Ganciclovir resistance as a result of oral ganciclovir in a heart transplant recipient with multiple human cytomegalovirus strains in blood

Single and multiple mutations in the human cytomegalovirus UL97 gene and their relationship to the enzymatic activity of UL97 kinase for ganciclovir phosphorylation

In this study we determined that the double mutant M460V/D605E in the UL97 gene of an HCMV isolate from an immunocompromised patient (MMT isolate) is related to resistance to ganciclovir (GCV) therapy. Our results suggest that the aspartic acid-to-glutamic acid substitution at codon 605 may be associated with a natural polymorphism of the UL97 gene, and not with positive selection pressure exerted by the antiviral drug. We also determined that GCV resistance due to the M460V mutation in the HCMV UL97 gene is not offset by a second mutation (D605E) at codon 605. Furthermore, we showed that when the two mutations related to GCV resistance were simultaneously detected in the same HCMV construct, virus-drug resistance might be enhanced in comparison to that of the single mutants studied separately. To our knowledge for the first time, seven of 12 amino acid changes (F102L, D118V, M330T, T400A, R507P and C511R and I533V) in the UL97 gene of an isolate are herein reported.

Viral monitoring and successful treatment of a ganciclovir-resistant cytomegalovirus infection in a heart transplant recipient

We reported a ganciclovir (GCV)-resistant cytomegalovirus (CMV) infection in a heart transplant recipient. Genotypic and phenotypic susceptibility assays demonstrated an A594V mutation in the UL97 phosphotransferase gene and GCV IC(50)>96 microM. Low GCV concentration exposure, immunosuppressive treatment, donor-positive/recipient-negative CMV serostatus, viral reactivations within antiviral prophylaxis or treatment, contributed to GCV-resistant strain selection.

Monitoring human cytomegalovirus infection in transplant recipients

Human cytomegalovirus (HCMV) infection remains one of the most challenging infectious complications in both solid organ transplant (SOT) and hemopoietic stem cell transplant (HSCT) recipients. In the last two decades advances have been made in the diagnosis and monitoring of HCMV infection in SOT and HSCT recipients following introduction of quantitative assays such as rapid virus isolation in blood (viremia), quantitation of pp65 in peripheral blood leukocytes (antigenemia), and quantitation of viral genome in blood (DNAemia). The availability of these rapid diagnostic assays has allowed treatment administration during the presymptomatic phase of HCMV infection (preemptive treatment) and greatly reduced HCMV-related morbidity and mortality, particularly among HSCT recipients. Definition of clinically validated thresholds for initiating preemptive treatment in SOT and HSCT recipients is a major goal in the transplantation setting. With respect to universal prophylaxis of HCMV infection in transplant recipients, the preemptive treatment approach shows advantages in (i) treating a lower number of patients for shorter periods of time and (ii) avoiding the reported emergence of HCMV disease after interruption of anti-HCMV prophylaxis. To understand the mechanism behind long-term control of HCMV infection in transplant recipients, the HCMV-specific T-cell response must be evaluated.

Modulation of Ganciclovir Intestinal Absorption in Presence of Absorption Enhancers

The purpose of this investigation was to study the influences of absorption enhancers in increasing oral bioavailability of Ganciclovir (GAN) by assessing the transepithelial permeation across cell monolayers in vitro and bioavailability in rats in vivo. The permeation of GAN across Caco-2 and MDCK cell monolayers in the absence/presence of dimethyl-beta-cyclodextrin (DMbetaCD), chitosan hydrochloride (CH), sodium lauryl sulphate (SLS), and their combinations was studied for a 2-h period. GAN was administered to rats in absence/presence of absorption enhancers and drug contents in plasma were estimated. We found that the apparent permeability coefficient (Papp) of GAN in absence of absorption enhancers (control) were 0.261 +/- 0.072 x 10(-6) and 0.486 +/- 0.063 x 10(-6) cm/s in Caco-2 and MDCK cell monolayers, respectively, whereas in the presence of DMbetaCD, CH, SLS, and their combinations, Papp of GAN increased by 5- to 25-fold and 7- to 33-fold as compared to control in Caco-2 and MDCK cell monolayers, respectively. However, in rats, the maximum enhancement in bioavailability of GAN during coadministration of these absorption enhancers was only fivefold compared to GAN control. To conclude, the absorption enhancers-DMbetaCD, CH, SLS, and their combinations demonstrated significant improvement in transepithelial permeation and bioavailability of GAN.

Rapid simultaneous detection by real-time PCR of cytomegalovirus UL97 mutations in codons 460 and 520 conferring ganciclovir resistance

Ganciclovir (GCV) resistance is an emerging problem for transplant recipients. A sensitive and rapid real-time PCR approach for simultaneous and semiquantitative detection of human cytomegalovirus (HCMV) UL97 mutations in codons 460/520 was established by LightCycler and confirmed by restriction fragment length polymorphism and sequencing. Results from HCMV laboratory strains were compared with results from 11 GCV-resistant clinical isolates.

Use of time-saving flow cytometry for rapid determination of resistance of human cytomegalovirus to ganciclovir

There are two ways to assess the susceptibility of human cytomegalovirus (HCMV) to ganciclovir (GCV): one is a genotypic test that detects resistance-related mutations and the other is a phenotypic test that actually assesses susceptibility. The advantages of genotyping the UL 97 gene are its rapidity and accuracy. However, to detect novel mutations or mutations affecting the UL 54 DNA polymerase, a phenotypic test such as the plaque reduction assay (PRA) is also required. To avoid the shortcomings of PRA such as its time-consuming nature and labor-intensiveness, we developed a time-saving fluorescence-activated cell sorting (TS-FACS) technique. We obtained a GCV 50% inhibitory concentration (IC(50)) from five clinical isolates and an HCMV laboratory strain (AD169) and compared the results with those from the PRA. The laboratory strain and three clinical isolates were sensitive to GCV. Although there was a minor discrepancy in the case of one of the three isolates, the GCV IC(50) values obtained by TS-FACS analysis correlated well with the results of the PRA. The remaining two isolates were resistant to GCV; one was GCV resistant due to the mutation M 460 V, and the GCV IC(50) results obtained by TS-FACS analysis and by PRA were also comparable. The advantages of TS-FACS analysis are the shorter time required, the possibility of automation, and its comparability to PRA, considered the gold standard. Thus, TS-FACS analysis may be useful as an alternative to PRA in the clinic.

A comparative randomised study of valacyclovir vs. oral ganciclovir for cytomegalovirus prophylaxis in renal transplant recipients

An open, prospective, randomised study was conducted to compare the safety and efficacy of valacyclovir vs. oral ganciclovir for cytomegalovirus (CMV) prophylaxis in renal transplant recipients. Eighty-three renal transplant recipients were assigned randomly to receive valacyclovir (n=43) or oral ganciclovir (n=40) for the first 3 months after transplantation. Both groups were similar in terms of demographics, primary renal disease, graft source, HLA matching, immunosuppressive therapy and donor-recipient CMV antibody status. CMV infection was diagnosed by detection of virus DNA in plasma with the Amplicor CMV Test. CMV disease was observed in only one patient belonging to the ganciclovir group, who developed enterocolitis 6 months post-transplantation. No difference was observed between the two treatment groups with respect to detection of CMV DNA, virus infections other than CMV, acute rejection episodes, and serum creatinine levels at 3 and 6 months following transplantation. An increased number of bacterial infections was noted in the ganciclovir group (p 0.003). No adverse reactions with either treatment were reported. The estimated cost of valacyclovir treatment was 20% higher than that of ganciclovir treatment. Overall, both valacyclovir and oral ganciclovir were found to be effective and safe for CMV prophylaxis in renal transplant recipients. Decisions regarding prophylactic regimens should include additional criteria, such as cost or possible development of resistance.

Influence of Ganciclovir Prophylaxis on Citomegalovirus, Human Herpesvirus 6, and Human Herpesvirus 7 Viremia in Renal Transplant Recipients

In order to know the influence of ganciclovir (GCV) prophylaxis on cytomegalovirus (CMV) human herpesvirus (HHV)-6 and HHV-7 replication in renal transplant recipients, three groups were studies: 54 patients without GCV; 29, with short-term GCV prophylaxis (less than 30 days); and 51, with long-term GCV prophylaxis (more than 60 days). CMV viremia was more prevalent in the first group (74%, 55%, and 29%, respectively), but CMV replication was also found in 14 patients during therapy, in the other two groups. The antiviral did not affect the prevalence of HHV-6 (67.2%) or HHV-7 (76%), but HHV-6 viremia appeared later (42 +/- 31 vs 21 +/- 25/38 +/- 29 days posttransplant) and was shorter (29 +/- 30 vs 62 +/- 34/41 +/- 33 days) among patients with long-term GCV prophylaxis. On the other hand, CMV viremia was longer when HHV-6 replication was present (40 +/- 25 days vs 18 +/- 16 days). In addition, HHV-7 DNA was detected in all patients with CMV disease.

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.

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.

Cytomegalovirus and lung transplantation

Cytomegalovirus (CMV) infection remains a serious problem in lung transplant recipients. Development of potent oral antiviral agents, molecular techniques for the detection of infection and its response to therapy and the emergence of isolates with antiviral resistance have had significant impacts on the approach to CMV in these patients. This article discusses the following issues as part of a comprehensive CMV management strategy in lung transplant recipients: (1) Prevention strategies in the era of potent oral antiviral agents, (2) the role of new diagnostic techniques in the management of CMV, (3) treatment regimens for established CMV infection or disease, (4) the potential impact of treatment of CMV on the indirect effects on long-term allograft function, and (5) the incidence, risk factors for and impact of ganciclovir resistance following lung transplantation.

[Viral pneumonia in immunocompetent patients]

Les infections virales respiratoires communautaires sont fréquentes et le plus souvent bénignes. Beaucoup d'agents différents comme les virus influenza, ou para-influenza, le virus respiratoire syncitial, les rhinovirus, coronavirus, adénovirus et les herpès virus peuvent être isolés chez les patients immunocompétents. Parmi ces virus, le cytomégalovirus (CMV) peut être responsable de pneumonie nosocomiale en réanimation. Le diagnostic des infections virales est difficile car les signes cliniques sont non spécifiques et l'isolement du virus responsable difficile. Cependant, une symptomatologie clinique associant fièvre, myalgies, céphalées, pharyngite est fréquente dans les infections à Inflenza qui peuvent aboutir à des tableaux sévères. Enfin, le virus plus récent responsable d'infection respiratoire est un virus nouvellement découvert de la famille des coronavirus, le SRAS-CoV qui a été responsable d'une épidémie d'infections respiratoires sévères. Les pneumonies virales sont fréquentes mais probablement non diagnostiquées chez les patients immunocompétents. Cependant le diagnostic est nécessaire car pour la plupart des pathogènes il existe un traitement efficace. Le diagnostic repose sur l'histologie mais de nouvelles techniques comme la PCR doivent devenir d'utilisation courante pour améliorer le rendement diagnostique.

Clinical and biologic aspects of human cytomegalovirus resistance to antiviral drugs

The emergence of human cytomegalovirus (HCMV) drug resistant strains is a life-threatening condition in immunocompromised individuals with active HCMV infection. HCMV drug resistance represented a major problem in patients with acquired immunodeficiency syndrome until the recent introduction of highly active antiretroviral combination therapy, which dramatically decreased the incidence in this clinical setting. However, HCMV resistance to antiviral drugs is now an emerging problem in the transplantation setting. The molecular mechanisms of HCMV drug resistance have been elucidated and rely on the selection during treatment of HCMV strains harboring mutations in two key viral genes: UL97 coding for a viral phosphotransferase and UL54 coding for the viral DNA polymerase.

Efficacy and limitations of preemptive therapy against cytomegalovirus infections in heart transplant patients

OBJECTIVES

Cytomegalovirus (CMV) disease often represents a serious complication that promotes opportunistic infections in heart transplant recipients. In this study we evaluated the impact of preemptive gancylovir therapy, guided by pp65 antigenemia on the morbidity associated with viral reactivation.

PATIENTS AND METHODS

We have performed a CMV infection surveillance program since March 1999, with antigenemia pp65 determinations weekly for the first 2 months biweekly in the third months, and monthly to the sixth month. Patients with pp65 antigenemia value >/= 10 positive cells per 2 x 10(5) polymorphonuclear cells (PMN) were treated with intravenous gancyclovir followed by 1 month of oral gancyclovir.

RESULTS

Among the 107 patients who underwent the virological monitoring, 80 were pp65 antigenemia-positive with preemptive therapy administered in 48 cases. Five patients displayed symptomatic CMV disease (4.7% vs 18% rate in the period of 1988 to 1998 before the introduction of virologic monitoring; P <.01). We observed only one case of gancyclovir-resistant pneumonia which was successfully treated with foscarnet. CMV recurrence in 10 patients required a second cycle of gancyclovir treatment. Our experience included 13 opportunistic infections (12.7%) with 11 antigenemia-positive.

CONCLUSIONS

Preemptive therapy drastically reduces the incidence of CMV disease and the associated morbidity. Compared to universal prophylaxis, this approach may avoid unnecessary pharmacologic treatment in more than 50% of transplant recipients. Indeed, preemptive therapy does not fully prevent CMV disease, because it may manifest at the first antigenemia determination, and furthermore may select gancyclovir-resistant strains.

Comparison of sequential cytomegalovirus isolates in a patient with lymphoma and failing antiviral therapy

BACKGROUND

Long-term anti-cytomegalovirus (CMV) treatments in immunocompromised patients are hampered by resistance to antiviral drugs. Longitudinal changes in the resistance genotype may depend on changes in selective pressure and the complexity of CMV isolates.

OBJECTIVE

To evaluate longitudinal changes in the CMV resistance genotype and phenotype along with strain-specific variability in a patient with non-Hodgkin's lymphoma in whom successive anti-CMV treatments failed.

STUDY DESIGN

The resistance phenotype and genotype of seven CMV isolates collected from one patient during a 2-year follow-up period were retrospectively analysed. In parallel, we used glycoprotein B (gB) genotyping, and a- and UL10-13-sequence analysis to study CMV interstrain variability.

RESULTS

The patient was infected by at least three CMV strains plus variants of the parental strains. Resistance to ganciclovir, cidofovir and foscarnet was successively detected during the follow-up period. UL97 protein kinase changes responsible for resistance to ganciclovir were initially detected at residues 591 and 592, and then at position 594. Decreased sensitivity to foscarnet coincided with the appearance of amino acid substitution N495K in DNA polymerase, whereas cross-resistance to ganciclovir and cidofovir was due to the L501I substitution.

CONCLUSIONS

The CMV isolates obtained from our patient were complex mixtures of strains. Changes in resistance genotypes depended on resistance selective pressure and were not linked to interstrain variation.

Comparative study of prophylactic oral ganciclovir and valacyclovir in high-risk kidney transplant recipients

BACKGROUND

Cytomegalovirus (CMV) is a major pathogen in renal transplant patients causing significant post-transplant morbidity and mortality. Prophylactic antiviral therapy, currently implemented in most kidney transplant centres, has significantly reduced the incidence of CMV infection after transplantation. Oral ganciclovir has been shown to be an effective prophylactic agent in preventing CMV disease and infection with a demonstrated superior efficacy over oral acyclovir. Valacyclovir, a prodrug of acyclovir with a higher level of bioavailability than acyclovir, has also been shown to be effective in preventing CMV disease when given as prophylactic treatment.

METHODS

In a retrospective analysis of 150 renal transplant recipients in our centre, we compared the efficacy of oral ganciclovir with valacyclovir in preventing CMV infection. Seventy-seven consecutive renal transplant recipients prophylactically treated with oral ganciclovir for 12 weeks after transplant were compared with 73 consecutive recipients treated with oral valacylovir for an equal length of time.

RESULTS

No difference was noted in the incidence of CMV infection between the two treatment groups (5.1 vs 5.4%) after a 6 month follow-up. Likewise, the incidence of acute rejection was similar in both groups (11.6 vs 6.8%). All cases of CMV infection occurred in high-risk patients (donor positive/recipient negative).

CONCLUSION

The prophylactic use of oral valacylovir is as effective as oral ganciclovir in reducing CMV infection and disease after kidney transplantation.

Genomes of the endothelial cell-tropic variant and the parental Toledo strain of human cytomegalovirus are highly divergent

The low-passage Toledo strain of human cytomegalovirus (HCMV) and fresh clinical HCMV isolates have been reported to share the capacity to propagate efficiently in endothelial cell cultures. In the laboratory, however, repeated attempts to adapt the Toledo strain to growth in endothelial cells have been unsuccessful. Southern blot analysis of the entire viral genome and restriction length polymorphism analysis of multiple genome regions amplified by PCR demonstrated that the reported endothelial cell-tropic viral variant of the Toledo strain and the parental Toledo strain are highly divergent. In fact, the restriction profile of the genome of the endothelial cell-tropic variant seems highly distinct from that of the parental strain. In conclusion, the degree of dissimilarity between the two genomes suggests that the endothelial cell-tropic variant of the Toledo strain could have originated from a recombination event.

Emergence of ganciclovir-resistant cytomegalovirus in lung transplant recipients

BACKGROUND

Since ganciclovir-resistant cytomegalovirus (CMV) disease was initially described in a patient with acquired immunodeficiency syndrome (AIDS) in 1986, the incidence of ganciclovir-resistant CMV disease appears to be increasing in immunocompromised patients. More recently, there have been sporadic reports of ganciclovir-resistant CMV disease in solid organ transplantation.

METHODS

We retrospectively assessed the incidence of ganciclovir-resistant CMV disease in all lung transplant recipients transplanted between 6/93 and 6/01 at Loyola University Medical Center. All patients underwent routine CMV blood culture, shell vial assay as well as phenotypic and genotypic anti-viral susceptibility testing according to a pre-determined schedule. The number of CMV episodes, intravenous ganciclovir use, acute and chronic rejection and survival data were documented for all patients.

RESULTS

Twelve of 212 (6%) transplant recipients developed ganciclovir-resistant CMV disease. Ganciclovir resistance was associated with a higher number of CMV episodes (3.4 +/- 2.3 episodes/patient vs 1.7 +/- 0.7 episodes/patient [p < 0.05]) and an increased exposure to cumulative intravenous ganciclovir in the primary CMV-mismatched (D(+)R(-)) population (22 +/- 10 vs 13 +/- 7 days [p < 0.05]) compared with patients who did not develop ganciclovir resistance. In addition, the use of daclizumab therapy was associated with a 7-fold greater likelihood of developing ganciclovir resistance (p < 0.0001). The presence of ganciclovir-resistant CMV disease in our population was associated with a decreased survival that could be attributed to CMV disease itself (p < 0.05).

CONCLUSIONS

By screening all lung transplant recipients with CMV disease for ganciclovir resistance, we were able to detect a higher incidence of ganciclovir-resistant CMV disease (6%) than previously seen in solid organ transplantation. High-risk patients (D(+)R(-) CMV serostatus) who receive anti-lymphocytic therapy should be monitored aggressively and treated to prevent the development of ganciclovir resistance and avert a negative outcome.

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.

Ganciclovir-resistant cytomegalovirus in organ transplant recipients

Ganciclovir-resistant (GanR) cytomegalovirus (CMV) is an emerging clinical problem in organ transplant recipients, particularly recipients of kidney and pancreas and lung transplants. GanR CMV, a late posttransplantation complication, is observed predominantly among CMV-seronegative recipients of organs from seropositive donors, especially among recipients receiving intensive immunosuppression and having prolonged exposure to ganciclovir. Given the limitations of current diagnostic methods, if GanR CMV is clinically suspected, empirical treatment with intravenously administered foscarnet should be used in conjunction with reductions in immunosuppressive therapy and possibly CMV hyperimmune globulin. Better diagnostic tools and newer, less-toxic antiviral agents with different mechanisms of action are urgently needed to decrease the morbidity associated with this complication in organ transplant recipients.

Cardiac Transplantation: Pre-transplant Infectious Diseases Evaluation and Post-transplant Prophylaxis

Screening of recipients and donors of cardiac allografts for infectious pathogens, and the use of appropriate immunization and antimicrobial prophylaxis strategies, remain important for the control of infection following heart transplantation. However, the risk of infectious complications in a particular patient must often be weighed against the risk of delaying or denying allograft transplantation. In addition, the ongoing degree of immunosuppression and its contribution to the risk for infectious complications should also be considered to guide the length of prophylactic antimicrobial therapy and provide optimal patient care.

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.

Mutations in the UL97 ORF of ganciclovir-resistant clinical cytomegalovirus isolates differentially affect GCV phosphorylation as determined in a recombinant vaccinia virus system

Mutations in the human cytomegalovirus (HCMV) UL97 phosphotransferase have been associated with ganciclovir (GCV) resistance due to an impairment of GCV monophosphorylation. Vaccinia virus recombinants (rVV) were generated that encoded different HCMV UL97 proteins (pUL97) with mutations previously detected in resistant HCMV clinical isolates at codons 460, 520, 592, 594, 595, 598 and 607. These rVVs allowed quantification of GCV phosphorylation catalyzed by the different mutated pUL97s. When compared to rVV-UL97 wild type, mean levels of residual intracellular GCV phosphorylation differed by a factor of 10 for the mutated UL97 proteins ranging from 5.2 to 51.8%. Mutations M460V (located in a UL97 region homologous to domain VIb of protein kinases) and H520Q (located in a cytomegalovirus-specific, functionally critical domain) were responsible for the lowest levels of residual GCV phosphorylation (9.3 and 5.2%). Mutations in a region homologous to the domain IX had a lower impact on GCV phosphorylation (15.8-51.8%). The relevance of pUL97 mutation G598S in inducing GCV resistance was demonstrated for the first time.

Resistance of herpesviruses to antiviral drugs: clinical impacts and molecular mechanisms

Nucleoside analogues such as acyclovir and ganciclovir have been the mainstay of therapy for alphaherpesviruses (herpes simplex virus (HSV) and varicella-zoster virus (VZV)) and cytomegalovirus (CMV) infections, respectively. Drug-resistant herpesviruses are found relatively frequently in the clinic, almost exclusively among severely immunocompromised patients receiving prolonged antiviral therapy. For instance, close to 10% of patients with AIDS receiving intravenous ganciclovir for 3 months excrete a drug-resistant CMV isolate in their blood or urine and this percentage increases with cumulative drug exposure. Many studies have reported that at least some of the drug-resistant herpesviruses retain their pathogenicity and can be associated with progressive or relapsing disease. Viral mutations conferring resistance to nucleoside analogues have been found in either the drug activating/phosphorylating genes (HSV or VZV thymidine kinase, CMV UL97 kinase) and/or in conserved regions of the viral DNA polymerase. Currently available second line agents for the treatment of herpesvirus infections--the pyrophosphate analogue foscarnet and the acyclic nucleoside phosphonate derivative cidofovir--also inhibit the viral DNA polymerase but are not dependent on prior viral-specific activation. Hence, viral DNA polymerase mutations may lead to a variety of drug resistance patterns which are not totally predictable at the moment due to insufficient information on specific drug binding sites on the polymerase. Although some CMV and HSV DNA polymerase mutants have been found to replicate less efficiently in cell cultures, further research is needed to correlate viral fitness and clinical outcome.

Lack of emergence of cytomegalovirus UL97 mutations conferring ganciclovir (GCV) resistance following preemptive GCV therapy in allogeneic stem cell transplant recipients

Fifty allogeneic stem cell transplant recipients were enrolled in a prospective cytomegalovirus pp65 antigenemia-guided preemptive therapy trial. Among these, 10 of 34 patients who received ganciclovir exhibited sustained and/or recurrent antigenemia despite treatment. Thirteen leukocyte preparations from these 10 subjects were screened for the presence of the most frequent cytomegalovirus UL97 mutations conferring ganciclovir resistance. None of these mutations were detected after mean and median ganciclovir exposures of 31.6 and 28.0 days, respectively.

Sequence analysis of UL54 and UL97 genes and evaluation of antiviral susceptibility of human cytomegalovirus isolates obtained from kidney allograft recipients before and after treatment

The frequency of infections caused by drug-resistant cytomegalovirus (CMV) in solid-organ transplant recipients is not known. Only a few resistant strains have been described in transplant recipients. Antiviral susceptibility to ganciclovir (GCV) and foscarnet (PFA) of CMV isolates from 24 renal transplant patients with CMV viremia and CMV disease before and after therapy were investigated by a solid phase ELISA. The CMV DNA polymerase (UL54) and viral phosphotransferase (UL97) genes were also sequenced. Ten patients did not receive antiviral treatment; five and nine patients were treated with PFA and GCV, respectively. No appearance of drug-resistant viruses was observed in the present study, but one isolate showed a reduced sensitivity to PFA after treatment with GCV. This finding could not be explained by the presence or development of mutations that have been associated with drug resistance in UL54. We found no evidence that short-term treatment of CMV with PFA- or GCV-induced resistance.

Longitudinal observations on mutations conferring ganciclovir resistance in patients with acquired immunodeficiency syndrome and cytomegalovirus retinitis: The Cytomegalovirus and Viral Resistance Study Group Report Number 8

PURPOSE

Cytomegalovirus retinitis is the most common intraocular infection in patients with acquired immunodeficiency syndrome (AIDS). With prolonged suppressive anticytomegalovirus maintenance therapy, resistance occurs in over 25% of patients. We evaluated longitudinal changes in the cytomegalovirus genotype in patients with cytomegalovirus retinitis who developed ganciclovir resistance that was demonstrated in either the blood or urine.

METHODS

Patients with AIDS and previously untreated cytomegalovirus retinitis were followed prospectively for the occurrence of resistance while on treatment. Blood and urine specimens were obtained periodically for cytomegalovirus culture according to a predetermined schedule. Positive isolates were tested for phenotypic susceptibility and for mutations in the UL97 and UL54 genes.

RESULTS

A mutation conferring resistance to ganciclovir in either the UL97 or UL54 gene was detected in 18 patients. In general, patients with a genotypically resistant virus developed increasing phenotypic resistance over time. There was a suggestion that unless therapy was changed, UL97 mutations tended to persist. In seven of eight patients, the mutations identified in isolates from the blood and urine were identical. In selected patients, there was a suggestion that a mixed population of cytomegalovirus might be present. Progression of the retinitis in an involved eye (15 of 18), contralateral eye retinitis (10 of 11), and extraocular cytomegalovirus disease (5 of 18) occurred commonly among patients with resistant virus.

CONCLUSION

Resistance-conferring mutations in the cytomegalovirus genome emerge and may persist when the selective pressure for resistance is maintained. Some patients appear to harbor complex subpopulations of virus with different mutations and different levels of phenotypic resistance. Changes in therapy may result in a shift in virus population and changes in the cytomegalovirus genotype identified.

Sequencing of cytomegalovirus UL97 gene for genotypic antiviral resistance testing

The widespread use of ganciclovir (GCV) to treat cytomegalovirus (CMV) infections in immunosuppressed patients has led to the development of drug resistance. Phenotypic assays for CMV drug resistance are presently too time-consuming to be therapeutically useful. To support the development of genotypic assays for GCV resistance, the complete sequences of the UL97 phosphotransferase genes in 28 phenotypically GCV-sensitive CMV clinical isolates were determined. The gene was found to be highly conserved, with nucleotide sequence identity among strains ranging from 98.6 to 100% and amino acid sequence identity of >99%. Primers for a genotypic assay were designed to amplify codons 400 to 707, because all known UL97 mutations conferring drug resistance occur at three sites within this region. This part of the UL97 gene was amplified from over 50 clinical isolates, and two sequencing reactions for the coding strand were successfully used to identify GCV resistance mutations. This genotypic assay can be performed in 48 h using genomic DNA extracted from cell monolayers at very low levels of virus infectivity, thus rapidly providing therapeutically useful results.

Infectious complications of solid organ transplantations

The rate of infectious complications in SOT recipients has declined dramatically. As improvements in immunosuppressive therapy, surgical techniques, and diagnostics and antimicrobial treatment continue, further declines in infectious complications are expected. Refinements to preemptive therapy for high-risk patients are likely to contribute further to this decrease. Further investigation is required to define what role various infectious agents play in chronic allograft injury and rejection.

Preemptive therapy versus universal prophylaxis with ganciclovir for cytomegalovirus in solid organ transplant recipients

Whether preemptive therapy or universal prophylaxis with ganciclovir is the optimal approach against cytomegalovirus (CMV) remains unresolved. Controversy abounds with respect to the efficacy of preemptive therapy, the reliability of preemptive therapy tools, the logistical difficulties in conducting surveillance monitoring for CMV, the cost of prophylaxis, the effect of prophylaxis on indirect sequelae of CMV and epidemiology of CMV, and the potential for emergence of ganciclovir-resistant CMV. Although neither approach is wholly adequate, a discussion of the relative merits and limitations of the 2 approaches may guide the selection of a rational approach toward prevention of CMV infection in organ transplant recipients.

Emergence of multiple human cytomegalovirus ganciclovir-resistant mutants with deletions and substitutions within the UL97 gene in a patient with severe combined immunodeficiency

Infection with multiple ganciclovir-resistant human cytomegalovirus mutants, containing different substitutions and deletions in the UL97 gene, was found in a patient with severe combined immunodeficiency (SCID) within 3 weeks of ganciclovir therapy. A novel 11-codon deletion at positions 590 to 600 was identified. These unique findings may be related to the nature of the immunodeficiency in the SCID patient.

Drug-resistant human cytomegalovirus infection in children after allogeneic stem cell transplantation may have different clinical outcomes

Three seropositive pediatric recipients of allogeneic stem cell transplantation out of a group of 42 patients receiving T-cell–depleted, unrelated transplants and 37 patients receiving T-cell–depleted, haploidentical transplants were monitored longitudinally for human cytomegalovirus (HCMV) infection and the emergence of antiviral drug resistance. Early in the posttransplant course, all 3 patients developed HCMV mutations conferring drug resistance to ganciclovir. One child additionally developed multidrug resistance to foscarnet and cidofovir, with mutations in the viral phosphotransferase gene (UL97) and the DNA-polymerase gene (UL54) being found. These data show that resistant HCMV infection does not necessarily correlate with a severe clinical outcome. The early detection of genotypic resistance up to 129 days before the emergence of phenotypic resistance and the dissociation of resistance patterns among different body sites emphasize the importance of genotypic analyses of different DNA specimens for an efficient antiviral therapy. T-cell–depleted children having transplantation might be at an increased risk for the development of drug resistance.

Drug-resistant human cytomegalovirus infection in children after allogeneic stem cell transplantation may have different clinical outcomes

Three seropositive pediatric recipients of allogeneic stem cell transplantation out of a group of 42 patients receiving T-cell–depleted, unrelated transplants and 37 patients receiving T-cell–depleted, haploidentical transplants were monitored longitudinally for human cytomegalovirus (HCMV) infection and the emergence of antiviral drug resistance. Early in the posttransplant course, all 3 patients developed HCMV mutations conferring drug resistance to ganciclovir. One child additionally developed multidrug resistance to foscarnet and cidofovir, with mutations in the viral phosphotransferase gene (UL97) and the DNA-polymerase gene (UL54) being found. These data show that resistant HCMV infection does not necessarily correlate with a severe clinical outcome. The early detection of genotypic resistance up to 129 days before the emergence of phenotypic resistance and the dissociation of resistance patterns among different body sites emphasize the importance of genotypic analyses of different DNA specimens for an efficient antiviral therapy. T-cell–depleted children having transplantation might be at an increased risk for the development of drug resistance.

Abstension from treatment of low-level pp65 cytomegalovirus antigenemia after liver transplantation: a prospective study

BACKGROUND

Ganciclovir is a highly effective and relatively safe drug to treat cytomegalovirus (CMV) infection in liver transplant patients; CMV resistance to ganciclovir is progressively emerging due to the extensive use of the drug in transplant and AIDS patients; CMV pp65 antigenemia allows early diagnosis of CMV infection and quantitation of the viral load; preemptive antigenemia-guided therapy of CMV infection can prevent CMV disease but the threshold of antigenemia value above which treatment has to be instituted is unclear.

METHODS

To demonstrate the safety of abstention from preemptive treatment in the presence of low levels of antigenemia 77 consecutive liver transplant recipients were prospectively evaluated. Antigenemia was tested twice a week from transplantation until discharge, then once a week until the third postoperative month. In absence of risk factors for CMV disease, namely donor positive/recipient negative CMV serology, treatment with antibodies to lymphocytes and retransplantation, only patients with antigenemia of more than 50 or symptoms possibly related to CMV infection had preemptive treatment.

RESULTS

A total of 32 patients had at least one positive antigenemia test with a value less than 50; 22 (68.7%) spontaneously cleared the virus, 3 were treated with i.v. ganciclovir for the presence of fever, and the other 7 (21,8%) progressed to values of antigenemia of more than 50 and were treated even if asymptomatic. No CMV disease was observed in these patients.

CONCLUSION

CMV antigenemia less than 50 in liver transplant recipients with low and intermediate risk for CMV disease does not mandate preemptive ganciclovir treatment. Close surveillance with repeated determination of antigenemia until its negativization and careful clinical and laboratory monitoring is advisable.

Long-term oral ganciclovir prophylaxis for prevention of cytomegalovirus infection and disease in cytomegalovirus high-risk renal transplant recipients

BACKGROUND

Although specific therapy is available with ganciclovir, cytomegalovirus (CMV) disease remains a major problem after renal transplantation especially in CMV seronegative recipients of organs of seropositive donors (D+R-).

METHODS

In an open-labeled prospective controlled trial we evaluated the effect of long-term oral ganciclovir prophylaxis (3 g/day for 3 months posttransplantation) in a cohort of 31 CMV-high risk (D+R-) renal transplant recipients (GC) compared with a cohort of 28 high-risk patients with targeted CMV prophylaxis (CO) receiving i.v. ganciclovir during antirejection therapy. Primary end-points were CMV infection, diagnosed by pp65 antigenemia assay or serologic method, and CMV disease. Additionally severity of CMV disease quantified by a scoring system was evaluated.

RESULTS

CMV prophylaxis significantly reduced the incidence of CMV infection (CO: 75%, GC: 45%; P<.05) and CMV disease (CO: 60%, GC: 29%; P<.05) without relevant side effects and without any clinical suspicion of ganciclovir resistance. Severity of CMV disease as quantified by a scoring system was reduced from 8.3+/-6.7 points in controls to 3.3+/-2.6 points in ganciclovir-treated patients (P<.05). Mortality did not differ significantly between the two groups (CO: n=3, GC: n=1; NS). However, there was one lethal CMV disease and a second death possibly attributable to CMV disease in the control group, whereas in ganciclovir-treated patients there was no CMV-associated fatal outcome.

CONCLUSION

Long-term oral ganciclovir prophylaxis is effective and safe in CMV high-risk renal transplant recipients.

Emergence of ganciclovir-resistant cytomegalovirus disease among recipients of solid-organ transplants

BACKGROUND

Concerns have been raised about emergence of ganciclovir resistance as a result of the advent of both routine oral ganciclovir prophylaxis and highly potent immunosuppression. We retrospectively assessed the occurrence of ganciclovir-resistant cytomegalovirus disease among transplant recipients who had received oral ganciclovir prophylaxis and highly potent immunosuppression.

METHODS

We studied 240 recipients of liver, kidney, or pancreas transplants. Antiviral susceptibility testing of blood cytomegaloviral isolates was done when patients failed to respond to intravenous ganciclovir treatment for symptomatic cytomegalovirus infection. Portions of the UL97 gene associated with ganciclovir resistance were sequenced in cytomegalovirus isolates with phenotypic resistance to ganciclovir.

FINDINGS

Ganciclovir-resistant cytomegalovirus disease developed in five (7%) of 67 seronegative recipients of cytomegalovirus-seropositive organs (D+/R-) compared with none of 173 seropositive recipients (p=0.002). Among the 25 (10.4%) patients who developed cytomegalovirus disease within 1 year after transplantation, five had ganciclovir-resistant cytomegalovirus disease. Among D+/R-transplant recipients, ganciclovir-resistant cytomegalovirus disease was more common among the group receiving the most potent immunosuppression--ie, recipients of kidney and pancreas or pancreas alone (four of 19) compared with all other transplant recipients (one of 48, p=0.02). Ganciclovir-resistant cytomegalovirus disease was diagnosed at a median of 10 months after transplantation (range 7-12) after lengthened exposure to ganciclovir, was associated with previously described mutations of the UL97 gene, and led to serious clinical complications.

INTERPRETATION

Ganciclovir-resistant cytomegalovirus is an important cause of late morbidity among D+/R- transplant recipients who have had lengthened exposure to ganciclovir and have received highly potent immunosuppression. Strategies to reduce this complication, especially among D+/R- patients, are warranted.

Prediction of cytomegalovirus load and resistance patterns after antiviral chemotherapy

Cytomegalovirus (CMV) replicates rapidly in its human host with a doubling time of approximately 1 day. Using simple mathematical models we show that the efficacy of the anti-CMV drug ganciclovir (GCV) against wild-type strains is 91.5% [95% confidence interval (CI) 89-94%] when given i.v. (5 mg/kg twice a day) but only 46.5% (95% CI 45-47.5%) when given orally (1 g three times a day) whereas the corresponding figures for a typical GCV-resistant virus are 62% (95% CI 57-66%) and 35% (95% CI 33-37%), respectively. During prolonged periods of GCV therapy we show that the apparent sudden appearance of GCV resistance is explained by the combination of two exponentially increasing populations (wild type and mutant) at doses of GCV that do not completely inhibit CMV replication. Cell culture methods to assess CMV drug resistance in vivo will underestimate its prevalence because of the fitness loss of resistant virus in the absence of therapy. The parameters determined from these models then were used to predict the likely viral load and resistance patterns in patients on prolonged therapy with GCV. The modeled and experimental data showed excellent agreement over extended time periods (up to 270 days of therapy) and provide a framework to predict the virologic course of patients at therapeutic initiation.

Pharmacokinetic assessment of oral ganciclovir in lung transplant recipients with cystic fibrosis

Oral ganciclovir has been used as prophylaxis and therapy against cytomegalovirus in patients with HIV infection and following organ transplantation. Oral ganciclovir has clear practical advantages over intravenous ganciclovir but has a relatively low bioavailability and this may be problematic in at-risk patients with malabsorption. The bioavailability and therefore therapeutic potential of oral ganciclovir in cystic fibrosis (CF) patients post-lung transplant (LT) might be expected to be inadequate given the high incidence of malabsorption in these patients. An 8 h pharmacokinetic study was performed in 12 CF patients 160 +/- 122 days post-transplant who had been taking 1 g oral ganciclovir tds for 3 days with food (plus normal enzyme supplements). Mean (range) serum creatinine was 150 Imol/L (70-280). Blood was sampled at 0.5, 1, 2, 3, 4, 6 and 8 h post-final dose. Plasma was stored at -20 degrees C and later analysed by highperformance liquid chromatography. Mean peak concentration (C(max)) was 4.8 mg/L (0. 96-12.8), mean minimum concentration (C(min)) was 3.6 mg/L (0.78-11. 7) and mean area under the curve (AUC) was 35.4 mg.8 h/L (8-99). C(max), C(min) and AUC correlated significantly with one another (P < 0.001) as well as with serum creatinine and creatinine clearance (P < 0.01). When corrected for alterations in renal function, plasma oral ganciclovir levels are as predicted for other transplant populations. Three days of oral ganciclovir results in therapeutically useful plasma drug levels in the CF LT population, despite a background of general malabsorption. C(max), C(min) and AUC are highly correlated, allowing for the possibility of steady-state drug monitoring to confirm that the recommended dosing algorithm produces appropriate plasma levels.

Prevention of recurrent cytomegalovirus disease in renal and liver transplant recipients: effect of oral ganciclovir

BACKGROUND

Although the primary treatment of symptomatic cytomegalovirus (CMV) disease in organ transplant recipients is successful in >90% of individuals, relapsing disease, particularly in those with primary infection, remains an important problem. Previously, we had observed that the rate of symptomatic recurrence was >60% in those with primary disease (seronegative for CMV prior to transplant), and approximately 20% in those who were seropositive prior to transplant. The present study was undertaken to determine whether a maintenance regimen of oral ganciclovir for 2-3 months added to the routine 14-21 days of intravenous ganciclovir would further prevent symptomatic CMV recurrence.

METHODS

From May 1995 until June 1998, all kidney and liver transplant recipients with confirmed tissue-invasive CMV disease or CMV syndrome were treated with 14-21 days of intravenous ganciclovir (5 mg/kg b.i.d. with dose adjusted for renal dysfunction) followed by 2-3 months of oral ganciclovir (2 g daily). The incidence of recurrence of CMV disease and/or viremia during and after oral therapy was then determined over a mean follow-up of 530.6 days.

RESULTS

Thirty-seven patients, 19 kidney and 18 liver transplant recipients, were studied; 5 had biopsy-proven tissue-invasive disease (13.5) and 32 suffered a CMV syndrome (86.5). Twenty-one of these patients (58.6) were seronegative for CMV prior to transplant and received an allograft from a seropositive donor (D+/R-). Overall, 10 patients (27.0) developed CMV recurrence. Eight of 21 patients who were D+/R- for CMV (38.1) developed recurrence as opposed to 2 of 16 patients with other serologic status (12.5) (P=0.14). Patients with recurrent CMV disease and/or viremia had a peak antigenemia assay titer during their initial CMV event of 319.2 positive cells/2 slides compared with 109.8 positive cells/2 slides for patients without recurrent CMV infection (P=0.14); the trend of having a higher peak antigenemia assay titer among patients who recurred occurred both in patients who were at risk of primary CMV infection (D+/R- for CMV) and in those who were not. Two patients developed recurrent infection with strains of CMV that were resistant to ganciclovir.

CONCLUSIONS

This new therapeutic regimen of oral ganciclovir following intravenous ganciclovir slightly reduced the overall rate of recurrent CMV disease and/or viremia, but it still did not adequately prevent CMV recurrence in patients who are at risk of primary infection prior to transplant. Of particular concern, 2 patients with primary infection treated with this regimen developed ganciclovir-resistant recurrent disease.

Development of cytomegalovirus resistance to ganciclovir after oral maintenance treatment in a renal transplant recipient

The emergence of a resistant strain is a theoretical threat after extensive use of antiviral drugs. We report the emergence of a ganciclovir-resistant cytomegalovirus (CMV) strain in a kidney transplant recipient during oral ganciclovir maintenance treatment. The patient was treated by oral ganciclovir for 2 months after successful treatment of CMV primary infection by intravenous ganciclovir. He developed a new episode of CMV infection with no clinical response to intravenous ganciclovir. The CMV isolate exhibited both phenotypic and genotypic resistance to ganciclovir. The CMV isolate was constituted of a mixture of strains, with and without a mutation at codon 460 of the UL97 gene. The clinical condition improved when mycophenolate mofetil (MMF) was discontinued, and a short course of intravenous globulin was added to ganciclovir. The emergence of the CMV strain could be secondary to more potent immunosuppression provide by MMF or subtherapeutic level obtained during oral ganciclovir treatment. We believe that ganciclovir resistance must be part of the differential diagnosis when a patient relapses or fails to respond to ganciclovir treatment.