Procalcitonin elevation in febrile recipients during pre-transplant conditioning with anti-thymocyte globulin.

Infection is a major contributor to non-relapse mortality in allogeneic hematopoietic stem cell transplantation (allo-HSCT). Detecting infectious diseases in febrile patients during pretransplant conditioning is crucial for subsequent transplant success. Procalcitonin (PCT) is an auxiliary diagnostic marker of severe bacterial infections and has been proposed as a useful predictor of infection in patients undergoing allo-HSCT. Pre-transplant use of anti-thymocyte globulin (ATG) can cause side effects, such as fever and hypotension, which must be distinguished from infectious diseases. Although ATG administration may increase PCT levels, data on PCT levels in febrile patients after ATG administration are limited. Furthermore, no studies have compared PCT levels during allo-HSCT conditioning using ATG or non-ATG regimens. To investigate whether ATG increases PCT levels during febrile episodes in pre-transplant conditioning and whether PCT could be used to discriminate infections during this period, we analyzed 17 ATG and 59 non-ATG patients with fever and who underwent PCT level measurements during pre-transplant conditioning. Our findings revealed that ATG administration was the only significant factor that increased PCT positivity during fever (p = 0.01). In contrast, infectious diseases did not affect PCT positivity in the ATG group (p = 0.24). Furthermore, bloodstream infection was a significant risk factor for PCT positivity in patients who received non-ATG regimens (p < 0.01). Incorporating PCT levels into the diagnostic workup for infectious diseases requires careful consideration, particularly for patients receiving ATG regimens.

A case of hemophagocytic lymphohistiocytosis with a significant response to baricitinib: a first report with review of literature.

Hemophagocytic lymphohistiocytosis (HLH) is a febrile disease with hyperinflammation characterized by activated macrophages with phagocytosis. The treatment strategy of secondary HLH has not been clearly established. Because of the high mortality rate and poor prognosis of HLH, alternative treatment strategies have been sought in treatment-resistant cases. Recently, there have been several reports that ruxolitinib, a Janus kinase (JAK) 1/JAK2 inhibitor, was effective against secondary HLH. Since the pathogenesis of HLH involves the overproduction of cytokines and JAK transmits a variety of cytokine signals, JAK inhibitors are thought to be effective in HLH. We herein report a case of HLH that was refractory to glucocorticoids, cyclosporine, and etoposide but responded to baricitinib. In the field of rheumatology, treatment-resistant cases of secondary HLH remain unmet needs. This is the first report to show that baricitinib was effective in a case of HLH. The accumulation of more cases in the future may prove that baricitinib is a potent agent for treating HLH.

Risk factors for late cytomegalovirus infection after completing letermovir prophylaxis.

Prophylactic use of letermovir (LMV) markedly reduces the incidence of early clinically significant cytomegalovirus (csCMV) infection within the first 100 days after allogeneic hematopoietic cell transplantation (allo-HCT), which improves transplant outcomes. However, some patients eventually develop late-csCMV infection (beyond day 100) after completing LMV prophylaxis. To assess the incidence of late-csCMV infection as well as its risk factors and impacts on transplant outcome, a total of 81 allo-HCT recipients who had not developed early csCMV infection during LMV prophylaxis were retrospectively analyzed. Among them, 23 (28.4%) patients developed late-csCMV infection (until day 180) at a median time of 131 days after transplantation and 30 days after LMV discontinuation, respectively. Late-csCMV infection was correlated with apparent delayed immune reconstitution: patients transplanted from HLA-mismatched donors (hazard ratio [HR] = 13.0, p = 0.011) or CMV-IgG-negative donors (HR = 2.39, p = 0.043) had a significantly higher risk. In this study, transplant outcomes did not differ between patients with and without late-csCMV infection. This suggests a need to clarify the efficacy of extended administration of LMV for preventing late-csCMV infection in a larger number of allo-HCT recipients, especially those with "high-risk" donors.

Incidence of refractory cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation.

Post-transplant cytomegalovirus (CMV) disease can be almost completely avoided by current infection control procedures. However, CMV reactivation occurs in more than half of patients, and some patients can develop clinically resistant CMV infections. Whether resistance is due to the host's immune status or a viral resistance mutation is challenging to confirm. Therefore, a prospective observational analysis of refractory CMV infection was conducted in 199 consecutive patients who received allogeneic hematopoietic stem cell transplantation at a single institution. Among them, 143 (72%) patients received anti-CMV drugs due to CMV reactivation, and only 17 (8.5%) exhibited refractory CMV infection. These patients had clinically refractory infection. However, viral genome analysis revealed that only one patient exhibited a mutation associated with the anti-CMV drug resistance. Clinical resistance was mainly correlated with host immune factors, and the incidence of resistance caused by gene mutations was low at the early stage after a transplantation.

Efficacy of prophylactic letermovir for cytomegalovirus reactivation in hematopoietic cell transplantation: a multicenter real-world data.

A novel anti-cytomegalovirus (CMV) agent, letermovir (LMV), could reportedly improve the outcomes of allogeneic hematopoietic cell transplantation (allo-HCT) recipients because of its high potential to prevent CMV reactivation. Therefore, 685 Japanese allo-HCT recipients, of whom ~80% had a high risk of CMV reactivation, were retrospectively analyzed to assess the impacts of prophylactic LMV on the incidence of clinically significant CMV (csCMV) infection as well as their transplant outcome. By comparing 114 patients who received LMV prophylaxis for a median 92 days to 571 patients without prophylaxis, we observed that prophylactic LMV could significantly (1) reduce the 180-day cumulative incidence of csCMV infection (44.7 vs. 72.4%, p < 0.001), (2) delay the median time until initiation of CMV antigenemia-guided preemptive therapy (90 vs. 36 days, p < 0.001), (3) shorten the duration of anti-CMV preemptive treatment (21 vs. 25 days, p = 0.006), and (4) improve the overall survival rate at 180 days after transplant (80.4 vs. 73.0%, p = 0.033) with a trend of lower non-relapse mortality (8.9 vs. 14.9%, p = 0.052). Our findings demonstrate that prophylactic LMV treatment is highly effective in preventing the development of csCMV infection and ultimately reduces transplant-related mortality.

A human SIRPA knock-in xenograft mouse model to study human hematopoietic and cancer stem cells.

In human-to-mouse xenogeneic transplantation, polymorphisms of signal-regulatory protein α (SIRPA) that decide their binding affinity for human CD47 are critical for engraftment efficiency of human cells. In this study, we generated a new C57BL/6.Rag2nullIl2rgnull (BRG) mouse line with Sirpahuman/human (BRGShuman) mice, in which mouse Sirpa was replaced by human SIRPA encompassing all 8 exons. Macrophages from C57BL/6 mice harboring Sirpahuman/human had a significantly stronger affinity for human CD47 than those harboring SirpaNOD/NOD and did not show detectable phagocytosis against human hematopoietic stem cells. In turn, Sirpahuman/human macrophages had a moderate affinity for mouse CD47, and BRGShuman mice did not exhibit the blood cytopenia that was seen in Sirpa-/- mice. In human to mouse xenograft experiments, BRGShuman mice showed significantly greater engraftment and maintenance of human hematopoiesis with a high level of myeloid reconstitution, as well as improved reconstitution in peripheral tissues, compared with BRG mice harboring SirpaNOD/NOD (BRGSNOD). BRGShuman mice also showed significantly enhanced engraftment and growth of acute myeloid leukemia and subcutaneously transplanted human colon cancer cells compared with BRGSNOD mice. BRGShuman mice should be a useful basic line for establishing a more authentic xenotransplantation model to study normal and malignant human stem cells.

Expansion of NKG2C-expressing Natural Killer Cells after Umbilical Cord Blood Transplantation in a Patient with Peripheral T-cell Lymphoma with Cytotoxic Molecules.

A 64-year-old woman presented with generalized lymphadenopathy and systemic manifestations. The examination of a biopsy specimen revealed peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) expressing cytotoxic molecules. Umbilical cord blood transplantation was successful during a partial remission state after the administration of salvage chemotherapy. The donor-derived large granular lymphocytes started to increase as a result of cytomegalovirus reactivation. The fraction of natural killer (NK) cells expressing the NKG2C molecule accounted for one-third of the total lymphocytes for almost two years. We implicitly indicate the association between the persistence of donor-derived NKG2C+ NK cell-expansion and maintaining a complete remission in similar cases of aggressive PTCL-NOS.

Enhanced Reconstitution of Human Erythropoiesis and Thrombopoiesis in an Immunodeficient Mouse Model with Kit(Wv) Mutations.

In human-to-mouse xenograft models, reconstitution of human hematopoiesis is usually B-lymphoid dominant. Here we show that the introduction of homozygous Kit(Wv) mutations into C57BL/6.Rag2(null)Il2rg(null) mice with NOD-Sirpa (BRGS) strongly promoted human multi-lineage reconstitution. After xenotransplantation of human CD34(+)CD38(-) cord blood cells, these newly generated C57BL/6.Rag2(null)Il2rg(null)NOD-Sirpa Kit(Wv/Wv) (BRGSK(Wv/Wv)) mice showed significantly higher levels of human cell chimerism and long-term multi-lineage reconstitution compared with BRGS mice. Strikingly, this mouse displayed a robust reconstitution of human erythropoiesis and thrombopoiesis with terminal maturation in the bone marrow. Furthermore, depletion of host macrophages by clodronate administration resulted in the presence of human erythrocytes and platelets in the circulation. Thus, attenuation of mouse KIT signaling greatly enhances the multi-lineage differentiation of human hematopoietic stem and progenitor cells (HSPCs) in mouse bone marrow, presumably by outcompeting mouse HSPCs to occupy suitable microenvironments. The BRGSK(Wv/Wv) mouse model is a useful tool to study human multi-lineage hematopoiesis.

Calreticulin mutation does not contribute to disease progression in essential thrombocythemia by inhibiting phagocytosis.

Somatic mutations of calreticulin (CALR) have been observed in many cases of essential thrombocythemia (ET) or primary myelofibrosis that harbor non-mutated Janus kinase 2 (JAK2). CALR mainly localizes within the endoplasmic reticulum lumen, but a small fraction of the total CALR pool is distributed over the cell surface. Cell surface CALR is known to transduce prophagocytic "eat me" signals to macrophages and acts as one of the important regulators for macrophage engulfment. In this study, we attempted to clarify whether mutant CALR may affect the threshold for macrophage engulfment and play an integral role in the pathogenesis of CALR-mutated ET. First, we compared the surface expression levels of CALR on hematopoietic stem and progenitor cells (HSPCs) and mature blood cells in patients with myeloproliferative neoplasms and found that the surface expression of mutant CALR did not change. Next, we compared the threshold for macrophage phagocytosis of each HSPC fraction and mature blood cells and found no significant change in the efficiency of macrophage engulfment. Our data suggest that CALR mutation does not affect sensitivity to phagocytosis by macrophages. Finally, we analyzed the phosphorylation statuses of molecules downstream of JAK2 at each HSPC level in patients with ET and found that CALR mutations activated the JAK-STAT pathway in a manner similar to that associated with JAK2 mutations. These results indicate that mutant CALR causes myeloproliferation because of the activation of JAK-STAT pathway and not by the inhibition of phagocytosis, which is similar to the myeloproliferation caused by JAK2 V617F mutation.

A human lung carcinoma cell line supports efficient measles virus growth and syncytium formation via a SLAM- and CD46-independent mechanism.

Measles virus (MV) propagates mainly in lymphoid organs throughout the body and produces syncytia by using signaling lymphocyte activation molecule (SLAM) as a receptor. MV also spreads in SLAM-negative epithelial tissues by unknown mechanisms. Ubiquitously expressed CD46 functions as another receptor for vaccine strains of MV but not for wild-type strains. We here show that MV grows and produces syncytia efficiently in a human lung adenocarcinoma cell line via a SLAM- and CD46-independent mechanism using a novel receptor-binding site on the hemagglutinin protein. This infection model could advance our understanding of MV infection of SLAM-negative epithelial cells and tissues.