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Effects of innate immunity on herpes simplex virus and its ability to kill tumor cells
H Wakimoto1, P R Johnson, D M Knipe
1Molecular Neuro-Oncology Laboratories, Neurosurgery Service, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Abstract:
Several clinical trials have or are being performed testing the safety and efficacy of different strains of oncolytic viruses (OV) for malignant cancers. OVs represent either naturally occurring or genetically engineered strains of viruses that exhibit relatively selective replication in tumor cells. Several types of OV have been derived from herpes simplex virus 1 (HSV1). Tumor oncolysis depends on the processes of initial OV infection of tumor, followed by subsequent propagation of OV within the tumor itself. The role of the immune responses in these processes has not been extensively studied. On the contrary, effects of the immune response on the processes of wild-type HSV1 infection and propagation in the central nervous system have been studied and described in detail. The first line of defense against a wild-type HSV1 infection in both naive and immunized individuals is provided by innate humoral (complement, cytokines, chemokines) and cellular (macrophages, neutrophils, NK cells, gammadelta T cells, and interferon-producing cells) responses. These orchestrate the lysis of virions and virus-infected cells as well as provide a link to effective adaptive immunity. The role of innate defenses in curtailing the oncolytic effect of genetically engineered HSV has only recently been studied, but several of the same host responses appear to be operative in limiting anticancer effects by the replicating virus. The importance of this knowledge lies in finding avenues to modulate such initial innate responses, in order to allow for increased oncolysis of tumors while minimizing host toxicity.
Insights
Oncolytic viruses (OVs) show promise for cancer treatment by selectively replicating in tumor cells. Understanding and modulating the host immune response is crucial for enhancing OV efficacy and minimizing toxicity in cancer therapy.
Area of Science:
- Virology
- Immunology
- Oncology
Background:
- Oncolytic viruses (OVs), including those derived from herpes simplex virus 1 (HSV1), are being investigated for cancer therapy.
- OVs selectively replicate within tumor cells, leading to tumor lysis.
- The role of the immune response in OV efficacy is not fully understood, unlike its well-studied role in HSV1 central nervous system infections.
Purpose of the Study:
- To investigate the role of innate immune responses in the efficacy of oncolytic viruses (OVs) for cancer treatment.
- To explore how host immune responses may limit the anticancer effects of engineered HSV-derived OVs.
- To identify strategies for modulating innate immunity to improve OV-mediated tumor oncolysis and reduce toxicity.
Main Methods:
- Review of existing literature on OV mechanisms and immune responses to HSV1.
- Analysis of host innate immune components (humoral and cellular) involved in viral defense.
- Comparison of immune responses to wild-type HSV1 and engineered OVs.
Main Results:
- Innate immune responses, including complement, cytokines, chemokines, macrophages, neutrophils, NK cells, and gammadelta T cells, are critical in controlling wild-type HSV1 infections.
- Similar innate host responses appear to limit the oncolytic effects of genetically engineered HSV-derived OVs in tumors.
- Understanding these host defenses is key to optimizing OV cancer therapy.
Conclusions:
- The host innate immune system plays a significant role in limiting the effectiveness of oncolytic viruses (OVs) in cancer treatment.
- Modulating these innate immune responses presents a potential strategy to enhance OV oncolysis and improve therapeutic outcomes.
- Further research into host-innate immune interactions is essential for advancing OV-based cancer therapies.
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