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Objectives To apply therapeutic drug monitoring and dose-individualization of intravenous Busulfan to paediatric patients and evaluate the impact of syringe-pump induced Busulfan infusion lag-time after in vitro estimation. Methods 76 children and adolescents were administered 2 h intravenous Busulfan infusion every 6 h (16 doses). Busulfan plasma levels, withdrawn by an optimized sampling scheme and measured by a validated HPLC–PDA method, were used to estimate basic PK parameters, AUC, Cmax, kel, t1/2, applying Non-Compartmental Analysis. In vivo infusion lag-time was simulated in vitro and used to evaluate its impact on AUC estimation. Key findings Mean (%CV) Busulfan AUC, Cmax, clearance and t1/2 for pediatric population were found 962.3 μm × min (33.1), 0.95 mg/L (41.4), 0.27 L/h/kg (33.3), 2.2 h (27.8), respectively. TDM applied to 76 children revealed 6 (7.9%) being above and 25 (32.9%) below therapeutic-range (AUC: 900–1350 μm × min). After dose correction, all patients were measured below toxic levels (AUC < 1500 μm × min), no patient below 900 μm × min. Incorporation of infusion lag-time revealed lower AUCs with 17.1% more patients and 23.1% more younger patients, with body weight Conclusions TDM, applied successfully to 76 children, confirmed the need for Busulfan dose-individualization in paediatric patients. Infusion lag-time was proved clinically significant for younger, low body-weight patients and those close to the lower therapeutic-range limit.

In this study, we aimed to illustrate the trajectory of humoral and cellular immunity nine months after primary vaccination with the BNT162b2 mRNA vaccine among 189 healthcare workers (HCWs). Additionally, we endeavored to identify correlations between immunity parameters and a number of common variables and comorbidities. A total of 189 healthcare workers (HCWs), vaccinated against COVID-19, were finally included in the study. All of the subjects had received two doses of the BNT162b2 vaccine; had undergone antibody tests one, four and nine months post-vaccination; and had completed a medical questionnaire. Further samples taken at nine months were tested for cellular immunity. No participants had evidence of COVID-19 infection pre- or post-vaccination. An anti-S1 receptor binding domain (RBD) antibody assay was used to assess humoral response, and cellular immunity was estimated with an INF-γ release assay (IGRA). Statistical analysis was performed using STATA. We report a statistically significant antibody drop over time. Being above the age of 40 or a smoker reduces the rise of antibodies by 37% and 28%, respectively. More than half of the participants did not demonstrate T-cell activation at nine months. Female gender and antibody levels at four months predispose detection of cellular immunity at nine months post-immunization. This study furthers the qualitative, quantitative, and temporal understanding of the immune response to the BNT162b2 mRNA vaccine and the effect of correlated factors.

INTRODUCTION: HCV infection in patients under hemodialysis for end stage chronic kidney disease (ESCKD) may exist despite the absence of anti-HCV antibodies. Molecular methods are widely accepted as “gold standard” techniques for the detection of viral RNA. However, the molecular methods are more expensive in comparison to conventional methods and their replacement is not cost-effective. The aim of this study was to estimate the prevalence of HCV RNA positivity in anti-HCV negative hemodialysis patients and evaluate new diagnostic methods for the detection and the monitoring of hepatitis C in ESCKD patients. METHODS: The study was performed in four hospitals of Thrace region of Greece and 233 patients with no history of hepatitis C were enrolled. Measurement of anti-HCV antibodies and HCV core antigen was performed by microparticle chemiluminescence immunoassay. Molecular detection of viral RNA was performed by the real-time RT PCR. RESULTS: The mean age of the patients was 64.9 ± 23.3 years. HCV-Ag was positive in 2/233 patients (0.86%). Nevertheless, viral RNA was negative in those patients. CONCLUSIONS: The results of the present study showed that the incidence of HCV-RNA in patients with negative anti-HCV Abs, in hemodialysis patients in Thrace region of Greece was negligible (0/233).

Infants are subjected to hematopoietic stem cell transplantation (HSCT) due to malignant and non-malignant diseases. However, specific data concerning the outcome and transplantation-related complications in infants, as a separate age group, are limited. Our aim was to evaluate the impact of infancy on the outcome, toxicity, and complications after HSCT.We retrospectively analyzed data of 55 infants that underwent HSCT in our unit from May 1997 until February 2020, emphasizing on the probability of overall survival (OS) and the cumulative incidence (CI) of transplantation-related mortality (TRM) and complications.We report a probability of OS of 61%, a CI of TRM at day 100 and 365 post transplantation of 22% and 30%, respectively, and additionally a CI of graft failure, acute graft-versus-host disease (GvHD), and infectious complications, 18%, 44%, and 39%, respectively. No statistically significant association was detected between the above mentioned parameters and diagnosis, the use of myeloablative or non-myeloablative/reduced toxicity conditioning regimens or the type of donor.We conclude that HSCT in infancy is associated with significant mortality and morbidity. This is possibly attributed to endogenous, age-related factors. More specifically, infants may be at a higher risk of toxicities due to the immaturity of developing vital organs and the deficiency of the newly adopted immune system that predisposes them to infectious complications. The development of GvHD further augments the danger of infections, in a potential vice-versa relationship. Moreover, there are few data on pharmacokinetics of chemotherapy agents, making safe and efficacious drug administration hard.

We develop a population pharmacokinetic model to describe Busulfan pharmacokinetics in paediatric patients and investigate by simulations the impact of various sampling schedules on the calculation of AUC. Seventy-six children had 2 h infusions every 6 h. A two-compartment linear model was found to adequately describe the data. A lag-time was introduced to account for the delay of the administration of the drug through the infusion pump. The mean values of clearance, central volume of distribution, intercompartmental clearance, and peripheral volume of distribution were 10.7 L/h, 39.5 L, 4.68 L/h and 17.5 L, respectively, normalized for a Body Weight (BW) of 70 kg. BW was found to explain a portion of variability with an allometric relationship and fixed exponents of 0.75 on clearance parameters and 1 on volumes. Interindividual variability for clearance and volume of distribution was found to be 28% and 41%, respectively, and interoccasion variability for clearance was found to be 11%. Three sampling schedules were assessed by simulations for bias and imprecision to calculate AUC by a non-compartmental and a model-based method. The latter was found to be superior in all cases, while the non-compartmental was unbiased only in sampling up to 12 h corresponding to a once-daily dosing regimen. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

We develop a population pharmacokinetic model to describe Busulfan pharmacokinetics in paediatric patients and investigate by simulations the impact of various sampling schedules on the calculation of AUC. Seventy-six children had 2 h infusions every 6 h. A two-compartment linear model was found to adequately describe the data. A lag-time was introduced to account for the delay of the administration of the drug through the infusion pump. The mean values of clearance, central volume of distribution, intercompartmental clearance, and peripheral volume of distribution were 10.7 L/h, 39.5 L, 4.68 L/h and 17.5 L, respectively, normalized for a Body Weight (BW) of 70 kg. BW was found to explain a portion of variability with an allometric relationship and fixed exponents of 0.75 on clearance parameters and 1 on volumes. Interindividual variability for clearance and volume of distribution was found to be 28% and 41%, respectively, and interoccasion variability for clearance was found to be 11%. Three sampling schedules were assessed by simulations for bias and imprecision to calculate AUC by a non-compartmental and a model-based method. The latter was found to be superior in all cases, while the non-compartmental was unbiased only in sampling up to 12 h corresponding to a once-daily dosing regimen.

The aim of this study was to estimate the immunogenic effect of mRNA vaccine against SARS-CoV-2. This study included 510 participants who received mRNA vaccine. The measurement of anti-COVID-19 antibodies was performed using the Abbott SARS-CoV-2 IgG quantitative assay (Abbott). Overall, mean titer of anti-Spike antibodies was 19,319.2 ± 1787.5 AU/mL. Vaccination induced a robust immunogenic response in those previously infected with SARS-CoV-2 compared with non-infected subjects. Additionally, individuals that were asymptomatic after vaccination produced lower levels of antibodies compared to feverish individuals. In conclusion, remarkably high levels of anti-Spike COVID-19 antibodies were observed after vaccination.

Introduction: The aim of this study was to assess the clinical performance of different automated immunoassays available in Europe to detect anti-SARS-CoV-2 antibodies; an ELISA assay and a CLIA. The second goal was to estimate the seroprevalence of SARS-CoV-2 antibodies among healthcare workers in Evros area during the first pandemic wave of COVID-19. Methods: The study included serum samples from 101 patients with confirmed COVID-19 by RT-PCR and 208 negative patients. Furthermore, it included 1036 healthcare workers (HWs) of the Evros Region, Northern Greece. The measurement of anti-SARS-CoV-2 antibodies was performed using the Abbott SARS-CoV-2 IgG and anti-SARS-CoV-2 ELISA IgG assay (Epitope Diagnostics, USA). Results: Of 101 confirmed COVID-19 patients, 82 were hospitalized and 19 were outpatients. Hospitalized patients had higher IgG levels in comparison to outpatients (6.46±2.2 vs. 3.52±1.52, p

Objectives: To apply therapeutic drug monitoring and dose-individualization of intravenous Busulfan to paediatric patients and evaluate the impact of syringe-pump induced Busulfan infusion lag-time after in vitro estimation. Methods: 76 children and adolescents were administered 2 h intravenous Busulfan infusion every 6 h (16 doses). Busulfan plasma levels, withdrawn by an optimized sampling scheme and measured by a validated HPLC-PDA method, were used to estimate basic PK parameters, AUC, Cmax, kel, t1/2, applying Non-Compartmental Analysis. In vivo infusion lag-time was simulated in vitro and used to evaluate its impact on AUC estimation. Key findings: Mean (%CV) Busulfan AUC, Cmax, clearance and t1/2 for pediatric population were found 962.3 μm × min (33.1), 0.95 mg/L (41.4), 0.27 L/h/kg (33.3), 2.2 h (27.8), respectively. TDM applied to 76 children revealed 6 (7.9%) being above and 25 (32.9%) below therapeutic-range (AUC: 900-1350 μm × min). After dose correction, all patients were measured below toxic levels (AUC < 1500 μm × min), no patient below 900 μm × min. Incorporation of infusion lag-time revealed lower AUCs with 17.1% more patients and 23.1% more younger patients, with body weight

Voriconazole levels were determined with high-performance liquid chromatography (HPLC) and a microbiological agar diffusion assay using a Candida parapsilosis isolate in 103 serum samples from an HPLC-tested external quality control program (n = 39), 21 patients receiving voriconazole monotherapy (n = 39), and 7 patients receiving combination therapy (n = 25). The results of the bioassay were correlated with the results obtained from the external quality control program samples and with the HPLC results in sera from patients on voriconazole monotherapy and on combination therapy with an echinocandin (Spearman's rank correlation coefficient [rs], > 0.93; mean ± standard error of the mean [SEM] % difference

Voriconazole levels were determined with high-performance liquid chromatography (HPLC) and a microbiological agar diffusion assay using a Candida parapsilosis isolate in 103 serum samples from an HPLC-tested external quality control program ( n = 39), 21 patients receiving voriconazole monotherapy ( n = 39), and 7 patients receiving combination therapy ( n = 25). The results of the bioassay were correlated with the results obtained from the external quality control program samples and with the HPLC results in sera from patients on voriconazole monotherapy and on combination therapy with an echinocandin (Spearman's rank correlation coefficient [ r s ], > 0.93; mean ± standard error of the mean [SEM] % difference

Background: Anti-thymocyte globulin (ATG) has been used to prevent graft failure/rejection in the setting of allogeneic stem cell transplantation (allo-SCT) for hemoglobinopathies; however, epidemiology data for transplant-related infections in this population are scarce. Method: We retrospectively analyzed the epidemiology of bacterial, fungal, viral, and parasitic infections in a cohort of 105 children and adolescents with β-thalassemia (n = 100) or sickle cell disease (n = 5) who underwent allo-SCT using human leukocyte antigen (HLA)-identical sibling (n = 96) or HLA-compatible unrelated donors (n = 9) in a single institution. All patients received an ATG-based conditioning regimen. Results: The cumulative incidence of cytomegalovirus (CMV) viremia was 45.7% (95% confidence interval [CI] 33-55%), developing at a median of 48 (range 12-142) days without evidence of overt CMV disease. Herpes zoster developed in 8 patients at a median of 12 months post transplant, while 10 patients presented with late onset hemorrhagic cystitis at a median of 35 days post transplant. The cumulative incidence of bacteremia was 17.1% (95% CI 10.6-25%), occurring at a median of 74 (range 24-110) days. No patient developed probable or definite invasive fungal infection. Four deaths were recorded; 2 of them were attributed to infections (toxoplasmosis and Pneumocystis jirovecii pneumonia, respectively). Conclusion: The rate of infections after allo-SCT, using an ATG-containing preparative regimen, in our population of pediatric patients with hemoglobinopathies is comparable to that reported elsewhere with the use of non-ATG containing regimens. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Background: Post transplant lymphoproliferative disorder (PTLD) is a heterogeneous complication of HSCT. It comprises a spectrum of pathogenetic mechanisms and clinical manifestations. It is mostly associated with EBV infection, either as a consequence of reactivation in the post transplant period or less frequently from primary infection. WHO classification defines four major histopathologic subtypes: 1. early plasmacytic hyperplasia and infectious mononucleosis (IM)-like 2. polymorphic lesions which may be polyclonal or focally monoclonal (P-PTLD) 3. monomorphic lesions that fulfill criteria for aggressive B- or T/NL-cell neoplasm (M-PTLD) 4. classic Hodgkin-type Lymphomas (CHL-PTLD). Indistinguishable categories, such as Hodgkin-like P-or M-PTLD might represent laborious diagnostic dilemmas. In literature, PTLD occurs in less than 1% of non T-cell-depleted grafts from matched siblings compared with as high as 25% in unrelated donor (VUD) recipients. There are several risk factors such as the type of conditioning and the use of ATG, the degree of immunosuppression and complications such as concurrent infections and GvHD. Objectives: To present our experience regarding the frequency, presentation and outcome of EBV related PTLD in a paediatric population of allo-HSCT recipients with haematological malignancies, to assess the risk factors and inquire into the heterogeneity in clinical presentation and outcome. Patients-Methods: From January 2004 until December 2014, 177 allo-HSCTs for myeloid and lymphoid malignancies were performed in patients aged 3 months to 19 years. PTLD was recorded in 15 (8 male) with median age of 13.24 yrs (range 5.0-17.9yrs). 11 patients had VUD, 4 patients had an haploidentical related donor and the grafts depleted of T-cells. 12 patients had peripheral blood and 3 had bone marrow as the source of HSCs. 4 were given a fully matched graft, 6 had 1 HLA antigen or allele mismatched donors, 1 patient had a 2 HLA antigen mismatched donor and 4 had 5/10 HLA matched haploidentical donors. All except for 2 patients were EBV IgG positive and the two seronegative patients had an EBV IgG positive donor. The conditioning regimens used were Busulfan or Treosulfan based in 11 patients with the addition of a combination of Cyclophosphamide, Fludarabine, Melphalan, VP16 and ATG. The latter was administered to all patients. GvHD prophylaxis consisted of Cyclosporin A and Methotrexate. Five patients (1 male) are alive and well with a median follow up of 43.1 months (range 8.3-69.2). Results: Neutrophil and platelet engraftment occurred at a median of 20 (range 14-24) and 21 days (range 14-48) respectively. Acute GvHD (stage II-IV) was recorded in 9 patients. Serial quantitative EBV-DNA/ml was employed routinely and the median day of confirmation of a rising level above 1.0x103/ml was day +58 post transplant. Median EBV copies at diagnosis were 2.3x104/ml(range 1.3x103/ml-2.15x105/ml). EBV positivity was immediately recorded post DLI in 3 patients and reactivation occurred post subsequent DLI. Immune reconstitution had not been achieved in any patient at the time of diagnosis. Median WBC count was 4.1x109/lt (1.04X109/lt - 8.78x109/lt) and all patients had absolute lymphopenia. 9 patients had documented other viral and/or bacterial infections. 2 patients developed M-PTLD, consistent unequivocally with DLBCL, 7 patients had P-PTLD and 6 patients had IM-like PTLD with plasmacytic hyperplasia only. All had anti-CD20, two patients had additional chemotherapy. Although responsive to EBV treatment, 3 died of primary disease recurrence while PTLD failed to regress in 7 patients who died of a multitude of complications. With a median follow up of 43,1 months (range 8.3-69.2), 5 patients (1 male) are alive and well. Conclusions: Nearly all HSCT recipients are EBV infected or will be infected eventually, yet only a fraction develop EBV driven PTLD. In our population the incidence was found to be 8.47%. PTLD exhibits a spectrum of features ranging from non specific and reactive to life threatening, indistinguishable from lymphoma. Administration of ATG, the type and extend of HLA mismatch, multiple sites of disease, immune suppression and concurrent infections heighten the risk of systemic manifestation. Rising EBV loads are strongly associated with impending PTLD, which can occur even with an overall modest viral load, thus requiring prompt recognition and early intervention. Disclosures No relevant conflicts of interest to declare.

Introduction: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative option for many children with various genetic or malignant diseases. However not all children in need for HSCT have a suitable donor available. For such cases in vitro fertilization (IVF) with pre-implantation genetic diagnosis (PGD) combined with human leukocyte antigen (HLA) tissue typing has been used to select an IVF healthy and HLA-matched embryo in order to give birth to a child who may serve as a stem cell donor. We report our experience with five children transplanted from HLA-matched siblings selected after IVF and PGD in our center. Methods and Patients: The clinical protocol was approved by the center’s Institutional Research and Ethics Committee. Written informed consent was obtained from parents. Hormonal stimulation for IVF, culture techniques, PGD and HLA-typing were performed according to standard protocols. Detection of the genetic disease mutation was performed by using mini-sequencing. Embryos genotyping was performed by using multiplex polymerase chain reaction (PCR) analysis of informative polymorphic short tandem repeat (STR) markers. Healthy and HLA-identical embryos were transferred 6 days after fertilization to the uterus of the respective mothers. Confirmatory genetic testing and HLA-typing were performed during the first trimester of pregnancy by using chorionic villus sampling. Patient’s characteristics are shown in Table 1. None of our patients had an available matched sibling donor. All patients underwent myeloablative conditioning consisting of busulfan, cyclophosphamide and antithymocytic globulin. GVHD prophylaxis consisted of CyA plus Methotrexate. Stem cell graft consisted of bone marrow plus cord blood in 4 out of 5 patients, while one patient received bone marrow only. Results: All couples underwent a single cycle of IVF resulting into the generation of 78 embryos. Fourteen embryos were healthy and HLA-identical with their sibling and 10 of them were transferred to the uterus of the respective mother giving birth to a total of 6 healthy children. Results of IVF, PGD and HLA-typing are shown in more detail in Table 2. The median age of the donor at the time of HSCT was 16 months. The median total nucleated cell (TNC) concentration of cord blood grafts was 2.3x107/kg, while the median CD34+ cell was 0.47x105/kg. The median TNC and CD34 cell concentration of bone marrow grafts was 1,97x108/kg and 5,09x106/kg respectively. All patients achieved sustained engraftment of donor cells. Mild acute GVHD of the skin was observed in one out of 5 patients. As of today, with a median follow up period of 4 years, all patients are alive with complete donor chimerism, without chronic GVHD and free of disease. Conclusions: IVF and PGD/HLA typing methodology should be considered and discussed with parents in cases where no HLA-matched donor is available. The procedure can be applied only in cases requiring non-urgent HSCT, and in parents of reproductive age. | Patient | Sex | Age (years) | Disease | Previous treatments | Date of transplant | | ------- | ------ | ----------- | ----------------------------- | ----------------------------------------- | ------------------ | | 1 | Male | 4,5 | Chronic granulomatous disease | Interferon-gamma, antibiotics | 2/10/2007 | | 2 | Male | 4 | Chronic granulomatous disease | antibiotics | 1/7/2008 | | 3 | Male | 11 | Chronic myeloid leukemia | Hydroxyurea, imatinib | 21/7/2009 | | 4 | Male | 4 | Thalassemia major | RBC transfusions | 4/5/2010 | | 5 | Female | 4,5 | Diamond-Blackfan anemia | Corticosteroids, RBC transfusions | 30/4/2013 | Table 1: Patient’s characteristics | Patients | IVF (cycles) | Number of embryos after IVF | Number of healthy and HLA-identical embryos | Number of healthy and HLA-identical transferred embryos | Number of healthy and HLA-identical borned children | | -------- | ------------ | --------------------------- | ------------------------------------------- | ------------------------------------------------------- | --------------------------------------------------- | | 1 | 1 | 37 | 6 | 2 | 1 | | 2 | 1 | 11 | 2 | 2 | 1 | | 3 | 1 | 10 | 2 | 2 | 1 | | 4 | 1 | 10 | 1 | 1 | 1 | | 5 | 1 | 10 | 3 | 3 | 2 | Table 2: Results of IVF, PGD and HLA-typing Disclosures No relevant conflicts of interest to declare.