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

Viral and Fungal Infections Early After HLA-Mismatched Hematopoietic Stem Cell Transplantation Using Low-Dose Antithymocyte Globulin in High-Risk Patients With Hematological Malignancies Not in Remission

BACKGROUND

In vivo T-cell depletion with antithymocyte globulin (ATG), especially at high-doses has been shown to be associated with increased incidence of infections after allogeneic hematopoietic stem cell transplantation (HSCT). However, it remains unclear whether ATG, even at low-doses increases the risk of posttransplant infections in the high-risk HSCT setting.

PATIENTS AND METHODS

We conducted a single-center retrospective study of viral and fungal infections early after transplantation, using the data from 82 patients with hematological malignancies. Among them, 42 underwent HLA-mismatched HSCT using low-dose (2.5 mg/kg n = 41, 2.0 mg/kg n = 1) thymoglobulin (ATG patients), and 40 control patients received HSCT without ATG (non-ATG patients) during the same period. Cord blood transplantation patients were excluded. All ATG patients had hematological malignancies not in remission at the time of transplantation, and were considered to be at high-risk for posttransplant infections.

RESULTS

There were no appreciable between-group differences in the incidence of clinically significant cytomegalovirus infection (csCMVi), late-onset CMV reactivation after discontinuation of letermovir, invasive fungal diseases or Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disease. Peak values of CMV antigenemia were almost equal in ATG and non-ATG patients. The prevention of csCMVi with letermovir was constant in the 2 groups. However, ATG patients showed earlier reactivation of CMV and higher incidence of EBV viremia than non-ATG patients. Among their underlying diseases, mature T-cell neoplasm was a significant risk factor for CMV/EBV reactivation.

CONCLUSION

The use of low-dose thymoglobulin in HLA-mismatched HSCT for nonremission hematological malignancies is a reasonable strategy under careful monitoring for viral reactivation.

Risk of Cytomegalovirus Infection after 3 or 6 Months of Valganciclovir Prophylaxis among Donor-Seropositive, Recipient-Seronegative Heart Transplant Recipients

Background

Cytomegalovirus (CMV) disease is frequent following heart transplant, especially among patients with donor-seropositive, recipient-seronegative (D+/R-) CMV status. Valganciclovir prophylaxis for 3 to 6 months is recommended, but few data support the use of 6 rather than 3 months of prophylaxis for patients who have undergone heart transplant.

Objective

To compare the risk of CMV infection and a first occurrence of CMV disease after heart transplant among CMV D+/R- patients who received 3 or 6 months of prophylaxis in the first year after transplant.

Methods

This retrospective analysis included every D+/R- heart transplant recipient at the study centre between October 2015 and October 2022. Patients had to have a minimum of 1 year of follow-up for inclusion.

Results

Thirty-five patients met the inclusion criteria. The duration of valganciclovir prophylaxis (determined by the medical team) was 3 months for 22 patients and 6 months for 13 patients. CMV infection occurred in 68.2% (15/22) and 30.8% (4/13) of the 3-month and 6-month groups, respectively (risk difference 37.4%, 95% confidence interval [CI] 1.75 to 65.8, p = 0.04). CMV disease occurred in 54.5% (12/22) of patients who received 3 months of prophylaxis and 23.1% (3/13) of those who received 6 months of prophylaxis (risk difference 31.4%, 95% CI -3.7 to 59.4, p = 0.09). Most CMV infections and diseases occurred in the 3 months after the end of prophylaxis.

Conclusions

After heart transplant, CMV D+/R- patients who received 3 months of prophylaxis had a higher risk of CMV infection and a non-statistically significant higher risk of CMV disease relative to those who received 6 months of prophylaxis.

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.

Case Report: Maribavir for refractory cytomegalovirus viremia after renal transplantation in a child with Schimke's immune-osseous dysplasia

Cytomegalovirus (CMV) is a major opportunistic pathogen in recipients of solid organ transplantation. Maribavir, a pUL97 protein kinase inhibitor, was approved for the treatment of refractory post-transplant CMV infection in the US in 2021. However, it is rarely used in pediatric patients worldwide. Here, we report the case of a Chinese boy with Schimke's immune-osseous dysplasia (SIOD) who developed refractory CMV infection after a renal transplantation. An 11-year-old boy was hospitalized with recurrent abdominal and testicular pain 50 days after renal transplantation. Diagnoses included urinary tract infection, epididymitis, CMV viremia, stage 2 chronic kidney disease, and SIOD. After five days of treatment, his pain improved, but he developed persistent fever and shortness of breath. Blood CMV levels rose to 1.64 × 105 copies/ml after one month of ganciclovir treatment. Significant bone marrow suppression was observed after combined treatment with foscarnet. Anti-rejection treatment was discontinued due to compromised immune function. On day 40, maribavir was initiated with parental consent, resulting in undetectable CMV copies within four days. The patient's clinical status and bone marrow suppression had improved. Continuing maribavir for two weeks led to the disappearance of CMV viremia, no bone marrow suppression, and normal liver and kidney functions. This case demonstrates the successful short-term use of maribavir in the treatment of refractory CMV infection in an immune-deficient child after renal transplantation. Further studies are required to explore the efficacy and safety of maribavir in pediatric patients.

Respiratory infections in lung transplant recipients

PURPOSE OF REVIEW

Morbidity and mortality rates after lung transplantation still remain higher than after other forms of solid organ transplantation, primarily due to a higher risk of infections and the development of chronic lung allograft dysfunction. Thus, a tiered approach highlighting the most significant respiratory pathogens including common opportunistic infections along with diagnostic, treatment and prevention strategies, including vaccination and prophylaxis is needed.

RECENT FINDINGS

The need for intense immunosuppressive therapy to prevent rejection, coupled with the transplanted lung's constant exposure to environment and impaired local defence mechanisms leads to frequent infections. Viral and bacterial infections are most frequent while fungal infections mainly involve the tracheobronchial tract but may be fatal in case of disseminated disease. Some infectious agents are known to trigger acute rejection or contribute to chronic allograft dysfunction. Invasive testing in the form of bronchoscopy with bronchoalveolar lavage is standard and increasing experience in point of care testing is gained to allow early preemptive therapy.

SUMMARY

Timely diagnosis, treatment, and ongoing monitoring are essential, but this can be difficult due to the wide variety of potential pathogens.

Chinese expert consensus on the application of intravenous immunoglobulin in hematological diseases

Intravenous immunoglobulin (IVIG), first developed for the treatment of patients with antibody deficiencies, is now widely used in clinical practice, especially in hematological and immune system diseases, and its application in hematological oncology chemotherapy, cellular immunotherapy and hematopoietic stem cell transplantation (HSCT) is becoming more and more common. The Chinese Collaborative Group for Infection Immunology and Microecology Research Translation Collaborative Group organized relevant experts to discuss and propose the "Chinese expert consensus on the application of intravenous immunoglobulin in hematological diseases," which was formulated based on the progress of research on the application of IVIG in blood diseases, and provides a basis for the standardization of the use of IVIG in hematologic disorders.

Simultaneous Monitoring of 3 Antiviral Drugs in Serum Using Liquid Chromatography-Tandem Mass Spectrometry: Full Validation and Clinical Application

BACKGROUND

Patients undergoing solid organ and hematopoietic stem cell transplantation are at risk of opportunistic pathogenic infections that increase morbidity and mortality. Universal antiviral prophylaxis improves the outcomes in this context. Therapeutic drug monitoring of antiviral drugs is not universally recommended but may be necessary in certain complex or polymorbid patients. The authors aimed to develop and validate a high-performance liquid chromatography-tandem mass spectrometry method to simultaneously quantify ganciclovir, acyclovir, and letermovir in human serum.

METHODS

A stable isotopically labeled internal standard was used for each antiviral drug. Compounds were extracted by protein precipitation, evaporation, and reconstitution in an aqueous mobile phase. Samples were analyzed using reverse-phase chromatography with subsequent detection by electrospray ionization in the positive ion mode on a triple quadrupole mass spectrometer (run time: 6.5 minutes).

RESULTS

Analytical curves for ganciclovir and acyclovir exhibited linearity within 0.1-25 mg/L (R2 > 0.993), whereas for letermovir, the linear range was 0.01-2 mg/L (R2 = 0.999). Matrix effects were not observed. Intraday and interday precision and accuracy were within ±15%. A therapeutic drug monitoring-guided strategy was explored to optimize preemptive antiviral drug therapy in 3 cohorts of transplant recipients. Seventy-nine samples from 35 patients were quantified, revealing median trough concentrations of 0.2 mg/L for ganciclovir (n = 21), 0.28 mg/L for acyclovir (n = 26), and 0.29 mg/L for letermovir (n = 32).

CONCLUSIONS

This method has been successfully applied in clinical settings and allows reliable and accurate drug-level measurements.

Risk of Cytomegalovirus Viremia Following Transplantation of Hepatitis C-Viremic Donor Kidneys Into Uninfected Recipients: A Multi-Center Retrospective Cohort Study

BACKGROUND

Several studies have suggested an increased risk of cytomegalovirus (CMV) viremia among Hepatitis C virus (HCV)-uninfected recipients of kidney transplants from HCV-RNA+ deceased donors (HCV D+/R-), but these studies featured small sample sizes and limited ability to address confounding variables.

METHODS

We assembled a retrospective cohort of adult kidney transplant recipients at five US centers between 4/1/2015 and 12/31/2020 to determine the association between HCV D+/R- transplants and the outcomes of CMV viremia (> 1000 IU/mL), death-censored graft failure, and mortality in the first posttransplant year compared to HCV D-/R- transplants. We generated highly similar matched cohorts of HCV D+/R- and HCV D-/R- recipients based on attributes that affect the risk of CMV viremia. We matched exactly on center, CMV donor/recipient serostatus, and antibody induction therapy.

RESULTS

The cohort comprised 275 HCV D+/R- recipients with a mean age of 52.5 years (SD = 10.7); 19% were CMV D+/R-, and 74% received anti-thymocyte globulin induction. With variable ratio matching, 267 HCV D+/R- recipients were matched to 996 HCV D-/R- recipients. CMV viremia occurred in 15% of HCV D+/R- and 11% of HCV D-R- recipients. In Cox regression, transplantation with an HCV-RNA+ donor kidney was not associated with a significantly higher risk of CMV viremia (HR 1.3, 95% CI 0.89-1.92) or death-censored graft loss (HR 0.61, 95% CI 0.31-1.2).

CONCLUSION

The risk of CMV viremia was not significantly increased among HCV D+/R- kidney recipients. Future studies should examine associations between donor-derived HCV infection and clinical outcomes of CMV syndrome and disease.

Estimation of Ganciclovir Exposure in Adults Transplant Patients by Machine Learning

INTRODUCTION

Valganciclovir, a prodrug of ganciclovir (GCV), is used to prevent cytomegalovirus infection after transplantation, with doses adjusted based on creatinine clearance (CrCL) to target GCV AUC0-24 h of 40-60 mg*h/L. This sometimes leads to overexposure or underexposure. This study aimed to train, test and validate machine learning (ML) algorithms for accurate GCV AUC0-24 h estimation in solid organ transplantation.

METHODS

We simulated patients for different dosing regimen (900 mg/24 h, 450 mg/24 h, 450 mg/48 h, 450 mg/72 h) using two literature population pharmacokinetic models, allocating 75% for training and 25% for testing. Simulations from two other literature models and real patients provided validation datasets. Three independent sets of ML algorithms were created for each regimen, incorporating CrCL and 2 or 3 concentrations. We evaluated their performance on testing and validation datasets and compared them with MAP-BE.

RESULTS

XGBoost using 3 concentrations generated the most accurate predictions. In testing dataset, they exhibited a relative bias of -0.02 to 1.5% and a relative RMSE of 2.6 to 8.5%. In the validation dataset, a relative bias of 1.5 to 5.8% and 8.9 to 16.5%, and a relative RMSE of 8.5 to 9.6% and 10.7% to 19.7% were observed depending on the model used. XGBoost algorithms outperformed or matched MAP-BE, showing enhanced generalization and robustness in their estimates. When applied to real patients' data, algorithms using 2 concentrations showed relative bias of 1.26% and relative RMSE of 12.68%.

CONCLUSIONS

XGBoost ML models accurately estimated GCV AUC0-24 h from limited samples and CrCL, providing a strategy for optimized therapeutic drug monitoring.

Cytomegalovirus infection and cardiovascular outcomes in abdominal organ transplant recipients: A systematic review and meta-analysis

INTRODUCTION

Despite advancements in Cytomegalovirus (CMV) management, its impact on graft function, mortality, and cardiovascular (CV) health of organ transplant recipients (OTR) remains a significant concern. We investigated the association between CMV infection and CV events (CVE) in organ (other than heart) transplant recipients.

METHODS

We conducted a comprehensive literature search in PubMed and EMBASE, including studies that reported on CMV infection or disease and post-transplantation CVE. Studies of heart transplant recipients were excluded.

RESULTS

We screened 3875 abstracts and 12 clinical studies were included in the final analysis, mainly in kidney and liver transplant recipients. A significant association was observed between CMV infection and an increased risk of CVE, with a pooled unadjusted hazard ratio (HR) of 1.99 (95% Confidence Intervals [CI] 1.45-2.73) for CMV infection and 1.59 (95% CI 1.21-2.10) for CMV disease. Pooled adjusted HR were 2.17 (95% CI 1.47-3.20) and 1.77 (95% CI 0.83-3.76), respectively. Heterogeneity was low (I2 = 0%) for CMV infection, suggesting consistent association across studies, and moderate-to-high for CMVdisease (I2 = 50% for unadjusted, 53% for adjusted HR).

DISCUSSION

We found a significant association between CMV infection and CV risk in abdominal OTR, underscoring the importance of proactive CMV surveillance and early treatment. Future research should aim for more standardized methodologies to fully elucidate the relationship between CMV and CV outcomes, potentially informing novel preventive and therapeutic strategies that could benefit the CV health of OTR.

Comprehensive Herpesviruses Antiviral drug Resistance Mutation Database (CHARMD)

A comprehensive and accessible Herpesvirus drug resistance database was designed to serve as an international reference for diagnosis and clinical studies. This database available at https://www.unilim.fr/cnr-herpesvirus/outils/codexmv/includes both resistance-related mutations and natural polymorphisms. Initially designed for human cytomegalovirus, it will be expanded to include herpes simplex and varicella-zoster viruses. Newly published mutations and new mutations reported by users or collaborating expert laboratories will be reviewed by an international committee of reference laboratories before inclusion in the database. Coupled with the Herpesvirus Sequence Analysis tool (HSA) mutation reports from NGS or Sanger sequences, it will be an open source for researchers in the field of Herpesviruses. We hope to fill this unmet need for the development and standardization of resistance genotyping.

Management of cytomegalovirus infection after liver transplantation

Cytomegalovirus (CMV) infection is one of the primary causes of morbidity and mortality following liver transplantation (LT). Based on current worldwide guidelines, the most effective strategies for avoiding post-transplant CMV infection are antiviral prophylaxis and pre-emptive treatment. CMV- IgG serology is the established technique for pretransplant screening of both donors and recipients. The clinical presentation of CMV infection and disease exhibits variability, prompting clinicians to consistently consider this possibility, particularly within the first year post-transplantation or subsequent to heightened immunosuppression. At annual symposia to discuss CMV prevention and how treatment outcomes can be improved, evidence on the incorporation of immune functional tests into clinical practice is presented, and the results of studies with new antiviral treatments are evaluated. Although there are ongoing studies on the use of letermovir and maribavir in solid organ transplantation, a consensus reflected in the guidelines has not been formed. Determining the most appropriate strategy at the individual level appears to be the key to enhancing outcomes. Although prevention strategies reduce the risk of CMV disease, the disease can still occur in up to 50% of high-risk patients. A balance between the risk of infection and disease development and the use of immunosuppressants must be considered when talking about the proper management of CMV in solid organ transplant recipients. The objective of this study was to establish a comprehensive framework for the management of CMV in patients who have had LT.

Immunopathology of lung transplantation: from infection to rejection and vice versa

Lung transplantation offers a lifesaving option for patients with end-stage lung disease, but it is marred by a high risk of post-transplant infections, particularly involving multidrug-resistant bacteria, Cytomegalovirus, and fungal pathogens. This elevated infection rate, the highest among solid organ transplants, poses a significant challenge for clinicians, particularly within the first year post-transplantation, where infections are the leading cause of mortality. The direct exposure of lung allografts to the external environment exacerbates this vulnerability leading to constant immune stimulation and consequently to an elevated risk of triggering alloimmune responses to the lung allograft. The necessity of prolonged immunosuppression to prevent allograft rejection further complicates patient management by increasing susceptibility to infections and neoplasms, and complicating the differentiation between rejection and infection, which require diametrically opposed management strategies. This review explores the intricate balance between preventing allograft rejection and managing the heightened infection risk in lung transplant recipients.

[Xenotransplantation of solid organs]

Transplantation of genetically modified porcine hearts and kidneys could become a solution to the persistent shortage of human organ donors. Progress has been made in genetic engineering of donor pigs, preservation techniques after organ harvesting and immunosuppression using co-stimulation blockade with anti-CD40/CD40L monoclonal antibodies. Progress has also been made in in the development of methods that detect pathogenic porcine viruses and prevent their transmission to the recipient. As normal land breed pig organs continue to grow in the recipient to their original size, different pig breeds (such as Auckland Island pigs) are now used which reach a final size suitable for humans. Alternatively, a knock-out of the growth hormone receptor gene has been established, e.g., in the 10GM genetically modified pigs from Revivicor/United Therapeutics, USA. The first clinical pilot studies including patients suffering from terminal heart failure are expected to start in Germany in about 2 years.

Current Status of Cardiac Xenotransplantation: Report of a Workshop of the German Heart Transplant Centers, Martinsried, March 3, 2023

This report comprises the contents of the presentations and following discussions of a workshop of the German Heart Transplant Centers in Martinsried, Germany on cardiac xenotransplantation. The production and current availability of genetically modified donor pigs, preservation techniques during organ harvesting, and immunosuppressive regimens in the recipient are described. Selection criteria for suitable patients and possible solutions to the problem of overgrowth of the xenotransplant are discussed. Obviously microbiological safety for the recipient and close contacts is essential, and ethical considerations to gain public acceptance for clinical applications are addressed. The first clinical trial will be regulated and supervised by the Paul-Ehrlich-Institute as the National Competent Authority for Germany, and the German Heart Transplant Centers agreed to cooperatively select the first patients for cardiac xenotransplantation.

Evaluation of an automated real-time transcription-mediated amplification (TMA) assay for detection and quantification of cytomegalovirus DNA in different clinical specimens

BACKGROUND

Reliable and fast detection and quantification of human cytomegalovirus (CMV) DNA in various diagnostic specimens is essential for care of immunocompromised or congenitally infected individuals.

OBJECTIVES

To evaluate the analytical and clinical performance of the Panther Aptima® CMV (Hologic) quantitative real-time transcription mediated amplification (TMA) assay.

STUDY DESIGN

Performance of the TMA assay run on the Hologic Panther Fusion was analysed for 32 proficiency testing samples and 21 quantitative reproducibility panel samples; additionally, we compared results of TMA assay and routine quantitative real-time PCR assays ("PCR-A"= Biomérieux CMV R-gene® or "PCR-B"= Laboratory-developed CMV-PCR) in 518 diagnostic specimens (254 plasma, 120 EDTA whole blood, 43 urine, 45 amniotic fluid and 56 breast milk) at two university hospital laboratories.

RESULTS

All proficiency panel samples were correctly identified and quantified by the TMA assay; replicate testing of the reproducibility panel samples showed good reproducibility within and between the two laboratories. Sensitivity in plasma and WB was higher for the TMA assay detecting low-level CMV-DNAemia in samples tested negative by routine PCR. Quantitative CMV-DNAemia values correlated well between TMA and real-time PCR. Similarly, urine, AF and BM specimens showed a high rate of concordant results (91%, 98% and 98%, respectively) among TMA and PCR with good correlation of quantitative values.

CONCLUSION

The performance of the Aptima® CMV TMA assay for viral blood load testing compared well to established real-time PCRs. In addition, it can be useful for diagnostics in urine, amniotic fluid and breast milk specimens.

Immunosuppressive strategies in face and hand transplantation: a comprehensive systematic review of current therapy regimens and outcomes

Background

Recipients of Vascularized Composite Allotransplants require effective immunosuppressive therapy to prevent graft rejection. This systematic review summarizes the current body of literature on immunosuppressive regimens used in face and hand transplants while summarizing their outcome in terms of rejection, renal failure, and infections.

Methods

A systematic search of electronic databases was conducted to identify relevant studies from 1998 until July 1st, 2023. We included all studies that discussed immunosuppressive strategies in face and hand transplant recipients according to PRISMA.

Results

The standard triple maintenance therapy was mostly adjusted due to nephrotoxicity or high incidence of rejection. The most common alternative treatments utilized were sirolimus (25/91; 27.5%) or everolimus (9/91; 9.9%) following hand- and photophoresis (7/45; 15.6%), sirolimus (5/45; 11.1%) or belatacept (1/45; 2.2%) following face transplantation. Episodes of rejection were reported in 60 (65.9%) of hand- and 33 (73%) of face transplant patients respectively. Graft loss of 12 (13.2%) hand and 4 (8.9%) face transplants was reported. Clinical CMV infection was observed in 6 (6.6%) hand and 7 (15.5%) face transplant recipients.

Conclusions

Based on the herein presented data, facial grafts exhibited a heightened incidence of rejection episodes and CMV infections. Facial mucosa adds complexity to the immunological graft composition highlighting the need of individualized immunosuppressive regimens and further research.

Cytomegalovirus Cell-mediated Immunity Assays in Pediatric Transplantation

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in pediatric transplantation. However, currently utilized CMV prevention paradigms have limitations, leading to research aimed at novel strategies for mitigation of CMV infection. Cell-mediated immunity (CMI) is crucial in controlling CMV infection and the use of CMV-specific CMI assays to guide prevention and treatment of CMV infection in both solid organ transplant and hematopoietic cell transplant recipients shows great promise. In this article, we review the immune response to CMV infection to highlight the rationale for CMI assays, describe available commercial assays and strategies for their use, and summarize relevant literature regarding the use of CMI assays in transplant recipients.

Development of a highly cytotoxic, clinical-grade virus-specific T cell product for adoptive T cell therapy

At present, recipients of allogeneic hematopoietic stem-cells are still suffering from recurrent infections after transplantation. Infusion of virus-specific T cells (VST) post-transplant reportedly fights several viruses without increasing the risk of de novo graft-versus-host disease. This study targeted cytomegalovirus (CMV) for the development of an innovative approach for generating a very specific VST product following Good Manufacturing Practices (GMP) guidelines. We used a sterile disposable compartment named the Leukoreduction System Chamber (LRS-chamber) from the apheresis platelet donation kit as the starting material, which has demonstrated high levels of T cells. Using a combination of IL-2 and IL-7 we could improve expansion of CMV-specific T cells. Moreover, by developing and establishing a new product protocol, we were able to stimulate VST proliferation and favors T cell effector memory profile. The expanded VST were enriched in a closed automated system, creating a highly pure anti-CMV product, which was pre-clinically tested for specificity in vitro and for persistence, biodistribution, and toxicity in vivo using NOD scid mice. Our results demonstrated very specific VST, able to secrete high amounts of interferon only in the presence of cells infected by the human CMV strain (AD169), and innocuous to cells partially HLA compatible without viral infection.

Letermovir Rescue Therapy in Kidney Transplant Recipients with Refractory/Resistant CMV Disease

(1) Background: CMV infections remain a problem after kidney transplantation, particularly if patients are refractory or resistant (r/r) to treatment with valganciclovir (VGCV) or ganciclovir (GCV). (2) Methods: In a single-center retrospective study, kidney transplant recipients (KTR) receiving letermovir (LTV) as rescue therapy for VGCV-/GCV-r/r CMV disease were analyzed regarding CMV history, immunosuppression, and outcomes. (3) Results: Of 201 KTR treated for CMV between 2017 and 2022, 8 patients received LTV following treatment failure with VGCV/GCV. All patients received CMV prophylaxis with VGCV according to the center's protocol, and 7/8 patients had a high-risk (D+/R-) CMV constellation. In seven of eight cases, rising CMV levels occurred during prophylaxis. In seven of eight patients, a mutation in UL97 associated with a decreased response to VGCV/GCV was detected. In four of eight patients, LTV resulted in CMV clearance after 24 ± 10 weeks (16-39 weeks), two of eight patients stabilized at viral loads <2000 cop/mL (6-20 weeks), and two of eight patients developed LTV resistance (range 8-10 weeks). (4) Conclusion: LTV, which is currently evaluated for CMV prophylaxis in kidney transplantation, also shows promising results for the treatment of patients with VGCV/GCV resistance despite the risk of developing LTV resistance. Additional studies are needed to further define its role in the treatment of patients with CMV resistance.

Body surface area compared to body weight dosing of valganciclovir is associated with increased toxicity in pediatric solid organ transplantation recipients

Optimal dosing of valganciclovir (VGCV) for cytomegalovirus (CMV) prevention in pediatric solid organ transplantation recipients (SOTR) is controversial. Dosing calculated based on body surface area (BSA) and creatinine clearance is recommended but simplified body weight (BW) dosing is often prescribed. We conducted a retrospective 6-center study to compare safety and efficacy of these strategies in the first-year posttransplant There were 100 (24.2%) pediatric SOTR treated with BSA and 312 (75.7%) with BW dosing. CMV DNAemia was documented in 31.0% vs 23.4% (P = .1) at any time during the first year and breakthrough DNAemia in 16% vs 12.2% (P = .3) of pediatric SOTR receiving BSA vs BW dosing, respectively. However, neutropenia (50% vs 29.3%, P <.001), lymphopenia (51% vs 15.0%, P <.001), and acute kidney injury causing treatment modification (8.0% vs 1.8%, P <.001) were documented more frequently during prophylaxis in pediatric SOTR receiving BSA vs BW dosing. The adjusted odds ratio of VGCV-attributed toxicities comparing BSA and BW dosing was 2.3 (95% confidence interval [CI], 1.4-3.7] for neutropenia, 7.0 (95% CI, 3.9-12.4) for lymphopenia, and 4.6 (95% CI, 2.2-9.3) for premature discontinuation or dose reduction of VGCV, respectively. Results demonstrate that BW dosing is associated with significantly less toxicity without any increase in CMV DNAemia.

Cytomegalovirus Cell-Mediated Immunity: Ready for Routine Use?

Utilizing assays that assess specific T-cell-mediated immunity against cytomegalovirus (CMV) holds the potential to enhance personalized strategies aimed at preventing and treating CMV in organ transplantation. This includes improved risk stratification during transplantation compared to relying solely on CMV serostatus, as well as determining the optimal duration of antiviral prophylaxis, deciding on antiviral therapy when asymptomatic replication occurs, and estimating the risk of recurrence. In this review, we initially provide an overlook of the current concepts into the immune control of CMV after transplantation. We then summarize the existent literature on the clinical experience of the use of immune monitoring in organ transplantation, with a particular interest on the outcomes of interventional trials. Current evidence indicates that cell-mediated immune assays are helpful in identifying patients at low risk for replication for whom preventive measures against CMV can be safely withheld. As more data accumulates from these and other clinical scenarios, it is foreseeable that these assays will likely become part of the routine clinical practice in organ transplantation.

Amplicon size and non-encapsidated DNA fragments define plasma cytomegalovirus DNA loads by automated nucleic acid testing platforms: A marker of viral cytopathology?

Management of cytomegalovirus (CMV) in transplant patients relies on measuring plasma CMV-loads using quantitative nucleic acid testing (QNAT). We prospectively compared the automated Roche-cobas®6800-CMV and Roche-CAP/CTM-CMV with laboratory-developed Basel-CMV-UL54-95bp, and Basel-CMV-UL111a-77bp. Roche-cobas®6800-CMV and Roche-CAP/CTM-CMV were qualitatively concordant in 142/150 cases (95%). In-depth comparison revealed higher CMV-loads of the laboratory-developed assay and correlated with smaller amplicon size. After calibration to the 1.WHO-approved CMV international standard, differences were reduced but remained significant. DNase-I pretreatment significantly reduced CMV-loads for both automated Roche-CAP/CTM-CMV and Roche-cobas®6800-CMV assays, whereby 90% and 95% of samples became undetectable. DNase-I pretreatment also reduced CMV-loads quantified by Basel-CMV-UL54-95bp and Basel-CMV-UL111a-77bp, but remaining detectable in 20% and 35%, respectively. Differences were largest for 110 samples with low-level CMV-DNAemia being detectable but not-quantifiable by Roche-cobas®6800-CMV, whereby the smaller amplicon sizes yielded higher viral loads for concordant positives. We conclude that non-encapsidated fragmented CMV-DNA is the major form of plasma CMV-loads also measured by fully-automated platforms. Amplicons of <150 bp and calibrators are needed for reliable and commutable QNAT-results. We hypothesize that non-encapsidated fragmented CMV-DNA results from lysis of CMV-replicating cells and represent a direct marker of viral cell damage, which contribute to delayed viral load responses despite effective antivirals.

Thioxothiazolo[3,4-a]quinazoline derivatives inhibit the human cytomegalovirus alkaline nuclease

Human cytomegalovirus (HCMV, human herpesvirus 5) is an opportunistic pathogen responsible for serious disease in immunocompromised patients. Current antiviral therapies rely predominantly on drugs interfering with viral DNA replication and packaging. However, the serious side effects of existing drugs and the emergence of drug resistance indicate the need for new targets for anti-HCMV therapy. One such target is the viral alkaline nuclease (AN), an enzyme highly conserved among the Herpesviridae. In this study, we validated the HCMV AN, encoded by the viral UL98 open reading frame, as a drug target by demonstrating that a UL98-deficient HCMV mutant is severely attenuated and shows a reduced ability to spread in cell culture. We established a fluorescence-based enzyme assay suitable for high-throughput screening and used it on a small-molecule compound library. The most promising hit, a thioxothiazolo[3,4-a]quinazoline derivative, blocked AN activity in vitro and inhibited HCMV replication in plaque reduction (PRA) and fluorescence reduction assays (FRA). Several derivatives of the hit compound were tested, some of which had similar or better inhibitory activities. The most potent derivative of hit scaffold A, compound AD-51, inhibited HCMV replication with a 50% effective concentrations (EC50) of 0.9 μM in the FRA and 1.1 μM in the PRA. AD-51 was also active against ganciclovir, foscarnet, and letermovir-resistant HCMVs. Moreover, it inhibited herpes simplex virus, Kaposi's sarcoma-associated herpesvirus, and murine CMV, a mouse virus serving as a model for HCMV. These results suggest that thioxothiazolo[3,4-a]quinazoline derivatives are a new class of herpesvirus inhibitors targeting the viral AN.

Current Perspectives on the Management of Herpesvirus Infections in Solid Organ Transplant Recipients

Solid organ transplant recipients (SOTRs) are at high risk of human herpesvirus (HHV)-related morbidity and mortality due to the use of immunosuppressive therapy. We aim to increase awareness and understanding of HHV disease burden in SOTRs by providing an overview of current prevention and management strategies as described in the literature and guidelines. We discuss challenges in both prevention and treatment as well as future perspectives.

Hematopoietic stem cells and betaherpesvirus latency

The human betaherpesviruses including human cytomegalovirus (HCMV), human herpesvirus (HHV)-6a and HHV-6b, and HHV-7 infect and establish latency in CD34+ hematopoietic stem and progenitor cells (HPCs). The diverse repertoire of HPCs in humans and the complex interactions between these viruses and host HPCs regulate the viral lifecycle, including latency. Precise manipulation of host and viral factors contribute to preferential maintenance of the viral genome, increased host cell survival, and specific manipulation of the cellular environment including suppression of neighboring cells and immune control. The dynamic control of these processes by the virus regulate inter- and intra-host signals critical to the establishment of chronic infection. Regulation occurs through direct viral protein interactions and cellular signaling, miRNA regulation, and viral mimics of cellular receptors and ligands, all leading to control of cell proliferation, survival, and differentiation. Hematopoietic stem cells have unique biological properties and the tandem control of virus and host make this a unique environment for chronic herpesvirus infection in the bone marrow. This review highlights the elegant complexities of the betaherpesvirus latency and HPC virus-host interactions.

Comparison of intracellular cytokine staining versus an ELISA-based assay to assess CMV-specific cell-mediated immunity in high-risk kidney transplant recipients

The best method for monitoring cytomegalovirus (CMV)-specific cell-mediated immunity (CMV-CMI) among high-risk kidney transplant (KT) recipients remains uncertain. We assessed CMV-CMI by intracellular cytokine staining (ICS) by flow cytometry and a commercial interferon (IFN)-γ release assay (QuantiFERON®-CMV [QTF-CMV]) at posttransplant months 3, 4, and 5 in 53 CMV-seropositive KT recipients that had received induction therapy with antithymocyte globulin (ATG) and a 3-month course of valganciclovir prophylaxis. The discriminative capacity (areas under receiver operating characteristics curve [auROCs]) and diagnostic accuracy to predict immune protection against CMV infection from the discontinuation of prophylaxis to month 12 were compared between both methods. There was significant although moderate correlations between CMV-specific IFN-γ-producing CD8⁺ T-cell counts enumerated by ICS and IFN-γ levels by QTF-CMV at months 3 (rho: 0.493; p = 0.005) and 4 (rho: 0.440; p = 0.077). The auROCs for CMV-specific CD4⁺ and CD8⁺ T-cells by ICS were nonsignificantly higher than that of QTF-CMV (0.696 and 0.733 vs. 0.678; p = 0.900 and 0.692, respectively). The optimal cut-off of ≥0.395 CMV-specific CD8⁺ T-cells yielded a sensitivity of 86.4%, specificity of 54.6%, positive predictive value of 79.2% and negative predictive value of 66.7% to predict protection. The corresponding estimates for QTF-CMV (IFN-γ levels ≥0.2 IU/mL) were 78.9%, 37.5%, 75.0%, and 42.9%, respectively. The enumeration of CMV-specific IFN-γ-producing CD8⁺ T-cells at the time of cessation of prophylaxis performed slightly better than the QTF-CMV assay to predict immune protection in seropositive KT recipients previously treated with ATG.