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Journal of Virology May 2014The human cytomegalovirus (HCMV)-encoded kinase pUL97 is required for efficient viral replication. Previous studies described two isoforms of pUL97, the full-length...
UNLABELLED
The human cytomegalovirus (HCMV)-encoded kinase pUL97 is required for efficient viral replication. Previous studies described two isoforms of pUL97, the full-length isoform (M1) and a smaller isoform likely resulting from translation initiation at codon 74 (M74). Here, we report the detection of a third pUL97 isoform during viral infection resulting from translation initiation at codon 157 (isoform M157). The consistent expression of isoform M157 as a minor component of pUL97 during infection with clinical and laboratory-adapted HCMV strains was suppressed when codon 157 was mutagenized. Viral mutants expressing specific isoforms were generated to compare their growth and drug susceptibility phenotypes, as well as pUL97 intracellular localization patterns and kinase activities. The exclusive expression of isoform M157 resulted in substantially reduced viral growth and resistance to the pUL97 inhibitor maribavir while retaining susceptibility to ganciclovir. Confocal imaging demonstrated reduced nuclear import of amino-terminal deletion isoforms compared to isoform M1. Isoform M157 showed reduced efficiency of various substrate protein interactions and autophosphorylation, whereas Rb phosphorylation was preserved. These results reveal differential properties of pUL97 isoforms that affect viral replication, with implications for the antiviral efficacy of maribavir.
IMPORTANCE
The HCMV UL97 kinase performs important functions in viral replication that are targeted by the antiviral drug maribavir. Here, we describe a naturally occurring short isoform of the kinase that when expressed by itself in a recombinant virus results in altered intracellular localization, impaired growth, and high-level resistance to maribavir compared to those of the predominant full-length counterpart. This is another factor to consider in explaining why maribavir appears to have variable antiviral activity in cell culture and in vivo.
Topics: Antiviral Agents; Benzimidazoles; Cytomegalovirus; Humans; Microbial Sensitivity Tests; Phosphotransferases (Alcohol Group Acceptor); Protein Isoforms; Ribonucleosides; Virus Replication
PubMed: 24522923
DOI: 10.1128/JVI.00192-14 -
American Journal of Transplantation :... Oct 2009Maribavir is being developed as a novel agent for the prevention or treatment of cytomegalovirus infections after stem cell and organ transplantation. This was a... (Randomized Controlled Trial)
Randomized Controlled Trial
Maribavir is being developed as a novel agent for the prevention or treatment of cytomegalovirus infections after stem cell and organ transplantation. This was a randomized, double-blind, placebo-controlled study designed to evaluate the potential pharmacokinetic interaction of concomitant administration of maribavir and tacrolimus. Twenty-five adult renal transplant recipients with stable renal function and stable dosing regimens of tacrolimus were randomized (20 maribavir 400 mg p.o. q12 h: 5 placebo). Tacrolimus whole blood concentration profiles were determined before and after 7 days of co-administration with maribavir. When co-administered with maribavir, tacrolimus mean C(max) increased 38%, tacrolimus trough concentrations (12 h post-dose) increased 57% and tacrolimus AUC((0-tau)) increased 51%. Apparent oral clearance of tacrolimus decreased 34% and T(max) was delayed by 0.5 h. There were no serious adverse events and no subject prematurely discontinued treatment. Because of the limited 7-day dosing course, the adverse event profile could not be adequately assessed. However, as seen with other maribavir studies, dysgeusia was common (90% of maribavir subjects and 20% of placebo subjects). In conclusion, co-administration of maribavir 400 mg twice daily increases exposure to tacrolimus. Routine therapeutic drug monitoring of tacrolimus blood concentrations should be included both at initiation and completion of maribavir treatment.
Topics: Administration, Oral; Adult; Area Under Curve; Benzimidazoles; Double-Blind Method; Drug Therapy, Combination; Female; Humans; Immunosuppressive Agents; Kidney Transplantation; Male; Middle Aged; Placebos; Ribonucleosides; Tacrolimus
PubMed: 19663892
DOI: 10.1111/j.1600-6143.2009.02768.x -
Molecules (Basel, Switzerland) Oct 2020The strong inhibition of Human Cytomegalovirus (HCMV) replication by benzimidazole nucleosides, like Triciribine and Maribavir, has prompted us to expand the...
The strong inhibition of Human Cytomegalovirus (HCMV) replication by benzimidazole nucleosides, like Triciribine and Maribavir, has prompted us to expand the structure-activity relationships of the benzimidazole series, using as a central core the imidazo[4,5-b]pyridine scaffold. We have thus synthesized a number of novel amino substituted imidazopyridine nucleoside derivatives, which can be considered as 4-(or 7)-aza-d-isosters of Maribavir and have evaluated their potential antiviral activity. The target compounds were synthesized upon glycosylation of suitably substituted 2-aminoimidazopyridines, which were prepared in six steps starting from 2-amino-6-chloropyridine. Even if the new compounds possessed only a slight structural modification when compared to the original drug, they were not endowed with interesting antiviral activity. Even so, three derivatives showed promising cytotoxic potential.
Topics: Antiviral Agents; Benzimidazoles; Cell Line; Cytomegalovirus; Glycosylation; Humans; Imidazoles; Nucleosides; Pyridines; Ribonucleosides
PubMed: 33022923
DOI: 10.3390/molecules25194531 -
F1000Research 2018Undergoing solid organ transplantation (SOT) exposes the recipient to various infectious risks, including possible transmission of pathogen by the transplanted organ,... (Review)
Review
Undergoing solid organ transplantation (SOT) exposes the recipient to various infectious risks, including possible transmission of pathogen by the transplanted organ, post-surgical infections, reactivation of latent pathogens, or novel infections. In the last few years, the emergence of Zika virus has raised concerns in the transplant community. Few cases have been described in SOT patients, and these were associated mainly with moderate disease and favorable outcome; the notable exception is a recent case of fatal meningo-encephalopathy in a heart transplant recipient. Because of the advances in treating hepatitis C, several teams recently started to use organs from hepatitis C-positive donors. The worldwide increasing incidence of multidrug-resistant pathogens, as well as the increasing incidence of infection, is of particular concern in SOT patients. In the field of mycology, the main recent therapeutic advance is the availability of isavuconazole for the treatment of invasive aspergillosis and mucormycosis. This drug has the advantage of minimal interaction with calcineurin inhibitors. Regarding the viral reactivations occurring after transplant, cytomegalovirus (CMV) infection is still a significant issue in SOT patients. The management of resistant CMV remains particularly difficult. The approval of letermovir, albeit in bone marrow transplantation, and the therapeutic trial of maribavir bring a ray of hope. Another advancement in management of post-transplant infections is the development of tests evaluating pathogen-specific immune response, such as immunodiagnostics for CMV and, more recently, tests for monitoring immunity against BK virus. The increasing number of organ transplantations, the use of newer immunosuppressive drugs, and high-risk donors continue to define the landscape of transplant infectious diseases in the current era.
PubMed: 29899970
DOI: 10.12688/f1000research.14262.1 -
Journal of Clinical Microbiology Feb 2021
PubMed: 33826525
DOI: 10.1128/JCM.00118-20 -
Antiviral Research Sep 2018The human cytomegalovirus (CMV) UL97 kinase inhibitor maribavir is in Phase III clinical trials as antiviral therapy, including use for infections refractory or...
The human cytomegalovirus (CMV) UL97 kinase inhibitor maribavir is in Phase III clinical trials as antiviral therapy, including use for infections refractory or resistant to standard therapy. To assess its activity in combination with approved and experimental CMV antivirals, and with the mTor inhibitor rapamycin (sirolimus), drug effects were tested by in vitro checkerboard assays and the data were analyzed using a three dimensional model based on an independent effects definition of additive interactions. Baseline virus and representative drug-resistant mutants were tested. According to the volume of synergy at 95% confidence, maribavir showed additive interactions with foscarnet, cidofovir, letermovir and GW275175X when tested against wild type and mutant viruses, strong antagonism with ganciclovir, and strong synergy with rapamycin, the latter suggesting a potentially useful therapeutic combination.
Topics: Antiviral Agents; Benzimidazoles; Cell Line; Cytomegalovirus; Drug Interactions; Humans; Microbial Sensitivity Tests; Ribonucleosides
PubMed: 30040968
DOI: 10.1016/j.antiviral.2018.07.013 -
Antimicrobial Agents and Chemotherapy Dec 2020Congenital cytomegalovirus (HCMV) infection may cause significant fetal malformation, lifelong disease, and, in severe cases, fetal or neonatal death. Placental...
Congenital cytomegalovirus (HCMV) infection may cause significant fetal malformation, lifelong disease, and, in severe cases, fetal or neonatal death. Placental infection with HCMV is the major mechanism of mother-to-child transmission (MTCT) and fetal injury. Thus, any pharmaceutical antiviral interference to reduce viral load may reduce placental damage, MTCT, and fetal disease. However, there is currently no licensed HCMV antiviral for use during pregnancy. In this study, aciclovir and the HCMV-specific antivirals letermovir, maribavir, and cidofovir were compared with ganciclovir for antiviral effects in model systems of pregnancy, including first-trimester TEV-1 trophoblast cell cultures and third-trimester placental explant histocultures. HCMV-infected trophoblasts at 7 days postinfection (dpi) showed an EC of 21 μM for aciclovir, 0.0007 μM for letermovir, 0.11 μM for maribavir, and 0.29 μM for cidofovir, relative to 0.42 μM for ganciclovir. Antivirals added at 10 μM showed no cytotoxic effects and did not affect trophoblast cell proliferation ( > 0.9999). Multiple-round HCMV replication measured at 7 dpi showed letermovir, maribavir, and cidofovir treatment inhibited immediate early, early, and true late viral protein expression as assayed on Western blots. Antiviral treatment of HCMV-infected placental explants showed significant inhibition ( 0.05) of viral replication with letermovir (83.3%), maribavir (83.6%), cidofovir (89.3%), and ganciclovir (82.4%), but not aciclovir ( > 0.9999). In model systems, recently trialed HCMV antivirals letermovir and maribavir were effective at inhibiting HCMV replication. They partly fulfil requirements for use as safe and effective therapeutics during pregnancy to control congenital HCMV. Clinical trials of these newer agents would assist assessment of their utility in pregnancy.
Topics: Antiviral Agents; Child; Cytomegalovirus; Cytomegalovirus Infections; Female; Humans; Infant, Newborn; Infectious Disease Transmission, Vertical; Placenta; Pregnancy; Virus Replication
PubMed: 33077661
DOI: 10.1128/AAC.01627-20 -
Microorganisms Apr 2020Human cytomegalovirus (HCMV) expresses a variety of viral regulatory proteins that undergo close interaction with host factors including viral-cellular multiprotein... (Review)
Review
Human cytomegalovirus (HCMV) expresses a variety of viral regulatory proteins that undergo close interaction with host factors including viral-cellular multiprotein complexes. The HCMV protein kinase pUL97 represents a viral cyclin-dependent kinase ortholog (vCDK) that determines the efficiency of HCMV replication via phosphorylation of viral and cellular substrates. A hierarchy of functional importance of individual pUL97-mediated phosphorylation events has been discussed; however, the most pronounced pUL97-dependent phenotype could be assigned to viral nuclear egress, as illustrated by deletion of the UL97 gene or pharmacological pUL97 inhibition. Despite earlier data pointing to a cyclin-independent functionality, experimental evidence increasingly emphasized the role of pUL97-cyclin complexes. Consequently, the knowledge about pUL97 involvement in host interaction, viral nuclear egress and additional replicative steps led to the postulation of pUL97 as an antiviral target. Indeed, validation experiments in vitro and in vivo confirmed the sustainability of this approach. Consequently, current investigations of pUL97 in antiviral treatment go beyond the known pUL97-mediated ganciclovir prodrug activation and henceforward include pUL97-specific kinase inhibitors. Among a number of interesting small molecules analyzed in experimental and preclinical stages, maribavir is presently investigated in clinical studies and, in the near future, might represent a first kinase inhibitor applied in the field of antiviral therapy.
PubMed: 32260430
DOI: 10.3390/microorganisms8040515 -
The Journal of Antimicrobial... May 2009Cytomegalovirus (CMV) infection is the most common cause of congenital infection in the developed world, occurring in approximately 1% of all liveborns. Symptomatic... (Review)
Review
Cytomegalovirus (CMV) infection is the most common cause of congenital infection in the developed world, occurring in approximately 1% of all liveborns. Symptomatic disease occurs in 10% of all congenitally infected infants, resulting in a spectrum of clinical manifestations that include microcephaly, chorioretinitis, hepatosplenomegaly and sensorineural hearing loss, among others. Even those children who are asymptomatic at birth have a risk of hearing loss, with approximately 8% experiencing this sequela. Overall, congenital CMV infection accounts for one-third of all cases of sensorineural hearing loss. The economic burden of disease exceeds $2 billion annually in the USA. Therefore, this infection has been the target for antiviral therapy. Studies performed by the National Institute of Allergy and Infectious Diseases Collaborative Antiviral Study Group (CASG) have evaluated ganciclovir for the treatment of symptomatic congenital CMV infection with central nervous system involvement. In a randomized, controlled clinical trial of ganciclovir treatment (6 mg/kg iv every 12 h for 6 weeks) brainstem-evoked responses were utilized as the primary endpoint and demonstrated stabilization of hearing both at 6 months and >1 year. Treatment was associated with neutropenia in over 60% of treated patients. Since ganciclovir must be given intravenously, studies with its prodrug, valganciclovir, have been performed to assess pharmacokinetics and pharmacodynamics. Currently, a clinical trial of 6 weeks versus 6 months of valganciclovir is being performed by the CASG. Notably, only intravenous ganciclovir and orally administered valganciclovir have been used to treat congenital CMV infection. Hopefully, other drugs such as maribavir will be available for evaluation in this population.
Topics: Antiviral Agents; Clinical Trials as Topic; Cytomegalovirus Infections; Ganciclovir; Hearing Loss, Central; Humans; Infant; Neutropenia; United States; Valganciclovir
PubMed: 19287011
DOI: 10.1093/jac/dkp083