Multiplex Cytokine Analysis after Cyclophosphamide/Fludarabine Nonmyeloablative Allogeneic Hematopoeitic Cell Transplantation

Background: We previously reported a pattern of lymphocyte expansion in transplant recipients prior to neutrophil engraftment following cyclophosphamide-fludarabine (Cy/Flu) nonmyeloablative allotrans-plantation (NMAT) in humans. T-cells and NK with approximately 85-90% donor chimerism were the predominant leukocyte population detectable in peripheral circulation in patients with acute myeloid leukemia (AML)/myelodysplasia (MDS) between days +6 and +8. This observation appears unique and reproducible and the mechanism is unknown. In an exploratory study, we analyzed TH1, TH2 and homeostatic cytokines present on day +7 in the serum of engrafting patients by Multiplex.

Methods: Sixteen patients with a variety of hematological malignancies who underwent Cy/Flu NMAT according to a phase II protocol (NCT00975975) at Indiana University between 2009 and 2011 were included. Frozen serum samples collected from patients on day +7 were thawed and cytokine levels measured using a commercially available multiplex platform (MPXHCYTO-60K, Millipore Corp, Billerica, MA, USA). Samples were run in triplicate and compared against sample matrix alone; sample matrix alone was spiked with known levels of the specific cytokines and standardized quality controls revealed low and high ranges for each cytokine. Clinical parameters included age, diagnosis, donor source, stem cell dose, daily temperature, serum albumin and days to engraftment. Data were analyzed using SAS.

Results: Median age was 60 years. Hematological diseases included acute myeloid leukemia/myelodysplasia (n=8), concomitant myelodysplasia and multiple myeloma (n=1), chronic lymphocytic leukemia (n=3), non-Hodgkin’s lymphoma (n=1), cutaneous T-cell lymphoma (n=1), acute lymphoblastic leukemia (n=1) and primary myelofibrosis (n=1). Patients received peripheral blood mononuclear cell grafts from matched related (n=8) or unrelated (n=8) donors. Median CD34+ dose was 4.7x10⁸ cells/kg (range 2.0-8.1) and median CD3+ dose was 1.7x10⁸ cells/kg (range 0.8 to 4.3). Median time to engraftment was 13.5 days (range 10 to 18). Table-1 summarizes clinical features and levels of various cytokine at day +7. Ten patients had a fever (>38.2^oC) by day +7. Median baseline (day -7) albumin was 3.5 mg/dl (range 3.1 to 4.1). We observed a median decrease in albumin by 1.0 mg/dl (range 0.1 to 1.6; P<0.001) comparing baseline to day +7. Median day +7 cytokine levels were as follows: IFNγ, 5pg/dl; TNFα, 20pg/dl; IL-4, undetectable; IL-6, 68pg/dl; FLT3 ligand, 624pg/dl; IL-10, 59pg/dl; IL-15, 51pg/dl; IL-2, undetectable; IL-7, undetectable; sIL2-Rα, 1121pg/dl and IL-8, 73pg/dl.

Conclusion: Although confirmatory studies with larger numbers of patients are needed, this exploratory analysis of day +7 cytokine levels suggests that pre-engraftment lymphoid expansion following Cy/Flu NMAT is mediated predominantly by homeostatic proliferative mechanisms.

MUD: matched unrelated donor, MRD: matched related donor, Alb: Albumin, ANC: absolute neutrophil count, N/A: not available

*other activation/inflammatory cytokines