Ganciclovir Resistance Mutations Research Articles

Ganciclovir Resistance-Linked Mutations in the HCMV UL97 Gene: Sanger Sequencing Analysis in Samples from Transplant Recipients at a Tertiary Hospital in Southern Brazil.

Background/Objectives: Human cytomegalovirus (HCMV) DNAemia remains a significant concern for transplant recipients, largely due to mutations in the viral genome that may lead to antiviral-resistant strains. Mutations in the UL97 gene are frequently associated with resistance to ganciclovir (GCV), highlighting the importance of early mutation detection to effectively manage viremia. This study aimed to optimize a Sanger sequencing protocol for analyzing GCV resistance-linked mutations in the HCMV UL97 gene from plasma samples of transplant patients treated at Hospital de Clínicas de Porto Alegre, Rio Grande do Sul, Brazil. Methods: A nested-PCR approach combined with a touchdown PCR method was employed to enhance the sensitivity and specificity of the sequencing analysis. Results: The study sample included various transplants, encompassing solid organ and bone marrow recipients. Among 16 sequenced samples, 8 exhibited nucleotide substitutions resulting in amino acid changes. Notably, the A594V and C603W mutations, associated with GCV resistance, were identified in four samples. Additionally, three mutations with unknown phenotypic impact (P509L, A628T, and H662Y) and two viral polymorphisms (N510S and D605E) were detected. Furthermore, double peaks in the Sanger electropherograms, indicative of mixed viral populations of HCMV were observed in seven samples. Conclusions: The optimized Sanger sequencing protocol provides a cost-effective solution for detecting GCV resistance mutations in HCMV UL97 among transplant recipients. This approach could improve the understanding of HCMV strain dynamics and serve as a valuable tool for long-term patient monitoring, particularly within resource-constrained settings such as the public health systems of middle-income countries.

Comparative Emergence of Maribavir and Ganciclovir Resistance in a Randomized Phase 3 Clinical Trial for Treatment of Cytomegalovirus Infection.

Among 547 patients receiving maribavir or valganciclovir for first-episode cytomegalovirus infection after hematopoietic cell transplant, the treatment response rate was 69.6% and 77.4% respectively. Development of maribavir and ganciclovir resistance was compared after receiving either drug. Viral mutations conferring drug resistance were analyzed in plasma DNA extracts at baseline and post-treatment. Prior antiviral drug exposure was limited, with only 2 instances of baseline drug resistance detected. An equal number (n=241) received valganciclovir or maribavir for at least 21 days (median 55-56 days). Among them, drug resistance mutations were detected in 24 (10%) maribavir recipients at 35-125 days (median 56) after starting therapy, including in 12 of 14 who experienced a viral load rebound while on therapy. Ganciclovir resistance mutations developed in 6 (2.5%) valganciclovir recipients at 66-110 days (median 90). One maribavir recipient developed a novel UL97 gene mutation (P-loop substitution G343A) that conferred strong maribavir and ganciclovir resistance in vitro. Viral clearance was confirmed in 17 (74%) of 23 patients with emergent maribavir resistance after re-treatment with an alternative CMV antiviral drug. After 3-8 weeks of therapy, maribavir resistance emerged earlier and more frequently than ganciclovir resistance but was usually treatable using alternative therapy. NCT02927067 (AURORA).

The Case | Crescentic glomerulonephritis in a kidney transplant recipient

A 55-year-old man was referred for acute kidney failure. He had undergone a kidney transplantation for focal segmental glomerulosclerosis 6 months before admission. Medical history consisted of hypertension, hypercholesterolemia, monoclonal gammopathy of unknown significance (IgM λ), and tertiary hyperparathyroidism secondary to chronic kidney disease. After anti-thymocyte globulin induction, the maintenance regimen consisted of azathioprine, tacrolimus, and corticosteroids. His baseline creatinine level was around 150 μmol/L, no proteinuria was detected, and a 3-month protocol graft biopsy was unremarkable. Three months after kidney transplantation, the patient developed primary cytomegalovirus infection despite valganciclovir prophylactic treatment in the setting of donor cytomegalovirus positive and recipient negative. No specific organ involvement was detected, and a ganciclovir-based regimen was started. Because of persistent viremia, 2 months after ganciclovir treatment, cytomegalovirus antiviral resistance testing was performed and a UL97 ganciclovir resistance mutation was detected. I.v. foscarnet treatment was initiated at 100 mg/kg per day.

Detection of Ganciclovir-Resistant Cytomegalovirus in a Prospective Cohort of Kidney Transplant Recipients Receiving Subtherapeutic Valganciclovir Prophylaxis.

ABSTRACTCytomegalovirus infection during antiviral prophylaxis occurs in transplant recipients despite individualized regimens based on renal function. Fifty kidney transplant recipients were assessed between 2016 and 2019 for valganciclovir dosing, ganciclovir exposure, cytomegalovirus infection, and genotypic resistance markers during the first year posttransplant. Ganciclovir plasma concentrations were measured using mass spectrometry. Population pharmacokinetics was used to determine individual ganciclovir exposure and to evaluate the ability of manufacturer dosing guidelines to meet therapeutic target daily area under the curve (AUC24) of 40 to 50 μg·h/mL. Full-length UL54 and UL97 were assessed using high-throughput sequencing in cytomegalovirus DNA-positive patient specimens. Valganciclovir doses administered to recipients with creatinine clearance of <40 mL/min were higher than specified by guidelines, and they were lower for recipients with creatinine clearance of ≥40 mL/min. The mean ganciclovir AUC24 was 33 ± 13 μg·h/mL, and 82% of subjects did not attain the therapeutic target. Pharmacokinetic simulations showed that the guidelines similarly could not attain the therapeutic target in 79% of individuals. Cytomegalovirus breakthrough occurred in 6% (3/50) of recipients, while 12% (6/50) developed late-onset infection. The mean AUC24s of recipients with (n = 3) and without (n = 47) infection were not significantly different (P = 0.528). However, one recipient with an AUC24 of 20 μg·h/mL acquired two UL97 ganciclovir resistance mutations. Current prophylaxis guidelines resulted in subtherapeutic ganciclovir exposure in several study recipients, including the emergence of resistance genotypes.IMPORTANCE This study examined the pharmacokinetics and viral genomic data from a prospective cohort of kidney transplant recipients undergoing valganciclovir prophylaxis for cytomegalovirus (CMV) prevention. We showed for the first time using high-throughput sequencing the detection of ganciclovir resistance mutations in breakthrough CMV infection during subtherapeutic plasma ganciclovir as indicated by the pharmacokinetic parameter daily area under the curve (AUC24). In addition, we found that current valganciclovir dosing guidelines for CMV prophylaxis are predicted to attain therapeutic targets in only 21% of recipients, which is consistent with previous pharmacokinetic studies. The novel findings of resistance mutations during subtherapeutic ganciclovir exposure presented here can inform future studies investigating the dynamics of drug selection pressure and the emergence of resistance mutations in vivo.

Cytomegalovirus UL97 ganciclovir resistance mutations in kidney transplant recipients.

Widespread and prolonged therapy with ganciclovir (GCV) may result in the emergence of GCV-resistant mutations in human cytomegalovirus (HCMV) genome. The aim of this study was to detect the UL97 mutations associated with GCV resistance in kidney transplant recipients. Forty-nine kidney recipients with positive HCMV DNAemia, who received GCV therapy were included in this study. A 707 bp fragment of UL97 gene spanning codons (436 to 655) was amplified by nested PCR and sequenced. Thirteen (26.5 %) out of 49 recipients contained mutations associated with amino acid changes. Two UL97 mutations related to GCV resistance were detected in 2 recipients (4 %), including alanine to valine (A594V) and proline to leucine (P521L). The D605E mutation was identified in 8 out of 49 (16.3 %) recipients. Silent mutations G598G, G503G, L553L, L634L, D456D and G579G were commonly observed. Our results indicate that mutations in the UL97 gene associated with GCV resistance may occur in 1 in 25 recipients treated with GCV. In addition, a higher mutation rate of D605E was detected in our recipients. This study provides the first evidence of the prevalence and pattern of GCV related mutations in Iranian Turkish recipients (Tab. 2, Fig. 1, Ref. 28).

Development and Dynamics of Cytomegalovirus UL97 Ganciclovir Resistance Mutations in Transplant Recipients Detected by Next-Generation Sequencing.

Background(Val)ganciclovir resistance mutations in CMV UL97 (UL97-GCV-R) complicate anti-CMV therapy in recipients of solid organ and hematopoietic stem cell transplants, but comprehensive data on prevalence, emergence, and outcome are scarce.MethodsUsing next-generation sequencing (NGS; Illumina MiSeq platform), we analyzed UL97-GCV-R in patients with available plasma samples and refractory CMV replication/DNAemia (n = 87) containing viral loads ≥910 IU/mL. Twenty-one patients with CMV DNAemia resolving under antiviral therapy were analyzed as controls. Detected mutations were considered induced and of potential clinical significance if they increased by ≥10% compared with the first detected frequency or if they had a maximum frequency ≥25%.ResultsNineteen of 87 (21.8%) with refractory CMV replication had ≥1 UL97-GCV-R detected by NGS, in comparison to 0/21 of the controls (P = .02). One-third of the recipients had 2 or more induced UL97-GCV-R mutations. The most frequently induced mutations affected codons 595 (42% [8/19]), 594 (32% [6/19]), and 603 (32% [6/19]). C592G was present in all episodes of both cases and controls at frequencies <15%, but never induced. UL97-GCV-R tended to be more frequent in donor/recipient CMV immunoglobulin G mismatch or following failure to complete primary prophylaxis, and many developed invasive CMV disease.ConclusionsUL97-GCV-R is common among transplant patients with refractory CMV replication. Early testing by NGS allows for identification of major mutations at codons 595, 594, and 603 and excludes a major role of C592G in ganciclovir resistance. Large prospective studies on UL97-GCV-R are warranted.

Ganciclovir and maribavir susceptibility phenotypes of cytomegalovirus UL97 ATP binding region mutations detected by expanded genotypic testing

Because ganciclovir resistance mutations in the cytomegalovirus UL97 gene most commonly occur at codons 460, 520 and 590–607, diagnostic genotyping for drug resistance has often omitted the analysis of codons below 440. However, the UL97 kinase inhibitor maribavir selects for distinctive resistance mutations at codons 409 and 411, and ganciclovir/maribavir resistance mutations have also been described in the ATP binding region starting at codon 335. Expanded genotypic testing of UL97 codons 335–440 in 1535 clinical specimens disclosed 10 uncharacterized sequence variants that were phenotyped for ganciclovir and maribavir susceptibility. Notable findings included low-grade ganciclovir resistance conferred by amino acid substitutions K359N and E362D, decreased maribavir susceptibility of L348V, and maribavir hypersensitivity of V345I and E362D. Recently published substitutions F342Y and K359E/Q were also confirmed. The data indicate that mutations in the UL97 ATP binding region may arise in clinical specimens to affect the interpretation of ganciclovir and maribavir resistance. This region should now be included in the standard diagnostic genotyping of UL97, especially with the introduction of maribavir into therapeutic use.

Prevalence of UL97 gene mutations and polymorphisms in cytomegalovirus infection in the colon associated with or without ulcerative colitis

Cytomegalovirus (CMV) reactivation in the colon is common in patients with severe ulcerative colitis (UC). Ganciclovir (GCV) resistance conferring CMV UL97 gene mutations have been reported in recent years. However, the prevalence of UL97 gene mutations in GCV-naive CMV infection in the colon remains unknown. We investigated the prevalence of CMV UL97 gene mutations in patients with colonic CMV infection associated with or without UC. Twenty-two GCV-naive patients with colonic CMV infection, 15 with UC and 7 with other diseases, were enrolled. Frozen biopsy samples or formalin-fixed paraffin-embedded samples were used for nested polymerase chain reaction (PCR) amplification of the UL97 gene. Sanger DNA sequencing was performed. In comparison with AD169 reference strain, natural polymorphisms were frequently detected in codons N68D (100%), I244V (100%), and D605E (86.4%). Seven polymorphisms were detected infrequently (< 10%) outside the kinase domain. However, no known GCV resistance mutations were found. There seemed to be no difference between the ratio of polymorphisms in patients with and without UC. In conclusions, we did not detect UL97 gene mutations associated with GCV resistance in GCV-naive patients with or without UC. Consistent with previous reports, D605E polymorphism may be used as a genetic marker for CMV in East Asian countries.

Investigation of Ganciclovir Resistance in Cytomegalovirus Strains Obtained from Immunocompromised Patients

CMV is a virus that is asymptomatic in healthy individuals but can cause serious mortality and morbidity in transplant patients and patients with acquired immunodeficiency syndrome (AIDS). Ganciclovir (GCV) is a nucleoside analog that significantly reduces morbidity and mortality in CMV-related infections and is used as the first choice in treatment. It is the first drug shown to be effective in the treatment of CMV disease in humans, and is also homologous to acyclovir. Long-term antiviral therapy is required to prevent or treat CMV disease, but this can cause antiviral resistance which was reported to be 8-14% in CMV. In CMV strains, GCV resistance is most common in the UL97 kinase gene region. The aim of this study was to investigate GCV resistance in CMV strains obtained from the patients with immune deficiency. A total of 49 patients, including 20 children, 29 adults, who were followed in the department of hematology were included in the study. Fifty-three samples from 49 patients with CMV DNA viral load ≥ 103 copies/ml were examined for GCV resistance. In the study, DNA sequences were determined by Sanger sequence analysis method 3500 Abi Prism Genetic Analyser (Applied Biosystems, Thermo Fisher Scientific, USA) in the 674 bp part of the UL97 gene region. The next generation sequencing (NGS) method was applied to the samples that could not be evaluated with this method. GCV resistance was not detected in 35 (66%) of 53 samples with the Sanger method. C592G, C607S and M460I GCV resistance mutation was detected in three patients. Since the sequences were mixed, resistance analysis could not be evaluated with Sanger in 15 patient samples and the resistance was not detected in these samples studied with NGS. Antiviral resistance mutation was detected in three of 49 patients (6.1%). In 20 patients included in the study, three variant sequences (A442G, C592F, A427V) reported in the literature and determined to be sensitive to drugs by phenotypic tests and 78 variant sequences that were not reported in the literature were detected. As a result, the detection of antiviral resistance is important in the follow-up of the patients and guides the clinician in planning of the treatment. It was concluded that the samples that could not be evaluated with the Sanger method should be studied with NGS and further studies are needed to determine the role of the variant sequences detected for the first time in drug resistance.

Novel UL97 drug resistance mutations identified at baseline in a clinical trial of maribavir for resistant or refractory cytomegalovirus infection

In a Phase 2 clinical trial, 120 subjects with cytomegalovirus (CMV) infection refractory or resistant to standard therapy were randomized equally to 3 doses of oral maribavir treatment, and 70% achieved undetectable plasma CMV DNA within 12 weeks. At study entry, standard diagnostic UL97 genotyping was available for 71 subjects, with 60 (85%) revealing well-characterized ganciclovir resistance mutations that did not preclude a therapeutic response to maribavir. Central laboratory testing of a range of UL97 codons (288–468) not fully covered by standard genotyping was done on 93 subjects at baseline. This detected no previously known maribavir resistance mutations, but identified atypical mutations in 3 subjects, including a P-loop substitution F342Y, and ATP-binding region substitutions K359E/Q. By recombinant phenotyping, K359E and K359Q each conferred a nearly 4-fold increased ganciclovir 50% inhibitory concentration (EC50) without maribavir resistance, whereas F342Y conferred a 6-fold increased ganciclovir EC50 and a 4.5-fold increased maribavir EC50. The subject with F342Y detected at baseline did not achieve plasma CMV DNA clearance after 12 weeks of maribavir therapy and later developed an additional UL97 substitution H411Y known to confer 12- to 20-fold increased MBV EC50 by itself. The combination of F342Y and H411Y was shown to increase the maribavir EC50 by 56-fold. Diagnostic genotyping of UL97 should be expanded to cover the ATP-binding region beginning at codon 335 to enable the detection of atypical resistance mutations and further correlation of their clinical significance.

1584. Development and Dynamics of Cytomegalovirus UL97 Ganciclovir Resistance Mutations in Transplant Recipients Detected by Next-generation Sequencing

Background(Val)ganciclovir resistance mutations (GRMs) in CMV UL97 (UL97-GCV-R) complicate prophylaxis and therapy of solid-organ transplant (SOT) and hematopoietic (stem) cell transplant (HCT) recipients, but data on prevalence and dynamics are scarce. We investigated UL97-GCV-R using next-generation sequencing (NGS) in transplant recipients with refractory CMV DNAemia episodes and a control group.MethodsBetween January 1, 2010–July 16, 2016, 385 transplant recipients were screened for plasma CMV DNAemia. Eighty-seven patients (54 SOT, 33 HCT) with available plasma samples had refractory CMV replication at viral loads ≥910 IU/mL and were analysed by NGS. If UL97-GCV-R were detected in >10% of the NGS reads, all earlier plasma samples were also analysed by NGS. For comparison, this approach was also performed in a control group of 21 patients (14 SOT, 7 HSCT) with DNAemia episodes resolving under antiviral therapy. UL97-targeted NGS was performed using Illumina MiSeq and analysed by LoFreq for variant calling.ResultsOf the 87 recipients with refractory CMV replication, 19 (22%) had ≥1 UL97-GCV-R detected by NGS (Table 1, Figure 1), in comparison to 0/21 (0%) of the controls (P = 0.02). Fourteen of 19 of the resistant cases (20 induced mutations) had NGS performed <4 week from onset of infection; in this sample, the mutation was either not detected, detected as minority or dominating variant for 11, 7 and 2, respectively. In the majority of recipients one dominant mutant was induced (68%); ≥2 mutations were detected in the remaining recipients (Table 1). Most frequent UL97-GCV-R affected codon-595 (42%), -594 (32%) or -603 (32%). The % of C592G was low in in all episodes (<15%) without changing during the course (Figure 1). There was a trend toward higher frequencies of donor (D)/recipient (R) CMV high-risk mismatch, CMV disease and prior failure to valganciclovir prophylaxis (SOT) or treatment (HCT) among the cases with UL97-GCV-R (Figure 2).ConclusionUL97-GCV-R was seen in 22% of refractory CMV replication episodes. CMV D/R mismatch and CMV disease were more common amongst resistant cases. The C592G mutation was present in low frequency in all patients, suggesting that this mutation was part of the quasispecies, and not selected by ganciclovir resistance. Implications for clinical management will be discussed. Disclosures All authors: No reported disclosures.

A Novel Ganciclovir Resistance Mutation in the UL97 Gene of the HHV-5 in an Adult Hematopoietic Stem Cell Transplant Recipient

Therapeutic management of cytomegalovirus (CMV) disease in hematopoietic stem cell transplantation patients can become a challenge because of the emergence of anti-CMV drug resistance. This case report presents a patient with clinical ganciclovir resistance due to a new mutation: histidine-to-asparagine change at residue 393 of UL97. This mutation, which is located in the nonfunctional region of the UL97 gene, is very unusual. Having more information about the mutations leading to drug resistance in CMV is important for both improved clinical management and development of new diagnostic tests and drugs.

Human Cytomegalovirus UL54 and UL97 Mutations for Detection of Ganciclovir Resistance in Congenital Infection

Aim: Ganciclovir (GCV) is used as an antiviral drug for the treatment of human cytomegalovirus infection. The aim of this study was to demonstrate GCV-resistant human cytomegalovirus in congenitally infected neonates. Patients &amp; methods: DNA of CMV positive newborn samples was extracted and UL97 and UL54 genes were amplified by PCR and real-time PCR. Sequencing of UL97 and UL54 genes were performed and analyzed. Results: UL97 GCV resistance mutation C603W was detected in one newborn. D605E was the most common polymorphism in UL97 observed in 7/13 (53.8%) of samples. N685S, A688V, A885T and N898D were four known common UL54 polymorphisms. Conclusion: The rate of GCV resistance in congenital CMV is low. Common polymorphisms in UL97 and UL54 genes are also reported as new mutations.

Outcomes in Transplant Recipients Treated With Foscarnet for Ganciclovir-Resistant or Refractory Cytomegalovirus Infection.

Antiviral-resistant or refractory cytomegalovirus (CMV) infection is challenging, and salvage therapies, foscarnet, and cidofovir, have significant toxicities. Several investigational anti-CMV agents are under development, but more information is needed on outcomes of current treatments to facilitate clinical trial design for new drugs. Records of solid organ transplant (SOT) and hematopoietic cell transplant (HCT) recipients at a single center over a 10-year period were reviewed retrospectively to characterize those who had received foscarnet treatment for ganciclovir-resistant or refractory CMV infection. Data were collected on virologic responses, mortality, and nephrotoxicity. Of 39 patients (22 SOT, 17 HCT), 15 had documented ganciclovir resistance mutations and 11 (28%) of 39 had tissue-invasive CMV. Median duration of foscarnet was 32 days. Virologic failure occurred in 13 (33%) of 39 and relapses of viremia occurred in 31%. Mortality was 12 (31%) of 39 and was higher in HCT than SOT (P = 0.001), although ganciclovir resistance was more common in SOT (P = 0.003). Doses of ganciclovir or valganciclovir were low in 10 (26%) of 39 at some time before switching to foscarnet. Renal dysfunction occurred in 20 (51%) of 39 by end of treatment and in 7 (28%) of 25 after 6 months. Outcomes of existing treatment for ganciclovir-resistant or refractory CMV are suboptimal, in terms of virologic clearance, renal dysfunction, and mortality. These data should provide background information for future clinical trials of newer antiviral agents.

Detection of Low Frequency Multi-Drug Resistance and Novel Putative Maribavir Resistance in Immunocompromised Pediatric Patients with Cytomegalovirus.

Human cytomegalovirus (HCMV) is a significant pathogen in immunocompromised individuals, with the potential to cause fatal pneumonitis and colitis, as well as increasing the risk of organ rejection in transplant patients. With the advent of new anti-HCMV drugs there is therefore considerable interest in using virus sequence data to monitor emerging resistance to antiviral drugs in HCMV viraemia and disease, including the identification of putative new mutations. We used target-enrichment to deep sequence HCMV DNA from 11 immunosuppressed pediatric patients receiving single or combination anti-HCMV treatment, serially sampled over 1–27 weeks. Changes in consensus sequence and resistance mutations were analyzed for three ORFs targeted by anti-HCMV drugs and the frequencies of drug resistance mutations monitored. Targeted-enriched sequencing of clinical material detected mutations occurring at frequencies of 2%. Seven patients showed no evidence of drug resistance mutations. Four patients developed drug resistance mutations a mean of 16 weeks after starting treatment. In two patients, multiple resistance mutations accumulated at frequencies of 20% or less, including putative maribavir and ganciclovir resistance mutations P522Q (UL54) and C480F (UL97). In one patient, resistance was detected 14 days earlier than by PCR. Phylogenetic analysis suggested recombination or superinfection in one patient. Deep sequencing of HCMV enriched from clinical samples excluded resistance in 7 of 11 subjects and identified resistance mutations earlier than conventional PCR-based resistance testing in 2 patients. Detection of multiple low level resistance mutations was associated with poor outcome.

Drug Resistance due to Mutation in UL 97 and Certain Other Specific Genes in Cytomegalovirus Strains: An Overview

The study of human cytomegalovirus (HCMV) antiviral drug resistance has enhanced knowledge of the virological targets and the mechanisms of antiviral activity. The currently approved drugs, ganciclovir (GCV), foscarnet (FOS), and cidofovir (CDV), target the viral DNA polymerase. The widespread use of ganciclovir (GCV) to treat cytomegalovirus (CMV) infections in immuno-suppressed patients has led to the development of drug resistance.GCV anabolism also requires phosphorylation by the virus-encoded UL97 kinase. GCV resistance mutations have been identified in both genes, while FOS and CDV mutations occur only in the DNA polymerase gene. Confirmation of resistance mutations requires genotypic assays based on sequencing provide more rapid results but are dependent on prior validation by phenotypic methods. Recombinant phenotyping methods performed in a few research laboratories have resolved some of the conflicting results. Treatment options for drug-resistant HCMV infections are complex and have not been subjected to controlled clinical trials, although consensus guidelines have been proposed.

Detection of ganciclovir resistance mutations by pyrosequencing in HCMV-infected pediatric patients

BackgroundHuman cytomegalovirus (HCMV) is an opportunistic pathogen especially for immuno-suppressed subjects that might develop pharmacological resistance in patients undergoing prolonged antiviral treatment. Ganciclovir (GCV) is the drug used as first choice therapy in affected children and a GCV-resistant phenotype is mainly linked to mutations of the viral protein kinase UL97. ObjectivesHere a new quantitative pyrosequence (PSQ) method is presented that allows detection and quantification of the viral species carrying the more frequent UL97 mutations responsible for GCV resistance in clinical samples (>80% of known cases). Study designThe system has been validated using two independent approaches (cloning and sequencing of UL-97 gene fragments and real-time PCR) and clinical samples derived from 3 pediatric patients. ResultsThe UL97 pyrosequencing analysis has indicated a significant increase of mutant viruses carrying the H520Q and C592G mutations.In particular, the H520Q viral mutation, known to increase GCV resistance (IC50=10) increased around 5 times during hospitalization. In addition, C592G (known to have IC50=2.9) also increased 3 times. ConclusionsPSQ is a quick, cheap, high throughput and sensitive analysis method to detect GCV-associated resistance mutation useful to follow antiviral therapy in perinatal CMV-infection as well as in immune-suppressed patients.

Incidence of cytomegalovirus UL97 and UL54 amino acid substitutions detected after 100 or 200 days of valganciclovir prophylaxis

BackgroundThe IMPACT study was a randomized, double-blind study comparing 100 to 200 days of VGCV prophylaxis (900mg once daily) in D+/R− kidney transplant recipients. Although extending the duration of prophylaxis resulted in a significant reduction in confirmed cytomegalovirus (CMV) disease (100-day: 36.8% vs 200-day: 16.1%1), the consequence of extending the duration of prophylaxis on the development of viral resistance remains unknown. ObjectiveTo determine whether extending valganciclovir prophylaxis from 100 days to 200 days increased the incidence of ganciclovir resistance. Study designGenotypic analysis of CMV UL97 and UL54 was conducted on virus isolated from patients meeting the predefined resistance analysis criteria (RAC). ResultsA greater number of patients met the RAC in the 100 day prophylaxis arm (50/163; 31%) compared to the 200 day prophylaxis arm (22/155; 14%). Sequence data were successfully generated for all 200-day patients and 48/50 100-day patients. Three patients in each treatment arm (100 day: 3/163 (1.8%) vs 200 day: 3/155 (1.9%)) had a single known valganciclovir resistance mutation detected (100 day: UL97 gene: M460V, C592G twice; 200 day: UL97 gene: C603W, M460V and UL54 gene: P522S). Overall, a resistance mutation was more likely to be detected if the patient met the RAC during prophylaxis (5/12 (42%)) compared to post-prophylaxis (1/58 (2%)). All six patients with known ganciclovir resistance mutations cleared the virus; three cleared virus without treatment and three cleared virus following treatment. ConclusionsExtending valganciclovir prophylaxis from 100 days to 200 days did not significantly affect the incidence of ganciclovir resistance.

Detection of ganciclovir resistance mutations by pyrosequencing in a congenital infected newborn

Detection of ganciclovir resistance mutations by pyrosequencing in a congenital infected newborn

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.