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Paramyxoviruses for Tumor-targeted Immunomodulation: Design and Evaluation Ex Vivo
Published on: January 7, 2019
The anti-virus T cell response dominates the anti-cancer response in oncolytic virus therapy
Meghan J O'Melia1, Kailan Sierra-Davidson2, Miranda A Robert1,3
1Department of Radiation Oncology, Edwin L. Steele Laboratories, Massachusetts General Hospital Cancer Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
Abstract:
Oncolytic viruses have strong potential as immunotherapies. By causing cancer cells to die and relieve antigens, these viruses can stimulate robust, systemic immune responses that may eliminate disseminated disease and prevent recurrence. Unfortunately, clinical trials using oncolytic viruses have not induced clearance of metastasis or protection from recurrence. Likewise, the combination of the only FDA-approved oncolytic virus-Talimogene laherparapvec-with immune checkpoint blockade did not improve progression-free or overall survival. Because of these disappointing clinical trials, we sought to measure the ability of oncolytic viruses to induce cancer antigen presentation and the elicitation of cancer antigen-specific immune responses. Our data revealed that despite improved antigen presentation by dendritic cells, priming of cancer antigen-specific T cells was limited. However, viral antigen-specific T cells did develop and were in a phenotypic state to induce an effective response against virally infected cells. These preclinical results were mirrored in human peripheral blood samples. Overall, these data show that oncolytic virus treatment induces a response against the virus itself, but not cancer antigen, explaining the lack of response in metastatic disease. These interesting findings identify a critical mechanism that needs to be overcome to increase the efficacy of oncolytic virus therapy.
Insights
Oncolytic virus therapy shows promise for cancer immunotherapy by stimulating immune responses. However, current treatments primarily activate anti-viral immunity, not anti-cancer immunity, limiting effectiveness against metastatic disease.
Area of Science:
- Immunology
- Virology
- Oncology
Background:
- Oncolytic viruses are potent immunotherapies that induce cancer cell death and antigen release, potentially stimulating systemic immune responses.
- Clinical trials with oncolytic viruses and combinations like talimogene laherparepvec with immune checkpoint blockade have yielded disappointing results in clearing metastasis and improving survival.
Purpose of the Study:
- To investigate the capacity of oncolytic viruses to enhance cancer antigen presentation and elicit cancer antigen-specific immune responses.
- To understand the limitations of current oncolytic virus therapies in overcoming metastatic disease.
Main Methods:
- Preclinical studies and analysis of human peripheral blood samples were used to assess immune responses.
- Evaluation of antigen presentation by dendritic cells and T cell priming against both viral and cancer antigens.
Main Results:
- Oncolytic viruses improved antigen presentation by dendritic cells, but priming of cancer antigen-specific T cells remained limited.
- Significant development of viral antigen-specific T cells was observed, exhibiting a phenotype capable of targeting virally infected cells.
- These findings were consistent across preclinical models and human samples.
Conclusions:
- Oncolytic virus treatment effectively generates immunity against the virus itself, but not against cancer antigens.
- This selective immune response explains the limited efficacy of oncolytic viruses in treating metastatic cancer.
- Overcoming this mechanism is crucial for enhancing the therapeutic potential of oncolytic virus treatments.
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