HHV-6B detection and host gene expression implicate HHV-6B as pulmonary pathogen after hematopoietic cell transplant.

Limited understanding of the immunopathogenesis of human herpesvirus 6B (HHV-6B) has prevented its acceptance as a pulmonary pathogen after hematopoietic cell transplant (HCT). In this prospective multicenter study of patients undergoing bronchoalveolar lavage (BAL) for pneumonia after allogeneic HCT, we test blood and BAL fluid (BALF) for HHV-6B DNA and mRNA transcripts associated with lytic infection and perform RNA-seq on paired blood. Among 116 participants, HHV-6B DNA is detected in 37% of BALs, 49% of which also have HHV-6B mRNA detection. We establish HHV-6B DNA viral load thresholds in BALF that are highly predictive of HHV-6B mRNA detection and associated with increased risk for overall mortality and death from respiratory failure. Participants with HHV-6B DNA in BALF exhibit distinct host gene expression signatures, notable for enriched interferon signaling pathways in participants clinically diagnosed with idiopathic pneumonia. These data implicate HHV-6B as a pulmonary pathogen after allogeneic HCT.

A Randomized Controlled Trial of Animal-assisted Activities for Pediatric Oncology Patients: Psychosocial and Microbial Outcomes.

INTRODUCTION: Evidence about the effectiveness and safety of dog visits in pediatric oncology is limited. METHOD: We conducted a randomized controlled trial (n=26) of dog visits versus usual care among pediatric oncology inpatients. Psychological functioning and microbial load from hand wash samples were evaluated. Parental anxiety was a secondary outcome. RESULTS: We did not observe a difference in the adjusted mean present functioning score (-3.0; 95% confidence interval [CI], -12.4 to 6.4). The difference in microbial load on intervention versus control hands was -0.04 (95% CI, -0.60 to 0.52) log10 CFU/mL, with an upper 95% CI limit below the prespecified noninferiority margin. Anxiety was lower in parents of intervention versus control patients. DISCUSSION: We did not detect an effect of dog visits on functioning; however, our study was underpowered by low recruitment. Visits improved parental anxiety. With hand sanitization, visits did not increase hand microbial levels. CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov NCT03471221.

Viral Encephalitis after Hematopoietic Cell Transplantation: A Systematic Review.

Viral encephalitis is a rare but serious complication after hematopoietic cell transplantation (HCT). The nonspecific early signs and symptoms and rapid progression can make it difficult to diagnose and treat in a timely fashion. To better inform clinical decision making in post-HCT viral encephalitis, a systematic review of prior studies of viral encephalitis was performed, with the goal of characterizing the frequency of various infectious etiologies and their clinical course, including treatments and outcomes. A systematic review of studies of viral encephalitis was performed. Studies were included if they described a cohort of HCT recipients who were tested for at least 1 pathogen. Of 1613 unique articles initially identified, 68 met the inclusion criteria, with a total of 72,423 patients studied. A total of 778 cases of encephalitis were reported (1.1%). Human herpesvirus 6 (HHV-6) (n = 596), Epstein-Barr virus (n = 76), and cytomegalovirus (n = 33) were the most commonly reported causes of encephalitis, and HHV-6 encephalitis tended to occur the earliest, accounting for most cases prior to day +100 post-transplantation. Of 29,671 patients with available transplantation data, encephalitis was diagnosed in 282 of 4707 (6.0%) cord blood transplantation (CBT) recipients, in 372 of 24,664 (1.5%) non-CBT allogeneic HCT recipients, and in 5 of 300 (1.7%) autologous HCT recipients. Of the 282 CBT encephalitis cases, 270 (95.7%) were caused by HHV-6. Overall, 288 (37.0%) of the 778 patients with encephalitis died, and 75 deaths were attributable to encephalitis, with the time between diagnosis and death ranging from 3 to 192 days. Viral encephalitis occurs in approximately 1% of HCT recipients, and HHV-6 is the most common cause. Mortality following encephalitis in HCT recipients is high, indicating an urgent need for advancement in preventive and therapeutic strategies.

Prospective Evaluation of Galactomannan and (1→3) ß-d-Glucan Assays as Diagnostic Tools for Invasive Fungal Disease in Children, Adolescents, and Young Adults With Acute Myeloid Leukemia Receiving Fungal Prophylaxis.

BACKGROUND: Patients receiving chemotherapy for acute myeloid leukemia (AML) are at high risk for invasive fungal disease (IFD). Diagnosis of IFD is challenging, leading to interest in fungal biomarkers. The objective was to define the utility of surveillance testing with Platelia Aspergillus galactomannan (GM) enzyme immunoassay (EIA) and Fungitell ß-d-glucan (BDG) assay in children with AML receiving antifungal prophylaxis. METHODS: Twice-weekly surveillance blood testing with GM EIA and BDG assay was performed during periods of neutropenia in the context of a randomized trial of children, adolescents, and young adults with AML allocated to fluconazole or caspofungin prophylaxis. Proven or probable IFD was adjudicated using blinded central reviewers. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for Platelia and Fungitell assays alone and in combination for the outcomes of proven and probable invasive aspergillosis (IA) or invasive candidiasis (IC). RESULTS: Among 471 patients enrolled, 425 participants (209 fluconazole and 216 caspofungin) contributed ≥1 blood specimen. In total, 6103 specimens were evaluated, with a median of 15 specimens per patient (range 1-43). The NPV was >99% for GM EIA and BDG assay alone and in combination. However, there were no true positive results, resulting in sensitivity and PPV for each assay of 0%. CONCLUSIONS: The GM EIA and the BDG assay alone or in combination were not successful at detecting IA or IC during periods of neutropenia in children, adolescents, and young adults with AML receiving antifungal prophylaxis. Utilization of these assays for surveillance in this clinical setting should be discouraged.

Association of Inherited Chromosomally Integrated Human Herpesvirus 6 with Neurologic Symptoms and Management after Allogeneic Hematopoietic Cell Transplantation.

Reactivation of human herpesvirus 6 (HHV-6) after allogeneic hematopoietic cell transplantation (HCT) is associated with neurologic complications, but the impact of donor and/or recipient inherited chromosomally integrated HHV-6 (iciHHV-6) on post-HCT central nervous system (CNS) symptoms and diagnostic and therapeutic interventions is not well understood. The aims of the present study were (1) to compare the cumulative incidence of CNS symptoms in the first 100 days following allogeneic HCT among patients with donor and/or recipient iciHHV-6 (iciHHV-6pos)with that of patients with neither donor nor recipient iciHHV-6 (iciHHV-6neg) and (2) to assess the role of HHV-6 detection in driving potentially unnecessary interventions in iciHHV-6pos patients. We performed a retrospective matched cohort study of 87 iciHHV-6pos and 174 iciHHV-6neg allogeneic HCT recipients. HHV-6 testing was performed at the discretion of healthcare providers, who were unaware of iciHHV-6 status. The cumulative incidence of CNS symptoms was similar in iciHHV-6pos (n = 37; 43%) and iciHHV-6neg HCT recipients (n = 81; 47%; P = .63). HHV-6 plasma testing was performed in similar proportions of iciHHV-6pos (n = 6; 7%) and iciHHV-6neg (9%) patients and was detected in all tested iciHHV-6pos HCTs and 2 (13%) iciHHV-6neg HCTs. This resulted in more frequent HHV-6-targeted antiviral therapy after iciHHV-6pos HCT (odds ratio, 12.8; 95% confidence interval, 1.5 to 108.2) with associated side effects. HHV-6 plasma detection in 2 iciHHV-6pos patients without active CNS symptoms prompted unnecessary lumbar punctures. The cumulative incidence of CNS symptoms was similar after allogeneic HCT involving recipients or donors with and without iciHHV-6. Misattribution of HHV-6 detection as infection after iciHHV-6pos HCT may lead to unnecessary interventions. Testing for iciHHV-6 may improve patient management.

Donor-Derived CD4+ T Cells and Human Herpesvirus 6B Detection After Allogeneic Hematopoietic Cell Transplantation.

We sought to determine whether donor-derived human herpesvirus (HHV) 6B-specific CD4+ T-cell abundance is correlated with HHV-6B detection after allogeneic hematopoietic cell transplantation. We identified 33 patients who received HLA-matched, non-T-cell-depleted, myeloablative allogeneic hematopoietic cell transplantation and underwent weekly plasma polymerase chain reaction testing for HHV-6B for 100 days thereafter. We tested donor peripheral blood mononuclear cells for HHV-6B-specific CD4+ T cells. Patients with HHV-6B detection above the median peak viral load (200 copies/mL) received approximately 10-fold fewer donor-derived total or HHV-6B-specific CD4+ T cells than those with peak HHV-6B detection at ≤200 copies/mL or with no HHV-6B detection. These data suggest the importance of donor-derived immunity for controlling HHV-6B reactivation.

Chlorhexidine gluconate bathing in children with cancer or those undergoing hematopoietic stem cell transplantation: A double-blinded randomized controlled trial from the Children's Oncology Group.

BACKGROUND: To the authors' knowledge, information regarding whether daily bathing with chlorhexidine gluconate (CHG) reduces central line-associated bloodstream infection (CLABSI) in pediatric oncology patients and those undergoing hematopoietic stem cell transplantation (HCT) is limited. METHODS: In the current multicenter, randomized, double-blind, placebo-controlled trial, patients aged ≥2 months and <22 years with cancer or those undergoing allogeneic HCT were randomized 1:1 to once-daily bathing with 2% CHG-impregnated cloths or control cloths for 90 days. The primary outcome was CLABSI. Secondary endpoints included total positive blood cultures, acquisition of resistant organisms, and acquisition of cutaneous staphylococcal isolates with an elevated CHG mean inhibitory concentration. RESULTS: The study was stopped early because of poor accrual. Among the 177 enrolled patients, 174 were considered as evaluable (88 were randomized to the CHG group and 86 were randomized to the control group). The rate of CLABSI per 1000 central line days in the CHG group was 5.44 versus 3.10 in the control group (risk difference, 2.37; 95% confidence interval, 0.05-4.69 [P = .049]). Post hoc conditional power analysis demonstrated a 0.2% chance that the results would have favored CHG had the study fully enrolled. The rate of total positive blood cultures did not differ between groups (risk difference, 2.37; 95% confidence interval, -0.41 to 5.14 [P = .078]). The number of patients demonstrating the new acquisition of resistant organisms did not differ between groups (P = .54). Patients in the CHG group were found to be more likely to acquire cutaneous staphylococcal isolates with an elevated CHG mean inhibitory concentration (P = .032). CONCLUSIONS: The data from the current study do not support the use of routine CHG bathing in children with cancer or those undergoing allogeneic HCT.

Collaborative Multidisciplinary Incident Command at Seattle Children's Hospital for Rapid Preparatory Pediatric Surgery Countermeasures to the COVID-19 Pandemic.

Washington was the first US state to have a patient test positive for COVID-19. Before this, our children's hospital proactively implemented an incident command structure that allowed for collaborative creation of safety measures, policies, and procedures for patients, families, staff, and providers. Although the treatment and protective standards are continuously evolving, this commentary shares our thoughts on how an institution, and specifically, surgical services, may develop collaborative process improvement to accommodate for rapid and ongoing change. Specific changes outlined include early establishment of incident command; personal protective equipment conservation; workforce safety; surgical and ambulatory patient triage; and optimization of trainee education. Please note that the contents of this manuscript are shared in the interest of providing collaborative information and are under continuous development as our regional situation changes. We recognize the limitations of this commentary and do not suggest that our approaches represent validated best practices.

Oral brincidofovir decreases the incidence of HHV-6B viremia after allogeneic HCT.

Human herpesvirus 6B (HHV-6B) frequently reactivates after allogeneic hematopoietic cell transplantation (HCT). There are no randomized studies of antiviral treatments to prevent HHV-6B reactivation. Brincidofovir has high in vitro activity against HHV-6B and other DNA viruses, but its in vivo activity for HHV-6B has not been demonstrated. We performed a post hoc analysis of a randomized controlled trial of twice-weekly oral brincidofovir for cytomegalovirus prophylaxis after allogeneic HCT to study the effect of brincidofovir on HHV-6B reactivation. We included patients randomized within 2 weeks of HCT and who received at least 6 consecutive doses of study drug after randomization. We tested plasma for HHV-6B through week 6 post-HCT. The cohort consisted of 92 patients receiving brincidofovir and 61 receiving placebo. The cumulative incidence of HHV-6B plasma detection through day 42 post-HCT was significantly lower among patients receiving brincidofovir (14.2%) compared with placebo (32.4%; log-rank, 0.019). In an adjusted Cox model, brincidofovir exposure remained associated with a lower hazard for HHV-6B plasma detection (hazard ratio, 0.40; 95% confidence interval, 0.20-0.80). In conclusion, brincidofovir prophylaxis reduced HHV-6B reactivation after allogeneic HCT in a post hoc analysis of a randomized controlled trial. These data support the study of intravenous brincidofovir for HHV-6B prophylaxis.

Inflammatory Cytokine Profile in Individuals with Inherited Chromosomally Integrated Human Herpesvirus 6.

Acute graft-versus-host-disease (aGVHD) is a major complication following hematopoietic cell transplantations (HCTs). We have shown that HCT recipients in whom either the donor or patient had inherited chromosomally integrated human herpesvirus 6 (iciHHV-6) have a higher incidence of developing more severe aGVHD. Previous studies established that increased proinflammatory cytokines are associated with increased risk for aGVHD and nonrelapse mortality post-HCT. We hypothesized that HCT recipients with donor or recipient iciHHV-6 (iciHHV-6pos HCT cases) will have higher cytokine levels compared with HCT recipients without iciHHV-6 (iciHHV-6neg HCT controls). We identified 64 iciHHV-6pos HCT cases with plasma from days 7, 14, and/or 21 post-HCT and before aGVHD onset in patients who developed aGVHD. We identified 64 iciHHV-6neg HCT controls matched for aGVHD risk factors. We also identified 28 donors with iciHHV-6 and 56 matched donors without iciHHV-6. We measured plasma cytokine concentrations for IL-6, suppression of tumorigenicity 2, T cell immunoglobulin and mucin-domain containing 3, TNFα, soluble TNF receptor 1 (TNFRp55), and C-reactive protein (CRP). We used Mann-Whitney tests and repeated-measures models to compare cytokine levels. iciHHV-6pos HCT cases had higher CRP levels on day 7 and day 21 and higher TNFRp55 levels on day 14 and day 21 compared with iciHHV-6neg HCT controls. These findings were recapitulated in a repeated-measures model. The differences were most evident among patients who subsequently developed aGVHD grades 2 to 4. Additionally, iciHHV-6pos HCT cases had earlier-onset aGVHD (median, 20 versus 27 days post-HCT; P = .02). There were no differences in cytokine levels among healthy donors with or without iciHHV-6. This study demonstrates that HCT recipients with iciHHV-6 have higher proinflammatory cytokines that may be associated with increased risk for aGVHD.

Validation of an Electronic Surveillance Algorithm to Identify Patients With Post-Operative Surgical Site Infections Using National Surgical Quality Improvement Program Pediatric Data.

BACKGROUND: Surgical site infections (SSIs) are common, but data related to these infections maybe difficult to capture. We developed an electronic surveillance algorithm to identify patients with SSIs. Our objective was to validate our algorithm by comparing it with our institutional National Surgical Quality Improvement Program Pediatric (NSQIP Peds) data. METHODS: We applied our algorithm to our institutional NSQIP Peds 2015-2017 cohort. The algorithm consisted of the presence of a diagnosis code for post-operative infection or the presence of 4 criteria: diagnosis code for infection, antibiotic administration, positive culture, and readmission/surgery related to infection. We compared the algorithm's SSI rate to the NSQIP Peds identified SSI. Algorithm performance was assessed using sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and Cohen's kappa. The charts of discordant patients were reviewed to understand limitations of the algorithm. RESULTS: Of 3879 patients included, 2.5% had SSIs by NSQIP Peds definition and 1.9% had SSIs by our algorithm. Our algorithm achieved a sensitivity of 44%, specificity of 99%, NPV of 99%, PPV of 59%, and Cohen's kappa of 0.5. Of the 54 false negatives, 37% were diagnosed/treated as outpatients, 31% had tracheitis, and 17% developed SSIs during their post-operative admission. Of the 30 false positives, 33% had an infection at index surgery and 33% had SSIs related to other surgeries/procedures. CONCLUSIONS: Our algorithm achieved high specificity and NPV compared with NSQIP Peds reported SSIs and may be useful when identifying SSIs in patient populations that are not actively monitored for SSIs.

Human Herpesvirus 6B and Lower Respiratory Tract Disease After Hematopoietic Cell Transplantation.

PURPOSE: Human herpesvirus 6B (HHV-6B) DNA is frequently detected in bronchoalveolar lavage fluid (BALF) from immunocompromised subjects with lower respiratory tract disease (LRTD). Whether HHV-6B is a pulmonary pathogen is unclear. METHODS: We tested BALF for HHV-6B DNA using polymerase chain reaction in allogeneic hematopoietic cell transplantation (HCT) recipients who underwent a BAL for evaluation of LRTD from 1992 to 2015. We used multivariable proportional hazards models to evaluate the association of HHV-6B+ BALF with overall mortality, death from respiratory failure, and the effect of anti-HHV-6B antivirals on these outcomes. We used branched-chain RNA in situ hybridization to detect HHV-6 messenger RNA (U41 and U57 transcripts) in lung tissue. RESULTS: We detected HHV-6B+ BALF from 147 of 553 (27%) individuals. Subjects with HHV-6B+ BALF, with or without copathogens, had significantly increased risk of overall mortality (adjusted hazard ratio [aHR], 2.18; 95% CI, 1.41-3.39) and death from respiratory failure (aHR, 2.50; 95% CI, 1.56-4.01) compared with subjects with HHV-6B- BALF. Subjects with HHV-6B+ BALF who received antivirals within 3 days pre-BAL had an approximately 1 log10 lower median HHV-6B BALF viral load, as well as a lower risk of overall mortality (aHR, 0.42; 95% CI, 0.16-1.10), compared with subjects with HHV-6B+ BALF not receiving antivirals. We detected intraparenchymal HHV-6 gene expression by RNA in situ hybridization in lung tissue in all three tested subjects with HHV-6B+ BALF and sufficient tissue RNA preservation. CONCLUSION: These data provide evidence that HHV-6B detection in BALF is associated with higher mortality in allogeneic hematopoietic cell transplantation recipients with LRTD. Definitive evidence of causation will require a randomized prevention or treatment trial.

A Novel, Widespread qacA Allele Results in Reduced Chlorhexidine Susceptibility in Staphylococcus epidermidis.

Chlorhexidine gluconate (CHG) is a topical antiseptic widely used in health care settings. In Staphylococcus spp., the pump QacA effluxes CHG, while the closely related QacB cannot due to a single amino acid substitution. We characterized 1,050 cutaneous Staphylococcus isolates obtained from 173 pediatric oncology patients enrolled in a multicenter CHG bathing trial. CHG susceptibility testing revealed that 63 (6%) of these isolates had elevated CHG MICs (≥4 µg/ml). Screening of all 1,050 isolates for the qacA/B gene (the same qac gene with A or B allele) by restriction fragment length polymorphism (RFLP) yielded 56 isolates with a novel qacA/B RFLP pattern, qacA/B273 The CHG MIC was significantly higher for qacA/B273 -positive isolates (MIC50, 4 µg/ml; MIC range, 0.5 to 4 µg/ml) than for other qac groups: qacA-positive isolates (n = 559; MIC50, 1 µg/ml; MIC range, 0.5 to 4 µg/ml), qacB-positive isolates (n = 17; MIC50, 1 µg/ml; MIC range, 0.25 to 2 µg/ml), and qacA/B-negative isolates (n = 418, MIC50, 1 µg/ml; MIC range, 0.125 to 2 µg/ml) (P = 0.001). A high proportion of the qacA/B273 -positive isolates also displayed methicillin resistance (96.4%) compared to the other qac groups (24.9 to 61.7%) (P = 0.001). Whole-genome sequencing revealed that qacA/B273 -positive isolates encoded a variant of QacA with 2 amino acid substitutions. This new allele, named qacA4, was carried on the novel plasmid pAQZ1. The qacA4-carrying isolates belonged to the highly resistant Staphylococcus epidermidis sequence type 2 clone. By searching available sequence data sets, we identified 39 additional qacA4-carrying S. epidermidis strains from 5 countries. Curing an isolate of qacA4 resulted in a 4-fold decrease in the CHG MIC, confirming the role of qacA4 in the elevated CHG MIC. Our results highlight the importance of further studying qacA4 and its functional role in clinical staphylococci.

RNA Sequencing of the In Vivo Human Herpesvirus 6B Transcriptome To Identify Targets for Clinical Assays Distinguishing between Latent and Active Infections.

Human herpesvirus 6B (HHV-6B) DNA is frequently detected in human samples. Diagnostic assays distinguishing HHV-6B reactivation from latency are limited. This has impaired strategies to diagnose and treat HHV-6B-associated diseases. We used RNA sequencing to characterize and compare the HHV-6B transcriptome in multiple sample types, including (i) whole blood from hematopoietic cell transplant (HCT) recipients with and without HHV-6B plasma viremia, (ii) tumor tissue samples from subjects with large B cell lymphoma infected with HHV-6B, (iii) lymphoblastoid cell lines (LCLs) from subjects with inherited chromosomally integrated HHV-6B or latent infection with HHV-6B, and (iv) HHV-6B Z29 infected SupT1 CD4+ T cells. We demonstrated substantial overlap in the HHV-6B transcriptome observed in in vivo and in vitro samples, although there was variability in the breadth and quantity of gene expression across samples. The HHV-6B viral polymerase gene U38 was the only HHV-6B transcript detected in all next-generation RNA sequencing (RNA-seq) data sets and was one of the most highly expressed genes. We developed a novel reverse transcription-PCR assay targeting HHV-6B U38, which identified U38 mRNA in all tested whole-blood samples from patients with concurrent HHV-6B viremia. No HHV-6B U38 transcripts were detected by RNA-seq or reverse transcription-real-time quantitative PCR (RT-qPCR) in whole-blood samples from subjects without HHV-6B plasma detection or from latently infected LCLs. A RT-qPCR assay for HHV-6B U38 may be useful to identify lytic HHV-6B infection in nonplasma samples and samples from individuals with inherited chromosomally integrated HHV-6B. This study also demonstrates the feasibility of transcriptomic analyses for HCT recipients.IMPORTANCE Human herpesvirus 6B (HHV-6B) is a DNA virus that infects most children within the first few years of life. After primary infection, HHV-6B persists as a chronic, latent infection in many cell types. Additionally, HHV-6B can integrate into germ line chromosomes, resulting in individuals with viral DNA in every nucleated cell. Given that PCR to detect viral DNA is the mainstay for diagnosing HHV-6B infection, the characteristics of HHV-6B infection complicate efforts to distinguish between latent and active viral infection, particularly in immunocompromised patients who have frequent HHV-6B reactivation. In this study, we used RNA sequencing to characterize the HHV-6B gene expression profile in multiple sample types, and our findings identified evidence-based targets for diagnostic tests that distinguish between latent and active viral infection.

Cytomegalovirus in Pediatric Hematopoietic Stem Cell Transplantation: A Case-Based Panel Discussion of Current Challenges.

Cytomegalovirus (CMV) remains a significant contributor to morbidity and death after pediatric solid and stem cell transplantation. Decisions regarding prevention and treatment often lack pediatric-specific data to drive decision making. We present here a case-based discussion around some of these specific topics and focus on approaches to CMV prevention, post-CMV secondary prophylaxis options, and identification and treatment of resistant CMV infection, including emerging antiviral agents and the use of cytotoxic CMV-specific T-cells, in the setting of pediatric hematopoietic stem cell transplantation.

HHV-6B infection, T-cell reconstitution, and graft-vs-host disease after hematopoietic stem cell transplantation.

Successful and sustained CD4+ T-cell reconstitution is associated with increased survival after hematopoietic cell transplantation (HCT), but opportunistic infections may adversely affect the time and extent of immune reconstitution. Human herpesvirus 6B (HHV-6B) efficiently infects CD4+ T cells and utilizes as a receptor CD134 (OX40), a member of the TNF superfamily that antagonizes regulatory T-cell (Treg) activity. Reactivation of HHV-6B has been associated with aberrant immune reconstitution and acute graft-versus-host disease (aGVHD) after HCT. Given that Treg counts are negatively correlated with aGVHD severity, we postulate that one mechanism for the poor CD4+ T-cell reconstitution observed shortly after transplant may be HHV-6B infection and depletion of peripheral (extra-thymic) CD4+ T cells, including a subpopulation of Treg cells. In turn, this may trigger a series of adverse events resulting in poor clinical outcomes such as severe aGVHD. In addition, recent evidence has linked HHV-6B reactivation with aberrant CD4+ T-cell reconstitution late after transplantation, which may be mediated by a different mechanism, possibly related to central (thymic) suppression of T-cell reconstitution. These observations suggest that aggressive management of HHV-6B reactivation in transplant patients may facilitate CD4+ T-cell reconstitution and improve the quality of life and survival of HCT patients.

Human Herpesvirus-6B Reactivation Is a Risk Factor for Grades II to IV Acute Graft-versus-Host Disease after Hematopoietic Stem Cell Transplantation: A Systematic Review and Meta-Analysis.

Graft-versus-host disease (GVHD) is an important cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Many studies have suggested that human herpesvirus-6B (HHV-6B) plays a role in acute GVHD (aGVHD) after HCT. Our objective was to systematically summarize and analyze evidence regarding HHV-6B reactivation and development of aGVHD. PubMed and EMBASE databases were searched using terms for HHV-6, HCT, and aGVHD, yielding 865 unique results. Case reports, reviews, articles focusing on inherited chromosomally integrated HHV-6, poster presentations, and articles not published in English were excluded. The remaining 467 articles were reviewed for the following requirements: a statistical analysis of HHV-6B reactivation and aGVHD was described, HHV-6B reactivation was defined by PCR, and blood (plasma, serum, or peripheral blood mononuclear cells) was used for HHV-6B PCR. Data were abstracted from publications that met these criteria (n = 33). Publications were assigned to 1 of 3 groups: (1) HHV-6B reactivation was analyzed as a time-dependent risk factor for subsequent aGVHD (n = 14), (2) aGVHD was analyzed as a time-dependent risk factor for subsequent HHV-6B reactivation (n = 1), and (3) analysis without temporal specification (n = 18). A statistically significant association (P < .05) between HHV-6B reactivation and aGVHD was observed in 10 of 14 studies (71%) in group 1, 0 of 1 study (0%) in Group 2, and 8 of 18 studies (44.4%) in Group 3. Of the 14 studies that analyzed HHV-6B as a risk factor for subsequent aGVHD, 11 performed a multivariate analysis and reported a hazard ratio, which reached statistical significance in 9 of these studies. Meta-analysis of these 11 studies demonstrated a statistically significant association between HHV-6B and subsequent grades II to IV aGVHD (hazard ratio, 2.65; 95% confidence interval, 1.89 to 3.72; P < .001). HHV-6B reactivation is associated with aGVHD, and when studies have a temporal component to their design, HHV-6B reactivation is associated with subsequent aGVHD. Further research is needed to investigate whether antiviral prophylaxis reduces incidence or severity of aGVHD.