The Effect of Herpes Simplex Virus-Type-1 (HSV-1) Oncolytic Immunotherapy on the Tumor Microenvironment

Safety and dose escalation of the targeted oncolytic adenovirus OBP-301 for refractory advanced liver cancer: Phase I clinical trial

OBP-301 is an oncolytic adenovirus modified to replicate within cancer cells and lyse them. This open-label, non-comparative, phase I dose-escalation trial aimed to assess its safety and optimal dosage in 20 patients with advanced hepatocellular carcinoma. Good tolerance was shown with a maximum tolerated dose of 6 × 1012 viral particles. The most common treatment-emergent adverse events were influenza-like illness, pyrexia, fatigue, decreased platelet count, abdominal distension, and anemia. Cohorts 4 and 5 had approximately 50% higher levels of CD8+ T cells in the peripheral blood after injection. The best target response occurred in 14 patients, 4 of whom had progressive disease. Multiple intratumoral injections of OBP-301 were well tolerated in patients with advanced hepatocellular carcinoma. The stable disease rate for the injected tumors was greater than the overall response rate, even with no obvious tumor response. OBP-301 might have a greater impact on local response as histological examination revealed that the presence of OBP-301 was consistent with the necrotic area at the injection site. Increased infiltration of CD8+ T cells and <1% PD-L1 expression were observed in tumors after injection. Improved antitumor efficacy might be achieved in future studies via viral injection with volume adjustment and in combination with other immuno-therapeutics.

Treatment of a large area perioral viral herpes infection following noninvasive ventilation: A case report

BACKGROUND

Alphaherpesvirus belongs to the Herpesviridae family and has large, monopartite double-stranded linear DNA. It mainly infects the skin, mucosa, and nerves, and can affect various hosts, including humans and other animals. Here, we present a case of a patient seen by the gastroenterology department at our hospital who experienced an oral and perioral herpes infection following treatment with a ventilator. The patient was treated with oral and topical antiviral drugs, furacilin, oral and topical antibiotics, local epinephrine injection, topical thrombin powder, and nutritional and supportive care. A wet wound healing approach was also implemented with good response.

CASE SUMMARY

A 73-year-old woman presented to the hospital with a chief complaint of "abdominal pain for 3 d with dizziness for 2 d." She was admitted to the intensive care unit for septic shock and spontaneous peritonitis secondary to cirrhosis and was given antiinflammatory and symptomatic supportive treatment. A ventilator was used to assist breathing for acute respiratory distress syndrome, which developed during her admission. A large area of herpes infection appeared in the perioral region 2 d following noninvasive ventilation. The patient was transferred to the gastroenterology department, at which time she had a body temperature of 37.8 C and a respiratory rate of 18/min. The patient's consciousness was intact, and she no longer had abdominal pain or distension, chest tightness, or asthma. At this point, the infected perioral region changed in appearance and was now accompanied by local bleeding with crusting of blood at the wounds. The surface area of the wounds measured approximately 10 cm × 10 cm. A cluster blisters appeared on the patient’s right neck, and ulcers developed in her mouth. On a subjective numerical pain scale, the patient reported a pain level of 2. Overall, her diagnoses other than the oral and perioral herpes infection included: (1) Septic shock; (2) spontaneous peritonitis; (3) abdominal infection; (4) decompensated cirrhosis; and (5) hypoproteinemia. Dermatology was consulted regarding the treatment of the patient’s wounds; they suggested treatment with oral antiviral drugs, an intramuscular injection of nutritious nerve drugs, and the application of topical penciclovir and mupirocin around the lips. Stomatology was also consulted and suggested the use of nitrocilin in a local wet application around the lips.

CONCLUSION

Through multidisciplinary consultation, the patient’s oral and perioral herpes infection was successfully treated with the following combined approach: (1) Application of topical antviral and antibiotic treatments; (2) keeping the wound moist with a wet wound healing strategy; (3) systemic use of oral antiviral drugs; and (4) symptomatic and nutritional supportive care. The patient was discharged from the hospital after successful wound healing.

PKR induces TGF-β and limits oncolytic immune therapy

BACKGROUND

Mammalian cells have developed multiple intracellular mechanisms to defend against viral infections. These include RNA-activated protein kinase (PKR), cyclic GMP-AMP synthase and stimulation of interferon genes (cGAS-STING) and toll-like receptor-myeloid differentiation primary response 88 (TLR-MyD88). Among these, we identified that PKR presents the most formidable barrier to oncolytic herpes simplex virus (oHSV) replication in vitro.

METHODS

To elucidate the impact of PKR on host responses to oncolytic therapy, we generated a novel oncolytic virus (oHSV-shPKR) which disables tumor intrinsic PKR signaling in infected tumor cells.

RESULTS

As anticipated, oHSV-shPKR resulted in suppression of innate antiviral immunity and improves virus spread and tumor cell lysis both in vitro and in vivo. Single cell RNA sequencing combined with cell-cell communication analysis uncovered a strong correlation between PKR activation and transforming growth factor beta (TGF-ß) immune suppressive signaling in both human and preclinical models. Using a murine PKR targeting oHSV, we found that in immune-competent mice this virus could rewire the tumor immune microenvironment to increase the activation of antigen presentation and enhance tumor antigen-specific CD8 T cell expansion and activity. Further, a single intratumoral injection of oHSV-shPKR significantly improved the survival of mice bearing orthotopic glioblastoma. To our knowledge, this is the first report to identify dual and opposing roles of PKR wherein PKR activates antivirus innate immunity and induces TGF-ß signaling to inhibit antitumor adaptive immune responses.

CONCLUSIONS

Thus, PKR represents the Achilles heel of oHSV therapy, restricting both viral replication and antitumor immunity, and an oncolytic virus that can target this pathway significantly improves response to virotherapy.

Inactivation of the UL37 Deamidase Enhances Virus Replication and Spread of the HSV-1(VC2) Oncolytic Vaccine Strain and Secretion of GM-CSF

The HSV-1 (VC2) live-attenuated vaccine strain was engineered with specific deletions in the amino termini of glycoprotein K (gK) and membrane protein UL20, rendering the virus unable to enter neurons and establish latency. VC2 replicates efficiently in epithelial cell culture but produces lower viral titers and smaller viral plaques than its parental HSV-1 (F) wild-type virus. VC2 is an effective live-attenuated vaccine against HSV-1 and HSV-2 infections in mice and guinea pigs and an anti-tumor immunotherapeutic and oncolytic virus against melanoma and breast cancer in mouse models. Previously, we reported that the gK/UL20 complex interacts with the UL37 tegument protein, and this interaction is essential for virion intracellular envelopment and egress. To investigate the potential role of the UL37 deamidase functions, the recombinant virus FC819S and VC2C819S were constructed with a C819S substitution to inactivate the UL37 predicted deamidase active site on an HSV-1(F) and HSV-1(VC2) genetic background, respectively. FC819S replicated to similar levels with HSV-1(F) and produced similar size viral plaques. In contrast, VC2C819S replication was enhanced, and viral plaques increased in size, approaching those of the wild-type HSV-1(F) virus. FC819S infection of cell cultures caused enhanced GM-CSF secretion in comparison to HSV-1(F) across several cell lines, including HEp2 cells and cancer cell lines, DU145 (prostate) and Panc 04.03 (pancreas), and primary mouse peritoneal cells. VC2 infection of these cell lines caused GM-CSF secretion at similar levels to FC819S infection. However, the VC2C819S virus did not exhibit any further enhancement of GM-CSF secretion compared to the VC2 virus. These results suggest that the UL37 deamidation functions in conjunction with the gK/UL20 complex to facilitate virus replication and GM-CSF secretion.

Oncolytic Virotherapy

Oncolytic virotherapy opens up avenues for cancer treatment by selectively targeting the cancer cells and destructs them either through direct lysis or by inducing an immune response in the tumor microenvironment. This platform technology utilizes a diverse range naturally existing or genetically modified oncolytic viruses for their immunotherapeutic potential. Due to the limitations associated with the conventional cancer therapies, immunotherapies using oncolytic viruses (OVs) have generated a great deal of interest in the modern era. Currently, several oncolytic viruses have entered clinical trials and have proven successful for a number of different cancers as monotherapies as well as in combination with the standard treatment methods like chemotherapy, radiotherapy, or immunotherapy. Efficacy of OVs can be further enhanced by utilizing several approaches. Efforts of the scientific community for getting better knowledge of individual patient tumor immune responses will enable medical community to treat cancer patients more precisely. In this regard, OV seems to be a part of multimodality cancer treatment option in the near future. In this chapter, the fundamental characteristics and mechanism of actions of oncolytic viruses are initially described and then overview of the important clinical trials of various oncolytic viruses for a number of cancers is presented.

Combining of Oncolytic Virotherapy and Other Immunotherapeutic Approaches in Cancer: A Powerful Functionalization Tactic

Oncolytic viruses have found a good place in the treatment of cancer. Administering oncolytic viruses directly or by applying genetic changes can be effective in cancer treatment through the lysis of tumor cells and, in some cases, by inducing immune system responses. Moreover, oncolytic viruses induce antitumor immune responses via releasing tumor antigens in the tumor microenvironment (TME) and affect tumor cell growth and metabolism. Despite the success of virotherapy in cancer therapies, there are several challenges and limitations, such as immunosuppressive TME, lack of effective penetration into tumor tissue, low efficiency in hypoxia, antiviral immune responses, and off-targeting. Evidence suggests that oncolytic viruses combined with cancer immunotherapy-based methods such as immune checkpoint inhibitors and adoptive cell therapies can effectively overcome these challenges. This review summarizes the latest data on the use of oncolytic viruses for the treatment of cancer and the challenges of this method. Additionally, the effectiveness of mono, dual, and triple therapies using oncolytic viruses and other anticancer agents has been discussed based on the latest findings.

Oncolytic virus-based hepatocellular carcinoma treatment: Current status, intravenous delivery strategies, and emerging combination therapeutic solutions

Current treatments for advanced hepatocellular carcinoma (HCC) have limited success in improving patients' quality of life and prolonging life expectancy. The clinical need for more efficient and safe therapies has contributed to the exploration of emerging strategies. Recently, there has been increased interest in oncolytic viruses (OVs) as a therapeutic modality for HCC. OVs undergo selective replication in cancerous tissues and kill tumor cells. Strikingly, pexastimogene devacirepvec (Pexa-Vec) was granted an orphan drug status in HCC by the U.S. Food and Drug Administration (FDA) in 2013. Meanwhile, dozens of OVs are being tested in HCC-directed clinical and preclinical trials. In this review, the pathogenesis and current therapies of HCC are outlined. Next, we summarize multiple OVs as single therapeutic agents for the treatment of HCC, which have demonstrated certain efficacy and low toxicity. Emerging carrier cell-, bioengineered cell mimetic- or nonbiological vehicle-mediated OV intravenous delivery systems in HCC therapy are described. In addition, we highlight the combination treatments between oncolytic virotherapy and other modalities. Finally, the clinical challenges and prospects of OV-based biotherapy are discussed, with the aim of continuing to develop a fascinating approach in HCC patients.

Cerebellar High-Grade Glioma: A Translationally Oriented Review of the Literature

World Health Organization (WHO) grade 4 gliomas of the cerebellum are rare entities whose understanding trails that of their supratentorial counterparts. Like supratentorial high-grade gliomas (sHGG), cerebellar high-grade gliomas (cHGG) preferentially affect males and prognosis is bleak; however, they are more common in a younger population. While current therapy for cerebellar and supratentorial HGG is the same, recent molecular analyses have identified features and subclasses of cerebellar tumors that may merit individualized targeting. One recent series of cHGG included the subclasses of (1) high-grade astrocytoma with piloid features (HGAP, ~31% of tumors); (2) H3K27M diffuse midline glioma (~8%); and (3) isocitrate dehydrogenase (IDH) wildtype glioblastoma (~43%). The latter had an unusually low-frequency of epidermal growth factor receptor (EGFR) and high-frequency of platelet-derived growth factor receptor alpha (PDGFRA) amplification, reflecting a different composition of methylation classes compared to supratentorial IDH-wildtype tumors. These new classifications have begun to reveal insights into the pathogenesis of HGG in the cerebellum and lead toward individualized treatment targeted toward the appropriate subclass of cHGG. Emerging therapeutic strategies include targeting the mitogen-activated protein kinases (MAPK) pathway and PDGFRA, oncolytic virotherapy, and immunotherapy. HGGs of the cerebellum exhibit biological differences compared to sHGG, and improved understanding of their molecular subclasses has the potential to advance treatment.

Serendipitous synergism - an exceptional response to treatment with pembrolizumab in the course of a natural immunovirotherapy: a case report and review of the literature

Immune checkpoint inhibitors (ICIs) are the current guideline recommended treatment for many malignancies considered to be terminal. Despite considerable advances, their utility remains limited, and the field requires synergistic partners to further improve outcomes. Oncolytic viruses (OV) are emerging as contenders for the role of the synergistic agent of choice due to their multi-mechanistic effect on activating the tumor 'cold' immune microenvironment. Herpes simplex virus 1, a naturally selective OV, is the most advanced virotherapeutic compound in clinical applications for use in combination with ICI. We here present the case of a 72 year-old patient with a heavily pre-treated, advanced maxillary sinus squamous cell cancer with distant metastases who developed complete response (CR) with only three administrations of a programmed death 1 inhibitor after treatment interference by a severe herpes zoster infection, based on the related alpha-herpesvirus varicella zoster virus (VZV). This exceptional response has been followed and confirmed with imaging studies over more than 5 years. Although the patient had several favorable predictors for response to immunotherapy, we reason that the exceptional response may in part be secondary to the serendipitous VZV infection. Documented cases of cancer patients that achieved CR after few administrations of treatment with ICI are rare, with most reporting follow up of just over 1 year or less. In this case, it is conceivable that the interference of the infection with VZV, soon after the start of immunotherapy with ICI, led to a lasting antitumor immunity and sustained CR. This hypothesis is supported by the concept of 'oncolytic immunotherapy' which is reviewed in this manuscript. In addition, persistence of a TP53 mutation found in a liquid biopsy, despite clinical and radiologic remission, is discussed.

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.

Genetic Modifications That Expand Oncolytic Virus Potency

Oncolytic viruses (OVs) are a promising type of cancer therapy since they selectively replicate in tumor cells without damaging healthy cells. Many oncolytic viruses have progressed to human clinical trials, however, their performance as monotherapy has not been as successful as expected. Importantly, recent literature suggests that the oncolytic potential of these viruses can be further increased by genetically modifying the viruses. In this review, we describe genetic modifications to OVs that improve their ability to kill tumor cells directly, to dismantle the tumor microenvironment, or to alter tumor cell signaling and enhance anti-tumor immunity. These advances are particularly important to increase virus spread and reduce metastasis, as demonstrated in animal models. Since metastasis is the principal cause of mortality in cancer patients, having OVs designed to target metastases could transform cancer therapy. The genetic alterations reported to date are only the beginning of all possible improvements to OVs. Modifications described here could be combined together, targeting multiple processes, or with other non-viral therapies with potential to provide a strong and lasting anti-tumor response in cancer patients.

Oncolytic Viruses: Newest Frontier for Cancer Immunotherapy

Cancer remains a leading cause of death worldwide. Despite many signs of progress, currently available cancer treatments often do not provide desired outcomes for too many cancers. Therefore, newer and more effective therapeutic approaches are needed. Oncolytic viruses (OVs) have emerged as a novel cancer treatment modality, which selectively targets and kills cancer cells while sparing normal ones. In the past several decades, many different OV candidates have been developed and tested in both laboratory settings as well as in cancer patient clinical trials. Many approaches have been taken to overcome the limitations of OVs, including engineering OVs to selectively activate anti-tumor immune responses. However, newer approaches like the combination of OVs with current immunotherapies to convert "immune-cold" tumors to "immune-hot" will almost certainly improve the potency of OVs. Here, we discuss strategies that are explored to further improve oncolytic virotherapy.