The role of purine analogues in low-intensity regimens with allogeneic hematopoietic stem cell transplantation

Extracorporeal photopheresis combined with pentostatin in the conditioning regimen for canine hematopoietic cell transplantation does not prevent GVHD

Extracorporeal photopheresis (ECP) and the purine analog pentostatin exert potent immunomodulatory effects. We evaluated the use of these treatment modalities to prevent GVHD in a canine model of unrelated dog leukocyte Ag-mismatched hematopoietic cell transplantation, after conditioning with 920 cGy TBI. We have shown previously in this model that 36/40 dogs given MTX alone as postgrafting immunosuppression engrafted and that 25 of 40 dogs had severe GVHD and median survival of 21 days. In the current study, nine dogs received conditioning with 920 cGy TBI and postgrafting MTX either with ECP on days -2 to -1 alone (n=5) or ECP on days -6 and -5 combined with two doses of pentostatin (days -4 to -3) (n=4). Seven of nine dogs achieved engraftment. Six dogs developed severe acute GVHD (four in the group with ECP alone and two with pentostatin and ECP). We failed to demonstrate a positive impact of ECP and pentostatin for the prevention of GVHD compared with historical control dogs.

Advances in haematological pharmacotherapy in 21st century

Last quarter of twentieth century and the first 10 years of 21st century has seen phenomenal development in haematological pharmacotherapy. Tailor made chemotherapeutic agents, vast array of monoclonal antibodies, epigenetic modifiers, growth factors for red cells white cells and platelets, peptidomimetics as growth factors, newer thrombin inhibitors, safer plasma derived protein molecules, recombinant molecules, newer immunomodulators, enzyme replacement therapy and above all a plethora of targetted molecules targeting innumerable pathways involved in cell division, growth, proliferation and apoptosis has given immense number of clinically usable molecules in the hand of modern haematologists to treat diverse hitherto untreatable haematological disorders effectively. In addition many old molecules are finding newer uses in diverse fields, thalidomide as an antiangiogenic molecule is a prime example of this genre. Present overview has tried to capture this rapidly evolving area in a broad canvas without going into details of indications and contraindications of the use of various drugs.

Extracorporeal photopheresis in addition to pentostatin in conditioning for canine hematopoietic cell transplantation: role in engraftment

Extracorporeal photopheresis (ECP) and the purine analog pentostatin exert potent immunomodulatory effects, but have not been evaluated for their ability to enhance engraftment of hematopoietic stem cells. We evaluated, in a canine model of dog leukocyte antigen (DLA)-identical hematopoietic cell transplantation (HCT), whether ECP in combination with pentostatin could enhance engraftment using a nonmyeloablative regimen consisting of 100 cGy TBI and postgrafting immunosuppression with mycophenolate mofetil and CYA. We have shown previously that with 100 cGy TBI alone as conditioning, all of the six dogs rejected their grafts 2-12 weeks after HCT. With the addition of pentostatin to 100 cGy TBI, 6 of 10 dogs rejected their graft. We now tested the additional use of ECP alone (n=2) or ECP and 3-6 doses of pentostatin (n=7) before 100 cGy TBI and HCT. Eight out of nine dogs rejected their grafts within 6-11 weeks after HCT. Compared with data without ECP, we failed to demonstrate a positive impact of the use of either ECP or pentostatin for prevention of rejection.

Development of novel major histocompatibility complex class I and class II-deficient NOD-SCID IL2R gamma chain knockout mice for modeling human xenogeneic graft-versus-host disease

Immunodeficient mice have been used as recipients of human peripheral blood mononuclear cells (PBMC) for in vivo analyses of human xeno-graft-versus-host disease (GVHD). This xeno-GVHD model system in many ways mimics the human disease. The model system is established by intravenous or intraperitoneal injection of human PBMC or spleen cells into unconditioned or irradiated immunodeficient recipient mice. Recently, the development of several stocks of immunodeficient Prkdc ( scid ) (scid) and recombination activating 1 or 2 gene (Rag1 or Rag2) knockout mice bearing a targeted mutation in the gene encoding the IL2 receptor gamma chain (IL2rgamma) have been reported. The addition of the mutated IL2rgamma gene onto an immunodeficient mouse stock facilitates heightened engraftment with human PBMC. Stocks of mice with mutations in the IL2rgamma gene have been studied in several laboratories on NOD-scid, NOD-Rag1 ( null ), BALB/c-Rag1 ( null ), BALB/c-Rag2 ( null ), and Stock-H2(d)-Rag2 ( null ) strain backgrounds. Parameters to induce human xeno-GVHD in H2(d)-Rag2 ( null ) IL2rgamma ( null ) mice have been published, but variability in the frequency of disease and kinetics of GVHD were observed. The availability of the NOD-scid IL2rgamma ( null ) stock that engrafts more readily with human PBMC than does the Stock-H2(d)-Rag2 ( null ) IL2rgamma ( null ) stock should lead to a more reproducible humanized mouse model of GVHD and for the use in drug evaluation and validation. Furthermore, GVHD in human PBMC-engrafted scid mice has been postulated to result predominately from a human anti-mouse major histocompatibility complex (MHC) class II reactivity. Our recent development of NOD-scid IL2rgamma ( null ) beta2m ( null ) and NOD-scid IL2rgamma ( null ) Ab ( null ) stocks of mice now make it possible to investigate directly the role of host MHC class I and class II in the pathogenesis of GVHD in humanized mice using NOD-scid IL2rgamma ( null ) stocks that engraft at high levels with human PBMC and are deficient in murine MHC class I, class II, or both classes of MHC molecules.

How I treat refractory acute GVHD

Graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT) is associated with considerable morbidity and mortality, particularly in patients who do not respond to primary therapy, which usually consists of glucocorticoids (steroids). Approaches to therapy of acute GVHD refractory to "standard" doses of steroids have ranged from increasing the dose of steroids to the addition of polyclonal or monoclonal antibodies, the use of immunotoxins, additional immunosuppressive/chemotherapeutic interventions, phototherapy, and other means. While many pilot studies have yielded encouraging response rates, in most of these studies long-term survival was not improved in comparison with that seen with the use of steroids alone. A major reason for failure has been the high rate of infections, including invasive fungal, bacterial, and viral infections. It is difficult to conduct controlled prospective trials in the setting of steroid-refractory GVHD, and a custom-tailored therapy dependent upon the time after HCT, specific organ manifestations of GVHD, and severity is appropriate. All patients being treated for GVHD should also receive intensive prophylaxis against infectious complications.