Rapid detection directly from patient serum samples of human cytomegalovirus UL97 mutations conferring ganciclovir resistance

Next-generation sequencing for cytomegalovirus antiviral resistance genotyping in a clinical virology laboratory

INTRODUCTION

The identification of CMV antiviral drug resistance (AVDR) is a critical diagnostic test for immunocompromised patients with CMV infection and a failure of virologic response on optimal antiviral treatment. We developed a next-generation sequencing (NGS) assay for CMV AVDR testing and compared the AVDR mutations identified by NGS to Sanger sequencing.

METHODS

Retrospective review of CMV AVDR testing requests for UL97 and UL54 at our laboratory from 2014 to 2019 was conducted. NGS was performed on the MinION and compared to Sanger sequencing performed at the national reference laboratory. Analysis of the sequences was completed with a novel cloud bioinformatics platform (BugSeq).

RESULTS

Twenty patient samples previously characterized were included for study on the MinION. NGS captured all of the CMV AVDR mutations identified by Sanger, and identified additional mutations in UL97 and/or UL54 in 8/13 (62%) of the samples. An analysis of the depth of coverage at which we no longer detected minority single nucleotide variants (SNVs) detected in the original data was conducted, estimating a recall of 95% at 1800 fold coverage.

CONCLUSION

NGS utilizing MinION technology for the detection of CMV AVDR mutations identified additional minority variants in UL97 and UL54 as compared with Sanger sequencing. Through the application of a bioinformatics pipeline available online, our NGS process eliminates barriers associated with the use of the MinION and NGS in clinical laboratories.

Study of cytomegalovirus resistance in allogeneic hematopoietic cell transplant recipients

INTRODUCTION

Cytomegalovirus (CMV) is the most important opportunistic pathogen associated with transplant. The objective of this study was the characterization of CMV resistance mutations in allogeneic haematopoietic cell transplant recipients (allo-TPH) and the study of associated factors.

METHODS

A retrospective study of a cohort of allo-TPH recipients with post-transplant CMV reactivations with stable or increasing viral loads (CV), despite adequate antiviral treatment for at least 2weeks. The study of resistance mutations of the UL97 and UL54 genes was carried out by Sanger sequencing.

RESULTS

Refractory CMV infection in our group of allo-TPH patients corresponded with a 21.43% rate of resistant virus infection (3 of 14 patients). All patients with resistance mutations had multiple reactivation episodes (P-value .01). The mutations found were A594V and H520Q in the UL97 gene that confers high-grade resistance to ganciclovir (GCV). One of the 3 cases with antiviral resistance was documented with a low VL (< 1000 copies/ml) and short accumulated GCV treatment (41 days).

CONCLUSION

Most of the failures in the treatment of CMV were possibly due to clinical resistance; the lack of satisfactory response to antiviral treatment is not always accompanied by virological resistance. However, the appearance of resistances can occur early after the start of the treatment and with VL below 1000 copies / ml. The number of episodes of reactivation was higher among patients with virological resistance than those who did not.

Global estimate of phenotypic and genotypic ganciclovir resistance in cytomegalovirus infections among HIV and organ transplant patients; A systematic review and meta-analysis

Human cytomegalovirus (CMV), an opportunistic pathogen belonging to Herpesviridae family, is considered as one of the major causes of morbidity and mortality among wide variety of patients, particularly in transplant recipients and HIV positive patients. As this virus can be resistant to treatment, frequency of CMV in patients who receive organ transplantation and people suffering from AIDS was studied between 1980 and 2019. Medline (via PubMed), Embase, Web of Science, and the Iranian Database were reviewed, and Comprehensive Meta-Analysis (V2.0, Biostat) software analyzed all data. Finally, we used Cochran's Q-statistic to encounter heterogeneity between different studies. Meta-analyses indicated, GCV resistance was 14.1% (95% CI 11.2-17.7); however, in patients suffering from AIDS and organ transplantation were 19.5% (95% CI 14.7-25.4) and 11.4% (95% CI 8.1-15.8), respectively. There were increasing rates in the prevalence of GCV resistance in CMV among transplant recipients, and HIV positive patients. Therefore, evaluation of these refractory infections is beneficial.

Risk Factors and Outcomes of Ganciclovir-Resistant Cytomegalovirus Infection in Solid Organ Transplant Recipients

Background

Ganciclovir-resistant (ganR) cytomegalovirus (CMV) is an emerging and important problem in solid organ transplant (SOT) recipients. Only through direct comparison of ganR- and ganciclovir-sensitive (ganS) CMV infection can risk factors and outcomes attributable specifically to ganciclovir resistance appropriately be determined.

Methods

We performed a retrospective, case-control (1:3) study of SOT recipients with genotypically confirmed ganR-CMV (n = 37) and ganS-CMV infection (n = 109), matched by donor/recipient CMV serostatus, year and organ transplanted, and clinical manifestation. We used χ2 (categorical) and Mann-Whitney (continuous) tests to determine predisposing factors and morbidity attributable to resistance, and Kaplan-Meier plots to analyze survival differences.

Results

The rate of ganR-CMV was 1% (37/3467) overall and 4.1% (32/777) among CMV donor-positive, recipient-negative patients, and was stable over the study period. GanR-CMV was associated with increased prior exposure to ganciclovir (median, 153 vs 91 days, P < .001). Eighteen percent (3/17) of lung transplant recipients with ganR-CMV had received <6 weeks of prior ganciclovir (current guideline-recommended resistance testing threshold), and all non-lung recipients had received ≥90 days (median, 160 [range, 90-284 days]) prior to diagnosis of ganR-CMV. GanR-CMV was associated with higher mortality (11% vs 1%, P = .004), fewer days alive and nonhospitalized (73 vs 81, P = .039), and decreased renal function (42% vs 19%, P = .008) by 3 months after diagnosis.

Conclusions

GanR-CMV is associated with longer prior antiviral duration and higher attributable morbidity and mortality than ganS-CMV. Upcoming revised CMV guidelines should incorporate organ transplant-specific thresholds of prior drug exposure to guide rational ganR-CMV testing in SOT recipients. Improved strategies for prevention and treatment of ganR-CMV are warranted.

How I treat resistant cytomegalovirus infection in hematopoietic cell transplantation recipients

Cytomegalovirus (CMV) infection is a significant complication in hematopoietic cell transplantation (HCT) recipients. Four antiviral drugs are used for preventing or treating CMV: ganciclovir, valganciclovir, foscarnet, and cidofovir. With prolonged and repeated use of these drugs, CMV can become resistant to standard therapy, resulting in increased morbidity and mortality, especially in HCT recipients. Antiviral drug resistance should be suspected when CMV viremia (DNAemia or antigenemia) fails to improve or continue to increase after 2 weeks of appropriately dosed and delivered antiviral therapy. CMV resistance is diagnosed by detecting specific genetic mutations. UL97 mutations confer resistance to ganciclovir and valganciclovir, and a UL54 mutation confers multidrug resistance. Risk factors for resistance include prolonged or previous anti-CMV drug exposure or inadequate dosing, absorption, or bioavailability. Host risk factors include type of HCT and degree of immunosuppression. Depending on the genotyping results, multiple strategies can be adopted to treat resistant CMV infections, albeit no randomized clinical trials exist so far, after reducing immunosuppression (if possible): ganciclovir dose escalation, ganciclovir and foscarnet combination, and adjunct therapy such as CMV-specific cytotoxic T-lymphocyte infusions. Novel therapies such as maribavir, brincidofovir, and letermovir should be further studied for treatment of resistant CMV.

Characterising variation in five genetic loci of cytomegalovirus during treatment for congenital infection

Cytomegalovirus (CMV) is the most common congenital infection in humans and a leading cause of sensorineural hearing loss. Ganciclovir (6 mg/kg twice daily for 42 days) has been shown to reduce hearing deterioration and is used in clinical practice. Vaccines and passive administration of antibody are being evaluated in randomized controlled trials in allograft candidates, women of childbearing age, and pregnant women with primary CMV infection. To help define genetic variation in each of the targets of these therapeutic interventions, we amplified and sequenced genes UL97 (site utilised for ganciclovir phosphorylation), UL55 (glycoprotein B (gB) vaccine target) and UL128, UL130, and UL131a (specific monoclonal antibody targets). Serial blood, saliva, and urine samples (total 120) obtained from nine infants with symptomatic congenital CMV treated with 42 days' ganciclovir were analyzed. All samples tested were UL97 wild type at baseline and none developed mutations during treatment, showing no selection of resistance. The prevalences of UL55 genotypes were 28% gB1, 22% gB2, 1% gB3, and mixed in 20% samples. No mutations were noted in UL128-131a. Phylogenetic tree analysis showed that sequences with variations were found in multiple body sites of individual patients, so there was no evidence of body site compartmentalization of particular strains of CMV. The significance of these results for changes in diagnostic practices and therapeutic interventions against CMV are discussed. J. Med. Virol. 89:502-507, 2017. © 2016 Wiley Periodicals, Inc.

Valganciclovir for the prevention of complications of late cytomegalovirus infection after allogeneic hematopoietic cell transplantation: a randomized trial

BACKGROUND

Optimal prevention of late cytomegalovirus (CMV) disease is poorly defined.

OBJECTIVE

To compare valganciclovir prophylaxis with polymerase chain reaction-guided preemptive therapy.

DESIGN

Randomized, double-blind trial. (ClinicalTrials.gov: NCT00016068).

SETTING

Multicenter trial.

PATIENTS

184 recipients of hematopoietic cell transplantation (HCT) who were at high risk for late CMV disease (95 patients received valganciclovir and 89 received placebo).

INTERVENTION

6 months of valganciclovir (900 mg/d) or placebo. Patients with polymerase chain reaction positivity at 1000 copies/mL or greater or a 5-fold increase over baseline were treated with ganciclovir or valganciclovir (5 mg/kg or 900 mg twice daily, respectively).

MEASUREMENTS

The composite primary end point was death, CMV disease, or other invasive infections by 270 days after HCT. Secondary end points were CMV disease, CMV DNAemia, death, other infections, resource utilization, ganciclovir resistance, quality of life, immune reconstitution, and safety.

RESULTS

The primary composite outcome occurred in 20% of valganciclovir recipients versus 21% of placebo-preemptive therapy recipients (treatment difference, -0.01 [95% CI, -0.13 to 0.10]; P = 0.86). There was no difference in the primary end point or its components 640 days after HCT. The incidence of a CMV DNAemia level of 1000 copies/mL or greater or a 5-fold increase over baseline was reduced in the valganciclovir group (11% vs. 36%; P < 0.001). Neutropenia was not significantly different at the absolute neutrophil count of less than 0.5 × 109 cells/L (P = 0.57); however, more patients received hematopoietic growth factors in the valganciclovir group (25.3% vs. 12.4%; P = 0.026). No significant differences were seen in other secondary outcomes.

LIMITATION

Some high-risk patients were not included.

CONCLUSION

Valganciclovir prophylaxis was not superior in reducing the composite end point of CMV disease, invasive bacterial or fungal disease, or death when compared with polymerase chain reaction-guided preemptive therapy. Both strategies performed similarly with regard to most clinical outcomes.

PRIMARY FUNDING SOURCE

Roche Laboratories.

Rapid detection of human cytomegalovirus UL97 and UL54 mutations directly from patient samples

Human cytomegalovirus (CMV) is a significant contributor to morbidity and mortality in immunocompromised patients, particularly in the transplant setting. The availability of anti-CMV drugs has improved treatment, but drug resistance is an emerging problem. Here, we describe an improved, rapid, sequencing-based assay for the two genes in CMV where drug resistance occurs, the UL97 and UL54 genes. This assay is performed in 96-well format with a single master mix and provides clinical results within 2 days. It sequences codons 440 to 645 in the UL97 gene and codons 255 to 1028 in the UL54 gene with a limit of detection of 240 IU/ml. With this assay, we tested 43 specimens that had previously been tested for UL97 drug resistance and identified 3 with UL54 mutations. One of these patients had no concurrent UL97 mutation, pointing toward the need for an assay that facilitates dual UL97/UL54 gene testing for complete resistance profiling.

Rapid detection and quantitation of ganciclovir resistance in cytomegalovirus quasispecies

Human cytomegalovirus (HCMV) may cause severe or fatal disease among immunocompromised patients. The first line prophylaxis and systemic HCMV disease therapy is ganciclovir (GCV). The presence of GCV-resistant virus has been linked to fatal HCMV disease. The implementation of rapid and sensitive techniques for the early detection and monitoring of GCV-resistance may be helpful to support antiviral therapy management. A pyrosequencing assay for the detection and quantitation of the most frequent mutations conferring moderate- and high-grade GCV resistance was implemented. The pyrosequencing achieved an analytical sensitivity for adequate interpretation of ≥10(3)  copies/ml. The assay was validated with 18 whole blood samples taken over a 6-month period from an umbilical cord blood recipient infected persistently with HCMV and allowed the detection and monitoring of the M460I and A594V GCV-resistant mutations. The percentage of resistant quasispecies ranged from 7.9% to 55.2% for the M460I mutation and from 19.8% to 43% for the A594V mutation. Clearance of the M460I mutation occurred in parallel with a decrease in the HCMV viremia, while the A594V mutation persisted. The pyrosequencing method for detection of GCV is sensitive enough to be used directly on clinical samples for the early identification of resistance mutations and allows the quantitation of resistant and wild type virus quasispecies within hours. The quantitation of minor resistant variants is an important issue to understand their relationship with viral load modification, and potentially anticipate treatment adjustment.

Successful ganciclovir treatment of primary cytomegalovirus infection containing the UL97 mutation N510S in an intestinal graft recipient

In solid organ transplantation, human cytomegalovirus (HCMV) is considered to be the most important viral pathogen. We report a case of a CMV R-/D+ small intestine transplant recipient with a primary CMV infection on valganciclovir prophylaxis. Sequencing of the HCMV DNA for drug resistance-associated mutations revealed the UL97 mutation N510S. This mutation has been initially reported to confer ganciclovir resistance. Based on in vitro recombinant phenotyping, this assumption has recently been questioned. Switching the antiviral treatment to an intravenous regimen of ganciclovir eliminated HCMV DNAemia, showing the in vivo efficacy of ganciclovir for the UL97 mutation N510S. Hence, knowledge of drug efficacy is crucial for an adequate choice of antiviral medication, carefully balancing antiviral potency versus the risk of harmful side effects.

The time course of development and impact from viral resistance against ganciclovir in cytomegalovirus infection

(Val)ganciclovir is used to treat cytomegalovirus (CMV) infection following solid organ (SOT) or hematopoietic stem cell (HSCT) transplantation. Treatment failures occur, but the contribution from 39 known ganciclovir-related mutations (GRMs) in the CMV-UL97 gene remains controversial. We propose a categorization of these GRMs potentially useful when interpreting sequence analyses in clinical settings. The UL97 gene was sequenced from first/recurrent CMV infections among consecutive SOT or HSCT recipients during 2004-2009. GRMs were categorized as: Signature GRM (sGRM) if in vitro ganciclovir IC(50) ratio for mutated versus wild-type virus >2 (n = 24); polymorphic GRM (pGRM) if ratio <2 (n = 15). (Val)ganciclovir treatment failure was defined as persistent viremia for 30 days or switch to foscarnet within this period. Of 99 (49 HSCT and 50 SOT) recipients with one CMV infection episode, 15 (13 HSCT and 2 SOT) experienced a total of 19 recurrent infection episodes. The prevalence of sGRM was 0% at start of first episode, whereas at start of recurrent episodes, prevalence was 37%. Only one sGRM was present at a time in individual patients. Patients with CMV containing an sGRM (vs. wild type)-but not with a pGRM-were at excess risk of treatment failure (odds ratio = 70.6 [95% CI:8.2-609.6]; p < 0.001). sGRMs emerged only following longer termed use of antiherpetic drugs and usually in recurrent CMV infection episodes. Risk of ganciclovir treatment failure was raised if an sGRM was detected.

Sensitive and rapid detection of ganciclovir resistance by PCR based MALDI-TOF analysis

BACKGROUND

Cytomegalovirus (CMV) infection is associated with significant morbidity and mortality in transplant recipients. Resistance against ganciclovir is increasingly observed. According to current guidelines, direct drug resistance testing is not always performed due to high costs and work effort, even when resistance is suspected.

OBJECTIVES

To develop a more sensitive, easy applicable and cost-effective assay as proof of concept for direct drug resistance testing in CMV surveillance of post-transplant patients.

STUDY DESIGN

Five consecutive plasma samples from a heart transplant patient with a primary CMV infection were analyzed by quantitative real-time polymerase chain reaction (rtPCR) as a surrogate marker for therapy failure, and by direct drug resistance detection assays such as Sanger sequencing and the novel primer extension (PEX) reaction matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) based method.

RESULTS

This report demonstrates that PEX reaction followed by MALDI-TOF analysis detects the A594V mutation, encoding ganciclovir resistance, ten days earlier compared to Sanger sequencing and more than 30 days prior to an increase in viral load.

CONCLUSION

The greatly increased sensitivity and rapid turnaround-time combined with easy handling and moderate costs indicate that this procedure could make a major contribution to improve transplantation outcomes.

Human cytomegalovirus UL97 D605E polymorphism has a high prevalence in immunocompetent Japanese infants and children

There is no existing data on UL97 mutation in human cytomegalovirus (HCMV) isolates obtained from individuals who have never been exposed to ganciclovir (GCV). UL97 codons 439 to 645 from 61 CMV isolates from 61 immunocompetent Japanese infants and children were sequenced directly. No known GCV resistance mutations were found, meaning that the UL97 mutation had resulted from the use of GCV. On the other hand, a mutation at codon 605 (D to E) was frequently identified (56/61: 91.8%). This could be a genetic marker for HCMV in East Asian counties, because of its low prevalence in the strains of HCMV circulating in Western countries.

Primary response against cytomegalovirus during antiviral prophylaxis with valganciclovir, in solid organ transplant recipients

Antiviral prophylaxis has proved successful for prevention of cytomegalovirus (CMV) disease in solid organ transplant (SOT) patients; though emerging data suggest that antiviral agents interfere with immunity, and may inhibit immune priming. In this context, we investigated levels and phenotype of primary CMV-specific immune responses that developed during antiviral prophylaxis in a cohort of CMV seronegative recipients (R(-) ) of a SOT from a seropositive donor (D(+) ). We longitudinally monitored CMV viral load, antibodies and levels of the negative immuno-modulator IL-10. PBMC were stimulated with CMV-specific peptide libraries to measure CD137 activation marker on CMV-specific T-cells and levels of PD-1 receptor, which is over expressed on exhausted T-cells. Unexpectedly, the majority (13/18) of D(+) R(-) patients who developed a primary CMV response showed early post-transplant CMV-specific responses, though levels of PD-1 on CMV-specific T-cells remained elevated throughout prophylaxis. A strong inverse association was found between levels of plasma IL-10 and CMV-specific cellular immune responses. Our study suggests that during prophylaxis, subclinical CMV infection might have occurred in the D(+) R(-) patients, and primary CMV-specific responses were detected early post-transplant when levels of plasma IL-10 were low. Extended prophylaxis or antiviral treatment did not appear to suppress CMV-specific antibodies or T-cells, which, however, showed exhaustion phenotypes.

Molecular analysis of varicella vaccines and varicella-zoster virus from vaccine-related skin lesions

To prevent complications that might follow an infection with varicella-zoster virus (VZV), the live attenuated Oka strain (V-Oka) is administered to children in many developed countries. Three vaccine brands (Varivax from Sanofi Pasteur MSD; Varilrix and Priorix-Tetra, both from Glaxo-Smith-Kline) are licensed in Germany and have been associated with both different degrees of vaccine effectiveness and adverse effects. To identify genetic variants in the vaccines that might contribute to rash-associated syndromes, single nucleotide polymorphism (SNP) profiles of variants from the three vaccines and rash-associated vaccine-type VZV from German vaccinees were quantitatively compared by PCR-based pyrosequencing (PSQ). The Varivax vaccine contained an estimated 3-fold higher diversity of VZV variants, with 20% more wild-type (wt) SNPs than Varilrix and Priorix-Tetra. These minor VZV variants in the vaccines were identified by analyzing cloned full-length open reading frame (ORF) orf62 sequences by chain termination sequencing and PSQ. Some of these sequences amplified from vaccine VZV were very similar or identical to those of the rash-associated vaccine-type VZV from vaccinees and were almost exclusively detected in Varivax. Therefore, minorities of rash-associated VZV variants are present in varicella vaccine formulations, and it can be concluded that the analysis of a core set of four SNPs is required as a minimum for a firm diagnostic differentiation of vaccine-type VZV from wt VZV.

Functional characterization of novel mutations in UL54 of ganciclovir resistant HCMV strain using structural analysis

This study reports the probable impact of the coupled mutations observed in our clinical isolate of HCMV UL54 polymerase, through structural bioinformatics approaches. The reported variant was found to be resistant to Ganciclovir (GCV) as per the clinical records. The presence of Glutamine deletion at 639 (Glu639) and a mis sense mutation of Serine 655 Leucine (Ser655Leu) in UL54 were identified by DNA sequencing and were predicted to lie in the DNA polymerase type-II domain. Docking simulation studies of the phosphorylated forms of Ganciclovir (GCV), Cidofovir (CDV) and Foscarnet (PFA) with the reported mutants showed significant variation in terms of binding affinity and inhibitory constant (Ki) in comparison to wild type UL54. The findings of this study revealed that the observed coupled mutation could potentially induce allosteric effects in the binding pockets of UL54 and thereby alter the drug binding affinity. In specific, it was observed that this coupled mutation could confer changes in the binding affinity of GCV and PFA by altering the binding energies and inhibitory constants to -0.88Kcal/mol and 226.71mM, -5.81Kcal/mol and 54.83µM, respectively, in comparison to Wild Type. On the other hand, CDV showed increased susceptibility for the reported mutant with a binding energy of -6.16Kcal/mol and inhibitory constant of 30.47µM.

Improved detection of mutated human cytomegalovirus UL97 by pyrosequencing

Ganciclovir (GCV) resistance frequently occurs upon prolonged treatment of ongoing active human cytomegalovirus (HCMV) infection in individuals with immature or compromised immune functions (e.g., recipients of solid-organ and hematopoietic stem cell transplants). Using pyrosequencing (PSQ), we established fast and sensitive detection of GCV resistance-associated mutations occurring in the HCMV open reading frame UL97. These mutations have been repeatedly associated with clinical treatment failure. We designed four PSQ assays and evaluated them by analyzing mixtures of plasmids or bacterial artificial chromosome-derived viruses containing UL97 wild-type and mutant sequences. A minimum level of 6% mutant sequence variants could be detected in these mixtures. In order to further evaluate the novel PSQ assays, we tested clinical specimens from patients with active HCMV infections. The results were compared with those obtained by conventional dideoxy chain terminator sequencing. As the PSQ method was more sensitive in detecting minor HCMV mutant fractions in a wild-type population, it is suggested that pyrosequencing is a useful tool for the early detection of emerging GCV-resistant HCMV in GCV-treated patients.

Recombinant phenotyping of cytomegalovirus UL97 kinase sequence variants for ganciclovir resistance

A strain of human cytomegalovirus, T2211, modified from standard laboratory strain AD169 to contain a secreted alkaline phosphatase reporter gene for rapid viral quantitation, was cloned as a bacterial artificial chromosome, BA1, and then mutagenized to create recombinant viruses containing viral UL97 kinase sequence variants found in clinical specimens after ganciclovir treatment, but with no phenotypic data to determine their role in drug resistance. Seven control strains and 14 other recombinant strains were phenotyped for ganciclovir resistance and compared with similar strains created using prior technology to show a good concordance of findings. Sequence changes V466M, H469Y, A478V, N510S, A588V, K599R, L600I, G623S, T659I, and V665I were found to confer no significant ganciclovir resistance, while mutations L405P, M460T, A594E, and C603R conferred 3- to 9-fold increases in ganciclovir 50% inhibitory concentrations. Different mutations at codons 594 (A594V, A594E) and 603 (C603W, C603S) conferred varied amounts of ganciclovir resistance. Advances in recombinant phenotyping make it easier to show that many uncharacterized UL97 sequence variants do not confer ganciclovir resistance, but some are newly confirmed as resistance associated, including one (L405P) which is outside the codon range where such mutations are usually found. This information should improve the interpretation of genotypic data generated by diagnostic laboratories.

Variable viral clearance despite adequate ganciclovir plasma levels during valganciclovir treatment for cytomegalovirus disease in D+/R- transplant recipients

BACKGROUND

Valganciclovir, the oral prodrug of ganciclovir, has been demonstrated equivalent to iv ganciclovir for CMV disease treatment in solid organ transplant recipients. Variability in ganciclovir exposure achieved with valganciclovir could be implicated as a contributing factor for explaining variations in the therapeutic response. This prospective observational study aimed to correlate clinical and cytomegalovirus (CMV) viral load response (DNAemia) with ganciclovir plasma concentrations in patients treated with valganciclovir for CMV infection/disease.

METHODS

Seven CMV D+/R- transplant recipients (4 kidney, 2 liver and 1 heart) were treated with valganciclovir (initial dose was 900-1800 mg/day for 3-6.5 weeks, followed by 450-900 mg/day for 2-9 weeks). DNAemia was monitored by real time quantitative PCR and ganciclovir plasma concentration was measured at trough (Ctrough) and 3 h after drug administration (C3h) by HPLC.

RESULTS

Four patients presented with CMV syndrome, two had CMV tissue-invasive disease after prophylaxis discontinuation, and one liver recipient was treated pre-emptively for asymptomatic rising CMV viral load 5 weeks post-transplantation in the absence of prophylaxis. CMV DNAemia decreased during the first week of treatment in all recipients except in one patient (median decrease: -1.2 log copies/mL, range: -1.8 to 0) despite satisfactory ganciclovir exposure (AUC0-12 = 48 mgxh/L, range for the 7 patients: 40-118 mgxh/L). Viral clearance was obtained in five patients after a median of time of 34 days (range: 28-82 days). Two patients had recurrent CMV disease despite adequate ganciclovir exposure (65 mgxh/L, range: 44-118 mgxh/L).

CONCLUSIONS

Valganciclovir treatment for CMV infection/disease in D+/R- transplant recipients can thus result in variable viral clearance despite adequate ganciclovir plasma concentrations, probably correlating inversely with anti-CMV immune responses after primary infection.

Valganciclovir as pre-emptive therapy for cytomegalovirus infection post-allogenic stem cell transplantation: implications for the emergence of drug-resistant cytomegalovirus

OBJECTIVES

Valganciclovir is a well established drug for the management of cytomegalovirus (CMV) infection in haematopoietic stem cell transplantation (HSCT). Data concerning its safety regarding the development of drug resistance are required. The aim of the present study was to retrospectively investigate CMV drug resistance in a group of HSCT patients experiencing relapses of CMV infection after a first-line pre-emptive antiviral therapy.

METHODS

Thirteen adult HSCT patients out of 26 with asymptomatic CMV infection, experiencing relapsing infections 45-155 days after either intravenous (iv) ganciclovir (2 patients) or valganciclovir (11 patients), were studied. Genotypic assays for mutations in the viral phosphotransferase (UL97) and DNA-polymerase (UL54) genes were directly applied on patient specimens. Baseline CMV sequences were compared with those at the time of relapses to identify drug-resistant strains.

RESULTS

UL97 mutations A594V and M460V known to confer drug resistance developed in one relapsing patient who received iv ganciclovir as first-line therapy, corresponding to a rate of 7.7% of relapses due to drug-resistant strains and an overall 3.8% rate of infections due to CMV drug-resistant strains. UL54 drug resistance mutations were absent. No evidence of drug resistance was found in patients on valganciclovir either as first-line therapy or as treatment for relapses.

CONCLUSIONS

The safety profile of valganciclovir as anti-CMV pre-emptive therapy was confirmed, as well as that monitoring CMV drug resistance with genotypic tests on sequential isolates over the time-course of therapy offers guidance to tailor antiviral treatment in a clinically relevant time frame.

Cytomegalovirus UL97 mutations in the era of ganciclovir and maribavir

Mutations in the human CMV UL97 kinase gene are a major mechanism of viral resistance to two anti-CMV drugs, ganciclovir (GCV) and maribavir (MBV). GCV, the most widely used and established therapy for CMV, is a substrate for the UL97 kinase. Well-characterised GCV-resistance mutations at UL97 codons 460, 520 and 590-607 impair the phosphorylation of GCV that is necessary for its antiviral activity, presumably by altering substrate recognition. In contrast, MBV is an inhibitor of the UL97 kinase and is the first new CMV therapy to reach later stage clinical trials in many years. No MBV-resistant CMV isolates have yet been detected in clinical trials, but after culture propagation under drug, UL97 mutations that confer moderate to high-level MBV resistance have been identified at codons 353, 397, 409 and 411. These mutations are located upstream of the GCV-resistance mutations and are close to the ATP-binding and catalytic domains common to all kinases, consistent with MBV acting as a small molecule ATP-competitive kinase inhibitor. So far, no UL97 mutations are known to confer resistance to both GCV and MBV.