Cytomegalovirus Infection and the Implications of Drug-Resistant Mutations in Pediatric Allogeneic Hematopoietic Stem Cell Transplant Recipients: A Retrospective Study from a Tertiary Hospital in China

Refractory cytomegalovirus infections in Chinese patients receiving allogeneic hematopoietic cell transplantation: a review of the literature

In the absence of prophylactic therapy, cytomegalovirus (CMV) viremia is a common complication following allogeneic hematopoietic cell transplantation (allo-HCT) and represents a significant cause of morbidity and mortality. Approximately 25% of allo-HCT happen in China, where the development and refinement of the 'Beijing protocol' has enabled frequent and increasing use of haploidentical donors. However, refractory CMV infection (an increase by >1 log10 in blood or serum CMV DNA levels after at least 2 weeks of an appropriately dosed anti-CMV medication) is more common among patients with haploidentical donors than with other donor types and has no established standard of care. Here, we review the literature regarding refractory CMV infection following allo-HCT in China.

Genetic Variants Associated with Drug Resistance of Cytomegalovirus in Hematopoietic Cell Transplantation Recipients

Cytomegalovirus (CMV) infection is a serious complication in hematopoietic cell transplantation (HCT) recipients. Drug-resistant strains make it more challenging to treat CMV infection. This study aimed to identify variants associated with CMV drug resistance in HCT recipients and assess their clinical significance. A total of 123 patients with refractory CMV DNAemia out of 2271 HCT patients at the Catholic Hematology Hospital between April 2016 and November 2021 were analyzed, which accounted for 8.6% of the 1428 patients who received pre-emptive therapy. Real-time PCR was used to monitor CMV infection. Direct sequencing was performed to identify drug-resistant variants in UL97 and UL54. Resistance variants were found in 10 (8.1%) patients, and variants of uncertain significance (VUS) were found in 48 (39.0%) patients. Patients with resistance variants had a significantly higher peak CMV viral load than those without (p = 0.015). Patients with any variants had a higher risk of severe graft-versus-host disease and lower one-year survival rates than those without (p = 0.003 and p = 0.044, respectively). Interestingly, the presence of variants reduced the rate of CMV clearance, particularly in patients who did not modify their initial antiviral regimen. However, it had no apparent impact on individuals whose antiviral regimens were changed due to refractoriness. This study highlights the importance of identifying genetic variants associated with CMV drug resistance in HCT recipients for providing appropriate antiviral treatment and predicting patient outcomes.

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

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

[Resistance to antiviral drugs in human viruses from the subfamily Betaherpesvirinae]

The review provides information on the mechanisms of the emergence of resistance to antiviral drugs in human viruses from the subfamily Betaherpesvirinae. Data on the principles of action of antiviral drugs and their characteristics are given. The occurrence rates of viral resistance in various groups of patients is described and information about the possible consequences of the emergence of resistance to antiviral drugs is given. Information is provided regarding the virus genes in which mutations occur that lead to viral resistance, and a list of such mutations that have described so far is given. The significance of the study of mutations leading to the resistance of the virus to antiviral drugs for medical practice is discussed.