Cytokine Environement Analysis During Allogeneic Hematopoietic Stem Cell Transplantation for Inherited Diseases
Authors: Touzot Fabien , Fiema Bryan , Paczesny Sophie , Andre-Schmutz Isabelle , Helley Dominique , Moshous Despina , De Chappedelaine Corinne , Blanche Stephane , Fischer Alain , Cavazzana-Calvo Marina 
Published: October 2019

Abstract
Abstract 4484
Hematopoietic stem cell transplantation (HSCT) is the treatment for an increasing number of inherited diseases. Graft rejection and acute Graft Versus Host Disease (GVHD) are known to be the two major complications of this procedure. A high frequency of graft rejection is observed particularly in patients with inflammatory conditions associated with congenital metabolic diseases, IFN-gR1 deficiency, familial hemophagocytic lymphohistiocytosis. GVHD results from immunological attack on target recipient organs (skin, liver and gut) by donor allogeneic T cells that are transferred along with the allograft. A better understanding of the patients' inflammatory environment in the course of HSCT may allow for the establishment of predictive markers for the occurrence of engraftment or GVHD and the improvement of conditioning regimens and post-transplant immunosuppressive therapy.

Methods:
All pediatric patients treated in the Department of Immuno-Hematology at the Necker Hospital who received allogeneic HSCT after full intensity conditioning regimen for nonmalignant disorders including inherited immunodeficiencies, metabolic diseases or hemoglobinopathies are eligible for inclusion.
Plasma samples are collected before conditioning (day-15), at the time of transplant (day 0), at day+15 and day+30 post-HSCT.
Validated markers of GVHD (Elafin, Reg3α, and ST2) as well as pro-inflammatory, anti-inflammatory, and angiogenic cytokines were analyzed, respectively, using sequential enzyme-linked immunosorbent assays and Luminex technology, which enables the determination of large numbers of cytokines in very small amounts of childrens' plasma. Engraftment was assessed on the presence of full donor chimerism, GVHD upon clinical, biological and histopathological data.

Results:
From April 2011 to March 2012, 15 patients were included (8 males and 7 females with an age ranging from 4 months to 9 years). Five patients presented with severe combined immunodeficiencies, three with chronic granulomatous disease, five with metabolic diseases (three Hurler and two osteopetrosis), one with congenital aplastic anemia and one with sickle cell diseaseConditioning regimen consisted of Busulfan/Fludarabin/ATG for ten patients, Busulfan/Fludarabin/Thiotepa/ATG for four patients and Busulfan/Cyclophosphamid/ATG in one. Donors were matched unrelated (n=6), 4 matched related (n=4), haplo-identical (n=4), and with intrafamilial mismatched donor (n=1). Acute graft rejection was observed in 2 of 15 patients and sustained engraftment in 13 of 15. Acute GVHD was observed in 6 of 15 patient occurring between day+10 and day+45 [grade 1 (n=1), grade 3 (n=3) and grade 4 (n=2)].
At day+30, we found significantly higher plasma concentrations of IFNγ, TNFα, ST2, and VEGF in patients with GVHD as compared to patients without GVHD. TNFα was the only cytokine for which the plasma concentrations was already significantly higher at day+15 in patients with GVHD versus patients without GVHD. No statistically significant differences in plasma concentrations of IL-4, IL-6, TGFβ, IL-7, IL-8, IL-12, IL-13 and IL-17 were observed.
The cytokine that appeared to differentiate patients with GVHD and patients without GVHD the most was IFN-α2 which had plasma concentrations that were consistently and significantly higher in patients without GVHD as compared to patients with GVHD from day-15 to day+15.

Conclusion:
These results confirm the Th1 associated profile of acute GVHD and the importance of endothelial dysfunction in GVHD, as suggested by increased concentrations of ST2 and VEGF in patients with GVHD. The potential forIFN-α2 as a predictive marker of GVHD in our population needs further confirmation through additional inclusions. A larger population is also needed to determine if a specific cytokine milieu is associated with other common HSCT complications seen in our population such as graft rejection and vascular complications such as sinusoidal obstructive syndrome of the liver and pulmonary arterial hypertension.

Disclosures:
No relevant conflicts of interest to declare.