Myxoma Virus Infection Promotes NK Lysis of Malignant Gliomas In Vitro and In Vivo

Abstract

Myxoma virus (MYXV) is a well-established oncolytic agent against different types of tumors. MYXV is also known for its immunomodulatory properties in down-regulating major histocompatibility complex (MHC) I surface expression (via the M153R gene product, a viral E3-ubiquitin ligase) and suppressing T cell killing of infected target cells. MHC I down-regulation, however, favors NK cell activation. Brain tumors including gliomas are characterized by high MHC I expression with impaired NK activity. We thus hypothesized that MYXV infection of glioma cells will promote NK cell-mediated recognition and killing of gliomas. We infected human gliomas with MYXV and evaluated their susceptibility to NK cell-mediated cytotoxicity. MYXV enhanced NK cell-mediated killing of glioma cells (U87 cells, MYXV vs. Mock: 51.73% vs. 28.63%, P = .0001, t test; U251 cells, MYXV vs. Mock: 40.4% vs. 20.03%, P .0007, t test). Using MYXV M153R targeted knockout (designated vMyx-M153KO) to infect gliomas, we demonstrate that M153R was responsible for reduced expression of MHC I on gliomas and enhanced NK cell-mediated antiglioma activity (U87 cells, MYXV vs. vMyx-M153KO: 51.73% vs. 25.17%, P = .0002, t test; U251 cells, MYXV vs. vMyx-M153KO: 40.4% vs. 19.27, P = .0013, t test). Consequently, NK cell-mediated lysis of established human glioma tumors in CB-17 SCID mice was accelerated with improved mouse survival (log-rank P = .0072). These results demonstrate the potential for combining MYXV with NK cells to effectively kill malignant gliomas.

Cellular Factors Promoting Resistance to Effective Treatment of Glioma with Oncolytic Myxoma Virus

“…It is not yet clear if MYXV is capable of generating an adaptive immunotherapeutic response in gliomas, however it has been shown in other cancer models 31 as well as to enhance adoptive NK immunotherapy. 17 Additional investigation probing the nature of the glioma microenvironment before and after virotherapy, as well as the specific mechanisms by which the innate immune response limits MYXV infection rates, could lead to a more targeted approach to enhance viral infection while initiating anti-tumour immunity.…”

“…11, 15-17 Animals were followed until they lost ≥20% of body weight or had trouble ambulating, feeding, or grooming. Intracranial injection of vMyx-FLuc or vMyx-GFP was performed on day 14 for all lines in survival or bioluminescent studies, and on day 12 for flow cytometric studies.…”

Involvement of Perforin/Granzyme B-Dependent Signaling Pathway in Cytotoxic Activity of Dendritic Cells Towards Human Glioblastoma Cells

“…Между тем, грануло-опосредованная цитотоксичность может иметь большое значение в противоопухолевом имму-нитете при глиальных опухолях головного моз-га, поскольку многие глиомные опухолевые ли-нии резистентны к рецептор-опосредованному апоптозу [6,8]. В литературе имеются отдельные сообщения о чувствительности клеток глиобла-стомы к перфорин/гранзим Б-опосредованному лизису [11,21]. Исследования in situ показали, что в области иммунологического синапса меж-ду глиобластомными клетками человека и опу-холь-инфильтрирующими CD8 + Т-лимфоцитами обнаруживается гранзим Б [5].…”

Oncolytic Poxviruses

“…The virus downregulates class I major histocompatibility complex (MHC) expression on the surface of infected cells (103); a recent study demonstrated this effect in infected glioma cells in vivo (104). This downregulation led to increased natural killer (NK) cell–mediated recognition and efficient killing of infected glioma cells (104). Thus, MYXV infection not only leads to the direct killing of cancer cells but also promotes early immune cell–mediated antitumor responses.…”