CMV Infection in Hematopoietic Stem Cell Transplantation: Prevention and Treatment Strategies

Real-world safety of maribavir: a retrospective study based on signal detection in the FDA adverse event reporting system

BACKGROUND

Maribavir is a novel antiviral agent targeting cytomegalovirus through inhibition of the UL97 protein kinase, exhibiting a distinct mechanism of action. However, limited data are available on its safety profile post-marketing.

AIM

This study aimed to evaluate the adverse events (AEs) associated with maribavir using the Food and Drug Administration's Adverse Event Reporting System (FAERS), providing insights to inform clinical practice.

METHOD

We conducted a retrospective analysis of maribavir-related adverse event reports from the FAERS database, spanning the fourth quarter of 2021 to the second quarter of 2024. Signal detection was performed using four statistical methods: the proportional reporting ratio, reporting odds ratio, Bayesian confidence propagation neural network (BCPNN), and multi-item gamma Poisson shrinker.

RESULTS

A total of 1372 reports associated with maribavir were identified. Seven significant signals emerged at the system organ class level. At the preferred term level, 76 adverse events (AEs) demonstrated positive signals, including novel events such as pleural effusion, hypersomnia, and anosmia, alongside signals related to ear disorders. The majority of AEs were reported within the first month of maribavir use.

CONCLUSION

This study identified several new adverse event signals for maribavir, offering healthcare professionals a deeper understanding of its safety profile, which may guide safer clinical usage.

Protein-S-nitrosylation of human cytomegalovirus pp65 reduces its ability to undermine cGAS

Post-translational modifications (PTMs) are key regulators of various processes important for cell survival. These modifications are critical for dealing with stress conditions, such as those observed in disease states, and during infections with various pathogens. We previously reported that during infection of primary dermal fibroblasts, multiple human cytomegalovirus (HCMV)-encoded proteins were post-translationally modified by the addition of a nitric oxide group to cysteine residues, a modification called protein-S-nitrosylation. For example, tegument protein pp71 is nitrosylated, diminishing its ability to inhibit STING, a protein necessary for DNA virus immune response. Herein, we report that an additional HCMV tegument protein, pp65, responsible for the inhibition of cGAS is also modified by protein-S-nitrosylation on two cysteine residues. Utilizing site-directed mutagenesis to generate recombinant viruses that encode a pp65 that cannot be protein-S-nitrosylated, we evaluated the impact of this PTM on viral replication and how the virus impacts the cGAS/STING pathway. We report that the nitrosylation of pp65 negatively impacts its ability to block cGAS enzymatic functions. pp65 protein-S-nitrosylation mutants demonstrated a decrease in cGAS/STING-induced IRF3 and TBK1 phosphorylation. Additionally, we observed a reduction in IFN-β1 secretion in NuFF-1 cells expressing a nitrosylation-resistant pp65. We report that HCMV expressing a protein-S-nitrosylation-deficient pp65 is resistant to the activation of cGAS in the infection of primary dermal fibroblasts. Our work suggests that nitrosylation of viral proteins may serve as a broadly neutralizing mechanism in HCMV infection.

IMPORTANCE

Post-translational modifications (PTM) are utilized by host cells to limit an invading pathogen's ability to establish a productive infection. A potent PTM, called protein-S-nitrosylation, has anti-bacterial and anti-viral properties. Increasing protein-S-nitrosylation with the addition of nitric oxide donor compounds reduced HCMV replication in fibroblasts and epithelial cells. We previously reported that protein-S-nitrosylation of HCMV pp71 limits its ability to inhibit STING. Herein, we report that the protein-S-nitrosylation of HCMV pp65 impacts its ability to limit cGAS activity, an additional protein important in regulating interferon response. Therapeutically, patients provided nitric oxide by inhalation reduced viral replication in coronavirus disease 2019, influenza, and even impacted bacterial growth within patients' lungs. It is thought that an increase in free nitric oxide increases the frequency of nitrosylated proteins. Understanding how protein-S-nitrosylation regulates a common DNA virus like HCMV will provide insights into the development of broadly neutralizing therapeutics in drug-resistant viral infections.

Impact of Cytomegalovirus Reactivation Following Allogeneic Hematopoietic Cell Transplantation on the Relapse of Acute Leukemia

BACKGROUND

Cytomegalovirus (CMV) reactivation following allogeneic hematopoietic cell transplantation (HCT) is a significant complication; however, its impact on relapse remains controversial.

OBJECTIVES

This study aimed to evaluate the clinical impact of CMV reactivation on relapse and survival after HCT in patients with acute leukemia.

STUDY DESIGN

We conducted a retrospective analysis of 1258 patients diagnosed with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) who underwent their first HCT between 2000 and 2020.

RESULTS

Our cohort included 871 patients with AML and 387 patients with ALL. Among all patients, 751 (61.6%) experienced CMV reactivation within one year post-HCT. CMV reactivation was associated with HCT from unrelated donors, anti-thymocyte globulin use, and the occurrence of acute graft-versus-host disease. Notably, CMV reactivation was associated with a lower risk of relapse (HR, 0.713; P = .001) and improved event-free survival (HR, 0.743; P = .001) in both AML and ALL patients. However, there was no significant difference in non-relapse mortality or overall survival according to CMV reactivation.

CONCLUSION

These results suggest that CMV reactivation may prevent post-HCT relapse and enhance event-free survival in AML and ALL patients. Therefore, a CMV prophylaxis strategy is warranted to establish a safe range of CMV reactivation titers that can yield beneficial effects.

Evaluating the relationship between letermovir prophylaxis and medication regimen complexity Index over time in allogeneic hematopoietic stem cell transplant patients

BackgroundThe medication regimen complexity index (MRCI) quantifies patient-level regimen complexity, and higher scores are associated with adverse clinical outcomes. Characterization of regimens using the MRCI for allogeneic hematopoietic cell transplant (allo-HCT) recipients remains unexplored. Regimens may include letermovir which is used for cytomegalovirus prophylaxis and may prevent the need for addition of complex preemptive therapies. However, quantification of complexity in patients receiving letermovir has not been described.ObjectiveThis study aimed to compare MRCI scores over a one-year period in allo-HCT recipients who received letermovir prophylaxis versus those who did not.MethodsA retrospective analysis included adults who underwent allo-HCT from January 1, 2016 to October 31, 2021. MRCI scores were calculated at admission, discharge, day +100, 6 months, and 1-year post-transplant.ResultsA total of 218 patients were included, with 67 receiving letermovir and 151 not receiving letermovir. Median MRCI scores were comparable at discharge post allo-HCT (23 [10-39] vs 22 [12-37], p = 0.97). However, at day +100, patients in the letermovir group exhibited significantly higher median scores compared to the non-letermovir group (59 [46-74] vs 50 [37-67], p = 0.009). By 1-year post allo-HCT, no significant difference in scores was observed between groups (47 [30-68] vs 41 [27-61], p = 0.12).Conclusion and RelevanceThis study revealed increased MRCI scores up to one year after transplantation in allo-HCT recipients receiving letermovir. The nonrandomized study design and potential patient differences between groups complicate the interpretation of the findings. Future analyses should aim to account for these differences.

Immune reconstitution of human cytomegalovirus-specific T lymphocytes after allogeneic hematopoietic stem cell transplantation and their predictive role in reactivation

Human cytomegalovirus (HCMV) is the most common virus to affect the recipients of allogeneic hematopoietic stem cell transplantation (allo-HSCT). HCMV reactivation increases the risk of secondary fungal and bacterial infections, as well as that of non-relapse mortality after allo-HSCT. This study investigates the post-transplantation reconstitution of HCMV-specific T cells and their role in the regulation of HCMV infections. Peripheral blood samples from CMV-seropositive allo-HSCT recipients (R+) and CMV-seropositive donors (D+) were collected from October 2019 to June 2021. Continuous quantification and function monitoring of CMV-specific CD4+/CD8+T lymphocytes were performed by flow cytometry after stimulation in an HCMV-pp65 pool in vitro and intracellular cytokine staining was performed. Plasma CMV-DNA was quantitatively detected by qPCR. The median age of patients (n = 131) was 34 (23-45) years. Post-transplantation HCMV reactivation occurred in 88 (67.2%) patients. HCMV-responsive CD4+T cells in non-HCMV reactivation patients was significantly higher than that in HCMV reactivation patients 30 days after transplantation (0.21 cells/μL vs 0.10 cells/μL; P = 0.005). Kaplan-Meier analysis showed that the incidence of HCMV reactivation in patients with low levels of HCMV-responsive CD4+T cells (<0.14 cells/μL) was significantly higher than that in patients with high levels of HCMV-responsive CD4+T cells (>0.14 cells/μL) (83.9% vs 54.7%; P < 0.001). Patients lacking HCMV-responsive CD8+T cells (<2 cells/μL) 60 days after allo-HSCT had a significantly higher risk of HCMV reactivation 100 days after transplantation (HR 9.932; P = 0.005). Patient age and the mononuclear cell-infusion level were correlated with the reconstructive levels of HCMV-responsive CD8+T cells 60 days after transplantation. Poor recovery of HCMV-responsive CD4+T cells 30 days post-transplantation is closely related to the risk of HCMV reactivation. The level of HCMV-responsive CD8+T cells 60 days post-transplantation is a good predictor for late-onset HCMV reactivation, which is particularly important for outpatient monitoring and management of patients with allo-HSCT, and facilitates individualized risk stratification for HCMV reactivation.

Efficacy and Safety of Letermovir for Cytomegalovirus Prophylaxis in Pediatric Hematopoietic Stem Cell Transplantation Recipients: A Systematic Review, Meta-Analysis, and Meta-Regression

OBJECTIVE

Letermovir (LTV) is a novel antiviral agent approved by the FDA in 2017 for CMV prophylaxis in adult CMV-seropositive allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients and approved for pediatric use in 2024. This study systematically evaluates the efficacy and safety of LTV prophylaxis for CMV infection in pediatric allo-HSCT recipients.

METHODS

We systematically searched PubMed, Scopus, Web of Science, Embase, and Cochrane Library up to December 2024 for studies that evaluated the use of LTV prophylaxis in pediatric allo-HSCT recipients. We conducted single-arm meta-analysis using Open Meta Analyst software and double-arm meta-analysis using R Studio. We pooled the dichotomous outcomes as event and total using the fixed-effects model.

RESULTS

Twelve articles were included in the analysis. The single-arm meta-analysis indicated that the prophylactic use of LTV against CMV among pediatrics was associated with a 10.9% (95% CI: 0.065, 0.153) infection rate without any disease occurrence. The percentage of patients who discontinued the drug due to adverse reactions was only 2.4% (95% CI: 0.003, 0.045), and all-cause mortality was 7.9% (95% CI: 0.032, 0.126). The double-arm meta-analysis results indicated that the incidence of CMV infection was significantly lower in the LTV group in comparison to the control group (RR: 0.29; 95% CI: 0.16, 0.56; p < 0.001).

CONCLUSION

LTV has demonstrated safety and efficacy in preventing CMV infection and disease among high-risk pediatric patients. Future large scale randomized trials are necessary to validate the findings.

M1 enrichment facilitates virus detection in patients with allogeneic hematopoietic stemcell transplantation

Due to the severe consequences of viral infection in allogeneic hematopoietic stem cell transplantation (allo-HSCT) patients, the routine use of polymerase chain reaction (PCR) screening of viruses is common in clinic, while the sensitivities of molecular methods are not always sufficient for blood samples. We aimed to increase the detection efficiency of viremia in allo-HSCT patients with M1 bead enrichment. Blood samples of allo-HSCT patients with fever were collected. Simultaneously with analyses of real-time PCR without enrichment, M1 bead enrichment followed by real-time PCR was applied to detect possible viruses in these samples, and metagenomic next-generation sequencing analyses were also applied in 10 samples negative with real-time PCR without enrichment. Various species of viruses were detected with M1 enrichment method. Significantly, some viruses that had not been found by real-time PCR without M1 enrichment were also detected by those with M1 enrichment and verified by metagenomic next-generation sequencing analyses. Furthermore, blood samples enriched with M1 beads had lower Ct values of real-time PCR assay than those that had not been treated. In conclusion, M1 bead enrichment increased the detection efficiency of most viruses in hematological malignancy patients.

Viral Metagenomics in Patients Who Underwent Allogeneic Hematopoietic Stem Cell Transplantation (HSCT): A Brazilian Experience

Viral infections are one of the most important causes of morbidity and mortality among patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Immunosuppression may lead to the reactivation of latent viruses or the acquisition of new infections, resulting in severe clinical outcomes. The early detection of viral reactivations is crucial for effective patient management and post-transplant care. In this study, we employed next-generation metagenomics to assess changes in viral abundance and detect clinically significant viruses in allogeneic HSCT patients. A total of 20 patients from the Transplant Unit of the University Hospital of the Faculty of Medicine of Ribeirão Preto, University of São Paulo were included, with plasma samples collected at three time points: D + 0 (pre-transplantation), D + 30 (30 days post-transplantation), and D + 100 (~100 days post-transplantation). A higher presence of clinically relevant viruses, such as the cytomegalovirus (CMV), the Epstein-Barr virus (EBV) and adenoviruses, were predominantly detected at D + 30. The diversity of commensal viruses, primarily anelloviruses, increased gradually, with the highest abundance and variability detected at D + 100. Viruses with clinical importance for HSCT, including CMV, adenovirus and EBV, were confirmed and characterized at the molecular level, showing generally high cycle threshold values. Our findings demonstrate a rise in anellovirus abundance following allogeneic HSCT, with the highest levels observed at D + 100. Notably, D + 30 was identified as a critical time point for the reactivation of clinically significant viruses. This study underscores the potential of metagenomics in the identification of clinically relevant viruses and highlights the importance of monitoring latent viruses in immunocompromised populations, including allogeneic HSCT patients.

Role of cytomegalovirus reactivation on relapse after allogeneic hematopoietic stem cell transplantation in acute lymphoblastic leukemia

Cytomegalovirus reactivation (CMV-R) is a frequent complication post-allogeneic hematopoietic stem cell transplantation (allo-HSCT), associated with poor outcomes. Previous studies have demonstrated the protective effect of CMV-R against relapse after allo-HSCT for acute myeloblastic leukemia (AML). However, this impact remains unclear in acute lymphoblastic leukemia (ALL). We conducted a retrospective study on 81 patients with ALL who received allo-HSCT after myeloablative conditioning regimen from matched sibling donors between 2016 and 2022. All patients underwent weekly monitoring for CMV-R by quantitative polymerase chain reaction assay from engraftment until day +100 post allo-HSCT, and received antiviral prophylaxis with acyclovir from day +1 to 6 months after allo-HSCT. Preemptive treatment was initiated when a viremia was higher than 150 copies/mL. The median age was 20 years (range, 5-50 years). After allo-HSCT, 35% of patients developed CMV-R after a median of 39 days (range, 19-100 days). After a median follow-up of 30 months (range, 1-93 months), CMV-R was an independent factor associated with lower cumulative incidence of relapse (CIR) (OR: 0.17; 95% CI [0.03 - 0.98], p = 0.04) without survival benefit. Further studies are needed to validate the protective effect of CMV-R on ALL relapse.

Antiviral Stewardship in Transplantation

Though antimicrobial stewardship programs (ASPs) are required for hospitals, the involvement of transplant recipients in programmatic interventions, protocols, and metrics has historically been limited. Though there is a growing interest in studying stewardship practices in transplant patients, optimal practices have not been clearly established. A component of ASPs, antiviral stewardship (AVS), specifically targeting cytomegalovirus (CMV), has been more recently described. Understanding AVS opportunities and interventions is particularly important for transplant recipients, given the morbidity and mortality associated with viral infections, challenging clinical syndromes, ultrasensitive molecular diagnostic assays, antiviral resistance, and costs of viral disease and medications, as well as antiviral drug toxicities. This review highlights opportunities for AVS for CMV, EBV, HSV, VZV, SARS-CoV-2, respiratory syncytial virus, and BK polyomavirus in transplant patients.

Cytomegalovirus Infections in Hematopoietic Stem Cell Transplant: Moving Beyond Molecular Diagnostics to Immunodiagnostics

Human CMV, regularly reactivated by simple triggers, results in asymptomatic viral shedding, powerful cellular immune responses, and memory inflation. Immunocompetent individuals benefit from a robust immune response, which aids in viral management without causing clinically significant illness; however, immunodeficient individuals are always at a higher risk of CMV reactivation and disease. Hematopoietic stem cell transplant (HSCT) recipients are consistently at higher risk of CMV reactivation and clinically significant CMV illness due to primary disease, immunosuppression, and graft vs. host disease. Early recovery of CMV-CMI responses may mitigate effects of viral reactivation in HSCT recipients. Immune reconstitution following transplantation occurs spontaneously and is mediated initially by donor-derived T cells, followed by clonal growth of T cells produced from graft progenitors. CMV-specific immune reconstitution post-transplant is related to spontaneous clearance of CMV reactivation and may eliminate the need for prophylactic or pre-emptive medication, making it a potential predictive marker for monitoring CMV reactivation. This review highlights current thoughts and therapeutic options for CMV reactivation in HSCT, with focus on CMV immune reconstitution and post-HSCT monitoring. Immune monitoring aids in risk stratification of transplant recipients who may progress from CMV reactivation to clinically significant CMV infection. Implementing this approach in clinical practice reduces the need for periodic viral surveillance and antiviral therapy in recipients who have a high CMV-CMI and thus may experience self-limited reactivation. Therefore, in the age of precision medicine, it is critical to incorporate CMV-specific cellular immune surveillance into conventional procedures and algorithms for the management of transplant recipients.

Cytomegalovirus infection risk with alemtuzumab therapy in hematological malignancies: a retrospective cohort study in the non-transplant setting

Alemtuzumab is a potent lymphocyte-depleting immunotherapy used in solid organ transplan-tation (SOT), that is increasingly being applied in diverse lymphoproliferative disorders (LPDs). However, a significant toxicity limiting expanded usage is cytomegalovirus (CMV) infection, for which standardized preventive strategies exist in SOT but not in LPDs due to a poor understanding of infection risk in this population, with early LPD studies largely limited to stem cell transplantation. Using one of the most diverse arrays of LPDs studied to date, our retrospective cohort study of non-transplant patients receiving alemtuzumab over a ten-year period at a large regional cancer center examines the incidence and clinical profile of infected patients. Among 24 patients, we identified a composite CMV infection rate of 42% with a symptomatic rate of 21%. We also noted significant variations in preventive strategies, which alongside a high infection rate presents an opportunity to improve outcomes through further work in standardization.

Pneumonia in Transplant Recipients: A Comprehensive Review of Diagnosis and Management

Transplant recipients have an increased risk of complications, including graft dysfunction and infections, which can be life-threatening if not recognized early. Pneumonia ranks as one of the most frequent complications in both solid organ and hematopoietic stem cell transplants. Clinical symptoms manifest late during infections in immunocompromised patients. An aggressive approach centered on early confirmatory diagnosis and a low threshold for empiric therapy is often the most effective strategy. The isolation of a pathogen in an upper airway sample does not necessarily mean the same organism is responsible for pneumonia. Viruses such as CMV (cytomegalovirus virus) may function as co-pathogens for opportunistic infections in transplant recipients in addition to causing their own primary infectious syndrome. Furthermore, some viruses exhibit immunomodulatory effects that can affect the graft function. Given the exhaustive list of causative pathogens responsible for pneumonia, the best approach to the diagnosis is to have a conceptual framework that includes a detailed history, such as the type of transplant, degree of immunosuppression, antimicrobial prophylaxis, risk factors, time of presentation since transplantation and the radiographic pattern on the CT chest (computer tomography of the chest). Management depends predominantly on the degree of antimicrobial resistance, drug-to-drug interaction, and adjustments to the immunosuppression.

Use of Specific T Lymphocytes in Treating Cytomegalovirus Infection in Hematopoietic Cell Transplant Recipients: A Systematic Review

Cytomegalovirus (CMV) poses a significant threat to post-hematopoietic cell transplantation (HCT). Control strategies include letermovir prophylaxis or ganciclovir pre-emptive therapy (PET). Without prophylaxis, 65-90% of seropositive recipients develop a clinically significant CMV infection. Due to PET drawbacks, letermovir prophylaxis is preferable, as it reduces CMV-related events and improves overall survival. However, refractory or resistant CMV-CS remains a challenge, with maribavir showing limited efficacy. This systematic review followed the Cochrane Manual and PRISMA guidelines and was registered in PROSPERO. Searches were conducted in PubMed, Scopus, Embase, and Web of Science. Out of 1895 identified records, 614 duplicates were removed, and subsequent screening excluded 1153 studies. Eleven included studies (2012-2024) involved 255 HCT recipients receiving adoptive immunotherapy (AI), primarily CMV-specific T-cell therapy. GvHD occurred in 1.82% of cases. Adverse events occurred in 4.4% of cases, while mild CRS was observed in 1.3% of patients. Efficacy, evaluated in 299 patients across eleven studies, showed an average response rate of 78.2%. CMV-CS recurrence was observed in 24.4% of 213 patients, and death due to CMV was reported in 9.7% of 307 patients across nine studies. Adoptive hCMV-specific T-cell immunotherapy appears to be a safe, effective alternative for refractory CMV-CS in HCT.

The Management of Hematopoietic Stem Cell Transplant in People with HIV

Hematopoietic stem cell transplant (HSCT) is now recognized as a standard treatment option for people with HIV (PWH) who develop high-risk hematologic malignancies. However, the involved polypharmacy can lead to complications from drug interactions and toxicities, affecting the efficacy and safety of chemotherapy and antiretroviral therapy (ART). Managing these patients requires a personalized approach, including the careful selection of ART based on previous therapies and potential interactions, alongside risk assessment for infections. This discussion will address the history of HSCT in PWH and management considerations for this group.

Antiviral Agents for Preventing Cytomegalovirus Disease in Recipients of Hematopoietic Cell Transplantation

This systematic review discusses the use of prophylaxis to prevent cytomegalovirus (CMV) infection in recipients who have undergone hematopoietic cell transplantation. It highlights the need for new approaches to control and prevent CMV infection. The approval of the anti-CMV drug letermovir has made antiviral prophylaxis more popular. CMV-specific T cell-mediated immunity tests are effective in identifying patients who have undergone immune reconstitution and predicting disease progression. Maribavir (MBV) has been approved for the treatment of post-transplant CMV infection/disease in adolescents. Adoptive T-cell therapy and the PepVax CMV vaccine show promise in tackling refractory and resistant CMV. However, the effectiveness of PepVax in reducing CMV viremia/disease was not demonstrated in a phase II trial. Cell-mediated immunity assays are valuable for personalized management plans, but more interventional studies are needed. MBV and adoptive T-cell therapy are promising treatments, and trials for CMV vaccines are ongoing.

Treatment outcome at the pediatric stem cell transplantation center in Syria: A single-center experience

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is a therapeutic approach known for its high success rates in treating various hematologic malignancies, hemoglobinopathies, immune deficiencies, and other disorders. Notably, pediatric HSCT commenced in Syria in 2021 amidst the prevailing crisis. This study aims to assess the demographic and clinical profiles of pediatric patients who underwent stem cell transplantation and to analyze treatment outcomes at Syria's inaugural pediatric HSCT center.

METHODS

This study is a single-center retrospective analysis of 25 pediatric patients who underwent HSCT underage of 14 years in the National Stem Cell Center (HAYAT) in Damascus within the period 2021-2023. The databases were created based on data that were collected from patient medical records.

RESULTS

In autologous patients, transplant-related mortality (TRM) was 0%, with 4 (57%) experiencing disease relapse, resulting in the death of one patient. Additionally, 3 (42.8%) of patients remain alive under second-line management. The overall survival rate was 6 (85.7%), and the disease-free survival rate was 16 (88%). In allogeneic patients, TRM was 5.5% (1/18). One allogeneic patient experienced disease relapse and subsequently died. The overall survival rate and disease-free survival rate were 16 (88%).

CONCLUSIONS

The objective of this study was to assess the outcomes of pediatric HSCT patients who have undergone transplantation thus far. Given the recent initiation of pediatric stem cell transplantation in Syria, our dataset provides a basis for comparison with international hematopoietic stem cell transplantation centers regarding treatment complications and outcomes, notwithstanding the challenges and crises faced within our country.

Characterization of recurrent cytomegalovirus reactivations post allogenic stem cell transplantation in a population with high seropositivity

OBJECTIVES

This study aimed to characterize incidences of CMV reactivations within one year post-allo-SCT and identify risk factors for CMV second reactivation episode in population with high seropositivity where first CMV reactivation episode deemed to be high.

METHODS

This retrospective cohort study analyzed data from 359 allo-SCT patients aged 14 and older admitted to a tertiary academic hospital. Data on demographic and clinical factors, CMV serostatus, conditioning regimens, graft-versus-host disease prophylaxis, engraftment time, and CMV reactivations were collected.

RESULTS

First and second CMV reactivations occurred in 88.9% and 18.4% of post-allo-SCT patients respectively. Patients were stratified into two groups based on primary disease necessitating allo-SCT, patients with malignant (Group 1) and non-malignant (Group 2) hematological disease. Factors associated with the second reactivation included cord blood as a stem cell source, human leukocyte antigen mismatch, acute graft-versus-host disease, and hematological malignancies. Patients with non-malignant hematological disease displayed better outcomes, including a higher rate of spontaneous clearance of first CMV reactivation (70% versus 49.4%) and lower rates of second CMV reactivation (9.6% versus 31%) than those with malignant hematological disease. The one-year overall survival rate was 87.7% (95.5% in non-malignant hematological disease and 78.13% in malignant hematological disease).

CONCLUSION

Our findings are concordant with previous local study in regard to high rate of first CMV reactivation post-allo-SCT. It appears that patients with nonmalignant hematological disease had better outcomes, such as lower second CMV reactivation and higher survival rates compared to patients with malignant hematological disease. Further investigation is needed to identify other factors affecting recurrent CMV reactivations in allo-SCT in patients with malignant hematological disease.

Approaches and Challenges in the Current Management of Cytomegalovirus in Transplant Recipients: Highlighting the Role of Advanced Practice Providers (Nurse Practitioners and Physician Assistants)

Cytomegalovirus (CMV) infection is associated with increased morbidity and mortality in hematopoietic cell transplant (HCT) and solid organ transplant (SOT) recipients, with traditional anti-CMV therapies limited by their associated toxicities and the development of resistance. Clinical providers are often faced with challenging and complicated CMV infections that require multiple courses of antiviral therapies. Increasingly, advanced practice providers (APPs) are playing an important role in the day-to-day management of transplant recipients with CMV infection, including resistant/refractory CMV and other complex CMV syndromes. Here, we provide an overview of current preventative and treatment strategies for CMV infection in HCT and SOT recipients, highlighting the challenging aspects of current management and the potential utility of newer antiviral agents. This article also focuses on how a multidisciplinary team, orchestrated by APPs, can improve CMV-associated patient outcomes. Protocols using antiviral agents for the prevention or treatment of CMV infections require carefully designed and meticulously implemented strategies to ensure the best clinical outcomes for patients. APPs, who have increasingly become the frontline providers of outpatient care for transplant recipients, are ideally positioned to design and carry out these protocols.

In Vitro Profiling of Commonly Used Post-transplant Immunosuppressants Reveals Distinct Impact on Antiviral T-cell Immunity Towards CMV

Infectious complications, including widespread human cytomegalovirus (CMV) disease, frequently occur after hematopoietic stem cell and solid organ transplantation due to immunosuppressive treatment causing impairment of T-cell immunity. Therefore, in-depth analysis of the impact of immunosuppressants on antiviral T cells is needed. We analyzed the impact of mTOR inhibitors sirolimus (SIR/S) and everolimus (EVR/E), calcineurin inhibitor tacrolimus (TAC/T), purine synthesis inhibitor mycophenolic acid (MPA/M), glucocorticoid prednisolone (PRE/P) and common double (T+S/E/M/P) and triple (T+S/E/M+P) combinations on antiviral T-cell functionality. T-cell activation and effector molecule production upon antigenic stimulation was impaired in presence of T+P and triple combinations. SIR, EVR and MPA exclusively inhibited T-cell proliferation, TAC inhibited activation and cytokine production and PRE inhibited various aspects of T-cell functionality including cytotoxicity. This was reflected in an in vitro infection model, where elimination of CMV-infected human fibroblasts by CMV-specific T cells was reduced in presence of PRE and all triple combinations. CMV-specific memory T cells were inhibited by TAC and PRE, which was also reflected with double (T+P) and triple combinations. EBV- and SARS-CoV-2-specific T cells were similarly affected. These results highlight the need to optimize immune monitoring to identify patients who may benefit from individually tailored immunosuppression.

Letermovir for Cytomegalovirus infection in pediatric patients undergoing allogenic hematopoietic stem cell transplantation: a real-life study by the Infectious Diseases Working Group of Italian Association of Pediatric Hematology-Oncology (AIEOP)

Letermovir prophylaxis revolutionized the approach to Cytomegalovirus infection in adult hematopoietic stem cell transplant (HCT), while data in pediatric setting are still lacking. We retrospectively analyzed 87 HCT children transplanted in 11 AIEOP centers receiving letermovir as off-label indication between January 2020 and November 2022. Letermovir was used as primary, secondary prophylaxis or CMV treatment in 39, 26 and 22 cases, respectively; no discontinuation due to toxicity was reported. Median duration was 100 days (14-256) for primary and 96 days (8-271) for secondary prophylaxis, respectively. None of the patients experienced CMV-clinically significant reactivation during Letermovir primary prophylaxis; one patient developed breakthrough infection during secondary prophylaxis, and 10 and 1 patient experienced asymptomatic CMV-reactivation and CMV-primary infection after drug discontinuation, respectively. Median duration of letermovir in CMV treatment was 40 days (7-134), with 4/22 patients suffering CMV-pneumonia, with an overall response rate of 86.4%. With a median follow-up of 10.7 months (8.2-11.8), estimated 1-year overall survival was 86%; no CMV-related deaths were reported in prophylaxis groups. This is the largest report on Letermovir use in pediatric HCT; real-life data confirm an excellent toxicity profile, with high efficacy as CMV prophylaxis; results in CMV-infection treatment should be investigated in larger, prospective trials.

Treatment for First Cytomegalovirus Infection Post-Hematopoietic Cell Transplant in the AURORA Trial: A Multicenter, Double-Blind, Randomized, Phase 3 Trial Comparing Maribavir With Valganciclovir

BACKGROUND

Neutropenia may limit the use of valganciclovir treatment for cytomegalovirus (CMV) infection following hematopoietic cell transplant (HCT). A phase 2 study indicated efficacy of maribavir with fewer treatment-limiting toxicities than valganciclovir.

METHODS

In this multicenter, double-blind, phase 3 study, patients with first asymptomatic CMV infection post-HCT were stratified and randomized 1:1 to maribavir 400 mg twice daily or valganciclovir (dose-adjusted for renal clearance) for 8 weeks with 12 weeks of follow-up. The primary endpoint was confirmed CMV viremia clearance at week 8 (primary hypothesis of noninferiority margin of 7.0%). The key secondary endpoint was a composite of the primary endpoint with no findings of CMV tissue-invasive disease at week 8 through week 16. Treatment-emergent adverse events (TEAEs) were assessed.

RESULTS

Among patients treated (273 maribavir; 274 valganciclovir), the primary endpoint of noninferiority of maribavir was not met (maribavir, 69.6%; valganciclovir, 77.4%; adjusted difference: -7.7%; 95% confidence interval [CI]: -14.98, -.36; lower limit of 95% CI of treatment difference exceeded -7.0%). At week 16, 52.7% and 48.5% of patients treated (maribavir and valganciclovir, respectively) maintained CMV viremia clearance without tissue-invasive disease (adjusted difference: 4.4%; 95% CI: -3.91, 12.76). With maribavir (vs valganciclovir), fewer patients experienced neutropenia (16.1% and 52.9%) or discontinued due to TEAEs (27.8% and 41.2%). Discontinuations were mostly due to neutropenia (maribavir, 4.0%; valganciclovir, 17.5%).

CONCLUSIONS

Although noninferiority of maribavir to valganciclovir for the primary endpoint was not achieved based on the prespecified noninferiority margin, maribavir demonstrated comparable CMV viremia clearance during post-treatment follow-up, with fewer discontinuations due to neutropenia. Clinical Trials Registration. NCT02927067 [AURORA].

A time trade-off study to determine health-state utilities of transplant recipients with refractory cytomegalovirus infection with or without resistance

BACKGROUND

Health-state utility values (HSUVs) for post-transplant refractory cytomegalovirus (CMV) infection (with or without resistance [R/R]) were determined using a time trade-off (TTO) survey completed by 1,020 members of the UK general public.

METHODS

Existing literature and qualitative interviews with clinicians experienced in treating R/R CMV were used to develop initial draft vignettes of health states. The vignettes were refined to describe three clinical states of R/R CMV: clinically significant and symptomatic (CS-symptomatic CMV); clinically significant and asymptomatic (CS-asymptomatic CMV); and non-clinically significant (non-CS CMV). Each clinical state was valued independently and combined with three events of interest: graft-versus-host disease; kidney graft loss; and lung graft loss to generate twelve vignettes. The final vignettes were evaluated by a sample of the UK general public using an online TTO survey. Exclusion criteria were applied to the final data to ensure that responses included in the analysis met pre-defined quality control criteria.

RESULTS

Overall, 738 participants met the inclusion criteria and were included in the analysis. The sample was representative of the UK general population in terms of age and sex. Non-CS CMV had the highest mean HSUV (95% confidence interval) (0.815 [0.791, 0.839]), followed by CS-asymptomatic CMV (0.635 [0.602, 0.669]), and CS-symptomatic CMV (0.443 [0.404, 0.482]). CS-symptomatic CMV with lung graft loss had the lowest mean HSUV (0.289), with none of the health states considered on average worse than dead.

CONCLUSIONS

Post transplant R/R CMV has substantial impact on the health-related quality of life of patients. The utility values obtained in this study may be used to support economic evaluations of therapies for R/R CMV infection.

'Getting Better'-Is It a Feasible Strategy of Broad Pan-Antiherpesviral Drug Targeting by Using the Nuclear Egress-Directed Mechanism?

The herpesviral nuclear egress represents an essential step of viral replication efficiency in host cells, as it defines the nucleocytoplasmic release of viral capsids. Due to the size limitation of the nuclear pores, viral nuclear capsids are unable to traverse the nuclear envelope without a destabilization of this natural host-specific barrier. To this end, herpesviruses evolved the regulatory nuclear egress complex (NEC), composed of a heterodimer unit of two conserved viral NEC proteins (core NEC) and a large-size extension of this complex including various viral and cellular NEC-associated proteins (multicomponent NEC). Notably, the NEC harbors the pronounced ability to oligomerize (core NEC hexamers and lattices), to multimerize into higher-order complexes, and, ultimately, to closely interact with the migrating nuclear capsids. Moreover, most, if not all, of these NEC proteins comprise regulatory modifications by phosphorylation, so that the responsible kinases, and additional enzymatic activities, are part of the multicomponent NEC. This sophisticated basis of NEC-specific structural and functional interactions offers a variety of different modes of antiviral interference by pharmacological or nonconventional inhibitors. Since the multifaceted combination of NEC activities represents a highly conserved key regulatory stage of herpesviral replication, it may provide a unique opportunity towards a broad, pan-antiherpesviral mechanism of drug targeting. This review presents an update on chances, challenges, and current achievements in the development of NEC-directed antiherpesviral strategies.

Refractory human cytomegalovirus infection without evidence of genetic resistance in the UL-54 and UL-97 genes in a pediatric hematopoietic stem cell transplant recipient: a case report

Cytomegalovirus (CMV) infection is a common complication in patients undergoing hematopoietic stem cell transplantation (HSCT). Management of refractory CMV infections, especially in developing countries, can be challenging due to the limited availability of second and third-line antiviral drugs or alternative treatments. Here, we present a case of an 8 years-old patient diagnosed with acute myeloid leukemia. Eight months post-diagnosis, the patient underwent TCR-αβ+/CD19+-depleted haploidentical HSCT. Both the donor and recipient tested positive for anti-CMV IgG and negative for IgM antibodies. Before transplantation, the patient received CMV prophylaxis in the form of intravenous ganciclovir. Post-transplantation, the patient exhibited oscillating CMV viral loads and was diagnosed with a refractory infection. Treatment with ganciclovir, foscarnet, and cidofovir was unsuccessful. Sequencing of UL-54 and UL-97 genes was performed to rule out potential resistance to first-line treatment. Ten months after the HSCT, the child died from hypovolemic shock due to gastrointestinal bleeding. This is the first case reported in Peru and Latin America of a refractory CMV infection in a pediatric HSCT recipient without evidence of clinical symptoms and CMV genetic resistance. This case demonstrates the need for alternative treatments to manage refractory CMV infections, especially in haploidentical HSCT cases where drug resistance is frequent (~15%). Furthermore, this case highlights the importance of using highly sensitive genetic tools to detect mutations associated with virus resistance in a broader range of the viral genome.

A Systematic Literature Review to Identify Diagnostic Gaps in Managing Immunocompromised Patients With Cancer and Suspected Infection

Patients with cancer are increasingly vulnerable to infections, which may be more severe than in the general population. Improvements in rapid and timely diagnosis to optimize management are needed. We conducted a systematic literature review to determine the unmet need in diagnosing acute infections in immunocompromised patients with cancer and identified 50 eligible studies from 5188 records between 1 January 2012 and 23 June 2022. There was considerable heterogeneity in study designs and parameters, laboratory methods and definitions, and assessed outcomes, with limited evaluation of diagnostic impact on clinical outcomes. Culture remains the primary diagnostic strategy. Fewer studies employing molecular technologies exist, but emerging literature suggests that pathogen-agnostic molecular tests may add to the diagnostic armamentarium. Well-designed clinical studies using standardized methodologies are needed to better evaluate performance characteristics and clinical and economic impacts of emerging diagnostic techniques to improve patient outcomes.

A new direction for cytomegalovirus prophylaxis among transplant recipients: Benefits and nonviral outcomes of letermovir use as primary CMV prophylaxis

PURPOSE OF REVIEW

Letermovir has changed the game of primary prophylaxis against cytomegalovirus (CMV) for hematopoietic stem cell transplant (HSCT) and more recently, solid organ transplant recipients. This is largely due to letermovir's similar efficacy in protecting against CMV reactivation and disease, along with its superior safety profile, notably reduced myelotoxicity, and lack of renal dose adjustment compared to standard agents like valganciclovir. This review will describe the potential benefits and clinical considerations of letermovir as prophylaxis among transplant recipients, with a focus on recent evidence describing nonviral outcomes of CMV.

RECENT FINDINGS

Recent evidence has demonstrated improved safety (e.g., less myelosuppression) and tolerability with no difference in rates of CMV infection or disease in kidney transplant recipients given letermovir compared to valganciclovir. Real-world studies and meta-analyses in HSCT populations have explored various nonviral outcomes with letermovir use. Letermovir prophylaxis was associated with reduced mortality, lower rates of graft versus host disease, delayed CMV immune reconstitution, improved tolerability with extended durations, and decreased healthcare utilization.

SUMMARY

Letermovir is an effective antiviral agent for CMV prevention and has demonstrated enhanced safety, which may allow for extended durations of primary prophylaxis among transplant recipients along with other improved clinical outcomes by mitigating the indirect effects of CMV.

Circulating cytokine and chemokine patterns associated with cytomegalovirus reactivation after stem cell transplantation

Objectives

Human cytomegalovirus (HCMV) reactivation is the leading viral complication after allogeneic haematopoietic stem cell transplantation (allo-HSCT). Understanding of circulating cytokine/chemokine patterns which accompany HCMV reactivation and correlate with HCMV DNAemia magnitude is limited. We aimed to characterise plasma cytokine/chemokine profiles in 36 allo-HSCT patients (21 with HCMV reactivation and 15 without HCMV reactivation) at four time-points in the first 100-day post-transplant.

Methods

The concentrations of 31 cytokines/chemokines in plasma samples were analysed using a multiplex bead-based immunoassay. Cytokine/chemokine concentrations were compared in patients with high-level HCMV DNAemia, low-level HCMV DNAemia or no HCMV reactivation, and correlated with immune cell frequencies measured using mass cytometry.

Results

Increased plasma levels of T helper 1-type cytokines/chemokines (TNF, IL-18, IP-10, MIG) were detected in patients with HCMV reactivation at the peak of HCMV DNAemia, relative to non-reactivators. Stem cell factor (SCF) levels were significantly higher before the detection of HCMV reactivation in patients who went on to develop high-level HCMV DNAemia (810-52 740 copies/mL) vs. low-level HCMV DNAemia (< 250 copies/mL). High-level HCMV reactivators, but not low-level reactivators, developed an elevated inflammatory cytokine/chemokine profile (MIP-1α, MIP-1β, TNF, LT-α, IL-13, IL-9, SCF, HGF) at the peak of reactivation. Plasma cytokine concentrations displayed unique correlations with circulating immune cell frequencies in patients with HCMV reactivation.

Conclusion

This study identifies distinct circulating cytokine/chemokine signatures associated with the magnitude of HCMV DNAemia and the progression of HCMV reactivation after allo-HSCT, providing important insight into immune recovery patterns associated with HCMV reactivation and viral control.

QuantiFERON-CMV and monitor predict cytomegalovirus, mortality, and graft-versus-host disease in transplant recipients

Cytomegalovirus (CMV) is the most prevalent infection in recipients of hematopoietic stem cell transplant (HSCT). QuantiFERON-CMV (QF-CMV) and QuantiFERON-Monitor (QFM) assays were used to test whether immune-competent adult allogeneic HSCT recipients with CMV-specific T cells can control CMV infection or reactivation. Our data demonstrated a significant correlation between CMV infection measured by CMV-antigenemia test and QF-CMV results, graft versus host disease (GvHD), and mortality rates. The QF-CMV test revealed that CMV-specific T cells with higher interferon-γ (IFN-γ) release were correlated with lower CMV infection rates. There was a significant negative association between QF-CMV results, GvHD, and mortality rates. Data showed that a one-unit rise in IFN-γ was linked with a 12.7% reduction in GvHD and a 20.7% reduction in the mortality odds ratio. In addition, a negative correlation was found between QF-M results and CMV infection, with the QFM test predicting protection against CMV infection by 1.9%. This is one of the few studies establishing the QF-CMV test's predictive value for GvHD and mortality, its use to monitor HSCT patients for pre-emptive therapy, and the use of the QFM test to predict CMV infection and mortality in HSCT patients. Thus, these assays could be utilized to optimize preventive and pre-emptive therapy procedures to reduce transplant recipient adverse effects and posttransplant therapy costs.

Letermovir for Cytomegalovirus prophylaxis in pediatric hematopoietic stem cell transplantation

BACKGROUND

Letermovir (LTV), an antiviral with exclusive activity against Cytomegalovirus (CMV), is approved for prophylaxis of CMV infection and disease in adult hematopoietic cell transplant (HCT) patients. The use of LTV in the pediatric HCT population is off-label, and has limited literature to support its use.

PROCEDURE

This was a single-center, retrospective, matched (1:1 LTV:non-LTV) cohort study of allogeneic HCT recipients transplanted at Children's Hospital Colorado from 2015 to 2022. The primary endpoint was clinically significant CMV DNAemia (defined as a CMV viral load >1000 copies/mL or any CMV DNAemia leading to preemptive treatment) through 6 months post transplant. Secondary outcomes included time to clinically significant CMV DNAemia, drug adverse effects, and dose adjustments of concomitant cyclosporine and voriconazole (known drug interactions).

RESULTS

We compared 41 patients who received LTV prophylaxis to 41 patients who received no CMV prophylaxis. There was less clinically significant CMV DNAemia through D+180 in the LTV group (9.8% vs. 17.0%, p = .33). Overall, LTV was well tolerated, and 87.8% of patients experienced no adverse effects related to the drug. There was no observed pattern in LTV effect on cyclosporine serum concentrations, but LTV was associated with decreased voriconazole trough levels.

CONCLUSIONS

In this retrospective study, the use of LTV prophylaxis in pediatric stem cell patients was associated with reduced clinically significant CMV DNAemia through D+180.

CMV hyperimmune globulin as salvage therapy for recurrent or refractory CMV infection in children undergoing hematopoietic stem cell transplantation

Cytomegalovirus (CMV) is a major cause of allogeneic hematopoietic stem cell transplant (HSCT)-related morbidity and mortality. Treatment failure continues to be a major issue in patients with CMV infection due to both drug resistance and intolerance. This single-center brief retrospective analysis of a case series aims to investigate the safety and efficacy of CMV-hyperimmune globulin as salvage therapy for CMV infection in children undergoing HSCT. Fifteen pediatric patients received human CMV-specific immunoglobulin (CMVIG) between July 2018 and December 2021 as a salvage therapy for refractory or recurrent CMV infection. At the time of CMVIG prescription, eight children presented with recurrent CMV infection and seven with refractory CMV infection. The overall response rate was 67% at 50 days from the CMVIG administration [95% confidence interval (CI): 44-88]. Overall survival (OS) from CMVIG administration at 100 days was 87% (95% CI: 56-96), and OS from HSCT at 1 year was 80% (95% CI: 50-93). Four patients died, three unrelated to CMV infection and one due to CMV pneumonia. CMVIG as salvage therapy was well tolerated, and no infusion-related adverse events were observed.

CMV-IgG pre-allogeneic hematopoietic stem cell transplantation and the risk for CMV reactivation and mortality

Cytomegalovirus (CMV) represents one of the most common infectious complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Currently, a common diagnostic test used to stratify the risk for CMV infection in allo-HSCT recipients is the qualitative CMV serology of donor and recipient. A positive serostatus of the recipient is the most important risk factor for CMV reactivation and associated with reduced overall survival post-transplantation (TX). Direct and indirect effects of CMV are involved in the poorer survival outcome. The present study investigated if the quantitative interpretation of anti-CMV IgG before allo-HSCT might serve as a novel parameter for the identification of patients at risk for CMV reactivation and worse outcome post-TX. For this purpose, a cohort of 440 allo-HSCT recipients over a period of 10 years was retrospectively analyzed. Our findings indicated that patients with high CMV IgG pre-allo-HSCT had a higher risk to develop CMV reactivation, including clinically relevant infections, and a worse prognosis 36 months post-allo-HSCT as compared to recipients with low CMV IgG values. In the letermovir (LMV) era, this group of patients might benefit from a closer CMV monitoring, and hence, earlier intervention if needed, especially after discontinuation of prophylaxis.

New trends in the management of cytomegalovirus infection after allogeneic hematopoietic cell transplantation: a survey of the Infectious Diseases Working Pary of EBMT

The management of cytomegalovirus (CMV) infection was assessed with a survey performed in 2020 by the Infectious Diseases Working Party of European Society for Blood and Marrow Transplantation (EBMT). One-hundred-eighty of the 579 EBMT centres (31%) responded. CMV monitoring with quantitative PCR for CMV-DNAemia was used by 97% of centres while the duration of monitoring was variable according to the patient immune recovery and the ongoing immunosuppressive therapy. CMV prophylaxis for high-risk patients was used in 101 (56%) of centres: letermovir in 62 centres (61%), aciclovir/valaciclovir in 19 centres (19%), ganciclovir/valganciclovir in 17 centres (17%), foscarnet in 3 (3%). The most used trigger for pre-emptive therapy was a threshold of >10³ copies/ml or >10³ IU/ml. Ganciclovir/valganciclovir confirmed the preferred first line treatment both for pre-emptive and CMV disease therapy. CMV-cytotoxic T-cells were used mainly in the setting of relapsing/refractory CMV disease. Forty-eight centres reported CMV refractory/resistant infection due to mutated CMV strain.This survey showed that letermovir prophylaxis is adopted by more than half of centres using a prophylaxis approach for CMV infection. How letermovir prophylaxis will modify other important pillars of daily CMV management, such as frequency of CMV-DNAemia monitoring and preemptive therapy, remain a matter of investigation.

Efficacy of Cytomegalovirus Specific Immunoglobulins to Reduce CMV Reactivation in Pediatric Hematopoietic Stem Cell Transplant Recipients

Cytomegalovirus (CMV) infection is a serious complication of pediatric hematopoietic stem cell transplant (HSCT). To date, antiviral therapy has been the mainstay of prophylaxis, with conflicting results regarding the benefits of CMV-specific immunoglobulins (CMV-Ig). After introducing prophylactic CMV-Ig to HSCT recipients at risk (seropositive recipient and/or donor), we conducted a single-center retrospective study comparing the incidence and severity of CMV infection with and without CMV-Ig. We identified 49 'at risk' recipients from 76 consecutive HSCTs over 3.5 years, in addition to standard antiviral prophylaxis, 10 patients received CMV-Ig and 39 did not. There was no significant difference in donor type, cell source, conditioning, or CMV status between the groups. We observed a potential trend toward reduction of incidence of CMV reactivation in patients exposed to CMV-Ig (30%) compared with those who weren't (38.4%). Besides, no symptomatic or lethal infection was observed in the CMV-Ig group, and time to recovery seemed shorter (21 [±7] vs 51.4 [±55] days) and peak titers lower (4578 [±4788] vs 24131 [±49257]) with CMV-Ig. No adverse events were noted. The statistical significance of the results was limited by the small sample size. These data raise interest in prophylactic CMV-Ig as a safe way of potentially reducing the severity and duration of CMV reactivation in HSCT.

Letermovir for Prophylaxis and Pre-emptive Therapy of Cytomegalovirus Infection in Paediatric Allogeneic Haematopoietic Cell Transplant Patients

BACKGROUND

Cytomegalovirus (CMV) infection is a frequent event in patients undergoing allogeneic haematopoietic cell transplantation (HCT) and is associated with increased morbidity and mortality due to eventual progress to end-organ disease. Letermovir prophylaxis for CMV infections has become a standard of care in adult HCT recipients due to its efficacy and high tolerability. However, it is not yet approved for paediatric patients.

OBJECTIVE

In a retrospective single-centre observational study we evaluated the use of letermovir for prophylaxis or pre-emptive treatment of cytomegalovirus (CMV) infection in seropositive paediatric HCT recipients receiving the compound outside of clinical trials. The primary endpoint was CMV reactivation requiring a change of medication.

METHODS

A total of 17 patients (seven female/ten male; median age 12.2 [range 3.5-19] years, median body weight 39.5 [range 15-63] kg; median follow-up time 463.7 [range 41-1022] days) were identified who were started on oral (14) or intravenous (3) followed by oral (2) letermovir shortly after neutrophil engraftment at doses determined on the basis of age, weight, and concomitant cyclosporine use.

RESULTS

Five patients had no evidence of viral replication (prophylactic use), while 12 patients had varying extents of viral replication (pre-emptive therapy). A change of therapy was required in one patient due to a sustained increase in CMV viral load, and in two patients, letermovir was stopped without later reactivation after initiation of palliative care for recurrent leukaemia. Of the 14 patients who completed treatment, 3 had evidence of transient viral replication after end of treatment that required no further antiviral treatment. No patients (of 17) discontinued letermovir due to an adverse event.

CONCLUSION

Letermovir was effective in controlling CMV infection in seropositive paediatric allogeneic HCT recipients and was overall well tolerated. Pending completion of the still ongoing paediatric investigation plans, letermovir will be an important adjunct to our options for control of infectious complications in this special population.

Letermovir as Cytomegalovirus Prophylaxis in a Pediatric Cohort: A Retrospective Analysis

Letermovir is an attractive cytomegalovirus (CMV) prophylactic agent, but published data in children are scarce. This retrospective chart review aimed to describe our experience using letermovir as CMV prophylaxis in pediatric hematopoietic cell transplantation (HCT) recipients. Pediatric patients (age <20 years) undergoing allogeneic HCT and receiving letermovir prophylaxis in the Mayo Clinic Pediatric Bone Marrow Transplant Program were eligible for inclusion in this retrospective chart review. Medical records were reviewed to evaluate letermovir dosing, CMV levels, laboratory values, and reports of adverse effects. Between October 2020 and April 2022, 9 patients age 4 to 19 years undergoing allogeneic HCT in the Pediatric Bone Marrow Transplant Program received letermovir prophylaxis, either 240 mg or 480 mg daily at a mean and median dose of 10 mg/kg/day. Letermovir was crushed and administered via nasogastric tube in 4 of 9 patients. Two patients received letermovir for secondary CMV prophylaxis after initial treatment with ganciclovir/valganciclovir, and the remaining 7 received letermovir for primary prophylaxis. One patient, a 20-kg 6-year-old female receiving 240 mg (12 mg/kg), experienced low-level CMV viremia while on letermovir. No other patients experienced CMV reactivation while on letermovir prophylaxis. In 2 patients, transient mild transaminitis was noted within the first weeks of letermovir therapy, which resolved without intervention, and its relationship to letermovir could not be clearly established. Letermovir administration was feasible and well tolerated as CMV prophylaxis in our small cohort of pediatric patients undergoing HCT. Larger, prospective studies are warranted to confirm the safety and efficacy of letermovir in children. © 2022 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Cytomegalovirus in the transplant setting: Where are we now and what happens next? A report from the International CMV Symposium 2021

The CMV Symposium in September 2021 was an international conference dedicated to cytomegalovirus (CMV) infection after solid organ or hematopoietic stem cell transplantation. This review provides an overview of the presentations given by the expert faculty, supplemented with educational clinical cases. Topics discussed include CMV epidemiology and diagnosis, the burden of CMV infection and disease, CMV-specific immunity and management of CMV in transplant settings. Major advances in the prevention and treatment of CMV in the past decade and increased understanding of CMV immunity have led to improved patient outcomes. In the future, management algorithms may be individualized based on the transplant recipient's immune profile, which will mark the start of a new era for patients with CMV.

The Impact of High CMV Viral Load and Refractory CMV Infection on Pediatric HSCT Recipients with Underlying Non-Malignant Disorder

Hematopoietic stem cell transplantation (HSCT) is a curative therapy for an increasing number of nonmalignant indications. Its use is restricted by severe transplant-related complications, including CMV infection; despite various prophylactic and therapeutic strategies, CMV reactivation has remarkable morbidity and mortality. The analysis included 94 children with nonmalignant disorder who underwent allogeneic HSCT in the Department of Pediatric Hematology, Oncology, and Bone Marrow Transplantation in Wrocław during years 2016–2020. Twenty-seven (29%) children presented with CMV infection, including ten (10/27; 37%) with high level CMV viremia (10,000 copies/mL). Six patients experienced subsequent CMV reactivation. The first-line ganciclovir-based (GCV) treatment was insufficient in 40% (11/27) of children. Overall survival (OS) was significantly lower in children with high CMV viremia compared to those with low levels/no CMV [1yrOS High CMV = 0.80 (95% CI 0.41–0.95) vs. 1yrOS others = 0.96 (95% CI 0.89–0.99)]. Similarly, patients with resistant and recurrent infections had greater risk of death. CMV reactivation at any level relevantly prolonged the hospital stay. CMV reactivation with high viremia load and resistant/recurrent CMV infections lead to a significant decrease in OS in children with nonmalignant disorders treated with HSCT. Our data proves there is an urgent need to introduce an effective anti-CMV prophylaxis in this cohort of patients.

Viral Nucleases from Herpesviruses and Coronavirus in Recombination and Proofreading: Potential Targets for Antiviral Drug Discovery

In this review, we explore recombination in two very different virus families that have become major threats to human health. The Herpesviridae are a large family of pathogenic double-stranded DNA viruses involved in a range of diseases affecting both people and animals. Coronaviridae are positive-strand RNA viruses (CoVs) that have also become major threats to global health and economic stability, especially in the last two decades. Despite many differences, such as the make-up of their genetic material (DNA vs. RNA) and overall mechanisms of genome replication, both human herpes viruses (HHVs) and CoVs have evolved to rely heavily on recombination for viral genome replication, adaptation to new hosts and evasion of host immune regulation. In this review, we will focus on the roles of three viral exonucleases: two HHV exonucleases (alkaline nuclease and PolExo) and one CoV exonuclease (ExoN). We will review the roles of these three nucleases in their respective life cycles and discuss the state of drug discovery efforts against these targets.

CXCR6+ and NKG2C+ Natural Killer Cells Are Distinct With Unique Phenotypic and Functional Attributes Following Bone Marrow Transplantation

Reactivation of human cytomegalovirus (HCMV) is a life-threatening complication in transplant patients. Natural Killer (NK) cells are the first lymphocyte lineage to reconstitute following an allogeneic hematopoietic stem cell transplant (HSCT). Amongst them, NK cell Group 2 isoform C/Killer cell lectin-like receptor subfamily C, member 2 (NKG2C)-expressing NK cells contribute significantly to patient protection upon HCMV reactivation. NKG2C⁺ NK cells are capable of immunological memory, albeit NK cell memory is not restricted to them. Hepatic C-X-C Motif Chemokine Receptor 6 (CXCR6)-expressing NK cells also mediate memory responses in mice and humans. Small numbers of them circulate and can thus be studied in peripheral blood samples. We hypothesize that NKG2C⁺ and CXCR6⁺ NK cell subsets are distinct. To test our hypothesis, we used multi-parametric flow cytometry to determine the phenotypes and effector functions of CD56^bright vs. CD56^dim and NKG2C⁺ vs. CXCR6⁺ human NK cell subsets in the peripheral blood (PB) of pediatric transplant recipients monthly while monitoring patients for HCMV reactivation. Interestingly, we did not find any NKG2C⁺CXCR6⁺ NK cells in the transplant recipients' peripheral blood, suggesting that NKG2C⁺ and CXCR6⁺ NK cells are distinct. Also, NKG2C-CXCR6- NK cells, rather than NKG2C⁺ NK cells, made up most NK cells post-transplant, even in transplant recipients with HCMV viremia. In contrast to NKG2C⁺ NK cells, CXCR6⁺ NK cells appeared phenotypically less differentiated but were highly proliferative and produced IFN-γ and TNF _α . Our findings contribute to our understanding of post-transplant NK cell development and its implications for human health.