Immunologic Profiling of CSF in Subarachnoid Neurocysticercosis Reveals Specific Interleukin-10-Producing Cell Populations During Treatment.

Background and objectives: Subarachnoid neurocysticercosis (SANCC) is the most severe form of Taenia solium CNS infection and accounts for the majority of neurocysticercosis-associated mortality. Inflammation is important in the treatment of SANCC because overactivity can lead to serious complications, but excessive suppression may be counterproductive toward parasite eradication. A relative abundance of CSF IL-10 to IL-12 has been associated with increased treatment duration for patients with SANCC, suggesting that IL-10 plays an important role in this disease process. To better understand SANCC immunology and the major sources of IL-10 during anthelmintic treatment, we took an unbiased and comprehensive approach to phenotype the immune cell populations in the CSF and peripheral blood of patients with SANCC.

Methods: Eight samples of CSF cells collected from 5 patients with SANCC during treatment were evaluated using single-cell RNA sequencing. Matched CSF and peripheral blood mononuclear cells from 4 patients were assessed using flow cytometry. Staining for extracellular and intracellular markers allowed for the characterization of IL-10-producing T cells.

Results: The CSF during SANCC contains a diversity of immune cell populations including multiple myeloid and lymphoid populations. Although there were changes in the composition of CSF cells during treatment, the largest population at both early and late time points was CD4⁺ T cells. Within this population, we identified 3 sources of IL-10 unique to SANCC CSF compared with controls: natural regulatory T cells (nTregs), induced regulatory T cells (iTregs), and Th17 cells. The abundance and phenotype of these IL-10-producing populations differed between CSF and blood in patients with SANCC, but iTregs were the single most productive population in the CSF. During treatment, these IL-10 producers persisted in consistent proportions despite decreases in parasite antigen over time.

Discussion: This profile of immune cell populations in the CSF provides a comprehensive blueprint of the local and systemic immunology associated with SANCC. The identification of IL-10-producing cells in the CSF and peripheral blood deepens our understanding of the immunosuppressive phenotype that deters SANCC treatment success. Finally, the discovery that these IL-10 producers persist throughout treatment highlights the endurance of these populations in the CNS.