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Introduction: The optimal dosage of anti-thymocyte globulin (ATG) may influence the outcome of patients after allogenic haematopoietic stem cell transplantation (HSCT). The aim of our study was to analyse human cytomegalovirus (CMV) infection data, incidence of graft-versus-host disease and other clinical endpoints comparing two patients cohorts that were administered two different Thymoglobuline Genzyme doses as part of the HSCT conditioning regimen., Materials and Methods: Total of 65 adult patients received ATG (7.5 mg/kg or 6 mg/kg) as a part of the fludarabine/busulfan/ATG conditioning regimen. CMV DNAemia was monitored after HSCT using quantitative real-time PCR and preemptive treatment was started for viral loads above 1000 cp/ml., Results: The mild ATG dose reduction extended the time to the first CMV detection after transplantation (28 days for 7.5 mg/kg dose vs. 40 days for 6 mg/kg dose, p = 0.04). But it did not reduce the incidence or influence first anti-CMV treatment onset, the initial viral load, peak viral load in whole blood or the antiviral therapy parameters (all p 0.18). No impact of ATG dose reduction on incidence of graft-versus-host-disease, relapse of underlying disease or mortality within first year after transplantation (all p 0.32) were observed., Conclusions: The reduced ATG dosages can allow lower toxicity of conditioning regimen while keeping the performance.

Objective: To determine the incidence of infection with ganciclovir-resistant cytomegalovirus (CMV) in adult allogeneic hematopoietic stem cell transplant (HSCT) recipients. Clinical resistance or treatment failure was defined as persistent DNAemia or increasing viral load in peripheral blood after 2 weeks of virostatic treatment. The association between the treatment failure and viral resistance was analysed. The presence of ganciclovir-resistant CMV strains was confirmed by genotypic testing able to detect mutations conferring resistance., Methods: In 2012 and 2014, 40 patients who underwent allogeneic HSCT for hematologic malignancies and were treated for human CMV reactivation/disease were followed up prospectively. In patients with treatment failure, CMV DNA was isolated and analysed by nucleotide sequence analysis of the UL 97 and UL 54 genes conferring resistance to the virostatic agent., Results: The treatment failure occurred in seven patients, but ganciclovir resistance conferring mutations were only detected in two of them (mutations L595F and M460I in the UL 97 gene). Another mutation in the UL 97 gene (N510S) was found in a patient with recurrent CMV replication who needed to be retreated but did not meet the criteria for treatment failure., Conclusion: The low incidence of genetically confirmed ganciclovir-resistant CMV isolates in HSCT recipients with relatively common clinical treatment failure suggests that the mechanism underlying slower viral clearance is often other than mutations conferring ganciclovir resistance to the virus.