Mycolicibacterium brumae Is a Safe and Non-Toxic Immunomodulatory Agent for Cancer Treatment.

Intravesical Mycobacterium bovisBacillus Calmette-Guerin (BCG) immunotherapy remains the gold-standard treatment for non-muscle-invasive bladder cancer patients, even though half of the patients develop adverse events to this therapy. On exploring BCG-alternative therapies,Mycolicibacterium brumae, a nontuberculous mycobacterium, has shown outstanding anti-tumor and immunomodulatory capabilities. As no infections due toM. brumaein humans, animals, or plants have been described, the safety and/or toxicity of this mycobacterium have not been previously addressed. In the present study, an analysis was made ofM. brumae- and BCG-intravenously-infected severe combined immunodeficient (SCID) mice,M. brumae-intravesically-treated BALB/c mice, and intrahemacoelic-infected-Galleria mellonellalarvae. Organs from infected mice and the hemolymph from larvae were processed to count bacterial burden. Blood samples from mice were also taken, and a wide range of hematological and biochemical parameters were analyzed. Finally, histopathological alterations in mouse tissues were evaluated. Our results demonstrate the safety and non-toxic profile ofM. brumae. Differences were observed in the biochemical, hematological and histopathological analysis betweenM. brumaeand BCG-infected mice, as well as survival curves rates and colony forming units (CFU) counts in both animal models.M. brumaeconstitutes a safe therapeutic biological agent, overcoming the safety and toxicity disadvantages presented by BCG in both mice andG. mellonellaanimal models.