Single-cell profiling of CAR-T CD19 cell phenotypes and immune system dynamics in pediatric BCP-ALL

Area of Science:

• Immunology
• Oncology
• Cell Therapy

Background:

• Chimeric Antigen Receptor T-cell (CAR-T) therapy targeting CD19 has revolutionized treatment for relapsed/refractory B-cell precursor acute lymphoblastic leukemia (BCP-ALL).
• The phenotypic diversity of CAR+ T-cells and their interactions within the immune microenvironment are not fully elucidated.
• Optimizing CAR-T therapy requires a deeper understanding of T-cell subsets and their persistence post-infusion.

Purpose of the Study:

• To characterize CAR+ T-cell subsets and their persistence in pediatric BCP-ALL patients receiving tisagenlecleucel.
• To investigate the dynamic changes in the peripheral blood mononuclear cell (PBMC) immune system following CAR-T infusion.
• To identify associations between CAR+ T-cell phenotypes, immune system alterations, and clinical outcomes, including cytokine release syndrome (CRS).

Main Methods:

• Mass cytometry was employed to analyze CAR+ T-cell composition and PBMC immune profiles in 19 pediatric BCP-ALL patients treated with tisagenlecleucel.
• Quantitative PCR (qPCR) validated CAR+ T-cell levels.
• Machine learning algorithms classified T-cell phenotypes, and statistical analyses examined correlations between immune parameters and clinical outcomes.

Main Results:

• Infusion products showed a predominance of CD4+ Central Memory and Treg memory cells, with CD8+ subsets expanding post-infusion and Treg cells declining significantly.
• PBMC analysis revealed increased monocyte and NK cell counts after infusion; however, patients experiencing CRS had distinct monocyte dynamics and lower pre-infusion NK cell levels.
• CRS correlated with specific CAR+ CD8+ Terminal Effector and MAIT/NKT cell frequencies in infusion products, while CAR+ composition did not link to disease burden or overall outcomes.

Conclusions:

• This study details CAR-T CD19 cell composition and post-infusion dynamics in pediatric BCP-ALL, revealing significant shifts in T-cell subsets and the broader immune system.
• The observed changes in CAR+ T-cells and immune cells like monocytes and NK cells are associated with clinical responses, including CRS.
• These findings underscore the critical role of the immune system in CAR-T therapy outcomes and offer insights for optimizing treatment strategies in pediatric BCP-ALL.