Tumor-specific Ab-mediated targeting of MHC-peptide complexes induces regression of human tumor xenografts in vivo

A cancer immunotherapy strategy is described herein that combines the advantage of the well established tumor targeting capabilities of high-affinity recombinant fragments of Abs with the known efficient, specific, and potent killing ability of CD8 T lymphocytes directed against highly antigenic MHC-peptide complexes. Structurally, it consists of a previously uncharacterized class of recombinant chimerical molecules created by the genetic fusion of single-chain (sc) Fv Ab fragments, specific for tumor cell surface antigens, to monomeric scHLA-A2 complexes containing immunodominant tumor- or viral-specific peptides. The fusion protein can induce very efficiently tumor cell lysis, regardless of the expression of self peptide-MHC complexes. Moreover, these molecules exhibited very potent antitumor activity in vivo in nude mice bearing preestablished human tumor xenografts. These in vitro and in vivo results suggest that recombinant scFv-MHC-peptide fusion molecules could represent an approach to immunotherapy, bridging Ab and T lymphocyte attack on cancer cells.     

Successful transplantation of haploidentically mismatched peripheral blood stem cells using CD133+-purified stem cells

OBJECTIVE: For recipients of haploidentically mismatched stem cell allografts, T-cell depletion is mandatory to prevent lethal graft-vs-host disease (GVHD). Prevention of GVHD can be accomplished by negative selection of T cells or positive selection of stem cells. Recently, a new method for positive selection of stem cells was introduced using monoclonal antibodies against CD133 antigen. We report five cases of successful application of immunomagnetic separation of CD133+ stem cells for haploidentically mismatched allogeneic stem cell transplantation. METHODS: Five patients with high-risk hematological malignancies, ages 7 to 63 years old (median, 17 years), underwent peripheral blood stem cell transplantation from haploidentically mismatched related donors. Conditioning protocol was tailored according to patient clinical situation and included combination of treosulfan/fludarabine/thiotepa/melphalan/Mabcampath. Two patients did not get thiotepa. One of them received a protocol that included infusion of 4.4 x 10(7) blood mononuclear cells from the donor (day -9), followed by a combination of fludarabine/cyclophosphamide/busulfex/MabCampath. Separation of CD133+ stem cells was done using CliniMACS with Miltenyi's CD133 reagent. RESULTS: The procedure was well tolerated by all patients. Early 3-lineage engraftment was documented and none exhibited immune-mediated rejection. Time to recovery of absolute neutrophils count above 0.5 x 10(9)/L and 1.0 x 10(9)/L was 10 to 15 days (median, 14) and 11 to 29 days (median, 15), respectively. Time for platelet recovery to values greater than 20 x 10(9)/L and greater than 50 x 10(9)/L ranged from 12 to 25 days (median, 13.5), and from 14 to 34 days (median, 16), respectively. Transplant-related mortality did not occur in any of the patients. CONCLUSION: Our successful pilot trial suggests that positive selection of CD133+ stem cells may be a useful method for safe transplantation with haploidentically mismatched stem cell allografts while avoiding lethal acute and chronic GVHD. Future studies will be required to assess the clinical benefits of stem cell purification with CD133+ in comparison with CD34+ stem cells.     

Identification of a second aryl phosphate-binding site in protein-tyrosine phosphatase 1B: A paradigm for inhibitor design

The structure of the catalytically inactive mutant (C215S) of the human protein-tyrosine phosphatase 1B (PTP1B) has been solved to high resolution in two complexes. In the first, crystals were grown in the presence of bis-(para-phosphophenyl) methane (BPPM), a synthetic high-affinity low-molecular weight nonpeptidic substrate (K_m = 16 μM), and the structure was refined to an R-factor of 18.2% at 1.9 Å resolution. In the second, crystals were grown in a saturating concentration of phosphotyrosine (pTyr), and the structure was refined to an R-factor of 18.1% at 1.85 Å. Difference Fourier maps showed that BPPM binds PTP1B in two mutually exclusive modes, one in which it occupies the canonical pTyr-binding site (the active site), and another in which a phosphophenyl moiety interacts with a set of residues not previously observed to bind aryl phosphates. The identification of a second pTyr molecule at the same site in the PTP1B/C215S–pTyr complex confirms that these residues constitute a low-affinity noncatalytic aryl phosphate-binding site. Identification of a second aryl phosphate binding site adjacent to the active site provides a paradigm for the design of tight-binding, highly specific PTP1B inhibitors that can span both the active site and the adjacent noncatalytic site. This design can be achieved by tethering together two small ligands that are individually targeted to the active site and the proximal noncatalytic site.     

FK-506 and cyclosporine A (CsA) immunomodulation of the human gut mucosal immune system

FK-506 and cyclosporine A (CsA) are two immunosuppressive drugs used in the treatment of patients after liver and small intestine transplantation. A clinical advantage of FK-506 over CsA has been observed in these patients. Although the immunomodulation of both drugs has been well documented in the circulatory immune system, their effect on the mucosal immune system is not well established. In this study, the effect of FK-506 on the human gut mucosal immune system was compared to CsA. Proliferation of human colonic lamina propria lymphocytes (LPL) was measured by DNA synthesis and ornithine decarboxylase (ODC) activity. Results show that FK-506 and CsA suppress LPL DNA proliferation in a dosedependent manner. FK-506 had a stronger antiproliferative effect compared to CsA. Moreover, the antiproliferative effect of both drugs was not dependent on monocytes or monocyteassociated factors (IL-1, IL-6). In addition, exogenous addition of IL-2 did not restore the suppressive effect of either drug on LPL DNA synthesis. We conclude that: (1) both drugs have an antiproliferative effect on the human mucosal immune system; and (2) the stronger effect of FK-506 on human LPL compared to CsA may explain its superior clinical response observed in patients after liver/small intestine transplantation.     

Coronary risk factor management in the framework of a community hospital-based ambulatory exercise training program

Ischemic heart disease is a chronic illness that causes major mortality and morbidity. Angiographic studies have shown the effectiveness of exercise programs, in combination with aggressive lipid management, in reversing or slowing the progression of atherosclerotic coronary disease. Despite these studies, participation in supervised programs that combine exercise and risk-factor management is limited. The authors measured the ability of a community hospital-based ambulatory cardiac rehabilitation program to recruit patients and to facilitate reduction of risk factors that have been demonstrated to influence progression of disease. Patients were recruited from a single community hospital for an ambulatory exercise training and cardiac risk-factor management program, and clinical and laboratory data was collected periodically. Recruited patients participated in a minimum 3-month period of training and counseling by a multidisciplinary team with follow-up measurements of weight, lipid profile, blood pressure, and exercise capacity. Thirty-two percent of the eligible hospitalized patients were successfully recruited into the program. Dropout rates over the initial 3 months were low (25%). Improvement in low-density lipoprotein cholesterol level (-4.5%), high-density lipoprotein cholesterol level (+7%), body mass index (-2%), systolic blood pressure (-3%), and maximum metabolic equivalents (+25%) were comparable to levels achieved in studies showing angiographic stabilization and/or regression of disease. Implementation of a community hospital-based risk management exercise program is an effective method for improving the long-term management of patients with chronic ischemic heart disease.