A deadly parasite known to cause serious health issues in pregnant women and individuals with impaired immune systems could be used to diagnose a range of cancers, according to researchers.

The study, published in the Journal for ImmunoTherapy Cancer, was carried out by scientists from the University of Nottingham, Ningbo University and Shanxi Agricultural University in China.

To fight certain cancers, limit tumor progression, and extend patients’ lives, it’s critical to improve the effectiveness of treatment against specific types of tumors. In this recent study, researchers discovered that a parasite found all over the world can sensitize cold tumors to immune checkpoint blockade therapy. Cold tumours are tumours that are unlikely to elicit a strong immunological response from the body.

The researchers feel that this discovery could have broader treatment implications for a variety of malignancies.

The researchers were able to tame the parasite Toxoplasma gondii, a single-celled opportunistic protozoan that can infect a wide range of warm-blooded mammals and has been found in roughly one-third of the world’s population.

Toxoplasma gondii must reside inside its host’s cells and secretes a variety of proteins to thwart the host’s immune responses and assist their own invasion and colonization. The researchers created a Toxoplasma gondii mutant strain that has a restricted ability to grow in cultured cells or cause sickness in mice, but can control the host immune system at the same time.

The researchers noted that injecting this mutant parasite directly into solid tumors causes inflammatory reactions in the injected tumors as well as malignancies located elsewhere in the mouse body. They also discovered that using this treatment method made tumors more susceptible to immune checkpoint inhibitors.

In mouse models of melanoma, Lewis lung carcinoma, and colon adenocarcinoma, this dual treatment greatly increased survival and reduced tumor growth.

“The use of a mutant version of Toxoplasma gondii in the treatment of certain tumors in mice models has been previously reported. What makes this study different is the confirmation that intratumoral injection with mutant Toxoplasma gondii strain boosts antitumor immunity and the effectiveness of checkpoint inhibition therapy,” said Dr Hany Elsheikha – one of the lead authors of the study.

“These are significant findings and are relevant to future tumor therapy. The marked reduction in tumor size and the significant improvement in the survival of mice that received this novel combinational therapy is promising but should be interpreted with caution as further research is needed.”

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