Successful hematopoietic stem cell transplantation for osteopetrosis using reduced intensity conditioning

BACKGROUND

Infantile malignant osteopetrosis (IMO) is an autosomal recessive condition characterized by defective osteoclast activity, with hematopoietic bone marrow transplant being the only available cure. Over the past several years, new conditioning regimes and donor options have emerged, thus extending the possibility of cure to a greater number of patients and improving the outcomes of bone marrow transplant. Here we detail the outcomes of bone marrow transplant in a cohort of 31 patients treated with a combination of fludarabine, treosulphan, thiotepa, and antithymocyte globulin.

PROCEDURES

Thirty-one patients with IMO who underwent hematopoietic stem cell transplantation with fludarabine, treosulphan, thiotepa, and antithymocyte globulin at our center from 2012 to 2017 are retrospectively reviewed in this study. Twenty-six patients were transplanted from 10/10 matched donors (13 from siblings, 11 from unrelated, and two from extended family donors), four from 9/10 matched unrelated donors, and one from a 9/10 matched family donor.

RESULTS

Overall survival was 100% with a median follow-up of 363 days (range 74-1891). There were 12 cases of acute graft versus host disease (GvHD) (38.7%), no cases of veno-occlusive disease, and eight cases of hypercalcemia (25.8%). Almost 80% of patients suffered viral reactivations with two cases of Epstein-Barr-virus-driven post-transplant lymphoproliferative disease. All cases of GvHD and viral reactivation were successfully treated.

CONCLUSIONS

We conclude that transplantation in children with IMO using fludarabine, treosulphan, thiotepa, and antithymocyte globulin is safe and effective and should be performed as early as possible following diagnosis, prior to the development of severe disease sequelae.

Parenteral administration of an activating monoclonal antibody to the alpha1beta1 integrin in dogs

In mice, monoclonal antibody (mAb) to the alpha1 integrin abrogate gastro-intestinal damage during graft-versus-host-disease (GVHD), suggesting anti alpha1 mAb as candidates for treatment in humans as well. Our current data show that one such reagent, mAb 1B3.1, when immobilized to plastic wells via rabbit- anti murine (ram) immunoglobulin (Ig) induces a protein kinase-dependent spreading of activated human T cells. Furthermore, it significantly increases the proliferative response, and expression of interleukin-2 (IL-2) receptors (R) and CD69, of resting T cells, expressing minimal integrin on the cell surface, to sub-optimal stimulation by anti-CD3 mAb. We found, in addition, that mAb 1B3.1 a) immuno-precipitates alpha1beta1 integrins from cell-surface iodinated canine epithelial cells b) is highly reactive with canine T cells after their activation and c) inhibits adhesion of canine T cells to collagen IV. Despite the potential ability of the mAb to co-activate T cells in vitro, two dogs that received 4 injections of 0.5-0.3 mg/Kg of mAb 1B3.1 remained healthy, developing only marginal transient lymphopenia. Injection of 0.75mg/Kg in a third dog induced a more marked lymphopenia, and an additional dose of 1.0 mg/Kg 2 weeks later was followed by gastrointestinal hemorrhage. importantly, the lymphopenia was associated with a greater and more persistent decrease of CD8+ than of CD4+ T cells, leading to an increase in the CD4/CD8 ratio 24 hours after the injection. Thus, despite it's co-activating effects in vitro, administration of this mAb in vivo is feasible when appropriately dosed, and may have immuno-modulatory effects.