A group in Italy has been searching for a way to screen children for asthma, and get a reliable indicator of the level of inflammation in the airway. Initially the group looked into measurements of the temperature of exhaled breath to provide a marker of airway remodeling (1). The increase in the exhaled breath temperature (EBT) has been hypothesized to result from increased vascularity of the airway wall (1). Other studies have noted the correlation between inflammation and temperature and given mechanistic hypothesis (4). Previous studies also showed preliminary results that linked metalloprotineinase-9 (MMP-9) to the remodeling process. The preliminary data showed a correlation when children were exposed to allergens between the exhaled temperature and MMP-9, measured through enzyme-linked immunoabsorbant assays on sputum.
The same group abandoned the tempurature measurement to persue measurements of exhaled nitric oxide (eNO) and fractional exhaled nitric oxide (FENO). The measurements of FENO have been shown to correlate with eosinophilic inflammation in asthma patients. The studies indicated that allergen avoidance modifies inflammatory parameters and that the initial extracellular bioelectrical conductivity measurements provided a reliable non-invasive method to assess airway inflammation (2). The method was also tested for correlation against the Childhood Asthma Control Test (C-ACT), when used together produce a reliable diagnostic and predicting tool (3).
(1) Piacentini, G.L. , et. Al. Exhaled breath temperature as a marker of airway remodeling in asthma, a preliminary study, Allergy 2008:63; 484-485
(2) Peroni, D.G., et. Al . Bioimpedance monitoring of airway inflammation in asthmatic allergic children. Allergologia et Immunopathologia 2008
(3) Piacentini, G.L. , et. Al. Childhood Asthma Control Test and airway inflammation evaluation in asthmatic children. Allergy 2009
(4) Piacentini, G.L. , et. Al. Exhaled air temperature in asthma: methods and relationship with markers of disease. Clin Exp Allergy, 2007; Mar;37(3): 415-419
24 December 2009
23 December 2009
operational tolerance post liver transplants
One of the interesting groups of patients that I have come across in the last 1 1/2 years are the patients who receive liver transplant and over time develop "operational tolerance" of their graft, meaning that they are able to wean off immunosuppressive agents over time. Operational tolerance is defined clinically as the "lack of acute or chronic rejectionn and graft survival with normal function and histology in an immunosuppressant-free, immunocompetent host."
Anectodally, we see this most commonly with teenagers who have become non-compliant with their immunosuppressive regiments. And of the solid organ transplants, liver transplants are most likely to become tolerated by the host's immune system. In general, children are more likely than adults to develop operational tolerance. In the literature, 3-20% of patients may be able to wean successfully off of immunosuppressants.
This brings the questions--why do some patients reject the graft and others become tolerant? How can we predict which patients will develop operational tolerance?
A study in Brussels observed that pediatric patients who developed operational tolerance had higher levels of IL-10 and decreased TNF-alpha and IFN-gamma levels soon after transplant (2 hours, 1 day and 4 days). This could potentially identify a cytokine profile that could possibly predict patients who would become tolerant. Other studies have suggested that there is an elevated number of T regs in patients who develop tolerance (this would correlate with higher amounts of IL-10, which is produced by T regs as we are aware).
T regs express CD4/CD25 and the transcription factor FoxP3. There are studies that suggest that FoxP3 can also be induced by peripheral T cells that are CD4+/CD25-.
This study (Pons et al) set out to monitor T cells in patients s/p liver transplant as immune suppression was weaned. They selected 12 adults who had: received a liver 2+ years prior to the start of the study, were 1+ years past a rejection episode, and had no evidence of autoimmune liver disease or viral infections. They were monitored prospectively as their immunosuppression (cyclosporine and prednisone) was gradually weaned. Flow cytometry was used to identify lymphocytes, and FoxP3 mRNA levels were detected by PCR. The researchers looked at populations of T lymphocytes (CD3+CD4+, CD3+CD8+, CD3+Vdelta+), B lymphocytes (CD19+), and NK cells (CD3_CD16+CD56+) prior to withdrawal of immunosuppression and then at various periods during withdrawal of immunosuppression. They compared these findings to another group s/p liver transplant who were immunosuppressant-dependant (ID) and another group who was healthy (H). There was a similar profile of T regs (CD4+CD25+) in all immunosuppressed patients.
Over the course of withdrawal of immunosuppression, 5/12 patients developed tolerance. The percentage of CD3+, CD4+, CD8+, CD19+, CD3-CD16+CD56+, CD8+CD28- populations did not change during withdrawal (in the patients who ended up becoming tolerant and those who ended up rejecting). However, in the group that became tolerant of their graft, T regs increased significantly during the withdrawal (beginning at the time of assessment pre-withdrawal and ending at the tolerance point). The group who rejected did not exhibit this increase in T regs. They noticed a similar pattern with FoxP3 mRNA expression.
This study was unable to predict (prior to immunosuppression withdrawal) which patients will become tolerant. However, they were able to determine that T regs and FoxP3 expression dramatically changes in patients who become tolerant.
Continued research in this area will greatly influence care of patients post transplant. In the past, it has been gold standard to continue immunosuppression, tolerating the side effect profiles of the medications. Identifying patients who will successful become tolerant will help to titrate medications, improve quality of life, and decrease harmful side effects of the immunosuppression medications.
Pons JA et al, FoxP3 in peripheral blood is associated with operational tolerance in liver transplant patients during immunosuppression withdrawal. Transplantation. 2008 Nov 27;86(10):1370-8.
Orlando G et al, Operational Tolerance after Liver Transplantation. J Hepatology 2009;50:1247-57.
Anectodally, we see this most commonly with teenagers who have become non-compliant with their immunosuppressive regiments. And of the solid organ transplants, liver transplants are most likely to become tolerated by the host's immune system. In general, children are more likely than adults to develop operational tolerance. In the literature, 3-20% of patients may be able to wean successfully off of immunosuppressants.
This brings the questions--why do some patients reject the graft and others become tolerant? How can we predict which patients will develop operational tolerance?
A study in Brussels observed that pediatric patients who developed operational tolerance had higher levels of IL-10 and decreased TNF-alpha and IFN-gamma levels soon after transplant (2 hours, 1 day and 4 days). This could potentially identify a cytokine profile that could possibly predict patients who would become tolerant. Other studies have suggested that there is an elevated number of T regs in patients who develop tolerance (this would correlate with higher amounts of IL-10, which is produced by T regs as we are aware).
T regs express CD4/CD25 and the transcription factor FoxP3. There are studies that suggest that FoxP3 can also be induced by peripheral T cells that are CD4+/CD25-.
This study (Pons et al) set out to monitor T cells in patients s/p liver transplant as immune suppression was weaned. They selected 12 adults who had: received a liver 2+ years prior to the start of the study, were 1+ years past a rejection episode, and had no evidence of autoimmune liver disease or viral infections. They were monitored prospectively as their immunosuppression (cyclosporine and prednisone) was gradually weaned. Flow cytometry was used to identify lymphocytes, and FoxP3 mRNA levels were detected by PCR. The researchers looked at populations of T lymphocytes (CD3+CD4+, CD3+CD8+, CD3+Vdelta+), B lymphocytes (CD19+), and NK cells (CD3_CD16+CD56+) prior to withdrawal of immunosuppression and then at various periods during withdrawal of immunosuppression. They compared these findings to another group s/p liver transplant who were immunosuppressant-dependant (ID) and another group who was healthy (H). There was a similar profile of T regs (CD4+CD25+) in all immunosuppressed patients.
Over the course of withdrawal of immunosuppression, 5/12 patients developed tolerance. The percentage of CD3+, CD4+, CD8+, CD19+, CD3-CD16+CD56+, CD8+CD28- populations did not change during withdrawal (in the patients who ended up becoming tolerant and those who ended up rejecting). However, in the group that became tolerant of their graft, T regs increased significantly during the withdrawal (beginning at the time of assessment pre-withdrawal and ending at the tolerance point). The group who rejected did not exhibit this increase in T regs. They noticed a similar pattern with FoxP3 mRNA expression.
This study was unable to predict (prior to immunosuppression withdrawal) which patients will become tolerant. However, they were able to determine that T regs and FoxP3 expression dramatically changes in patients who become tolerant.
Continued research in this area will greatly influence care of patients post transplant. In the past, it has been gold standard to continue immunosuppression, tolerating the side effect profiles of the medications. Identifying patients who will successful become tolerant will help to titrate medications, improve quality of life, and decrease harmful side effects of the immunosuppression medications.
Pons JA et al, FoxP3 in peripheral blood is associated with operational tolerance in liver transplant patients during immunosuppression withdrawal. Transplantation. 2008 Nov 27;86(10):1370-8.
Orlando G et al, Operational Tolerance after Liver Transplantation. J Hepatology 2009;50:1247-57.
22 December 2009
Allogeneic Hematopoetic Stem Cell Transplantation for Sickle Cell Disease
Background
Myeloablative allogeneic hematopoietic stem-cell transplantation is curative in children with sickle cell disease, but in adults the procedure is unduly toxic. Graft rejection and graft-versus-host disease (GVHD) are additional barriers to its success. We performed nonmyeloablative stem-cell transplantation in adults with sickle cell disease.
Methods
Ten adults (age range, 16 to 45 years) with severe sickle cell disease underwent nonmyeloablative transplantation with CD34+ peripheral-blood stem cells, mobilized by granulocyte colony-stimulating factor (G-CSF), which were obtained from HLA matched siblings. The patients received 300 cGy of total-body irradiation plus alemtuzumab before transplantation, and sirolimus was administered afterward.
Results
All 10 patients were alive at a median follow-up of 30 months after transplantation (range, 15 to 54). Nine patients had long-term, stable donor lymphohematopoietic engraftment at levels that sufficed to reverse the sickle cell disease phenotype. Mean ± SE) donor–recipient chimerism for T cells (CD3+) and myeloid cells (CD14+15+) was 53.3 ± 8.6% and 83.3 ± 10.3%, respectively, in the nine patients whose grafts were successful. Hemoglobin values before transplantation and at the last follow-up assessment were 9.0± 0.3 and 12.6 ± 0.5 g per deciliter, respectively. Serious adverse events included the narcotic-withdrawal syndrome and sirolimus-associated pneumonitis and arthralgia. Neither acute nor chronic GVHD developed in any patient.
Conclusions
A protocol for nonmyeloablative allogeneic hematopoietic stem-cell transplantation that includes total-body irradiation and treatment with alemtuzumab and sirolimus can achieve stable, mixed donor–recipient chimerism and reverse the sickle cell phenotype. (ClinicalTrials.gov number, NCT00061568.)
As the authors note in their abstract, the myeloablative transplantation of allogeneic stem cells has been extremely successful (90-95%) in curing children with sickle cell disease. However, the myeloablation process has shown unacceptable toxicity in human adult patients, preventing clinicians from successfully treating these patients. The authors thus tested a nonmyeloablative procedure on a murine model to determine safety and efficacy, then progressed to this study on 10 adult human patients. Instead of attempting to block T cell activation as in normal myeloablative procedures, the drug combination used by this team inhibits T cell proliferation. The inhibition of T cell proliferation causes anergy in the host’s Tcells, limiting their reactivity to antigens, promoting T cell tolerance to the new graft tissue. With this treatment, the authors were successful at reversing the sickle cell disease phonotype in 9 out of 10 patients, and managed to prevent GVHD in all patients. This is promising research into being able to reverse the disease state in adults.
1. Hsieh, M. M.; Kang, E. M.; Fitzhugh, C. D.; Link, M. B.; Bolan, C. D.; Kurlander, R.; Childs, R. W.; Rodgers, G. P.; Powell, J. D.; Tisdale, J. F., Allogeneic Hematopoietic Stem-Cell Transplantation for Sickle Cell Disease. N Engl J Med 2009, 361 (24), 2309-2317.
Myeloablative allogeneic hematopoietic stem-cell transplantation is curative in children with sickle cell disease, but in adults the procedure is unduly toxic. Graft rejection and graft-versus-host disease (GVHD) are additional barriers to its success. We performed nonmyeloablative stem-cell transplantation in adults with sickle cell disease.
Methods
Ten adults (age range, 16 to 45 years) with severe sickle cell disease underwent nonmyeloablative transplantation with CD34+ peripheral-blood stem cells, mobilized by granulocyte colony-stimulating factor (G-CSF), which were obtained from HLA matched siblings. The patients received 300 cGy of total-body irradiation plus alemtuzumab before transplantation, and sirolimus was administered afterward.
Results
All 10 patients were alive at a median follow-up of 30 months after transplantation (range, 15 to 54). Nine patients had long-term, stable donor lymphohematopoietic engraftment at levels that sufficed to reverse the sickle cell disease phenotype. Mean ± SE) donor–recipient chimerism for T cells (CD3+) and myeloid cells (CD14+15+) was 53.3 ± 8.6% and 83.3 ± 10.3%, respectively, in the nine patients whose grafts were successful. Hemoglobin values before transplantation and at the last follow-up assessment were 9.0± 0.3 and 12.6 ± 0.5 g per deciliter, respectively. Serious adverse events included the narcotic-withdrawal syndrome and sirolimus-associated pneumonitis and arthralgia. Neither acute nor chronic GVHD developed in any patient.
Conclusions
A protocol for nonmyeloablative allogeneic hematopoietic stem-cell transplantation that includes total-body irradiation and treatment with alemtuzumab and sirolimus can achieve stable, mixed donor–recipient chimerism and reverse the sickle cell phenotype. (ClinicalTrials.gov number, NCT00061568.)
As the authors note in their abstract, the myeloablative transplantation of allogeneic stem cells has been extremely successful (90-95%) in curing children with sickle cell disease. However, the myeloablation process has shown unacceptable toxicity in human adult patients, preventing clinicians from successfully treating these patients. The authors thus tested a nonmyeloablative procedure on a murine model to determine safety and efficacy, then progressed to this study on 10 adult human patients. Instead of attempting to block T cell activation as in normal myeloablative procedures, the drug combination used by this team inhibits T cell proliferation. The inhibition of T cell proliferation causes anergy in the host’s Tcells, limiting their reactivity to antigens, promoting T cell tolerance to the new graft tissue. With this treatment, the authors were successful at reversing the sickle cell disease phonotype in 9 out of 10 patients, and managed to prevent GVHD in all patients. This is promising research into being able to reverse the disease state in adults.
1. Hsieh, M. M.; Kang, E. M.; Fitzhugh, C. D.; Link, M. B.; Bolan, C. D.; Kurlander, R.; Childs, R. W.; Rodgers, G. P.; Powell, J. D.; Tisdale, J. F., Allogeneic Hematopoietic Stem-Cell Transplantation for Sickle Cell Disease. N Engl J Med 2009, 361 (24), 2309-2317.
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