Prevalence of 25(OH) vitamin D (calcidiol) deficiency at time of renal transplantation: a prospective study

25(OH) Vitamin D (calcidiol) is the major circulating form of vitamin D and is considered the most reliable measure of vitamin D status. Adequate vitamin D status is important for bone health but there is increasing evidence that low serum concentrations of calcidiol (<30 ng/mL) are associated with many adverse health outcomes in the general population. Little is known about calcidiol status at the time of renal transplantation, a period when bone loss is greatest and immunosuppression is highest. We prospectively measured serum calcidiol and parathyroid hormone immediately after transplant from March 2005 onwards. Of 112 patients studied, 29% had calcidiol deficiency (<10 ng/mL), 59% had calcidiol insufficiency (10-29 ng/mL) and only 12% of patients had a normal calcidiol concentration (>30 ng/mL). The prevalence of calcidiol deficiency in black recipients was extremely high at 41%. Serum calcidiol tended to be lower in winter than other seasons. In conclusion, the prevalence of 25(OH) vitamin D (calcidiol) deficiency/insufficiency at the time of renal transplant is very high. The clinical effects of this deficiency/insufficiency deserve further study.

Renal thrombotic microangiopathy associated with interferon-alpha treatment of chronic myeloid leukemia

Recent reports have documented the development of renal thrombotic microangiopathy in patients with chronic myeloid leukemia (CML) who have undergone treatment with interferon-alpha. The pathogenesis of the renal lesion in such cases remains unclear. We report the case of a patient with chronic myeloid leukemia who developed renal failure and nephrotic syndrome while being treated with hydroxyurea and interferon-alpha. The renal biopsy showed features of chronic thrombotic microangiopathy. The patient had serologic and functional evidence of anti-phospholipid antibody. Interferon-alpha is known to cause induction of multiple autoantibodies. We propose that in the context of CML, interferon-alpha treatment can induce pathogenic anti-phospholipid antibodies that result in renal thrombotic microangiopathy. This has important implications for patients with CML receiving immune-stimulating therapy because it suggests that prospective monitoring of such patients for anti-phospholipid antibody might identify those at risk of developing thrombotic microangiopathy. Furthermore, patients with established anti-phospholipid antibody syndrome in this context might benefit from intervention such as early anticoagulation.

Intrathymic immunomodulation in sensitized rat recipients of cardiac allografts: requirements for allorecognition pathways

BACKGROUND

Intrathymic injection of alloantigen in the form of donor cells, soluble major histocompatibility complex (MHC) molecules, or MHC allopeptides induces donor-specific tolerance in a variety of acute allograft rejection models. We have previously shown that a single intrathymic injection of donor spleen cells into pre-sensitized rats abrogates accelerated (circa 24-hour) rejection and prolongs the survival of cardiac allografts to about 7 days. The present study was designed to investigate the mechanisms by which intrathymic administration of donor cells modifies the course of accelerated rejection.

METHODS

Lewis RT1(1) (LEW) rats sensitized by transplantation with Wistar-Furth RT1(u) (WF) skin grafts received WF cardiac allografts 7 days later-a classic model of accelerated rejection. At the time of skin challenge, however, certain animals received intrathymic cell suspensions (either allogeneic or syngeneic) or donor-derived class I and/or class II MHC peptides.

RESULTS

Control animals (sensitized by skin grafts but receiving no other treatment) rejected cardiac allografts within 24 hours. Intrathymic injection of WF splenocytes at the time of skin transplantation abrogated rejection at 24 hours and prolonged cardiac allograft survival to 6.6+/-0.6 days (p<0.001), whereas intrathymic administration of syngeneic (LEW) or allogeneic third party Brown Norway RT1(n) cells was ineffective in this regard. Intrathymic injection of gamma-irradiated donor cells marginally extended cardiac allograft survival to 3.0+/-0.9 days (p< 0.001), but the grafts were still rejected in an accelerated fashion. Intrathymic injection of donor-derived class I and/or class II MHC allopeptides at the same time period also failed to prolong cardiac allograft survival beyond 3 days. In the group receiving unmodified donor cells, elevated immunoglobulin M (IgM) and immunoglobulin G (IgG) allo-antibodies were found at the time of cardiac transplantation; this pattern was not observed with any other treatment.

CONCLUSION

The superiority of non-modified donor spleen cells over gamma-irradiated donor cells or donor specific allopeptides in modifying the course of accelerated cardiac rejection suggests that direct allorecognition is the dominant pathway initiating rejection in sensitized transplant recipients. Marked alterations in the antidonor IgM and IgG responses are associated with successful abrogation of accelerated rejection by thymic immunomodulatory mechanisms.

Outcome analysis of patients with vasculitis associated with antineutrophil cytoplasmic antibodies

BACKGROUND

Objective scoring systems of disease activity and disease-associated damage have proven useful in the management of patients with systemic vasculitis.

PATIENTS AND METHODS

We used the recently designed Birmingham vasculitis activity score (BVAS; maximum score 63) and vasculitis damage index (VDI; maximum score 59) to assess initial activity and long-term damage, respectively, in ANCA positive patients from one center over a 3-year period. Thirty-two patients with ANCA vasculitis were identified and analyzed as an historic cohort. The median BVAS for all vasculitis patients at first presentation was 19 (range 6 - 36). Patients with Wegener's granulomatosis had a significantly higher total score and respiratory BVAS score compared to the 15 with microscopic polyangiitis. The majority of patients received standard cyclophosphamide/steroid treatment.

RESULTS

At the end of follow-up (mean 24.9 months), 4 patients had died; all patients had evidence of permanent organ damage. The median total VDI score at last follow-up was 4.0 (range 0-11), with no differences between patients with Wegener's granulomatosis and microscopic polyangiitis. The VDI was not associated with the number of relapses. A high initial BVAS was found to correlate with a later high vasculitis damage index (r = 0.56). Initial renal or respiratory involvement was also associated with longterm damage in the same organ system.

CONCLUSION

Although mortality from ANCA-associated vasculitis has decreased, morbidity remains a common problem. High early-disease activity may identify patients at high risk of long-term organ damage, allowing more effective individualized therapy. This hypothesis requires validation in a prospective, controlled study.

In vitro and in vivo immunomodulatory effects of RDP1258, a novel synthetic peptide

Peptides derived from certain regions of human class I MHC molecules are known to have immunomodulatory effects. In particular, amino acid residues 75-84 of the HLA-B7 and HLA-B2702 molecules have demonstrated allele nonspecific immunosuppression in several animal transplant models. There is evidence that these effects are mediated by binding to intracellular heat shock proteins, including heme oxygenase-1. A new derivative of these peptides, RDP1258, was developed using a novel computer-assisted rational design technique. In vitro, RDP1258 peptide inhibited rat heme oxygenase activity in a dose-dependent manner. Similar to observations made with other in vitro heme oxygenase inhibitors, in vivo administration of RDP1258 peptide to naive rats resulted in upregulation of splenic heme oxygenase activity. The effects of the peptide on alloimmune responses were then tested. Addition of RDP1258 to rat and human mixed leukocyte reactions inhibited proliferation in a dose-dependent manner. In a rat renal transplantation model, peptide therapy combined with a sub-therapeutic dose of cyclosporin A significantly prolonged allograft survival. These data provide further evidence that modulation of the heat shock protein heme oxygenase by rationally designed peptides affects immune effector functions and may allow the development of novel immunomodulatory strategies in organ transplantation.

Nocardial infection in a renal transplant recipient on tacrolimus and mycophenolate mofetil

Infection with Nocardia spp. is an uncommon but important cause of morbidity and mortality in organ transplant recipients. Cotrimoxazole prophylaxis against urinary tract infection and Pneumocystis carinii pneumonia in these patients usually prevents nocardial infection also. We report the case of a patient on tacrolimus and mycophenolate mofetil who developed drug-induced diabetes mellitus followed by nocardial brain infection. This infection occurred despite conventional cotrimoxazole prophylaxis. Physicians should be aware that newer, more potent and more diabetogenic immunosuppressive regimens may increase the risk of opportunistic infections such as nocardiosis, even in the presence of "adequate" antimicrobial preventive measures.

Immunosuppressive agents in organ transplantation

This article reviews current and future immunosuppressive strategies in organ transplantation. Recently introduced drugs are lowering the rates of acute rejection and allowing more individualized management of transplanted patients.

Inhibition of allorecognition by a human class II MHC-derived peptide through the induction of apoptosis

The interaction of the T-cell receptor with the major histocomatibility complex (MHC)-peptide complex is central to T-cell activation. Variation in the nature of the peptide bound within the groove of the MHC molecule may result in an altered T-cell response. Because some naturally processed peptides bound within the groove of the class II MHC molecule are derived from the MHC molecules themselves, we studied the inhibitory effects of synthetic class II MHC peptides on alloimmune responses in vitro. Three peptides derived from a highly conserved region of the class II MHC alpha chains inhibited the rat mixed lymphocyte response (MLR) in a dose-dependent manner, with the human HLA-DQA1 peptide also inhibiting the human and mouse MLR. No effect was seen on mitogen-induced T-cell proliferation. HLA-DQA1 inhibited cytolytic T lymphocyte (CTL) generation in a dose-response fashion, with no reduction in preformed CTL killing, suggesting that the inhibitory effect is targeted at CD4(+) T-cell function. Cell-cycle analysis by flow cytometry showed that restimulation of primed T cells in the presence of HLA-DQA1 resulted in increased apoptosis, whereas unstimulated cells were not affected. These data demonstrate that synthetic peptides derived from highly conserved regions of the class II MHC alpha chain can alter CD4(+) T-lymphocyte alloimmune responses in vitro, and this effect is mediated by the induction of apoptosis in activated T cells.

Comparative studies of specific acquired systemic tolerance induced by intrathymic inoculation of a single synthetic Wistar-Furth (RT1U) allo-MHC class I (RT1.AU) peptide or WAG (RT1U)-derived class I peptide

BACKGROUND

Because T cell receptor-MHC class I/self-peptide interactions regulate T-cell development, the presence of MHC allopeptides in the thymus may influence T-cell tolerance to alloantigens. This hypothesis is supported by our most recent finding that intrathymic (IT) inoculation of nonimmunogenic synthetic peptides derived from "WAG" RT1.A induces tolerance to cardiac allografts in the Wistar-Furth (WF)-to-ACI model. To evaluate whether in vivo immunogenicity of MHC peptides is relevant to tolerance induction and to examine the effect of peptide specificity, we compared the effects on graft survival of well-defined, strain-specific immunogenic WF MHC class I peptides (RT1.AU) with closely related but non-strain-specific class I peptides derived from WAG (RT1U).

METHODS

In vivo immunization of seven MHC class I peptides synthesized from RT1.AU sequences showed that two (u-5 and u-7) were immunogenic, whereas five others were not immunogenic in ACI recipients. We then examined the effects on cardiac allograft survival in the WF-to-ACI model of the two immunogenic RT1.AU peptides (u-5 and u-7) and three immunogenic WAG-derived peptides (peptides 1, 2, and 5).

RESULTS

A combination of equal amounts (150 microg or 300 microg) of u-5 or u-7 each with 0.5 ml of antilymphocyte serum (ALS) on day -7 led to 60% and 100% permanent graft survival (>150 days), respectively. IT injection of the individual peptides on day -7 showed that only 300 microg of u-5 significantly prolonged graft survival to a median survival time of 17.3 days from 10.5 days in naive recipients. IT injection of 150, 300, and 600 microg of u-5 combined with 0.5 ml of ALS on day -7 led to permanent graft survival (> 150 days) in four of six, nine of nine, and six of six ACI recipients, respectively, compared with a median survival time of 15.4 days in ALS alone-treated controls. In contrast, similar treatments with peptide u-7 with or without 0.5 ml of ALS did not prolong graft survival, thus demonstrating that peptide u-5 alone mediates the observed effects on graft prolongation. A total of 300 microg of u-5 injected IT combined with ALS led to acute rejection of third-party (Lewis) grafts. Intravenous injection of 300 microg of u-5 with ALS also did not prolong WF graft survival in ACI recipients. The long-term unresponsive ACI recipients accepted permanently donor-type (WF) but not third-party (Lewis) second-set cardiac and islet allografts. Similarly, we showed that although IT injection of 600 and 1200 microg of a mixture of immunogenic WAG-derived peptides 1, 2, and 5 combined with 0.5 ml of ALS on day -7 led to permanent WF graft survival in ACI, only IT injection of 300 microg of peptide 2 combined with ALS led to permanent graft survival (>150 days) in four of five animals. To define the underlying mechanisms of tolerance, we examined in vitro the mixed lymphocyte reaction (MLR), cell-mediated lymphocytotoxicity, and cytokine profile of unresponsive recipients. Although the results showed nonspecific T-cell suppression in the MLR at 25 days after transplantation, which correlated with the persistence of ALS immunosuppression, long-term unresponsive animals showed normal MLR to donor and third-party antigens. In contrast, the donor-specific reactive cytotoxic T lymphocytes remained suppressed in short-term and long-term unresponsive rats.

CONCLUSION

Of interest is our finding that IT injection of a short segment of WAG-derived MHC class I peptide induces active acquired tolerance similar to results obtained with the use of pure WF-derived peptide u-5 in the WF-to-ACI rat combination. It is noteworthy that we could not confirm the T helper (Th)1/Th2 paradigm in this model by initial cytokine analysis. Whether induction of tolerance by IT injection of allo-MHC peptides will have clinical usefulness must await results of similar studies in large animals. However, of major interest is the finding that a short segment of RT1.AU represents the tolerogenic

Peptide-mediated immunosuppression

New insights into the mechanisms of allorecognition and the interactions of the TCR with the MHC molecule-peptide complex on antigen presenting cells have focused attention on developing novel biological strategies to modify the alloimmune response. Peptides derived from various regions of MHC class I and II molecules and structure-based peptides have demonstrated immunomodulatory effects both in vitro and in vivo. Their binding sites and mechanisms of action are under active investigation. Trials in human transplant recipients, with an MHC class I peptide have already begun.