Monitoring of GRAFT Versus Leukemia Effect with CD34+ Specific DONOR Chimerism Analysis

Introduction: Success of allogeneic hematopoietic stem cell transplant (allo-HSCT) for patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) largely depends on graft versus leukemia (GVL) effect.  Although GVL cannot be directly measured in the clinical setting, its development is frequently associated with the development of chronic graft versus host disease (cGVHD). Here we describe the assay, which allows monitoring of both minimal residual disease (MRD) and GVL in MDS and AML patients after allo-HCT.

 Methods: MRD was monitored in high risk patients with CD34+ MDS and AML by monthly peripheral blood CD34+ specific donor chimerism (PB CD34+ DC) analysis  starting at day +30 following allo-HCT. To obtain PB CD34+ DC, CD34+ cells were positively selected by immunomagnetic isolation from peripheral blood followed by fluorescence-activated cell sorting.  Highly purified CD34+ cells (>95%) were subsequently evaluated for percentage of donor DNA contribution by short tandem repeat analysis.

Results: Between September 2011 and July 2013 subjects with  MDS or AML were monitored monthly by PB CD34+ DC analysis. A rapid and steady decline in CD34+ donor chimerism was detected in all study participants who developed hematologic relapse (Figure 1).  However, in 2 other patients, development of extensive c GVHD coincided with rapid reversion of declining PB CD34+ DC. Restoration of PB CD34+ DC after cGVHD was associated with development of potent GVL effect because both patients have remained disease free for 12 and 15 months, respectively (Fig2).

  

Conclusions: Declining PB CD34+ DC associates with higher risk for relapsed disease after allo-HCT.  MRD and GVL can be monitored serially by a non-invasive PB CD34+ DC assay. GVL associates with cGVHD in patients with MDS and AML. Monitoring of PB CD34+ DC may identify at-risk patients eligible for early withdrawal of immunosuppression or post-transplant allograft modulation.