A 2-step approach to myeloablative haploidentical stem cell transplantation: a phase 1/2 trial performed with optimized T-cell dosing.

Studies of haploidentical hematopoietic stem cell transplantation (HSCT) have identified threshold doses of T cells below which severe GVHD is usually absent. However, little is known regarding optimal T-cell dosing as it relates to engraftment, immune reconstitution, and relapse. To begin to address this question, we developed a 2-step myeloablative approach to haploidentical HSCT in which 27 patients conditioned with total body irradiation (TBI) were given a fixed dose of donor T cells (HSCT step 1), followed by cyclophosphamide (CY) for T-cell tolerization. A CD34-selected HSC product (HSCT step 2) was infused after CY. A dose of 2 × 10(8)/kg of T cells resulted in consistent engraftment, immune reconstitution, and acceptable rates of GVHD. Cumulative incidences of grade III-IV GVHD, nonrelapse mortality (NRM), and relapse-related mortality were 7.4%, 22.2%, and 29.6%, respectively. With a follow-up of 28-56 months, the 3-year probability of overall survival for the whole cohort is 48% and 75% in patients without disease at HSCT. In the context of CY tolerization, a high, fixed dose of haploidentical T cells was associated with encouraging outcomes, especially in good-risk patients, and can serve as the basis for further exploration and optimization of this 2-step approach. This study is registered at www.clinicaltrials.gov as NCT00429143

Acute Heart Transplant Rejection in the Presence of Apparently Weak, Non-Complement-Fixing Donor-Specific Antibodies Detected at the Time of Transplant

Poster presented at: American Society for Histocompatibility and Immunogenetics (ASHI) conference. AIM: A 66 year old female with an end-stage NYHA class IV inotrope-dependent, ischemic cardiomyopathy received a heart transplant on 9-12-09 from a doctor having antigens B13 and DR7. Pre-transplant antibody testing indicated only weakly positive, non-complement fixing donor-specific antibodies. The patient suffered a cardiac arrest on POD#6 and was resuscitated. She was in cardiogenic shock from allograft failure and subsequently expired on POD#9 of multiorgan failure due to acute humoral rejection . These antibodies were investigated further. METHODS: Antibodies were evaluated using Labscreen PRA (One Lambda), Labscreen Single Antigen (One Lambda) beads, and C1q Single Antigen (One Lambda) beads, and crossmatching was performed using standard T and B cell CDC and flow cytometry methods. RESULTS: Pre-transplant antibody studies (Labscreen PRA) had shown the presence of clearly defined antibodies to B27, DR4 and a possible weak anti-DR7. Retrospective Labscreen Single Antigen (SA) (One Lambda) testing revealed antibodies to B13 and DR7, both donor-specific antibodies. MFI values were 2000 for B13 and 5000 for DR7. The pre-transplant crossmatches (CDC and flow cytometry) were negative except for a positive B cell CDC. The patient received blood products on POD#3 and was noted to be in acute renal insufficiency. Crossmatching on POD#3 showed only a weakly positive T flow crossmatch and negative DSA. However, SA antibody studies on POD#6 showed high MFI values of 19,000 (B13) and 23,000 (DR7), and strongly positive T and B CDC and flow crossmatches. C1q studies of sera from POD#0 and #3 showed the DSA were non-complement fixing. However, by POD#6 the DS antibodies were not clearly complement-fixing. The patient expired on POD#9. Myocardium tissue from the left ventricle taken at autopsy showed positive staining for C4d

Haploidentical Hematopoietic Stem Cell Transplantation: Rationale, Development, and Jefferson’s Method

INTRODUCTION There are many indications for hematopoietic stem cell transplantation. In addition to hematologic malignancies, transplants are performed in certain non-hematologic malignancies, for marrow disorders such as Sickle Cell Anemia, and for various inherited disorders such as SCID. Traditionally, transplants have been performed between donors and recipients that are a complete HLA match (typically matched siblings). That is, patients have identical HLA alleles on both copies of chromosome 6. HLA alleles code for major histocompatibility complex molecules, which are the proteins that cause transplant rejection when a mismatch between donor and recipient is present. Thus, matched transplants have been historically favored in order to avoid both rejection of the graft by the recipient, as well as disease in the recipient due to graft vs. host disease (GVHD) in which the donor immune cells attack the host’s tissues. However, matched transplants have several disadvantages. First, only about 30% of patients requiring a transplant have a matched sibling available as a donor. For the remaining 70%, the search for an unrelated matched donor can be time consuming, expensive, and especially difficult for patients of minority racial and ethnic groups. Many conditions requiring transplant are so acute that patients often die during the search for a donor. Accordingly, several institutions pioneered the research and implementation of haploidentical transplants as a viable option. A haploidentical transplant refers to the situation when the recipient and donor have identical alleles on one copy of chromosome 6, but not on the other. In terms of advantages, haploidentical transplants greatly increase the pool of available donors since biological parents are by definition haploidentical to all of their children, and there is a much greater chance that a sibling will be a half match than a full match. Additionally, haploidentical transplants allow for a critical Graft vs. Tumor effect (GVT), whereby the donor’s immune cells attack the recipient’s cancer cells because of the HLA mismatch present. The caveat, however, is that this mismatch also promotes GVHD that can be lethal. Accordingly, different institutions have attempted various methods of manipulating the donor graft to try and maximize the GVT effect while minimizing GVHD. Jefferson’s regimen is one such method that has had success thus far

Transplant Glomerulopathy in the Absence of Donor Specific Antibodies

Conclusions: Half of our 50 patients with TG documented by EM had no DSAs or positive C4d staining in PTCs. Almost 70% of the patients evidenced PTC basement membrane multilayering. These patients were all diagnosed with chronic active CMR independently of the presence of TG. Cellular rejection mechanisms are likely the cause of the TG in this group. Patients with TG and DSAs are at greater risk for episodes of acute AMR and CMR. C4d staining of PTCs was evident in less than 40% and in the glomeruli in less than half. Interestingly, 25 of the 26 DSA+ patients were independently diagnosed with chronic active CMR