We present a case of severe Clostridium difficile infection (CDI) in a non-neutropenic allogeneic hematopoietic stem cell transplant recipient who was treated successfully with fecal microbiota therapy after standard pharmacologic therapy had failed. Following naso-jejunal instillation of donor stool, the patient's symptoms resolved within 48 h. Bowel resection was averted. This is the first case in the literature, to our knowledge, to describe fecal microbiota therapy in a profoundly immunocompromised host with severe CDI. We propose that fecal microbiota therapy be considered as a therapeutic option in immunosuppressed patients with refractory severe CDI.

3308 Poster Board III-196 The use of lineage-specific chimerism studies following allotransplantation has shown that low levels of donor T-cell chimerism can be seen following some preparative regimens despite good engraftment of donor myeloid-origin cells. Furthermore, low levels of early T-cell chimerism have been associated with eventual graft rejection, malignant relapse and poorer event-free survival [Maris et al Blood 102: 2021-2030 (2003); Saito et al Biol Blood Marrow Transplant 14: 1148-1155 (2008)]. There is no consensus regarding the management of such differential engraftment. Withdrawal of immunosuppression, DLI, and second transplant with repeat conditioning have all been used. We utilized a strategy of low dose DLI (initial dose 0.1-1 × 10e7 CD3+ cells/kg) without additional conditioning or withdrawal of immunosuppression in patients with donor T-cell chimerism < 50% following allotransplant who had no evidence of relapse/progression of malignancy. Nineteen consecutive patients treated this way between Nov 2005 and April 2009 were included in this analysis - median age 59 (range 36-63);15M, 4F; NHL 5, AML 5, MDS 3, CLL2, CML 2, MPS 2; donor =MRD 3, MUD 16; Preparative regimen for transplant- reduced intensity 18, myeloablative 1, and consisted of fludarabine/busulfan (11), fludarabine/cyclophosphamide (6), other (2). Alemtuzumab was used in the preparative regimen in 15 and rabbit antithymocyte globulin in 2. The first DLI was administered a median of 66 days post BMT (range 36-237). Median CD3+ and CD34+ cell dose was 1.0 ×10e7/kg (range 0.1-1) and 0.24 × 10e6 (0.02-0.74) respectively. Cryopreserved G-CSF mobilized cells collected at the time of BMT were used for the DLI in all patients. Median (range) donor chimerism in blood CD3+ cells and CD33+ cells prior to DLI was 14% (0-34%) and 100% (10-100%) respectively. Pre and post DLI donor T-cell chimerism is shown in the Figure below. Full donor CD3 chimerism (FDC) (>90% donor-derived CD3+ cells) was achieved after one DLI in 9 evaluable patients (50%) at a median 90 d post infusion (range 30-180 d). Eight patients received additional DLI (median 1 range 1-3) at a CD3+ cell dose up to 4 × 10e7/kg and 7 of these patients achieved FDC in CD3+ cells [total success rate in achieving FDC = 89%]. FDC was durable in all cases. Acute GVHD (none > gd 2 overall) developed in three evaluable patients following DLI (17% - median 43d [35-57d]) and chronic GVHD (extensive mild 1, moderate 8, severe 1) developed in ten patients (55% -median 119d [53-166d]). One patient died of chronic GVHD. With a median follow-up of 728d (135-1240d) estimated 2yr survival from DLI is 74%. Conclusion This strategy is highly effective at correcting poor donor T-cell chimerism without inducing severe GVHD. Disclosures No relevant conflicts of interest to declare.

1262 Steroid-refractory acute graft versus host disease (aGVHD) is associated with a poor prognosis. Although clinical responses occur to second line therapy they are associated with high rates of infection and dismal long-term survival. Blockade at 2 different points in the cytokine cascade with infliximab and daclizumab (double antibody therapy, DAT), along with aggressive infection prophylaxis may improve outcomes. We retrospectively reviewed our experience using DAT in steroid-refractory aGVHD. Between December 2005 and December 2009, 22 patients were treated of which 20 are evaluable. All patients had persistent or progressive aGVHD despite 1–2 mg/kg/d steroids for a median of 9 days (range 2–55). Five patients had failed 2nd line systemic aGVHD therapy and 1 patient failed 3rd line therapy prior to DAT. Combination therapy was given for aGVHD grade 2 (n=3), 3 (n=13), or 4 (n=4). GVHD involved the skin in 7 patients, the liver in 9 patients and GI tract in 16 patients. The median age at time of therapy was 55 years (range 29–69). Grafts were from HLA identical siblings (9), 10 locus matched unrelated donors (5), 9/10 locus matched unrelated donors (3), cord blood (2) or 5/10 haploidentical donor (1). The conditioning regimen was myeloablative in 10 patients, and either nonmyeloablative or reduced intensity in 10 patients. Indications for stem cell transplant were acute leukemia (7), chronic myelogenous leukemia (2), chronic lymphocytic leukemia (1), myelodysplastic syndrome (4), non-Hodgkins lymphoma (5), and multiple myeloma (1). Most patients received methotrexate (MTX) with tacrolimus (FK)(14) or mycophenolate (MMF) (4) for GVHD prophylaxis; one patient received MTX with FK and MMF and one FK alone. Fifteen patients developed aGVHD after the primary transplant and five after donor lymphocyte infusion. Daclizumab was given (1mg/kg) day 1,4,8,15, and 22, and infliximab (10mg/kg) days 1,8,15, and 22. Steroid therapy was aggressively tapered upon commencement of DAT. Maximal response achieved by day 60 post initiation of therapy was assessed. Five pts (25%) attained a CR (resolution of all symptoms), 10 (50%) PR (improvement in ≥ 1 organ & no progression in others), 2(10%) MR (improvement in ≥ 1 organ & deterioration or new symptoms in others) and 3 (15%) no response. Five patients received 1–2 additional courses of DAT at a median of 60 days. Three patients (15%) were concurrently on an investigational protocol utilizing mesenchymal stem cells. All patients received antifungal (azole with mold coverage or echinocandin), anti-Herpes virus, and Pneumocystis prophylaxis. Patients with gastrointestinal GVHD also received antibacterial prophylaxis irrespective of neutropenia. Patients were monitored once or twice weekly for CMV reactivation and received preemptive therapy upon reactivation. Only two patients had documented fungal infections: Mucormycosis in 1 and Candida parapsilosis in 1. Sixteen (80%) of patients had bacterial infections, including 21 gram-positive infections and 13 gram-negative infections. Viral infections, primarily CMV reactivation, occurred in 16 patients (80%). As of August 2010, 12 patients have died after a median of 102 days from initiation of DAT (range 14–658) (5 from relapsed or progressive disease, 3 from aGVHD, 2 from cGVHD, and 2 from organ failure). With a median follow up of 511 days for living patients, the estimated probability of survival at 6 months and 12 months is 55% and 50%, respectively. DAT is an effective therapy for steroid-refractory aGVHD. Survival beyond 6 months can be achieved in approximately half the patients using this strategy. Aggressive antifungal and antiviral prophylaxis may have contributed to this outcome. Disclosures: Off Label Use: Infliximab and daclizumab are not FDA approved for GVHD.

3371 Poster Board III-259 Background: Failure to achieve high levels of donor T-cell chimerism in the early period after RICT may be associated with eventual graft rejection, disease relapse and poor disease-free survival [Maris et al Blood 102:2021-2030 (2003); Saito et al Biol Blood Marrow Transplant 14:1148-1155 (2008)]. We hypothesized that pre-administration of reduced-dose rATG two weeks prior to stem cell transplant (SCT) would produce selective in-vivo depletion of host but not donor T-cells due to in-vivo decay of active rATG levels. Patients and methods: Twenty-two pts with HLA-identical sibling donors were enrolled on this study. The median age 57 yrs (24-68); F (n=10) M (n=12); NHL (n=9), MDS (n= 7), MPS (n=2), AML (n=2), HD (n=1), MM (n=1). Seven pts had a prior auto transplant. Disease status at transplant was CR (n=8), PR (n=4), HI (n=3), not in remission (n=5), untreated (n=2). CIBMTR risk stratification was high (n=12), intermediate (n=6) and low (n=4). RIC consisted of rATG 1 mg /kg d-16 & 3.5 mg/kg d-15, fludarabine 30 mg/m2/d (d-7 to -3), busulfan 130 mg/m2 IV (d -4, -3), and cylophosphamide 1.5 g/m2 d-2. Mobilized PBSC were infused on d 0. GVHD prophylaxis consisted of tacrolimus and methotrexate. All pts were admitted on d -16,-15 for rATG administration and were then discharged to receive the remaining therapy in the outpatient clinic. Results: Median active rATG levels at day -14, -7, and 0 were 4.4 mcg/mL (1.37-12.2), 1.35 mcg/mL (0.2-2.6), and 0.5 mcg/mL (0-3.2). Fifteen evaluable pts (83%) had a sub therapeutic active ATG level (<1 mcg/mL) on day 0. Of evaluable pts, the median (range) peripheral blood CD 3+ cell chimerism on day 15, 30, 60, 90 & 360 was 93% (75-100%), 95% (75-100%), 100% (87-100%), 100 (88-100%) and 100% (93-100%) respectively. Median CD 33+ cell chimerism was consistently > 95% (range 90-100%) at all time points. Readmission prior to d 100 occurred in 17 pts and was most commonly due to febrile neutropenia (n=7), GI toxicity (n=6) and acute GVHD (n=4). The median length of hospitalization was 5 days (range 1-34 days). Post transplant infections included CMV reactivation (n=5), Adenovirus (n=1), BK virus (n=3), Parainfluenza (n=1), HSV oral (n=1), Candida Parapsilosis (n=1), C.Difficile (n=3), Pseudomonas (n=4) Giardia (n=1), MRSE (n=17), MRSA (n=1) Gram positive organisms (other; n=9) and other bacteria (n=5). Estimated cumulative incidence of treatment related mortality (TRM) at d 100 and 1 year was 0% and 17.9%.The maximum cumulative incidence of aGVHD grade II-III and grade III-IV was 44% and 5% respectively. Chronic GVHD (all stages) developed in 70% of evaluable patients but was extensive severe for only 8%. One patient developed steroid refractory GVHD. Estimated probability of 2 year overall survival & progression-free survival are 59.9% and 39.8%. Cause of death included progression of malignancy (n=2), chronic GVHD (n=1), bacterial infection (n=1), pulmonary failure (n=1). Conclusions: Pre-administration of rATG (on d-16 and -15) with this RIC regimen results in sub-therapeutic serum active rATG levels on d 0 in the majority of patients thus avoiding significant in-vivo donor T-cell depletion. It produces high levels of early and sustained donor T-cell chimerism without an apparent increase in TRM or GVHD. Disclosures: Off Label Use: Anti-thymocyte globulin off label use for stem cell transplant. Bashey:Genzyme: Research Funding.