Chemically defined cytokine-free expansion of human haematopoietic stem cells.

Haematopoietic stem cells (HSCs) are a rare cell type that reconstitute the entire blood and immune systems after transplantation and can be used as a curative cell therapy for a variety of haematological diseases1,2. However, the low number of HSCs in the body makes both biological analyses and clinical application difficult, and the limited extent to which human HSCs can be expanded ex vivo remains a substantial barrier to the wider and safer therapeutic use of HSC transplantation3. Although various reagents have been tested in attempts to stimulate the expansion of human HSCs, cytokines have long been thought to be essential for supporting HSCs ex vivo4. Here we report the establishment of a culture system that allows the long-term ex vivo expansion of human HSCs, achieved through the complete replacement of exogenous cytokines and albumin with chemical agonists and a caprolactam-based polymer. A phosphoinositide 3-kinase activator, in combination with a thrombopoietin-receptor agonist and the pyrimidoindole derivative UM171, were sufficient to stimulate the expansion of umbilical cord blood HSCs that are capable of serial engraftment in xenotransplantation assays. Ex vivo HSC expansion was further supported by split-clone transplantation assays and single-cell RNA-sequencing analysis. Our chemically defined expansion culture system will help to advance clinical HSC therapies.

Ex vivo expansion of human hematopoietic stem cells and clinical applications.

Hematopoietic stem cells (HSCs) are a rare population of cells found in the bone marrow that play a critical role in lifelong hematopoiesis and the reconstitution of the hematopoietic system after hematopoietic stem cell transplantation. Hematopoietic stem cell transplantation remains the only curative treatment for patients with refractory hematologic disorders, and umbilical cord blood (CB) serves as an alternative stem cell source due to its several advantageous characteristics, including human leukocyte antigen flexibility and reduced donor burden. However, CB also has the disadvantage of containing a small number of cells, resulting in limited donor selection and a longer time for engraftment. Therefore, the development of techniques to expand HSCs ex vivo, particularly umbilical CB, is a goal in hematology. While various combinations of cytokines were once the mainstream approach, these protocols had limited expansion rates and did not lead to clinical application. However, in recent years, the development of a technique in which small molecules are added to cytokines has enabled the stable, long-term ex vivo expansion of human HSCs. Clinical trials of expanded umbilical CB using these techniques have been undertaken and have confirmed their efficacy and safety. In addition, we have successfully developed a recombinant-cytokine-free and albumin-free culture system for the long-term expansion of human HSCs. This approach could offer the potential for more selective expansion of human HSCs compared to previous protocols. This review discusses ex vivo culture protocols for expanding human HSCs and presents the results of clinical trials using these techniques, along with future perspectives.

Significance of absolute neutrophil count before allogeneic hematopoietic stem cell transplantation in adult patients with aplastic anemia.

The impact of absolute neutrophil count (ANC) before allogenic hematopoietic stem cell transplantation (HSCT) on the outcomes for patients with aplastic anemia (AA) remains unclear. We retrospectively evaluated the relationship between ANC before transplantation and patient outcomes, involving 883 adult Japanese patients with AA who underwent allogeneic HSCT as their first transplantation between 2008 and 2020. Patients were divided into three groups based on ANC: 0/µL (n = 116); 1-199 (n = 210); and ≥ 200 (n = 557). In the low ANC groups (ANC < 200), patient age was higher, previous anti-thymocyte globulin (ATG) treatments were infrequent, duration from diagnosis to transplantation was shorter, hematopoietic cell transplantation-comorbidity index (HCT-CI) was higher, ATG-based conditioning was used infrequently, and peripheral blood stem cell from related donor and cord blood were used frequently. In multivariate analysis, patient age, previous ATG treatment, HCT-CI, stem cell source, and ANC before transplantation were significantly associated with 5-year overall survival (OS) ("ANC ≥ 200": 80.3% vs. "ANC 1-199": 71.7% vs. "ANC 0": 64.4%). The cumulative incidence of bacterial infection, invasive fungal disease, and early death before engraftment were significantly higher in the low ANC groups. Among patients with ANC of zero before transplantation, younger patient age, shorter duration from diagnosis to transplantation, HCT-CI of 0, and bone marrow from related donor as stem cell source were significantly associated with better OS. Consequently, ANC before allogeneic HSCT was found to be a significant prognostic factor in adult patients with AA. Physicians should pay attention to ANC before transplantation.

[Japanese patient preferences between ravulizumab and eculizumab for the treatment of paroxysmal nocturnal hemoglobinuria].

Ravulizumab is the first long-acting complement inhibitor approved for paroxysmal nocturnal hemoglobinuria (PNH) treatment. We evaluated patient preference for ravulizumab or eculizumab among Japanese adults with PNH. The ALXN1210-PNH-301 (NCT02946463) and ALXN1210-PNH-302 (NCT03056040) studies included 23 Japanese adults who are enrolled in complement inhibitor treatment-naive and eculizumab (≥6 months) treatment. Patient preference was assessed using the PNH-specific patient preference questionnaire (PNH-PPQ©). Most patients preferred ravulizumab (19/23, 82.6%), none preferred eculizumab, and four (17.4%) reported no preference (χ2 test, p<0.005). The preference for ravulizumab was driven by its lower infusion frequency (every 8 weeks) compared with eculizumab (every 2 weeks). The included Japanese patients with PNH preferred ravulizumab because of its reduced infusion frequency, which increases activity planning ability, treatment convenience, and overall quality of life, as compared with eculizumab. These data provide useful insight into patient perspectives and may aid decision-making for PNH treatment.

Improved survival after single-unit cord blood transplantation using fludarabine and melphalan-based reduced-intensity conditioning for malignant lymphoma: impact of melphalan dose and graft-versus-host disease prophylaxis with mycophenolate mofetil.

We evaluated 413 adult patients with lymphoma who underwent unrelated cord blood transplantation (UCBT) with fludarabine and melphalan (FM)-based reduced-intensity conditioning between 2002 and 2017 to investigate longitudinal changes in outcomes and the optimal melphalan dose and graft-versus-host disease (GVHD) prophylaxis regimen. Outcomes were compared between FM80/100 (melphalan dose: 80 or 100 mg/m2) and FM140 (melphalan dose: 140 mg/m2), as well as between calcineurin inhibitor (CNI) plus methotrexate (MTX), CNI plus mycophenolate mofetil (MMF), and CNI alone. The 3-year overall survival (OS) and non-relapse mortality (NRM) rates improved over time (OS: 27% in 2000s vs. 42% in 2010s, p < 0.001; NRM: 43% in 2000s vs. 26% in 2010s, p < 0.001). Multivariable analysis showed that in the 2000s, melphalan dose and GVHD prophylaxis regimen did not affect any outcomes. In the 2010s, FM80/100 (vs. FM140) related to better OS (hazard ratio [HR] 0.62, p = 0.01) and NRM (HR 0.52, p = 0.016). MTX + CNI and CNI alone (vs. CNI + MMF) related to worse OS (CNI + MTX, HR 2.01, p < 0.001; CNI alone, HR 2.65, p < 0.001) and relapse/progression (CNI + MTX, HR 2.40, p < 0.001; CNI alone, HR 2.13, p = 0.023). In recent years, the use of FM80/100 and CNI + MMF significantly reduced the risk of NRM and relapse/progression, respectively, and resulted in better OS after UCBT for lymphoma.

Risk factor analysis for cytomegalovirus reactivation under prophylaxis with letermovir after allogeneic hematopoietic stem cell transplantation.

BACKGROUND: Letermovir has been approved as a novel cytomegalovirus (CMV) prophylactic agent after allogeneic hematopoietic stem cell transplantation (HSCT). However, there are still insufficient data to properly evaluate the real-world role of letermovir, and the risk factors for CMV reactivation under letermovir prophylaxis have not been clarified. METHODS: We performed a single-institution retrospective analysis of patients under prophylaxis with or without letermovir who underwent allogeneic HSCT between March 2012 and December 2019. In August 2018, letermovir was added to the clinical practice at our institution for the prophylaxis of CMV reactivation in allogeneic HSCT recipients. Patients who underwent HSCT without prophylactic letermovir from March 2012 until September 2018 served as a historical control. RESULTS: The cumulative incidence of clinically significant CMV infection (CS-CMVi) was significantly lower in the letermovir group than in the historical control group not receiving letermovir (30.2% vs. 71.6%, p < .05, at 100 days). In addition, the cumulative incidence of non-relapse mortality (NRM) at day 500 was significantly lower in the letermovir group (4.7% vs. 19.8%, p < .05). We then performed a risk factor analysis for developing CS-CMVi in the letermovir group. The only significant factor identified by this multivariable analysis was transplantation from a CMV seronegative donor to a seropositive recipient (Hazard ratio = 2.76, 95% confidence interval 1.14-6.68, p < .05). CONCLUSION: Our study showed that letermovir prophylaxis significantly reduced the incidence of CS-CMVi and NRM in a real-world setting and that the CMV serostatus of the donor remained as a risk factor for CS-CMVi even under letermovir prophylaxis.

Usefulness of the FilmArray Meningitis/Encephalitis Panel in diagnosis of central nervous system infection after allogeneic hematopoietic stem cell transplantation.

PURPOSE: The BioFire FilmArray® Meningitis/Encephalitis Panel (FAMEP) is designed to rapidly and accurately detect common multiple pathogens that cause central nervous system (CNS) infection, including viruses, bacteria, and yeast. The FAMEP's usefulness in the setting of allogeneic hematopoietic stem cell transplantation (HSCT) has not been fully evaluated. This retrospective study evaluated the usefulness of the FAMEP in the screening for CNS infection after allogeneic HSCT. METHODS: Cerebrospinal fluid (CSF) was obtained from 12 patients to evaluate the causes of CNS disorders after allogeneic HSCT, and the FAMEP was applied. RESULTS: The median day of the FAMEP evaluations was 27 days post-transplant (range, 0-390). Human herpesvirus 6 (HHV-6) was detected in three patients and cytomegalovirus was detected in one patient, leading to the diagnosis of encephalitis/myelitis. In three patients (HHV-6, n = 2; CMV, n = 1), the presence of the viruses was confirmed by conventional real-time polymerase chain reaction (PCR). However, in the remaining patient with HHV-6 detected by the AMEP, HHV-6 was not detected by real-time PCR at the onset but was detected 7 days later. The treatments for the detected viruses improved the clinical conditions in the four patients. CONCLUSIONS: Our results suggest that the FAMEP can be a useful sensitive assay in the screening and diagnosis of CNS viral infections after allogeneic HSCT.

Simultaneous quantification of dasatinib, nilotinib, bosutinib, and ponatinib using high-performance liquid chromatography-Photodiode array detection.

BACKGROUND: Dasatinib, nilotinib, and bosutinib, second-generation tyrosine kinase inhibitors (TKIs), and ponatinib, a third-generation TKI, are approved pharmaceuticals used in the treatment of chronic myeloid leukemia (CML). Although liquid chromatography-tandem mass spectrometry assays for simultaneous quantification of the four TKIs in human serum have been reported in the literature, a high-performance liquid chromatography (HPLC) assay that simultaneously quantifies these compounds has not yet been developed. This study aims to establish and validate an efficient HPLC analytical method using a photodiode array (PDA) detector for the simultaneous quantification of the four TKIs. METHODS: Calibration standards were prepared by serial dilution of serum samples containing the four TKIs, followed by solid-phase extraction. The four TKIs were eluted in order within 10 min using a binary HPLC gradient system. RESULTS: The calibration ranges were 2-500 ng/ml for dasatinib, 100-5000 ng/ml for nilotinib, and 10-500 ng/ml for bosutinib and ponatinib. Intra-day and inter-day precision and accuracy values were found to be in accordance with the U.S. Food and Drug Administration guidelines. The recovery rates were 92.9%-96.0%, 80.7%-86.1%, 91.6%-99.0%, and 86.4%-92.6% for dasatinib, nilotinib, bosutinib, and ponatinib, respectively. CONCLUSION: To the best of our knowledge, this is the first report of an HPLC-PDA analytical method that allows efficient simultaneous quantification of the four TKIs in the serum of patients with CML. We believe that the method developed herein can improve the efficiency of therapeutic drug monitoring in patients with CML in clinical practice.

Adoptive cell therapy using tumor-infiltrating lymphocytes for melanoma refractory to immune-checkpoint inhibitors.

To evaluate the feasibility of adoptive cell therapy (ACT) using ex vivo-expanded tumor-infiltrating lymphocytes (TILs) in Japanese patients with melanoma who failed immune-checkpoint inhibitor therapy, an open-label, single-arm, pilot study was conducted. We investigated the immunological and genetic factors of the pretreatment tumor and expanded TILs that may be associated with the clinical response. The treatment protocol comprised preparation of TIL culture, lympho-depleting non-myeloablative preconditioning with cyclophosphamide and fludarabine, TIL infusion, and intravenous administration of low-dose IL-2. Three patients of clinical subtypes mucosal, superficial spreading, and acral melanoma underwent TIL-ACT. Most severe adverse events, including fever and leukopenia, were manageable with the supportive regimen specified in the protocol, suggesting that the TIL-ACT regimen is suitable for Japanese patients with melanoma. One patient showed a short-term partial response, one relatively long-stable disease, and one experienced disease progression. Whole-exome and transcriptional sequencing of isolated tumor cells and immunohistochemical analyses before TIL-ACT revealed various immunostimulatory factors, including a high tumor mutation burden and immune cell-recruiting chemokines, as well as various immunosuppressive factors including TGF-ß, VEGF, Wnt/ß-catenin, and MAPK signaling and epithelial-to-mesenchymal transition, which might influence the efficacy of TIL-ACT. Our results imply mechanisms for the antitumor effect of and resistance to TIL-ACT. Further studies of immune-resistant mechanisms of TIL-ACT are warranted. This study is registered with the UMIN Clinical Trial Registry (UMIN 000011431).

Toxoplasmosis after allogeneic hematopoietic stem cell transplantation: Impact of serostatus-based management.

Toxoplasmosis caused by Toxoplasma gondii (T. gondii) is a serious infectious complication after allogeneic hematopoietic stem cell transplantation (HSCT). The incidence of toxoplasmosis varies widely because of the variabilities of seroprevalence among patient populations. The incidence and the optimal management of toxoplasmosis after allogeneic HSCT in a patient population with a low seroprevalence have not been fully evaluated. We conducted a single-center retrospective study evaluating toxoplasmosis in Japanese patients who underwent allogeneic HSCT. Of the 728 evaluable patients, only 5 developed toxoplasmosis with a median onset of day 60 post-transplant (range, day 55-393). The cumulative incidence was 0.7% (95% CI: 0.3%-1.5%) at day 500 post-transplant. Four of the five patients succumbed due to toxoplasmosis. The more recently treated 220 patients (not the earlier 508 patients) were screened for the T. gondii serostatus, and prophylactic treatment with trimethoprim/sulfamethoxazole was applied. All five patients with toxoplasmosis were in the unscreened group, and there was no case of toxoplasmosis after the introduction of the screening and prophylactic treatment. Our results suggest that toxoplasmosis after allogeneic HST is rare but can develop as a life-threatening complication even in the populations with low seroprevalence, and that prophylactic treatment for seropositive patients could effectively prevent toxoplasmosis.

[Spontaneous remission of relapsed skin lesions of ALK-positive anaplastic large cell lymphoma after autologous stem cell transplantation].

A 44-year-old woman was diagnosed with anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) with clinical stage IVA (nodal and bladder involvement). Complete response (CR) was achieved after the CHOP chemotherapy; however, 12 months after the last course of chemotherapy, ALCL relapsed in the form of skin lesions without nodal involvement. After achieving a second CR with chemotherapy, autologous stem cell transplantation was performed. Two months after transplantation, the disease again relapsed as multiple skin lesions. Electron beam irradiation was performed; however, other skin lesions appeared thereafter and spontaneously disappeared. At present, 3.4 years after the transplantation, the patient is free from disease. ALK-positive ALCL relapsing as skin lesions may behave differently from the nodal relapse. An accumulation of cases is required to elucidate ALCL characteristics relapsing as skin lesions.

Outcome of stem cell transplantation for Waldenström's macroglobulinemia: analysis of the Japan Society for Hematopoietic Cell Transplantation (JSHCT) Lymphoma Working Group.

The role of stem cell transplantation (SCT) for patients with Waldenström's macroglobulinemia (WM) remains undetermined. Therefore, we retrospectively evaluated the outcome of autologous and allogeneic SCT for patients with WM using the registry database of the Japan Society for Hematopoietic Cell Transplantation. Forty-six patients receiving autologous and 31 receiving allogeneic SCT were analyzed. The allogeneic SCT group included more patients with advanced disease status at transplant and received more lines of chemotherapy. The cumulative incidences of non-relapse mortality (NRM) at 1 year were 30.0% (95% CI, 14.7-46.9%) in the allogeneic SCT and 0% in the autologous SCT group. The estimated 3-year overall (OS) and progression-free (PFS) survival rates were 84.5% (95% CI, 66.0-93.4%) and 70.8% (95% CI, 53.0-82.9%) in the autologous SCT group, and 52.2% (95% CI, 32.5-68.6%) and 45.0% (95% CI, 26.3-62.0%) in the allogeneic SCT group. No patients died after the first 2 years following allogeneic SCT. In univariate analyses, disease status at SCT was significantly associated with PFS in autologous SCT, and with OS and PFS in allogeneic SCT. These results suggest that both autologous and allogeneic SCT have each potential role in WM. Allogeneic SCT is more curative for WM, but is associated with high NRM.

Seasonal changes in indoor airborne fungal concentration in a hematology ward.

Invasive fungal disease (IFD) is an important infectious complication of hematological disorders, especially in hematopoietic stem cell transplantation recipients. Evidences suggest seasonal and/or geographical variations in the airborne fungal counts and a relationship between those counts and the incidence of IFD. We evaluated the concentrations of indoor airborne fungi quantitated over the course of one year in a hematology ward in Japan. In January, April, July, and October, fixed volumes of air samples were obtained by an air sampler in a hematology ward not equipped with a high-efficiency particulate air filter and incubated in fugal cultures. Samples were also obtained from a protective environment in the same ward and were evaluated. The number of fungal colonies per 50 L of sampled air was highest in October (median 2.25 (range, 0.2-7.0)), which was significantly higher than those in the other three months (0.1 (range, 0-1.0) in January; 0 (0-0) in April; 0.55 (0-2.5) in July; P < 0.01)). Commonly identified pathogens included Penicillium and Cladosrporium species, but Aspergillus species was detected only in July and October samples. These results suggest a seasonal variation in indoor airborne fungal concentrations in Japan, which could affect the epidemiology of IFD.

[Efficacy of photocatalytic air purifiers in reducing dimethyl sulfide malodor following cryopreserved peripheral blood stem cell infusion].

Dimethyl sulfoxide (DMSO) is used as a cryoprotectant for peripheral blood stem cells (PBSC) preservation. Dimethyl sulfide (DMS) is a metabolite of DMSO secreted through patients' breath after PBSC infusion. It possesses malodor causing an unpleasant environment. We evaluated the efficacy of a photocatalyst environment purifier, which has the potential to lyse toxic substances, in reducing DMS malodor. High DMS concentration in the air after PBSC infusion rapidly decreased after operating the device. Our results suggest that photocatalytic reaction has the potential to reduce the DMS odor associated with PBSC infusion.

Human Herpesvirus 6 Reactivation Evaluated by Digital Polymerase Chain Reaction and Its Association With Dynamics of CD134-Positive T Cells After Allogeneic Hematopoietic Stem Cell Transplantation.

BACKGROUND: Human herpesvirus 6 (HHV-6) causes life-threatening central nervous system disorders after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Recent studies implicated CD134 as a specific receptor of HHV-6B and demonstrated that its expression levels in CD4-positive T cells after allo-HSCT could be related to the reactivation of HHV-6. We prospectively evaluated the relationship between HHV-6 reactivation and CD134+ T cells in the recipients of allo-HSCT. METHODS: HHV-6 viral load in plasma was quantitatively measured weekly after allo-HSCT by digital polymerase chain reaction in 34 patients. The ratio of CD134 in CD4+ T cells (CD134/CD4 ratio) was serially measured by flow cytometry before and after transplantation. RESULTS: HHV-6 reactivation was detected in 23 patients (68%). The CD134/CD4 ratio before conditioning was significantly higher in patients with HHV-6 reactivation than in those without (median, 3.8% vs 1.5%, P < .01). In multivariate analysis, a higher CD134/CD4 ratio before conditioning was significantly associated with the incidence of HHV-6 reactivation (odds ratio, 10.5 [95% confidence interval, 1.3-85.1], P = .03). CONCLUSIONS: A higher CD134/CD4 ratio before conditioning was associated with a higher risk of HHV-6 reactivation, suggesting that the rate may be a promising marker for predicting HHV-6 reactivation after allo-HSCT.

Geriatric screening tools predict survival outcomes in older patients with diffuse large B cell lymphoma.

The proportion of elderly patients with diffuse large B cell lymphoma (DLBCL) appears to be increasing, with outcomes varying widely because of the patients' heterogeneity. Geriatric assessment is used to predict prognosis in elderly patients with DLBCL, but the utility of two simple screening tools for patients with DLBCL, the Flemish version of the Triage Risk Screening Tool (fTRST) and G8, has remained to be elucidated. We retrospectively assessed patients using fTRST and G8, and evaluated the impacts of the scores on survival outcomes in older patients with newly diagnosed DLBCL. A total of 59 patients aged 65 years or older and who were diagnosed with DLBCL were included. The median age was 77 years (range, 65-91 years), and the initial treatments were R-CHOP (63%) and R-THPCOP (31%). The estimated 2-year overall survival (OS) rate was significantly lower in patients with abnormal fTRST scores (≥ 2; N = 17) than in those with normal fTRST scores (< 2; N = 42): (50.5% (95% CI, 22.7-73.0%) vs. 82.2% (95% CI, 63.8-91.8%), P = 0.007). The estimated 2-year OS rate was significantly lower also in patients with abnormal G8 scores (≤ 14; N = 38) than in those with normal G8 scores (> 14; N = 21): (66.1% (95% CI, 46.7-79.5%) vs. 86.8% (95% CI, 55.7-96.7%), P = 0.03, respectively). These associations were independently significant after adjusting for other significant factors by multivariate analysis. These results suggest that the easy-to-use geriatric screening tools, fTRST and G8, have strong prognostic value for OS in older patients with DLBCL.

Impact of immunoglobulin G2 subclass level on late-onset bacterial infection after allogeneic hematopoietic stem cell transplantation.

BACKGROUND: Immunoglobulin (Ig) G2 subclass deficiency is known to be associated with recurrent bacterial respiratory infections caused by capsulated bacteria and is found mostly in pediatric patients. However, its impact after allogeneic hematopoietic stem cell transplantation (HSCT) has not been fully assessed. METHODS: We retrospectively evaluated the relationship between IgG2 subclass levels and bacterial pneumonia in 74 adult patients who survived longer than 2 years after allogeneic HSCT. RESULTS: During the evaluation period, nine patients developed bacterial pneumonia. The median IgG2 level was significantly lower in patients with an infectious episode than in those without (143 mg/dL vs 287 mg/dL; P < 0.01). In multivariate analysis, a history of rituximab therapy and cord blood as a stem cell source were significantly associated with decreased levels of both IgG2 and IgG2/IgG ratios (P < 0.05). CONCLUSIONS: Suboptimal serum IgG2 levels could increase susceptibility to late-onset bacterial pneumonia after allogeneic HSCT. IgG2 levels should be considered carefully, especially in patients receiving cord blood transplantation and/or rituximab treatment.

Invasive hepatic mucormycosis: A case report and review of the literature.

Mucormycosis generally develops under immunocompromised conditions, including hematological malignancies and solid organ or hematopoietic stem cell transplantation. Although mucormycosis usually affects the lungs and paranasal sinuses, sporadic cases of invasive mucormycosis of the liver have been reported. We hereby report a patient with myelofibrosis who developed hepatic mucormycosis diagnosed by post-mortem examination. An extensive literature review identified 13 reported cases of hepatic mucormycosis, including ours, without lung involvement. Most of the underlying diseases or conditions were hematological malignancies and solid organ transplantation. Three cases had splenic lesions and four had gastrointestinal lesions, suggesting the possibility of translocation to the liver and/or spleen from the gastrointestinal tracts. Hepatic mucormycosis should be recognized as one of the presentations of invasive mucormycosis, especially when hepatic nodules are found in immunocompromised patients such as those with hematological malignancy or recipients of solid organ transplantation.

[Bacteriocidal effects of introducing copper products on highly touched areas in hematology ward].

Nosocomial infection via the hospital environment is a serious problem, and highly touched surfaces are the main route of transmission. Copper has been reported to possess bacteriocidal effects, and the introduction of copper-impregnated products is receiving attention as a potential component of hospital infection control. In this study, copper-impregnated door handles as highly touched areas were introduced in a hematology ward, and their bacteriocidal effects were evaluated in comparison with conventional products. All 12 samples obtained from conventional door handles were positive for bacterial cultures, whereas only 5 of 18 samples from copper-impregnated handles were positive (P<0.0001). The mean number of bacterial colonies per milliliter of sample was 300 (range: 40-1.1×106) in samples from conventional handles, but it was significantly lower in samples from copper-impregnated handles (0; range: 0-220, P<0.0001). While various types of bacteria grew on conventional handles, most of the bacteria on copper-impregnated handles were Bacillus subtilis. These results suggest that the introduction of copper-impregnated products would be useful for hospital infection control by reducing the bacterial burden on highly touched areas. However, the efficacy of this approach against spore-forming bacteria should be further investigated.