Utility of a Recombinant HSV-1 Vaccine Vector for Personalized Cancer Vaccines.

Current approaches to cancer immunotherapy include immune checkpoint inhibitors, cancer vaccines, and adoptive cellular therapy. These therapies have produced significant clinical success for specific cancers, but their efficacy has been limited. Oncolytic virotherapy (OVT) has emerged as a promising immunotherapy for a variety of cancers. Furthermore, the unique characteristics of OVs make them a good choice for delivering tumor peptides/antigens to induce enhanced tumor-specific immune responses. The first oncolytic virus (OV) approved for human use is the attenuated herpes simplex virus type 1 (HSV-1), Talimogene laherparepvec (T-VEC) which has been FDA approved for the treatment of melanoma in humans. In this study, we engineered the recombinant oncolytic HSV-1 (oHSV) VC2-OVA expressing a fragment of ovalbumin (OVA) as a fusion protein with VP26 virion capsid protein. We tested the ability of VC2-OVA to act as a vector capable of stimulating strong, specific antitumor immunity in a syngeneic murine melanoma model. Therapeutic vaccination with VC2-OVA led to a significant reduction in colonization of tumor cells in the lungs of mice intravenously challenged B16cOVA cells. In addition, VC2-OVA induced a potent prophylactic antitumor response and extended survival of mice that were intradermally engrafted with B16cOVA tumors compared with mice immunized with control virus.

Uche IK ，Stanfield BA ，Rudd JS ，Kousoulas KG ，Rider PJF ... -  《Frontiers in Molecular Biosciences》

Novel Oncolytic Herpes Simplex Virus 1 VC2 Promotes Long-Lasting, Systemic Anti-melanoma Tumor Immune Responses and Increased Survival in an Immunocompetent B16F10-Derived Mouse Melanoma Model.

Oncolytic virotherapy (OVT) is now understood to be an immunotherapy that uses viral infection to liberate tumor antigens in an immunogenic context to promote the development of antitumor immune responses. The only currently FDA-approved oncolytic virotherapy, T-Vec, is a modified type 1 herpes simplex virus (HSV-1). While T-Vec is associated with limited response rates, its modest efficacy supports the continued development of novel OVT viruses. Herein, we test the efficacy of a recombinant HSV-1, VC2, as an OVT in a syngeneic B16F10-derived mouse model of melanoma. VC2 possesses mutations that block its ability to enter neurons via axonal termini. This greatly enhances its safety profile by precluding the ability of the virus to establish latent infection. VC2 has been shown to be a safe, effective vaccine against both HSV-1 and HSV-2 infection in mice, guinea pigs, and nonhuman primates. We found that VC2 slows tumor growth rates and that VC2 treatment significantly enhances survival of tumor-engrafted, VC2-treated mice over control treatments. VC2-treated mice that survived initial tumor engraftment were resistant to a second engraftment as well as colonization of lungs by intravenous introduction of tumor cells. We found that VC2 treatment induced substantial increases in intratumoral T cells and a decrease in immunosuppressive regulatory T cells. This immunity was critically dependent on CD8+ T cells and less dependent on CD4+ T cells. Our data provide significant support for the continued development of VC2 as an OVT for the treatment of human and animal cancers.IMPORTANCE Current oncolytic virotherapies possess limited response rates. However, when certain patient selection criteria are used, oncolytic virotherapy response rates have been shown to increase. This, in addition to the increased response rates of oncolytic virotherapy in combination with other immunotherapies, suggests that oncolytic viruses possess significant therapeutic potential for the treatment of cancer. As such, it is important to continue to develop novel oncolytic viruses as well as support basic research into their mechanisms of efficacy. Our data demonstrate significant clinical potential for VC2, a novel type 1 oncolytic herpes simplex virus. Additionally, due to the high rates of survival and the dependence on CD8+ T cells for efficacy, our model will enable study of the immunological correlates of protection for VC2 oncolytic virotherapy and oncolytic virotherapy in general. Understanding the mechanisms of efficacious oncolytic virotherapy will inform the rational design of improved oncolytic virotherapies.

Uche IK ，Fowlkes N ，Vu L ，Watanabe T ，Carossino M ，Nabi R ，Del Piero F ，Rudd JS ，Kousoulas KG ，Rider PJF ... -  《-》

The Oncolytic herpes simplex virus type-1 (HSV-1) vaccine strain VC2 causes intratumor infiltration of functionally active T cells and inhibition of tumor metastasis and pro-tumor genes VEGF and PDL1 expression in the 4T1/Balb/c mouse model of stage four

Introduction: Oncolytic viruses (OVs) provide new modalities for cancer therapy either alone or in combination with synergistic immunotherapies and/or chemotherapeutics. Engineered Herpes Simplex Virus Type-1 (HSV-1) has shown strong promise for the treatment of various cancers in experimental animal models as well as in human patients, with some virus strains licensed to treat human melanoma and gliomas. In the present study we evaluated the efficacy of mutant HSV-1 (VC2) in a late stage, highly metastatic 4T1 murine syngeneic. Method: VC2 was constructed VC2 using double red recombination technology. For in-vivo efficacy we utilized a late stage 4T1 syngeneic and immunocompetent BALB/cJ mouse model breast cancer model which exhibits efficient metastasis to the lung and other organs. Results: VC2 replicated efficiently in 4T1 cells and in cell culture, achieving titers similar to those in African monkey kidney (Vero) cells. Intra-tumor treatment with VC2 did not appreciably reduce average primary tumor sizes but a significant reduction of lung metastasis was noted in mice treated intratumorally with VC2, but not with ultraviolet-inactivated VC2. This reduction of metastasis was associated with increased T cell infiltration comprised of CD4+ and CD4+CD8+ double-positive T cells. Characterization of purified tumor infiltrating T cells revealed a significant improvement in their proliferation ability compared to controls. In addition, significant T cell infiltration was observed in the metastatic nodules associated with reduction of pro-tumor PD-L1 and VEGF gene transcription. Conclusion: These results show that VC2 therapy can improve anti-tumor response associated with a better control of tumor metastasis. improve T cell responses and reduce pro-tumor biomarker gene transcription. VC2 holds promise for further development as an oncolytic and immunotherapeutic approach to treat breast and other cancers.

Nabi R ，Musarrat F ，Menk P Lima JC ，Langohr IM ，Chouljenko VN ，Kousoulas KG ... -  《Frontiers in Molecular Biosciences》

The Oncolytic Herpes Simplex Virus Talimogene Laherparepvec Shows Promising Efficacy in Neuroendocrine Cancer Cell Lines.

Metastatic neuroendocrine cancer still constitutes a palliative situation, lacking promising treatment options. Oncolytic virotherapy, a novel type of virus-based immunotherapy, lyses tumor cells using genetically engineered viruses thereby activating the immune system to induce an optimized antitumor response which could bring down tumor masses to a stage of minimal residual tumor disease. The oncolytic vector talimogene laherparepvec (T-VEC, herpes simplex virus [HSV] type 1) has already shown excellent safety profiles in clinical studies and has become the first ever FDA/EMA-approved oncolytic virus (OV). This work presents a first preclinical assessment of this state-of-the-art OV, using a panel of human neuroendocrine tumor/neuroendocrine carcinoma (NET/NEC) cell lines. Cytotoxicity, transgene expression, and viral replication patterns were studied. Furthermore, the antiproliferative activity was compared to the one of mTOR inhibitor Everolimus and also interactions between the OV and Everolimus were evaluated. Moreover, virostatic effects of ganciclovir (GCV) on replication of T-VEC were assessed and electron microscopic pictures were taken to comprehend viral envelopment and details of the replication cycle of T-VEC in human neuroendocrine cancer. It could be shown that T-VEC infects, replicates in, and lyses human NET/NEC cells exhibiting high oncolytic efficiencies already at quite low virus concentrations. Interestingly, Everolimus was not found to have any relevant impact on rates of viral replication, but no additive effects could be proved using a combinatorial therapy regimen. On the other hand, GCV was shown to be able to limit replication of T-VEC, thus establishing an important safety feature for future treatments of NET/NEC patients. Taken together, T-VEC opens up a promising novel treatment option for NET/NEC patients, warranting its further preclinical and clinical development.

Kloker LD ，Berchtold S ，Smirnow I ，Schaller M ，Fehrenbacher B ，Krieg A ，Sipos B ，Lauer UM ... -  《-》

Talimogene Laherparepvec (T-VEC): A Review of the Recent Advances in Cancer Therapy.

Zhang T ，Jou TH ，Hsin J ，Wang Z ，Huang K ，Ye J ，Yin H ，Xing Y ... -  《Journal of Clinical Medicine》