Hematopoiesis-restricted minor histocompatibility antigens HA-1- or HA-2-specific T cells can induce complete remissions of relapsed leukemia

Abstract

Donor lymphocyte infusion (DLI) into patients with a relapse of their leukemia or multiple myeloma after allogeneic stem cell transplantation (alloSCT) has been shown to be a successful treatment approach. The hematopoiesis-restricted minor histocompatibility antigens (mHAgs) HA-1 or HA-2 expressed on malignant cells of the recipient may serve as target antigens for alloreactive donor T cells. Recently we treated three mHAg HA-1- and/or HA-2-positive patients with a relapse of their disease after alloSCT with DLI from their mHAg HA-1- and/or HA-2-negative donors. Using HLA-A2HA-1 and HA-2 peptide tetrameric complexes we showed the emergence of HA-1- and HA-2-specific CD8(+) T cells in the blood of the recipients 5-7 weeks after DLI. The appearance of these tetramer-positive cells was followed immediately by a complete remission of the disease and restoration of 100% donor chimerism in each of the patients. Furthermore, cloned tetramer-positive T cells isolated during the clinical response specifically recognized HA-1 and HA-2 expressing malignant progenitor cells of the recipient and inhibited the growth of leukemic precursor cells in vitro. Thus, HA-1- and HA-2-specific cytotoxic T lymphocytes emerging in the blood of patients after DLI demonstrate graft-versus-leukemia or myeloma reactivity resulting in a durable remission. This finding implies that in vitro generated HA-1- and HA-2-specific cytotoxic T lymphocytes could be used as adoptive immunotherapy to treat hematological malignancies relapsing after alloSCT.

Figure 1

HA-1 and HA-2 tetramer⁺ T cells in peripheral blood from patient 1 in relation to clinical effect. (a) CD8⁺/tetramer⁺ T cells are expressed as absolute numbers per milliliter in peripheral blood (left y axis). ■, CD8⁺/HA-2 tetramer⁺ T cells; ♦, CD8⁺/HA-1 tetramer⁺ T cells; *, CD8⁺/HY-A2 tetramer⁺ T cells; ○, white blood cell count (WBC) × 10⁶ per ml in peripheral blood (expressed on the right y axis). The black arrow depicts the moment of DLI. (b) BCR/ABL (■) is expressed as the ratio of BCR/ABL/household gene porphobilinogen deaminase mRNA. The lower level of detection is ≤10⁻⁵.

Figure 2

HA-1 and HY/B7 tetramer⁺ T cells in peripheral blood from patient 2 in relation to clinical effect. See the legend to Fig. 1 for a description of symbols and abbreviations used. ▵, CD8⁺/HY-B7 tetramer⁺ T cells.

Figure 3

HA-1 tetramer⁺ T cells in peripheral blood from patient 3 in relation to clinical effect. (a) See the legends to Figs. 1 and 2 for a description of symbols and abbreviations used. (b) ♦, M protein is expressed in grams/liter in peripheral blood. The lower level of detection is <1 g/liter.

Figure 4

Percentage lysis of EBV-LCLs and CML cells from patient 1 by different CTL clones as measured in the ⁵¹Cr-release assay. (Left) Lysis of EBV-LCLs. (Right) Lysis of CML cells. Gray bars, 20-h incubation; white bars, 4-h incubation.

Figure 5

Percentage of growth inhibition by different CTL clones in the HPC growth-inhibition assay. Effector cells: (a) high-affinity anti-HA-1 CTL clone; (b) intermediate affinity anti-HA-1 CTL clone; (c and d) high-affinity anti-HA-2 CTL clones; (e) control anti-HLA-A1/HY CTL clone. Target cells: ♦, donor HPCs; ■, recipient CML HPCs before transplantation; ○, recipient CML HPCs at relapse; x, unrelated CML patient X; *, unrelated CML patient Y; +, unrelated CML patient Z. On the x axis the E/T ratio is shown. Tissue typing: CML-X ♀, HLA-A2, HA-1-positive, HA-2-positive; CML-Y ♂, HLA-A1, -A2, HA-1-positive, HA-2-negative; and CML-Z ♂, HLA-A2, HA-1-negative, HA-2-positive.