NK-Cell Recovery and Immune Reconstitution after Haploidentical Hematopoietic Cell Transplantation Using Either CD34 Selected Grafts and Adoptive NK-Cell Transfer or CD3/CD19 Depleted Grafts: Comparison of Two Strategies for NK Cell Based Immunotherapy.

NK-cells have been shown to play a pivotal role in haploidentical hematopoietic cell transplantation (HHCT) for engraftment, GvL effects and to combat infectious complications. Different strategies have been employed to hasten NK-cell recovery after HHCT. Here we compare the immune recovery of 17 patients after CD34 selected HHCT receiving additional adoptive CD3-depleted CD56-enriched NK cells 2 days after HHCT (adoptive NK-cells), with 18 patients receiving CD3/CD19 depleted grafts (CD3/CD19) for HHCT. Transplantations were performed at two different institutions with a median follow-up of >1 year. Conditioning consisted of 12 Gy TBI, thiotepa (10mg/kg), fludarabine (150 mg/m²) and OKT3 (day −4 to +2) in the group receiving CD34 selected grafts and adoptive NK-cell transfusions. All patients in the CD3/CD19 group received conditioning with fludarabine (150–200 mg/m²), thiotepa (10 mg/kg), melphalan (120 mg/m²) and OKT-3 (day −5 to +14). No postgrafting immunosuppression was used in both groups. Seven out of the 17 patients in the adoptive NK-cell group received IL-2 activated NK cells. Median age was 37 years in the adoptive NK-cell group compared to 40 years in the CD3/CD19 group. Diagnoses in the adoptive NK-cell group included AML (n=10), ALL (n=3), CML (n=2), and Hodgkin’s disease (n=1) and MDS (n=1). Diagnoses in the CD3/CD19 group were AML (n=10), ALL (n=5), NHL (n=1), CML (n=1) and multiple myeloma (n=1). The grafts contained a median of 12.5x10E6 CD34+ cells/kg and 1.1×10E4 CD3+ cells/kg in the CD34 selected group versus 9.2×10E6 CD34+cells/kg and 2.3×10E4 CD3+cells/kg in the CD3/CD19 group. The number of transferred CD56+ cells was 8.3×10E6/kg in the adoptive NK-cell group and 7.2×10E7/kg cells in the CD3/CD19 group. Hematopoietic recovery was similar in both groups. Among the patients receiving adoptive NK-cells we observed a striking difference in immune recovery between the patients receiving IL2-activated and those treated with non-activated NK cells: patients receiving activated NK cells showed significantly lower numbers of NK- and T cells during the first months post transplant (p=<0.05). In addition, we compared the immune recovery of the patients in the CD3/CD19 group and the 10 patients in the adoptive NK cells group receiving unstimulated NK-cells. There was a significant faster recovery of CD4⁺ T cells in the adoptive NK-cell group with a median day 40 count of 179 versus 2 cells/μl (p<0.05). However, patients in the CD3/CD19 group showed a significant faster and more sustained recovery of NK-cells with a median day 40 CD56+ count of 1464 versus 254 cells/μL (p<0.05). After day 50 no significant difference between the two groups was observed. The incidence of GvHD≥II was similar with 47% in the adoptive NK-cell group versus 50% in the CD3/CD19 group. In conclusion, patients receiving CD3/19 depleted grafts show a faster and more sustained NK-cell reconstitution but a slower T cell recovery in the early phase after transplant. The clinical impact of these differences warrants evaluation in further prospective studies.