Human herpesvirus-6 encephalitis after allogeneic hematopoietic cell transplantation: What we do and do not know

Risk factors and long-term outcomes for human herpesvirus 6 encephalitis in the early period after allogeneic stem cell transplantation

Human herpesvirus 6 (HHV6) encephalitis is a rare but life-threatening complication for patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, reports on susceptibility factors and clinical outcomes are limited. We enrolled HHV6 encephalitis patients following allo-HSCT between 2018 and 2022, then conducted a 1:4 nested case-control cohort study to evaluate risk factors and long-term outcomes. Among 1350 patients, 20 (1.48%) developed HHV6 encephalitis, with a median onset time of 25.5 days after HSCT. Patient age<30 (odds ratio [OR], 3.24, P = 0.016) and NK cell count<115/ul at 21 days (OR, 6.07, P = 0.018) were identified as independent risk factors in multivariate analysis. Moreover, the HHV6 encephalitis group was significantly associated with higher incidence of grade II-IV graft-versus-host disease (aGVHD) (hazard ratio [HR], 5.52, P < 0.001) and transplant-associated microangiopathy (HR,9.86, P < 0.001), and demonstrated a significantly higher non-relapse mortality (NRM) (HR, 5.28, P = 0.004) and a lower overall survival (HR, 4.34, P = 0.001) or progression-free survival (HR, 3.94, P = 0.001) compared to control group. In conclusion, patients <30 years old or with delayed NK cell recovery are more susceptible to HHV6 encephalitis after allo-HSCT, and patients with HHV6 encephalitis after transplantation have poorer clinical outcomes.

International recommendations for screening and preventative practices for long-term survivors of transplantation and cellular therapy: a 2023 update

As hematopoietic cell transplantation (HCT) and cellular therapy expand to new indications and international access improves, the volume of HCT performed annually continues to rise. Parallel improvements in HCT techniques and supportive care entails more patients surviving long-term, creating further emphasis on survivorship needs. Survivors are at risk for developing late complications secondary to pre-, peri- and post-transplant exposures and other underlying risk-factors. Guidelines for screening and preventive practices for HCT survivors were originally published in 2006 and updated in 2012. To review contemporary literature and update the recommendations while considering the changing practice of HCT and cellular therapy, an international group of experts was again convened. This review provides updated pediatric and adult survivorship guidelines for HCT and cellular therapy. The contributory role of chronic graft-versus-host disease (cGVHD) to the development of late effects is discussed but cGVHD management is not covered in detail. These guidelines emphasize special needs of patients with distinct underlying HCT indications or comorbidities (e.g., hemoglobinopathies, older adults) but do not replace more detailed group, disease, or condition specific guidelines. Although these recommendations should be applicable to the vast majority of HCT recipients, resource constraints may limit their implementation in some settings.

International Recommendations for Screening and Preventative Practices for Long-Term Survivors of Transplantation and Cellular Therapy: A 2023 Update

As hematopoietic cell transplantation (HCT) and cellular therapy expand to new indications and international access improves, the number of HCTs performed annually continues to rise. Parallel improvements in HCT techniques and supportive care entails more patients surviving long term, creating further emphasis on survivorship needs. Survivors are at risk for developing late complications secondary to pretransplantation, peritransplantation, and post-transplantation exposures and other underlying risk factors. Guidelines for screening and preventive practices for HCT survivors were originally published in 2006 and then updated in 2012. An international group of experts was convened to review the contemporary literature and update the recommendations while considering the changing practices of HCT and cellular therapy. This review provides updated pediatric and adult survivorship guidelines for HCT and cellular therapy. The contributory role of chronic graft-versus-host disease (cGVHD) to the development of late effects is discussed, but cGVHD management is not covered in detail. These guidelines emphasize the special needs of patients with distinct underlying HCT indications or comorbidities (eg, hemoglobinopathies, older adults) but do not replace more detailed group-, disease-, or condition-specific guidelines. Although these recommendations should be applicable to the vast majority of HCT recipients, resource constraints may limit their implementation in some settings.

Case report: Acute HHV6B encephalitis/myelitis post CAR-T cell therapy in patients with relapsed/refractory aggressive B-cell lymphoma

Background

The development of chimeric antigen receptor (CAR)-T cell therapy has revolutionized treatment outcomes in patients with lymphoid malignancies. However, several studies have reported a relatively high rate of infection in adult patients following CD19-targeting CAR T-cell therapy, particularly in the first 28 days. Notably, acute human herpesvirus 6 B (HHV6B) reactivation occurs in up to two-thirds of allogeneic hematopoietic stem cell transplantation patients.

Case presentations

Herein, we describe a report of HHV6B encephalitis/myelitis in three patients with relapsed/refractory diffuse large B-cell lymphoma post CAR T-cell therapy. All three patients received multiple lines of prior treatment (range: 2-9 lines). All patients presented with fever that persisted for at least 2 weeks after CAR-T cell infusion (CTI). Both the onset time and duration were similar to those of the cytokine release syndrome (CRS); nevertheless, the CRS grades of the patients were low (grade 1 or 2). Delirium and memory loss after CTI were the earliest notable mental presentations. Neurological manifestations progressed rapidly, with patients experiencing varying degrees of impaired consciousness, seizures, and coma. Back pain, lumbago, lower limb weakness and uroschesis were also observed in Patient 3, indicating myelitis. High HHV6B loads were detected in all Cerebral spinal fluid (CSF) samples using metagenomic next-generation sequencing (mNGS). Only one patient required high-activity antivirals and IgG intravenous pulse treatment finally recovered, whereas the other two patients died from HHV6B encephalitis.

Conclusion

Considering its fatal potential, HHV6B encephalitis/myelitis should be urgently diagnosed post CAR-T cell-based therapy. Furthermore, hematologists should differentially diagnose these conditions from CRS or other immunotherapy-related neurotoxicities as early as possible. The results of this study demonstrate the potential of mNGS in the early diagnosis of HHV6B infection, particularly when the organism is difficult to culture.

Seizures in children undergoing stem cell transplantation

BACKGROUND

Neurological complications (NCs) are of major concern following hematological stem cell transplantation (HSCT), most of which present with seizures.

PROCEDURES

We performed a retrospective study (2002-2018) of patients undergoing HSCT in order to analyze the incidence and aetiologies related to seizures.

RESULTS

Of 155 children undergoing HSCT, 27 (17.4%) developed seizures at some point in 2 years of follow-up. The most frequent etiologies were central nervous system (CNS) infection (n = 10), drug toxicity (n = 8), and vascular disease (n = 5). A statistically significant association was found between seizure and the HSCT type (lower risk for a related identical donor, p = .010), prophylactic or therapeutic mycophenolate use (p = .043 and .046, respectively), steroid use (p = .023), selective CD45RA+ depletion (p = .002), pre-engraftment syndrome (p = .007), and chronic graft-versus-host disease (GVHD) severity (p = .030). Seizures predicted evolution to life-threatening complications and admission to intensive care (p < .001) and higher mortality (p = .023). A statistically significant association was also found between seizures and sequelae in survivors (p = .029). Children who developed seizures had a higher risk of CNS infection and vascular disease (odds ratio 37.25 [95% CI: 7.45-186.05] and 12.95 [95% CI 2.24-74.80], respectively).

CONCLUSIONS

Neurological complications highly impact survival and outcomes and need to be addressed when facing an HSCT procedure.

How to improve the outcomes of elderly acute myeloid leukemia patients through allogeneic hematopoietic stem cell transplantation

In recent years, with the gradual advancement of haploidentical transplantation technology, the availability of donors has increased significantly, along with the widespread use of reduced-intensity conditioning and the improvement of nursing techniques, giving more elderly acute myeloid leukemia (AML) patients the chance to receive allogeneic hematopoietic stem cell transplantation. We have summarized the classic and recently proposed pre-transplant assessment methods and assessed the various sources of donors, conditioning regimens, and post-transplant complication management based on the outcomes of large-scale clinical studies for elderly AML patients.

Differentiating central nervous system infection from disease infiltration in hematological malignancy

Hematological malignancies place individuals at risk of CNS involvement from their hematological disease and opportunistic intracranial infection secondary to disease-/treatment-associated immunosuppression. Differentiating CNS infection from hematological disease infiltration in these patients is valuable but often challenging. We sought to determine if statistical models might aid discrimination between these processes. Neuroradiology, clinical and laboratory data for patients with hematological malignancy at our institution between 2007 and 2017 were retrieved. MRI were deep-phenotyped across anatomical distribution, presence of pathological enhancement, diffusion restriction and hemorrhage and statistically modelled with Bayesian-directed probability networks and multivariate logistic regression. 109 patients were studied. Irrespective of a diagnosis of CNS infection or hematological disease, the commonest anatomical distributions of abnormality were multifocal-parenchymal (34.9%), focal-parenchymal (29.4%) and leptomeningeal (11.9%). Pathological enhancement was the most frequently observed abnormality (46.8%), followed by hemorrhage (22.9%) and restricted diffusion (19.3%). Logistic regression could differentiate CNS infection from hematological disease infiltration with an AUC of 0.85 where, with OR > 1 favoring CNS infection and < 1 favoring CNS hematological disease, significantly predictive imaging features were hemorrhage (OR 24.61, p = 0.02), pathological enhancement (OR 0.17, p = 0.04) and an extra-axial location (OR 0.06, p = 0.05). In conclusion, CNS infection and hematological disease are heterogeneous entities with overlapping radiological appearances but a multivariate interaction of MR imaging features may assist in distinguishing them.

Human seminal virome: a panel based on recent literature

Background

The seminal virome and its implications for fertility remain poorly understood. To date, there are no defined panels for the detection of viruses of clinical interest in seminal samples.

Results

In this study, we characterized the human seminal virome based on more than 1,000 studies published over the last five years.

Conclusions

The number of studies investigating viruses that occur in human semen has increased, and to date, these studies have been mostly prospective or related to specific clinical findings. Through the joint analysis of all these studies, we have listed the viruses related to the worsening of seminal parameters and propose a new panel with the main viruses already described that possibly affect male fertility and health. This panel can assist in evaluating semen quality and serve as a tool for investigation in cases of infertility.

Clinical and microbiological characteristics of bacterial meningitis in umbilical cord blood transplantation recipients

Bacterial meningitis is a rare but severe infectious complication after hematopoietic stem cell transplantation. However, its clinical features were previously not clear. We reviewed the cases of 7 patients diagnosed with bacterial meningitis with a positive cerebrospinal fluid culture among 1147 patients who underwent cord blood transplantation (CBT) at our institution between September 2007 and September 2020. The diagnosis was made on day + 5- + 45, and 5 patients developed bacterial meningitis before neutrophil engraftment. The causative organisms were all Gram-positive cocci: Enterococcus faecium and Enterococcus gallinarum (2 patients each), and Staphylococcus haemolyticus, Streptococcus mitis/oralis, and Rothia mucilaginosa (1 patient each). Six patients developed bacterial meningitis secondary to prior or concomitant bacteremia caused by the same bacterium. Five patients had received anti-MRSA agents at onset: vancomycin in 3, teicoplanin in 1, and daptomycin in 1. After diagnosis of bacterial meningitis, linezolid was eventually used for 6 patients. Two patients with E. gallinarum were alive at day + 1380 and + 157 after CBT, respectively, whereas 5 patients died 17-53 (median 43) days after the onset of bacterial meningitis. Breakthrough meningitis in CBT can occur even during the use of anti-MRSA drugs, and intensive antibiotic treatment is necessary.

Neurologic Complications in Pediatric Allogeneic Stem Cell Transplantation: Analysis of Risk Factors and Outcome

Neurologic complications following stem cell transplantation are of utmost importance owing to their high morbimortality. Although many studies have been performed in the adult population, reports in children are scarce. Our objective was to determine the most common neurologic complications in a pediatric population and to analyze possible risk factors for their development. We performed an exploratory retrospective study of neurologic complications in pediatric patients who had allogeneic stem cell transplantation over the last 18 years. We identified 66 neurologic complications in 178 allogeneic stem cell transplantations. The most frequent neurologic complications were those involving the peripheral nervous system and those related to drug toxicity. Survival decreased significantly in the presence of neurologic complications. Multivariate logistic regression analysis showed that independent risk factors for developing neurologic complications were development of chronic extensive graft-vs-host disease requiring treatment, cytomegalovirus reactivation, and central nervous system radiation. Prompt diagnosis and preemptive treatment, if possible, are necessary to avoid long-term sequelae or mortality.

Human Herpesvirus 6 Reactivation Associated With Intestinal Pseudo-Obstruction in a Renal Transplant Recipient

Human herpesvirus 6 infection is common after organ transplant. Generally, infection is asymptomatic or is associated with a mild illness. However, human herpesvirus 6 infection in these patients may as well be life threatening as a result of severe end-stage organ disease. Here, we have reported a case of a severe human herpesvirus 6 infection with cerebral, hepatic, and gastrointestinal involvement, which presented as intestinal pseudo-obstruction. The patient was a renal transplant recipient who was successfully treated with ganciclovir. We also reviewed the literature on human herpesvirus 6 diagnosis and the associated colitis and encephalitis with its infection in solid-organ transplant recipients.

Post-Transplantation Cyclophosphamide Is Associated with an Increase in Non-Cytomegalovirus Herpesvirus Infections in Patients with Acute Leukemia and Myelodysplastic Syndrome

The use of post-transplantation cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis in recipients of haploidentical and fully matched transplantations is on the increase. Published studies have reported an increased incidence of cytomegalovirus (CMV) infection with the use of PTCy. Limited data exist on the incidence and outcomes of infection with non-CMV herpesviruses (NCHV) in this setting. The aim of this study was to evaluate the cumulative incidence of NCHV infections and the association of NCHV infections with transplantation-specific outcomes in recipients of haploidentical transplantation with PTCy (HaploCy), matched sibling donor transplantation with PTCy (SibCy), and matched sibling donor transplantation with calcineurin inhibitor-based prophylaxis (SibCNI). We hypothesized that, like CMV infection, HaploCy recipients of also will have a higher risk of NCHV infections. Using the Center for International Blood and Marrow Transplantation Research database, we analyzed 2765 patients (HaploCy, n = 757; SibCNI, n = 1605; SibCy, n = 403) who had undergone their first hematopoietic stem cell transplantation (HCT) between 2012 and 2017 for acute myelogenous leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome. The cumulative incidence of NCHV at 6 months post-NCT was 13.9% (99% confidence interval], 10.8% to 17.3%) in the HaploCy group, 10.7% (99% CI, 7.1% to 15%) in the SibCy group, and 5.7% (99% CI, 4.3% to 7.3%) in the Sib CNI group (P < .001). This was due primarily to a higher frequency of human herpesvirus 6 viremia reported in patients receiving PTCy. The incidence of Epstein-Barr viremia was low in all groups, and no cases of post-transplantation lymphoproliferative disorder were seen in either PTCy group. The incidence of NCHV organ disease was low in all 3 cohorts. The development of NCHV infection was associated with increased treatment-related mortality, particularly in the HaploCy group. There was no association with the development of GVHD, relapse, or disease-free survival. Patients in PTCy cohorts who did not develop NCHV infection had lower rates of cGVHD. This study demonstrates that the use of PTCy is associated with an increased risk of NCHV infection. The development of NCHV infection was associated with increased nonrelapse mortality, especially in the HaploCy group. Prospective trials should consider viral surveillance strategies in conjunction with assessment of immune reconstitution for a better understanding of the clinical relevance of viral reactivation in different HCT settings.

Unique Challenges to Diagnosing Human Herpesvirus-6 (HHV-6) Encephalitis Following Post-Hematopoietic Stem Cell Transplant: A Case and Brief Review

A patient with an ultimate diagnosis of human herpesvirus-6 (HHV-6) encephalitis developed central nervous system (CNS) symptoms 13 days after undergoing myeloablative haploidentical allogeneic hematopoietic stem cell transplant (HSCT). Due to the patient's body habitus, magnetic resonance (MR) imaging was not obtained until the onset of retrograde amnesia on day +24. MR imaging and other clinical findings eliminated all skepticism of HHV-6 encephalitis and HHV-6 antivirals were initiated on day +28, leading to gradual recovery. This case demonstrates some of the factors that may complicate the diagnosis of post-alloHSCT HHV-6 encephalitis. Because HHV-6 encephalitis and viremia can occur without warning, a single negative study should not exclude future development, especially if CNS symptoms are present. Acute graft-versus-host disease and cord blood transplantation are both significant risk factors for HHV-6 encephalitis. Human leukocyte antigen (HLA) mismatch, engraftment complications, or certain HLA alleles have also been associated with HHV-6 encephalitis. Chromosomally integrated HHV-6 must also be ruled out to prevent inappropriate and potentially harmful administration of antivirals. Due to the severe short- and long-term sequelae of HHV-6 encephalitis, appropriate treatment should be administered as soon as possible.

Approach to Neurologic Complications in the Immunocompromised Patient

Neurologic complications are common in immunocompromised patients, including those with advanced human immunodeficiency virus, transplant recipients, and patients on immunomodulatory medications. In addition to the standard differential diagnosis, specific pathogens and other conditions unique to the immunocompromised state should be considered in the evaluation of neurologic complaints in this patient population. A thorough understanding of these considerations is critical to the inpatient neurologist in contemporary practice, as increasing numbers of patients are exposed to immunomodulatory therapies. In this review, we provide a chief complaint-based approach to the clinical presentations and diagnosis of both infectious and noninfectious complications particular to immunocompromised patients.

Acute Graft-Versus-Host Disease, Infections, Vascular Events and Drug Toxicities Affecting the Central Nervous System

Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative therapy for patients with hematological malignancies. Acute Graft versus host diseases (GVHD) is a major immune mediated side effect of allo-HCT that can affect the central nervous system (CNS) in addition to post-allo-HCT vascular events, drug toxicity or infections. Here we summarize and discuss recent preclinical data on the CNS as a target of acute GVHD and the known mechanisms contributing to neurotoxicity with a focus on microglia and T cells. We also discuss open questions in the field and place the findings made in mouse models in a clinical context. While in mice the neurological deficits can be assessed in a controlled fashion, in patients the etiology of the CNS damage is difficult to attribute to acute GVHD versus infections, vascular events, and drug-induced toxicity. Ultimately, we discuss novel therapies for GVHD of the CNS. Our understanding of the biological mechanisms that lead to neurotoxicity after allo-HCT increased over the last decade. This review provides insights into CNS manifestations of GVHD versus other etiologies of CNS damage in mice and patients.

Human herpesvirus 6A U27 plays an essential role for the virus propagation

Human herpesvirus 6A (HHV-6A) is a member of the genus Roseolovirus and the subfamily Betaherpesvirinae. It is similar to and human cytomegalovirus (HCMV). HHV-6A encodes a 41 kDa nuclear phosphoprotein, U27, which acts as a processivity factor in the replication of the viral DNA. HHV-6A U27 has 43% amino acid sequence homology with HCMV UL44, which is important for DNA replication. A previous study on HHV-6A U27 revealed that it greatly increases the in vitro DNA synthesis activity of HHV-6A DNA polymerase. However, the role of U27 during the HHV-6A virus replication process remains unclear. In this study, we constructed a U27-deficient HHV-6A mutant (HHV-6ABACU27mut) with a frameshift insertion at the U27 gene using an HHV-6A bacterial artificial chromosome (BAC) system. Viral reconstitution from the mutant BAC DNA was not detected, in contrast to the wild type and the revertant from the U27 mutant. This suggests that U27 plays a critical role in the life cycle of HHV-6A.

Post-allogeneic hematopoietic stem cell transplantation viral reactivations and viremias: a focused review on human herpesvirus-6, BK virus and adenovirus

Human cytomegalovirus and Epstein-Barr virus have been recognized as potential drivers of morbidity and mortality of patients undergoing allogeneic stem cell transplantation for years. Specific protocols for monitoring, prophylaxis and pre-emptive therapy are in place in many transplant settings. In this review, we focus on the next three most frequent viruses, human herpesvirus-6, BK virus and adenovirus, causing reactivation and/or viremia after allogeneic transplant, which are increasingly detected in patients in the post-transplant period owing to emerging techniques of molecular biology, recipients' characteristics, treatment modalities used for conditioning and factors related donors or stem cell source. Given the less frequent detection of an illness related to these viruses, there are often no specific protocols in place for the management of affected patients. While some patients develop significant morbidity (generally older), others may not need therapy at all (generally younger or children). Furthermore, some of the antiviral therapies used are potentially toxic. With the addition of increased risk of secondary infections, risk of graft failure or increased risk of graft-versus-host disease as well as the relationship with other post-transplant complications, the outcomes of patients with these viremias remain unsatisfactory and even long-term survivors experience increased morbidity.

Aseptic Meningitis after Recovery from SARS-CoV-2 in an Allogeneic Stem Cell Transplant Recipient

SARS-CoV-2 emerged as a worldwide pandemic in late 2019 and initially was described as a primary respiratory illness. The clinical manifestations of COVID-19 are now known to encompass nearly all organ systems, including the central nervous system. We present a case of an allogeneic hematopoietic stem cell transplant recipient who recovered from documented SARS-CoV-2 infection and later presented with symptoms of meningitis. While cerebrospinal fluid analysis did not reveal any bacterial or viral etiologies, evidence of an inflammatory state, including ophthalmologic findings of episcleritis, indicate what is likely the first reported case of aseptic meningitis associated with SARS-CoV-2 infection after initial clinical recovery.

Hippocampal Atrophy in Pediatric Transplant Recipients with Human Herpesvirus 6B

The aim of this study was to determine whether human herpesvirus 6B (HHV-6B) infection can impair the hippocampus in pediatric hematopoietic stem cell transplant (HSCT) recipients. Study subjects were pediatric HSCT recipients monitored for HHV-6B infection who underwent brain MRI before and after transplantation. Volumetric analysis of the hippocampus was performed. Of the 107 patients that received HSCT at Nagoya University Hospital Between July 2008 and April 2014, 20 were eligible for volumetric analysis. Eight patients had HHV-6B infection, of whom two had encephalopathy at the time of HHV-6B infection. None of the 12 patients without HHV-6B infection had encephalopathy. The median ratio of the right hippocampal volume from before to after transplantation was 0.93 in patients with HHV-6B infection and 1.02 in without HHV-6B infection (p = 0.007). The median ratio of the left hippocampal volume ratio in patients with and without HHV-6B infection was 0.92 and 1.00, respectively (p = 0.003). Among the eight patients with HHV-6B infection, four had a marked reduction in hippocampal volume (volume ratio < 0.90). Only one of these patients had neurological symptoms at the time of HHV-6B infection. The reduction in the hippocampal volume ratio was higher in pediatric HSCT recipients with HHV-6B infection than those without viral infection. Neurological follow-up may be required for pediatric HSCT recipients with HHV-6B infection.

The role of early natural killer cell adoptive infusion before engraftment in protecting against human herpesvirus-6B encephalitis after naïve T-cell-depleted allogeneic stem cell transplantation

BACKGROUND

Naïve T-cell-depleted grafts have been employed as an ex vivo T-cell depletion (TCD) platform to prevent graft-versus-host disease (GvHD) and improve immune reconstitution by providing rapid donor memory T-cell reconstitution after allogenic hematopoietic stem cell transplantation (allo-HSCT). CD45RA^- memory T cells confer protection against viruses such as cytomegalovirus, Epstein-Barr virus, and adenovirus; however, reports have shown an unexpectedly high incidence of human herpesvirus (HHV)-6B encephalitis among pediatric allo-HSCT patients.

METHODS

We report the first 18 consecutive allo-HSCT, 16 haplo-HSCT, and two human leukocyte antigen-matched related donors implanted with naïve TCD grafts. All donors were administered three cell products: first, a CD34⁺ stem cell product; second, a CD45RA⁺ TCD graft, followed by an adoptive natural killer (NK) cell infusion within 10 days after HSCT. The study's primary endpoint was the incidence of HHV-6B encephalitis.

RESULTS

Engraftment was achieved in 94.5% of cases; 2-year overall survival, event-free survival, and GvHD/relapse-free survival were 87.2% (95% CI 78.6-95.8), 67.3% (95% CI 53.1-81.5), and 64% (95% CI 50.5-78.1), respectively. HHV-6B reactivation occurred in 7 of the haplo-HSCT patients, six of who received a cell infusion with an NK/CD4 ratio <2. None of the patients developed encephalitis.

CONCLUSIONS

In this clinical study, we show that early adoptive NK cell infusion after a 45RA⁺ TCD allo-HSCT graft is safe and can prevent HHV-6B encephalitis. We recommend infusing adoptive NK cells after allo-HSCT using CD45RA⁺ TCD grafts.

Effect of methotrexate dose in graft-versus-host disease prophylaxis after single-unit cord blood transplantation in adult acute myeloid leukemia

To investigate the association between methotrexate (MTX) dosage and engraftment, graft-versus-host disease (GVHD) incidence, and survival in umbilical cord blood transplantation (UCBT), we compared transplant outcomes after UCBT with various GVHD prophylaxis regimens, using registry data with additional data collection. Patients transplanted for acute myeloid leukemia with a calcineurin inhibitor (CNI) and either MTX or mycophenolate mofetil (MMF) combination were selected. In total, 888 single-unit UCBTs (MTX_15-10-10, 415; MTX_10-7-7, 294; MTX_5-5-5, 71; MMF, 108) were included. In multivariate analyses with MTX_15-10-10 as the reference, the likelihood of neutrophil and platelet engraftment was significantly worse in the MTX_10-7-7 group, and similarly better in MMF group compared with MTX_15-10-10. All variables including CyA vs Tac and 4-group GVHD prophylaxis became significant for the risk of grade II-IV acute GVHD in the final multivariate model. We observed significant additional effects of combined MTX dose in the Tac group, which were larger with lower MTX dose and MMF. No significant difference was observed in survival risk among GVHD prophylaxis groups. Despite the potential background differences in the combined CNI and conditioning regimen, we conclude that the recommended GVHD prophylaxis is a combination of CyA plus MTX_15-10-10 or Tac plus MMF.

Neuroimaging of CNS infection in haematological malignancy: important signs and common diagnostic pitfalls

Patients with haematological malignancy are at increased risk of developing central nervous system (CNS) infections, which are associated with significant morbidity and mortality. Neuroimaging plays a pivotal role in the diagnostic pathway of these patients; however, layers of complexity are added to image interpretation by the heterogeneity in imaging manifestations of haematological malignancies in the CNS, overlapping imaging features of CNS infection, treatment-related parenchymal changes and the presence of intracranial comorbidity. In this article, we review important intracranial findings of CNS infection cases accrued in 1,855 studies over more than a decade at a specialist tertiary centre. We offer schema to identify common and important neuroimaging features, discuss key differential diagnoses and frequent diagnostic pitfalls.

Human herpesvirus 6 reactivation in unmanipulated haploidentical hematopoietic stem cell transplantation predicts the occurrence of grade II to IV acute graft-versus-host disease

BACKGROUND

Human herpesvirus 6 (HHV-6) reactivation is relatively common after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the incidence of HHV-6 reactivation and the clinical outcomes following unmanipulated haploidentical HSCT (haplo-HSCT) remain unknown.

METHOD

We prospectively monitored blood HHV-6 DNA using real-time quantitative polymerase chain reaction weekly until day 100 post unmanipulated haplo-HSCT in patients with hematological malignancies.

RESULTS

From November 2016 to March 2017, 102 patients (58 male and 44 female, median age 25(2-58) years old) were enrolled. Within 100 days post-transplantation, 27 patients (27/136, 19.9%) developed HHV-6 viremia with a median onset time of 14 (7-98) days. The cumulative incidence of HHV-6 reactivation on day 100 post-HSCT was 25.5 ± 4.3% in haplo-HSCT. The median HHV-6 copy number was 1.45 × 10³ (5.48 × 10² -2.00 × 10⁴ ) copies/ml. The HHV-6 viremia duration time was 7 days in 23 patients, 14 days in one patient and 21 days in one patient. In multivariate analysis, prior HHV-6 reactivation was an independent risk factor for grade 2-4 graft-versus-host disease (GVHD). But it did not influence the overall survival (OS)(HR 1.624, 95%CI 0.768-3.432, P = .204), disease-free survival (DFS) (HR 1.640, 95%CI 0.799-3.367, P = .177) and non-relapse mortality (NRM) (HR 1.644, 95%CI 0.670-4.038, P = .278).

CONCLUSION

The reactivation of HHV-6 after unmanipulated haploidentical transplantation predicts the occurrence of grade 2-4 a-GVHD, but it may not influence the overall survival (OS), disease-free survival (DFS) and non-relapse mortality (NRM).

Clinical, radiological, and electroencephalographic features of HHV-6 encephalitis following hematopoietic stem cell transplantation

Background

To study the clinical, radiological, electroencephalographic, and cerebrospinal fluid (CSF) features of Human Herpes Virus 6 (HHV-6) encephalitis in leukemia patients underwent allogeneic hematopoietic stem cell transplantation (HSCT).

Methods

We retrospectively reviewed all leukemia patients who underwent allogeneic HSCT between January 2010 and December 2018. The clinical, radiological, electroencephalographic, and CSF features of those with HHV6 encephalitis were recorded.

Results

A total of five cases of HHV6 encephalitis were identified. Three patients had Chronic Myelogenous Leukemia, one had Chronic Lymphocytic Leukemia and one had Acute Lymphoblastic Leukemia. All of them presented a few months after transplantation with altered mental status. Comorbidities included pancytopenia, sepsis, graft versus host disease, and multi-organ failure. EEG showed focal seizures originating from temporal lobes in two patients, generalized or focal periodic discharges in three patients, focal slowing in two patients, and diffuse slowing in three patients. MRI brain showed T2/FLAIR hyper-intensities in four patients; two of them in bilateral temporal lobes, one in the thalamus/hypothalamus/brainstem/cerebellum/basal ganglia, and one in the periventricular areas. CSF showed pleocytosis, high protein, and positive HHV-6 PCR. Foscarnet was used as an anti-viral agent. Anti-epileptics used were phenytoin, levetiracetam, and valproic acid. Four patients died in a few months, whereas one recovered completely.

Conclusions

HHV-6 encephalitis can add significant morbidity and mortality to leukemic patients following allogeneic HSCT. Patients present with typical clinical features of encephalitis. Salient EEG characteristics include periodic discharges or overt temporal lobe seizures. MRI findings are T2/FLAIR signal hyperintensities, mainly in the temporal lobes.

Comprehensive Screening of Mouse T-Cell Epitopes in Human Herpesvirus 6B Glycoprotein H/L/Q1/Q2 Tetramer Complex

Human herpesvirus 6 (HHV-6) infects over 90% of people. The HHV-6 subtype, HHV-6B in particular, is often associated with exanthem subitum in early childhood. Exanthem subitum is usually self-limiting and good prognosis disease; however, some infants primarily infected with HHV-6B develop encephalitis/encephalopathy, and half of the patients developed encephalopathy reported to have neurological sequelae. Furthermore, after primary infection, HHV-6B remains in a latent state and sometimes reactivated in immunosuppressed patients, causing life-threatening severe encephalopathy. However, effective immunotherapies or vaccines for controlling HHV-6B infection and reactivation have not yet been established. Recently, we have found that the HHV-6B tetrameric glycoprotein (g) complex, gH/gL/gQ1/gQ2 is a promising vaccine candidate, and currently under preclinical development. To confirm our vaccine candidate protein complex induce detectable T-cell responses, in this study, we comprehensively screened CD4⁺ and CD8⁺ T-cell epitopes in the gH/gL/gQ1/gQ2 tetrameric complex protein in mice immunisation model. Both BALB/c and C57BL/6 mice were immunised with the tetrameric complex protein or plasmid DNA encoding gH, gL, gQ1, and gQ2, and then restimulated with 162 20-mer peptides covering the whole gH/gL/gQ1/gQ2 sequences; multiple CD4⁺ and CD8⁺ T-cell-stimulating peptides were identified in both BALB/c and C57BL/6 mice. Our study demonstrates that gH/gL/gQ1/gQ2 tetramer-targeted vaccination has potential to induce T-cell responses in two different strains of mice and supports the future development and application of T-cell-inducing vaccine and immunotherapies against HHV-6B.

Structural basis for the interaction of human herpesvirus 6B tetrameric glycoprotein complex with the cellular receptor, human CD134

A unique glycoprotein is expressed on the virus envelope of human herpesvirus 6B (HHV-6B): the complex gH/gL/gQ1/gQ2 (hereafter referred to as the HHV-6B tetramer). This tetramer recognizes a host receptor expressed on activated T cells: human CD134 (hCD134). This interaction is essential for HHV-6B entry into the susceptible cells and is a determinant for HHV-6B cell tropism. The structural mechanisms underlying this unique interaction were unknown. Herein we solved the interactions between the HHV-6B tetramer and the receptor by using their neutralizing antibodies in molecular and structural analyses. A surface plasmon resonance analysis revealed fast dissociation/association between the tetramer and hCD134, although the affinity was high (KD  = 18 nM) and comparable to those for the neutralizing antibodies (anti-gQ1: 17 nM, anti-gH: 2.7 nM). A competition assay demonstrated that the anti-gQ1 antibody competed with hCD134 in the HHV-6B tetramer binding whereas the anti-gH antibody did not, indicating the direct interaction of gQ1 and hCD134. A single-particle analysis by negative-staining electron microscopy revealed the tetramer's elongated shape with a gH/gL part and extra density corresponding to gQ1/gQ2. The anti-gQ1 antibody bound to the tip of the extra density, and anti-gH antibody bound to the putative gH/gL part. These results highlight the interaction of gQ1/gQ2 in the HHV-6B tetramer with hCD134, and they demonstrate common features among viral ligands of the betaherpesvirus subfamily from a macroscopic viewpoint.

Imaging Assessment of Complications from Transplantation from Pediatric to Adult Patients: Part 2: Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation is an intravenous transfusion of pluripotent stem cells to repopulate the marrow and restore immunocompetence. However, before transplantation, the patient undergoes a conditioning regimen to eradicate the underlying disease, subsequently resulting in an immunocompromised state. Serious and some life-threatening complications involving any organ can occur. Currently, with advances in hematopoietic stem cell transplantation techniques and posttransplant management, more pediatric patients are now living longer and into their adulthood. The goal of this review article is to discuss the common neurologic, pulmonary, and abdominal complications associated with hematopoietic stem cell transplantation with emphasis on their imaging characteristics.

HHV-6-Associated Neurological Disease in Children: Epidemiologic, Clinical, Diagnostic, and Treatment Considerations

Human herpesviruses 6A and 6B, often referred to collectively as human herpesvirus 6, are a pair of beta-herpesviruses known to cause a variety of clinical syndromes in both immunocompetent and immunocompromised individuals. Most humans are infected with human herpesvirus 6B, and many with human herpesvirus 6A. Primary infection typically occurs in early childhood, although large-scale reviews on the topic are limited. Herein, the authors explore the clinical manifestations of human herpesvirus 6-associated disease in both immunocompetent and immunocompromised pediatric patients, the risk factors for development of human herpesvirus 6-associated neurological disease, the risk of autoimmunity associated with development of active or latent infection, the relevance of human herpesvirus 6-specific diagnostic tests, and the medications used to treat human herpesvirus 6. The goal of this review is to improve the current understanding of human herpesvirus 6 in pediatric populations and to examine the most effective diagnostic and therapeutic interventions in this disease state.

An Animal Model That Mimics Human Herpesvirus 6B Pathogenesis

Human herpesvirus 6B (HHV-6B), a T-lymphotropic virus, infects almost exclusively humans. An animal model of HHV-6B has not been available. Here, we report the first animal model to mimic HHV-6B pathogenesis; the model is based on humanized mice in which human immune cells were engrafted and maintained. For HHV-6B replication, adequate human T-cell activation (which becomes susceptible to HHV-6B) is necessary in this murine model. Here, we found that an additional transfer of human mononuclear cells to humanized mice resulted in an explosive proliferation of human activated T cells, which could be representative of graft-versus-host disease (GVHD) because the primary transfer of human cells was not sufficient to increase the number and ratio of human T cells. Mice infected with HHV-6B became weak and/or died approximately 7 to 14 days later. Quantitative PCR analysis revealed that the spleen and lungs were the major sites of HHV-6B replication in this model, and this was corroborated by the detection of viral proteins in these organs. Histological analysis also revealed the presence of megakaryocytes, indicating HHV-6B infection. Multiplex analysis of cytokines/chemokines in sera from the infected mice showed secretions of human cytokines/chemokines as reported for both in vitro infection and clinical samples, indicating that the secreted cytokines could affect pathogenesis. This is the first animal model showing HHV-6B pathogenesis, and it will be useful for elucidating the pathogenicity of HHV-6B, which is related to GVHD and idiopathic pneumonia syndrome.IMPORTANCE Human herpesvirus 6B (HHV-6B) is a ubiquitous virus that establishes lifelong latent infection only in humans, and the infection can reactivate, with severe complications that cause major problems. A small-animal model of HHV-6B infection has thus been desired for research regarding the pathogenicity of HHV-6B and the development of antiviral agents. We generated humanized mice by transplantation with human hematopoietic stem cells, and here, we modified the model by providing an additional transfer of human mononuclear cells, providing the proper conditions for efficient HHV-6B infection. This is the first humanized mouse model to mimic HHV-6B pathogenesis, and it has great potential for research into the in vivo pathogenesis of HHV-6B.

Herpes Virus Infections Other than Cytomegalovirus in the Recipients of Hematopoietic Stem Cell Transplantation

This review discusses the epidemiologic and clinical aspects of herpes viruses other than cytomegalovirus in patients who have undergone hematopoietic stem cell transplantation.

Molecular Diagnostic Advances in Transplant Infectious Diseases

PURPOSE OF REVIEW

The infectious complications of transplantation can have devastating consequences for patients. Early and accurate diagnosis is essential to good outcomes. This review describes recent advances in pathogen-directed diagnostic testing and discusses the role of new methods for transplant infectious diseases.

RECENT FINDINGS

Several molecular assays have been introduced into clinical practice in recent years. When the results of rapid testing are linked to patient-specific interventions, improved outcomes can be realized. Syndromic testing along with metagenomic next-generation sequencing (mNGS) represents novel approaches to infection diagnosis. However, the optimal use of these tests for transplant patients along with an overall assessment of cost-effectiveness demands further study. Molecular diagnostics are revolutionizing transplant care. Clinicians need to be aware of the current diagnostic landscape and have a working knowledge of the nuances related to test performance, result interpretation, and cost.

Clinical characteristics of human herpesvirus-6 myelitis after allogeneic hematopoietic stem cell transplantation and its favorable outcome by early intervention

After allogeneic hematopoietic stem cell transplantation (HSCT), human herpesvirus-6 (HHV-6) can cause serious central nervous system (CNS) disorder and typically presents as encephalitis. Another manifestation of HHV-6 is myelitis, which has not been fully evaluated. In this study, we retrospectively analyzed 19 patients who developed HHV-6 myelitis after allogeneic HSCT. Median onset was 20 days after transplantation (range, 13-31), with a cumulative incidence of 4.1% at day 40 after transplantation. Median age at transplant was 50 years (range, 17-61). Median copy number of HHV-6 DNA was 3000 copies/ml in cerebrospinal fluid (CSF; range, 200-100,000). The most common symptoms were pruritus, pain of the extremities/back, and numbness. Three patients subsequently developed encephalitis in the clinical course of myelitis; their HHV-6 copy numbers in CSF had been higher than 10,000 copies/ml at the onset of myelitis. Antiviral agents were initiated shortly after onset in all patients, resulting in recovery. These results suggest that myelitis would be an important subtype of HHV-6-associated CNS disorders after allogeneic HSCT, whose prognosis could be favorable by an early intervention. Transplant physicians should recognize early posttransplant neurological symptoms such as pruritus, pain, or numbness as possible signs of HHV-6 myelitis, which could also progress to encephalitis.

Clinical practice recommendations for the diagnosis and management of human herpesvirus-6B encephalitis after allogeneic hematopoietic stem cell transplantation: the Japan Society for Hematopoietic Cell Transplantation

Reactivation of human herpesvirus (HHV)-6B is relatively common after allogeneic hematopoietic stem cell transplantation (HSCT) and HHV-6B diseases may consequently develop. Among them, HHV-6B encephalitis is a serious and often fatal complication. The aim of these clinical practice recommendations is to provide diagnostic and therapeutic guidance for HHV-6B encephalitis after allogeneic HSCT. In this evidence-based review, we critically evaluated data from the published literature. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology was used to assist in generating recommendations. We have summarized the findings that contribute to decision-making and we have provided our recommendations. In cases where rigorous clinical data are unavailable, recommendations have been developed in discussions with physicians who have relevant expertize.

Clinical Significance of Human Herpesvirus 6 Positivity on the FilmArray Meningitis/Encephalitis Panel

A review of 15 patients who tested positive for human herpesvirus 6 (HHV-6) on the FilmArray Meningitis/Encephalitis panel revealed that the majority were unlikely to have HHV-6 encephalitis. Criteria to assist interpretation of HHV-6 positive results are presented.

Central nervous system disorders after hematopoietic stem cell transplantation: a prospective study of the Infectious Diseases Working Party of EBMT

We performed a prospective study to evaluate the types and characteristics of central nervous system (CNS) disorders in patients after hematopoietic stem cell transplantation. The study included 163 episodes of CNS disorders of which 58 (36%) were infections. Proven or probable infections were documented in 34 patients and included fungi (n = 10, 29%), viruses (n = 12, 35%), Toxoplasma spp. (n = 9, 27%) and bacteria (n = 3, 9%). Non-infectious neurological disorders (n = 105, 64%) frequently encompassed metabolic/drug-induced abnormalities (n = 28, 27%) or cerebral vascular events (n = 22, 21%). Median onset times were later for infectious (day + 101) vs non-infectious neurological disorders (day + 50, p = 0.009). An unremarkable cranial CT scan was found in 33% of infection episodes. Absence of cerebrospinal fluid pleocytosis despite a normal or increased peripheral blood white blood cell count occurred in 26% of infections. Day-30 mortality rates were significantly higher for fungal (87%) vs non-fungal infections (40%, p < 0.001). Significantly higher mortality rates were also documented for cerebral vascular events than for other non-infectious disorders (86% vs 34%, p < 0.001). Our prospective study shows that diagnostic findings in CNS infections might differ between hematopoietic stem cell transplant recipients and immunocompetent hosts. Special awareness and timely initiation of adequate diagnostics are crucial to improve the prognosis of these patients.

Correlations of cytokine levels in cerebrospinal fluid and peripheral blood with outcome of HHV-6B encephalitis after hematopoietic stem cell transplantation

BACKGROUND

Human herpesvirus (HHV)-6B encephalitis has been recognized as a serious complication after allogeneic hematopoietic cell transplantation (allo-HCT). Little is known about the pathogenic mechanism for its progression.

STUDY DESIGN

We retrospectively evaluated the 16 kinds of cytokines and chemokines in cerebrospinal fluid (CSF) and plasma in patients who developed HHV-6B encephalitis. Among a total of 20 patients, 12 were categorized as the poor prognosis group (died of encephalitis; n = 8 and retained sequelae; n = 4), and other eight patients were categorized as the good prognosis group (complete recovery; n = 8).

RESULTS

Concentrations of CSF IL-6 and IL-8 at the onset of encephalitis were significantly higher in the poor prognosis group than in the good prognosis group (median CSF IL-6, 28.27 pg/mL vs 14.32 pg/mL, P = .004; median CSF IL-8, 128.70 pg/mL vs 59.43 pg/mL, P = .043). Regarding plasma, the concentration of each cytokine at the onset of encephalitis was not significantly different between the two groups, except IL-5. However, higher levels of IL-6, IL-7, and MCP-1 and lower levels of IL-12 were observed 1 week before the development of encephalitis in patients with poor prognosis (median IL-6; 464.17 pg/mL vs 47.82 pg/mL, P = .02; median IL-12; 1.63 pg/mL vs 6.57 pg/mL, P = .03).

CONCLUSION

We found that one week before onset of HHV-6B encephalitis, poor prognosis patients had high plasma concentrations of IL-6, IL-7, and MCP-1 and low concentrations of IL-12. At the onset of encephalitis, high concentrations of IL-6 and IL-8 in CSF were more common in the poor prognosis group, consistent with other evidence that IL-6 can have a role in CNS disturbances. Our findings show that specific cytokine status is associated with severe brain damage in patients with HHV-6B encephalitis, demonstrate prognostic value of plasma IL-6 concentrations, and suggest evaluation of anti-cytokine therapeutics in patients with HHV-6B encephalitis.

Gastroenteritis, Hepatitis, Encephalopathy, and Human Herpesvirus 6 Detection in an Immunocompetent Child: Benefits and Risks of Syndromic Multiplex Molecular Panel Testing

An immunocompetent toddler came to medication attention with gastroenteritis, complicated by encephalopathy and hepatitis. Multiplexed testing using a polymerase chain reaction meningitis panel was positive for human herpesvirus 6 (HHV-6). Clinical correlation, quantitative HHV-6 polymerase chain reaction, and metagenomic next-generation sequencing supported a likely diagnosis of primary HHV-6B infection.

Guidelines from the 2017 European Conference on Infections in Leukaemia for management of HHV-6 infection in patients with hematologic malignancies and after hematopoietic stem cell transplantation

Of the two human herpesvirus 6 (HHV-6) species, human herpesvirus 6B (HHV-6B) encephalitis is an important cause of morbidity and mortality after allogeneic hematopoietic stem cell transplant. Guidelines for the management of HHV-6 infections in patients with hematologic malignancies or post-transplant were prepared a decade ago but there have been no other guidelines since then despite significant advances in the understanding of HHV-6 encephalitis, its therapy, and other aspects of HHV-6 disease in this patient population. Revised guidelines prepared at the 2017 European Conference on Infections in Leukaemia covering diagnosis, preventative strategies and management of HHV-6 disease are now presented.

Posterior reversible encephalopathy syndrome concurrent with human herpesvirus-6B encephalitis after allogeneic hematopoietic stem cell transplantation

Posterior reversible encephalopathy syndrome (PRES) and human herpesvirus (HHV)-6 encephalitis are both serious neurological complications post hematopoietic stem cell transplantation. Although infection is one of the important causes of PRES, only few cases have reported the relation between PRES and viral infection. Herein, we report the first adult case of PRES concurrent with HHV-6 encephalitis after allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia. This case suggests that HHV-6 reactivation is associated with the pathogenesis of PRES. Also, PRES and HHV-6 encephalitis cause similar symptoms, and switching the immunosuppressant from calcineurin inhibitor to prednisolone for treating PRES may worsen HHV-6 encephalitis. Therefore, we should pay attention to the complication of HHV-6 encephalitis even after PRES is diagnosed.

Clinical Metagenomic Sequencing for Diagnosis of Meningitis and Encephalitis

BACKGROUND

Metagenomic next-generation sequencing (NGS) of cerebrospinal fluid (CSF) has the potential to identify a broad range of pathogens in a single test.

METHODS

In a 1-year, multicenter, prospective study, we investigated the usefulness of metagenomic NGS of CSF for the diagnosis of infectious meningitis and encephalitis in hospitalized patients. All positive tests for pathogens on metagenomic NGS were confirmed by orthogonal laboratory testing. Physician feedback was elicited by teleconferences with a clinical microbial sequencing board and by surveys. Clinical effect was evaluated by retrospective chart review.

RESULTS

We enrolled 204 pediatric and adult patients at eight hospitals. Patients were severely ill: 48.5% had been admitted to the intensive care unit, and the 30-day mortality among all study patients was 11.3%. A total of 58 infections of the nervous system were diagnosed in 57 patients (27.9%). Among these 58 infections, metagenomic NGS identified 13 (22%) that were not identified by clinical testing at the source hospital. Among the remaining 45 infections (78%), metagenomic NGS made concurrent diagnoses in 19. Of the 26 infections not identified by metagenomic NGS, 11 were diagnosed by serologic testing only, 7 were diagnosed from tissue samples other than CSF, and 8 were negative on metagenomic NGS owing to low titers of pathogens in CSF. A total of 8 of 13 diagnoses made solely by metagenomic NGS had a likely clinical effect, with 7 of 13 guiding treatment.

CONCLUSIONS

Routine microbiologic testing is often insufficient to detect all neuroinvasive pathogens. In this study, metagenomic NGS of CSF obtained from patients with meningitis or encephalitis improved diagnosis of neurologic infections and provided actionable information in some cases. (Funded by the National Institutes of Health and others; PDAID ClinicalTrials.gov number, NCT02910037.).

Human herpesvirus 6 infection after autologous stem cell transplantation: A multicenter prospective study in adult patients

OBJECTIVES

to prospectively evaluate the incidence and the clinical relevance on hematopoietic reconstitution of HHV-6 infection in autologous hematopoietic stem cell transplantation (ASCT) recipients.

METHODS

HHV-6 DNA load was measured in whole blood specimens once during the 7 days before stem cell re-infusion and once a week after transplantation until hematopoietic recovery. Active HHV-6 infection was defined by 2 consecutive positive DNA loads.

RESULTS

from July 2012 to February 2015, 196 adult patients undergoing ASCT were enrolled. Twenty-two (11.2%) patients developed active HHV-6 infection with a cumulative incidence of 19% at 40 days after transplantation. The onset of active HHV-6 infection occurred with a median of 13 days after stem cell re-infusion. HHV-6 infection was associated with an increased frequency of non-infectious complications (OR = 5.05; 95%CI 1.78-14.32; P < 0.001). Moreover, the severity of these non-infectious complications was higher in recipients exhibiting HHV-6 infection (OR = 4.62; 95%CI 1.32-16.2; p < 0.01). Delayed neutrophils 10 (IQR: 8-14) vs 8 (IQR: 6-11) days and platelets recoveries 15 (IQR: 11.8-18.5) vs 8 (IQR: 4-14) days were observed in patients with active HHV-6 infection compared to non-infected ones.

CONCLUSIONS

in this study, 11.2% ASCT recipients presented active HHV-6 infection associated with significantly delayed hematologic reconstitution.

Humanization of Murine Neutralizing Antibodies against Human Herpesvirus 6B

Exanthem subitum is a common childhood illness caused by primary infection with human herpesvirus 6B (HHV-6B). It is occasionally complicated by febrile seizures and even encephalitis. HHV-6B reactivation also causes encephalitis, especially after allogeneic hematopoietic stem cell transplantation. However, no adequate antiviral treatment for HHV-6B has yet been established. Mouse-derived monoclonal antibodies (MAbs) against the HHV-6B envelope glycoprotein complex gH/gL/gQ1/gQ2 have been shown to neutralize the viral infection. These antibodies have the potential to become antiviral agents against HHV-6B despite their inherent immunogenicity to the human immune system. Humanization of MAbs derived from other species is one of the proven solutions to such a dilemma. In this study, we constructed chimeric forms of two neutralizing MAbs against HHV-6B to make humanized antibodies. Both showed neutralizing activities equivalent to those of their original forms. This is the first report of humanized antibodies against HHV-6B and provides a basis for the further development of HHV-6B-specific antivirals.IMPORTANCE Human herpesvirus 6B (HHV-6B) establishes lifelong latent infection in most individuals after the primary infection. Encephalitis is the most severe complication caused by both the primary infection and the reactivation of HHV-6B and is the cause of considerable mortality in patients, without any established treatments to date. The humanization of the murine neutralizing antibodies described in this research provided a feasible way to reduce the inherent immunogenicity of the antibodies without changing their neutralizing activities. These newly designed chimeric antibodies against HHV-6B have the potential to be candidates for antivirals for future use.

Increased opportunity for prolonged survival after allogeneic hematopoietic stem cell transplantation in patients aged 60-69 years with myelodysplastic syndrome

We conducted a nationwide retrospective study to evaluate the outcomes of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in 651 patients aged 60-69 years with de novo myelodysplastic syndrome (MDS). We divided patients into two groups: 152 and 499 patients with an early and advanced disease status, respectively. The 3-year overall survival (OS) rate of patients with an early disease status was 45.9% (95% confidence interval [CI], 37.0 to 54.2%). A multivariate analysis revealed five adverse factors for OS: performance status (PS) 2-4 (hazard ratio [HR] 4.48; P < .001), poor cytogenetic risk group (HR 1.83; P = .041), male recipient (HR 2.58; P = .003), use of HLA-mismatched related grafts (HR 4.75; P = .003), and unrelated cord blood (HR 2.47; P = .023). The 3-year OS rate of patients with an advanced disease status was 37.2% (95% CI 32.4 to 41.9%). Five factors correlated with worse OS: PS 2-4 (HR 1.72; P = .003), poor cytogenetic risk group (HR 1.49; P = .003), use of HLA-mismatched related grafts (HR 1.96; P = .015), unrelated cord blood (HR 2.05; P < .001), and the high number of red blood cell transfusions before transplantation (HR 1.85; P = .018). The present results revealed the more frequent utilization of allo-HSCT for MDS patients aged 60-69 years, which increases the curative potential.

Identification of CD4 and H-2Kd-restricted cytotoxic T lymphocyte epitopes on the human herpesvirus 6B glycoprotein Q1 protein

The identification of Human herpesvirus 6B (HHV-6B) epitopes that are recognized by T-cells could contribute to the development of potential vaccines and immunotherapies. Here, we identified CD4⁺ and H-2K^d-restricted CD8⁺ T-cell epitopes on the glycoprotein Q1 of HHV-6B (BgQ1), which is a unique glycoprotein and essential for HHV-6B viral entry, by using in vivo electroporation with a plasmid DNA encoding BgQ1, overlapping peptides spanning the BgQ1 sequence, ELISPOT assay for quantification of gamma interferon (IFN-γ), and computer-based T-cell epitope prediction programs. The CD4⁺ and CD8⁺ T-cell epitopes identified in BALB/c mice in this study could be a good animal model system for use in the development of T-cell responses, inducing HHV-6B vaccines or immunotherapies.

Overview of Infections Complicating Pediatric Hematopoietic Cell Transplantation

Hematopoietic cell transplantations (HCT) are increasingly being performed in children for the treatment of malignant and nonmalignant diseases. Infections remain an important cause of morbidity and mortality after HCT, where the type and timing of infection is influenced by host, transplant, and pathogen-related factors. Herein, an overview of the epidemiology of infections is presented and organized by timing before and after HCT, understanding that infection may occur at any time point until there is successful immune reconstitution.