Oncolytic herpes simplex virus type 1 (HSV-1) in combination with lenalidomide for plasma cell neoplasms.

Oncolytic viruses exert an anti-tumour effect through two mechanisms: direct oncolytic and indirect immune-mediated mechanisms. Although oncolytic herpes simplex virus type 1 (HSV-1) has been approved for melanoma treatment and is being examined for its applicability to a broad spectrum of malignancies, it is not known whether it has an anti-myeloma effect. In the present study, we show that the third-generation oncolytic HSV-1, T-01, had a direct oncolytic effect on five of six human myeloma cell lines in vitro. The anti-tumour effect was enhanced in the presence of peripheral blood mononuclear cells (PBMCs) from healthy individuals and, to a lesser extent, from patients with myeloma. The enhancing effect of PBMCs was abrogated by blocking type I interferons (IFNs) or by depleting plasmacytoid dendritic cells (pDCs) or natural killer (NK) cells, suggesting that pDC-derived type I IFNs and NK cells dominated the anti-tumour effect. Furthermore, the combination of T-01 and lenalidomide exhibited enhanced cytotoxicity, and the triple combination of T-01, lenalidomide and IFN-α had a maximal effect. These data indicate that oncolytic HSV-1 represents a viable therapy for plasma cell neoplasms through direct oncolysis and immune activation governed by pDCs and NK cells. Lenalidomide is likely to augment the anti-myeloma effect of HSV-1.

Oncolytic Virus Therapy with HSV-1 for Hematological Malignancies.

Oncolytic herpes simplex virus type 1 (HSV-1) has been investigated to expand its application to various malignancies. Because hematopoietic cells are resistant to HSV-1, its application to hematological malignancies has been rare. Here, we show that the third generation oncolytic HSV-1, T-01, infected and killed 18 of 26 human cell lines and 8 of 15 primary cells derived from various lineages of hematological malignancies. T-01 replicated at low levels in the cell lines. Viral entry and the oncolytic effect were positively correlated with the expression level of nectin-1 and to a lesser extent 3-O-sulfated heparan sulfate, receptors for glycoprotein D of HSV-1, on tumor cells. Transfection of nectin-1 into nectin-1-negative tumor cells made them susceptible to T-01. The oncolytic effects did not appear to correlate with the expression or phosphorylation of antiviral molecules in the cyclic GMP-AMP (cGAS)-stimulator of interferon genes (STING) and PKR-eIF2α pathways. In an immunocompetent mouse model, intratumoral injection of T-01 into lymphoma induced regression of injected, as well as non-injected, contralateral tumors accompanied by abundant infiltration of antigen-specific CD8+ T cells. These data suggest that intratumoral injection of oncolytic HSV-1 may be applicable to systemic hematological malignancies. Nectin-1 expression may be the most useful biomarker for optimal efficacy.