This is a single center, open-label ,phase 1/2 study to evaluate the safety and efficacy of targeted CD19/CD22 chimeric antigen receptor engineered T cell immunotherapy (CART) in the treatment of CD19/CD22 positive Relapsed or Refractory B-Cell Acute Lymphoblastic Leukemia.

The patients will receive infusion of CART cells targeting CD19 and CD22 to confirm the safety and efficacy of CD19/CD22 CART Cells in Relapsed or Refractory B-Cell Acute Lymphoblastic Leukemia.

Inclusion Criteria:

• Male or female patients with CD19+/CD22+ relapsed/refractory B-cell acute lymphoblastic leukemia who have a dismal prognosis (estimated survival from several months to <2 year). The study will enroll 20 evaluable patients as follows:
• Age 6-65 years.
• Left ventricular ejection fractions≥ 0.5 by echocardiography.
• Creatinine < 1.6 mg/dL.
• Aspartate aminotransferase/aspartate aminotransferase < 3x upper limit of normal.
• Bilirubin <2.0 mg/dL.
• Karnofsky performance status ≥ 60
• Expected survival time ≥ 3 months (according to investigator's judgement)

Exclusion Criteria:

• Pregnant or lactating women.
• Uncontrolled active infection.
• Active hepatitis B or hepatitis C infection.
• Class III/IV cardiovascular disability according to the New York Heart Association Classification.
• HIV infection.
• Patients with history of seizure
• Active central nervous system leukemia