Lymphokine‐activated killer and dendritic cell carriage enhances oncolytic reovirus therapy for ovarian cancer by overcoming antibody neutralization in ascites

V.A Jennings,G.D Hall,E.J Ilett,R Vile,A.A Melcher,P Selby,K.J Scott,H Pandha,E.J West,A Young,M Coffey,K Harrington,F Errington‐Mais

doi:10.1002/ijc.28450

Abstract

Reovirus is an oncolytic virus (OV), which acts by both direct tumor cell killing and priming of antitumor immunity. A major obstacle for effective oncolytic virotherapy is effective delivery of OV to tumor cells. Ovarian cancer is often confined to the peritoneal cavity and therefore i.p. delivery of reovirus may provide the ideal locoregional delivery, avoiding systemic dissemination. However, ovarian cancer is associated with an accumulation of ascitic fluid, which may interfere with oncolytic viral therapy. Here, we investigated the effect of ascites on reovirus-induced oncolysis against primary ovarian cancer cells and ovarian cancer cell lines. In the absence of ascites, reovirus was cytotoxic against ovarian cancer cells; however, cytotoxicity was abrogated in the presence of ascitic fluid. Neutralizing antibodies (NAb) were identified as the cause of this inhibition. Loading OV onto cell carriers may facilitate virus delivery in the presence of NAb and immune cells which have their own antitumor effector activity are particularly appealing. Immature dendritic cells (iDC), Lymphokine-activated killer (LAK) cells and LAKDC cocultures were tested as potential carriers for reovirus for tumor cell killing and immune cell priming. Reovirus-loaded LAKDC, and to a lesser degree iDC, were able to: (i) protect from NAb and hand-off reovirus for tumor cell killing; (ii) induce a proinflammatory cytokine milieu (IFNɣ, IL-12, IFNα and TNFα) and (iii) generate an innate and specific antitumor adaptive immune response. Hence, LAKDC pulsed with reovirus represent a novel, clinically practical treatment for ovarian cancer to maximise both direct and innate/adaptive immune-mediated tumor cell killing.What’s new?Oncolytic viruses (OVs) specifically infect and kill tumor cells. In this study, the authors began to examine whether intraperitoneal delivery of an OV could be effective against ovarian cancer. They found that, while the virus does kill ovarian-cancer cells in vitro, this effect is blocked when ascites fluid is added. Cytotoxicity can be restored, however, by using a combination of lymphokine-activated killer and dendritic cells (LAKDC) as carriers, which protect the virus from neutralizing antibodies in the ascites. The LAKDC combination may also support subsequent adaptive immune priming.

Highlights

Ovarian cancer is the leading cause of death amongst gynaecological malignancies and the fourth most common cause of cancer-related deaths in women, with 125,000 deaths per year, worldwide
In the presence of 2.5 % ascitic fluid, reovirusinduced cytotoxicity was significantly inhibited in all cell lines and in four out of four patient tumor samples cultured in autologous ascites (Figs. 1a and 1d)
In the absence of ascites, reovirus readily replicated in ovarian cancer cell lines (Fig. 1b) and primary ovarian cancer cells (Fig. 1e, at 10- to 1000-fold lower levels than those detected in cell lines)

Summary

Introduction

Ovarian cancer is the leading cause of death amongst gynaecological malignancies and the fourth most common cause of cancer-related deaths in women, with 125,000 deaths per year, worldwide. Viral internalization by carrier cells may allow better protection from NAb but will fail if the carrier cell is killed before it reaches the tumor site In this regard, it is reassuring that reovirus is not toxic to human DC, T cells[18] or peripheral blood mononuclear cells (PBMC).[19] using immune cells as carriers has the potential to provide additional antitumor activity, either via direct cytotoxicity [e.g., natural killer (NK), cytokine-induced killer (CIK) and lymphokine-activated killer (LAK) cells], or by supporting the priming of adaptive antitumor immune responses (e.g., DC and macrophages). Preclinical studies have demonstrated that vesicular stomatitis virus (VSV) loaded onto tumor-specific T cells and vaccinia virus (VV) loaded onto CIK cells can enhance antitumor therapy compared with either agent alone.[20,21]

Methods

Results

Conclusion