Anti CD22 CAR-T cell therapy (YaKe Biotech)

The investigators will conduct a phase II clinical trial of autologous humanized anti-CD22 chimeric antigen receptor T cells treating refractory or relapsed B acute lymphoblastic leukemia children in Beijing Boren Hospital. The study will be approved by the institutional review board of Beijing Boren Hospital, and informed consent will be obtained in accordance with the Declaration of Helsinki. All these participants will be matched the diagnostic criteria for (r/r) B-ALL according to the WHO classification and complete morphological evaluation, immunophenotype analysis by flow cytometry (FCM), cytogenetic analysis by routine G-banding karyotype analysis and leukemia fusion gene screening by multiplex nested reverse transcriptase-polymerase chain reaction (PCR). Participants will be eligible if they are heavily treated B-ALL who failed from re-induction chemotherapy after relapse or continued MRD+ for more than three months, and had positive CD22 expression on leukemia blasts by FCM (>95% CD19). After CAR T-cell infusion, clinical outcomes including overall survival (OS), Disease-free survival (DFS), adverse effects and relapse will be evaluated.