Evaluation of the Digene Hybrid Capture System for detection and quantitation of human cytomegalovirus viremia in human immunodeficiency virus-infected patients

Clinical utility of viral load in management of cytomegalovirus infection after solid organ transplantation

The negative impact of cytomegalovirus (CMV) infection on transplant outcomes warrants efforts toward improving its prevention, diagnosis, and treatment. During the last 2 decades, significant breakthroughs in diagnostic virology have facilitated remarkable improvements in CMV disease management. During this period, CMV nucleic acid amplification testing (NAT) evolved to become one of the most commonly performed tests in clinical virology laboratories. NAT provides a means for rapid and sensitive diagnosis of CMV infection in transplant recipients. Viral quantification also introduced several principles of CMV disease management. Specifically, viral load has been utilized (i) for prognostication of CMV disease, (ii) to guide preemptive therapy, (iii) to assess the efficacy of antiviral treatment, (iv) to guide the duration of treatment, and (v) to indicate the risk of clinical relapse or antiviral drug resistance. However, there remain important limitations that require further optimization, including the interassay variability in viral load reporting, which has limited the generation of standardized viral load thresholds for various clinical indications. The recent introduction of an international reference standard should advance the major goal of uniform viral load reporting and interpretation. However, it has also become apparent that other aspects of NAT should be standardized, including sample selection, nucleic acid extraction, amplification, detection, and calibration, among others. This review article synthesizes the vast amount of information on CMV NAT and provides a timely review of the clinical utility of viral load testing in the management of CMV in solid organ transplant recipients. Current limitations are highlighted, and avenues for further research are suggested to optimize the clinical application of NAT in the management of CMV after transplantation.

Diagnosis and management of human cytomegalovirus infection in the mother, fetus, and newborn infant

Human cytomegalovirus (HCMV) is the leading cause of congenital viral infection and mental retardation. HCMV infection, while causing asymptomatic infections in most immunocompetent subjects, can be transmitted during pregnancy from the mother with primary (and also recurrent) infection to the fetus. Hence, careful diagnosis of primary infection is required in the pregnant woman based on the most sensitive serologic assays (immunoglobulin M [IgM] and IgG avidity assays) and conventional virologic and molecular procedures for virus detection in blood. Maternal prognostic markers of fetal infection are still under investigation. If primary infection is diagnosed in a timely manner, prenatal diagnosis can be offered, including the search for virus and virus components in fetal blood and amniotic fluid, with fetal prognostic markers of HCMV disease still to be defined. However, the final step for definite diagnosis of congenital HCMV infection is detection of virus in the blood or urine in the first 1 to 2 weeks of life. To date, treatment of congenital infection with antiviral drugs is only palliative both prior to and after birth, whereas the only efficacious preventive measure seems to be the development of a safe and immunogenic vaccine, including recombinant, subunit, DNA, and peptide-based vaccines now under investigation. The following controversial issues are discussed in the light of the most recent advances in the field: the actual perception of the problem; universal serologic screening before pregnancy; the impact of correct counseling on decision making by the couple involved; the role of prenatal diagnosis in ascertaining transmission of virus to the fetus; the impact of preconceptional and periconceptional infections on the prevalence of congenital infection; and the prevalence of congenitally infected babies born to mothers who were immune prior to pregnancy compared to the number born to mothers undergoing primary infection during pregnancy.

Diagnosis and management of human cytomegalovirus infection in the mother, fetus, and newborn infant

Human cytomegalovirus (HCMV) is the leading cause of congenital viral infection and mental retardation. HCMV infection, while causing asymptomatic infections in most immunocompetent subjects, can be transmitted during pregnancy from the mother with primary (and also recurrent) infection to the fetus. Hence, careful diagnosis of primary infection is required in the pregnant woman based on the most sensitive serologic assays (immunoglobulin M [IgM] and IgG avidity assays) and conventional virologic and molecular procedures for virus detection in blood. Maternal prognostic markers of fetal infection are still under investigation. If primary infection is diagnosed in a timely manner, prenatal diagnosis can be offered, including the search for virus and virus components in fetal blood and amniotic fluid, with fetal prognostic markers of HCMV disease still to be defined. However, the final step for definite diagnosis of congenital HCMV infection is detection of virus in the blood or urine in the first 1 to 2 weeks of life. To date, treatment of congenital infection with antiviral drugs is only palliative both prior to and after birth, whereas the only efficacious preventive measure seems to be the development of a safe and immunogenic vaccine, including recombinant, subunit, DNA, and peptide-based vaccines now under investigation. The following controversial issues are discussed in the light of the most recent advances in the field: the actual perception of the problem; universal serologic screening before pregnancy; the impact of correct counseling on decision making by the couple involved; the role of prenatal diagnosis in ascertaining transmission of virus to the fetus; the impact of preconceptional and periconceptional infections on the prevalence of congenital infection; and the prevalence of congenitally infected babies born to mothers who were immune prior to pregnancy compared to the number born to mothers undergoing primary infection during pregnancy.

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.

A randomised trial comparing cytomegalovirus antigenemia assay vs screening bronchoscopy for the early detection and prevention of disease in allogeneic bone marrow and peripheral blood stem cell transplant recipients

Preemptive antiviral therapy is often employed for CMV prevention following allogeneic BMT. Two common strategies are a screening bronchoscopy for CMV post-BMT or regular CMV antigenemia testing with ganciclovir administration for a positive result. In a randomised trial, we prospectively compared the efficacy of these two preemptive strategies. Consecutive patients were randomised to either a bronchoscopy for CMV on day 35 post BMT or weekly CMV antigenemia testing. If the bronchoscopy was positive for CMV, patients received preemptive ganciclovir for 8-10 weeks. If the antigenemia was positive for CMV, patients received a minimum of 2 weeks of preemptive ganciclovir. The primary endpoint was the development of active CMV disease. One hundred and eighteen allogeneic BMT patients were enrolled (60 in the antigenemia arm and 58 in the bronchoscopy arm). The two groups were comparable with respect to baseline demographic data, underlying disease, conditioning regimen, and immunosuppression. Active CMV disease developed in 7/58 (12.1%) patients in the bronchoscopy arm vs 1/60 patients (1.7%) in the CMV antigenemia arm (P = 0.022). Based on the screening test, 13.8% of patients received preemptive ganciclovir in the bronchoscopy arm vs 48.3% of patients in the antigenemia arm (P < 0.001). There was no significant difference in the rate of graft-versus-host disease, bacteremia, invasive fungal infections or mortality between the two groups. Preemptive therapy based on regular CMV antigenemia monitoring is superior to screening bronchoscopy for the prevention of CMV disease after allogeneic BMT.

Quantification of cytomegalovirus (CMV) viral load by the hybrid capture assay allows for early detection of CMV disease in lung transplant recipients

BACKGROUND

We prospectively compared the hybrid capture system (HCS) assay with conventional cell culture and shell vial assay for the detection of cytomegalovirus (CMV) infection and disease in the lung transplant population.

METHODS

Between January 1999 and February 2000, 34 lung transplant patients at Loyola University Medical Center, who were considered to be at risk for CMV disease, underwent surveillance testing for CMV cell culture, shell vial assay and HCS assay according to a pre-determined schedule. In addition, bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsy were performed at regular intervals and for clinical indications. All BAL samples were sent for CMV cultures and biopsy specimens were analyzed for histopathologic evidence of CMV by immunoperoxidase staining using antibody to early immediate nuclear antigen.

RESULTS

Ten patients developed CMV disease/syndrome during the course of the study. The sensitivity, specificity, positive predictive value and negative predictive value were >90% for the HCS assay. The sensitivity of the HCS assay (90%) was statistically significantly higher than the sensitivity of either the SV assay (40%) or the cell culture (50%). In addition, the HCS assay was able to detect CMV 50 +/- 67 days prior to clinical evidence of CMV disease and an average of 36 days prior to the other detection techniques.

CONCLUSION

The HCS assay is a sensitive diagnostic technique able to reliably detect CMV disease earlier than other diagnostic methods in the lung transplant population. Future studies may be able to evaluate whether pre-emptive anti-viral therapy targeted to specific viral loads using the HCS assay will be beneficial in preventing morbidity associated with CMV disease.

Increased human cytomegalovirus (HCMV) DNA load in peripheral blood leukocytes after lung transplantation correlates with HCMV pneumonitis

BACKGROUND

Human cytomegalovirus (HCMV) reactivation and disease remain relatively common in lung transplant recipients (LTR) despite the use of ganciclovir prophylaxis protocols for all HCMV at-risk patients. The specific aims of this study were to (1) describe the HCMV DNA viral load in the peripheral blood leukocytes (PBL) of a cohort of LTR during the first 6 months after lung transplantation; (2) prospectively determine whether HCMV DNA viral load predicts episodes of HCMV pneumonitis in LTR; and (3) study the effect of ganciclovir on HCMV viral load.

METHODS

Competitive polymerase chain reaction using an internal standard and fluorometric detection were used to quantitate HCMV DNA in the PBL of a cohort of 26 LTR monthly for the first 6 months after transplantation (145 samples). All patients were treated with standard triple immunosuppression, and ganciclovir prophylaxis was given to all at-risk LTR (donor or recipient HCMV seropositive) for at least 8 weeks after transplantation.

RESULTS

Thirteen episodes of histopathologically proven HCMV pneumonitis in nine subjects occurred during follow-up with a wide intra- and intersubject variation in the HCMV DNA PBL levels. HCMV detection had a sensitivity of 92% and specificity of 76% for HCMV pneumonitis (negative likelihood ratio, 9.5), whereas greater than 10-fold increases in HCMV DNA load had a specificity of 93% and sensitivity of 67% (positive likelihood ratio, 11). HCMV DNA detection had an adjusted odds ratio for HCMV pneumonitis of 107 (95% confidence interval, 14-821; P<0.005). In those with detectable HCMV DNA in PBL (n=44), HCMV DNA levels were 4.4 (95% confidence interval, 1.2-16.8) times higher in those with HCMV pneumonitis than in those without HCMV pneumonitis. Although ganciclovir treatment was very effective in treating HCMV pneumonitis and suppressing HCMV DNA levels, thrice weekly ganciclovir prophylaxis only partially controlled HCMV DNA levels and did not eliminate HCMV pneumonitis risk as three patients developed HCMV pneumonitis while on this regimen.

CONCLUSIONS

HCMV DNA detection, absolute levels, and relative change from baseline in the PBL of LTR correlate with HCMV pneumonitis episodes and may be a useful intermediate outcome measure of the efficacy of ganciclovir prophylaxis and treatment strategies.

Evaluation of the Murex CMV DNA Hybrid Capture assay (version 2.0) for early diagnosis of cytomegalovirus infection in recipients of an allogeneic stem cell transplant

Early diagnosis of CMV infection based on sensitive diagnostic assays has helped to reduce CMV-related mortality after allogeneic stem cell transplantation (SCT). In this study, the commercialized Murex CMV DNA Hybrid Capture assay (version 2.0) (HCS) was prospectively compared to an in-house CMV-DNA PCR assay from whole blood in patients after allogeneic stem cell transplantation. Overall, a high concordance between HCS and PCR was documented (kappa = 0.686; n = 385). The HCS assay was found to be as sensitive as the PCR indicating active CMV infection at a median of 35 and 34 days after transplantation, respectively. None of the HCS-negative patients developed CMV-related symptoms (negative predictive value 100%). Declining CMV DNA load in the blood was found to be an indicator for effective antiviral therapy, whereas persistence of a high viral load was associated with fatal CMV disease. In conclusion, the Hybrid Capture CMV DNA assay (v 2.0) allows early diagnosis of CMV infection after allogeneic SCT and assessment of the efficacy of antiviral therapy.

Diagnostic virology

Diagnostic virology has now entered the mainstream of medical practice. Multiple methods are used for the laboratory diagnosis of viral infections, including viral culture, antigen detection, nucleic acid detection, and serology. The role of culture is diminishing as new immunologic and molecular tests are developed that provide more rapid results and are able to detect a larger number of viruses. This review provides specific recommendations for the diagnostic approach to clinically important viral infections.

Comparison of three assays for cytomegalovirus detection in AIDS patients at risk for retinitis

The purpose of this study was to determine the sensitivity and specificity of three different methods of cytomegalovirus (CMV) detection for AIDS patients at risk for CMV retinitis. Patients with CD4(+) counts of <100/microl and negative baseline screening eye examinations were tested for CMV infection by (i) pp65 antigenemia expression in leukocytes, (ii) the Digene Hybrid Capture CMV DNA System, and (iii) the Roche Amplicor Qualitative PCR Test. The incidence of CMV retinitis in our study of 296 patients at the Medical Center of Louisiana-New Orleans HIV Outpatient Clinic was 7. 2 per 100 person-years (a total of 20 episodes in 18 patients from April 1997 to February 1999). Receiver operating characteristic curves were calculated for each assay to determine optimal cutoff points which maximized the sensitivity and specificity of each assay. The sensitivities of the assays compared to the eye examinations were 80% for the pp65 antigenemia assay (cutoff, >0 cell per 1.5 x 10(5) leukocytes), 85% for the Digene assay (cutoff, 1,400 genome copies/ml of whole blood), and 60% for the Amplicor assay. The specificities of the assays were 84, 84, and 87%, respectively. The Digene assay with a cutoff of >/=1,400 genome copies/ml gave optimal sensitivity and specificity and was found to have predictive values equal to those of the more technically cumbersome antigenemia assay.

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.

Comparison of the Murex Hybrid Capture CMV DNA (v2.0) assay and the pp65 CMV antigenemia test for the detection and quantitation of CMV in blood samples from immunocompromised patients

BACKGROUND

Presently the semiquantitative pp65 cytomegalovirus (CMV) antigenemia test on white blood cells is often used for monitoring transplant patients for the appearance of active CMV infections. However, the need for immediate processing of the specimens and the lack of interlaboratory standardization of the test may sometimes be a disadvantage.

OBJECTIVE

The aim of this study was to investigate the value of the recently developed second version of the Murex Hybrid Capture (MHC) CMV-DNA assay (v 2.0) in comparison with the CMV-pp65 test. The MHC CMV-DNA assay is a quantitative solution hybridization antibody capture assay, using alkaline phosphatase conjugated antibodies and a chemiluminescent substrate.

STUDY DESIGN

248 EDTA blood samples from 33 renal transplant patients and 32 samples from 22 other immunocompromised patients were tested by both the MHC CMV-DNA assay and the CMV-pp65 test.

RESULTS

The qualitative ( + or -) results of both tests showed an overall concordance of 81.4%. Calculations on the basis of discordancy analyses showed that the sensitivity, the specificity, and the positive and negative predictive values were 87.7, 98.3, 98.6, 85.2% for the MHC CMV-DNA assay and 76.6, 100, 100, 75.5% for the CMV-pp65 test. Comparison of the quantitative results of both tests systems showed a correlation coefficient of 0.837. In addition, retesting of 50 samples with the MHC-CMV-DNA assay showed an excellent reproducibility with a correlation coefficient of 0.992. All patients which were tested regularly (at least five samples) became either positive with both tests or with none of them. Neither test system detected CMV significantly earlier than the other one. Both tests became strongly positive in all transplant patients with symptomatic CMV infections, and both tests showed a rapid decline of CMV during subsequent antiviral treatment.

CONCLUSION

The quantitative Murex Hybrid Capture CMV-DNA assay (v 2.0) may become a valuable additional tool in CMV diagnosis. Further studies will be needed to support this preliminary judgement.

Evaluation of the AmpliSensor PCR and the SHARP signal detection system for the early prediction of symptomatic CMV infection in solid transplant recipients

BACKGROUND

Cytomegalovirus (CMV) is associated with high morbidity and mortality in transplant patients. Specific antiviral treatment at an early stage of CMV infection may effectively ameliorate, but not eliminate CMV disease in these patients. Presently, the pp65 antigenemia test on peripheral leukocytes is the method most widely used for predicting and monitoring transplant patients for active CMV infection. Nucleic acid amplification methods are less well defined since they lack standardisation.

OBJECTIVE

A seminested fluorometric PCR assay (AmpliSensor-CMV, BAG, Germany) and a one-step PCR with a signal-amplification step (SHARP, Abbott, Germany) specific for the fragments of the CMV UL 122 and UL 123 genes, respectively, were evaluated for the early diagnosis of CMV infection.

DESIGN

A total of 26 recipients of heterogeneous solid organs were monitored prospectively for a median of 99 days after transplantation. By testing 371 clinical samples parallel with the pp65-antigen assay and IgM and IgG EIA assays the sensitivity, specificity, correlation and quantitation potential of both PCRs was evaluated.

RESULTS

Eight out of 26 patients developed active CMV infection. A total of 48 samples of these patients exceeded a CMV-DNA load threshold of 15 genome equivalents/10(5) leukocytes (AmpliSensor-CMV) and 41 samples exceeded the critical cut-off for the SHARP system. The AmpliSensor PCR exceeded its threshold consistently before the clinical onset of CMV disease (median 8 days). There was very good agreement between symptomatic CMV infection in patients and AmpliSensor-PCR, SHARP PCR, and pp65-antigen results (kappa-coefficient > 0.900). IgM and IgG EIA showed moderate agreement (kappa-coefficient = 0.591 and 0.552, respectively).

CONCLUSION

Both PCRs and pp65 antigen assay correlated significantly better with CMV disease than serodiagnosis. The AmpliSensor PCR allowed more precisely than the SHARP system a quantitative determination of viral load and an early and reliable prediction of active CMV infection. The use of AmpliSensor PCR may improve the diagnosis and management of active CMV infection in organ transplant recipients.

Multicenter comparison of the digene hybrid capture CMV DNA assay (version 2.0), the pp65 antigenemia assay, and cell culture for detection of cytomegalovirus viremia

We compared the Digene Hybrid Capture CMV DNA Assay version 2.0, the pp65 antigenemia assay, traditional tube culture, and shell vial culture for the detection of cytomegalovirus (CMV) viremia in several patient populations at three centers. Of 561 blood specimens collected from 402 patients, complete clinical and laboratory data were available for 489. Using consensus definitions for true positives and true negatives, the sensitivities of the Hybrid Capture assay, antigenemia, shell vial, and tube culture were 95, 94, 43, and 46%, respectively. The specificities of the Hybrid Capture assay and antigenemia were 95 and 94%, respectively. At all three study sites, the detected level of CMV viremia was significantly higher with the Hybrid Capture assay or antigenemia than with shell vial and tube culture. In a group of 131 healthy nonimmunosuppressed volunteers, the Hybrid Capture assay demonstrated a specificity of over 99%. The Hybrid Capture assay is a standardized assay that is simple to perform and can utilize whole blood specimens that have been stored for up to 48 h. The high sensitivity and specificity of the Hybrid Capture assay along with its simplicity and flexibility make it a clinically useful assay for the detection of CMV viremia in immunocompromised or immunosuppressed patients. Further evaluation to determine its role in predicting CMV disease and for monitoring the therapeutic response to anti-CMV therapy is needed.

Quantitative cytomegalovirus DNA level in the blood and its relationship to cytomegalovirus retinitis in patients with acquired immune deficiency syndrome

OBJECTIVE

A pilot study was performed to determine whether relationships exist between changes in a quantitative solution hybridization assay for cytomegalovirus (CMV) DNA in the blood and development of CMV retinitis, development of nonocular CMV disease, or reactivation of pre-existing CMV retinitis lesions.

DESIGN

Observational case series.

PARTICIPANTS

Two groups of human immunodeficiency virus-infected patients: 10 CMV antibody-positive patients with CD4+ T-lymphocyte counts of less than 50 ml and no CMV disease at baseline and 11 patients with CMV retinitis but no extraocular CMV disease at baseline.

INTERVENTION

Quantitative changes in leukocyte-associated CMV DNA levels were observed over time. Anti-CMV therapies were based on clinical findings only.

MAIN OUTCOME MEASURES

Development of CMV end-organ disease or change in activity of pre-existing CMV retinitis lesions was measured.

RESULTS

Among patients with no CMV disease at baseline, four had CMV disease develop during follow-up (three cases of CMV retinitis, one case of presumed CMV esophagitis); all had CMV DNA levels greater than 5000 genomes/ml before the onset of CMV disease. The remaining six patients had levels less than 5000 genomes/ml throughout follow-up (P = 0.05). Among patients with CMV retinitis at baseline, all whose CMV DNA blood levels rose more than tenfold had extraocular CMV disease or reactivation of CMV retinitis develop. Raised CMV DNA blood levels were not seen in every patient with clinical reactivation of CMV retinitis.

CONCLUSION

Elevated or rising CMV DNA blood levels appear to be associated with the development of CMV disease in individuals with low CD4+ T-lymphocyte counts. In patients with CMV retinitis, rising levels appear to be associated with the development of extraocular CMV disease or reactivation of CMV retinitis. Conversely, reactivation of CMV retinitis also may occur in the absence of changes in CMV DNA blood levels. Further studies are warranted to determine whether changes in CMV blood levels can be used as a guide for preemptive therapy to prevent reactivation of CMV retinitis lesions or to help choose between local and systemic therapy for management of reactivations.

Quantitation of human cytomegalovirus DNA in peripheral blood leukocytes of heart transplant recipients: relationship with pp65 antigenemia and with antiviral therapy

OBJECTIVE: To retrospectively determine DNA levels in blood polymorphonuclear leukocytes (PMNLs) of 21 heart transplant patients who suffered from HCMV infection and who were monitored by the antigenemia assay (pp65 test) during follow-up, by use of a quantitative competitive polymerase chain reaction (PCR) assay for human cytomegalovirus (HCMV) DNA. METHODS: Quantitation of HCMV DNA by PCR was expressed as genome equivalents (GE) per 200 000 PMNLs. RESULTS: Ten patients experienced symptomatic HCMV infection (five primary infections and five reactivations) with mild symptoms and received ganciclovir treatment, whereas 11 asymptomatic HCMV infections were not treated. Therapy was discontinued when a 90% reduction of the pretreatment antigenic load was achieved in a symptomless patient. The mean HCMV DNA and antigenic loads were significantly higher in symptomatic than in asymptomatic patients: 4.6 x 105 plus minus 4.7 x 105 GE and 1.1 x 104 GE (p<0.0001) and 390 plus minus 350 versus 25 plus minus 12 pp65-positive PMNLs (p<0.0001), and in primary than in secondary infections (583 plus minus 403 pp65-positive PMNLs versus 85 plus minus 111, p=0.002 and 5.2 x 105 plus minus 5.2 x 105 GE instead of 1.5 x 105 plus minus 3.2 x 105 GE, p=0.02). A single course of 14--21 days of ganciclovir caused a marked decrease of HCMV DNA and antigenemia in eight of 10 patients in whom a 90% reduction of the antigenic load correlated with a 98% DNA reduction of the pretreatment levels. In two primary infections, a 90% antigenic reduction was achieved by 21 days of ganciclovir treatment, but those data only correlated with a DNA load reduction of 28% and 60% of the pretreatment levels. Fifteen and 12 days later, respectively, the two patients relapsed and underwent a second ganciclovir course, at the end of which a 90% reduction of the antigenic load correlated with a >98% DNA drop. GCV was discontinued and the patients recovered completely. In those two patients we retrospectively found persistent high DNA levels before the second ganciclovir course, whereas the antigenic load slowly increased after an apparent reduction. CONCLUSIONS: Our data suggest that: (1) DNA levels have the same trend as the pp65 antigen test---they are significantly higher in symptomatic and in primary HCMV-infected patients than in asymptomatic patients and those with secondary infection; (2) a 90% antigenic load reduction from the pre-treatment level may be a less reliable predictor of the efficacy of anti-HCMV therapy than DNA load, at least in primary infection, in which a much higher viral load and much more severe disease are present; and (3) a DNA load reduction of >98% of the pretreatment value is required for therapeutic success.

A randomized prospective controlled trial of oral acyclovir versus oral ganciclovir for cytomegalovirus prophylaxis in high-risk kidney transplant recipients

BACKGROUND

Posttransplantation cytomegalovirus (CMV) infection remains a significant cause of morbidity in kidney transplant recipients. We performed a randomized prospective controlled trial of oral acyclovir versus oral ganciclovir for CMV prophylaxis in a group of renal allograft recipients considered at high risk for CMV disease due to the use of OKT3 induction therapy.

METHODS

A total of 101 recipients of cadaveric (83) and zero haplotype-matched live donor (18) kidney transplants were entered into the trial. A total of 22 D-R- patients received no prophylaxis. Twenty-seven D+R-, 29 D+R+, and 23 D-R+ patients were randomized to receive 3 months of either oral acyclovir (800 mg q.i.d.) or oral ganciclovir (1000 mg t.i.d.). Doses were adjusted according to the level of renal function. The D+R- patients were also given CMV immune globulin biweekly for 16 weeks. Surveillance blood cultures were obtained at transplantation, at months 1, 2, 3, and 6, and when clinically indicated. The primary study end points were time to CMV infection and disease the first 6 months after transplantation.

RESULTS

The mean follow up was 14.4 months. Both agents were well tolerated, and no drug interruptions for toxicity occurred. CMV was isolated in 14 of 39 (35.9%) acyclovir-treated and 1 of 40 (2.5%) ganciclovir-treated recipients by 6 months (P=0.0001). Symptomatic CMV disease occurred in 9 of 14 (64%) of the acyclovir patients, two with tissue-invasive disease. Infection rates for acyclovir vs. ganciclovir, respectively, stratified by CMV serology were: D+R-, 54 vs. 0%, P=0.0008; D+R+, 43 vs. 6.6%, P=0.01; D-R+, 8.3 vs. 0%, P=NS. No patient developed CMV infection while taking oral ganciclovir, however three delayed infections occurred 2-7 months after finishing therapy. Each patient had been previously treated for acute rejection.

CONCLUSIONS

Oral acyclovir provides effective CMV prophylaxis only for recipients of seronegative donor kidneys. Oral ganciclovir is a superior agent providing effective CMV prophylaxis for recipients of seropositive donor kidneys. Recipients who are treated for acute rejection are at risk for delayed CMV infection during the first posttransplantation year.

Use of laboratory assays to predict cytomegalovirus disease in renal transplant recipients

Eight laboratory assays, viz., the pp65 direct antigenemia test, a quantitative cytomegalovirus (CMV)-specific immunoglobulin G (IgG) assay (Biomerieux VIDAS), a CMV-specific IgM assay (Biomerieux VIDAS), the Hybrid Capture system (Murex), an in-house PCR with plasma (P-PCR) and leukocytes (L-PCR), and a commercial PCR (Roche AMPLICOR) with plasma (P-AMP) and leukocytes (L-AMP), were compared for their abilities to predict CMV disease before the onset of illness in a prospective study of 37 renal transplant recipients. By using an expanded criterion for active infection (two or more of the markers positive) and a clinical definition of disease, 22 (59%) patients were identified as having active CMV infection and 13 (35%) were identified as having CMV disease. Of the 13 CMV-seronegative recipients who received seropositive kidneys (R- group), 8 had active infection and disease. All assays were 100% specific and 100% predictive of CMV disease in the R- group. The leukocyte PCRs (L-PCR and L-AMP) were the most sensitive assays, had positive results an average of between 8 and 13 days before the onset of illness, and were the assays of choice. The performance of the assays was less satisfactory for the 24 patients who were CMV seropositive before transplantation (R+ group). A negative result was more useful for this group. Overall, P-AMP had the best results, and it could be the assay of choice for monitoring R+ patients. The non-PCR-based methods generally had high specificities but often gave late positive results and were not sensitive enough for use as prediction tools for either group of patients.

Evaluation of the murex hybrid capture cytomegalovirus DNA assay versus plasma PCR and shell vial assay for diagnosis of human cytomegalovirus viremia in immunocompromised patients

We evaluated a cytomegalovirus (CMV) 24-hour shell vial assay (SVA), the Murex Hybrid Capture CMV DNA assay (HCA), and a CMV plasma PCR for the detection of CMV viremia in renal and bone marrow transplant recipients and human immunodeficiency virus-infected patients. CMV viremia was detected by at least one method in 125 of 317 evaluable samples (39.4%) from 78 patients and was detected in 19.8% of samples by SVA, 26.8% by HCA, and 32.2% by plasma PCR. There was moderate to substantial agreement between the results of the different tests (kappa coefficient = 0.415 to 0.631). However, HCA and plasma PCR were significantly more sensitive than SVA (P = 0.001 and P < 0.0001, respectively; McNemar's test), and plasma PCR was more sensitive than HCA (P = 0.031; McNemar's test). HCA and plasma PCR were more consistently positive than SVA during viremic episodes (P = 0.0002 and P < 0.0001, respectively; McNemar's test). The use of HCA or plasma PCR may therefore improve the diagnosis and management of CMV disease in susceptible patient groups.

Quantitation of cytomegalovirus: methodologic aspects and clinical applications

Cytomegalovirus (CMV) is an important pathogen in transplant recipients and human immunodeficiency virus (HIV)-infected individuals. Major progress has been made in developing quantitative detection methods for CMV in recent years. Due to their high sensitivity, these assays can detect CMV early, and quantitation may be useful in predicting the patient's risk for disease and in monitoring the effect of antiviral therapy. This review discusses methodological aspects of currently used quantitative assays for CMV (i.e., viral culture techniques, antigen detection assays, DNA detection assays including PCR, branched-DNA assay, and the DNA hybrid capture assay) and addresses the correlation of systemic and site-specific CMV load and CMV disease in different populations of immunosuppressed patients as well as the response to antiviral treatment. To date, direct antigen detection and molecular techniques have largely replaced traditional culture-based techniques for CMV quantitation. In general, a high systemic CMV load is correlated with CMV disease. This correlation is strong in the HIV-infected population and in solid-organ transplant recipients but less clear in allogeneic marrow transplant recipients. Measuring the viral load at specific anatomic sites may be an alternative way to assess disease activity in situations where the systemic viral load correlates poorly with disease activity. A reduction of the systemic CMV load also correlates with a response to antiviral treatment, but more research is needed to evaluate the role of viral load as a surrogate marker for drug resistance. Due to the widespread use of quantitative CMV detection techniques to direct and monitor antiviral treatment, there is a great need for an assessment of the reproducibility of test results and better standardization of the assays.

Human cytomegalovirus (HCMV) leukodnaemia correlates more closely with clinical symptoms than antigenemia and viremia in heart and heart-lung transplant recipients with primary HCMV infection

BACKGROUND

In the last few years, human cytomegalovirus (HCMV) viremia, pp65 antigenemia, and leuko- and plasma-DNAemia have been developed to quantitate virus in blood of immunocompromised patients with HCMV infection. However, thus far, no conclusive studies have been performed to define the correlation of each of the different assays with clinical symptoms in primary HCMV infections.

METHODS

This correlation was investigated in a population of 20 heart and heart-lung transplant recipients with primary HCMV infection using standardized virological methods.

RESULTS

Median peak HCMV viremia, antigenemia, and leukoDNAemia levels were 110 (0-2,000) p72-positive fibroblasts, 450 (27-2,000) pp65-positive leukocytes, and >10,000 (1,358-10,000) genome equivalents (GE) in the 14 symptomatic patients and 18 (1-130) p72-positive fibroblasts, 86.5 (5-350) pp65-positive leukocytes, and 248 (10-863) GE in the six asymptomatic patients, respectively. The difference was statistically significant for antigenemia (P=0.009) and leukoDNAemia (P<0.0001). However, on an individual basis, unlike viremia and antigenemia, all DNA peaks of the 6 asymptomatic patients were below the DNA range of the 14 symptomatic patients (<1,000 GE), while all the 14 symptomatic patients had DNA peaks higher than those of asymptomatic patients (>1,000 GE). Follow-up confirmed these results, showing that 1,000-2,000 GE was the threshold zone for emergence of clinical symptoms. Symptoms were never observed in patients with secondary DNA peaks, except for one patient suffering from an HCMV organ localization (HCMV gastritis).

CONCLUSIONS

LeukoDNAemia is the viral parameter of choice for monitoring of primary HCMV infections and antiviral treatment in heart and heart-lung transplant recipients. In this patient population, antigenemia-guided preemptive therapy could be replaced by leukoDNAemia-based antiviral therapy.

The clinical utility of viral quantitation using molecular methods

BACKGROUND

The quantitation of viral nucleic acids in biological fluids has become increasingly desirable over the past several years. To this end, a number of quantitative molecular procedures have been developed.

OBJECTIVES

The objective was to review the current literature on the molecular techniques used in the quantitation of viral nucleic acids and to assess the appropriateness of these methods for clinical use.

RESULTS

Assays involving both target and signal amplification are now available for the accurate and precise quantitation of viral burden in infected patients. These methods include quantitative polymerase chain reaction (PCR), branched chain signal amplification (bDNA), nucleic acid sequence-based amplification (NASBA) and the SHARP signal and hybrid capture systems. Our understanding of the natural history and pathogenesis of viruses such as the human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV) and Epstein-Barr virus (EBV) may be greatly facilitated by accurate determinations of viral and infected cell burden. Quantitation of viral load in infected individuals may also be useful to assess disease progression, monitor the efficacy of therapy and to predict treatment failure and the emergence of drug-resistant viruses.

CONCLUSION

Precise, accurate and reproducible quantitation of viral load is now feasible. Molecular assays for viral quantitation should have a considerable impact on medical research and clinical care.

Evaluation of Murex CMV DNA hybrid capture assay for detection and quantitation of cytomegalovirus infection in patients following allogeneic stem cell transplantation

Murex hybrid capture DNA assay (HCS) is a solution hybridization antibody capture assay for detection and quantitation of cytomegalovirus (CMV) DNA in leukocytes. To determine whether CMV HCS is sensitive enough to initiate and monitor antiviral therapy after allogeneic stem cell transplantation (SCT), 51 consecutive SCT recipients were prospectively screened for the appearance of CMV infection by HCS, PCR, and culture assays from blood samples. Preemptive antiviral therapy was initiated after the second positive PCR result in all patients, as previously reported, and HCS was not considered for clinical decision making. A total of 417 samples were analyzed. Of these, 21 samples were found to be positive by PCR and HCS, 88 samples were PCR positive but HCS negative, and 308 were negative by both assays. Concordance of results between PCR and HCS and between HCS and blood culture was observed in 78.9 and 95.9% of the samples assayed, respectively. PCR was found to be more sensitive than HCS, and HCS was more sensitive than the blood culture assay (P < 0.0001). Four patients with symptomatic CMV infection were PCR positive prior to the onset of CMV-related symptoms, whereas HCS detected CMV DNA in three patients prior to and one at onset of CMV disease. The numbers of genomes per milliliter of blood were higher in patients with symptomatic CMV infection than in those with asymptomatic CMV infection (P = 0.06). None of the HCS-negative patients developed CMV disease. Thus, all patients with CMV disease were correctly identified by HCS; however, the lower sensitivity limit of the HCS assay may still be insufficient to allow diagnosis of CMV infection early enough to prevent CMV disease in patients following allogeneic SCT.

Utility of major leukocyte subpopulations for monitoring secondary cytomegalovirus infections in renal-allograft recipients by PCR

The feasibility of the major peripheral blood leukocyte (PBL) subsets for use in qualitative and quantitative PCR to monitor secondary cytomegalovirus (CMV) infection and ganciclovir therapy was assessed with 188 blood samples derived from 40 CMV immunoglobulin G-positive renal-allograft recipients. In pp65 antigen-positive patients all leukocyte fractions, but only 79.5% of plasma preparations, were PCR positive. In pp65 antigen-negative samples from patients after antiviral treatment only 7.3% of polymorphonuclear cell (PMNL) samples, but 81.8% of peripheral blood mononuclear cells (PBMC), and 10.9% of plasma samples remained PCR positive. Similarly, in patients with latent infections only 5.0% of PMNL, but 51.7% of PBMC preparations, and 8.0% of plasma samples were PCR positive. Regarding patients with active CMV infection, CMV DNA copy numbers in PMNL correlated significantly with pp65 antigen-positive cell counts before and after onset of ganciclovir therapy. Significant differences in CMV DNA copy numbers in PMNL and plasma were observed (i) between patients with symptomatic infection and those with asymptomatic infection and (ii) between patients with active infection and those with latent infection. In contrast, PBMC harbored equally low CMV DNA levels both in patients with active infection and those with latent infections, and no decline of CMV DNA load in PBMC was observed during antiviral treatment. We conclude that detection of CMV DNA in PMNL, not in PBMC, is associated with active infections and is more sensitive than detection of CMV DNA in plasma. Negative PCR results for PMNL after antiviral therapy indicate recovery, and fewer unwanted positive results occur compared to PBMC and plasma. Therefore, purified PMNL should be preferred for analysis by qualitative CMV PCR to avoid unwanted positive results. The CMV DNA load in PBMC compared with that in PMNL is negligible during active infection, so mixed PBL are sufficient for use in quantitative PCR.

Long-term predictive value of a single cytomegalovirus (CMV) DNA PCR assay for CMV disease in human immunodeficiency virus-infected patients

Universal prophylaxis with oral ganciclovir is not cost-effective for the prevention of cytomegalovirus (CMV) disease in human immunodeficiency virus infection. For a preemptive strategy to be considered, patients at highest risk for CMV disease need to be easily and accurately identified. In this study, the sensitivity, specificity, positive predictive value, and negative predictive value of a single CMV DNA PCR assay for the subsequent development of CMV disease were 0.75, 0.89, 0.75, and 0.89, respectively.

Management of cytomegalovirus infection after solid-organ or stem-cell transplantation. Current guidelines and future prospects

Recent developments in diagnosis and therapy of cytomegalovirus (CMV) infection have helped to reduce CMV-associated mortality following organ transplantation. However, CMV is still associated with significant morbidity in recipients of an allogeneic stem cell or solid-organ transplant. The clinical symptoms of active CMV infection per se and, most importantly, the prevalence of life-threatening CMV disease show broad variation between different patient populations depending on the type of transplant and the intensity of immuno-suppression. Therefore, management of CMV infection must be stratified according to risk profiles of a given patient population. In the past decade, novel diagnostic assays (such as rapid shell-vial culture, polymerase chain reaction, pp65 antigen assay and sensitive hybridisation techniques) have been developed. Broad variations in the ability of a given test to predict a positive or negative risk of developing CMV disease have been observed between different transplant modalities. Highly effective therapeutic agents against CMV, such as ganciclovir and foscarnet, have become available, improving the outcome of patients with CMV disease. Moreover, antiviral prophylaxis with ganciclovir or aciclovir has been shown to reduce CMV infection and CMV disease following organ transplantation. However, these drugs are often associated with considerable toxicity. Moreover, antiviral resistance to ganciclovir and foscarnet has been observed in recipients of organ transplants and, even more frequently, in patients with AIDS. Short courses of pre-emptive antiviral therapy, administered after CMV infection has been documented by sensitive diagnostic techniques prior to the development of clinical symptoms, help to reduce duration and incidence of adverse effects associated with antiviral drugs and are thus an attractive strategy compared with antiviral prophylaxis. Newer options, such as oral ganciclovir, cidofovir, benzimidavir (1263W94) and lobucavir, are currently under investigation and might further improve the management of CMV infection in recipients of solid-organ or stem-cell transplants.

Surveillance of cytomegalovirus after solid-organ transplantation: comparison of pp65 antigenemia assay with a quantitative DNA hybridization assay

In a multicenter study, 113 blood samples from 19 organ transplant patients were analyzed for cytomegalovirus by the pp65 antigenemia assay and a quantitative DNA hybridization assay. Overall, there was 84% agreement among the results obtained by the two tests. Fifteen of 16 episodes of active infection were detected by both assays. One episode was missed by the pp65 assay, and one patient showed significant DNA-emia but only low-level antigenemia.

Evaluation of a novel immunoglobulin A capture enzyme immunoassay for diagnosis of cytomegalovirus infection in renal and heart transplant recipients

In a retrospective cohort study of 68 organ transplant patients, the usefulness of a new commercial immunoglobulin A (IgA) antibody capture enzyme immunoassay (EIA) specific to human cytomegalovirus (CMV) for the early diagnosis of CMV disease was investigated. The results were compared with those obtained with the CMV pp65 antigen assay in peripheral blood leukocytes, an IgM immunoblot assay, and six other commercial EIAs. In 21 of 28 patients with CMV disease, the pp65 antigen assay and the immunoblot assay identified patients before the onset of disease more frequently than any other serological test method (17 and 13 patients, respectively; p = 0.0029). In patients at risk for primary CMV infection, the pp65 antigen assay was the only method that identified all patients prior to the onset of CMV disease (p = 0.008). For the other patients who were at risk for CMV infection, the pp65 antigen assay and the immunoblot assay detected infection before CMV disease more frequently than any other test system (p = 0.026). With respect to CMV disease, both immunoblotting and the pp65 antigen assay showed excellent sensitivity (100% and 89%, respectively). However, the specificity of the immunoblot was poor (41%), while the specificity of the pp65 antigen assay was reasonably good (68%). The IgA capture EIA showed moderate sensitivity (61%) and reasonable specificity (76%). In conclusion, the pp65 antigen assay, which detects pp65 antigen in leukocytes, is the method of choice for diagnosis of either primary or recurrent CMV infection. The specificity of the pp65 antigen assay was improved by additional testing for specific IgA and IgM antibodies (95% vs. 68%). The IgA assay is of limited value in renal and heart transplant patients, since it detected IgA antibodies only sporadically, and even then, too late for a timely therapy.

Comparative quantification of human cytomegalovirus DNA in blood of immunocompromised patients by PCR and Murex Hybrid Capture System

BACKGROUND

Monitoring of human cytomegalovirus (HCMV) load by quantification of antigenemia, viremia and DNAemia is helpful in the management of HCMV infections in immunocompromised patients. In fact, threshold values of these viral parameters are associated with the emergence of clinical symptoms. In addition, the response to antiviral treatment is revealed by a decrease in viral load or virus disappearance from blood.

OBJECTIVES

Aim of this study was to compare HCMV DNA quantification in blood of immunocompromised patients by an 'in house' developed quantitative PCR (Q-PCR) assay and the commercially available Murex Hybrid Capture System (HCS).

STUDY DESIGN

HCMV DNA was quantified in 95 blood samples from 12 heart and heart-lung transplant recipients and 27 AIDS patients using both techniques. For HCS analysis 3.5 ml whole blood were utilized, whereas Q-PCR was performed using 1 x 10(5) peripheral blood leukocytes (PBL). HCMV DNA levels obtained by HCS and Q-PCR were expressed as number of genome equivalents (GE)/ml whole blood or 1 x 10(5) PBL, respectively. Results from HCS and Q-PCR were compared and submitted to statistical analysis. In addition, HCMV DNA values were compared to levels of antigenemia and viremia.

RESULTS AND CONCLUSIONS

Sensitivity of HCS, antigenemia and viremia with respect to Q-PCR were 37.2, 79.5 and 33.3%, respectively. Specificity was 100% for all techniques. On average, samples positive by Q-PCR only, contained low amounts of HCMV DNA. In particular, 45 (91.8%) out of 49 samples negative by HCS and positive by Q-PCR showed < 500 GE/1 x 10(5) PBL. A significant correlation was found between quantitative DNA levels in samples positive by both HCS and Q-PCR (n = 29, R = 0.693, P < 0.01). HCS positivity was associated to significantly higher DNA values as determined by Q-PCR as well as to significantly higher antigenemia and viremia levels. A decrease in DNAemia levels was observed using both HCS and Q-PCR after antiviral treatment. Given that the great majority of blood samples missed by HCS contain low levels of HCMV DNA which are not clinically significant, HCS seems very promising as an alternative to HCMV DNA quantification by PCR in solid organ transplant recipients and AIDS patients.

Usefulness of DNA viral load quantification for cytomegalovirus disease monitoring in renal and pancreas/renal transplant recipients

BACKGROUND

The purpose of this prospective study was to evaluate the usefulness of quantifying DNA-cytomegalovirus (CMV) load for the diagnosis and monitoring of CMV disease among renal and pancreas transplant patients under immunosuppressive drugs.

METHODS

A longitudinal study was conducted among 34 consecutive, unselected renal and pancreas/renal transplanted patients in our unit. During the first 3 posttransplant months, weekly monitoring of CMV infection and CMV disease was done, involving the determination of viremia by the shell vial assay, qualitative DNAemia by semi-nested polymerase chain reaction (PCR) and quantitative DNAemia by the hybrid capture system (HCS), a new and original hybridization method (337 samples were collected for each test). Qualitative and quantitative DNAemia results were blinded to physicians and three grades of disease were defined according to CMV related symptom occurrence.

RESULTS

PCR was the most sensitive (100%) but the least specific (78%) method for the diagnosis of CMV disease. HCS was specific for CMV genome detection, sensitive and reproducible. Blood DNA levels above 60 pg/ml were predictive of severe or moderate CMV disease (sensitivity, 92%; specificity, 100%). A significant decrease in viral load was observed after ganciclovir administration, and a positive PCR or HCS result at the end of the antiviral treatment was associated with relapse of CMV infection or disease.

CONCLUSIONS

It is concluded that quantitative DNAemia detection, with this new commercially available method, can predict disease and may be useful for a rational evaluation of ganciclovir preemptive therapy in such patients.