Quantitation of cytomegalovirus in the blood of liver transplant recipients

Cytomegalovirus treatment options in immunocompromised patients

Cytomegalovirus (CMV) infection was recognised in congenitally infected infants in the first half of the 20th century. Following the increased use of immunosuppressive regimens for bone marrow and solid organ transplantation, various manifestations of CMV disease were recognised. Milder symptoms included fever, anorexia and malaise but severe symptoms included pneumonitis, hepatitis, gastrointestinal ulceration, choreoretinitis and encephalopathy, all with a high morbidity or mortality. With the onset of the AIDS epidemic, manifestations of CMV became evident, predominantly retinitis. Ganciclovir used intravenously has been the principal anti-CMV agent investigated. However, ganciclovir has problems with suboptimal efficacy, toxicity, poor oral bioavailability and evolution of resistant strains. Additional studies have been performed on foscarnet and cidofovir, although the use of both have been limited by their nephrotoxicity. Combination therapy with ganciclovir and foscarnet for resistant strains has been used. There are promising newer drugs like the methylenecyclopropane nucleoside analogues and benzimidazole. The most novel compound is the antisense oligonucleotide fomivirsen that has been evaluated principally in CMV retinitis. The role of immunotherapy with either immunoglobulin prophylaxis or the novel adoptive immunotherapy needs further evaluation.

Evaluation of the COBAS AMPLICOR CMV MONITOR test for detection of viral DNA in specimens taken from patients after liver transplantation

Detection of cytomegalovirus (CMV) DNA in blood by PCR is a sensitive method for the detection of infection in patients posttransplantation. The test, however, has low specificity for the identification of overt CMV disease. Quantitative CMV PCR has been shown to overcome this shortcoming. The COBAS AMPLICOR CMV MONITOR test was evaluated by using consecutive serum and peripheral blood mononuclear cell (PBMN) samples from liver transplant patients. Twenty-five patients had CMV viremia (by shell vial cell culture assay) and/or tissue-invasive disease (by biopsy); 20 had no active infection. A total of 262 serum and 62 PBMN specimens were tested. Of 159 serum specimens from patients with overt CMV infection, the COBAS assay detected CMV DNA in 21 patients (sensitivity, 84%). Only 1 of 103 samples from patients with no evidence of active infection had detectable CMV DNA (341 copies/ml). By comparison of 62 matching serum and PBMN samples by the same assay, 12 PBMN samples were exclusively positive, whereas only 2 serum samples were exclusively positive (P < 0.05). At the time of clinical CMV infection, viral copy numbers were higher in PBMNs than serum from four of five patients. The COBAS AMPLICOR CMV MONITOR test is a sensitive and specific test for the quantitative detection of CMV DNA in blood. Clinical applications of the assay will require further validation with samples from a larger population of transplant patients.

New strategies for prevention and therapy of cytomegalovirus infection and disease in solid-organ transplant recipients

In the past three decades since the inception of human organ transplantation, cytomegalovirus (CMV) has gained increasing clinical import because it is a common pathogen in the immunocompromised transplant recipient. Patients may suffer from severe manifestations of this infection along with the threat of potential fatality. Additionally, the dynamic evolution of immunosuppressive and antiviral agents has brought forth changes in the natural history of CMV infection and disease. Transplant physicians now face the daunting task of recognizing and managing the changing spectrum of CMV infection and its consequences in the organ recipient. For the microbiology laboratory, the emphasis has been geared toward the development of more sophisticated detection assays, including methods to detect emerging antiviral resistance. The discovery of novel antiviral chemotherapy is an important theme of clinical research. Investigations have also focused on preventative measures for CMV disease in the solid-organ transplant population. In all, while much has been achieved in the overall management of CMV infection, the current understanding of CMV pathogenesis and therapy still leaves much to be learned before success can be claimed.

Determination of cytomegalovirus DNA load for monitoring of cytomegalovirus disease and antiviral treatment in solid organ transplant patients, comparing limiting-dilution PCR and hybrid capture assay with cytomegalovirus isolation

OBJECTIVE: To improve the identification of patients at risk of developing cytomegalovirus (CMV) disease. MATERIALS AND METHODS: In a prospective study of 50 kidney or liver transplant patients who developed fever, 133 EDTA blood samples were analyzed, using two tests to measure CMV DNA: a 10-fold limiting dilution of an extract of 2 million leukocytes for CMV PCR, and a CMV hybrid capture assay. Both tests were compared with virus isolation, using an equivalent amount of leukocytes as a base for all three tests. RESULTS: The limiting-dilution CMV PCR and the hybrid capture assay presented relatively similar changes of sensitivity and specificity at different CMV DNA concentrations. The kinetics of the positive and negative predictive values were also comparable. A higher CMV DNA load corresponded to an increased risk of developing CMV disease. Furthermore, an increase in the endpoint dilution of a positive CMV PCR also corresponded to more severe disease. After antiviral treatment, the CMV PCR decreased by at least 100-fold (2 log10) in 10 cases and by 10-fold (1 log10) in five cases. Thus, there was a decrease in 15 of 18 (83%) patients. Similarly, with the hybrid capture assay, the amount of CMV DNA decreased about 100-fold in five patients and decreased by about 0.5 genome equivalents in five cases, i.e. in 10 of 12 (83%) patients. CONCLUSION: Both methods proved clinically useful for detecting patients at risk of developing CMV disease and for monitoring antiviral treatment in solid organ transplant patients.

Cytomegalovirus viremia: risk factor for allograft cirrhosis after liver transplantation for hepatitis C

BACKGROUND

Despite recent advances in diagnosis and treatment, cytomegalovirus (CMV) infection continues to be a common cause of morbidity in liver transplant (LT) recipients. Because CMV infection suppresses cell-mediated immunity, which seems to be important in neutralizing hepatitis C virus (HCV) infection, we assessed the impact of CMV infection on histopathological HCV recurrence after LT.

METHODS

The study group was comprised of 43 consecutive LT recipients with at least 6 months of histologic follow-up. Group 1 consisted of the 8 patients who developed CMV viremia after LT; group 2 comprised the 35 patients without CMV viremia. There was no significant difference with regard to age, initial immunosuppression, incidence of rejection, distribution of HCV genotypes, or mean follow-up between the groups. Semiquantitative histopathologic assessment of allograft hepatitis was performed using the Knodell's score.

RESULTS

The mean total Knodell score of the final allograft biopsy was significantly greater in group 1 patients (P=0.016), with most of the difference due to periportal/bridging necrosis (P=0.009) and lobular activity subitem (P=0.01) scores. Half of the CMV viremic patients eventually developed allograft cirrhosis as compared with 11% of the CMV-negative patients (P=0.027). Accordingly, the cirrhosis-free actuarial survival by Kaplan-Meier estimates was significantly diminished in the CMV viremic patients. Glycoprotein B genotype analysis of CMV isolates revealed no significant differences between patients who did and those who did not develop allograft cirrhosis.

CONCLUSIONS

After LT for chronic HCV, patients who develop CMV viremia incur a significantly greater risk of severe HCV recurrence.

Comparison of a new quantitative cytomegalovirus DNA assay with other detection methods

OBJECTIVE

We assessed a new cytomegalovirus (CMV) DNA hybridization assay. We also compared the assay with other currently used assays to determine its use in the early detection of active CMV infection.

PATIENTS AND METHODS

Sequential whole blood samples collected from 109 patients who had undergone orthotopic liver transplantation were tested using the Murex hybrid capture system, cell culture, antigen detection, and serology. Liver biopsies performed during the study period for graft dysfunction in 84 patients were examined for histological features of CMV hepatitis. The biopsies were also immunostained for the presence of CMV antigens.

RESULTS

Fifteen patients developed clinically significant CMV disease (CMV syndrome in six patients and CMV hepatitis in nine patients, including two patients with disseminated CMV disease). In all 15, CMV DNA was detected by the hybrid capture assay between 1 and 20 days before other CMV assays. Fourteen of the 15 patients had CMV DNA levels greater than 50 pg/ml; the other patient had a value of 48 pg/ml. Of the remaining 94 patients with no evidence of CMV disease, 86 were negative by the hybrid capture assay and 8 were positive; all but one patient had values less than 50 pg/ml. DNA levels fell rapidly in all patients during antiviral therapy.

CONCLUSION

Unlike conventional CMV detection methods, this hybridization assay is an early predictor of clinically significant CMV infection after liver transplantation and also provides quantitation of viral load, allowing monitoring of antiviral therapy.

Patterns of viremia in liver transplant recipients with symptomatic cytomegalovirus infection

Cytomegalovirus (CMV) titer in blood seems to be the principal determinant of clinical symptoms in immunosuppressed patients. We have developed an assay for quantitation of CMV DNA in serum. The assay requires the coamplification by polymerase chain reaction (PCR) of extracted serum DNA with 1000 molecules of mutated internal standard DNA, and then an ELISA detection system. We examined 133 paired buffy coats and sera from 15 patients with symptomatic infection. Sera were examined by quantitative PCR, and buffy coats were examined by qualitative PCR (with a detection threshold of approximately 40 copies per 150,000 cells). Serum viral titers peaked during the seventh week after transplant (median day 40, range 26-58) at about the time of symptom onset. Mean viral titer measured during the seventh week was 1.2 x 10(5) copies per milliliter of serum (standard error 6.5 x 10(4). Buffy-coat PCR results were generally concordant with results of serum PCR (overall concordance 103/133=77.4%). Serum CMV titer fell, as symptoms resolved with reduction of immunosuppression and specific antiviral therapy. High titers and poor response to antiviral therapy were observed in the context of excessive immunosuppression and bacterial sepsis. Measurement of serum CMV titer may be useful for the management of immunosuppressed transplant recipients, and provides a tool for the better understanding of factors that enhance or inhibit viral replication.