Management of late, recurrent, and resistant cytomegalovirus in transplant patients

Commutability of Cytomegalovirus WHO International Standard in Different Matrices

Commutability of quantitative standards allows patient results to be compared across molecular diagnostic methods and laboratories. This is critical to establishing quantitative thresholds for use in clinical decision-making. A matrix effect associated with the 1st cytomegalovirus (CMV) WHO international standard (IS) was identified using the Abbott RealTime CMV assay. A commutability study was performed to compare the CMV WHO IS and patient specimens diluted in plasma and whole blood. Patient specimens showed similar CMV DNA quantitation values regardless of the diluent or extraction procedure used. The CMV WHO IS, on the other hand, exhibited a matrix effect. The CMV concentration reported for the WHO IS diluted in plasma was within the 95% prediction interval established with patient samples. In contrast, the reported DNA concentration of the CMV WHO IS diluted in whole blood was reduced approximately 0.4 log copies/ml, and values fell outside the 95% prediction interval. Calibrating the assay by using the CMV WHO IS diluted in whole blood would introduce a bias for CMV whole-blood quantitation; samples would be reported as having higher measured concentrations, by approximately 0.4 log IU/ml. Based on the commutability study with patient samples, the RealTime CMV assay was standardized based on the CMV WHO IS diluted in plasma. A revision of the instructions for use of the CMV WHO IS should be considered to alert users of the potential impact from the diluent matrix. The identification of a matrix effect with the CMV WHO IS underscores the importance of assessing commutability of the IS in order to achieve consistent results across methods.

Cytomegalovirus infection in liver transplant recipients: Updates on clinical management

Cytomegalovirus (CMV) infection is a common complication after liver transplantation, and it is associated with multiple direct and indirect effects. Management of CMV infection and disease has evolved over the years, and clinical guidelines have been recently updated. Universal antiviral prophylaxis and a pre-emptive treatment strategy are options for prevention. A currently-recruiting randomized clinical trial is comparing the efficacy and safety of the two prevention strategies in the highest risk D+R- liver recipients. Drug-resistant CMV infection remains uncommon but is now increasing in incidence. This highlights the currently limited therapeutic options, and the need for novel drug discoveries. Immunotherapy and antiviral drugs with novel mechanisms of action are being investigated, including letermovir (AIC246) and brincidofovir (CMX001). This article reviews the current state of CMV management after liver transplantation, including the updated practice guidelines, and summarizes the data on investigational drugs and vaccines in clinical development.

Cytomegalovirus infection in childhood-onset systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem disease with significant morbidity and even mortality. Cytomegalovirus (CMV) is a ubiquitous herpesvirus that, similar to SLE, can also lead to significant morbidity and mortality in the immunocompromised host. The relationship between SLE and CMV is complex, with observations suggesting that CMV induces the autoimmunity of SLE in addition to occurring in the immunocompromised host with known SLE. In this article, we first consider CMV infection in the immunocompetent host, and further examine how this infection differs in the patient with SLE. We focus on disease mechanisms, CMV detection and treatment. We review the differences between CMV infection, syndrome and disease, as identifying the correct state will determine the appropriate treatment. We propose guidelines for the screening and management of CMV infection in childhood-onset SLE, and recognize that further study in this population is required to increase our understanding of the interplay between these disease entities.

Managing complications following lung transplantation

Lung transplantation has become a proven therapeutic option for patients with end-stage lung disease, extending life and providing improved quality of life to those who otherwise would continue to be breathless and oxygen-dependent. Over the past 20 years, considerable experience has been gained in understanding the multitude of medical and surgical issues that impact upon patient survival. Today, clinicians have an armamentarium of tools to manage diverse problems such as primary graft dysfunction, acute and chronic allograft rejection, airway anastomotic issues, infectious complications, renal dysfunction, diabetes and osteoporosis, hematological and gastrointestinal problems, malignancy, and other unique issues that confront immunosuppressed solid organ transplant recipients.

Repopulation of ganciclovir-resistant cytomegalovirus by wild-type virus

We report a patient in whom ganciclovir (GCV)-resistant cytomegalovirus (CMV) was replaced by wild-type virus after discontinuation of GCV/valganciclovir and review other similar cases. Repopulation by wild-type virus may occur soon after discontinuation and may be fostered by discontinuing GCV altogether rather than continuing it in combination with foscarnet when treating patients with GCV-resistant CMV disease.

Defining the risks for cytomegalovirus infection and disease after solid organ transplantation

Cytomegalovirus continues to be one of the most clinically significant infections after solid organ transplantation. Classic definitions of patients at high risk for infection and tissue-invasive disease are focused on recipient-donor serostatus, type of organ transplanted, and overall level of immunosuppression. However, recent trends in clinical practice call for a reevaluation of cytomegalovirus infection risks after solid organ transplantation. Indeed, whereas early-onset cytomegalovirus infection is usually controlled by antiviral prophylaxis with ganciclovir and derivatives, delayed- and late-onset cytomegalovirus infection can develop after the completion of a course of preventive therapy. In addition, indirect effects of cytomegalovirus infection may occur as a result of persistent low-level viremia. Suboptimal dosing of antiviral drugs due to specific drug toxicities may result in the development of ganciclovir-resistant cytomegalovirus disease. The relationship between organ allograft rejection and cytomegalovirus infection and disease has been recognized for some time. Transplantation of increasing numbers of extended-criteria donor organs increases the risk of delayed graft function and acute rejection, prompting the use of more intensive immunosuppression. In addition, the trend to spare long-term exposure to calcineurin inhibitors has contributed to a resurgence in the use of polyclonal T-cell induction immunosuppressive agents, which may reduce host anticytomegalovirus immunity. We discuss the current trends in solid organ transplantation that provide a foundation for defining risks for cytomegalovirus infection and disease, including identification of patients who would benefit from more aggressive cytomegalovirus monitoring and prevention strategies.

Fluorescence-based assay for phenotypic characterization of human cytomegalovirus polymerase mutations regarding drug susceptibility and viral replicative fitness

One essential prerequisite for genotypic drug susceptibility testing of human cytomegalovirus (HCMV) is the phenotypic characterization of mutations identified in the viral protein kinase gene UL97 and the viral DNA polymerase gene UL54 regarding their quantitative impact on drug susceptibility. We developed a new method for phenotypic characterization of UL54 mutations with regard to polymerase activity, viral replication, and drug susceptibility. To determine the most suitable viral indicator gene, enhanced green fluorescence protein was C-terminally fused to the HCMV early-late protein UL83 (pp65) or the late proteins UL32 (pp150) and UL99 (pp28), resulting in reporter viruses vTB65g, vTB150g, and vTB28g. vTB65g proved to be superior to the other constructs due to its favorable signal-to-noise ratio and was therefore used to establish the optimum conditions for our assay. The UL54 E756K and D413E mutations were introduced into vTB65g by markerless bacterial artificial chromosome mutagenesis, resulting in virus strains vE756Kg and vD413Eg. The drug susceptibility phenotypes of vE756Kg and vD413Eg were comparable to those previously reported. Furthermore, we found a reduced replicative fitness of vE756Kg by measuring fluorescence intensity as well as by conventional virus growth kinetics. Decreased fluorescence signals of vE756Kg- and vD413Eg-infected cells at late times of infection suggested a reduced polymerase activity, which was confirmed by real-time PCR quantification of the newly synthesized viral DNAs. This new fluorescence-based assay is a highly reproducible method for the phenotypic characterization of mutations potentially influencing drug susceptibility, viral replicative fitness, and polymerase activity of HCMV after marker transfer.

Antiviral treatment of cytomegalovirus infection and resistant strains

This review discusses the management of resistant cytomegalovirus and prevention strategies for fatal therapy failures. Five drugs, ganciclovir/valganciclovir, cidofovir, foscarnet and fomivirsen, have been approved so far for the treatment of human cytomegalovirus (HCMV) diseases. Except for fomivirsen, all of the approved drugs share the same target molecule, the viral DNA polymerase. The emergence of drug-resistant HCMV has also been reported for all of them. For optimal care of patients, the clinical virologist has to provide the most meaningful assays for monitoring of therapy and early detection of emerging drug-resistant HCMV. Additionally, a quantitative drug monitoring would be helpful. New antiviral agents are urgently needed with less adverse effects, good oral bioavailability and possibly novel targets or mechanisms of action to avoid cross-resistance and to improve the ability to suppress the selection of resistant virus strains by combination therapy. Compounds like maribavir, leflunomide and artesunate, which exhibit anti-HCMV activity in vitro and in patients need to be evaluated in clinical studies. Besides these, new therapy approaches like immunotherapy or new diagnostic techniques like pyrosequencing have to be considered in the future.