Predictors of Cytomegalovirus Recurrence Following Cessation of Posttransplant Prophylaxis

INTRODUCTION

Cytomegalovirus (CMV) infection is associated with a poor prognosis after lung transplantation, and donor and recipient CMV serostatus is a risk factor for reactivation. CMV prophylaxis is commonly administered in the first year following transplantation to reduce CMV infection; however, the risk factors for long-term reactivation remain unclear. We investigated the timing and risk factors of CMV infection after prophylactic administration.

METHODS

This study was a retrospective review of the institutional lung transplantation database from June 2014 to June 2022. Data on patient characteristics, pretransplantation laboratory values, postoperative outcomes, and CMV infection were collected. Donor CMV-IgG-positive and recipient CMV-IgG-negative groups were defined as the CMV mismatch group.

RESULTS

During the study period, 257 patients underwent lung transplantation and received a prophylactic dose of valganciclovir hydrochloride for up to 1 y. CMV infection was detected in 69 patients (26.8%): 40 of 203 (19.7%) in the non-CMV mismatch group and 29 of 54 (53.7%) in the CMV mismatch group (P < 0.001). CMV infection after prophylaxis occurred at a median of 425 and 455 d in the CMV mismatch and non-CMV mismatch groups, respectively (P = 0.07). Multivariate logistic regression analysis revealed that preoperative albumin level (odds ratio [OR] = 0.39, P = 0.04), CMV mismatch (OR = 15.7, P < 0.001), and donor age (OR = 1.05, P = 0.009) were significantly associated with CMV infection.

CONCLUSIONS

CMV mismatch may have increased the risk of CMV infection after lung transplantation, which decreased after prophylaxis. In addition to CMV mismatch, low preoperative albumin level and donor age were independent predictors of CMV infection.

Next-generation sequencing for cytomegalovirus genotypic antiviral resistance testing

Sanger-based sequencing has long served as the gold standard for detecting cytomegalovirus (CMV) resistance mutations. However, next-generation sequencing (NGS) offers a highly multiplexed and sensitive approach. Clinical implementation of NGS-antiviral resistance testing requires thorough validation. In this issue of the Journal of Clinical Microbiology, M. A. Mallory, W. C. Hymas, K. E. Simmon, M. T. Pyne, et al. (J Clin Microbiol 61:e00829-23, 2023, https://doi.org/10.1128/jcm.00829-23) detail a validation of a targeted NGS-based assay for multiple genomic regions that confer resistance to CMV antivirals and share their bioinformatics analysis and reporting pipeline. This validation can serve as guidance for laboratories wishing to develop similar methodologies.

Clinical next-generation sequencing assay combining full-length gene amplification and shotgun sequencing for the detection of CMV drug resistance mutations

Cytomegalovirus (CMV) causes severe systemic and tissue-invasive disease in immunocompromised patients, particularly solid organ and hematopoietic stem cell transplant recipients. While antiviral drugs offer promising efficacy, clinical management is complicated by the high frequency of drug resistance-associated mutations. The most commonly encountered mutations occur in the genes encoding for the drug targets: UL54 (DNA polymerase), UL56 (terminase complex), and UL97 (phosphotransferase), conferring resistance to ganciclovir/cidofovir/foscarnet, letermovir, and ganciclovir/maribavir, respectively. Currently, standard practice for detecting drug resistance is sequencing-based genotypic analysis by commercial reference laboratories with strictly prescribed sample requirements and reporting parameters that can often restrict testing in a highly vulnerable population. In order to circumvent these limitations, we developed a dual-step next-generation sequencing (NGS)-based clinical assay that utilizes full-length gene amplification by long-range PCR followed by shotgun sequencing for mutation analysis. This laboratory-developed test (LDT) achieved satisfactory performance with 96.4% accuracy, 100% precision, and an analytical sensitivity of 300IU/mL with 20% allele frequency. Highlighted by two clinical cases, our NGS LDT was able to provide critical results from patient specimens with viral loads <500IU/mL and volumes <0.5 mL - conditions otherwise unacceptable by reference laboratories. Here, we describe the development and implementation of a robust NGS LDT that offers greater testing flexibility and sensitivity to accommodate a more diverse patient population.

Therapeutic Drug Monitoring of Ganciclovir: Where Are We?

BACKGROUND

Ganciclovir is the mainstay of therapy for the prophylaxis and treatment of Cytomegalovirus. However, therapy with this antiviral agent is hindered by side effects such as myelosuppression, which often leads to therapy cessation. Underdosing, as an attempt to prevent side effects, can lead to drug resistance and therapy failure. Therapeutic drug monitoring (TDM) has been used to overcome these problems. The purpose of this narrative review was to give an overview of ganciclovir TDM, available assays, population pharmacokinetic models, and discuss the current knowledge gaps.

METHODS

For this narrative review, a nonsystematic literature search was performed on the PubMed database in April 2021. The following search terms were used: ganciclovir, valganciclovir, pharmacokinetics, pharmacodynamics, population pharmacokinetics, therapeutic drug monitoring, bioassay, liquid chromatography coupled with tandem mass spectrometry, liquid chromatography, chromatography, spectrophotometry, and toxicity. In addition, the reference lists of the included articles were screened.

RESULTS

The most common bioanalysis method identified was liquid chromatography coupled with tandem mass spectrometry. There are different models presenting ganciclovir IC50; however, establishing a pharmacokinetic/pharmacodynamic target for ganciclovir based on preclinical data is difficult because there are no studies combining dynamic drug exposure in relation to inhibition of viral replication. The data on ganciclovir TDM show large interindividual variability, indicating that TDM may play a role in modifying the dose to reduce toxicity and prevent treatment failure related to low concentrations. The main hurdle for implementing TDM is the lack of robust data to define a therapeutic window.

CONCLUSIONS

Although the pharmacokinetics (PK) involved is relatively well-described, both the pharmacodynamics (PD) and pharmacokinetic/pharmacodynamic relationship are not. This is because the studies conducted to date have mainly focused on estimating ganciclovir exposure, and owing to the limited therapeutic options for CMV infections, future studies on ganciclovir are warranted.

Pentostatin antagonizes the antiviral activity of MBX-2168 by inhibiting the biosynthesis of the active compound

MBX-2168 has a mechanism of action similar to that of acyclovir (ACV) and ganciclovir (GCV), but two unique steps differentiate this drug from ACV/GCV. First, MBX-2168 is, at least partially, phosphorylated by the endogenous cellular kinase TAOK3 to a monophosphate. The second involves the removal of a moiety at the 6-position of MBX-2168-MP by adenosine deaminase like protein-1 (ADAL-1). It has been previously demonstrated that co-incubation with pentostatin (dCF), an ADAL-1 inhibitor, antagonizes the anti-viral activity of MBX-2168. We therefore hypothesize that inhibiting ADAL-1 results in a reduction of active compound produced in virus-infected cells. To test this, we examined the effect dCF has on the conversion of MBX-2168 to a triphosphate in HSV-1 and HCMV-infected cells. Our results demonstrate incubation of MBX-2168 alone or with dCF in HCMV-infected cells resulted in 53.1 ± 0.7 and 39.4 ± 1.5 pmol triphosphate/10⁶ cells at 120 h, respectively. Incubation of MBX-2168 alone or with dCF in Vero cells resulted in 12.8 ± 0.1 and 6.7 ± 0.7 pmol triphosphate/10⁶ cells at 24 h, respectively. HSV-1-infected Vero cells demonstrated no statistical difference in triphosphate accumulation at 24 h (13.1 ± 0.3 pmol triphosphate/10⁶ cells). As expected, incubation with dCF resulted in the accumulation of MBX-2168-MP in both HFF (9.8 ± 0.9 pmol MBX-2168-MP/10⁶ cells at 120 h) and Vero cells (4.7 ± 0.3 pmol MBX-2168-MP/10⁶ cells at 24 h) while no detectable levels of monophosphate were observed in cultures not incubated with dCF. We conclude that dCF antagonizes the anti-viral effect of MBX-2168 by inhibiting the production of triphosphate, the active compound.

Definitions of Resistant and Refractory Cytomegalovirus Infection and Disease in Transplant Recipients for Use in Clinical Trials

Despite advances in preventive strategies, cytomegalovirus (CMV) infection remains a major complication in solid organ and hematopoietic cell transplant recipients. CMV infection may fail to respond to commercially available antiviral therapies, with or without demonstrating genotypic mutation(s) known to be associated with resistance to these therapies. This lack of response has been termed "resistant/refractory CMV" and is a key focus of clinical trials of some investigational antiviral agents. To provide consistent criteria for future clinical trials and outcomes research, the CMV Resistance Working Group of the CMV Drug Development Forum (consisting of scientists, clinicians, regulatory officials, and industry representatives from the United States, Canada, and Europe) has undertaken establishing standardized consensus definitions of "resistant" and "refractory" CMV. These definitions have emerged from the Working Group's review of the available virologic and clinical literature and will be subject to reassessment and modification based on results of future studies.

Biosynthesis and half-life of MBX-2168-triphosphate in herpes virus-infected cells

The third generation of methylenecyclopropane nucleoside analogs (MCPNAs) elicit an anti-viral effect against all three sub-classes of herpes viruses without inducing cytotoxicity in vitro. It has been previously established that the mechanism of action of MCPNAs is similar to that of ganciclovir (GCV) or acyclovir (ACV). However, the activation of MBX-2168, a third generation MCPNA, involves additional and unique enzymatic steps and this process has not been examined in virus-infected cells. To that end, herpes virus-infected cells were incubated with MBX-2168, synguanol, GCV, or ACV. Incubation of HCMV-infected cells with five times the EC₅₀ of MBX-2168 (4.0 μM), synguanol (10.5 μM), or GCV (25 μM) resulted in a time-dependent increase in triphosphate accumulation reaching a maximum of 48.1 ± 5.5, 45.5 ± 2.5, and 42.6 ± 3.7 pmol/10⁶ cells at 120 h, respectively. Additionally, half-lives of these compounds were similar in HCMV-infected cells (GCV-TP = 25.5 ± 2.7 h; MBX-2168-TP/synguanol-TP = 23.0 ± 1.4 h). HSV-1-infected cells incubated with five times the EC₅₀ of MBX-2168 (33.5 μM) or ACV (5.0 μM) demonstrated a time-dependent increase in triphosphate levels reaching a maximum of 12.3 ± 1.5 and 11.6 ± 0.7 pmol/10⁶ cells at 24 h, respectively. ACV-TP and MBX-2168-TP also had similar half-lives under these conditions (27.3 ± 4.8 h and 22.2 ± 2.2 h, respectively). We therefore conclude that although MBX-2168 does not follow the classical route of nucleoside analog activation, the metabolic profile of MBX-2168 is similar to other nucleoside analogs such as GCV and ACV that do.

Infectious Complications Following Kidney Transplantation-A Focus on Hepatitis C Infection, Cytomegalovirus Infection and Novel Developments in the Gut Microbiota

The incidence of infectious complications, compared with the general population and the pre-transplant status of the recipient, increases substantially following kidney transplantation, causing significant morbidity and mortality. The potent immunosuppressive therapy given to prevent graft rejection in kidney transplant recipients results in an increased susceptibility to a wide range of opportunistic infections including bacterial, viral and fungal infections. Over the last five years, several advances have occurred that may have changed the burden of infectious complications in kidney transplant recipients. Due to the availability of direct-acting antivirals to manage donor-derived hepatitis C infection, this has opened the way for donors with hepatitis C infection to be considered in the donation process. In addition, there have been the development of medications targeting the growing burden of resistant cytomegalovirus, as well as the discovery of the potentially important role of the gastrointestinal microbiota in the pathogenesis of post-transplant infection. In this narrative review, we will discuss these three advances and their potential implications for clinical practice.

Targeting the terminase: An important step forward in the treatment and prophylaxis of human cytomegalovirus infections

A key step in the replication of human cytomegalovirus (HCMV) in the host cell is the generation and packaging of unit-length genomes into preformed capsids. Enzymes required for this process are so-called terminases, first described for double-stranded DNA bacteriophages. The HCMV terminase consists of the two subunits, the ATPase pUL56 and the nuclease pUL89, and a potential third component pUL51. The terminase subunits are essential for virus replication and are highly conserved throughout the Herpesviridae family. Together with the portal protein pUL104 they form a powerful biological nanomotor. It has been shown for tailed dsDNA bacteriophages that DNA translocation into preformed capsid needs an extraordinary amount of energy. The HCMV terminase subunit pUL56 provides the required ATP hydrolyzing activity. The necessary nuclease activity to cleave the concatemers into unit-length genomes is mediated by the terminase subunit pUL89. Whether this cleavage is mediated by site-specific duplex nicking has not been demonstrated, however, it is required for packaging. Binding to the portal is a prerequisite for DNA translocation. To date, it is a common view that during translocation the terminase moves along some domains of the DNA by a binding and release mechanism. These critical structures have proven to be outstanding targets for drugs to treat HCMV infections because corresponding structures do not exist in mammalian cells. Herein we examine the HCMV terminase as a target for drugs and review several inhibitors discovered by both lead-directed medicinal chemistry and by target-specific design. In addition to producing clinically active compounds the research also has furthered the understanding of the role and function of the terminase itself.

Resistant cytomegalovirus infection in renal transplant recipients

Resistant cytomegalovirus infection is a significant problem in the transplant population including renal transplant recipients. A combination of factors including receipt of potent immunosuppression, high viral loads and suboptimal levels of anti-cytomegalovirus antivirals leads to emergence of resistant strains. Reports of associated poor graft survival and mortality demonstrate the potential pathogenic nature of such strains. Genotypic and phenotypic resistance testing are available for laboratory diagnosis of resistant cytomegalovirus infection and may help guide therapy. Various agents, including novel and newly minted antivirals and treatment approaches have been employed, with variable success. Thus, in spite of major advances in both diagnostics and therapeutics, management of resistant cytomegalovirus infection in renal transplant recipients remains a challenging prospect.

Review article: cytomegalovirus and inflammatory bowel disease

BACKGROUND

The association between ulcerative colitis and cytomegalovirus (CMV) has been recognised for over 50 years; and the role of CMV in ulcerative colitis in general, and steroid resistance in particular, remains a topic of ongoing controversy. The outcome for patients with CMV reactivation appears worse than that for patients without reactivation, but it is not entirely clear whether CMV is a contributor or a bystander and if treatment with anti-virals alters the course of inflammatory bowel disease (IBD).

AIM

To review the role of CMV associated with IBD, including epidemiology, clinical features, diagnosis and management strategies.

METHODS

By reviewing literature available on CMV associated with IBD in adult patients. A PubMed literature search was performed using the following terms individually or in combination: CMV colitis, cytomegalovirus colitis, IBD and CMV, CMV treatment.

RESULTS

Cytomegalovirus reactivation is common in patients with severe colitis, with a reported prevalence of 4.5-16.6%, and as high as 25% in patients requiring colectomy for severe colitis. The outcome for this group of patients appears worse than that for patients without reactivation; however, reported remission rates following treatment with anti-viral therapy are as high as 71-86%.

CONCLUSIONS

Evidence, although not conclusive, supports testing for CMV colonic disease in cases of moderate to severe colitis, by processing biopsies for haematoxylin and eosin staining with immunohistochemistry and/or, CMV DNA real-time polymerase chain reaction; and if present treating with ganciclovir.

Direct and Indirect Effects of Cytomegalovirus-Induced γδ T Cells after Kidney Transplantation

Despite effective anti-viral therapies, cytomegalovirus (CMV) is still associated with direct (CMV disease) and indirect effects (rejection and poor graft survival) in kidney transplant recipients. Recently, an unconventional T cell population (collectively designated as Vδ2^neg γδ T cells) has been characterized during the anti-CMV immune response in all solid-organ and bone-marrow transplant recipients, neonates, and healthy people. These CMV-induced Vδ2^neg γδ T cells undergo a dramatic and stable expansion after CMV infection, in a conventional “adaptive” manner. Similarly, as CMV-specific CD8+ αβ T cells, they exhibit an effector/memory TEMRA phenotype and cytotoxic effector functions. Activation of Vδ2^neg γδ T cells by CMV-infected cells involves the γδ T cell receptor (TCR) and still ill-defined co-stimulatory molecules such as LFA-1. A multiple of Vδ2^neg γδ TCR ligands are apparently recognized on CMV-infected cells, the first one identified being the major histocompatibility complex-related molecule endothelial protein C receptor. A singularity of CMV-induced Vδ2^neg γδ T cells is to acquire CD16 expression and to exert an antibody-dependent cell-mediated inhibition on CMV replication, which is controlled by a specific cytokine microenvironment. Beyond the well-demonstrated direct anti-CMV effect of Vδ2^neg γδ T cells, unexpected indirect effects of these cells have been also observed in the context of kidney transplantation. CMV-induced Vδ2^neg γδ T cells have been involved in surveillance of malignancy subsequent to long-term immunosuppression. Moreover, CMV-induced CD16+ γδ T cells are cell effectors of antibody-mediated rejection of kidney transplants, and represent a new physiopathological contribution to the well-known association between CMV infection and poor graft survival. All these basic and clinical studies paved the road to the development of a future γδ T cell-based immunotherapy. In the meantime, γδ T cell monitoring should prove a valuable immunological biomarker in the management of CMV infection.

Human cytomegalovirus resistance to deoxyribosylindole nucleosides maps to a transversion mutation in the terminase subunit-encoding gene UL89

Human cytomegalovirus (HCMV) infection can cause severe illnesses, including encephalopathy and mental retardation, in immunocompromised and immunologically immature patients. Current pharmacotherapies for treating systemic HCMV infections include ganciclovir, cidofovir, and foscarnet. However, long-term administration of these agents can result in serious adverse effects (myelosuppression and/or nephrotoxicity) and the development of viral strains with reduced susceptibility to drugs. The deoxyribosylindole (indole) nucleosides demonstrate a 20-fold greater activity in vitro (the drug concentration at which 50% of the number of plaques was reduced with the presence of drug compared to the number in the absence of drug [EC50] = 0.34 μM) than ganciclovir (EC50 = 7.4 μM) without any observed increase in cytotoxicity. Based on structural similarity to the benzimidazole nucleosides, we hypothesize that the indole nucleosides target the HCMV terminase, an enzyme responsible for packaging viral DNA into capsids and cleaving the DNA into genome-length units. To test this hypothesis, an indole nucleoside-resistant HCMV strain was isolated, the open reading frames of the genes that encode the viral terminase were sequenced, and a G766C mutation in exon 1 of UL89 was identified; this mutation resulted in an E256Q change in the amino acid sequence of the corresponding protein. An HCMV wild-type strain, engineered with this mutation to confirm resistance, demonstrated an 18-fold decrease in susceptibility to the indole nucleosides (EC50 = 3.1 ± 0.7 μM) compared to that of wild-type virus (EC50 = 0.17 ± 0.04 μM). Interestingly, this mutation did not confer resistance to the benzimidazole nucleosides (EC50 for wild-type HCMV = 0.25 ± 0.04 μM, EC50 for HCMV pUL89 E256Q = 0.23 ± 0.04 μM). We conclude, therefore, that the G766C mutation that results in the E256Q substitution is unique for indole nucleoside resistance and distinct from previously discovered substitutions that confer both indole and benzimidazole nucleoside resistance (D344E and A355T).

The 2010 nephrology quiz and questionnaire: part 1

Presentation of the Nephrology Quiz and Questionnaire (NQQ) has become an annual "tradition" at the meetings of the American Society of Nephrology. It is a very popular session judged by consistently large attendance. Members of the audience test their knowledge and judgment on a series of case-oriented questions prepared and discussed by experts. They can also compare their answers in real time, using audience response devices, to those of program directors of nephrology training programs in the United States, acquired through an Internet-based questionnaire. As in the past, the topics covered were transplantation, fluid and electrolyte disorders, end-stage renal disease and dialysis, and glomerular disorders. Two challenging cases representing each of these categories along with single best answer questions were prepared by a panel of experts (Drs. Hricik, Palmer, Bargman, and Fervenza, respectively). The "correct" and "incorrect" answers then were briefly discussed, after the audience responses and the results of the questionnaire were displayed. The 2010 version of the NQQ was exceptionally challenging, and the audience, for the first time, gained a better overall correct answer score than the program directors, but the margin was small. In this issue we present the transplantation and fluid and electrolyte cases; the remaining end-stage renal disease and dialysis, and glomerular disorder cases will be presented next month. These articles try to recapitulate the session and reproduce its educational value for a larger audience--the readers of the Clinical Journal of the American Society of Nephrology. Have fun.

High incidence of anticytomegalovirus drug resistance among D+R- kidney transplant recipients receiving preemptive therapy

Anti-cytomegalovirus (CMV) prophylaxis is recommended in D+R- kidney transplant recipients (KTR), but is associated with a theoretical increased risk of developing anti-CMV drug resistance. This hypothesis was retested in this study by comparing 32 D+R- KTR who received 3 months prophylaxis (valganciclovir) with 80 D+R- KTR who received preemptive treatment. The incidence of CMV infections was higher in the preemptive group than in the prophylactic group (60% vs. 34%, respectively; p = 0.02). Treatment failure (i.e. a positive DNAemia 8 weeks after the initiation of anti-CMV treatment) was more frequent in the preemptive group (31% vs. 3% in the prophylactic group; p = 0.001). Similarly, anti-CMV drug resistance (UL97 or UL54 mutations) was also more frequent in the preemptive group (16% vs. 3% in the prophylactic group; p = 0.05). Antiviral treatment failures were associated with anti-CMV drug resistance (p = 0.0001). Patients with a CMV load over 5.25 log(10) copies/mL displayed the highest risk of developing anti-CMV drug resistance (OR = 16.91, p = 0.0008). Finally, the 1-year estimated glomerular filtration rate was reduced in patients with anti-CMV drug resistance (p = 0.02). In summary, preemptive therapy in D+R- KTR with high CMV loads and antiviral treatment failure was associated with a high incidence of anti-CMV drug resistance.

First report of successful treatment of multidrug-resistant cytomegalovirus disease with the novel anti-CMV compound AIC246

We report the first case of cytomegalovirus (CMV) disease treated with AIC246, a novel anti-CMV compound which targets the viral terminase complex and remains active against virus resistant to DNA polymerase inhibitors. A lung transplant recipient developed refractory multidrug-resistant CMV disease involving the lungs, gastrointestinal tract and retina. His disease progressed despite treatment with all DNA polymerase inhibitors; multiple agents reported to have activity against CMV in case series, and reduction in his immunosuppressive medications. AIC246 which is in clinical development was obtained for emergency use, and combined with additional reduction in immunosuppression resulted in rapid clinical, virological and radiological resolution of disease. The patient has remained free of CMV disease or viremia off treatment for greater than 3 months. In summary AIC246, while still in development, may be a promising alternative to current therapies.

Oral maribavir for treatment of refractory or resistant cytomegalovirus infections in transplant recipients

BACKGROUND

Despite advances in cytomegalovirus (CMV) prophylaxis and therapy, some transplant recipients still develop refractory CMV infections. Maribavir (MBV), an investigational benzimidazole antiviral agent, acts by a mechanism different from that of existing anti-CMV drugs. Previous Phase I and II studies have demonstrated a favorable safety profile for MBV, but its utility in treatment of complex CMV syndromes is unknown.

METHODS

Between June and December 2008, MBV was released for use under individual emergency investigational new drug applications requested by treating physicians and approved by the US Food and Drug Administration and local institutional review boards. Six patients (5 solid organ transplant recipients and 1 hematopoietic stem cell transplant recipient) who had failed to respond to other therapies and/or had known ganciclovir-resistant CMV were treated with MBV at a starting oral dose of 400 mg twice daily.

RESULTS

Patients were treated for a median of 207 days (range, 15-376). Four of 6 patients had no detectable CMV DNAemia within 6 weeks of starting MBV therapy. One patient, who had an initial viral load of 1.8 million copies/mL, developed MBV resistance mutations. One patient, who had low serum levels of MBV, had persistent CMV DNAemia and viruria without developing genotypic or phenotypic resistance to MBV. One patient cleared CMV DNAemia, but died of pneumonia and multiorgan failure. No significant adverse effects attributable to MBV were observed.

CONCLUSIONS

MBV deserves further systematic evaluation as treatment for CMV infection that is resistant and/or refractory to standard therapies, but its optimal dose, duration of therapy, and use in combinations versus as a single agent have yet to be determined.

Herpesviruses: hijacking the Ras signaling pathway

Cancer is the final result of the accumulation of several genetic alterations occurring in a cell. Several herpesviruses and especially gamma-herpesviruses have played an important role in Cancer Biology, contributing significantly to our comprehension of cell signaling and growth control pathways which lead to malignancy. Unlike other infectious agents, herpesviruses persist in the host by establishing a latent infection, so that they can reactivate periodically. Interestingly, some herpesviruses are able to either deliver or induce the expression of cellular oncogenes. Such alterations can result in the derailment of the normal cell cycle and ultimately shift the balance between continuous proliferation and programmed cell death. Herpesvirus infection employs key molecules of cellular signaling cascades mostly to enhance viral replication. However, most of these molecules are also involved in essential cellular functions, such as proliferation, cellular differentiation and migration, as well as in DNA repair mechanisms. Ras proteins are key molecules that regulate a wide range of cellular functions, including differentiation, proliferation and cell survival. A broad field of medical research is currently focused on elucidating the role of ras oncogenes in human tumor initiation as well as tumor progression and metastasis. Upon activation, Ras proteins employ several downstream effector molecules such as phosphatidylinositol 3-kinase (PI3-K) and Raf and Ral guanine nucleotide-dissociation stimulators (RALGDS) to regulate a cascade of events ranging from cell proliferation and survival to apoptosis and cellular death. In this review, we give an overview of the impact that herpesvirus infection has on the host-cell Ras signaling pathway, providing an outline of their interactions with the key cascade molecules with which they associate. Several of these interactions of viral proteins with member of the Ras signaling pathway may be crucial in determining herpesviruses' oncogenic potential or their oncomodulatory behavior. The questions that emerge concern the potential role of these molecules as therapeutic targets both for viral infections and cancer. Understanding the means by which viruses may cause oncogenesis would therefore provide a deeper knowledge of the overall oncogenic process.

Resistance pattern of cytomegalovirus (CMV) after oral valganciclovir therapy in transplant recipients at high-risk for CMV infection

In transplant recipients, cytomegalovirus (CMV) resistance to antivirals causes an increasing problem. Here we report the clinical, therapeutic, and virological characteristics of 11 cases of CMV resistance among transplant recipients at high-risk for CMV infection and receiving valganciclovir as a prophylactic, preemptive or maintenance therapy. Active CMV infection was monitored by viral DNA quantification in whole blood, and CMV resistance was assessed by UL97 and UL54 viral gene sequencing. For 10 patients, ganciclovir resistance detected after valganciclovir therapy was associated with one mutation within UL97 phosphotransferase located at codons 460 and 592-603, which constitutes a similar pattern of resistance to what has been reported previously in AIDS patients treated with valganciclovir. For the last patient, two mutations in UL97 and UL54 genes were identified. The start of valganciclovir maintenance treatment after an intravenous curative treatment while CMV DNA is still detectable in peripheral blood might represent a risk factor for the emergence of CMV resistance. The possible emergence of CMV resistance in transplant recipients at high-risk for CMV infection who receive valganciclovir therapy should be taken into account. Among those patients, CMV infection has to be closely monitored in order to detect promptly the emergence of drug-resistance.

Viral infection after renal transplantation: surveillance and management

Viral infections remain a significant cause of morbidity and mortality following renal transplantation. Although cytomegalovirus is the most common opportunistic pathogen seen in transplant recipients, numerous other viruses have also affected outcomes. In some cases, preventive measures such as pretransplant screening, prophylactic antiviral therapy, or post transplant viral monitoring may limit the impact of these infections. Recent advances in laboratory monitoring and antiviral therapy have improved outcomes. This review will summarize the major viral infections seen following transplant and discuss strategies for prevention and management of these potential pathogens.

Antimicrobial resistance prevention initiative--an update: proceedings of an expert panel on resistance

Antimicrobial resistance is a growing problem that complicates the treatment of important nosocomial and community-acquired infections. It is a worldwide problem that spans the range of human pathogens, including bacteria, fungi, and viruses. This update from the Antimicrobial Resistance Prevention Initiative (ARPI) provides a review of some important trends in antibiotic, antifungal, and antiviral resistance. Areas of focus include multidrug-resistant bacteria in the hospital setting; the growing problem of community-acquired methicillin-resistant Staphylococcus aureus; triazole and polyene resistance in nosocomial infections caused by non-Candida albicans or Aspergillus species, and the utility of in vitro susceptibility testing for these fungal infections; antiviral resistance in alpha- or beta-herpesviruses causing genital herpes or cytomegalovirus infection in immunocompromised hosts; and concerns about a possible pandemic involving avian influenza A and the importance of minimizing emergence of resistant strains of this highly pathogenic virus. The challenges in each area are different, but the general keys to addressing the growing problem of antimicrobial resistance continue to be responsible antimicrobial stewardship and the development of newer antimicrobial agents.

Antimicrobial resistance prevention initiative--an update: proceedings of an expert panel on resistance

Antimicrobial resistance is a growing problem that complicates the treatment of important nosocomial and community-acquired infections. It is a worldwide problem that spans the range of human pathogens, including bacteria, fungi, and viruses. This update from the Antimicrobial Resistance Prevention Initiative (ARPI) provides a review of some important trends in antibiotic, antifungal, and antiviral resistance. Areas of focus include multidrug-resistant bacteria in the hospital setting; the growing problem of community-acquired methicillin-resistant Staphylococcus aureus; triazole and polyene resistance in nosocomial infections caused by non-Candida albicans or Aspergillus species, and the utility of in vitro susceptibility testing for these fungal infections; antiviral resistance in alpha- or beta-herpesviruses causing genital herpes or cytomegalovirus infection in immunocompromised hosts; and concerns about a possible pandemic involving avian influenza A and the importance of minimizing emergence of resistant strains of this highly pathogenic virus. The challenges in each area are different, but the general keys to addressing the growing problem of antimicrobial resistance continue to be responsible antimicrobial stewardship and the development of newer antimicrobial agents.

Novel real-time monitoring system for human cytomegalovirus-infected cells in vitro that uses a green fluorescent protein-PML-expressing cell line

Promyelocytic leukemia (PML) bodies are discrete nuclear foci that are intimately associated with many DNA viruses. In human cytomegalovirus (HCMV) infection, the IE1 (for "immediate-early 1") protein has a marked effect on PML bodies via de-SUMOylation of PML protein. Here, we report a novel real-time monitoring system for HCMV-infected cells using a newly established cell line (SE/15) that stably expresses green fluorescent protein (GFP)-PML protein. In SE/15 cells, HCMV infection causes specific and efficient dispersion of GFP-PML bodies in an IE1-dependent manner, allowing the infected cells to be monitored by fluorescence microscopy without immunostaining. Since a specific change in the detergent solubility of GFP-PML occurs upon infection, the infected cells can be quantified by GFP fluorescence measurement after extraction. With this assay, the inhibitory effects of heparin and neutralizing antibodies were determined in small-scale cultures, indicating its usefulness for screening inhibitory reagents for laboratory virus strains. Furthermore, we established a sensitive imaging assay by counting the number of nuclei containing dispersed GFP-PML, which is applicable for titration of slow-growing clinical isolates. In all strains tested, the virus titers estimated by the GFP-PML imaging assay were well correlated with the plaque-forming cell numbers determined in human embryonic lung cells. Coculture of SE/15 cells and HCMV-infected fibroblasts permitted a rapid and reliable method for estimating the 50% inhibitory concentration values of drugs for clinical isolates in susceptibility testing. Taken together, these results demonstrate the development of a rapid, sensitive, quantitative, and specific detection system for HCMV-infected cells involving a simple procedure that can be used for titration of low-titer clinical isolates.

The emergence of cytomegalovirus resistance to ganciclovir therapy in kidney transplant recipients

Transplant recipients that have not been previously exposed to the cytomegalovirus (CMV) are highly susceptible to viral diseases while under immunosuppression therapy. CMV disease requires prolonged therapy, facilitating the emergence of resistant strains. Persistence of positive antigenemia represents clinical evidence of the presence of resistant strains, although its frequency is unknown. These strains may present amino acid deletions or substitutions in conserved regions of the UL97 protein, point mutations in the DNA polymerase (UL54), or both. In this study we aimed to analyze the prevalence of mutations associated with ganciclovir resistance in transplant recipients. Fifteen kidney transplant recipients and four kidney-pancreas transplant recipients, with a positive and oscillating CMV viremia detected by sequential antigenemia test, were enrolled. The UL97 gene was amplified by Nested-PCR and enzymatically digested in samples of these patients in order to detect mutations in the most common codons, such as 460 (M460V), 594 (A594V) and 595(L595S/F). The end-product fragments were further sequenced. Nine (47.4%) out of 19 patients presented with mutations in UL97 at codons L595S (55.6%), A594V (11.1%), A595F/A594V (11.1%) and L595S/A594V (22.2%). None presented with mutation at the M460V codon. Renal transplant patients with oscillation in viral load for more than 2 weeks might have developed viral resistance to anti-drug therapy. Its detection might aid physicians in their clinical plan of tapering the patient's immunosuppression.

Anti-cytomegalovirus prophylaxis in solid-organ transplant recipients

Ganciclovir and its prodrug, valganciclovir, are more effective than acyclovir in preventing cytomegalovirus (CMV) infection and disease in solid-organ transplant recipients. However, the indirect effects of prophylactic use of ganciclovir and acyclovir are comparable, and the greater effectiveness of ganciclovir may be compensated for by less drug-related toxicity with acyclovir or valacyclovir. No conclusive data exist concerning the best technique and duration of surveillance for CMV infection in patients for whom active surveillance for late-onset CMV should be performed, i.e., those reaching the end of prophylaxis. Only large randomised controlled trials, with long follow-up periods, will provide definitive conclusions regarding the comparative prophylactic roles of the major antiviral agents in this population, and how their use fits with a strategy of active surveillance and pre-emptive therapy.

Utility of direct fluorescent antibody testing of nasopharyngeal washes in children with and without respiratory tract illness

BACKGROUND

Direct fluorescent antibody (DFA) testing of nasopharyngeal wash specimens is a rapid and reliable means of diagnosing respiratory viral infection. The utility of DFA testing in the evaluation of febrile children without respiratory symptoms has not been critically evaluated. It is not known whether clinical or demographic factors apart from respiratory symptoms are associated with a positive DFA or whether a positive DFA is more likely to be associated with lower or upper respiratory tract symptoms (RTS).

METHODS

This is a retrospective case-series of 756 consecutive nasopharyngeal specimens with respiratory DFA testing performed at the University of California San Francisco from November 1, 2002 through October 31, 2003.

RESULTS

No RTS was a statistically significant predictor of negative DFA [odds ratio (OR), 0.03; 95% confidence interval (CI), 0.004-0.2; P = 0.001] compared with lower RTS. Male subjects were more likely than female subjects to have a positive DFA (OR 1.8; 95% CI 1.1-2.8; P = 0.02). Specimens collected from April to October were less likely to have a positive DFA (OR 0.4; 95% CI 0.2-0.7; P = 0.001). Specimens collected at the time of hospital admission and during a hospitalization were less likely to have a positive DFA (OR 0.5; 95% CI 0.3-0.9; P = 0.01 and OR, 0.07; 95% CI 0.02-0.2; P = 0.001, respectively) compared with specimens collected in the outpatient setting.

CONCLUSION

The yield of testing children without respiratory tract illness is extremely low.

Role of helix P of the human cytomegalovirus DNA polymerase in resistance and hypersusceptibility to the antiviral drug foscarnet

Mutations in the human cytomegalovirus DNA polymerase (UL54) can not only decrease but also increase susceptibility to the pyrophosphate (PP(i)) analogue foscarnet. The proximity of L802M, which confers resistance, and K805Q, which confers hypersusceptibility, suggests a possible unifying mechanism that affects drug susceptibility in one direction or the other. We found that the polymerase activities of L802M- and K805Q-containing mutant enzymes were literally indistinguishable from that of wild-type UL54; however, susceptibility to foscarnet was decreased or increased, respectively. A comparison with the crystal structure model of the related RB69 polymerase suggests that L802 and K805 are located in the conserved alpha-helix P that is implicated in nucleotide binding. Although L802 and K805 do not appear to make direct contacts with the incoming nucleotide, it is conceivable that changes at these residues could exert their effects through the adjacent, highly conserved amino acids Q807 and/or K811. Our data show that a K811A substitution in UL54 causes reductions in rates of nucleotide incorporation. The activity of the Q807A mutant is only marginally affected, while this enzyme shows relatively high levels of resistance to foscarnet. Based on these data, we suggest that L802M exerts its effects through subtle structural changes in alpha-helix P that affect the precise positioning of Q807 and, in turn, its presumptive involvement in binding of foscarnet. In contrast, the removal of a positive charge associated with the K805Q change may facilitate access or increase affinity to the adjacent Q807.

Cytomegalovirus Pneumonia in Transplant Recipients

The incidence of cytomegalovirus CMV pneumonia has been reduced by routine antiviral prophylaxis in susceptible populations. Many of the complications of this infection are caused by indirect effects of the virus, including acute and chronic graft rejection, graft-versus-host disease, and superinfection by other viruses, bacteria and fungi. Distinction must be made between viral secretion and invasion. Invasive procedures are often required for the optimal management of such infections. The use of sensitive and quantitative assays have greatly improved the outcomes of CMV infection.

Use of leflunomide in an allogeneic bone marrow transplant recipient with refractory cytomegalovirus infection

Ganciclovir-resistant cytomegalovirus (CMV) infection is an emerging problem in transplant recipients. Foscarnet resistance and cidofovir resistance have also been described, but no previous reports have suggested treatment regimens for patients with CMV refractory to all three of these drugs. Leflunomide, an immunosuppressive drug used in rheumatoid arthritis and in rejection in solid-organ transplantation, has been reported to have novel anti-CMV activity. However, its clinical utility in CMV treatment has not been described previously. We report an allogeneic bone marrow transplant recipient who developed CMV infection refractory to sequential therapy with ganciclovir, foscarnet, and cidofovir. The patient was ultimately treated with a combination of leflunomide and foscarnet. Both phenotypic and genotypic virologic analysis was performed on sequential CMV isolates. The patient's high CMV-DNA viral load became undetectable on leflunomide and foscarnet, but the patient, who had severe graft-versus-host disease (GVHD) of the liver, expired with progressive liver failure and other complications. We concluded that leflunomide is a new immunosuppressive agent with anti-CMV activity, which may be useful in the treatment of multiresistant CMV. However, the toxicity profile of leflunomide in patients with underlying GVHD remains to be defined.

Update on human herpesvirus 6 biology, clinical features, and therapy

Human herpesvirus 6 (HHV-6) is a betaherpesvirus that is closely related to human cytomegalovirus. It was discovered in 1986, and HHV-6 literature has expanded considerably in the past 10 years. We here present an up-to-date and complete overview of the recent developments concerning HHV-6 biological features, clinical associations, and therapeutic approaches. HHV-6 gene expression regulation and gene products have been systematically characterized, and the multiple interactions between HHV-6 and the host immune system have been explored. Moreover, the discovery of the cellular receptor for HHV-6, CD46, has shed a new light on HHV-6 cell tropism. Furthermore, the in vitro interactions between HHV-6 and other viruses, particularly human immunodeficiency virus, and their relevance for the in vivo situation are discussed, as well as the transactivating capacities of several HHV-6 proteins. The insight into the clinical spectrum of HHV-6 is still evolving and, apart from being recognized as a major pathogen in transplant recipients (as exemplified by the rising number of prospective clinical studies), its role in central nervous system disease has become increasingly apparent. Finally, we present an overview of therapeutic options for HHV-6 therapy (including modes of action and resistance mechanisms).

Pre-emptive treatment with oral valganciclovir in management of CMV infection after cardiac transplantation

BACKGROUND

Cytomegalovirus (CMV) has long been recognized as the most common opportunistic pathogen in transplant recipients. The use of post-detection antiviral treatment of CMV as a strategy to prevent disease in cardiac recipients is becoming the standard policy. Valganciclovir is an oral pro-drug of ganciclovir, with a 10-fold greater bioavailability than oral gancyclovir.

PATIENTS AND METHODS

We reported our first experience with 8 patients (3 female, 45.0 +/- 10.5 years old, non-CMV mismatched) who underwent cardiac transplantation and had positive results of CMV polymerase chain reaction (PCR) within first 6 weeks after transplantation without concomitant CMV disease. These patients received valganciclovir in dosage 450 to 900 mg daily depending on renal function for 3 weeks. Standard immunosuppressive regimen consisted of cyclosporin A, MMF and corticosteroids, and was not changed after detection of CMV infection. In one patient we used sirolimus with respectively reduced dosage of cyclosporin A. Weekly measurements of CMV-PCR were performed to observe results of therapy.

RESULTS

After 1 week of valganciclovir therapy CMV-PCR plasma concentration in all patients decreased significantly (2,105 copies/ml vs 400 copies/ml; p < 0.0001). No relapse of CMV infection has been detected after completing of valganciclovir therapy with follow up duration of 9.0 +/- 0.92 months. The drug was generally well tolerated, and we did not observe any severe drug related adverse events.

CONCLUSION

Oral valganciclovir as pre-emptive antiviral therapy administrated after detection of CMV infection seems to be an effective and safe treatment in cardiac transplant recipients.

Mechanism of action of the ribopyranoside benzimidazole GW275175X against human cytomegalovirus

New human cytomegalovirus (HCMV) therapies with novel mechanisms of action are needed to treat drug-resistant HCMV that arises during therapy with currently approved agents. 2-Bromo-5,6-dichloro-1-beta-D-ribofuranosyl-1H-benzimidazole (BDCRB) is an effective anti-HCMV agent with a novel mechanism of action, but problems with in vivo stability preclude clinical development. A D-ribopyranosyl derivative of BDCRB, GW275175X, displays similar antiviral activity without the in vivo stability problems. We present an initial description of the activity of GW275175X against HCMV, other herpesviruses, and selected nonherpesviruses. In addition, we show that it acts as a DNA maturation inhibitor like the parent compound, BDCRB, rather than via the mechanisms of action of 1263W94 or any anti-HCMV drugs approved for marketing. GW275175X is a promising candidate for clinical development as an anti-HCMV agent.

The influence of mixed HCMV UL97 wildtype and mutant strains on ganciclovir susceptibility in a cell associated plaque reduction assay

BACKGROUND

Ganciclovir (GCV) resistance is an emerging problem following organ transplantation. A restriction fragment length polymorphism (RFLP) assay is a convenient and rapid method to discover known resistance mutations within the UL97 (phosphotransferase) gene for the determination of GCV resistance. Phenotypic resistance testing remains important for the identification of human cytomegalovirus (HCMV) strains possibly harboring novel mutations and also for the determination of foscarnet and cidofovir resistance.

OBJECTIVE

The aim of this work was to evaluate the reliability of a cell-associated plaque reduction assay with respect to an expanded UL97 RFLP assay for use on codons 460, 520, 591, 592, 594, 595 and 603. Furthermore, the influence of mixed viral populations with coexistent wildtype and mutant UL97 sequences on GCV IC(50) values was investigated.

STUDY DESIGN

Twenty-eight clinical HCMV isolates were obtained from six adult patients under clinical and virological suspicion for development of GCV resistance following peripheral blood stem cell transplantation (PBSCT), and from one adult and three pediatric patients with confirmed GCV resistance following PBSCT. All isolates were tested for drug susceptibility and screened for UL97 resistance mutations.

RESULTS

The plaque reduction assay exceeded the GCV cut-off for resistance even when only a small number (5-10%) of the viral population was resistant. The proportion of UL97 mutant and wildtype strains influenced GCV IC(50) values. Genotypically detected GCV resistance always preceded phenotypically detected resistance. Long-term follow-up UL97 resistance screening revealed evidence for transient and compartment-specific UL97 mutations.

CONCLUSION

The stringent and longitudinal use of an expanded HCMV UL97 RFLP assay of specimens from different sites contributes to the rapid and reliable diagnosis of GCV resistance. The influence of the proportion of UL97 mutant and wildtype strains on GCV IC(50) values along with the strong correlation between phenotype and genotype suggests that the cell associated plaque reduction assay is highly reliable.

Specific inhibition of human cytomegalovirus glycoprotein B-mediated fusion by a novel thiourea small molecule

A novel small molecule inhibitor of human cytomegalovirus (HCMV) was identified as the result of screening a chemical library by using a whole-virus infected-cell assay. Synthetic chemistry efforts yielded the analog designated CFI02, a compound whose potency had been increased about 100-fold over an initial inhibitor. The inhibitory concentration of CFI02 in various assays is in the low nanomolar range. CFI02 is a selective and potent inhibitor of HCMV; it has no activity against other CMVs, alphaherpesviruses, or unrelated viruses. Mechanism-of-action studies indicate that CFI02 acts very early in the replication cycle, inhibiting virion envelope fusion with the cell plasma membrane. Mutants resistant to CFI02 have mutations in the abundant virion envelope glycoprotein B that are sufficient to confer resistance. Taken together, the data suggest that CFI02 inhibits glycoprotein B-mediated HCMV virion fusion. Furthermore, CFI02 inhibits the cell-cell spread of HCMV. This is the first study of a potent and selective small molecule inhibitor of CMV fusion and cell-cell spread.

Reduced efficacy of ganciclovir against porcine and baboon cytomegalovirus in pig-to-baboon xenotransplantation

In pig-to-baboon xenotransplantation, porcine cytomegalovirus (PCMV) causes viremia, consumptive coagulopathy, and tissue-invasive disease. Baboon cytomegalovirus (BCMV) is associated with invasive disease in xenograft recipients. The efficacy of prophylaxis with intravenous ganciclovir (GCV) was studied for prevention of PCMV and BCMV infections in pig-to baboon xenotransplantation. GCV prophylaxis did not alter the incidence of BCMV activation in recipients, but reduced the amount of virus in tissues (mean 8.38 x 10(2) vs. 3.24 x 10(5) copies/ micro g DNA without treatment) and prevented tissue-invasive infections. PCMV viral loads were unaltered by GCV prophylaxis (8.36 x 10(8) copies/ micro g DNA without prophylaxis vs. 1.20 x 10(9) copies/ micro g DNA with prophylaxis). In vitro, PCMV was relatively resistant to GCV [90% inhibitory concentration (IC90) of 10 micro m, IC50 = 3 micro m], acyclovir (100 micro m), and leflunomide (not achievable). Only cidofovir (IC90 1 micro m) and foscarnet (IC90 100 micro m) might have therapeutic efficacy for PCMV in vivo in achievable concentrations, although these agents often carry significant toxicity in transplant recipients. GCV has limited activity against BCMV and no therapeutic efficacy against PCMV at standard doses in vivo. GCV and other antiviral agents have limited activities against PCMV in vitro. Breeding of PCMV-free xenograft donors may be necessary to prevent PCMV infections in clinical trials.

Gastrointestinal Infections Caused by Cytomegalovirus

Cytomegalovirus (CMV) is an important human pathogen, causing a variety of syndromes ranging from asymptomatic infections to life-threatening end-organ disease. Infections of the gastrointestinal tract are an especially common form of disease caused by CMV and are usually manifest as luminal infections, such as esophagitis or colitis. Solid organ disease caused by CMV is also known to occur, with hepatitis being the most common syndrome. The large majority of cases of tissue-invasive disease caused by CMV have been reported to occur in immunocompromised hosts. Patients at highest risk for serious CMV-mediated disease are commonly HIV infected, recipients of transplants, or are receiving potent immunosuppressive medications. Intriguingly, several recent reports have discussed the previously underappreciated role of serious forms of CMV-mediated disease occurring in immunocompetent patients. This paper reviews several recent reports addressing important aspects related to the diagnosis, treatment, and management of CMV infections of the gastrointestinal tract.

Clinical characteristics of 13 solid organ transplant recipients with ganciclovir-resistant cytomegalovirus infection

BACKGROUND

Ganciclovir-resistant (GCV-R) cytomegalovirus (CMV) is now being reported with increasing frequency in solid organ transplant recipients.

OBJECTIVE

To describe the clinical characteristics and outcomes of all solid organ transplant patients with GCV-R CMV seen between 1990 and 2000 at a single center.

METHODS

Patients with clinically suspected GCV resistance had viral isolates subjected to phenotypic analysis by plaque reduction assay, and also genotypic analysis. Medical records of the 13 patients with GCV-R CMV were reviewed for demographic, microbiologic, clinical, and pathologic data.

RESULTS

Thirteen patients were identified, including 5 kidney, 1 heart, and 7 lung transplant recipients. All but one patient (92%) were CMV donor seropositive, recipient negative (D+/R-), and 11/13 (85%) had tissue-invasive CMV. CMV viremia was recurrent in 9/13 (69%); in 2 others, the first CMV episode was fatal. Overall, 9/13 (69%) of patients have died, all of CMV or its complications. Of the 10 who received foscarnet, only one survived. All patients had received GCV-based prophylactic regimens; 8/13 patients (62%) had received CMV hyperimmune globulin (CMVIG) as part of prophylaxis, 6/13 (46%) had received oral ganciclovir, and 5/13 (38%) had received intermittent (3 x/week) IV ganciclovir for prophylaxis.

CONCLUSIONS

GCV-R CMV is associated with CMV D+/R- status, tissue-invasive disease, and high mortality even with foscarnet therapy. Exposure to less than fully therapeutic levels of GCV, in the form of oral or intermittent IV GCV, is common. The use of CMVIG in prophylaxis does not appear to prevent resistance. Further work remains to be done to elucidate the risk factors and optimal mode of prophylaxis and treatment for GCV-R CMV.

Intravenous Cidofovir therapy for disseminated adenovirus in a pediatric liver transplant recipient

BACKGROUND

No definitive antiviral therapy exists for adenovirus (ADV) in immunosuppressed hosts. Cidofovir (CDV), a broad spectrum anti-DNA viral agent, has previously been shown to be of therapeutic benefit in life-threatening adenoviral disease in bone marrow stem-cell recipients.

METHODS

A 71/2-month-old girl with a history of biliary atresia developed fevers, hematochezia, tachypnea, and laboratory evidence of hepatitis and pancreatitis 12 days after liver transplantation. A stool culture, oropharyngeal culture, blood viral culture, and blood polymerase chain reaction (PCR) confirmed ADV. Cidofovir 1 mg/kg intravenously three times per week was initiated. The patient received intravenous hydration and probenecid with the infusions to reduce the nephrotoxicity of CDV. Immunosuppression was reduced to achieve tacrolimus trough levels of approximately 8 ng/mL and prednisone at 0.1 mg/kg per day. Complete blood cell count, urinalysis, and viral studies were obtained weekly.

RESULTS

Detection of ADV DNA by PCR made a transition from positive to negative during CDV therapy. Blood viral cultures became negative after two CDV doses. Alanine aminotransferase normalized by 5 weeks of therapy. CDV was discontinued after 7 weeks secondary to transient acidosis and proteinuria. The patient never developed azotemia, neutropenia, or ocular abnormalities.

CONCLUSIONS

CDV was associated with improved clinical status, viral clearance, and minimal transient side effects in a pediatric liver transplant recipient with disseminated adenoviral disease. The current report documents clearance of disseminated ADV infection in a liver transplant recipient receiving CDV infusions.

Combination antiviral therapy for ganciclovir-resistant cytomegalovirus infection in solid-organ transplant recipients

The resistance of cytomegalovirus (CMV) to ganciclovir is a factor in therapeutic failure and disease progression. The clinical significance of such resistance in solid-organ transplantation has not been completely established. Six patients who developed persistent infection due to ganciclovir-resistant CMV were treated with a combination of ganciclovir (50% of the therapeutic dose) and a daily dose of intravenous foscarnet that gradually increased to a maximum of 125 mg/kg. All patients responded clinically within 72-96 hours. Magnesium depletion occurred in all patients. No clinical or laboratory relapses have been observed in 6-30 months of follow-up. Gradually increasing doses of foscarnet combined with half-dose regimens of ganciclovir are safe and can be beneficial in organ transplant recipients with ganciclovir-resistant CMV infection. Larger studies are needed to identify the patients who are most likely to benefit from this regimen.