Abstract 927: Gut microbiome changes are associated with the efficacy of Delta-24-RGDOX viroimmunotherapy against malignant glioma
Authors: Gomez-Manzano Candelaria , Melendez-Vazquez Natalie M. , Nguyen Teresa , Ossimetha Ashley , Jiang Hong , Fueyo Juan , Godoy-Vitorino Filipa 
Published: July 2021

Malignant gliomas are devastating diseases that require new and more effective treatments. To improve clinical outcomes, our laboratories have developed an oncolytic adenovirus armed with the T-cell activator OX40L, named Delta-24-RGDOX. Here, we evaluated changes to gut microbiome in glioma bearing mice treated with viroimmunotherapy. GL261 glioblastoma cells were implanted in the brain of immunocompetent C57BL/6 mice. Then mice were treated with intratumoral injections of control (PBS) or a combination of Delta-24-RGDOX and Indoximod, an inhibitor of the immune modulator IDO. The combined immunotherapy prolonged mice overall survival with the production of long-term survivors (&gt;100 days). We also performed a similar set of experiments in mice with depleted CD4+ T cell. Genomic DNA was isolated with the Powerlyzer kit from fecal pellets collected from glioma-bearing mice (n=15), followed by sequencing of the 16S ribosomal RNA V4 region (prokaryotes) and ITS-2 region (for fungi) using the Illumina platform. Data was analyzed at first and deposited in Qiita, the taxonomic reference was the SILVA database, and community analyses were performed in QIIME and R with a rarefaction depth of 27,000 reads for 16S and 500 reads for ITS. We found significant differences in the gut microbiome community structure of viroimmunotherapy-treated animals compared to those with depleted CD4+ T cells and controls which shared similarities (PERMANOVA p&lt;0.001). The highest gut diversity was observed in viroimmunotherapy in animals in which the T cell populations were not depleted which also corresponded to long-term survivors (KW p=0.006). The gut bacterial community structure of viroimmunotherapy-treated animals without T-cell depletion showed an increase in Actinobacteria compared to control-treated mice and those with shorter survival. In fact, we found significantly higher amounts of Bifidobacterium and Lactobacillus in the viroimmunotherapy-treated mice while Moryella were more dominant in the control groups (WRST p&lt;0.05). We did not find significant differences in structure nor diversity of the fungal communities which were dominated by Ascomycota with Alternaria and Fusarium. However, control-treated animals had higher amounts of Aspergillus while Trichoderma were increased in viroimmunotherapy-treated mice.Our data suggests that bacterial communities play an important role in modulating viroimmunotherapy against glioma in immunocompetent animal glioma models. Importantly, increase in Bifidobacterium and Lactobacillus was associated with a better response to the therapy, likely strengthening antitumor immunity and raising efficacy in viroimmunotherapy-treated mice. This reveals the benefits of gut microbiome therapeutics in positively influencing the final clinical outcome of viroimmunotherapy. Sponsored by NCI's 2U54CA096297-16.

Citation Format: Candelaria Gomez-Manzano, Natalie M. Melendez-Vazquez, Teresa Nguyen, Ashley Ossimetha, Hong Jiang, Juan Fueyo, Filipa Godoy-Vitorino. Gut microbiome changes are associated with the efficacy of Delta-24-RGDOX viroimmunotherapy against malignant glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 927.