Characterization of Oncolytic Vaccinia Virus Harboring the Human IFNB1 and CES2 Transgenes

Abstract

The purpose of this study was to assess characteristics of SJ-815, a novel oncolytic vaccinia virus lacking a functional thymidine kinase-encoding TK gene, and instead, having two human transgenes: the IFNB1 that encodes interferon 1, and the CES2 that encodes carboxylesterase 2, which metabolizes the prodrug, irinotecan, into cytotoxic SN-38. Materials and Methods Viral replication and dissemination of SJ-815 were measured by plaque assay and comet assay, respectively, and compared to the backbone of SJ-815, a modified Western Reserve virus named WI. Tumor cytotoxicity of SJ-815 (or mSJ-815, which has the murine IFNB1 transgene for mouse cancers) was evaluated using human and mouse cancer cells. Antitumor effects of SJ-815, with/without irinotecan, were evaluated using a human pancreatic cancer-bearing mouse model and a syngeneic melanoma-bearing mouse model. The SN-38/ irinotecan ratios in mouse melanoma tissue 4 days post irinotecan treatment were compared between groups with and without SJ-815 intravenous injection. Results SJ-815 demonstrated significantly lower viral replication and dissemination, but considerably stronger in vitro tumor cytotoxicity than WI. The combination use of SJ-815 plus irinotecan generated substantial tumor regression in the human pancreatic cancer model, and significantly prolonged survival in the melanoma model (hazard ratio, 0.11; 95% confidence interval, 0.02 to 0.50; p=0.013). The tumor SN-38/irinotecan ratios were over 3-fold higher in the group with SJ-815 than those without (p < 0.001). Conclusion SJ-815 demonstrates distinct characteristics gained from the inserted IFNB1 and CES2 transgenes. The potent antitumor effects of SJ-815, particularly when combined with irinotecan, against multiple solid tumors make SJ-815 an attractive candidate for further preclinical and clinical studies.

Engineering and Characterization of Oncolytic Vaccinia Virus Expressing Truncated Herpes Simplex Virus Thymidine Kinase

“…The virus dosages used in this study (10 6 PFU for IT and 10 8 PFU for IP) were based on our previous studies on other OVVs [11,12]. The GCV dosages that were used in this study (25 and 50 mg/kg/day) were commonly adopted by many other animal studies [44,45] and, according to a widely used human-animal drug dose translation equation [46], mouse dose of 50 mg/kg/day is equivalent to the recommended maintenance dosages for humans, which is around 5 mg/kg/day.…”

“…Safety was a major consideration in developing engineering strategies for the new OVV that was described in this paper. VACV thymidine kinase (VV-tk) gene was deleted to enhance tumor selectivity to address concerns of uncontrolled replication in non-target tissues, as described in our other OVV projects [11,12], and herpes simplex virus (type 1) thymidine kinase (HSV-tk) transgene was inserted for viral replication control. The rationale supporting these strategies is, as follows: first, because of the high level of shared homology between the VV-tk gene and the human thymidine kinase 1 (TK1) gene, VACV lacking a functional tk gene can efficiently replicate in cancer cells, which often express high levels of TK1, a human cytosolic enzyme which plays the primary role in regulating intracellular thymidine pools throughout the cell cycle.…”

“…This distinction cumulatively explains why HSV is sensitive to GCV, a purine analogue, while VACV is not [21]. However, the insertion of the wild-type HSV-tk gene into the VV-tk region of an OVV may raise concern for impaired tumor selectivity, while considering that the HSV-tk can also catalyze thymidine (a pyrimidine deoxynucleoside), since VV-tk gene deletion results in tumor selectivity [11,12,22]. Therefore, in this study, an artificial selection procedure while using bromodeoxyuridine (BrdU) was adopted to exclude any HSV-tk incorporated recombinant viruses expressing thymidine kinase activity.…”

STING activation normalizes the intraperitoneal vascular-immune microenvironment and suppresses peritoneal carcinomatosis of colon cancer

“…[19][20][21][22][23] Moreover, STING signaling is also involved in the regulation of the tumor vasculature in various malignancies and can stimulate tumor endothelial cells to secrete type-I IFNs, triggering spontaneous and therapeutic antitumor immunity within the TME. [24][25][26][27] Additionally, recent studies unveiled that intratumoral STING activation can remodel the phenotype of the tumor vasculature to enhance endothelial-lymphocyte interactions and facilitate intratumoral trafficking of CD8 + T cells. 24 27 28 Here, we elucidated the establishment of a highly angiogenic and immunosuppressive milieu within the peritoneal cavity during peritoneal dissemination of colon cancer.…”

Oncolytic Vaccinia Virus Gene Modification and Cytokine Expression Effects on Tumor Infection, Immune Response, and Killing

“…Vaccinia viruses are promising for treatment of poorly immunogenic tumors because their large genome can accommodate mutations and transgenes, and they target tumors after intravenous (iv) administration (1,3,5), Many vaccinia virus variants have been created to boost antitumor activity. Genetic changes have been made to increase viral replication and spread in tumors and for targeted immunotherapy (6)(7)(8). Viral thymidine kinase (TK, J2R gene, VACV-WR94 locus) and vaccinia growth factor have been disrupted by insertional inactivation to favor selective viral replication in tumor cells (7,9).…”