American Society for Transplantation and Cellular Therapy Series: #4 - Cytomegalovirus treatment and management of resistant or refractory infections after hematopoietic cell transplantation

The Importance of Drug Exposure in the Development of Cytomegalovirus Resistance

Human cytomegalovirus (CMV) is a widespread pathogen which remains asymptomatic in healthy individuals. However, CMV disease can be life-threatening in immunocompromised individuals, particularly in transplant patients. This disease is routinely managed by antiviral agents including (val)ganciclovir, foscarnet, cidofovir, letermovir, and maribavir. Subtherapeutic antiviral drug exposure is a common occurrence and can lead to drug-resistant CMV development, a key contributor to disease progression. Breakthrough CMV often results in graft loss, end-organ failure, or death. By optimising intracellular exposure levels of antiviral therapies, it may be possible to improve patient outcomes. Therefore, this review aims to explore the relationship between antiviral exposure and the development of drug-resistant CMV. There are several challenges to achieving optimal concentrations of current and novel CMV therapies. Narrow therapeutic indices and toxicity profiles of current CMV therapeutics contribute to their subtherapeutic exposure and hence suboptimal clinical outcomes. Alternately, novel antivirals such as letermovir and maribavir offer improved pharmacokinetic profiles. However, these agents are associated with rapid resistance development. Overall, a distinct gap exists in understanding the relationship between antiviral exposure and resistance development. As a result, current clinical markers used to predict clinical efficacy lack reliability. In future, resistance development in relation to drug exposure should be included as a clinical trial endpoint to gain understanding of exposure-resistance relationships. With solid knowledge of these relationships, more predictive in vitro and in vivo markers of clinical efficacy can be identified. Additionally, pharmacokinetic-pharmacodynamic models and combination therapies should be further explored in to improve the management of CMV.

Co-designing a Novel Ordinal Endpoint for an Adaptive Platform Trial, BANDICOOT, in Pediatric Hematopoietic Stem Cell Transplant

An adaptive platform trial (APT) offers the ability to incorporate several research questions in the same target population across multiple domains (interventions), with the ability to add new questions in a perpetual manner. An APT is particularly appealing for pediatric hematopoietic stem cell transplant (HCT); an area of high heterogeneity, limited trial availability, and high mortality. Ideally, all domains in an APT would have the same primary endpoint. Therefore, an ordinal endpoint with multiple categories that combines various clinical outcomes into a single outcome measure is particularly appealing for APTs. Unfortunately, there is no accepted ordinal endpoint for pediatric HCT trials. This article aims to describe the methodology used to co-design a novel primary ordinal endpoint for the pediatric HCT APT - BANDICOOT. BANDICOOT is a study that aims to build an adaptive novel platform design - improving the complications, cost-effectiveness, outcomes, and overall survival from hematopoietic stem cell transplantation.The results of this process identified two potential ordinal endpoints that could be used, one focusing on organ support and the other on a combination of organ support, viral reactivation, and immune reconstitution. We explored the data extraction required for these endpoints from electronic medical records that we will utilize to validate the endpoints and determine which will be used in the APT BANDICOOT. In an era in which APTs are becoming increasingly utilized to answer important questions in clinical care, this article describes a reproducible strategy for the design of high-quality and meaningful ordinal endpoints.

Impact of prophylactic cytomegalovirus immunoglobulin on cytomegalovirus viremia and graft function in ABO-incompatible living donor kidney transplantation: a retrospective analysis

Background

Cytomegalovirus (CMV) infection poses a significant risk to kidney transplant recipients. CMV immunoglobulin shows promising prophylactic effect, particularly in the context of ABO-incompatible transplants. However, its efficacy in preventing CMV viremia remains underexplored.

Methods

In this retrospective study, we enrolled patients who underwent ABO-incompatible living donor kidney transplantation between May 2021 and September 2023. Prophylactic CMV immunoglobulin was administered at 100 mg/kg weekly for one month in the combined prophylaxis group, while no prophylactic medication was applied in the preemptive therapy group. The primary outcome was measured as the incidence of clinically relevant CMV viremia (CMV DNA >10,000 copies/mL) within one year after transplantation. Both groups received standard preemptive therapy with ganciclovir or valganciclovir after diagnosed with clinically relevant CMV viremia.

Results

Prophylactic CMV immunoglobulin significantly reduced clinically relevant viremia incidence compared to preemptive therapy group (16.0% vs. 34.0%, P = 0.04). At the end of the follow-up, the combined prophylaxis group showed higher eGFR (56.40 ± 14.19 vs. 47.30 ± 13.01 mL/min/1.73m², P = 0.0014) and lower serum creatinine (146.5 ± 57.07 vs. 171.2 ± 51.48 µmol/L, P = 0.0274). However, no significant differences in renal function were observed between the groups at1,3, or 6 months post-transplantation.

Conclusion

CMV immunoglobulin represents a promising prophylactic option for reducing clinically relevant CMV viremia incidence and delaying infection onset in ABO-incompatible kidney transplant recipients.

Letermovir-inclusive combination therapy for a refractory and resistant infection by cytomegalovirus with UL54 mutation following a hematopoietic stem cell transplant for MHC class II deficiency

Cytomegalovirus (CMV) infection remains one of the most common and challenging post-transplant infections. Children with inborn errors of immunity (IEI) and T-cell dysfunction are at high risk for CMV infection, which can be complicated by refractory and/or resistant cases. This case describes a Nepalese girl with MHC class II deficiency, who presented at 3 months of age with CMV and Pneumocystis jirovecii pneumonia. Hematopoietic stem cell transplantation (HSCT) was planned as a curative treatment for IEI. Initial antiviral therapy with ganciclovir, followed by foscarnet, achieved undetectable CMV viral loads. However, the viral load rebounded during foscarnet therapy. HSCT was performed at 7 months of age using peripheral blood stem cells from her CMV-seropositive father, despite the recipient's high CMV viral load. Empiric combination therapy with cidofovir (an unapproved drug in Japan), foscarnet, leflunomide, and artesunate was initiated. CMV genetic testing revealed UL54 mutations conferring high-level resistance to foscarnet and moderate-level resistance to ganciclovir. The regimen was adjusted to letermovir, ganciclovir, leflunomide, and artesunate, which successfully suppressed the viral load following engraftment. At three months post-HSCT, combination therapy was discontinued after sustained undetectable CMV viral loads. Although CMV infection was controlled, the patient died from idiopathic pulmonary hemorrhage at five months post-HSCT. This case highlights the potential efficacy of a letermovir-inclusive therapy regimen in managing drug-resistant CMV with UL54 mutations in a pediatric HSCT recipient.

Dual Resistance to Maribavir and Ganciclovir in Transplant Recipients

BACKGROUND

Human cytomegalovirus (CMV) remains an important pathogen, especially for immunocompromised patients such as solid organ and hematopoietic stem cell recipients. Viral genomic mutations conferring drug resistance are an important impediment to effective CMV management and frequently lead to use of alternative antiviral drugs to treat CMV disease.

METHODS

Results from 1459 de-identified patient samples with both UL54 and UL97 sequencing results were analyzed for ganciclovir (GCV) and maribavir (MBV) resistance mutations. Genomic sequencing was performed by the Sanger method and resistance mutations were identified by comparison to CMV reference strain AD169.

RESULTS

Ganciclovir resistance was identified in 379 of 1459 (25.98%) of the samples tested, with most resistance-conferring mutations present in viral gene UL97. A total of 121 of 1459 (8.29%) samples had MBV resistance mutations, and 84 (69.42%) of the 121 samples with MBV resistance also had GCV resistance mutations. Of the 84 samples with resistance to both MBV and GCV, 35 (41.67%) had a single UL97 mutation conferring resistance to both drugs, either C480F or F342Y. The overall prevalence of C480F was increased relative to an earlier analysis of samples from this reference laboratory.

CONCLUSIONS

Although a high prevalence of CMV resistance mutations was identified, this must be taken in the context of healthcare providers submitting samples from patients with suspected CMV resistance. Most MBV-resistant samples were also resistant to GCV, suggesting that use of MBV as an alternative to GCV may benefit from genotypic resistance testing to achieve the effective control of CMV disease.

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.

How Should Cytomegalovirus Infection Be Managed in Allogeneic Hematopoietic Stem Cell Transplant Recipients? A Clinical Grand Round

Cytomegalovirus (CMV) is a significant concern for patients with allogeneic hematopoietic cell transplantation (allo-HCT). CMV management differs between institutions due to the lack of local guidelines. Here, we describe a case of refractory/resistant CMV infection treated using our institution's CMV management protocol. A 59-year-old woman who underwent allo-HCT was treated for CMV reactivation. Despite 3 months of valganciclovir administration, serum CMV level surged. CMV gene mutation test revealed a ganciclovir-resistant A594V mutation in the UL97 gene. Treatment was switched to foscarnet until the drug became unavailable nationwide. During the foscarnet shortage, cidofovir was used, leading to a decline in CMV levels when foscarnet was reintroduced and used for 2 months. Following allo-HCT, CMV prophylaxis with letermovir is crucial to prevent reactivation in seropositive recipients. CMV titers should be monitored frequently after allo-HCT. The cutoff value for preemptive therapy varies across institutions, with ganciclovir/valganciclovir usually administered as first-line therapy. Maribavir is an option in cases of ganciclovir/valganciclovir resistance or intolerance. CMV gene mutations should be examined in patients with suspected resistance after 2 weeks of appropriate treatment. This case was discussed at the Clinical Grand Round of the Annual Conference of the Korean Society of Infectious Diseases on November 2, 2023.

Letermovir for Prevention of Recurrent Cytomegalovirus in High-Risk Allogeneic Hematopoietic Cell Transplantation Recipients

We evaluated letermovir (LTV) for secondary prophylaxis for cytomegalovirus (CMV) in allogeneic hematopoietic cell transplant recipients (HCT) at high-risk for CMV recurrence. This open-label study was conducted at Memorial Sloan Kettering Cancer Center and the University of Minnesota. Patients with clinically significant CMV infection (cs-CMVi) and ≥1 high-risk criteria for CMV who achieved viral suppression with standard CMV antivirals received LTV secondary prophylaxis for up to 14 weeks. The primary endpoint was cs-CMVi at week 14; secondary endpoints included LTV resistance, CMV end-organ disease (EOD), CMV-related death, and LTV-related adverse events at week 14. Thirty-six patients were analyzed (CMV seropositive, n = 33; T cell-depleted HCT, n = 25; cord blood allograft, n = 5). By week 14 post-transplantation, 5 patients met the primary endpoint of cs-CMVi, for a cumulative incidence of 14.9% (95% confidence interval, 2.6% to 27.1%). Four patients developed LTV breakthrough cs-CMVi (including 2 patients with confirmed LTV resistance). The remaining patient developed rebound cs-CMVi after premature discontinuation of LTV due to enrollment in a clinical trial. There were no cases of CMV EOD, CMV-related death, or LTV-related adverse events by week 14 or by week 24. Our data support that LTV secondary prophylaxis is safe and effective in high-risk HCT recipients.

Real-World Comparison of Maribavir to Foscarnet for the Treatment of Cytomegalovirus in Solid Organ and Hematopoietic Stem Cell Transplant Recipients

Cytomegalovirus (CMV) infection in solid organ transplant (SOT) and hematopoietic cell transplant (HCT) recipients may increase the risk of rejection or allograft dysfunction, other infection(s), and morbidity and mortality. Treatment can be challenging due to medication-associated toxicities. Maribavir (MBV) is a promising option for the treatment of resistant or refractory (R/R) CMV infection in lieu of foscarnet (FOS), which has long been the recommended therapy for (val)ganciclovir-resistant infection. This was a single-center retrospective study of clinical outcomes of patients who received MBV compared to a control group who received FOS for an episode of CMV infection. Each cohort consisted of 27 episodes of CMV infection. Twenty patients in the MBV cohort and from the FOS cohort cleared the infection, with five and three patients developing MBV or FOS resistance, respectively. There were no statistically significant differences in failure of therapy as evidenced by persistent DNAemia (p = 0.56) or development of antiviral resistance (p = 0.24). In conclusion, MBV was as effective as FOS for the treatment of R/R CMV infection and was better tolerated without increased risk of antiviral resistance.

The emergence of letermovir and maribavir drug-resistant mutations: from clinical trials to real-world studies

PURPOSE OF REVIEW

Cytomegalovirus (CMV) infection is associated with severe clinical disease and high morbidity in immunocompromised hosts. Letermovir and maribavir, are two recently developed antiviral drugs used in the prevention and treatment of resistant and refractory CMV. Following the publication of landmark randomized trials and increased use, both clinical trial data and real-world experience has reported the development of antiviral drug resistance. The aim of this review was to comprehensively review the published literature on letermovir and maribavir drug resistance and to describe the clinical scenarios in which they may emerge.

RECENT FINDINGS

For letermovir, the most frequently detected resistance mutations occur in the UL56 gene (C325Y/W/F) and confer total resistance. Maribavir resistance mutations most often occur in the UL97 gene and resistance-associated variants (RAVs) T409M, H411Y, C480F have all been detected. The clinical context in which letermovir and maribavir resistance occurs include high viral loads at initiation, intensified immunosuppression, subtherapeutic drug exposure because of poor adherence, drug interactions, and inadequate central nervous system (CNS) penetration. Emergence of resistance mutations generally occurs within the first 3 months of initiation.

SUMMARY

The detection of letermovir and maribavir resistance mutations highlights an ongoing clinical challenge in the management of CMV.

Cytomegalovirus viral load at initiation of pre-emptive antiviral therapy impacts cytomegalovirus dynamics in pediatric allogeneic hematopoietic cell transplantation recipients

BACKGROUND

Cytomegalovirus (CMV) contributes to morbidity and mortality in allogeneic hematopoietic cell transplantation (allo-HCT) recipients. Pre-emptive antiviral therapy (PET) reduces the incidence of CMV end-organ disease (EOD), though relevant viral thresholds to initiate PET remain undefined. We evaluated the impact of viral loads (VLs) at PET initiation on virologic and clinical outcomes following pediatric allo-HCT.

METHODS

Single-center retrospective cohort analysis of children who underwent their first allo-HCT from January 2014 to December 2020. Weekly quantitative plasma CMV polymerase chain reaction was performed until Day +100 and PET was initiated once VL exceeded a pre-defined threshold per institutional guidelines. Patients were followed for 1-year post-HCT to evaluate virologic and clinical outcomes including end-organ disease (EOD), overall survival (OS), and non-relapse mortality (NRM).

RESULTS

Among 146 allo-HCT recipients, CMV DNAemia occurred in 40 patients (27%) at a median of 15 days post-HCT (interquartile range 6-28.5). Ten percent (n = 4) had spontaneous resolution of DNAemia, while 90% (n = 36) required PET. PET initiated when CMV VL was ≥ 1000 IU/mL (n = 21) vs when VL < 1000 IU/mL (n = 15) resulted in higher peak CMV VL (12,670 vs. 1284 IU/mL, p = 0.0001) and longer time to CMV DNAemia resolution (36 vs. 24 days, p = 0.035). There were no differences in EOD, OS, or NRM at 12 months post-HCT based on VL at PET initiation.

CONCLUSIONS

Initiating PET when CMV VL was ≥1000 IU/mL resulted in significantly higher peak VL and prolonged DNAemia, with no differences in EOD, OS, or NRM at 12 months post pediatric HCT.

Pulmonary complications of bone marrow transplantation

Bone marrow transplantation, now often known as haematopoietic stem cell transplantation (HSCT), is a complex choreographed procedure used to treat both acquired and inherited disorders of the bone marrow. It has proven invaluable as therapy for haematological and immunological disorders, and more recently in the treatment of metabolic and enzyme disorders. As the number of performed transplants grows annually, and with patients enjoying improved survival, a knowledge of both early and late complications of HSCT is essential for respiratory trainees and physicians in practice. This article highlights the spectrum of respiratory complications, both infectious and non-infectious, the timeline of their likely occurrence, and the approaches used for diagnosis and treatment, keeping in mind that more than one entity may occur simultaneously. As respiratory issues are often a leading cause of short- and long-term morbidity, consideration of a combined haematology/respiratory clinic may prove useful in this patient population.

Management of resistant and refractory cytomegalovirus infections after transplantation

INTRODUCTION

Cytomegalovirus (CMV) is a classic opportunistic infection in transplant recipients. Treatment-refractory CMV infections are of concern, with growing identification of strains that have developed genetic mutations which confer resistance to standard antiviral therapy. Resistant and refractory CMV infections are associated with worse patient outcomes, prolonged hospitalization, and increased healthcare costs.

AREAS COVERED

This article provides a comprehensive practical overview of resistant and refractory CMV infections in transplant recipients. We review the updated definitions for these infections, antiviral pharmacology, mechanisms of drug resistance, diagnostic workup, management strategies, and host-related factors including immune optimization.

EXPERT OPINION

Resistant and refractory CMV infections are a significant contributor to post-transplant morbidity and mortality. This is likely the result of a combination of prolonged antiviral exposure and active viral replication in the setting of intensive pharmacologic immunosuppression. Successful control of resistant and refractory infections in transplant recipients requires a combination of immunomodulatory optimization and appropriate antiviral drug choice with sufficient treatment duration.

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.

Refractory/Resistant Cytomegalovirus Infection in Transplant Recipients: An Update

Despite the significant progress made, CMV infection is one of the most frequent infectious complications in transplant recipients. CMV infections that become refractory or resistant (R/R) to the available antiviral drugs constitute a clinical challenge and are associated with increased morbidity and mortality. Novel anti-CMV therapies have been recently developed and introduced in clinical practice, which may improve the treatment of these infections. In this review, we summarize the treatment options for R/R CMV infections in adult hematopoietic cell transplant and solid organ transplant recipients, with a special focus on newly available antiviral agents with anti-CMV activity, including maribavir and letermovir.

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

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

Case Report: Approaches for managing resistant cytomegalovirus in pediatric allogeneic hematopoietic cell transplantation recipients

The instructional case is a pediatric haploidentical TCRαβ+/CD19+ depleted allogeneic hematopoietic cell transplantation recipient who developed early onset CMV infection, which was complicated by resistant CMV (both UL97 and UL54) and successfully managed with maribavir and haploidentical CMV-specific T lymphocytes. Novel approaches to resistant CMV infection are reviewed and effective utilization of recent advances in diagnosis and management of resistant CMV in pediatric HCT are highlighted.

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

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

The indirect effects of CMV reactivation on patients following allogeneic hematopoietic stem cell transplantation: an evidence mapping

Cytomegalovirus (CMV) reactivation following allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a challenging problem, and the impact on the risk of overall mortality (OM) and non-relapse mortality (NRM) in patients following allo-HSCT is still controversial. Utilizing the evidence mapping method, we aimed to assess the effect of CMV infection on outcomes of patients post-transplantation and identify research gaps through systematic reviews (SRs) and clinical studies. PubMed, EMBASE, Web of Science, and Cochrane library databases were searched from inception until 5 July 2022 to identify relevant literature. After systematic literature screening and data extraction, evidence mapping of the effects of CMV reactivation on patients post-allo-HSCT was conducted. Three SRs and 22 clinical studies were included. In one SR, CMV reactivation was associated with an increased risk of mortality (HR 1.46; 95% CI, 1.24-1.72; P ≤ 0.001). In two SRs, CMV reactivation was associated with NRM. One SR reported CMV reactivation was potentially associated with significant protection against relapse in patients with acute myelocytic leukemia (AML), but no significant correlation with graft-versus-host disease (GVHD) was found. Lastly, in one SR CMV reactivation significantly increased the risk of invasive fungal disease (IFD). Most clinical articles reported that CMV reactivation increased the risk of renal dysfunction, poor graft function, re-hospitalization, and bacterial infections. CMV reactivation following allo-HSCT is associated with an increased risk of OM, NRM, IFD, and renal dysfunction, as well as a reduced risk of relapse in patients with AML.

Human Cytomegalovirus (HCMV) Genetic Diversity, Drug Resistance Testing and Prevalence of the Resistance Mutations: A Literature Review

Human cytomegalovirus (HCMV) is a pathogen with high prevalence in the general population that is responsible for high morbidity and mortality in immunocompromised individuals and newborns, while remaining mainly asymptomatic in healthy individuals. The HCMV genome is 236,000 nucleotides long and encodes approximately 200 genes in more than 170 open reading frames, with the highest rate of genetic polymorphisms occurring in the envelope glycoproteins. HCMV infection is treated with antiviral drugs such as ganciclovir, valganciclovir, cidofovir, foscarnet, letermovir and maribavir targeting viral enzymes, DNA polymerase, kinase and the terminase complex. One of the obstacles to successful therapy is the emergence of drug resistance, which can be tested phenotypically or by genotyping using Sanger sequencing, which is a widely available but less sensitive method, or next-generation sequencing performed in samples with a lower viral load to detect minority variants, those representing approximately 1% of the population. The prevalence of drug resistance depends on the population tested, as well as the drug, and ranges from no mutations detected to up to almost 50%. A high prevalence of resistance emphasizes the importance of testing the patient whenever resistance is suspected, which requires the development of more sensitive and rapid tests while also highlighting the need for alternative therapeutic targets, strategies and the development of an effective vaccine.

Enhanced Immunomodulatory Effects of Thymosin-Alpha-1 in Combination with Polyanionic Carbosilane Dendrimers against HCMV Infection

Resistance and toxicity associated with current treatments for human cytomegalovirus (HCMV) infection highlight the need for alternatives and immunotherapy has emerged as a promising strategy. This study examined the in vitro immunological effects of co-administration of Thymosin-alpha-1 (Tα1) and polyanionic carbosilane dendrimers (PCDs) on peripheral blood mononuclear cells (PBMCs) during HCMV infection. The biocompatibility of PCDs was assessed via MTT and LDH assays. PBMCs were pre-treated with the co-administered compounds and then exposed to HCMV for 48 h. Morphological alterations in PBMCs were observed using optical microscopy and total dendritic cells (tDCs), myeloid dendritic cells (mDCs), and plasmacytoid dendritic cells (pDCs), along with CD4+/CD8+ T cells and regulatory T cells (Treg), and were characterized using multiparametric flow cytometry. The findings revealed that Tα1 + PCDs treatments increased DC activation and maturation. Furthermore, increased co-receptor expression, intracellular IFNγ production in T cells and elevated Treg functionality and reduced senescence were evident with Tα1 + G2-S24P treatment. Conversely, reduced co-receptor expression, intracellular cytokine production in T cells, lower functionality and higher senescence in Treg were observed with Tα1 + G2S16 treatment. In summary, Tα1 + PCDs treatments demonstrate synergistic effects during early HCMV infection, suggesting their use as an alternative therapeutic for preventing virus infection.

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.

Risk Factors Associated with Survival Following Ganciclovir Prophylaxis through Day +100 in Cytomegalovirus At-Risk Pediatric Allogeneic Stem Cell Transplantation Recipients: Development of Cytomegalovirus Viremia Associated with Significantly Decreased 1-Year Survival

Cytomegalovirus (CMV) reactivation is a major cause of morbidity and nonrelapse mortality (NRM) in pediatric allogeneic stem cell transplantation (alloSCT) recipients. Approximately 80% of CMV seropositive alloHCT recipients will experience CMV reactivation without prophylaxis. The impacts of ganciclovir prophylaxis and subsequent CMV viremia on 1-year survival and 1-year NRM are unknown. The primary objective of this study was to determine the effect of CMV viremia on the probability of 1-year survival and 1-year NRM in pediatric alloSCT recipients receiving 100 days of ganciclovir prophylaxis. The secondary objective was to determine the effect of other risk factors on 1-year survival and 1-year NRM. All patients age 0 to 26 years who underwent alloSCT between June 2011 and May 2020 and received ganciclovir prophylaxis for 100 days at Westchester Medical Center, an academic medical center, were analyzed. Ganciclovir was administered to at-risk alloSCT recipients (donor and or recipient CMV+ serostatus) as 5 mg/kg every 12 hours from the first day of conditioning through day -1 (recipient CMV+ only) followed by 6 mg/kg every 24 hours on Monday through Friday beginning on the day of an absolute neutrophil count >750/mm3 and continuing through day +100. National Cancer Institute Common Terminology Criteria for Adverse Events 5.0 criteria were used to grade toxicity. NRM was analyzed using competing survival analysis with relapse death as a competing event. The log-rank and Gray tests were performed to compare the 1-year survival probabilities and NRM cumulative incidence between patients who experienced CMV viremia post-alloSCT and those who did not. Univariate Cox regression analysis was performed for the following risk factors: CMV viremia, donor source, sex, malignant disease, disease risk index, conditioning intensity, receipt of rabbit antithymocyte globulin (rATG)/alemtuzumab, graft-versus-host disease (GVHD) prophylaxis, CMV donor/recipient serostatus, grade II-IV acute GVHD, and grade 3/4 neutropenia necessitating discontinuation of ganciclovir, treating the last 3 factors as time-dependent covariates. Those with P values < .2 were included in the multivariate Cox regression analysis. Eighty-four alloSCT recipients (41 males, 43 females; median age, 10.8 years [range, .4 to 24.4 years]) were analyzed. Multivariate analysis showed significantly lower 1-year survival and significantly higher 1-year NRM in patients who developed CMV viremia compared to those who did not (P = .0036). No other risk factors were significantly associated with 1-year survival or 1-year NRM. One-year survival was significantly decreased and 1-year NRM was significantly increased in pediatric alloSCT recipients who developed CMV viremia following ganciclovir prophylaxis. No other risk factors were found to be associated with 1-year survival or 1-year NRM. Alternative CMV prophylaxis regimens that reduce CMV viremia should be investigated in pediatric alloSCT recipients at risk for CMV infection.

Incidence of refractory CMV infection with or without antiviral resistance in Spain: A systematic literature review

INTRODUCTION

Solid organ transplantation (SOT) and hematopoietic stem cell transplantation (HSCT) recipients are susceptible to cytomegalovirus (CMV) infection. The incidence of refractoriness to antivirals, with or without resistance, is unclear. The purpose of this review was to describe the epidemiology of refractory CMV infection in Spain to understand the current unmet needs.

METHODS

PubMed, EMBASE, Cochrane and MEDES were searched systematically for relevant articles. We included randomized controlled trials and observational studies published during the period from January 1990 to June 2021.

RESULTS

From 212 screened records, we selected 19 papers including 1973 transplant recipients. Refractory infection ranged from 3 to 10% in studies with SOT recipients. The incidence of CMV resistance ranged from 1% to 36% in these patients. The incidence of CMV refractory infection in HSCT recipients ranged from 11 to 50%, while values for resistant infection ranged from 0% to 21%.

CONCLUSION

The wide range of definitions and values observed does not allow us to establish the true incidence of refractory CMV infection with or without resistances in SOT and HSCT patients in Spain. This review highlights the gap between clinical practice and clinical trials' definitions which needed to be updated to be easier followed in current clinical practice.

MicroRNAs in infectious diseases: potential diagnostic biomarkers and therapeutic targets

MicroRNAs (miRNAs) are conserved, short, non-coding RNAs that play a crucial role in the post-transcriptional regulation of gene expression. They have been implicated in the pathogenesis of cancer and neurological, cardiovascular, and autoimmune diseases. Several recent studies have suggested that miRNAs are key players in regulating the differentiation, maturation, and activation of immune cells, thereby influencing the host immune response to infection. The resultant upregulation or downregulation of miRNAs from infection influences the protein expression of genes responsible for the immune response and can determine the risk of disease progression. Recently, miRNAs have been explored as diagnostic biomarkers and therapeutic targets in various infectious diseases. This review summarizes our current understanding of the role of miRNAs during viral, fungal, bacterial, and parasitic infections from a clinical perspective, including critical functional mechanisms and implications for their potential use as biomarkers and therapeutic targets.

At-Home Foscarnet Administration in Patients with Cytomegalovirus Infection Post-Allogeneic Stem Cell Transplantation: A Unicentric, Safe, and Feasible Program

Cytomegalovirus (CMV) infection is a relevant cause of morbimortality in patients receiving allogeneic stem cell transplantation (allo-HCT). Foscarnet (FCN) is an effective drug against CMV administered intravenously and usually on an inpatient basis. The Home Care Unit (HCU) for hematologic patients at our hospital designed an at-home FCN administration model to avoid the hospitalization of patients requiring FCN treatment. This study analyzes whether the at-home administration of FCN is as safe and effective as its hospital administration. We collected and compared demographic, clinical, analytical, and economic data of patients with CMV infection post-allo-HCT who received FCN in the hospital (n = 16, 17 episodes) vs. at-home (n = 67, 88 episodes). The proportions of patients with cured CMV infections were comparable between the two groups (65.9% vs. 76.5%, p = 0.395). The median duration of FCN treatment was 15 (interquartile range [IQR] 9-23) and 14 (IQR 11-19) days in the HCU and inpatient cohorts, respectively (p = 0.692). There were no significant differences in the FCN toxicities between groups except for hypocalcemia (26.1% vs. 58.8%, p = 0.007), which was more prevalent in the inpatient cohort. A significant cost-effectiveness was found in the HCU cohort, with a median savings per episode of EUR 5270. It may be concluded that home administration of FCN is a safe, effective, and cost-efficient therapeutic option for patients with CMV infection and disease.

CMV prevention strategies in allogeneic hematopoietic cell transplantation; the role of prophylaxis and pre-emptive monitoring in the era of letermovir

The preferred strategy for preventing CMV in at-risk populations in alloHCT has undergone a significant practice shift in recent years where the pendulum has swung from a pre-emptive approach to now offering letermovir prophylaxis to all CMV seropositive recipients. Letermovir prophylaxis has resulted in significant reductions in post-transplant clinically significant CMV infection (csCMVi) as well as other important outcomes such as CMV disease, resistant, and refractory CMV infections and nonrelapse mortality. However, prophylactic strategies are not without some limitations, namely delayed onset CMV infections, delayed CMV-specific T cell immune reconstitution, increased drug costs and limited data within pediatric populations. Thus, this review aims to provide an overview of prophylaxis and pre-emptive CMV preventative strategies, and how they are applicable in the current era of letermovir prophylaxis.

Updates in hematopoietic cell transplant and cellular therapies that enhance the risk for opportunistic infections

BACKGROUND

Infectious disease physicians may be asked to evaluate and manage a variety of infections in immunocompromised hosts undergoing hematopoietic cell transplant (HCT) and cellular therapies. Over the last decade, several advances in cellular therapy have occurred, with implications for the types of infectious complications that may be seen.

AIMS

The purpose of this review is to update the infectious disease physician on newer advances in HCT and cellular therapy, including haploidentical transplant, expanding indications for transplant in older individuals and children, and chimeric antigen receptor T-cells. We will review how these advances might influence infectious disease complications following HCT. We will also provide a perspective that infectious disease physicians can use to evaluate the degree of immune suppression in an individual patient to help determine the type of infections that may be encountered.

Epidemiology, treatment patterns, and disease burden of cytomegalovirus in hematopoietic cell transplant recipients in selected countries outside of Europe and North America: A systematic review

BACKGROUND

Cytomegalovirus (CMV) disease impacts morbidity and mortality in hematopoietic cell transplant (HCT) recipients. This systematic review summarized data on the epidemiology, management, and burden of CMV post-HCT outside of Europe and North America.

METHODS

The MEDLINE, Embase, and Cochrane databases were searched for observational studies and treatment guidelines in HCT recipients across 15 selected countries from Asia-Pacific, Latin America, and Middle East (search period: 1 January 2011-17 September 2021). Outcomes included incidence of CMV infection/disease, recurrence, risk factors, CMV-related mortality, treatments, refractory, resistant CMV, and burden.

RESULTS

Of 2708 references identified, 68 were eligible (67 studies and one guideline; 45/67 studies specific to adult allogeneic HCT recipients). The rates of CMV infection and disease within 1 year of allogeneic HCT were 24.9%-61.2% (23 studies) and 2.9%-15.7% (10 studies), respectively. Recurrence occurred in 19.8%-37.9% of cases (11 studies). Up to 10% of HCT recipients died of CMV-related causes. In all countries, first-line treatment for CMV infection/disease involved intravenous ganciclovir or valganciclovir. Conventional treatments were associated with serious adverse events such as myelosuppression (10.0%) or neutropenia only (30.0%, 39.8%) and nephrotoxicity (11.0%) (three studies), frequently leading to treatment discontinuation (up to 13.6%). Refractory CMV was reported in 2.9%, 13.0%, and 28.9% of treated patients (three studies) with resistant CMV diagnosed in 0%-10% of recipients (five studies). Patient-reported outcomes and economic data were scarce.

CONCLUSION

The incidence of CMV infection and disease post-HCT is high outside of North America and Europe. CMV resistance and toxicity highlight a major unmet need with current conventional treatments.

Third-party cytomegalovirus-specific T cells improved survival in refractory cytomegalovirus viremia after hematopoietic transplant

BackgroundRefractory CMV viremia and disease are associated with significant morbidity and mortality in recipients of hematopoietic stem cell transplant (HCT).MethodsIn phase I/II trials, we treated 67 subjects for CMV viremia or disease arising after HCT with adoptive transfer of banked, third-party, CMVpp65-sensitized T cells (CMVpp65-VSTs). All were evaluable for toxicity and 59 for response. Evaluable subjects had CMV disease or persisting viremia that had failed at least 2 weeks of induction therapy with a median of 3 antiviral drugs; 84.7% had more than 3 of 11 high-risk features. CMVpp65-VSTs were specific for 1 to 3 CMVpp65 epitopes, presented by a limited set of HLA class I or II alleles, and were selected based on high-resolution HLA matching at 2 of 10 HLA alleles and matching for subject and subject's HCT donor for 1 or more alleles through which the CMVpp65-VSTs were restricted.ResultsT cell infusions were well tolerated. Of 59 subjects evaluable for response, 38 (64%) achieved complete or durable partial responses.ConclusionsRecipients responding to CMVpp65VSTs experienced an improved overall survival. Of the risk factors evaluated, transplant type, recipient CD4+ and CD8+ T cell levels prior to adoptive therapy, and the HLA restriction of CMVpp65-VSTs infused each significantly affected responses. In addition, CMVpp65-specific T cells of HCT donor or recipient origin contributed to the durability of both complete and partial responses.Trial RegistrationNCT00674648; NCT01646645; NCT02136797 (NIH).FundingNIH (P01 CA23766, R21 CA162002 and P30 CA008748); Aubrey Fund; Claire Tow Foundation; Major Family Foundation; "Rick" Eisemann Pediatric Research Fund; Banbury Foundation; Edith Robertson Foundation; Larry Smead Foundation.

Prevalence of cytomegalovirus antiviral drug resistance in transplant recipients

Cytomegalovirus (CMV) is a significant human pathogen, especially for immunocompromised patients, often treated with one or more antiviral drugs. Although the prevalence of resistance is low, the impact of drug resistant CMV infections on patient outcomes is high and genotypic testing is recommended when resistance is suspected. To assess the prevalence of CMV drug resistance mutations among samples submitted for genotypic testing, 2750 patient sample results were analyzed. Testing was performed by sequencing for ganciclovir (GCV), cidofovir (CDV), foscarnet (FOS), maribavir (MBV) and/or letermovir (LMV) resistance conferring mutations. Of the 2750 patient samples, 826 (30.04%) had resistance to one or more anti-CMV drug. Resistance mutations were most common in UL97, with 27.64% and 9.96% of samples having GCV and MBV mutations, respectively. Resistance mutations in UL54 were less common, with 6.11%, 5.98% and 1.76% of samples having GCV, CDV and FOS mutations, respectively. For LMV, resistance mutations in UL56 were present in 7.17% of samples, with mutations at codon 325 representing 80.95% of the observed LMV resistance mutations. Resistance to two drugs was identified in 215 samples and to 3 or more drugs in 35 samples. While a high prevalence of CMV resistance mutations was identified, this must be taken in the context of healthcare providers submitting samples from patients with suspected resistant CMV strains. For these patients, rapid monitoring for resistance allows treatment modifications based on objective results rather than empiric drug selection, which is particularly relevant given the presence of mutations conferring resistance to more than one drug.

Population Pharmacokinetics of Ganciclovir in Allogeneic Hematopoietic Stem Cell Transplant Patients

Treatment of cytomegalovirus (CMV) infection in allogeneic hematopoietic stem cell transplantation (alloHCT) patients with ganciclovir is complicated by toxicity and resistance. This study aimed to develop an intravenous ganciclovir population pharmacokinetic model for post-alloHCT patients and to determine dosing regimens likely to achieve suggested therapeutic exposure targets. We performed a prospective observational single-center pharmacokinetic study in adult alloHCT patients requiring treatment with intravenous ganciclovir for CMV viremia or disease. Samples were analyzed using a validated ultraperformance liquid chromatography method. Population pharmacokinetic analysis and Monte Carlo simulations (n = 1000) were performed using Pmetrics for R. Twenty patients aged 18 to 69 years were included in the study. A 2-compartment model with linear elimination from the central compartment and between occasion variability best described the data. Incorporating creatinine clearance (CLCR) estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and presence of continuous renal replacement therapy as covariates for ganciclovir clearance improved the model. Compared to current dosing recommendations, simulations demonstrated loading doses were required to achieve a target AUC24 of 80 to 120 mg.h/L on day 1 of induction therapy. Increased individualization of post-loading induction and maintenance doses based on CLCR is required to achieve the suggested exposures for efficacy (AUC24 >80/>40 mg.h/L for induction/maintenance) while remaining below the exposure thresholds for toxicity (AUC24 <120/<60 mg.h/L for induction/maintenance). Intravenous ganciclovir dosing in alloHCT patients can be guided by CLCR estimated by CKD-EPI. Incorporation of loading doses into induction dosing regimens should be considered for timely achievement of currently suggested exposures.

The Ten Most Common Questions on Cytomegalovirus Infection in Hematopoietic Stem Cell Transplant Patients

With the rising number of patients undergoing hematopoietic stem cell transplantation (HSCT), clinicians are more likely to encounter infectious complications in immunocompromised hosts, particularly cytomegalovirus (CMV) infection. Besides the high mortality of CMV end-organ disease, patients with detectable CMV viremia may have worse outcomes and decreased survival even in the absence of end-organ disease. In view of the implications on morbidity and mortality, clinicians should maintain a high index of suspicion and initiate antiviral drugs promptly when CMV infection is confirmed. High-risk patients should be identified in order to provide optimal management. Additionally, novel antiviral agents with a good safety profile and minor adverse events are now available for prophylaxis in high-risk patients and for treatment of resistant or refractory CMV infection. The following review provides concise, yet comprehensive, guidance on the burden and risk factors of CMV in this population, as well as an update on the latest evidence for the management of CMV infection.

Challenges, Recent Advances and Perspectives in the Treatment of Human Cytomegalovirus Infections

Human cytomegalovirus (HCMV) is ubiquitous worldwide and elicits global health problems. The diseases associated with HCMV are a serious threat to humans, especially for the sick, infant, elderly and immunocompromised/immunodeficient individuals. Although traditional antiviral drugs (e.g., ganciclovir, valganciclovir, cidofovir, foscarnet) can be used to treat or prevent acute HCMV infections, their efficacy is limited because of toxicity, resistance issues, side effects and other problems. Fortunately, novel drugs (e.g., letermovir and maribavir) with less toxicity and drug/cross-resistance have been approved and put on the market in recent years. The nucleic acid-based gene-targeting approaches including the external guide sequences (EGSs)-RNase, the clustered regularly interspaced short palindromic repeats (CRISPRs)/CRISPRs-associated protein 9 (Cas9) system and transcription activator-like effector nucleases (TALENs) have been investigated to remove both lytic and latent CMV in vitro and/or in vivo. Cell therapy including the adoptive T cell therapy (ACT) and immunotherapy have been tried against drug-resistant and recurrent HCMV in patients receiving hematopoietic stem cell transplantation (HSCT) or solid organ transplant (SOT), and they have also been used to treat glioblastoma (GBM) associated with HCMV infections. These newly developed antiviral strategies are expected to yield fruitful results and make a significant contribution to the treatment of HCMV infections. Despite this progress, the nucleic acid-based gene-targeting approaches are still under study for basic research, and cell therapy is adopted in a small study population size or only successful in case reports. Additionally, no current drugs have been approved to be indicated for latent infections. Therefore, the next strategy is to develop antiviral strategies to elevate efficacy against acute and/or latent infections and overcome challenges such as toxicity, resistance issues, and side effects. In this review, we would explore the challenges, recent advances and perspectives in the treatment of HCMV infections. Furthermore, the suitable therapeutic strategies as well as the possibility for compassionate use would be evaluated.

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.

Donor-derived cytomegalovirus-cytotoxic T lymphocytes and leflunomide successfully control refractory cytomegalovirus infections and disease of multiple sites after allogeneic-hematopoietic stem cell transplantation: A case report

Drug-resistant cytomegalovirus (CMV) infection after hematopoietic stem cell transplantation (HSCT) often leads to morbidity and mortality. Several studies have shown that CMV-cytotoxic T lymphocytes (CTLs) can overcome drug-resistant CMV infection, but still many questions remain unanswered. Here, we present a case of refractory CMV infection after allogeneic HSCT (allo-HSCT). Donor-derived CMV-CTLs failed to eliminate the virus in unique peripheral blood on the first application, when 70 mg methylprednisolone (MP) was taken per day. After a second attempt with a combination of 8 mg MP with leflunomide, a complete and persisting clearance of all involved sites, including peripheral blood, urinary system, leptomeninges, and retina, was achieved. To summarize, intravenous infusion of CTLs can eliminate CMV in the oculi and central nervous system (CNS), and a low dosage of 8 mg MP has no interaction with CMV-CTLs.

Prevention and management of human cytomegalovirus in pediatric HSCT recipients: A review

Cytomegalovirus (CMV), like other herpesviruses, has the unique ability to establish latent infection with subsequent reactivation during periods of stress and immunosuppression. Herpesviruses cause potentially devastating disease, particularly in hematopoietic stem cell transplant (HSCT) recipients. CMV is especially of concern in HSCT recipients given the high community seroprevalence, high risk of reactivation and high risk of transmission from HSCT donors to recipients causing primary infection after transplantation. The risk of CMV infection and severity of CMV disease varies depending on the underlying disease of the HSCT recipient, donor and recipient CMV status prior to HSCT, type of conditioning therapy in preparation for HSCT, allogeneic versus autologous HSCT, donor graft source, timing of infection in relation to HSCT, and other patient comorbidities. Different strategies exist for prevention (e.g., preemptive therapy vs. universal prophylaxis) as well as management of CMV disease (e.g., antiviral therapy, augmenting immune reconstitution, cytotoxic T-cell therapy). The purpose of this narrative review is to discuss diagnosis, prevention, and management of CMV infection and disease at different stages of HSCT, including key points illustrated through presentations of complex cases and difficult clinical scenarios. Traditional and novel strategies for CMV management will be discussed in the context of these unique clinical cases.