Peter Podgorny

Immune reconstitution after anti-thymocyte globulin-conditioned hematopoietic cell transplantation

BACKGROUND AIMS Anti-thymocyte globulin (ATG) is being used increasingly to prevent graft-versus-host disease (GvHD); however, its impact on immune reconstitution is relatively unknown. We (i) studied immune reconstitution after ATG-conditioned hematopoietic cell transplantation (HCT), (ii) determined the factors influencing the reconstitution, and (iii) compared it with non-ATG-conditioned HCT. METHODS Immune cell subset counts were determined at 1-24 months post-transplant in 125 HCT recipients who received ATG during conditioning. Subset counts were also determined in 46 non-ATG-conditioned patients (similarly treated). RESULTS (i) Reconstitution after ATG-conditioned HCT was fast for innate immune cells, intermediate for B cells and CD8 T cells, and very slow for CD4 T cells and invariant natural killer T (iNKT) (iNKT) cells. (ii) Faster reconstitution after ATG-conditioned HCT was associated with a higher number of cells of the same subset transferred with the graft in the case of memory B cells, naive CD4 T cells, naive CD8 T cells, iNKT cells and myeloid dendritic cells; lower recipient age in the case of naive CD4 T cells and naive CD8 T cells; cytomegalovirus recipient seropositivity in the case of memory/effector T cells; an absence of GvHD in the case of naive B cells; lower ATG serum levels in the case of most T-cell subsets, including iNKT cells; and higher ATG levels in the case of NK cells and B cells. (iii) Compared with non-ATG-conditioned HCT, reconstitution after ATG-conditioned HCT was slower for CD4 T cells, and faster for NK cells and B cells. CONCLUSIONS ATG worsens the reconstitution of CD4 T cells but improves the reconstitution of NK and B cells.

High rabbit-antihuman thymocyte globulin levels are associated with low likelihood of graft-vs-host disease and high likelihood of posttransplant lymphoproliferative disorder.

Rabbit-antithymocyte globulin (ATG) given with conditioning has the potential to decrease the likelihood of graft-versus-host disease (GVHD) or graft failure and to increase the likelihood of relapse or infections. After a given ATG dose, serum ATG levels are variable. Here we determined ATG levels on days 7 and 28 in 153 patients whose conditioning included 4.5 mg/kg ATG (thymoglobulin). Median follow-up was 547 days (range: 14-1519, minimum for patients who have not died, relapsed, developed second malignancy, or had graft failure, 365). Both high day 7 levels and high day 28 levels were associated with low likelihoods of grade II-IV acute GVHD and chronic GVHD needing systemic immunosuppressive therapy, and a high likelihood of posttransplant lymphoproliferative disorder (PTLD). Patients with day 7 ATG levels above 0.803 mg/L had 0.52-fold risk of developing chronic GVHD needing systemic therapy (P = 0.012) and patients with day 7 ATG levels above 1.436 mg/L had 5.84-fold risk of developing PTLD (P = 0.001) compared to patients with lower ATG levels. There was no association of ATG levels with relapse, death, or non-PTLD infections. Association with graft failure could not be evaluated due to only 4 graft failures in the cohort. In conclusion, patients with slow clearance of ATG have a low risk of GVHD, but a high risk of PTLD. The clearance of this relatively low dose of ATG does not impact the likelihood of relapse, death, or non-PTLD infections.

Immune Cell Subset Counts Associated with Graft-versus-Host Disease

Graft-versus-host disease (GVHD) is a major transplantation complication. The purpose of this study was to measure immune cell subsets by flow cytometry early after transplantation (before median day of GVHD onset) to identify subsets that may play a role in GVHD pathogenesis. We also measured the subsets later after transplantation to determine which subsets may be influenced by GVHD or its treatment. We studied 219 patients. We found that acute GVHD (aGVHD) was preceded by high counts of CD4 T cells and CD8 T cells. It was followed by low counts of total and naive B cells, total and cytolytic NK cells, and myeloid and plasmacytoid dendritic cells. Chronic GVHD (cGVHD) was preceded by low counts of memory B cells. In conclusion, both CD4 and CD8 T cells appear to play a role in the pathogenesis of aGVHD. Generation of B cells, NK cells, and dendritic cells may be hampered by aGVHD and/or its treatment. Memory B cells may inhibit the development of cGVHD.

Anti-thymocyte globulins capable of binding to T and B cells reduce graft-vs-host disease without increasing relapse

Anti-thymocyte globulin (ATG) is polyclonal, containing Ab specificities capable of binding to various immune-cell subsets implicated in the pathogenesis of GVHD, including T cells, B cells, natural killer cells, monocytes/macrophages, neutrophils and DC. We wished to determine which ATG specificities are important for GVHD prevention. We measured day 7 serum levels of 23 ATG specificities in 120 hematopoietic cell transplant recipients whose myeloablative conditioning included 4.5 mg/kg ATG (thymoglobulin). High levels of ATG specificities capable of binding to T- and B-cell subsets were associated with a low likelihood of acute GVHD (aGVHD). High levels of these ATG specificities were associated with increased rates of viral but not bacterial or fungal infections. They were not associated with an increased risk of malignancy relapse; on the contrary, high levels of ATG specificities capable of binding to regulatory T cells and invariant NKT cells were associated with a low risk of relapse. In conclusion, high levels of ATG antibodies to Ag(s) expressed on T and B cells are associated with a low risk of aGVHD and a high risk of viral but not bacterial or fungal infections. These antibodies have neutral or beneficial effects on relapse.

IL15 levels on day 7 after hematopoietic cell transplantation predict chronic GVHD.

Chronic GVHD (cGVHD) is an important complication of allogeneic hematopoietic cell transplantation (HCT). As preemptive therapy might be efficacious if administered early post transplant, we set out to determine whether cGVHD can be predicted from the serum level of a biomarker on day 7 or 28. In a discovery cohort of 153 HCT recipients conditioned with BU, fludarabine and rabbit antithymocyte globulin (ATG), we determined serum levels of B-cell-activating factor, vascular endothelial growth factor, soluble TNF-α receptor 1, soluble IL2 receptor α, IL5, IL6, IL7, IL15, γ-glutamyl transpeptidase, cholinesterase, total protein, urea and ATG. Patients with low levels of IL15 (<30.6 ng/L) on day 7 had 2.7-fold higher likelihood of developing significant cGVHD (needing systemic immunosuppressive therapy) than patients with higher IL15 levels (P<0.001). This was validated in a validation cohort of 105 similarly-treated patients; those with low IL15 levels had 3.7-fold higher likelihood of developing significant cGVHD (P=0.001). Low IL15 was not associated with relapse; it trended to be associated with acute GVHD and was associated with low infection rates. In conclusion, low IL15 levels on day 7 are predictive of cGVHD, and thus could be useful in guiding preemptive therapy.

Evidence for small fiber neuropathy in early Parkinson's disease

INTRODUCTION Parkinsons disease (PD) is neurodegenerative movement disorder affecting primarily the central nervous system with several recognized non-motor symptoms that can occur at various stages of the disease. Recently it has been shown that patients with PD may be prone to peripheral nervous system pathology in the form of a peripheral neuropathy (PN). It is unclear if PN is an inherent feature of PD or if it is an iatrogenic effect of the mainstay PD treatment Levodopa. METHODS To determine if peripheral neuropathy occurs in early untreated PD we employed a case-control study design using gold standard tests for PN, including neurological examination according to the Utah Early Neuropathy Scale (UENS) and nerve conduction studies, as well as new, more sensitive and informative tests for PN including the skin biopsy and corneal confocal microscopy (CCM). RESULTS We studied 26 patients with PD and 22 controls using the neurological examination and nerve conduction studies (NCS) and found no significant difference between groups except for some reduced vibration sense in the PD group. Epidermal nerve densities in the skin biopsies were similar between our cohorts. However, using CCM - a more sensitive test and a surrogate marker of small fiber damage in PN, we found that patients with PD had significantly reduced corneal nerve fiber densities and lengths as compared to controls. CONCLUSIONS We conclude that our positive CCM results provide evidence of preclinical PN in newly diagnosed PD patients.

High Epstein-Barr virus-specific T-cell counts are associated with near-zero likelihood of acute myeloid leukemia relapse after hematopoietic cell transplantation.

High Epstein–Barr virus-specific T-cell counts are associated with near-zero likelihood of acute myeloid leukemia relapse after hematopoietic cell transplantation

Epidermal axonal swellings in painful and painless diabetic peripheral neuropathy.

The pathophysiology of neuropathic pain (NeP) in diabetic peripheral neuropathy (DPN) is unclear. A potential pathological feature associated with intraepidermal nerve fiber density (IENFD) loss in DPN is axonal swellings.

Absence of clinical relationship between oxidized low density lipoproteins and diabetic peripheral neuropathy: a case control study

BackgroundThe pathophysiology of diabetic peripheral neuropathy (DPN) is complex and uncertain. A potential comorbidity in diabetes mellitus (DM) that may contribute to greater severity of DPN is a lipid disorder, such as with elevated cholesterol, low density lipoproteins or triglycerides. Oxidized low density lipoprotein (oxLDL) is a form of cholesterol that exerts direct toxic effects and contributes to pathogenicity through ligating a receptor called lectin-like receptor (LOX-1).MethodsWe examined plasma oxLDL levels in cohorts of patients with DPN with neuropathic pain (NeP), DPN patients without NeP, DM patients without DPN, patients with idiopathic peripheral neuropathy, and control subjects without DM or neuropathy. Our outcome measure was extent of oxLDL elevation, measured as fasting with Enzyme-Linked ImmunoSorbant Assay (ELISA) studies. Severity of diabetes was assessed using hemoglobin A1C measurements. Neuropathic severity was measured with the Utah Early Neuropathy Score (UENS). We hypothesized that DPN presence would be associated with oxLDL elevations.ResultsA total of 115 subjects (47 with DPN and NeP, 23 with DPN without NeP, 12 with diabetes only, 13 with idiopathic peripheral neuropathy, and 20 control subjects without diabetes or neuropathy) were studied. Duration of diabetes and diabetic glycemic measures were similar between populations with DM. Severity of DPN was similar between cohorts with DPN and NeP and DPN without NeP. Plasma oxLDL levels were similar between all cohorts, without any elevation in the presence of DM noted in any cohort with DM.ConclusionsoxLDL levels are not different in patients with DPN, and their lack of greater presence suggests that any pathogenic role in human DPN is likely limited.

Anti-GVHD Effect of Antithymocyte Globulin is Mediated by Antibodies Binding to T Cells and Regulatory NK Cells, and Less So or Not at All by Antibodies Binding to Other Mononuclear Cell Subsets

Introduction: Polyclonal rabbit-anti-human T cell globulin (ATG) may decrease the likelihood of graft-vs-host disease (GVHD) without increasing the likelihood of relapse. ATG is polyclonal and the anti-GVHD effect may be mediated through killing/inhibition of one or several lymphocyte subsets (eg, T cells) or their subsets (eg, na€ıve T cells). To understand the mechanism of action of ATG on GVHD, we determined levels of which ATG fraction (capable of binding to which cell subset) are associated with subsequent development of GVHD. Patients &Methods:We studied 121 patients whose myeloablative conditioning included 4.5 mg/kg ATG (Thymoglobulin). Using flow cytometry, levels of the following ATG fractions in serum from day 7 were determined: capable of binding to naive or memory B cells; naive, central memory (CM) or effector memory (EM) CD4 andCD8Tcells,EMCD8Tcells not expressingCD45RA (EMRA-); cytolytic, regulatory or CD16CD56 NK cells; monocytes and dendritic cells (DCs). ATG levels in patients with vs without aGVHD or cGVHD were compared using Mann-Whitney test. For each fractionwhere levels were significantly different (p\0.05), we determined if patients with high fraction level had a significantly lower likelihood of aGVHD or cGVHD using log-binomial regression models. Results: In univariate analyses, significantly lower levels of ATG fractions on the following subsets were found in patients developing aGVHD: binding to naive CD4 and CD8 T cells, EM CD4 T cells, and regulatoryNK cells, or cGvHD: binding to naive CD4 and CD8 T cells, CM and EM CD4 T cells, and regulatory NK cells. In multivariate analyses, high levels of the following ATG fractions were associated with a low likelihood of aGVHD: binding to naive CD4 T cells (RR 5 .33, p 5 .001), EM CD4 T cells (RR 5 .30, p\ .001), naive CD8 T cells (RR 5 .33, p 5 .002) and regulatory NK cells (RR5 .36, p5 .001) or low likelihood of cGVHD: binding to naive CD4 T cells (RR5 .59, p5 .028), CMCD4 T cells (RR5 .49, p5 .009), EMCD4T cells (RR5 .51, p5 .006), naive CD8 T cells (RR 5 .46, p 5 .005) and regulatory NK cells (RR 5 .55, p 5 .036). Conclusion: For both aGVHD and cGVHD, the anti-GVHD effect with relapse-neutral effect of ATGappears to bemediated by antibodies to antigens expressed on naive T cells (both CD4 and CD8), EM CD4 T cells and regulatory NK cells. This is the first step towards identifying the antibody(ies) within ATG important for the anti-GVHD effect without impacting relapse.