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A new insight into aggregation of oncolytic adenovirus Ad5-delta-24-RGD during CsCl gradient ultracentrifugation.

ABSTRACT: Two-cycle cesium chloride (2 × CsCl) gradient ultracentrifugation is a conventional approach for purifying recombinant adenoviruses (rAds) for research purposes (gene therapy, vaccines, and oncolytic vectors). However, rAds containing the RGD-4C peptide in the HI loop of the fiber knob domain tend to aggregate during 2 × CsCl gradient ultracentrifugation resulting in a low infectious titer yield or even purification failure. An iodixanol-based purification method preventing aggregation of the RGD4C-modified rAds has been proposed. However, the reason explaining aggregation of the RGD4C-modified rAds during 2 × CsCl but not iodixanol gradient ultracentrifugation has not been revealed. In the present study, we showed that rAds with the RGD-4C peptide in the HI loop but not at the C-terminus of the fiber knob domain were prone to aggregate during 2 × CsCl but not iodixanol gradient ultracentrifugation. The cysteine residues with free thiol groups after the RGD motif within the inserted RGD-4C peptide were responsible for formation of the interparticle disulfide bonds under atmospheric oxygen and aggregation of Ad5-delta-24-RGD4C-based rAds during 2 × CsCl gradient ultracentrifugation, which could be prevented using iodixanol gradient ultracentrifugation, most likely due to antioxidant properties of iodixanol. A cysteine-to-glycine substitution of the cysteine residues with free thiol groups (RGD-2C2G) prevented aggregation during 2 × CsCl gradient purification but in coxsackie and adenovirus receptor (CAR)-low/negative cancer cell lines of human and rodent origin, this reduced cytolytic efficacy to the levels observed for a fiber non-modified control vector. However, both Ad5-delta-24-RGD4C and Ad5-delta-24-RGD2C2G were equally effective in the murine immunocompetent CT-2A glioma model due to a primary role of antitumor immune responses in the therapeutic efficacy of oncolytic virotherapy.

SUBMITTER: Stepanenko AA

PROVIDER: S-EPMC8352973 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Abstract BACKGROUND Atypical teratoid/rhabdoid tumors (AT/RTs) are rare pediatric brain tumors affecting mainly infants and young children. However, AT/RTs encompass almost 10% of death caused by pediatric brain tumors, and the 2-year overall survival for these children remains below 20%. For this reason, AT/RT ranks among the deadliest pediatric brain tumors. Therefore, it is clear we need to find out new therapeutic options for these children. Delta-24-RGD is an oncolytic adenovirus that has already demonstrated its efficacy as in Phase I/II clinical trials in adult patients affected by high grade gliomas with no evidence of severe side effects. Of interest for pediatric brain tumors, the safety of Delta-24-RGD is has also been demonstrated in an ongoing Phase I clinical trial for the treatment of DIPGs (NCT03178032). For these reasons, we propose to evaluate the anti-tumor effect of Delta-24-RGD in preclinical models of ATRT. MATERIAL AND METHODS Our studies have been carried out in three stablished AT/RT cell lines (BT-12, CHLA-06 and CHLA-266). In vitro, AT/RT cultures were infected with Delta-24-RGD-GFP to confirm the infectivity of the virus by flow cytometry. Replication of Delta-24-RGD was ensured by titrating the PFUs generated in AT/RT infected cultures. In regard to cytolytic effect, viability assays (MTS) were conducted in AT/RT cultures infected at increasing MOIs of Delta-24-RGD. In vivo, AT/RT cell lines were engrafted in Rag-2 mice in supratentorial and infratentorial locations, and the animals were treated with Delta-24-RGD at 107 or 108 PFU/animal (intra-tumor administration), or PBS. The therapeutic benefit of Delta-24-RGD was evaluated comparing the overall survival obtained for treated and untreated animals using the Log-rank test. We have also generated models of disseminated disease through intraventricular injection of the tumor cells, thus mimicking the lesions found in patients. AT/RT cell lines were transduced with a luc-expressing lentivirus to facilitate the follow up of these tumors. Mice bearing disseminated AT/RT were treated with Delta-24-RGD at 107 or 108 PFU/animal, or PBS (control). The therapeutic effect was monitored by bioluminescence and by comparison of the survival curves (Log-rank). RESULTS The virus was able to infect and replicate in tumor three different cell culture models of AT/RT, inducing a potent cytotoxic effect that resulting in IC50 values below 1 PFU/cell. Administration of the virus in mice bearing localized AT/RT (supratentorial and infratentorial) extended significantly the survival the animals, leading to up to 20% of long-term survivors. In disseminated AT/RT models, light emission reveals reduction of tumor growth in virus treated animals, resulting in an increased overall survival. CONCLUSION In conclusion, these results demonstrate that Delta-24-RGD could be a feasible therapeutic choice for patients affected by AT/RT.

Project description:Abstract Based on promising results of recent clinical trials using oncolytic viruses, virotherapy is evolving as an alternative to treat patients with malignant glioma. Our group developed the oncolytic adenovirus Delta-24-RGD (DNX-2401) that is being tested, alone or in combination with anti-PD1, in clinical trials for recurrent glioblastoma (NCT00805376; NCT01956734; NCT02798406). The results suggest that, besides the expected oncolytic effect, the injection of the pathogen initiated, in a subset of patients, an anti-tumoral immunity that led to 20% of long-term survivors (3.5–5 years). To further enhance this effect, we have armed Delta-24-RGD to express the co-stimulatory ligand GITRL, and generated Delta-24-GREAT. The intracranial injection of Delta-24-GREAT prolonged the survival of GL261 glioma-bearing immunocompetent mice when compared to Delta-24-RGD treatment (P=0.002, log-rank test). Delta-24-GREAT treatment resulted in enhanced frequency of tumor-infiltrating lymphocytes: T lymphocytes (CD45+/CD3+) and cytotoxic T lymphocytes (CD45+CD3+CD8+). Functional studies performed by culturing splenocytes from Delta-24-GREAT-treated mice with glioma cells and analyzing secretion of Th1 cytokines, such as IL2 and IFN-?, showed that lymphocytes recognized not only viral antigens but also tumoral antigens, suggesting the triggering of anti-tumoral immunity. Of interest, Delta-24-GREAT treatment resulted in an antigen-restricted anti-tumor memory effect and in the generation of central immune memory. Thus, rechallenging the survivor mice from the first experiment with a second implantation of glioma cells did not lead to tumor growth, and we detected an increased frequency of central memory CD8+ T cells (CD45+CD62L+). However, survivor mice developed lethal tumors when implanted intracranially with B16/F10 melanoma cells, strongly indicating that the developed immune response was specific for GL261 glioma antigens. This is a novel approach using an oncolytic adenovirus expressing GITRL to target cancer and to stimulate the immunity within the tumor. Our data strongly indicate that this type of strategy may be further developed to treat patients with malignant glioblastoma.

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A new insight into aggregation of oncolytic adenovirus Ad5-delta-24-RGD during CsCl gradient ultracentrifugation.

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