Presenting ADAMTS13 antibody and antigen levels predict prognosis in immune-mediated thrombotic thrombocytopenic purpura.

Immune-mediated thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder caused by antibodies against ADAMTS13. From the United Kingdom TTP registry, we undertook a prospective study investigating the impact of the presenting anti-ADAMTS13 IgG antibody and ADAMTS13 antigen on mortality. A total of 312 episodes involving 292 patients over 87 months were included; 68% were female, median age 46 (range, 11-88 years), and median presenting ADAMTS13 of <5% (range, <5%-18%). The mortality rate was 10.3% (n = 32); 68% of patients had a raised troponin at presentation conferring a sixfold increase in mortality compared with those with normal troponin levels (12.1% vs 2.0%, P = .04). Twenty-four percent had a reduced Glasgow Coma Score (GCS) at presentation with a ninefold increase in mortality (20% vs 2.2% for normal GCS at presentation, P < .0001). Mortality increased with higher anti-ADAMTS13 antibody levels and lower ADAMTS13 antigen levels. Those with antibody levels in the upper quartile (antibody >77%) had a mortality of 16.9% compared with 5.0% for the lowest quartile (antibody <20%) (P = .004). Those with an antigen level in the lowest quartile (antigen <1.5%) had a mortality of 18% compared with 3.8% for the highest quartile (antigen >11%) (P = .005). The synergistic effect of anti-ADAMTS13 IgG antibody in the upper quartile and ADAMTS13 antigen in the lowest quartile had the highest mortality of 27.3%. We conclude that both anti-ADAMTS13 IgG antibody and ADAMTS13 antigen levels correlate with outcome in TTP with increased cardiac and neurological involvement and increased mortality.

Rituximab prophylaxis to prevent thrombotic thrombocytopenic purpura relapse: outcome and evaluation of dosing regimens.

Acute antibody-mediated thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy with high morbidity and mortality. Rituximab is highly effective as prophylaxis in patients at risk of acute TTP relapse, but the ideal dosing regimen is unknown. A multicenter retrospective cohort study evaluated outcomes of patients given rituximab prophylaxis to prevent TTP relapse. Rituximab was given in 76 episodes to 45 patients (34 women and 11 men). Four once-per-week infusions of standard- (375 mg/m2 [24 episodes]), reduced- (200 mg [19 episodes]), and intermediate- (500 mg [17 episodes]) dose rituximab were given; in the remaining 16 episodes, patients received 100 to 1000 mg rituximab in 1 to 5 doses. Patients were deemed at high risk of TTP relapse on the basis of ADAMTS13 activity dropping to ≤15% from the normal range. Preprophylaxis median ADAMTS13 level was 5% (range, <5% to 17%). Normalization of ADAMTS13 occurred in 78.9% of patients, with 92.1% having at least a partial response (ADAMTS13 ≥30%); 3 patients had no response. Over a median of 15 months (range, 1-141 months), there were only 3 TTP relapses (2 of these subacute) in the reduced dose group. Re-treatment with rituximab occurred in 50% of patient episodes at a median of 17.5 months (range, 9-112 months) after initial prophylaxis. There was a statistically higher rate of re-treatment in the reduced- vs standard-dose group: 0.38 vs 0.17 episodes per year, respectively. Treatment was generally well tolerated, infusional effects being the most commonly reported. Rituximab therapy is effective as prophylaxis for normalizing ADAMTS13 and is an additional measure for preventing acute TTP relapses in patients with immune TTP.

The utility of ADAMTS13 in differentiating TTP from other acute thrombotic microangiopathies: results from the UK TTP Registry.

Thrombotic microangiopathies (TMAs) are frequently difficult to differentiate clinically, and measurement of ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) remains vital in thrombotic thrombocytopenic purpura (TTP) diagnosis. We retrospectively reviewed cases referred for ADAMTS13 testing, using UK TTP Registry screening data. Of a total 810 cases, 350 were confirmed as TTP. The 460 non-TTP cases comprised secondary TMAs (24·57%) and haemolytic uraemic syndrome (HUS) (27·17% aHUS, 2·83% Shiga-like toxin-producing E. coli [STEC]-HUS); the remainder were TMAs with no clear association, not TMAs, or had no confirmed diagnosis. ADAMTS13 levels were significantly lower in TTP than STEC-HUS, aHUS and other TMAs. TTP patients had significantly lower platelet count (15 × 10(9) /l; range 0-96) than aHUS (57 × 10(9) /l; range 13-145, P < 0·0001) or STEC-HUS (35 × 10(9) /l; range 14-106, P < 0·0001); they also had lower creatinine levels (92 µmol/l; range 43-374) than aHUS (255 µmol/l; range 23-941, P < 0·0001) and STEC-HUS (324 µmol/l; range 117-639, P < 0·0001). However, 12/34 (35·3%) aHUS patients had a platelet count <30 × 10(9) /l and 26/150 (17·3%) of TTP patients had a platelet count >30 × 10(9) /l; 23/150 (15·3%) of TTP patients had a creatinine level >150 µmol/l. This study highlights the wide variety of TMA presentations, and confirms the utility of ADAMTS13 testing in TTP diagnosis.

An innovative method to generate a Good Manufacturing Practice-ready regulatory T-cell product from non-mobilized leukapheresis donors.

BACKGROUND AIMS: There is real and sustained interest in preparing T-regulatory cells from leukapheresis collections for cellular therapy through the use of simple, effective and reliable methods conforming to Good Manufacturing Practice (GMP). We describe a GMP-ready isolation procedure for CD25(+) products with the use of a sterile docking device, pigtail sampling, a laminar flow hood and the CliniMACS system that uses leukapheresis collections made by two apheresis machines. METHODS: We used CD8/CD19 depletion followed by CD25-positive selection. The median number of CD4(+) cells recovered was 72.5 ± 32.6 × 10(6), of which 60.5% ± 17.8% were CD25(+)FOXP3(+) cells. Suppression of autologous CD25(-) cell proliferation by the cryopreserved CD25(+) products was 51.3% ± 4.4%, 49.0% ± 3.7% and 39.0% ± 3.6% at CD25(+):CD25(-) ratios of 1:1, 1:2 and 1:4 (n = 6), respectively, comparable to suppression by fresh CD25(+) products (53% ± 6.2%, 51% ± 3.3% and 39% ± 7.1%). RESULTS: We found Leukapheresis collections by Cobe Spectra contained more lymphocytes and platelets than collections by Spectra Optia apheresis machine (median, 9.2 × 10(9) versus 6.7 × 10(9); P = 0.04) and platelets (median, 610 × 10(9) versus 170 × 10(9); P = 0.04). The frequency of CD4(+)CD25(+)FOXP3(+) was significantly higher in the leukapheresis (4.85%; 95% confidence interval, 1.95% to 5.38%) than in peripheral blood (3.9%; 95% confidence interval, 2.63% to 6.45%) (P = 0.02). The CD8- and CD19-negative depletion step was associated with significant loss of total CD4(+) T cells (P = 0.001). CONCLUSIONS: Results suggest that functional CD25(+) products can be isolated with a GMP-ready method, and good recovery can be obtained with the use of an optimized cryopreservation protocol. These data and methods show the potential, possibilities and future work needed to isolate target cell populations in a reproducible, time-efficient and cost-efficient manner for clinical applications.

Human immunodeficiency virus associated thrombotic thrombocytopenic purpura--favourable outcome with plasma exchange and prompt initiation of highly active antiretroviral therapy.

Thrombotic thrombocytopenic purpura (TTP) is an acute prothrombotic disorder. Human immunodeficiency virus (HIV) is an identified precipitant. This study reviewed 30 episodes of HIV-associated TTP in 24 patients from the South-East England Apheresis units, over the last 10 years. All patients were heterosexual Black Africans. First presentation of TTP revealed a new diagnosis of HIV in eight patients. TTP relapse occurred on six occasions (in four patients) as a result of non-adherence to highly active antiretroviral therapy (HAART). Prompt initiation/re-initiation of HAART in parallel with plasma exchange (PEX)±steroid led to prompt remission. Adjunct immunomodulatory agents (e.g. Rituximab) were required in 10% of cases. Once-daily HAART regimens are recommended, being compatible with PEX requirement, maximizing drug exposure between PEX. High viral loads (>500,000 copies/ml) require more PEX to remission. ADAMTS13 activity was reduced (<5%) as detected by collagen-binding assay and anti-ADAMTS13 immunoglobulin G antibodies were raised in 80%. Continued HAART-adherence ensured a durable TTP remission with associated viral control resulting in no evidence of relapse. PEX and HAART are associated with replenishment of ADAMTS13 and viral suppression. More PEX is required in cases with higher viral loads. Continued HAART maintains remission. In a small proportion of cases, further immunomodulatory therapy may be required.

Regional UK TTP registry: correlation with laboratory ADAMTS 13 analysis and clinical features.

Thrombotic thrombocytopenic purpura (TTP) is an acute, rare, life-threatening disorder. This report presents the South East (SE) England registry for TTP, from April 2002 to December 2006, which included 176 patients and 236 acute episodes; 75% of patients were female and 25% were male, overall median age at presentation was 42 years. Mortality was 8.5%, most cases died before treatment was instigated. The main ethnic groups were Caucasian (64%) and Afro Caribbean (27%). Seventy-seven percent of cases were idiopathic, 5% were congenital and the remaining cases had a defined precipitant. Neurological features were the most prevalent, but cardiac involvement accounted for 42% of presenting features. The overall median number of plasma exchanges (PEXs) to remission was 15; between April 2002 and December 2003, the median number of PEXs was 19 and it was 12 between January 2004 and December 2006 (P < 0.0001). In the latter period, adjuvant therapies were reduced, but Rituximab was increased. ADAMTS 13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity was <10% in 74% and 95% of these cases had positive IgG antibodies to ADAMTS 13. Renal impairment and delayed normalisation of platelet count were the main differences between idiopathic and secondary TTP.

Remission in acute refractory and relapsing thrombotic thrombocytopenic purpura following rituximab is associated with a reduction in IgG antibodies to ADAMTS-13.

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder and plasma exchange (PEX) remains the primary treatment modality. Twenty-five patients with acute refractory/relapsing idiopathic TTP received rituximab in conjunction with PEX because of progressive clinical disease or deterioration in laboratory parameters, despite intensive standard therapy. In relapsing TTP, rituximab was started if antibody to ADAMTS-13 (a disintegrin and metalloproteinase with thrombospondin motif-13) was demonstrated during previous episodes. All 25 patients attained complete clinical and laboratory remission in a median of 11 d after initiating rituximab. In 21 cases, ADAMTS-13 activity was within the normal range following rituximab. Inhibitors were detected in 24/25 patients by mixing studies and/or immunoglobulin G (IgG) antibodies to ADAMTS-13 pre-rituximab. There was no evidence of inhibitors and/or IgG activity <10% in 23/25 patients following rituximab. In acute refractory cases, the median number of PEX pre-rituximab and following the first rituximab infusion was 13 and 9, respectively. There have been no infectious complications, despite low CD 19 levels and no relapses. In patients with acute refractory/relapsing idiopathic TTP, rituximab appears to be a safe, effective, targeted therapy with a significant reduction in the requirement for PEX.

Venous thromboembolism associated with the management of acute thrombotic thrombocytopenic purpura.

Venous thromboembolism (VTE) is not a feature of thrombotic thrombocytopenic purpura (TTP), but there has been a recent report of VTE in association with plasma exchange (PEX) treatment for TTP using the solvent detergent (SD) plasma, PLAS+SD. We reviewed the occurrence of VTE in 68 consecutive patients with TTP (25 men, 43 women). Eight documented VTE events [six deep venous thromboses (DVTs), three pulmonary emboli] were identified in seven patients (all female) during PEX therapy. All six DVTs were associated with central lines at the site of thrombosis. Other known precipitating factors included pregnancy, immobility, obesity and factor V Leiden heterozygosity. VTE occurred at a mean of 53 d following the first PEX. The European SD plasma, Octaplas was the last plasma to be used in PEX prior to the VTE in 7/8 events. This is the first report of VTE following Octaplas infusion. VTE is a multifactorial disease and, although several known precipitating factors were present in all patients in this study, the use of large volumes of SD plasma in PEX may be an additional risk factor. We recommend prevention of VTE with graduated elastic compression stockings (class I) at diagnosis and prophylactic low-molecular-weight heparin once the platelet count rises above 50 x 10(9)/l.