Injected into solid tumors, Toxoplasma gondii, the parasite responsible for toxoplasmosis, would block their growth and make them more sensitive to treatment.
- When injected into solid tumors, the mutant strain of the parasite responsible for toxoplasmosis makes them more susceptible to treatment with immunotherapy.
- Tested on mice, this protocol reduced tumor growth in several cancers.
May be present in raw or undercooked meat, on vegetables, or insufficiently washed fruits, Toxoplasma gondii is an intracellular parasite that can cause toxoplasmosis, an infection that can cause serious health problems in pregnant women and immunocompromised patients.
But this parasite could also be used to treat different types of tumors. This is shown by a new international study published in the Journal for ImmunoTherapy Cancer. According to its authors, researchers at the University of Nottingham (England), Ningbo University and Shanxi Agricultural University (China), Toxoplasma gondii is able to sensitize cold tumors – that is, tumors that are not likely to elicit a strong immune response from the body – to an immunotherapy called immune checkpoint inhibitor therapy.
Reduced tumor growth
To be able to live and develop, Toxoplasma gondii must live inside the cells of its host. For this, it secretes many proteins to counter the host’s immune defenses and facilitate its own invasion and colonization of host cells.
The researchers used this mode of survival to develop a mutant strain of the parasite, which they then transmitted to mice. The results showed that direct injection of this mutant parasite into solid tumors induces inflammatory responses in the injected tumors and even in tumors located remotely within the mouse body. It also makes tumors more responsive to treatment with an immune checkpoint inhibitor.
This dual treatment significantly prolonged mouse survival and reduced tumor growth in mouse models of melanoma, Lewis lung carcinoma, and colon adenocarcinoma.
“The use of a mutant version of Toxoplasma gondii in the treatment of certain tumors in mouse models has been previously reported. What makes this study different is the confirmation that intratumoral injection of the mutant strain of Toxoplasma gondii enhances antitumor immunity and effectiveness of checkpoint inhibition therapy”explains Dr. Hany Elsheikha, one of the main authors of the study.
“These are significant and relevant results for the future treatment of tumors. The marked reduction in tumor size and significant improvement in survival of mice that received this novel combination therapy are promising but should be interpreted with caution. Caution as further research is needed”he concludes.
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