CMV-seropositive Recipients Research Articles

Peptide Sharing Between CMV and Mismatched HLA Class I Peptides Promotes Early T-Cell-Mediated Rejection After Kidney Transplantation.

Cytomegalovirus (CMV) infection is related to acute rejection and graft loss after kidney transplantation, though the underlying mechanism remains largely unknown. Some CMV strains produce a peptide that is identical to a peptide sequence found in the leader peptide of specific HLA-A and -C alleles. In this retrospective study of 351 kidney transplantations, we explored whether CMV-seropositive recipients without the VMAPRTLIL, VMAPRTLLL or VMAPRTLVL HLA class I leader peptide receiving a transplant from a donor with this peptide, faced an increased risk of T-cell-mediated rejection (TCMR) in the first 90 days after transplantation. An independent case-control cohort was used for validation (n = 122). The combination of recipient CMV seropositivity with the VMAPRTLIL peptide mismatch was associated with TCMR with a hazard ratio (HR) of 3.06 (p = 0.001) in a multivariable analysis. Similarly, the VMAPRTLLL peptide mismatch was associated with TCMR revealing a HR of 2.61 (p = 0.008). Transplantations featuring either a VMAPRTLIL or a VMAPRTLLL peptide mismatch had a significantly higher cumulative TCMR incidence (p < 0.0001), with the primary impact observed in the first 2 weeks post-transplantation. The findings could be validated in an independent cohort. Together, our data strongly suggest that CMV-positive recipients without an HLA peptide identical to a CMV peptide yet transplanted with a donor who does possess this peptide, have a significantly increased risk of early TCMR. Considering the prevention of such an leader peptide mismatch in these patients or adjusting immunosuppression protocols accordingly may hold promise in reducing the incidence of early TCMR.

Belatacept-related cytomegalovirus infection: Advocacy for tailored immunosuppression based on individual assessment of immune fitness

Belatacept, a fusion protein combining CTLA-4 and the Fc region of human IgG1, is increasingly used as a calcineurin inhibitor–sparing regimen in patients with chronic graft dysfunction. Older kidney transplant recipients, particularly from expanded criteria donors, may be switched to belatacept due to poor renal recovery. However, late-onset cytomegalovirus (CMV) reactivation is increasingly reported with this treatment, especially in older patients with graft dysfunction. This suggests a progressive loss of CMV-specific T cell response, potentially driven by T cell exhaustion. Contributing factors include preexisting T cell dysfunction, increased viral antigen exposure, and interference in the PD-L1/PD-1 pathway by belatacept. mTOR inhibitors have shown efficacy in preventing CMV reactivation by reinvigorating CMV-specific T cells. These findings support combining belatacept with mTOR inhibitors in high-risk CMV-seropositive recipients and emphasize the need for personalized immune assessments to guide immunosuppressive strategies.

Evaluating longitudinal cytomegalovirus-specific humoral immune responses and association with DNAemia risk in seropositive lung transplant recipients

BackgroundCytomegalovirus (CMV) is the most common viral infection among lung transplant recipients and is associated with chronic lung allograft dysfunction. There is a need for better therapeutics as well as biomarkers to enable effective stratification of CMV seropositive patient risk for developing CMV DNAemia to inform prophylaxis duration. MethodsCMV-specific IgG binding and functional responses were evaluated in a discovery cohort of longitudinal plasma samples from 51 CMV seropositive human lung transplant recipients, collected as part of the CTOT-20 and CTOT-22 consortium studies. Pre-transplant plasma from an additional 43 CMV seropositive lung transplant recipients were evaluated as a validation cohort. ResultsIn the discovery cohort with longitudinal samples, pre-transplant plasma IgG binding to CMV surface glycoproteins gH/gL, gH/gL/gO, and pentameric complex (PC), as well as neutralization of CMV in epithelial cells are associated with increased risk of CMV DNAemia post-prophylaxis. However, these results were not confirmed by the validation cohort. ConclusionWhile quantification of pre-transplant CMV-specific antibody responses showed association with DNAemia in the discovery cohort, additional clinical variables and/or known risk factors for CMV, such as patient CMV-specific T-cell responses, may need to be considered in combination with humoral immunity to effectively stratify risk of CMV DNAemia.

Dynamics of cytomegalovirus-specific T-cell recovery in allogeneic hematopoietic cell transplant recipients using a commercially available flow cytometry assay: A pilot study.

Cytomegalovirus-specific T-cell-mediated immunity (CMV-CMI) protects from CMV infection in allogeneic hematopoietic cell transplantation (allo-HCT), but to date, there is no validated measure of CMV immunity for this population. In this prospective, observational, pilot study, CMV T-cell responses were evaluated monthly and at onset of graft-versus-host disease (GVHD) or CMV infection in CMV-seropositive allo-HCT recipients using a commercial flow cytometry assay, the CMV inSIGHT T-Cell Immunity Panel (CMV-TCIP). The primary endpoint was the time to first positive CMV-TCIP, defined as percentage of interferon-γ-producing CD4+ or CD8+ CMV-specific T cells >0.2%. Letermovir was prescribed from day +10 to ≥100. Twenty-eight allo-HCT recipients were enrolled. The median time to first positive CMV-TCIP result was earlier for CD4+ (60 days [interquartile range, IQR 33‒148]) than for CD8+ T cells (96 days [IQR 33‒155]) and longer for haploidentical and mismatched transplant recipients (77 and 96 days, respectively) than for matched donors (45 and 33 days, respectively). CD4+ and CD8+ CMV-CMI recovery was sustained in 10/10 (100%) and 10/11 (91%) patients, respectively, without GVHD, whereas CD4+ and/or CD8+ CMV-CMI was lost in 4/6 and 2/6 patients, respectively, with GVHD requiring steroids. As a predictor of clinically significant CMV infection in patients with low-level CMV reactivation, the sensitivity and negative predictive value of CMV-TCIP were 90% and 87.5%, respectively, for CD4+ CMV-TCIP and 66.7% and 62.5%, respectively, for CD8+ CMV-TCIP. There was significant variability in time to CMV-CMI recovery post-HCT, with slower recovery after haploidentical and mismatched HCT. CD4+ CMV-CMI may protect against CS-CMVi, but immunity may be lost with GVHD diagnosis and treatment.

Mortality in recipients of allogeneic haematopoietic cell transplantation in the era of cytomegalovirus primary prophylaxis: a single-centre retrospective experience

ObjectivesAllogeneic haematopoietic cell transplant (allo-HCT) recipients who are cytomegalovirus (CMV)-seronegative have better post-transplant outcomes than CMV-seropositive recipients. Letermovir (LTV) is approved for CMV primary prophylaxis in adults who are CMV-seropositive after allo-HCT, and its use is associated with improved long-term post-transplant outcomes. We analysed whether LTV has affected the relationship between CMV serostatus and post-transplant outcomes. MethodsWe conducted a retrospective single-centre cohort study of allo-HCT recipients, stratified according to donor (D) and recipient (R). CMV serostatus and the use of LTV: D−/R−, R+/LTV−, and R+/LTV+. Outcomes measured were all-cause and non-relapse mortality, clinically significant CMV infection, graft-versus-host disease, and relapse up to week 48 after allo-HCT. The D−/R− group served as the reference for comparisons in univariate, competing risk regression, and cumulative incidence functions. ResultsThe analysis included 1071 consecutive allo-HCT recipients: 131 D−/R−, 557 R+/LTV−, and 383 R+/LTV+. All-cause mortality by day 100 was 6.1% for the D−/R− group, compared with 14.0% (p 0.024) and 7.8% (p 0.7) for the R+/LTV− and R+/LTV + groups, respectively. Non-relapse mortality by day 100 was 11.0%, 6.8% and 3.8% for R+/LTV−, R+/LTV+, and D−/R− groups, respectively, without significant difference. When including relapse as a competing event, the hazard ratio for non-relapse mortality was 1.83 (95% CI: 1.12–2.99, p 0.017) for R+/LTV− compared with D−/R− and 1.05 (95% CI 0.62–1.77, p 0.85) for R+/LTV + compared with D−/R−. DiscussionCMV primary prophylaxis with LTV abrogated the mortality gap based on CMV serostatus, a protective effect that persisted after discontinuation of primary prophylaxis.

Real-Life Data on the Efficacy and Safety of Letermovir for Primary Prophylaxis of Cytomegalovirus in Allogeneic Hematopoietic Stem Cell Recipients: A Single-Center Analysis

Cytomegalovirus (CMV) reactivation is a life-threatening complication after allogeneic hematopoietic stem cell transplantation (HSCT). Introduction of letermovir (LMV) seems to improve post-transplant outcomes, but delayed-onset CMV reactivation still remains a challenge. In this study, we report on our first experience with LMV prophylaxis in 93 CMV-seropositive adult patients receiving HSCT in our center. We retrospectively analyzed the data of 93 adult CMV-seropositive recipients receiving LMV as CMV prophylaxis after HSCT for hematological malignancies between 2019 and 2023. The starting LMV dose was 480 mg daily, reduced to 240 mg daily for those receiving cyclosporin A co-administration. CMV DNA in the blood was measured by real-time polymerase chain reaction weekly for the first 2 months after transplantation, then every other week until the end of immunosuppressive treatment. LMV was continued to day +100 or to CMV reactivation. The median recipient age at the time of transplant was 51 (range: 20-71) years. All patients received grafts from peripheral blood, mostly for acute myeloid leukemia (60%). The median time from transplantation to LMV initiation was 3 (range: 0-24) days. While 55% of patients were transplanted from matched related donors, 32% had unrelated donors and 13% underwent haploidentical HSCT. Four patients (4%) had CMV “blips” while on LMV, but the drug was continued and repeated assays were negative. Only 2 patients (2%) experienced CMV reactivation while on LMV, on days 48 and 34 after HSCT, respectively. Seven patients (7%) developed late-onset CMV reactivation after a median of 124 days after HSCT (range: 118-152 days) and they were successfully treated with ganciclovir. CMV disease was not observed. Grade III-IV acute graft-versus-host disease occurred in 6 patients (6%) during LMV treatment. LMV treatment was free of side effects. LMV prophylaxis was effective in preventing CMV reactivation with a favorable safety profile. CMV reactivation occurred mostly after LMV discontinuation; thus, extending the duration of prophylaxis beyond 100 days could be beneficial.

Late CMV Disease after Hematopoietic Cell Transplantation: Significance of Post-Transplant Cyclophosphamide, Steroid Treatment and CMV Viral Load

Introduction: Pre-emptive therapy (PET) and letermovir prophylaxis are effective in preventing CMV disease within the first 100 days after allogeneic hematopoietic cell transplantation (HCT), and are widely used worldwide. However, both strategies are associated with late-onset CMV disease. The goal of this study was to determine the period of risk, clinical manifestations, risk factors for initial and recurrent late CMV disease at key landmark time points, and its impact on mortality. Patients and Methods: We retrospectively analyzed CMV seropositive allogeneic HCT recipients transplanted between 2001 and 2017 who survived more than 100 days post HCT. All patients underwent PCR monitoring and PET before day 100 and for patients deemed at high risk for late CMV complications continuation of PCR monitoring and PET was recommended. Data were collected via medical record review of CMV disease and viremia, PET, transplant variables such as lymphopenia, corticosteroid use, donor type, stem cell source, type of underlying disease, and outcomes for 2 years post-transplantation. Cumulative incidence curves and Cox proportional hazards models were used to evaluate time to event and risk factors for late CMV disease and mortality. Results: Among 2155 day 100 survivors, 166 episodes of late CMV disease were observed in 144 (6.7%, 95% CI 5.7%-7.8%) patients. Most of the cases were diagnosed between day 100 and 1 year (126 cases), 40 episodes occurred within the second year (1.6% 95%CI 1.2%-2.3%) post HCT (Figure 1). CMV gastrointestinal (GI) disease (3.4%, 95% CI 2.7%-4.2%) was the most common manifestation of late CMV disease, followed by CMV pneumonia (2.9%, 95% CI 2.2%-3.7%), occurring at a median of 196 days after HCT for first GI disease episode (range 104-685) and 211 days (range 105-574) for first late pneumonia. Twenty-nine patients (10.5%, 95% CI 7%-14.7%) developed recurrent CMV disease. Most recurrences involved the same anatomical site as the first episode with a median of 126 days (range 52-444) after the initial event. Five patients developed a third episode, with a median of 145 (range 85-350) days after their second episode. Prolonged CMV surveillance was recommended in 1787 (83%) cases. High risk patients included: cord blood recipients , in vivo T-cell depletion, acute or chronic GvHD requiring steroid treatment, or those who were treated due to CMV infection before day 100. Based on day 100 risk stratification, cumulative incidence of late CMV disease occurred in 7.6% (95% CI 6.4%-8.9%) and 2.8% (95% Ci 1.4%-4.8%) in high and low risk groups, respectively. In a subgroup analysis (HCT 2001-2011), adherence to late CMV surveillance recommendations was reduced: by week 20 post-HCT, approximately 6 weeks post-discharge, only 65% of patients had CMV PCR tests performed. By 1-year post-HCT, only 40% of patients were still being tested. In multivariable analyses, steroid treatment after day 100 at a dose of ≥1mg/kg, post-transplant cyclophosphamide, GvHD prior day 100, and CMV viremia before day 100 were associated with increased risk of late CMV disease. (Figure 2). The only factors contributing to recurrence of CMV disease were HLA mismatched donor status (aHR 2.92, 95% CI 1.03-8.28) and treatment with high dose steroids ≥1mg/kg after day 100 (as time dependent variable) (aHR 7.60, 95% CI 3.32-17.4). In a landmark analysis of 1-year survivors, the risk of late CMV disease was increased in chronic GvHD patients (aHR 2.11, 95% CI 0.99-4.51, p=0.054) and those with a CMV disease episode prior to 1 year (aHR 2.80, 95% CI 1.23-6.40). Among 144 patients with late CMV disease, 32 (22%) died within 6 weeks of diagnosis of the last episode. Patients who developed late CMV pneumonia were at the highest risk of death by year 2 after HCT (aHR 4.08, 95% CI 2.62-6.35), while GI disease was associated with a somewhat lower risk (aHR 1.62, 95% CI 1.05-2.5). Conclusion: In a large cohort for which late surveillance and PET was recommended, late CMV disease occurred frequently, and was associated with the use of high dose steroids, post-transplant cyclophosphamide, and CMV reactivation before day 100. Late CMV pneumonia and GI disease were associated with overall mortality. Improved strategies to prevent late CMV disease are needed in high-risk patients, including continued antiviral prophylaxis or surveillance strategies that are more suitable for the late setting, such as home-based CMV testing.

QuantiFERON-CMV as a Predictor of CMV Events During Preemptive Therapy in CMV-seropositive Kidney Transplant Recipients.

Prevention of cytomegalovirus (CMV) infection after kidney transplantation is costly and burdensome. Given its promising utility in risk stratification, we evaluated the use of QuantiFERON-CMV (QFCMV) and additional clinical variables in this prospective cohort study to predict the first clinically significant CMV infection (CS-CMV, ranging from asymptomatic viremia requiring treatment to CMV disease) in the first posttransplant year. A cost-effectiveness analysis for guided prevention was done. One hundred adult kidney transplant recipients, CMV IgG + , were given basiliximab induction and maintained on steroid/mycophenolate/tacrolimus with weekly CMV monitoring. Thirty-nine patients developed CS-CMV infection (viral syndrome, n = 1; end-organ disease, n = 9; and asymptomatic viremia, n = 29). A nonreactive or indeterminate QFCMV result using the standard threshold around day 30 (but not before transplant) was associated with CS-CMV rates of 50% and 75%, respectively. A higher QFCMV threshold for reactivity (>1.0 IU interferon-γ/mL) outperformed the manufacturer's standard (>0.2 IU interferon-γ/mL) in predicting protection but still allowed a 16% incidence of CS-CMV. The combination of recipient age and type of donor, along with posttransplant QFCMV resulted in a prediction model that increased the negative predictive value from 84% (QFCMV alone) to 93%. QFCMV-guided preemptive therapy was of lower cost than preemptive therapy alone ( P < 0.001, probabilistic sensitivity analysis) and was cost-effective (incremental net monetary benefit of 210 USD) assuming willingness-to-pay of 2000 USD to avoid 1 CMV disease. Guided CMV prevention by the prediction model with QFCMV is cost-effective and would spare from CMV surveillance in 42% of patients with low risk for CS-CMV.

Using a commercially available assay that measures cytomegalovirus (CMV)-specific T-cell immunity to predict protection against CMV: A prospective, blinded clinical study

The Viracor CMV-T-cell immunity Panel (TCIP) measures %CMV-specific CD4+ and CD8+ T-cells. In this blinded clinical study, we evaluated the performance of the TCIP in predicting CMV events. Prospectively enrolled donor or recipient CMV-seropositive kidney transplant recipients (KTR) were evaluated with monthly TCIP testing until either discontinuation of valganciclovir prophylaxis or CMV DNAemia prompting treatment initiation. Also, prospectively enrolled KTR with low-level untreated DNAemia or after completion of treatment were evaluated for progression or relapse of CMV infection. Among 46 KTR, those with CMV events had significantly lower %CMV-specific CD8+ T-cells (p = 0.024), and the CMV protection ROC AUC was significant (AUC 0.78, p = 0.026). The positive predictive values of CD4+ and CD8+ T-cell positivity >0.2 % for CMV protection were: 96.3 % for CMV DNAemia prompting treatment initiation, 92.6 % for any DNAemia, 100 % for DNAemia >1000 IU/mL. The TCIP could be a useful adjunct tool in individualized management of CMV infection.

Letermovir Prophylaxis Reduced Cytomegalovirus Reactivation and Resistance Post Umbilical Cord Blood Transplantation

Objective: Umbilical cord blood transplantation (UCBT) has proved to be an effective treatment with its own unique advantages nowadays, while long-lasting immunosuppression and delayed immune recovery make the UCBT recipients susceptible to a range of infections. Human cytomegalovirus (HCMV) is the main cause of viral complications post transplantation, which is associated with poor prognosis. Although the implementation of pre-emptive therapy (PET) has significantly reduced the incidence of CMV disease, the long-time antigenemia and the toxicity of antiviral drug remains challenging and risky. Letermovir (LET), a kind of CMV DNA terminase complex inhibitor, is a relatively new antiviral drug for prophylaxis against CMV and has received positive opinion in adult CMV-seropositive recipients of allogeneic haematopoietic stem cell transplant (allo-HSCT). Nevertheless, the clinical efficacy of LET prophylaxis on CMV reactivation and resistance post UCBT remained unknown. Methods: We retrospectively analyzed 43 UCBT patients with hematological diseases at the First Affiliated Hospital of University of Science and Technology of China between August 2022 and May 2023, who received LET prophylaxis since the first day post transplantation until 100d or CMV reactivation occurred, whichever came first. A historical cohort of 208 UCBT patients also from our transplant center between 2021 and 2022 without LET prophylaxis was compared as control group. The CMV DNA testing was performed using the quantitative real-time PCR (RT-PCR) method and CMV monitoring was examined twice per week for at least 100 days and once a week for at least half a year after UCBT. The 180-day cumulative incidences of CMV reactivation (defined as DNA achieved 500 copies/ml or 1000 copies/ml) and refractory CMV infection (defined as CMV viral load remains the same level or increases after at least 2 weeks of appropriately dosed antiviral therapy) were compared between the two groups. To explore independent predictors of the development of CMV reactivation and resistance, univariate and multivariate analyses were performed by using Fine-Gray proportional hazard regression. Results: The two groups were similar in demographic and transplant characteristics, and in the LET group, patients received LET for a median of 100 days (range, 16-100). The 180-day cumulative incidence of CMV DNA achieved 500 copies/ml and 1000 copies/ml and refractory CMV infection in the LET group were significantly lower than that in the control group [500 copies/ml: 33.8% vs. 78.4%, P &amp;lt; 0.001; 1000 copies/ml: 30.2% vs. 74.0%, P &amp;lt; 0.001; refractory CMV: 4.7% vs. 31.7%, P &amp;lt; 0.001]. Furthermore, multivariate competing risk analysis identified LET prophylaxis as an independent protective factor for CMV reactivation (adjusted hazard ratio [HR] 0.27, 95% CI 0.15 to 0.48, P &amp;lt; 0.001) and refractory CMV infection ([HR] 0.16, 95% CI 0.04 to 0.62, P = 0.004). However no significantly lower incidences of CMV disease (4.7% vs. 8.8%, P = 0.542) and recurrent CMV infection (3.7% vs. 9.6%, P = 0.386) were found in LET group. Among the patients who developed CMV reactivation, there was no significant difference in the time from UCBT to CMV reactivation between two groups (39 days vs. 41 days, P = 0.367). LET prophylaxis was associated with a shorter duration of CMV DNAemia (median 27 days vs. 42 days, P = 0.014), and there was a trend towards lower peak CMV viral load in the LET group (median 2620 copies/ml vs. 5380 copies/ml, P = 0.165). Conclusion: We demonstrated that LET is highly effective at preventing CMV reactivation and resistance after UCBT, and its benefit for UCBT patients perhaps will be observed in a longer-time following time.

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.

S1602 Do We Really Need CMV Prophylaxis in Every Aviremic High Risk CMV-Seropositive Liver Transplant Recipients (D+/R+) in Pakistani Population

S1602 Do We Really Need CMV Prophylaxis in Every Aviremic High Risk CMV-Seropositive Liver Transplant Recipients (D+/R+) in Pakistani Population

Dynamics and Clinical Significance of Cytomegalovirus-Specific Neutralizing Antibodies in Kidney Transplant Recipients Treated with T-Cell-Depleting Agents.

We measured cytomegalovirus (CMV)-specific antibodies that neutralize epithelial cell infection (CMV-AbNEIs) in 101 CMV-seropositive kidney transplant recipients (KTRs) at baseline and posttransplant months 3 and 6. All the patients received antithymocyte globulin and 3-month valganciclovir prophylaxis. There were no significant differences in pretransplant AbNEIs titers between KTRs that developed or did not develop any-level CMV infection or the composite of high-level infection and/or disease. One-year CMV infection-free survival was comparable between KTRs with or without pretransplant CMV-AbNEIs. No differences were observed by months 3 and 6. We observed no protective role for CMV-AbNEIs among CMV-seropositive KTRs undergoing T-cell-depleting induction.

Human herpesvirus-6 reactivation and disease after allogeneic haematopoietic cell transplantation in the era of letermovir for cytomegalovirus prophylaxis

ObjectivesLetermovir for cytomegalovirus (CMV) prophylaxis in allogeneic haematopoietic cell transplant (HCT) recipients has decreased anti-CMV therapy use. Contrary to letermovir, anti-CMV antivirals are also active against human herpesvirus-6 (HHV-6). We assessed changes in HHV-6 epidemiology in the post-letermovir era. MethodsWe conducted a retrospective cohort study of CMV-seropositive allogeneic HCT recipients comparing time periods before and after routine use of prophylactic letermovir. HHV-6 testing was at the discretion of clinicians. We computed the cumulative incidence of broad-spectrum antiviral initiation (foscarnet, (val)ganciclovir, and/or cidofovir), HHV-6 testing, and HHV-6 detection in blood and cerebrospinal fluid within 100 days after HCT. We used Cox proportional-hazards models with stabilized inverse probability of treatment weights to compare outcomes between cohorts balanced for baseline factors. ResultsWe analysed 738 patients, 376 in the pre-letermovir and 362 in the post-letermovir cohort. Broad-spectrum antiviral initiation incidence decreased from 65% (95% CI, 60–70%) pre-letermovir to 21% (95% CI, 17–25%) post-letermovir. The cumulative incidence of HHV-6 testing (17% [95% CI, 13–21%] pre-letermovir versus 13% [95% CI, 10–16%] post-letermovir), detection (3% [95% CI, 1–5%] in both cohorts), and HHV-6 encephalitis (0.5% [95% CI, 0.1–1.8%] pre-letermovir and 0.6% [95% CI, 0.1–1.9%] post-letermovir) were similar between cohorts. First HHV-6 detection occurred at a median of 37 days (interquartile range, 18–58) in the pre-letermovir cohort and 27 (interquartile range, 25–34) in the post-letermovir cohort. In a weighted model, there was no association between the pre-versus post-letermovir cohort and HHV-6 detection (adjusted hazard ratio, 1.08; 95% CI, 0.44–2.62). Discussion: Despite a large decrease in broad-spectrum antivirals after the introduction of letermovir prophylaxis in CMV-seropositive allogeneic HCT recipients, there was no evidence for increased clinically detected HHV-6 reactivation and disease.

In vitro assessment of the combined effect of letermovir and sirolimus on cytomegalovirus replication.

Letermovir (LMV) is used for prophylaxis of cytomegalovirus (CMV) reactivation and end-organ disease in adult CMV-seropositive allogeneic hematopoietic stem cell transplant recipients (allo-HSCT). In turn, sirolimus (SLM) which displays in vitro anti-CMV activity, is frequently employed for prophylaxis of Graft vs. Host disease in allo-HSCT. Here, we aimed at assessing whether LMV and SLM used in combination may act synergistically in vitro on inhibiting CMV replication. The antiviral activity of LMV and SLM alone or in combination was evaluated by a checkerboard assay, using ARPE-19 cells infected with CMV strain BADrUL131-Y. LMV and SLM were used at concentrations ranging from 24 nM to 0.38 nM and 16 nM to 0.06 nM, respectively. The mean EC50 for LMV and SLM was 2.44 nM (95% CI, 1.66-3.60) and 1.40 nM (95% CI, 0.41-4.74), respective. LMV and SLM interaction yielded mainly additive effects over the range of concentrations tested. The additive nature of the combination of LMV and SLM against CMV may have relevant clinical implications in management of CMV infection in allo-HSCT recipients undergoing prophylaxis with LMV.

Cytomegalovirus Immunity Assays Predict Viremia but not Replication Within the Lung Allograft.

We performed CMV immunity assays on 32 lung transplant recipients at risk of CMV disease as defined by serostatus (CMV-seropositive recipients, n = 26; or CMV-seronegative lung transplant recipient receiving a CMV-seropositive donor organ, n = 6). QFN-CMV and T-Track were performed on peripheral blood mononuclear cells, and episodes of CMV replication in both serum and bronchoalveolar lavage were found to be correlated to the CMV immune assays. The predictive ability of the assays was determined using Kaplan-Meier curves. There was a degree of concordance between tests, with 44% of recipients positive for both tests and 28% negative for both tests; however, test results were discordant in 28% of cases. A negative result in either the QFN-CMV (P < 0.01) or T-Track (P < 0.05) assays was obtained in a significantly higher number of recipients who experienced CMV replication in the blood. Using these assays together gave higher predictability of CMV replication, with only 1 recipient experiencing CMV replication in the blood who obtained a positive test result for both assays. Neither assay was able to predict recipients who experienced CMV replication in the lung allograft. Our study demonstrates that CMV immunity assays can predict viremia; however, the lack of association with allograft infection suggests that CMV-specific T-cell immunity in the circulation is not associated with the control of CMV replication within the transplanted lung allograft.

(222) Discordance Between Humoral and Cellular Immune Responses to Cytomegalovirus Infection in CMV Seropositive Recipients (R+)

(222) Discordance Between Humoral and Cellular Immune Responses to Cytomegalovirus Infection in CMV Seropositive Recipients (R+)

Improved outcomes over time and higher mortality in CMV seropositive allogeneic stem cell transplantation patients with COVID-19; An infectious disease working party study from the European Society for Blood and Marrow Transplantation registry.

COVID-19 has been associated with high morbidity and mortality in allogeneic hematopoietic stem cell transplant (allo-HCT) recipients. This study reports on 986 patients reported to the EBMT registry during the first 29 months of the pandemic. The median age was 50.3 years (min - max; 1.0 - 80.7). The median time from most recent HCT to diagnosis of COVID-19 was 20 months (min - max; 0.0 - 383.9). The median time was 19.3 (0.0 - 287.6) months during 2020, 21.2 (0.1 - 324.5) months during 2021, and 19.7 (0.1 - 383.9) months during 2022 (p = NS). 145/986 (14.7%) patients died; 124 (12.6%) due to COVID-19 and 21 of other causes. Only 2/204 (1%) fully vaccinated patients died from COVID-19. There was a successive improvement in overall survival over time. In multivariate analysis, increasing age (p<.0001), worse performance status (p<.0001), contracting COVID-19 within the first 30 days (p<.0001) or 30 - 100 days after HCT (p=.003), ongoing immunosuppression (p=.004), pre-existing lung disease (p=.003), and recipient CMV seropositivity (p=.004) had negative impact on overall survival while patients contracting COVID-19 in 2020 (p<.0001) or 2021 (p=.027) had worse overall survival than patients with COVID-19 diagnosed in 2022. Although the outcome of COVID-19 has improved, patients having risk factors were still at risk for severe COVID-19 including death.

Features of cytomegalovirus DNAemia and virus-specific T-cell responses in allogeneic hematopoietic stem-cell transplant recipients during prophylaxis with letermovir.

There is scarce information on the natural kinetics of cytomegalovirus (CMV) DNAemia and dynamics of CMV-specific T-cell reconstitution in allogeneic hematopoietic transplant recipients (allo-HSCT) undergoing letermovir (LMV) prophylaxis. Twelve adult CMV-seropositive high-risk recipients (median age, 53 years; 9 males/3 females) undergoing LMV prophylaxis and 13 non-LMV allo-HSCT controls (median age, 58 years; 7 males/6 females) were included. CMV DNAemia in plasma was monitored by real-time polymerase chain reaction. Preemptive antiviral therapy (PET) was administered upon detection of ≥1500IU/ml. CMV-specific interferon-gamma (IFN-γ)-producing CD8+ and CD4+ T cells were enumerated by flow cytometry around days +30, +60, and +90 after allo-HSCT. Ex vivo experiments assessing of the potential effect of LMV on CMV-specific T-cell expansion in a single CMV-seropositive donor were also conducted. Five LMV patients (41.6%) developed CMV DNAemia that cleared spontaneously. Four patients (33.3%) developed CMV DNAemia after LMV cessation, of which two required PET. Nine non-LMV patients (69.2%) developed CMV DNAemia (five required PET). The percentage of LMV and non-LMV patients exhibiting detectable CMV-specific T-cell responses was comparable (7/10 vs. 10/13; p=.71). Nevertheless, median CMV-specific CD4+ and CD8+ T-cell counts were lower in LMV patients by days +60 (p=.006 and .02, respectively) and +90 (p=.08 and .02). Ex vivo, CMV-specific CD8+ T cells expanded to the same level either in the presence (19.8%) or in the absence of LMV (20.6%). In our series, episodes of CMV DNAemia in LMV patients cleared spontaneously. A diminished degree of CMV-specific T-cell reconstitution in LMV patients compared to non-LMV patients was observed.

Cytomegalovirus breakthrough and resistance during letermovir prophylaxis.

Letermovir is a relatively new antiviral for prophylaxis against cytomegalovirus (CMV) after allogeneic hematopoietic cell transplantation (HCT). CMV-seropositive HCT recipients who received letermovir prophylaxis from 2018 to 2020 at our center were evaluated for letermovir resistance and breakthrough CMV reactivation. Two-hundred twenty-six letermovir recipients were identified and 7/15 (47%) with CMV DNAemia ≥200 IU/mL were successfully genotyped for UL56 resistance. A single C325Y resistance mutation was identified in an umbilical cord blood recipient. Ninety-five (42%), 43 (19%), and 15 (7%) patients had breakthrough CMV at any level, ≥150 IU/mL, and ≥500 IU/mL, respectively. Risk factors for breakthrough CMV reactivation at each viral threshold were examined. Cumulative steroid exposure was the strongest risk factor for CMV at all evaluated viral thresholds. Graft-versus-host disease prophylaxis with post-transplantation cyclophosphamide (aHR 2.34, 95% CI 1.28-4.28, p = 0.001) or calcineurin inhibitors plus mycophenolate (aHR 2.24, 95% CI 1.30-3.86, p = 0.004) were also associated with an increased risk of CMV reactivation at any level. De novo letermovir resistance is rare and can be successfully treated using other antivirals. Letermovir effectively prevents clinically significant CMV, however, subclinical CMV reactivation occurs frequently at our center.