Toxoplasma gondii infection supports the infiltration of T cells into brain tumors

Primary brain tumors, residing behind the blood-brain-barrier (BBB), have few infiltrated T cells. We hypothesized that Toxoplasma gondii, a microorganism that naturally traffics to the brain to elicit a Th1 response, can promote T cell infiltration into brain tumors. Using a mouse genetic model for medulloblastoma, we found that T. gondii infection was well-controlled in tumor-bearing mice, induced robust infiltration of T cells into the tumor, and led to myeloid cell transcriptional reprogramming toward a T cell-supportive state. The study demonstrates that the immune modulatory capacity of T. gondii could be leveraged to promote brain tumor immunotherapy through future efforts. To study the effect of T. gondii infection over the transcriptional profile of the myeloid populations in the tumors, myeloid cells were enriched from the tumors of uninfected (injected with PBS) or infected tumor-bearing mice (n=5 per group). Gene expression analysis was then performed on the RNA-seq data obtained from the samples.