CO035 | THE ROLE OF INFLAMMATORY BIOMARKERS IN IMMUNE THROMBOTIC THROMBOCYTOPENIC PURPURA

F. Schieppati^1|2, S. Bolognini^1|2, C. Ticozzi¹, O.C. Cretu¹, P. Gomez-Rosas^1|3, M. D’Adda⁴, V. Cancelli⁴, C. Ambaglio¹, E. Galimberti¹, L. Barcella¹, A. Falanga^1|2, M. Marchetti^1|2 | ¹Immunohematology and Transfusion Medicine, Department of Transfusion Medicine and Hematology, ERN-EuroBloodNet - European Reference Network in Rare Hematological Diseases, ASST Papa Giovanni XXIII, Bergamo, Italy; ²School of Medicine and Surgery, University of Milano-Bicocca, Milano, Italy; ³Maastricht University Medical Center, Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands; ⁴Hematology, Hospital Spedali Civili di Brescia, Brescia, Italy

Background and Aims. Current iTTP treatment with therapeutic plasma exchange (TPE), immunosuppression (IS), and caplacizumab has dramatically reduced the mortality rate to <10%, although the clinical severity of each acute episode remains unpredictable. While ADAMTS13 deficiency is central to iTTP pathogenesis, growing evidence implicates systemic inflammation and NETosis as contributor mechanisms of disease development and prognosis. We aim to investigate the role of biomarkers of NETosis (citrullinated H3 histone, H3Cit) and inflammation (IL-1B, IL-2, IL-6, IL-10, and TNF-α) at iTTP onset and during treatment.
Methods. Six patients (50% female; median age: 57 years, range 20–79) newly diagnosed with acute iTTP were enrolled. Plasma samples were collected at baseline (T0) and on days 6 (T6), 9 (T9), and 15 (T15) following diagnosis. ADAMTS13 activity, anti-ADAMTS13 antibodies, and H3 Citr were assessed by ELISA, while TNF-α and interleukin levels were quantified by multiplex assay. Clinical data and treatments were recorded. Forty subjects served as controls for inflammatory biomarkers.
Results. At onset, all patients presented neurological symptoms of different severity (2 cases of ischemic stroke). Relevant comorbidities included HIV infection, myelodysplastic syndrome (MDS), and autoimmune disorders. All patients received daily TPE, IS, and caplacizumab. Hematological remission was achieved in all patients, in a median time of 3 days, except for the patient with MDS, who reached a stable platelet count >20 × 10⁹/L by day 9. Platelets’ rise correlated with LDH reduction (p=0.001). Median time to ADAMTS13 >20% was 8 days. At T0, H3Cit and TNF-α were significantly increased in iTTP patients compared to controls (p=0.004). During treatment, a significant decrease in H3Cit (p=0.0018) and TNF-α (p=0.015) plasma levels was observed over the different time points. Specifically, H3Cit levels markedly decreased from T0 (5.90 ng/mL) to T6 (1.32) (p=0.017), T9 (0.55) (p=0.009), and T15 (0.69) (p=0.016). TNF-α also significantly declined from baseline to T9 (14.83 vs 4.90 pg/mL, p=0.035). Furthermore, a significant correlation was found between the decrease of TNF-α levels and anti-ADAMTS13 antibodies (r=0.783; p<0.001). Interestingly, patients who received caplacizumab within 2 days of diagnosis (n=3) had significantly lower post-treatment TNF-α levels (4.6 vs 7.2, p=0.009) and showed a trend toward lower IL-6 levels (2.4 vs 7.3) compared to those who initiated treatment later (n=3). No correlation between inflammatory biomarkers and indicators of clinical severity (i.e., LDH level, serum troponin, and major neurological symptoms) was seen, but a positive correlation between anti-ADAMTS13 antibody titers and levels of H3Cit (p=0.028), IL-1B (p=0.023), IL-2 (p=0.013), and IL-6 (p=0.015) at baseline was observed.
Conclusions. During iTTP treatment, a significant reduction in H3Cit and TNF-α was observed in parallel with hematological response, pointing to a role of these biomarkers as indicators of NET-driven inflammation and immune activation. The positive correlation between TNF-α and anti-ADAMTS13 antibodies further supports the link between inflammation and the autoimmune process. This preliminary observation suggests that early initiation of caplacizumab may be associated with reduced inflammation. Further studies, including more severe iTTP cases, will help to clarify the role of inflammation and NETosis on disease severity and prognosis.