An immune-mediated anti-tumor response is the ultimate goal of allogeneic transplantation for relapsed, refractory malignancies. We developed a transplant protocol with less toxicity compared with standard allogeneic transplantation. We utilize multiple donor lymphocyte infusions after nonmyeloablative HLA-haploidentical stem cell transplantation for refractory disease. We have performed a total of 41 HLA-mismatched transplants with escalation of the CD3+ dose to 2×108 cells/kg using G-CSF primed product, with a conditioning regimen of 100cGy total body irradiation (TBI). Our phase I/II study had 26 with hematologic malignancies. This therapy results in loss of detectable macrochimerism. Despite this, 13 responses, six major, occurred outside of macrochimerism. We have observed a new infusion related clinical entity named haploimmunostorm (HIS), observed after infusion. This syndrome occurred in 26 out of 30 (87%) patients with a CD3+ dose more than 108 cells/kg. In the syndrome, a constellation of symptoms occurred, some with variable penetrance, in which hyperpyrexia and malaise were a constant feature occurring as early as 4 hrs after cell infusion (median of 14 hrs). A morbilliform rash was seen in 40% of patients. Biopsies revealed no evidence of hyperacute or acute GVHD. Diarrhea was present in a 20% of patients; biopsies taken also failed to show any evidence of GVHD. Transient elevations of liver enzymes occurred in 40% of the patients usually. Steroids were used successfully if the HIS syndrome lasted more than 72 hrs. We used a Bioplex machine and analyzed 17-separate cytokine levels serially in these patients beginning with pre-treatment levels. Cytokine level analysis showed a cluster of cytokines that had up to a 1100 fold level increase compared with baseline pretreatment cytokine levels with significant increases of at least 10 fold in IFN-g, IL-10, IL-13, IL-2, IL-5, IL-6, IL-7, IL-8, MCP-1, and MIP-1b. This syndrome appears to be immunologically based and represents neither hyperacute nor acute GVHD. This syndrome is different than an engraftment syndrome reported in some patients undergoing autologous transplant with a different cluster of cytokine elevation (IL-6, IL-8, IL-10, IFN-g, MCP-1, MIP-1b) compared with (IL-1, IL-2, IL-8, TNFa, IFNg) for engraftment syndrome Engraftment syndrome occurs at time of engraftment, opposed to HIS in which may be a rejection syndrome. HIS deviates from engraftment syndrome with absence of noncardiogenic edema, pulmonary infiltrates, renal insufficiency weight gain and encephalopathy. The skin and intestinal biopsy results are distinctly different than GVHD or engraftment syndrome. HIS may be critical to our observed tumor responses. The increased presence of MCP-1 and MIB-1b, which up-regulate NK cell function and recruitment, suggests that NK cells have some role in this syndrome and are possibly mediating tumor response, essentially breaking host tumor tolerance. In summary, we have observed a new clinical entity that was not previously seen and is a result of the donors having a relatively intact immune system at the time of cell infusion. TBI of 100cGy followed by HLA-haploidentical transplant is a biologically active therapy for refractory hematologic disease. The responses outside of chimerism are intriguing and may be related to marrow rejection and or a unique type of cytokine storm. These data further indicate that persistent donor chimerism may not be necessary for durable anti-tumor response. The rejection of donor derived cells, in concert with elevations of specific cytokines, may represent a novel therapeutic approach for hematological malignancies.

Disclosure:Research Funding: NIH, COBRE, K08-Colvin; NIH, COBRE, R01-Quesenberry.