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. 2016 Mar 23:3:16002.
doi: 10.1038/mto.2016.2. eCollection 2016.

Expression of DAI by an oncolytic vaccinia virus boosts the immunogenicity of the virus and enhances antitumor immunity

Mari Hirvinen  1 , Cristian Capasso  1 , Kilian Guse  2 , Mariangela Garofalo  1 , Andrea Vitale  3 , Marko Ahonen  2 , Lukasz Kuryk  4 , Markus Vähä-Koskela  5 , Akseli Hemminki  6 , Vittorio Fortino  7 , Dario Greco  7 , Vincenzo Cerullo  1
Affiliations

Expression of DAI by an oncolytic vaccinia virus boosts the immunogenicity of the virus and enhances antitumor immunity

Mari Hirvinen et al. Mol Ther Oncolytics. .

Abstract

In oncolytic virotherapy, the ability of the virus to activate the immune system is a key attribute with regard to long-term antitumor effects. Vaccinia viruses bear one of the strongest oncolytic activities among all oncolytic viruses. However, its capacity for stimulation of antitumor immunity is not optimal, mainly due to its immunosuppressive nature. To overcome this problem, we developed an oncolytic VV that expresses intracellular pattern recognition receptor DNA-dependent activator of IFN-regulatory factors (DAI) to boost the innate immune system and to activate adaptive immune cells in the tumor. We showed that infection with DAI-expressing VV increases expression of several genes related to important immunological pathways. Treatment with DAI-armed VV resulted in significant reduction in the size of syngeneic melanoma tumors in mice. When the mice were rechallenged with the same tumor, DAI-VV-treated mice completely rejected growth of the new tumor, which indicates immunity established against the tumor. We also showed enhanced control of growth of human melanoma tumors and elevated levels of human T-cells in DAI-VV-treated mice humanized with human peripheral blood mononuclear cells. We conclude that expression of DAI by an oncolytic VV is a promising way to amplify the vaccine potency of an oncolytic vaccinia virus to trigger the innate-and eventually the long-lasting adaptive immunity against cancer.

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Conflict of interest statement

A.H. is employee and shareholder in TILT Biotherapeutics Ltd. and shareholder in Oncos Therapeutics, Ltd. The other authors declare no potential conflict of interest.

Figures

Figure 1
Figure 1
Characteristics of the double deleted oncolytic vaccinia virus expressing DAI. (a) Schematic figures of the virus constructs. Two novel armed vaccinia viruses were generated expressing human (vvdd-tdTomato-hDAI) or murine DAI (vvdd-tdTomato-mDAI). Both viruses express also tdTomato fluorescent protein as a reporter gene and are deleted in thymidine kinase and vaccinia growth factor genes. (b) DAI-expression does not hinder virus replication and cell killing efficacy. MTS cell viability assays were performed in several cell lines 5 days postinfection. Virus expressing human DAI was used for human cell lines and mDAI-virus for the mouse cell line B16-OVA.
Figure 2
Figure 2
Infection of THP-1 monocytes with DAI-armed vaccinia virus results in altered expression pattern of genes involved in biological processes. HS294T melanoma cells and THP-1 monocytes were infected with vvdd-tdTomato-hDAI, vvdd-tdTomato, or phosphate-buffered saline, and the wide genome gene expression profile was analyzed. A BACA clustering representation of the differentially expressed biological processes induced by vvdd-tdTomato and vvdd-tdTomato-hDAI is shown in the two different cell lines. The upregulated genes are marked with red dots and down-regulated genes with green dots.
Figure 3
Figure 3
In vivo efficacy and antitumor immunity elicited after vvdd-tdTomato-mDAI treatment in an immunocompetent syngeneic melanoma model. B16-OVA melanoma tumors were established by injecting 1 × 105 B16-OVA cells subcutaneously into other flank of C57BL/6J mice (N = 12 per group). Established tumors (one tumor per mouse, ~4 × 4 mm in diameter) were injected intratumorally with viruses in volume of 50 μl on day 0 with 3 × 106 pfu/tumor and on day 2 with 1 × 106 pfu/tumor. Mock tumors were injected with phosphate-buffered saline only. (a) Tumor growth was measured over time (day 0 = day when the first virus treatment was given). (b) General CD8+ and CD4+ T-cells and (c) tumor-specific (OVA peptide-specific) CD8+ T-cells were analyzed by flow cytometry from the tumors of treated mice 12 after the first virus treatment.
Figure 4
Figure 4
DAI-virus boosts tumor-specific immunity without boosting anti-viral immunity in mice bearing syngeneic melanoma tumors. (a) Schematic of the experiment; B16-OVA melanoma tumors were established by injecting 1 × 105 B16-OVA cells subcutaneously into other flank of C57BL/6J mice (N = 12 per group). Established tumors (one tumor per mouse, ~4 × 4 mm in diameter) were injected intratumorally with viruses in volume of 50 μl on day 0 with 3 × 106 pfu/tumor and on day 2 with 1 × 106 pfu/tumor. Mock tumors were injected with phosphate-buffered saline only. The mice were re-challenged with another tumor of the same background: the mice received either B16-OVA cells or B16-F10 cells 3 × 105 cells/tumor, 10 days after the first virus treatment. The second tumor was not treated, only tumor growth was followed. (b) Four mice per group were rechallenged with the same tumor cell line (B16-OVA) and (c) four mice per group were rechallenged with a cell line with the same origin but which does not express ovalbumin (B16-F10). The mean tumor growth (above) and the growth of individual tumors (below) are presented after the second tumor implantation (day 0 = day when second tumor was injected). IFN-γ producing T-cells were assessed from spleens 22 days after virus treatments by ELISpot. Splenocytes were cultured with tumor-associated or virus-associated peptides for 36 hours and spots were counted. (d) Cumulative spot counts of the ELISpot wells of B16-OVA rechallenged mice (left) and B16-F10 rechallenged mice (right).
Figure 5
Figure 5
In vivo efficacy and immunogenicity of the DAI-virus in a peripheral blood mononuclear cell (PBMC) humanized melanoma mouse model. Human melanoma HS294T cells were injected subcutaneously into both flanks of the NSG mice, 5 × 106 cells/flank. When tumors reached injectable size, human PBMCs were injected intravenously to the tail vein in 200 μl of phosphate-buffered saline, 2 × 107 cells/ mouse. Two days later virus treatments were started. Tumors were treated on days 0 and 6 with 1 × 106 pfu/ tumor in volume of 50 μl, mock mice were treated with phosphate-buffered saline only. Parts of the mice were left without PBMCs to have a study control lacking the immune system. (a) Growth of human melanoma HS294T tumors in PBMC humanized NSG mice after virus treatments on days 0 and 6 (N of tumors/group=8). Day 0 = day when the first virus treatment was given. (b) Comparison of the tumor growth in mice humanized with PBMCs (N of tumors/group = 8) and mice that did not receive PBMCs (N of tumors/group = 4).
Figure 6
Figure 6
Oncolytic vaccinia virus expressing human DAI induces infiltration of human T-cells into infected human melanoma tumors in PBMC-humanized mice. Human CD8+ and CD4+ T-cells were analyzed by flow cytometry from (a) tumors, (b) spleens, and (c) blood of mice 18 days after the first treatment.
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