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Updated: Oct 9, 2025
Paramyxoviruses for Tumor-targeted Immunomodulation: Design and Evaluation Ex Vivo
Published on: January 7, 2019
Generation of a Retargeted Oncolytic Herpes Virus Encoding Adenosine Deaminase for Tumor Adenosine Clearance
Chiara Gentile1,2, Arianna Finizio1, Guendalina Froechlich1
1CEINGE Biotecnologie Avanzate S.C.aR.L., Via G. Salvatore 486, 80145 Naples, Italy.
Background:
Oncolytic viruses are immunotherapeutic agents that can be engineered to encode payloads of interest within the tumor microenvironment to enhance therapeutic efficacy. Their therapeutic potential could be limited by many avenues for immune evasion exerted by the tumor. One such is mediated by adenosine, which induces pleiotropic immunosuppression by inhibiting antitumor immune populations as well as activating tolerogenic stimuli. Adenosine is produced starting from the highly immunostimulatory ATP, which is progressively hydrolyzed to ADP and adenosine by CD39 and CD73. Cancer cells express high levels of CD39 and CD73 ectoenzymes, thus converting immunostimulatory purinergic signal of ATP into an immunosuppressive signal. For this reason, CD39, CD73 and adenosine receptors are currently investigated in clinical trials as targets for metabolic cancer immunotherapy. This is of particular relevance in the context of oncovirotherapy, as immunogenic cell death induced by oncolytic viruses causes the secretion of a high amount of ATP which is available to be quickly converted into adenosine.
Methods:
Here, we took advantage of adenosine deaminase enzyme that naturally converts adenosine into the corresponding inosine derivative, devoid of immunoregulatory function. We encoded ADA into an oncolytic targeted herpes virus redirected to human HER2. An engineered ADA with an ectopic signal peptide was also generated to improve enzyme secretion (ADA-SP).
Results:
Insertion of the expression cassette was not detrimental for viral yield and cancer cell cytotoxicity. The THV_ADA and THV_ADA-SP successfully mediated the secretion of functional ADA enzyme. In in vitro model of human monocytes THP1, this ability of THV_ADA and THV_ADA-SP resulted in the retrieval of eADO-exposed monocytes replication rate, suggesting the proficiency of the viruses in rescuing the immune function.
Conclusions:
Encoding ADA into oncolytic viruses revealed promising properties for preclinical exploitation.
Insights
Oncolytic viruses engineered to carry the adenosine deaminase (ADA) enzyme can overcome tumor-induced immunosuppression. This approach enhances the potential of oncolytic virotherapy by neutralizing adenosine, a key immunosuppressive molecule in the tumor microenvironment.
Area of Science:
- Oncolytic virotherapy
- Cancer immunotherapy
- Molecular virology
Background:
- Oncolytic viruses are potent immunotherapeutic agents but face immune evasion challenges within the tumor microenvironment.
- Tumors exploit adenosine signaling, produced by CD39 and CD73 enzymes, to suppress anti-tumor immune responses.
- Adenosine converts immunostimulatory ATP into an immunosuppressive signal, hindering effective cancer immunotherapy.
Purpose of the Study:
- To engineer oncolytic viruses expressing adenosine deaminase (ADA) to counteract adenosine-mediated immunosuppression.
- To evaluate the efficacy of ADA-encoding oncolytic viruses in restoring immune function within the tumor microenvironment.
Main Methods:
- Adenosine deaminase (ADA) was encoded into an oncolytic targeted herpes virus (THV) directed against human HER2.
- An engineered ADA with a signal peptide (ADA-SP) was created to enhance enzyme secretion.
- Viral yield, cancer cell cytotoxicity, and immune cell function were assessed in vitro.
Main Results:
- The engineered viruses (THV_ADA and THV_ADA-SP) did not compromise viral yield or cancer cell killing ability.
- Functional ADA enzyme was successfully secreted by the engineered viruses.
- In vitro studies showed that THV_ADA and THV_ADA-SP restored the replication rate of adenosine-exposed monocytes, indicating improved immune function.
Conclusions:
- Encoding ADA into oncolytic viruses presents a promising strategy for preclinical cancer immunotherapy.
- This approach effectively neutralizes immunosuppressive adenosine, enhancing the therapeutic potential of oncolytic virotherapy.
