal cells sequesters a significant portion of the administered viral dose away from the tumor target. Hence, targeting H-1PV entry specifically to tumor cells is important to increase the efficacy of parvovirus-based treatments. In this study, we first found that sialic acid plays a key role in H-1PV entry. We then genetically engineered the H-1PV capsid to improve its affinity for human tumor cells. By analogy with the resolved crystal structure of the closely related parvovirus minute virus of mice, we developed an in silico three-dimensional (3D) model of the H-1PV wild-type capsid. Based on this model, we identified putative amino acids involved in cell membrane recognition and virus entry at the level of the 2-fold axis of symmetry of the capsid, within the so-called dimple region. In situ mutagenesis of these residues significantly reduced the binding and entry of H-1PV into permissive cells. We then engineered an entry-deficient viral capsid and inserted a cyclic RGD-4C peptide at the level of its 3-fold axis spike. This peptide binds α(v)ß(3) and α(v)ß(5) integrins, which are overexpressed in cancer cells and growing blood vessels. The insertion of the peptide rescued viral infectivity toward cells overexpressing α(v)ß(5) integrins, resulting in the efficient killing of these cells by the reengineered virus. This work demonstrates that H-1PV can be genetically retargeted through the modification of its capsid, showing great promise for a more efficient use of this virus in cancer therapy.

Phase I/IIa study of intratumoral/intracerebral or intravenous/intracerebral administration of Parvovirus H-1 (ParvOryx) in patients with progressive primary or recurrent glioblastoma multiforme: ParvOryx01 protocol.

BACKGROUND: The treatment of patients with malignant brain tumors remains a major oncological problem. The median survival of patients with glioblastoma multiforme (GBM), the most malignant type, is only 15 months after initial diagnosis and even less after tumor recurrence. Improvements of standard treatment including surgery and radio-chemotherapy have not lead to major improvements. Therefore, alternative therapeutics such as oncolytic viruses that specifically target and destroy cancer cells are under investigation. Preclinical data of oncolytic parvovirus H-1 (H-1PV) infection of glioma cells demonstrated strong cytotoxic and oncosuppressing effects, leading to a phase I/IIa trial of H-1PV in patients with recurrent GBM (ParvOryx01). ParvOryx01 is the first trial with a replication competent oncolytic virus in Germany. METHODS: ParvOryx01 is an open, non-controlled, two groups, intra-group dose escalation, single center, phase I/IIa trial. 18 patients with recurrent GBM will be treated in 2 groups of 9 patients each. Treatment group 1 will first receive H-1PV by intratumoral injection and second by administration into the walls of the tumor cavity during tumor resection. In treatment group 2 the virus will initially be injected intravenously and afterwards, identical to group 1, into the surrounding brain tissue during tumor removal. Main eligibility criteria are: age of 18 years, unifocal recurrent GBM, amenable to complete or subtotal resection. Dose escalation will be based on the Continual Reassessment Method. The primary objective of the trial is local and systemic safety and tolerability and to determine the maximum tolerated dose (MTD). Secondary objectives are proof of concept (PoC) and Progression-free Survival (PFS) up to 6 months. DISCUSSION: This is the first trial with H-1PV in patients with recurrent GBM. The risks for the participants appear well predictable and justified. Furthermore, ParvOryx01 will be the first assessment of combined intratumoral and intravenous application of an oncolytic virus. Due to its study design the trial will not only generate data on the local effect of H-1PV but it will also investigate the penetration of H-1PV into the tumor after systemic delivery and obtain safety data from systemic delivery possibly supporting clinical trials with H-1PV in other, non-CNS malignancies. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01301430.

Activation of the human immune system by chemotherapeutic or targeted agents combined with the oncolytic parvovirus H-1.

BACKGROUND: Parvovirus H-1 (H-1PV) infects and lyses human tumor cells including melanoma, hepatoma, gastric, colorectal, cervix and pancreatic cancers. We assessed whether the beneficial effects of chemotherapeutic agents or targeted agents could be combined with the oncolytic and immunostimmulatory properties of H-1PV. METHODS: Using human ex vivo models we evaluated the biological and immunological effects of H-1PV-induced tumor cell lysis alone or in combination with chemotherapeutic or targeted agents in human melanoma cells +/- characterized human cytotoxic T-cells (CTL) and HLA-A2-restricted dendritic cells (DC). RESULTS: H-1PV-infected MZ7-Mel cells showed a clear reduction in cell viability of >50%, which appeared to occur primarily through apoptosis. This correlated with viral NS1 expression levels and was enhanced by combination with chemotherapeutic agents or sunitinib. Tumor cell preparations were phagocytosed by DC whose maturation was measured according to the treatment administered. Immature DC incubated with H-1PV-induced MZ7-Mel lysates significantly increased DC maturation compared with non-infected or necrotic MZ7-Mel cells. Tumor necrosis factor-α and interleukin-6 release was clearly increased by DC incubated with H-1PV-induced SK29-Mel tumor cell lysates (TCL) and was also high with DC-CTL co-cultures incubated with H-1PV-induced TCL. Similarly, DC co-cultures with TCL incubated with H-1PV combined with cytotoxic agents or sunitinib enhanced DC maturation to a greater extent than cytotoxic agents or sunitinib alone. Again, these combinations increased pro-inflammatory responses in DC-CTL co-cultures compared with chemotherapy or sunitinib alone. CONCLUSIONS: In our human models, chemotherapeutic or targeted agents did not only interfere with the pronounced immunomodulatory properties of H-1PV, but also reinforced drug-induced tumor cell killing. H-1PV combined with cisplatin, vincristine or sunitinib induced effective immunostimulation via a pronounced DC maturation, better cytokine release and cytotoxic T-cell activation compared with agents alone. Thus, the clinical assessment of H-1PV oncolytic tumor therapy not only alone but also in combination strategies is warranted.

Human Retrotransposons and the Global Shutdown of Homeostatic Innate Immunity by Oncolytic Parvovirus H-1PV in Pancreatic Cancer.

Although the oncolytic parvovirus H-1PV has entered clinical trials, predicting therapeutic success remains challenging. We investigated whether the antiviral state in tumor cells determines the parvoviral oncolytic efficacy. The interferon/interferon-stimulated genes (IFN/ISG)-circuit and its major configurator, human endogenous retroviruses (HERVs), were evaluated using qRT-PCR, ELISA, Western blot, and RNA-Seq techniques. In pancreatic cancer cell lines, H-1PV caused a late global shutdown of innate immunity, whereby the concomitant inhibition of HERVs and IFN/ISGs was co-regulatory rather than causative. The growth-inhibitory IC50 doses correlated with the power of suppression but not with absolute ISG levels. Moreover, H-1PV was not sensitive to exogenous IFN despite upregulated antiviral ISGs. Such resistance questioned the biological necessity of the oncotropic ISG-shutdown, which instead might represent a surrogate marker for personalized oncolytic efficacy. The disabled antiviral homeostasis may modify the activity of other viruses, as demonstrated by the reemergence of endogenous AluY-retrotransposons. This way of suppression may compromise the interferogenicity of drugs having gemcitabine-like mechanisms of action. This shortcoming in immunogenic cell death induction is however amendable by immune cells which release IFN in response to H-1PV.

Phase 2 Trial of Oncolytic H-1 Parvovirus Therapy Shows Safety and Signs of Immune System Activation in Patients With Metastatic Pancreatic Ductal Adenocarcinoma.

PURPOSE: To investigate the safety, clinical efficacy, virus pharmacokinetics, shedding, and immune response after administration of an oncolytic parvovirus (H-1PV, ParvOryx) to patients with metastatic pancreatic ductal adenocarcinoma (PDAC) refractory to first-line therapy. PATIENTS AND METHODS: This is a noncontrolled, single-arm, open-label, dose-escalating, single-center clinical trial. Seven patients with PDAC and at least one liver metastasis were included. ParvOryx was administered intravenously on 4 consecutive days and as an intralesional injection, 6 to 13 days thereafter. Altogether, three escalating dose levels were investigated. In addition, gemcitabine treatment was initiated on day 28. RESULTS: ParvOryx showed excellent tolerability with no dose-limiting toxicities. One patient had a confirmed partial response and one patient revealed an unconfirmed partial response according to RECIST criteria. Both patients showed remarkably long surivial of 326 and 555 days, respectively. Investigation of pharmacokinetics and virus shedding revealed dose dependency with no excretion of active virus particles in saliva or urine and very limited excretion in feces. H-1PV nucleic acids were detected in tumor samples of four patients. All patients showed T-cell responses to viral proteins. An interesting immunologic pattern developed in tumor tissues and in blood of both patients with partial response suggesting immune activation after administration of ParvOryx. CONCLUSIONS: The trial met all primary objectives, revealed no environmental risks, and indicated favorable immune modulation after administration of ParvOryx. It can be considered a good basis for further systematic clinical development alone or in combination with immunomodulatory compounds.

Temporal multi-omics identifies LRG1 as a vascular niche instructor of metastasis.

Metastasis is the primary cause of cancer-related mortality. Tumor cell interactions with cells of the vessel wall are decisive and potentially rate-limiting for metastasis. The molecular nature of this cross-talk is, beyond candidate gene approaches, hitherto poorly understood. Using endothelial cell (EC) bulk and single-cell transcriptomics in combination with serum proteomics, we traced the evolution of the metastatic vascular niche in surgical models of lung metastasis. Temporal multiomics revealed that primary tumors systemically reprogram the body's vascular endothelium to perturb homeostasis and to precondition the vascular niche for metastatic growth. The vasculature with its enormous surface thereby serves as amplifier of tumor-induced instructive signals. Comparative analysis of lung EC gene expression and secretome identified the transforming growth factor­ß (TGFß) pathway specifier LRG1, leucine-rich alpha-2-glycoprotein 1, as an early instructor of metastasis. In the presence of a primary tumor, ECs systemically up-regulated LRG1 in a signal transducer and activator of transcription 3 (STAT3)­dependent manner. A meta-analysis of retrospective clinical studies revealed a corresponding up-regulation of LRG1 concentrations in the serum of patients with cancer. Functionally, systemic up-regulation of LRG1 promoted metastasis in mice by increasing the number of prometastatic neural/glial antigen 2 (NG2)+ perivascular cells. In turn, genetic deletion of Lrg1 hampered growth of lung metastasis. Postsurgical adjuvant administration of an LRG1-neutralizing antibody delayed metastatic growth and increased overall survival. This study has established a systems map of early primary tumor-induced vascular changes and identified LRG1 as a therapeutic target for metastasis.

Parvovirus H1 selectively induces cytotoxic effects on human neuroblastoma cells.

Despite multimodal therapeutic concepts, advanced localized and high-risk neuroblastoma remains a therapeutic challenge with a long-term survival rate below 50%. Consequently, new modalities for the treatment of neuroblastoma, e.g., oncolytic virotherapy are urgently required. H-1PV is a rodent parvovirus devoid of relevant pathogenic effects in infected adult animals. In contrast, the virus has oncolytic properties and is particularly cytotoxic for transformed or tumor-derived cells of various species including cells of human origin. Here, a preclinical in vitro assessment of the application of oncolytic H-1PV for the treatment of neuroblastoma cells was performed. Infection efficiency, viral replication and lytic activity of H-1PV were analyzed in 11 neuroblastoma cell lines with different MYCN status. Oncoselectivity of the virus was confirmed by the infection of short term cultures of nonmalignant infant cells of different origin. In these nontransformed cells, no effect of H-1PV on viability or morphology of the cells was observed. In contrast, a lytic infection was induced in all neuroblastoma cell lines examined at MOIs between 0.001 and 10 pfu/cell. H-1PV actively replicated with virus titres increasing up to 5,000-fold within 48-96 hr after infection. The lytic effect of H-1PV was observed independent of MYCN oncogene amplification or differentiation status. Moreover, a significant G2-arrest and induction of apoptosis could be demonstrated. Infection efficiency, rapid virus replication and exhaustive lytic effects on neuroblastoma cells together with the low toxicity of H-1PV for nontransformed cells, render this parvovirus a promising candidate for oncolytic virotherapy of neuroblastoma.

Improvement of gemcitabine-based therapy of pancreatic carcinoma by means of oncolytic parvovirus H-1PV.

UNLABELLED: Pancreatic carcinoma is a gastrointestinal malignancy with poor prognosis. Treatment with gemcitabine, the most potent chemotherapeutic against this cancer up to date, is not curative, and resistance may appear. Complementary treatment with an oncolytic virus, such as the rat parvovirus H-1PV, which is infectious but nonpathogenic in humans, emerges as an innovative option. PURPOSE: To prove that combining gemcitabine and H-1PV in a model of pancreatic carcinoma may reduce the dosage of the toxic drug and/or improve the overall anticancer effect. EXPERIMENTAL DESIGN: Pancreatic tumors were implanted orthotopically in Lewis rats or subcutaneously in nude mice and treated with gemcitabine, H-1PV, or both according to different regimens. Tumor size was monitored by micro-computed tomography, whereas bone marrow, liver, and kidney functions were monitored by measuring clinically relevant markers. Human pancreatic cell lines and gemcitabine-resistant derivatives were tested in vitro for sensitivity to H-1PV infection with or without gemcitabine. RESULTS: In vitro studies proved that combining gemcitabine with H-1PV resulted in synergistic cytotoxic effects and achieved an up to 15-fold reduction in the 50% effective concentration of the drug, with drug-resistant cells remaining sensitive to virus killing. Toxicologic screening showed that H-1PV had an excellent safety profile when applied alone or in combination with gemcitabine. The benefits of applying H-1PV as a second-line treatment after gemcitabine included reduction of tumor growth, prolonged survival of the animals, and absence of metastases on CT-scans. CONCLUSION: In addition to their potential use as monotherapy for pancreatic cancer, parvoviruses can be best combined with gemcitabine in a two-step protocol.

Fluorescence In Situ Hybridization (FISH) Detection of Viral Nucleic Acids in Oncolytic H-1 Parvovirus-Treated Human Brain Tumors.

Fluorescence in situ hybridization (FISH) is a specific, sensitive, accurate, and reliable technique widely applied in both research and clinic. Here we describe the detailed protocol of a FISH method established by us to serve the scientific purposes of the first oncolytic parvovirus clinical trial (ParvOryx01). This trial was launched in Germany in 2011. After trial completion in 2015, results were published in Molecular Therapy in 2017. The primary purpose of the trial was to evaluate the safety of an oncolytic parvovirus, H-1PV (ParvOryx), in recurrent glioblastoma patients. In addition, the efficiency of H-1PV tumor targeting after intratumoral or systemic virus administration was assessed by FISH detection of viral nucleic acids (genomic single-stranded DNA, mRNA and parvovirus double-stranded replicative forms) in formalin-fixed paraffin-embedded glioblastoma tissues resected at day 10 after ParvOryx treatment. The FISH method allowed the detection-for the first time in humans-of H-1PV replication markers in brain tumors of parvovirus-treated patients. A protocol combining mRNA FISH with simultaneous immunofluorescent staining for tumor and tumor microenvironment markers was also developed and is described here, in order to better characterize H-1PV cellular targets and H-1PV treatment-associated tumor microenvironment changes.

Various effects of AAV9-mediated ßARKct gene therapy on the heart in dystrophin-deficient (mdx) mice and δ-sarcoglycan-deficient (Sgcd-/-) mice.

So far effective strategies to treat cardiomyopathy in patients with muscular dystrophies are still not clearly defined. Previously, treatment with ß-blockers showed beneficial effects on the development of cardiomyopathy in dystrophin-deficient (mdx) mice, but not in δ-sarcoglycan-deficient (Sgcd-/-) mice. We therefore aimed to study a more specific approach to target maladaptive ß-adrenergic signalling in these mice. It has been shown that lowering cardiac G-protein-coupled-receptor-kinase-2 (GRK2) activity with ßARKct expression, a peptide inhibitor of protein-coupled-receptor-kinase-2 (GRK2), results in improvement of heart failure in several different animal models. We therefore investigated whether adeno-associated virus type 9 (AAV9)-mediated gene delivery of ßARKct, could ameliorate cardiac pathology in mdx and Sgcd-/- mice. We found that long-term treatment with AAV9- ßARKct-cDNA with a cardiac-specific promoter significantly improves left ventricular systolic function and reduces myocardial hypertrophy in mdx mice, whereas only mild beneficial effects on cardiac function is observed in Sgcd-/- mice. Interestingly, in contrast to mdx mice neither GRK2 nor nuclear-factor-kappaB (NFκB) were upregulated in Sgcd-/- mice. Taken together, effectiveness of AAV-mediated ßARKct therapy may vary between different genetic mutations and presumably depend on the state of adrenergic dysregulation mediated through the upregulation of GRK2.

Arming parvoviruses with CpG motifs to improve their oncosuppressive capacity.

Oncolytic viruses represent novel tools for cancer treatment. Besides specifically killing cancer cells (oncolysis), these agents also provide danger signals, prompting the immune system to eliminate virus-infected tumours. As a consequence of oncolytic events, the innate and adaptive immune systems gain access to tumour antigens, which result in cross-priming and vaccination effects. Here the aim was to see whether we could enhance this adjuvant capacity by incorporating immunostimulatory CpG motifs into the single-stranded genome of an oncolytic parvovirus (H-1PV). We engineered 2 CpG-enriched H-1PV variants (JabCG1 and JabCG2), preserving both the replication competence and the oncolytic features of the parental virus. In keeping with their increased CpG content, the JabCG1 and JabCG2 genomes proved in vitro to be more potent triggers of TLR-9-mediated signalling than wild-type H-1PV DNA. Antitumour activity was evaluated in a rat model of MH3924A hepatoma lung metastases, where an infection with parental or modified viruses served as an ex vivo adjuvant to a subcutaneously administered autologous cell vaccine. In this setup, which excludes direct oncolytic effects on metastases, the JabCG2 vector displayed enhanced immunogenicity, inducing markers of cellular immunity (IFN gamma) and dendritic cell activation (CD80, CD86) in mediastinal (tumour-draining) lymph nodes. This led to a significantly reduced metastatic rate (50%) as compared to other vaccination schedules (H-1PV-, JabCG1-, JabGC- or mock-treated cells). The data provide proof of principle that increasing the number of immunostimulatory CpG motifs within oncolytic viruses makes it possible to improve their overall anticancer effect by inducing antitumour vaccination.

Killing of p53-deficient hepatoma cells by parvovirus H-1 and chemotherapeutics requires promyelocytic leukemia protein.

AIM: To evaluate the synergistic targeting and killing of human hepatocellular carcinoma (HCC) cells lacking p53 by the oncolytic autonomous parvovirus (PV) H-1 and chemotherapeutic agents and its dependence on functional promyelocytic leukemia protein (PML). METHODS: The role of p53 and PML in regulating cytotoxicity and gene transfer mediated by wild-type (wt) PV H-1 were explored in two pairs of isogenic human hepatoma cell lines with different p53 status. Furthermore, H-1 PV infection was combined with cytostatic drug treatment. RESULTS: While the HCC cells with different p53 status studied were all susceptible to H-1 PV-induced apoptosis, the cytotoxicity of H-1 PV was more pronounced in p53-negative than in p53-positive cells. Apoptosis rates in p53-negative cell lines treated by genotoxic drugs were further enhanced by a treatment with H-1 PV. In flow cytometric analyses, H-1 PV infection resulted in a reduction of the mitochondrial transmembrane potential. In addition, H-1 PV cells showed a significant increase in PML expression. Knocking down PML expression resulted in a striking reduction of the level of H-1 PV infected tumor cell death. CONCLUSION: H-1 PV is a suitable agent to circumvent the resistance of p53-negative HCC cells to genotoxic agents, and it enhances the apoptotic process which is dependent on functional PML. Thus, H-1 PV and its oncolytic vector derivatives may be considered as therapeutic options for HCC, particularly for p53-negative tumors.