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

The human cytomegalovirus

Human cytomegalovirus (HCMV), a betaherpesvirus, represents the major infectious cause of birth defects, as well as an important pathogen for immunocompromised individuals. The viral nucleocapsid containing a linear double-stranded DNA of 230 kb is surrounded by a proteinaceous tegument, which is itself enclosed by a loosely applied lipid bilayer. Expression of the HCMV genome is controlled by a cascade of transcriptional events that leads to the synthesis of three categories of viral proteins designated as immediate-early, early, and late. Clinical manifestations can be seen following primary infection, reinfection, or reactivation. About 10% of infants are infected by the age of 6 months following transmission from their mothers via the placenta, during delivery, or by breastfeeding. HCMV is a significant post-allograft pathogen and contributes to graft loss independently from graft rejection. Histopathologic examination of necropsy tissues demonstrates that the virus enters via the epithelium of the upper alimentary, respiratory, or genitourinary tracts. Hematogenous spreading is typically followed by infection of ductal epithelial cells. Infections are kept under control by the immune system. However, total HCMV clearance is rarely achieved, and the viral genome remains at selected sites in a latent state. Virological and molecular detection of HCMV, as well as serological demonstration of a specific immune response, are used for diagnosis. Treatment of HCMV infections is difficult because there are few options. The presently available drugs produced a significant clinical improvement, but suffer from poor oral bioavailability, low potency, development of resistance in clinical practice, and dose-limiting toxicities.

Synergy of bovine lactoferrin with the anti-cytomegalovirus drug cidofovir in vitro

Human cytomegalovirus (HCMV) causes severe morbidity and mortality in immunocompromised patients. Treatment of HCMV infections with conventional antiviral drugs like ganciclovir and cidofovir has major drawbacks (i.e. serious side effects). Therefore, combination therapies using drugs with different antiviral mechanisms should be envisaged. Potential synergy between lactoferrin (LF), an antibacterial, antimycotic and antiviral protein, and the antiviral drugs acyclovir, ganciclovir, foscarnet and cidofovir was investigated, using an in vitro test system with the recombinant RC256 HCMV strain.

RESULTS

Combination of LF with acyclovir and foscarnet resulted in antagonism. When LF and ganciclovir were combined, neither synergy nor antagonism was observed. Strikingly, the combination of LF with cidofovir resulted in marked synergy. The synergistic effect could be explained by inhibition of two subsequent steps in the viral replication cycle: HCMV penetration into the target cells and intracellular synthesis of HCMV DNA. In conclusion, LF might be a potential candidate for combination therapy with cidofovir.

Randomized comparison of oral valacyclovir and intravenous ganciclovir for prevention of cytomegalovirus disease after allogeneic bone marrow transplantation

In this multicenter, randomized study, cytomegalovirus (CMV)-seropositive patients who received an allogeneic bone marrow transplant were provided high-dose intravenous acyclovir (500 mg/m(2) q8h) from the day of transplantation until engraftment. The patients were then randomly assigned to receive either oral valacyclovir, 2 g q.i.d. (n=83), or intravenous ganciclovir, 5 mg/kg q12h for 1 week, then 6 mg/kg once daily for 5 days per week (n=85), until day 100 after transplantation. CMV infection occurred in 12% of the patients who received valacyclovir and in 19% of the patients who received ganciclovir (hazard ratio [HR], 1.042; 95% confidence interval [CI], 0.391-2.778; P=.934). CMV disease developed in only 2 patients who received valacyclovir and in 1 patient who received ganciclovir (HR, 1.943; 95% CI, 0.176-21.44; P=.588). Oral valacyclovir can be an effective alternative to intravenous ganciclovir for prophylaxis of CMV disease after bone marrow transplantation.

Viral escape and T-cell immunity during ganciclovir treatment of cytomegalovirus infection: case report of a pancreatico-renal transplant recipient

BACKGROUND

Pancreas-kidney transplant recipients are at high risk for cytomegalovirus (CMV) disease despite prophylactic ganciclovir therapy. Because the impact of antiviral therapy on anti-CMV immune reactions is unknown, CMV-specific T-cell subsets in primary and recurrent CMV infection were analyzed in a pancreas-kidney transplant case study.

METHODS

Major histocompatibility complex class I tetramers were used to detect peripheral CMV pp65-specific CD8 T cells. Intracellular cytokine staining was used to determine the frequency of CMV-specific CD4 T cells. Conventional virologic parameters and routine laboratory parameters were monitored. For ganciclovir resistance testing, CMV-UL97 genotyping was performed.

RESULTS

Despite prophylactic ganciclovir therapy, primary CMV infection induced in vivo expansion of activated CMV-specific CD8 T cells. Interestingly, viral dissemination during recurrent CMV disease was a result of partially ganciclovir-resistant CMV. Recovery after discontinued ganciclovir treatment was associated with the expansion of CMV-specific CD4 T cells.

CONCLUSION

Immunologic monitoring may contribute to clinical management of recurrent CMV disease.

Impact of current transplantation practices on the changing epidemiology of infections in transplant recipients

The spectrum of infections in transplant recipients has been substantially affected by novel immunosuppressive regimens and the use of antimicrobial agents. Epidemiology and presentation of traditional opportunistic pathogens has changed. Invasive aspergillosis and cytomegalovirus occur later in the post-transplant period. The incidence of infections that were previously encountered rarely--eg, BK virus nephropathy--has increased, the clinical course of hepatitis C virus recurrence has become more aggressive, the risk factors for invasive aspergillosis have changed, and non-aspergillus moulds are occurring more commonly in transplant recipients. Recognition of these trends as they unfold has significant implications for the clinical care of the transplant recipients, for providing insights into the pathogenesis, and for continually improving the approaches to the management of infections.

Randomized controlled trial of oral ganciclovir versus oral acyclovir after induction with intravenous ganciclovir for long-term prophylaxis of cytomegalovirus disease in cytomegalovirus-seropositive liver transplant recipients

BACKGROUND

Without effective antiviral prophylaxis, cytomegalovirus (CMV) disease is a common cause of morbidity and mortality after liver transplantation. In this randomized, controlled trial, we compared the efficacy and safety of oral ganciclovir with oral acyclovir after induction with intravenous (IV) ganciclovir for long-term prophylaxis of CMV disease in CMV-seropositive liver transplant recipients.

METHODS

Patients were initially administered IV ganciclovir at a dose of 6 mg/kg per day from day 1 to day 14 after transplantation followed by either oral ganciclovir (1 g every 8 hr) or oral acyclovir (800 mg every 6 hr) from day 15 to day 100 after transplantation.

RESULTS

CMV disease occurred in only 1 of 110 patients (0.9%) receiving ganciclovir compared with 8 of 109 patients (7.3%) receiving acyclovir within the first year after transplantation (P =0.019). There was one case of CMV colitis in the ganciclovir group, whereas four cases of CMV syndrome, three cases of CMV pneumonia, and one case of CMV hepatitis developed in the acyclovir group. The only death from CMV disease occurred in an acyclovir-treated patient with CMV pneumonia. Both oral ganciclovir and oral acyclovir were generally well tolerated. Reversible leukopenia (decline in white blood cell count to <3.0 x 10(9)/L) was more common with oral ganciclovir (38/110 patients, 35%) than with oral acyclovir (20/109 patients, 18%) (P =0.009). The emergence of ganciclovir-resistant strains of CMV was not found during the study.

CONCLUSIONS

A prophylactic regimen of 2 weeks of IV ganciclovir followed by an additional 12 weeks of oral ganciclovir is superior to a similar regimen of IV ganciclovir followed by oral acyclovir and almost completely eliminates CMV disease after liver transplantation. This superior protection against CMV disease extends up to 1 year after transplantation and is not associated with ganciclovir resistance.

Emergence of late cytomegalovirus central nervous system disease in hematopoietic stem cell transplant recipients

Preemptive ganciclovir therapy has reduced the occurrence of early cytomegalovirus (CMV) disease after hematopoietic stem cell (HSC) transplantation. However, late disease is increasingly reported. We describe 2 patients who developed late CMV central nervous system (CNS) disease after haploidentical HSC transplantation. Direct genotypic analysis was used to examine the presence of ganciclovir resistance. One patient had a mixed viral population in the cerebrospinal fluid (CSF), with coexistent wild-type and mutant UL97 sequences. The presence of 2 different strains was confirmed by subclone sequencing of the UL54 gene. One of the strains was different from the concurrent blood strain. The second patient had resistant variant in the lungs. These cases raise concern about the changing natural history of CMV disease in HSC transplantation, with emergence of previously uncommon manifestations following prolonged prophylaxis. Under these circumstances the CNS may be a sanctuary site, where viral persistence and antiviral drug resistance could result from limited drug penetration.

Trends in risk profiles for and mortality associated with invasive aspergillosis among liver transplant recipients

To discern whether the characteristics and outcome of invasive aspergillosis in liver transplant recipients have evolved during the past decade, 26 patients who underwent transplantation during 1990-1995 (known as "the earlier cohort") were compared with 20 patients who underwent transplantation during 1998-2001 (known as "the later cohort"). Twenty-three percent of the Aspergillus infections in the earlier cohort occurred > or =90 days after transplantation, compared with 55% of such infections in the later cohort (P=.026). The earlier cohort was significantly more likely to have disseminated infection (P=.034) and central nervous system (CNS) involvement (P=.0004) than was the later cohort. The mortality rate was significantly higher for the earlier cohort (92%) than for the later cohort (60%; P=.012). Only disseminated infection (not the year of transplantation) approached statistical significance as an independent predictor of outcome. In the current era, invasive aspergillosis occurs later in the posttransplantation period, is less likely to be associated with CNS infection, and is associated with a lower mortality rate, compared with invasive aspergillosis in the early 1990s.

Recipient screening prior to solid-organ transplantation

Screening a potential transplant recipient for infectious diseases is an important component of the transplantation process. Such screening may lead to the discovery and treatment of occult active infection, may help determine posttransplant prophylactic strategies, or may disqualify the recipient from receiving a transplant. The pretransplant period also affords an opportunity for updating vaccination status and providing education regarding the reduction of posttransplant infectious risks. The present brief review will outline the investigation of preexisting active infection, as well as latent bacterial, mycobacterial, fungal, parasitic, and viral infections. Recommendations for pretransplant immunization and education are provided.

Pre-emptive oral ganciclovir can reduce the risk of cytomegalovirus disease in liver transplant recipients

A cohort of 65 liver transplant recipients was prospectively monitored with qualitative polymerase chain reaction (PCR) in plasma. The first 25 patients did not receive prophylaxis. From a consecutive group of 40 recipients, 11 high-risk patients donor CMV-seropositive/receptor CMV-seronegative (D+/R-), persistent CMV replication) received pre-emptive oral ganciclovir (1000 mg three times daily), when a marker of risk was identified, until day 90. The overall incidence of cytomegalovirus (CMV) disease at six months was 20% (five of 25 patients) in the non-prophylaxis group and 2.5% (one of 40 patients) in the group treated with pre-emptive oral ganciclovir (relative risk, 0.11; 95% confidence interval; 0.01-0.96; P = 0.04). The PCR sensitivity for detecting CMV disease was 80%, the specificity was 90%, and the positive and negative predictive values were 66% and 95%, respectively. Adverse events, graft rejection and survival were similar between groups. We conclude that pre-emptive oral ganciclovir in high-risk patients can reduce the risk of CMV disease.

Ganciclovir-resistant cytomegalovirus encephalitis in a bone marrow transplant recipient

A 20-year-old patient, who received a bone marrow transplant in order to treat metachromatic leukodystrophy (MLD), succumbed to cytomegalovirus (CMV) encephalitis. After CMV viremia developed, the patient received ganciclovir, but he was switched to foscarnet when ganciclovir resistance was suspected. Foscarnet was discontinued because of concern about its potential central nervous system toxicity. Autopsy samples of brain and cerebrospinal fluid contained CMV DNA with a UL97 mutation (M460V) known to confer ganciclovir resistance. No foscarnet resistance mutations were found.

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.

Cytomegalovirus drug resistance and clinical implications

Antiviral agents are commonly used for cytomegalovirus (CMV) prophylaxis or therapy after solid organ transplantation. Until recently, the detection of drug-resistant CMV in this setting was rare, but ganciclovir resistance has now been reported to occur in 5-10% of high-risk patient subsets, such as those undergoing primary CMV infection. Persistent viral shedding or progressive CMV disease after several weeks of antiviral therapy may indicate a problem with drug resistance, though laboratory testing is required to confirm this. Rapid genotypic assays for specific mutations in the viral UL97 phosphotransferase or UL54 DNA polymerase genes can be used to detect resistance and predict cross-resistance to other drugs. The emergence of drug resistance may be reduced by optimization of host immunity, use of potent antiviral drug regimens, and adherence to dosing regimens that adequately suppress viral replication.

Molecular methods for cytomegalovirus surveillance in bone marrow transplant recipients

Two different methods for detection of cytomegalovirus (CMV), PCR and hybrid capture (HC), were compared by using plasma, peripheral blood leukocytes (PBLs), and whole blood (WB) from allogeneic bone marrow transplant recipients. One hundred specimens were obtained from nine children over an 18-month surveillance period. PCR of plasma for CMV was used for clinical management. The proportions of samples positive for CMV DNA by PCR with plasma, HC with WB, and PCR with PBLs were 21, 28, and 37%, respectively. Among 44 samples that were tested by all three methods, 68% had concordant results. By using a robust definition of true-positive samples (positivity by two or more methods or positivity of sequential samples by one method), the sensitivities of PCR with plasma, HC with WB, and PCR with PBLs were 50, 67, and 83%, respectively, and the specificities were 100, 96, and 96%, respectively. Two patients developed CMV-associated end-organ disease (one developed respiratory disease, and one developed gastrointestinal disease). CMV DNA was not detected in the plasma 1 week prior to the development of symptoms in either patient, whereas HC with WB was positive for both patients and PCR with PBLs was for one patient. These data suggest that WB or PBLs might be the preferred sample for use for surveillance for CMV in immunocompromised patients.

Preemptive strategy for ganciclovir administration against cytomegalovirus in liver transplantation recipients

In utilizing a preemptive strategy to minimize the occurrence of symptomatic cytomegalovirus (CMV) infection following liver transplant, only patients with proven CMV activity by direct detection are treated. We applied the following preemptive strategy for CMV infection to 49 sequential liver transplant recipients between 1998 and 2001. Patients were monitored for CMV activity using CMV p65 antigen assay for the first 10 months of the study. Thereafter, we changed the detection method to a quantitative PCR for plasma CMV-DNA. All patients were monitored post transplant, weekly for the first 3 months and then monthly. Only patients with detected CMV activity were treated with ganciclovir. Patients were divided into four groups, based on donor (D) and recipient (R) CMV status. In seven out of 49 patients (14.3%) CMV activity was detected: four in group D+/R-, and three in group D-/R-. Five out of these seven patients had asymptomatic CMV infection. Symptomatic CMV infection developed only in two of these seven patients, to give total rate of 4.1% (2/49). All seven patients developed CMV IgG antibody. 'Transient' CMV replication detected by PCR in five patients in group D+/R+ was not defined as infection. No patients developed organ-invasive CMV disease. The cost of anti-CMV treatment using the preemptive strategy was $1000/patient/1st year. Using preemptive strategy, early detection of CMV infection was achieved, allowing timely treatment. The use of ganciclovir for CMV infection in only 4.3% of the patients should have a positive impact on minimizing the risk of ganciclovir-resistant virus, and should reduce the cost of CMV prevention strategies.

Improved monitoring of cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation by an ultrasensitive plasma DNA PCR assay

Cytomegalovirus (CMV) DNA amplification assays in plasma have shown limited sensitivity compared to the detection of pp65 antigen in leukocytes. Our goal was to increase the sensitivity of a commercial CMV DNA PCR quantitative assay. After modification, the new assay was able to reproducibly detect 20 CMV DNA copies/ml of plasma. We compared this new ultrasensitive PCR assay with the standard PCR and the pp65 test for CMV detection and quantification in 22 consecutive allogeneic hematopoietic stem cell recipients. CMV infection or reactivation was detected in 84 of 319 (26%) samples by the ultrasensitive PCR assay compared to 38 of 319 (12%) samples by the pp65 assay (P < 0.01). All samples positive by the pp65 assay were positive by the ultrasensitive PCR, and CMV episodes were detected on average 4 days earlier and 7 days later than the first and the last pp65-positive test, respectively. In addition, during CMV episodes, the ultrasensitive assay identified positive samples that were inconsistently detected by the pp65 assay. The ultrasensitive assay was also much more sensitive than the standard PCR, with 26 versus 12% of CMV DNA-positive samples (P < 0.01). This assay improved the monitoring of CMV infection or reactivation in hematopoietic allogeneic stem cell recipients.

Beta-herpesvirus challenges in the transplant recipient

Cytomegalovirus (CMV) has major consequences after allogeneic stem cell and solid organ transplantation. CMV may cause significant morbidity and mortality, and monitoring to detect reactivation to reduce disease or management of end organ disease is associated with increased resource utilization. Two other members of the beta-herpesvirus family, human herpesvirus (HHV) type 6 and HHV-7, are increasingly recognized as important pathogens in transplant recipients, either by direct infection (e.g., encephalitis, hepatitis, or pneumonitis) or via interaction with CMV. In addition to direct effects of CMV infection, such indirect effects as an increased risk for bacterial and fungal infections or impaired graft acceptance and function are important research topics. Diagnosis and treatment of CMV infection is currently more advanced than for HHV-6 and HHV-7.

Rapid development of ganciclovir-resistant cytomegalovirus infection in children after allogeneic stem cell transplantation in the early phase of immune cell recovery

As recently reported, children having T cell-depleted peripheral blood stem cell transplantation (PBSCT) might be at increased risk for the development of drug resistance. To investigate if delayed immune recovery was a potential risk factor, the recovery of the CD3(+), CD4(+), CD8(+) and CD19(+) cells was related retrospectively to genotypic detected resistance development in three pediatric patients with ganciclovir (GCV)-resistant human cytomegalovirus (HCMV)-infection out of 79 receiving allogeneic PBSCT. Selected control groups consisted of HCMV-seronegative patients without any infection (A, n = 8), asymptomatic infected patients with viral leuko- and plasmaDNAemia (B, n = 4) and patients with HCMV-disease (pneumonia) (C, n = 3). Patient No. 1 with very early resistance development exhibited a rapid immune recovery with higher T cell counts than in group A. Immune recovery of patient No. 2 was delayed, as also observed in groups B and C. Patient No. 3 showed an immune recovery comparable to group A. Resistance developed before (No. 2) or during (Nos 1 and 3) the recovery of the relevant CD3(+), CD4(+), CD8(+) lymphocytes. GCV-resistance development did not necessarily coincide with delayed immune recovery, but appeared in all three cases in the early phase of immune recovery (range: day +44 to day +95). Therefore, children seem to be at special risk for resistance development in the early phase after transplantation before immune cells have recovered. These results suggest that GCV treatment of an HCMV infection in the early posttransplant phase of children after T cell-depleted PBSCT/BMT should promote more stringent resistance screening.

Inhibition of clinical isolates of human cytomegalovirus and varicella zoster virus by PNU-183792, a 4-oxo-dihydroquinoline

The susceptibility of human cytomegalovirus (CMV) and varicella zoster virus (VZV) clinical isolates to PNU-183792, a 4-oxo-dihydroquinoline, was examined. The antiviral potency of PNU-183792, a non-nucleoside inhibitor, was compared to the licensed nucleoside inhibitors ganciclovir and acyclovir using plaque reduction and virus yield reduction assays. PNU-183792 was as potent against CMV as ganciclovir and was superior in potency to acyclovir against VZV. PNU-183792 represents a new class of non-nucleoside inhibitors of human herpesviruses.

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.

Prospective validation of quantitative polymerase chain reaction for management of cytomegalovirus disease in solid-organ transplant patients

This study evaluates the utility of quantitative polymerase chain reaction (QPCR) to determine duration of treatment of transplant patients with human cytomegalovirus (HCMV) disease. Eighteen patients with HCMV disease were prospectively evaluated and followed for recurrence using a QPCR assay. We used plasma samples from which nucleic acid was extracted. Quantification was determined by using an internal standard that contained the same primer sequences as for HCMV. During treatment, weekly QPCR assays were performed. Patients were treated with HCMV immunoglobulin-G for a finite period, but intravenous ganciclovir was continued until less than 100 viral copies (vc) per mL was detectable. After cessation of therapy, patients were followed for 6 months with monthly clinical assessment and QPCR. No patient developed recurrence of HCMV at a mean follow-up of 16 months. This preliminary study suggests that the use of QPCR to assess viral load is useful in deciding the length of HCMV treatment with ganciclovir but requires further randomized validation.

Diagnosis and treatment approaches of CMV infections in adult patients

BACKGROUND

Cytomegalovirus (CMV) infections are very common in the general population. Clinical CMV disease, particularly CMV pneumonitis, greatly impacts the morbidity and mortality of immunosuppressed patients.

OBJECTIVE

To present an overview of the basic aspects of the biology, epidemiology, and clinical features of CMV in relation to the available diagnostic and therapeutic approaches in adult patients.

METHODS

Review of the medical literature on cytomegalovirus infection and disease in adult hosts, with a focus on approaches to diagnosis and treatment of CMV respiratory disease in immunosuppressed hosts.

CONCLUSIONS

Cytomegalovirus infections are likely to remain a significant cause of morbidity and mortality among immunosuppressed patients. Important aspects of the biological events underlying the transition from infection to clinical disease remain unclear. Despite that, considerable progress has been made in the design of improved diagnostic techniques and the development of antiviral agents. Preventive and particularly preemptive therapeutic approaches demand further technical improvements in diagnostic testing. At present, the emphasis in the search for improved diagnostic testing rests on the development of quantitative methods for early detection of the increased viral replicative activity that presumably precedes the onset of CMV disease in infected individuals.

CNS manifestations of cytomegalovirus infections: diagnosis and treatment

Cytomegalovirus (CMV) infection of the CNS occurs most commonly in patients with severe immunosuppression such as those with advanced HIV infection (i.e. AIDS) or those who have undergone bone marrow or solid organ transplantation. Immunocompetent patients are affected very rarely. The infection of the CNS may affect the brain (diffuse encephalitis, ventriculoencephalitis, cerebral mass lesions) or the spinal cord (transverse myelitis, polyradiculomyelitis). Diagnosis is very difficult and should be based on clinical presentation, results of imaging and virological markers. The most specific diagnostic tool is the detection of CMV DNA by polymerase chain reaction in the CSF. Treatment should be initiated promptly if CMV infection is suspected. Antiviral therapy consists of intravenous ganciclovir, intravenous foscarnet or a combination of both. Cidofovir is the treatment of second choice. Patients who experience clinical improvement or stabilisation during induction therapy should be given maintenance therapy. After immune reconstitution (in HIV-positive patients) or discontinuation of immunosuppressive therapy (in transplant recipients), maintenance therapy may be stopped. Despite therapy, the prognosis for long-term survival is very poor, especially in patients with AIDS.

Home Health Care for the Kidney and Kidney-Pancreas Transplant Recipient

Kidney transplantation has been a part of the world medical scene for more than 45 years and simultaneous kidney-pancreas transplantation for more than 20 years. Improvements in medical techniques, immunosuppressive therapy, and expansion of patient eligibility have led to a population more in need of home health services than ever before. The home health needs of the population range from typical chronic health care needs to issues specifically associated with immunosuppression.

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.

Direct targeting of human cytomegalovirus protein kinase pUL97 by kinase inhibitors is a novel principle for antiviral therapy

The protein kinase pUL97, encoded by human cytomegalovirus (HCMV), is an important determinant of virus replication. Recently, indolocarbazoles were identified as a class of substances that inhibit the pUL97 kinase activity in vitro. In parallel, it was shown that indolocarbazoles interfere with HCMV replication; however, the causal relationship between inhibition of pUL97 kinase activity and virus replication has not been clarified. Here evidence is provided that indolocarbazole-mediated inhibition of virus replication is a direct result of diminished pUL97 protein kinase activity. In cell culture infections, a strong and selective antiviral activity was measured with respect to several strains of HCMV in contrast with other related or non-related viruses. For fine quantification, recombinant HCMVs expressing green fluorescent protein were used, demonstrating the high sensitivity towards compounds NGIC-I and Gö6976. Interestingly, a ganciclovir-resistant virus mutant (UL97-M460I) showed increased sensitivity to both compounds. Supporting this concept, transfection experiments with cloned pUL97 revealed that ganciclovir-resistant mutants were characterized by reduced levels of autophosphorylation compared with wild-type and possessed particularly high sensitivity to indolocarbazoles. Moreover, the Epstein-Barr virus-encoded homologous kinase, BGLF4, which showed a similar pattern of autophosphorylation and ganciclovir phosphorylation activities, was not inhibited. Importantly, a cytomegalovirus deletion mutant, lacking a functional UL97 gene and showing a severe impairment of replication, was completely insensitive to indolocarbazoles. Thus, our findings indicate that a specific block in the activity of pUL97 is the critical step in indolocarbazole-mediated inhibition of virus replication and that pUL97 might be targeted very efficiently by a novel antiviral therapy.

Reassessing the impact of cytomegalovirus infection in kidney and kidney-pancreas transplantation

New antiviral agents and practice guidelines have been implemented to address cytomegalovirus (CMV) infection in organ transplantation. We hypothesized that such measures would reduce rates of symptomatic CMV infection, CMV disease, and CMV seroconversion and associated complications in renal transplant and simultaneous pancreas-kidney transplant recipients. We analyzed the impact of CMV in 1,424 renal transplant and simultaneous pancreas-kidney transplant recipients, transplanted at our center between January 1, 1994 and June 30, 1999. Most patients received quadruple sequential immunosuppression with high-dose acyclovir (800 mg four times daily) for 12 weeks as prophylaxis. High-risk patients (donor CMV-positive/recipient CMV-negative) received ganciclovir (500 to 1,000 mg three times daily) beginning in 1998, again for 12 weeks. One hundred and one renal transplant (9.0%) and 40 simultaneous pancreas-kidney transplant (13.4%) recipients experienced symptomatic CMV infection or CMV disease. Donor CMV-positive/recipient CMV-negative patients had the greatest rates of CMV infection or CMV disease (25.2%; P = 0.0001 versus all other categories). The impact of CMV on outcomes was evaluated in a proportional hazards model. Symptomatic CMV infection or CMV disease increased the risk for subsequent rejection (relative risk, 2.11; P = 0.003) and non-CMV infection (relative risk, 2.24; P = 0.001). To determine if the effects of ganciclovir were masked by pre-1998 data, CMV infection and CMV disease rates for ganciclovir-treated patients (n = 62) were censored at 1 year and compared with acyclovir-treated patients (n = 287). Ganciclovir was associated with trends toward lower rates of infection and disease. It also delayed the time to infection or disease. Serologic testing in high-risk patients also showed late seroconversion, with 20% of patients seroconverting by 6 months, 12 weeks after the prophylaxis period. These data suggest that despite better prophylaxis strategies, CMV remains an important pathogen in renal transplant and simultaneous pancreas-kidney transplant recipients. This finding may require reassessment of prophylaxis strategies and the development of alternative or novel anti-CMV regimens.

Prevention and management of CMV-related problems after hematopoietic stem cell transplantation

Prevention and management of human cytomegalovirus (CMV) infection after hematopoietic stem cell transplantation has improved substantially in the past decade. However, with this improvement, there is increased complexity in deciding which diagnostic tests, treatment strategies and immunologic assessments are optimal for different patient populations. The purpose of this review is to address certain practical problems that commonly arise and suggest a suitable approach to management that should have wide applicability.

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.

Resistance in viruses other than HIV

The aim of this brief paper is to summarize the ways in which viruses develop resistance to currently licensed anti-viral drugs and to comment on their clinical relevance. Specific examples will be chosen to emphasize basic principles of the development of resistance and readers are referred elsewhere to a summary of resistance in HIV that follows the same principles.

Response-oriented preemptive therapy against cytomegalovirus disease with low-dose ganciclovir: a prospective evaluation

BACKGROUND

Preemptive therapy against cytomegalovirus (CMV) disease has succeeded in reducing the incidence of CMV disease, but the toxicity of ganciclovir remains problematic.

METHODS

We prospectively evaluated the efficacy and toxicity of a preemptive protocol with ganciclovir at a reduced initial dose in 40 patients who achieved engraftment after allogeneic hematopoietic stem cell transplantation.

RESULTS

Twenty-three (58%) patients had high-risk features, including transplant from an HLA-mismatched or unrelated donor, or associated acute graft-versus-host disease. CMV antigenemia assay was performed weekly, and ganciclovir was started in a risk-adapted manner, in which the initial dose of ganciclovir was fixed at 5 mg/kg/d and then adjusted based on the results of a weekly CMV antigenemia assay. In this protocol, 23 (58%) patients demonstrated positive antigenemia, and 19 (48%) received a preemptive administration of ganciclovir. Only one patient had CMV disease in the gastrointestinal system, which was successfully treated with a regular therapeutic dose of ganciclovir. Consequently, the total dose of ganciclovir was significantly less than that in a previous protocol using the conventional double dose (5 mg/kg twice daily) of ganciclovir (134 mg/kg vs. 190 mg/kg on average, P=0.046). There were no significant toxicities attributed to ganciclovir, except for neutropenia <0.5 x 109/L, which developed in three patients for 3, 4, and 14 days, respectively, with granulocyte colony-stimulating factor support.

CONCLUSION

Preemptive therapy with a low initial dose of ganciclovir appeared to be effective even in high-risk patients. Further randomized controlled trial is warranted.

Pattern and persistence of the epitope-specific IgM response against human cytomegalovirus in renal transplant patients

The humoral immune response against human cytomegalovirus (HCMV) was evaluated in immunocompromised patients by Western blotting (WB) based on recombinant viral envelope (gB and gH) and tegument (pp150 and pp65) proteins. Three groups of patients were investigated: (a) 74 renal transplant recipients; (b) 24 hemodialysis patients, both groups without clinical evidence of viral infections; and (c) 19 renal transplant patients with manifest HCMV infections. The results obtained suggest that (i) the WB is considerably more sensitive, recognizing the HCMV-specific IgM response rather than the enzyme-linked immunosorbent assays. An IgM response was detected in one-third of all clinically asymptomatic renal patients. (ii) The virus-specific IgM response is primarily directed against the pp150 epitope. (iii) In patients with clinically manifest HCMV disease, additional IgM reactivities are most frequently directed against the glycoprotein B epitope. (iv) The severity of HCMV infections correlates with the extent of the IgM antibody response, i.e. with the number of specific epitopes involved. (v) After transplantation, IgM reactivity and its epitope-specific pattern persist for years.

Virus population dynamics, fitness variations and the control of viral disease: an update

Viral quasispecies dynamics and variations of viral fitness are reviewed in connection with viral disease control. Emphasis is put on resistance of human immunodeficiency virus and some human DNA viruses to antiviral inhibitors. Future trends in multiple target antiviral therapy and new approaches based on virus entry into error catastrophe (extinction mutagenesis) are discussed.

Ganciclovir: an update of its use in the prevention of cytomegalovirus infection and disease in transplant recipients

Ganciclovir is a nucleoside guanosine analogue which incorporates ganciclovir triphosphate (the active moiety) into DNA during elongation, thereby inhibiting viral replication. Comparative studies of pre-emptive and prophylactic ganciclovir therapies in bone marrow transplant (BMT) recipients have shown similar rates of cytomegalovirus (CMV) infection, disease and patient mortality. Long term prophylaxis with either oral, or sequential intravenous/oral, ganciclovir has shown efficacy in renal allograft recipients, including high risk patients or those receiving antilymphocyte antibody therapy. A preliminary study indicates that ganciclovir is more efficacious than aciclovir in paediatric patients. Both oral and intravenous prophylactic ganciclovir regimens have shown efficacy compared with no antiviral treatment in lung transplant recipients; initial reports have shown similar efficacy between pre-emptive and prophylactic ganciclovir. Oral ganciclovir monotherapy is as efficacious as sequential intravenous/oral ganciclovir therapy in liver transplant recipients. Pre-emptive treatment was equally as effective as long term ganciclovir prophylaxis in high risk patients. Ganciclovir prophylaxis for 4 weeks appears ineffective in heart allograft recipients treated with antithymocyte globulin. Long term sequential intravenous/ oral ganciclovir therapy has shown greater efficacy in preventing CMV disease than sequential ganciclovir/aciclovir therapy. in these patients. Initial reports indicate that pre-emptive therapy may be beneficial in this patient group. although this remains to be determined. Ganciclovir in therapeutic dosage regimens generally has acceptable tolerability with adverse effects usually of a haematological or neurological nature. Neutropenia, thrombocytopenia and anaemia are the primary dose-limiting toxicities associated with ganciclovir therapy. Overall, neutropenia occurs less frequently with administration of oral ganciclovir than with intravenous ganciclovir. Monitoring of renal function is recommended as serum creatinine levels may rise during ganciclovir therapy. In addition, ganciclovir prophylaxis appears more cost effective than the majority of other currently available therapies for CMV with oral ganciclovir more cost effective than intravenous ganciclovir. In conclusion, it is unlikely that a single strategy will be able to be applied to all transplant patients for the prevention of CMV disease. An optimal strategy will probably be arisk-adapted approach. Prophylactic treatment with ganciclovir appears the best strategy to implement in high risk patients: oral ganciclovir formulations may be best employed where lower toxicity is required. Pre-emptive treatment with ganciclovir appears most efficacious in patients identified as lower risk or, in the case of BMT recipients, where lower toxicity may be desirable. Ganciclovir remains an important therapeutic option for the prevention and treatment of CMV disease in transplant recipients.

Risk factors and impact of cytomegalovirus disease in simultaneous pancreas-kidney transplantation

BACKGROUND

The relevance of cytomegalovirus (CMV) in simultaneous pancreas kidney (SPK) transplant recipients in the modern era of immunosuppression and antiviral therapeutics is largely unquantified. We sought to determine the risk factors of CMV disease and its impact on SPK transplant outcomes in recipients all receiving a consistent regime of maintenance immunosuppression and CMV prophylaxis.

METHODS

This is a retrospective, single center study of 100 consecutive SPK transplant recipients. All received maintenance immunosuppression with mycophenolate mofetil, tacrolimus, and prednisone. CMV prophylaxis consisted of a short course of parenteral gancyclovir followed by oral gancyclovir. Recipients at high-risk (D+/R-) for CMV also received CMV hyperimmune globulin. Multivariate analysis of risk factors for CMV disease and risk factors for adverse outcomes in SPK transplantation were determined. The effect of duration of prophylaxis on timing and severity of CMV disease in high-risk (D+/R-) SPK transplant recipients was also evaluated.

RESULTS

The actual 1-year rate of CMV disease was 17.0% (12.0% noninvasive, 5.0% tissue invasive); and according to donor and recipient CMV serological status was: D-/R+: 0%; D-/R-: 2.8%; D+/R+: 25.6%; and D+/R-: 40.6%. Multivariate analysis showed transplantation of organs from a donor with positive CMV serology to be predictive of CMV disease with a relative risk of 63.37 (P=0.0052). In the high-risk (D+/R-) subgroup, the duration of prophylactic therapy delayed onset of CMV disease, but had minimal effect on severity. Invasive CMV disease was an independent predictor of mortality but did not decrease kidney or pancreas allograft survival.

CONCLUSIONS

Outcomes of SPK transplantation have improved in the current era of modern immunosuppression, yet CMV remains an important pathogen. The serological status of the organ donor and the duration of CMV prophylaxis are predictive of who and when CMV disease may occur. Nevertheless, new strategies that reduce risk and severity of CMV disease are still needed.