Long-term antigen-specific immune response by an oncolytic adenovirus encoding SP-SA-E7-4-1BBL in HPV-16 cancer model

BACKGROUND

To describe an oncolytic adenovirus (OAd) encoding SP-SA-E7-4-1BBL that is capable of inducing tumor regression in therapeutic assays. Herein, we tested whether the antitumor effect is given by the induction of a tumor-specific immune response, as well as the minimum dose needed to elicit antitumor protection and monitor the OAd biodistribution over time.

METHODS AND RESULTS

C57BL/6 mice (n = 5) per group were immunized twice with OAds encoding SP-SA-E7-4-1BBL, SA-E7-4-1BBL, or SP-SA-4-1BBL and challenged with TC-1 cancer cells. The DNA construct SP-SA-E7-4-1BBL was employed as a control via biolistic or PBS injection. Groups without tumor development at 47 days were rechallenged with TC-1 cells, and follow-up lasted until day 90. The minimum dose of OAd to induce the antitumor effect was established by immunization using serial dilution doses. The cytometry bead assay and the ELISpot assay were used to evaluate cytokine release in response to ex vivo antigenic stimulation. The distribution profile of the OAd vaccine was evaluated in the different organs by histological, immunohistochemical and qPCR analyses. The OAd SP-SA-E7-4-1BBL-immunized mice did not develop tumors even in a rechallenge. A protective antitumor effect was observed from a dose that is one hundredth of most reports of adenoviral vaccines. Immunization with OAd increases Interferon-gamma-producing cells in response to antigen stimulation. OAd was detected in tumors over time, with significant morphological changes, contrary to nontumor tissues.

CONCLUSIONS

The OAd SP-SA-E7-4-1BBL vaccine confers a prophylactic, safe, long-lasting, and antigen-dependent antitumor effect mediated by a Th1 antitumor immune response.

Abstract 692: OAd-mediated SA-4-1BBL fused to HPV-16 E7 elicits specific antitumor efficacy in syngeneic mouse lung cancer model

Introduction: Human papillomaviruses (HPVs) are responsible for about 25% of cancer cases worldwide. HPV-16 E7 antigen is a tumor-associated antigen (TAA) commonly expressed in HPV-induced tumors; however, it has low immunogenicity. The interaction of 4-1BBL with its receptor induces pleiotropic effects on innate, adaptive, and regulatory immunity and, if fused to TAAs in DNA vaccines, can improve the antitumor response; however, there is low transfection and antitumor efficiency. Oncolytic virotherapy is promising for antitumor gene therapy as it can be selectively replicated in tumor cells, inducing cell lysis, and furthermore, tumor cell debris can be taken in by immune cells to potentiate antitumor responses.

Methods: The AdenoQuick 2.0 system was used to construct three OAds, expressing 1) SP-SA-E7-4-1BBL, 2) SA-E7-4-1BBL or 3) SP-SA-41BBL. The expression of transgenes was confirmed by western blot and subcellular localization of SP-SA-E7-4-1BBL was evaluated by immunofluorescence. The recombinant OAds-mediated cancer killing effect was evaluated by MTT assay and crystal violet staining, The recombinant OAds therapeutic efficacy was evaluated in a C57BL/6 mice bearing subcutaneous TC-1 lung tumor. Tumor growth and survival were monitored for a period of twenty-eight days.

Results: In this study, we expressed the immunomodulatory molecule SA-4-1BBL fused to E7 on an oncolytic adenovirus (OAd) system. In vitro infection of TC-1 tumor cells and NIH-3T3 non-tumor cells with SA/E7/4-1BBL OAd demonstrated that only tumor cells are selectively destroyed. Moreover, protein expression is targeted to the endoplasmic reticulum in both cell lines when a signal peptide (SP) is added. Finally, in an HPV-induced cancer murine model, the therapeutic oncolytic activity of OAd can be detected, and this can be improved when fused to E7 and SP.

Conclusions: In this study, we report the design of an oncolytic adenovirus expressing the SP/SA/E7/4-1BBL fusion gene, which is capable of infecting murine cancer and normal cells, and the expressed protein was able to be targeted to the endoplasmic reticulum. Most importantly, OAd induced a cell killing effect that is specific to cancer cells. Moreover, OAd treatment induced a potent antitumor effect in a mouse TC-1 cancer model.

Citation Format: Jorge G. Gomez-Gutierrez, Rodolfo Garza-Morales, Alejandra G. Martinez-Perez, Jose J. Perez-Trujillo, Odila Saucedo-Cardenas, Maria J. Loera-Arias, Roberto Montes-de-Oca-Luna. OAd-mediated SA-4-1BBL fused to HPV-16 E7 elicits specific antitumor efficacy in syngeneic mouse lung cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 692.