Comparative study of cytomegalovirus (CMV) antigenemia assay, polymerase chain reaction, serology, and shell vial assay in the early diagnosis and monitoring of CMV infection after renal transplantation

Fast and Efficient Titration of Human Cytomegalovirus Stocks with a Self-Excisable Bacterial Artificial Chromosomes Cassette by Flow Cytometry

The study of human cytomegalovirus (HCMV) has for long been challenging due to the inability of clinical strains to efficiently proliferate in vitro until adaptive mutations occur. These mutations lead to strains that differ considerably from clinical isolates, many of them showing altered cell tropism, a decrease in cell association and higher susceptibility to an innate immune response. These problems were recently solved by the use of bacterial artificial chromosome (BAC) vectors that allow for the conservation of an intact HCMV genome. Other characteristics that render HCMV difficult for in vitro study are related to its slow replication rate that leads to some constraints in its titration. During the cloning of HCMV into BAC vectors, many groups additionally inserted a fluorescent tag to facilitate the virus characterization. However, the methods used for titration of HCMV-BAC stocks are still relaying on the standard methods that are expensive and/or time consuming. In this study, we assessed the possibility of viral titration by fluorescence-activated cell sorting (FACS), making use of the fluorescent tags that many of the HCMV-BACs hold. We compared viral titers obtained by immunohistochemistry with FACS, a faster and inexpensive technique. We showed that viral titers are comparable using the techniques already mentioned, and that titration by FACS is an efficient, fast, and cost-effective method. The establishment of viral titration of BAC vectors by FACS can further simplify the study of HCMV.

Cytomegalovirus Colitis and Subsequent New Diagnosis of Inflammatory Bowel Disease in an Immunocompetent Host: A Case Study and Literature Review

Patient: Male, 40

Final Diagnosis: CMV colitis

Symptoms: Abdominal pain • diarrhea • jaundice

Medication: —

Clinical Procedure: Flexible sigmoidoscopy • colonoscopy

Specialty: Family Medicine

Cytomegalovirus infection in transplant recipients

Cytomegalovirus infection is a frequent complication after transplantation. This infection occurs due to transmission from the transplanted organ, due to reactivation of latent infection, or after a primary infection in seronegative patients and can be defined as follows: latent infection, active infection, viral syndrome or invasive disease. This condition occurs mainly between 30 and 90 days after transplantation. In hematopoietic stem cell transplantation in particular, infection usually occurs within the first 30 days after transplantation and in the presence of graft-versus-host disease. The major risk factors are when the recipient is cytomegalovirus seronegative and the donor is seropositive as well as when lymphocyte-depleting antibodies are used. There are two methods for the diagnosis of cytomegalovirus infection: the pp65 antigenemia assay and polymerase chain reaction. Serology has no value for the diagnosis of active disease, whereas histology of the affected tissue and bronchoalveolar lavage analysis are useful in the diagnosis of invasive disease. Cytomegalovirus disease can be prevented by prophylaxis (the administration of antiviral drugs to all or to a subgroup of patients who are at higher risk of viral replication) or by preemptive therapy (the early diagnosis of viral replication before development of the disease and prescription of antiviral treatment to prevent the appearance of clinical disease). The drug used is intravenous or oral ganciclovir; oral valganciclovir; or, less frequently, valacyclovir. Prophylaxis should continue for 90 to 180 days. Treatment is always indicated in cytomegalovirus disease, and the gold-standard drug is intravenous ganciclovir. Treatment should be given for 2 to 3 weeks and should be continued for an additional 7 days after the first negative result for viremia.

Peripheral blood leukocytes and serum nested polymerase chain reaction are complementary methods for monitoring active cytomegalovirus infection in transplant patients

BACKGROUND

Human cytomegalovirus is an important cause of morbidity and mortality in immunocompromised patients. Qualitative polymerase chain reaction (PCR) has proven to be a sensitive and effective technique in defining active cytomegalovirus infection, in addition to having low cost and being a useful test for situations in which there is no need for quantification. Real-time PCR has the advantage of quantification; however, the high cost of this methodology makes it impractical for routine use.

OBJECTIVE

To apply a nested PCR assay to serum (sPCR) and to evaluate its efficiency to diagnose active cytomegalovirus infection compared with PCR of peripheral blood leukocytes (L-PCR).

METHODS

Samples of 37 patients were prospectively evaluated. An internal control was created and applied to sPCR to exclude false-negative results.

RESULTS

In total, 21 patients (57%) developed active cytomegalovirus infection. After analyzing the two methods for the diagnosis of active infection, higher sensitivity and negative predictive value of the L-PCR versus sPCR (100% versus 62%), and higher specificity and positive predictive value of sPCR versus L-PCR (81% versus 50% and 72%, respectively) were observed. Discordant results were observed in 11 patients who were L-PCR-positive but sPCR-negative for active cytomegalovirus infection, five of whom developed clinical symptoms of cytomegalovirus. Clinical symptoms were observed in 14 patients, 12 of whom were diagnosed with active infection by nested L-PCR (P=0.007) and seven by nested sPCR (P=0.02). Higher specificity and a positive predictive value for sPCR were observed.

CONCLUSION

Nested L-PCR and sPCR were considered to be complementary methods for the diagnosis and management of symptomatic cytomegalovirus infection.

The role of the cytomegalovirus antigenemia assay in the detection and prevention of cytomegalovirus syndrome and disease in solid organ transplant recipients: A review of the British Columbia experience

BACKGROUND

The pp65 cytomegalovirus (CMV) antigenemia assay has been used as a means of guiding the pre-emptive therapy of CMV disease in solid organ transplant (SOT) recipients. Recently, concerns have been raised regarding the utility of the test to accurately and precisely detect viral activity early enough to reduce the morbidity and mortality associated with CMV OBJECTIVE: To determine the performance characteristics of the method of antigenemia testing of SOT recipients used at Vancouver General Hospital, Vancouver, British Columbia.

METHODS

All SOT recipients between January 1, 1999, and June 30, 2000, were retrospectively reviewed for six months following transplantation. Physical examination results, laboratory parameters, antigenemia results and treatment information were reviewed.

RESULTS

A total of 134 kidney, liver, lung and kidney-pancreas transplant recipients were included in the analysis. The overall performance characteristics of the antigenemia assay in predicting CMV disease included a sensitivity of 64%, a specificity of 81%, a positive predictive value of 76% and a negative predictive value of 71%. A mean of 18 days passed between the onset of signs and symptoms of CMV disease/syndrome and the first recorded positive antigenemia result, and only 26% of patients had a positive test result before the onset of symptoms. It was found that an antigenemia test breakpoint of at least one positive cell for defining a positive test provided the most sensitive and specific prediction, with increased odds of developing CMV disease.

CONCLUSIONS

Based on performance characteristics, the Vancouver General Hospital's current method of antigenemia testing to guide pre-emptive ganciclovir therapy in SOT patients is not optimal for the early detection of disease. Further study is needed on new molecular testing methods to determine if our ability to predict CMV disease can be improved.

Strain-specific seroepidemiology and reinfection of cytomegalovirus

Although there have been some reports describing the serostatus of cytomegalovirus, strain-specific antibody responses and their distribution remain unknown. In this study, ELISA using fusion proteins encompassing epitope of glycoprotein H from both AD169 and Towne strains was used to test 352 blood donors. Of these 352 donors, 207 were analyzed for strain-specific glycoprotein H antibodies. Of the 44 donors whose serum contained antibodies against both AD169 and Towne, 27 (60%) were aged 50 years or over (p = 0.0003). This may indicate serological evidence of reinfection with cytomegalovirus in the elder population. The nucleotide sequence analysis of cytomegalovirus glycoprotein H from the peripheral blood of the cytomegalovirus-positive renal transplant recipients showed that our strain-specific ELISA can reveal cytomegalovirus reinfection after transplantation.

Nonhuman primate infections after organ transplantation

Nonhuman primates, primarily rhesus macaques (Macaca mulatta), cynomolgus macaques (Macaca fascicularis), and baboons (Papio spp.), have been used extensively in research models of solid organ transplantation, mainly because the nonhuman primate (NHP) immune system closely resembles that of the human. Nonhuman primates are also frequently the model of choice for preclinical testing of new immunosuppressive strategies. But the management of post-transplant nonhuman primates is complex, because it often involves multiple immunosuppressive agents, many of which are new and have unknown effects. Additionally, the resulting immunosuppression carries a risk of infectious complications, which are challenging to diagnose. Last, because of the natural tendency of animals to hide signs of weakness, infectious complications may not be obvious until the animal becomes severely ill. For these reasons the diagnosis of infectious complications is difficult among post-transplant NHPs. Because most nonhuman primate studies in organ transplantation are quite small, there are only a few published reports concerning infections after transplantation in nonhuman primates. Based on our survey of these reports, the incidence of infection in NHP transplant models is 14%. The majority of reports suggest that many of these infections are due to reactivation of viruses endemic to the primate species, such as cytomegalovirus (CMV), polyomavirus, and Epstein-Barr virus (EBV)-related infections. In this review, we address the epidemiology, pathogenesis, role of prophylaxis, clinical presentation, and treatment of infectious complications after solid organ transplantation in nonhuman primates.

Effect of cytomegalovirus prophylaxis with acyclovir on renal transplant survival

It is recognized that cytomegalovirus (CMV) infection in transplant recipients may lead to graft loss. Prophylaxis with acyclovir has therefore gained widespread acceptance, but the debate on whether this intervention improves long term graft survival continues. All patients who received renal grafts at the National Renal Transplant Centre, Dublin, between January 1992 and December 1999 were retrospectively analyzed. During this time period, patients who were CMV positive and/or had received grafts from CMV-positive donors were administered prophylactic oral acyclovir 800 mg thrice daily, adjusted for calculated creatinine clearance, from the first day post-transplantation. This treatment was continued for three months unless the graft failed or the patient developed CMV disease or died. Graft and patient outcomes were compared in recipients who received acyclovir with those who did not. Over the study period, 935 patients received renal transplants in our center, of whom 487 were administered acyclovir. The incidence of CMV disease was 3.3 cases per 100 patients per annum in those who required prophylaxis. Despite prophylaxis, graft outcomes were found to be significantly worse (p value < 0.001) in the group that qualified for acyclovir. We conclude that acyclovir provides incomplete protection from the negative impact of CMV on graft survival.

Multicentric evaluation of a new commercial cytomegalovirus real-time PCR quantitation assay

Automated real-time PCR systems have become the most common method in the quantitation of viral load during cytomegalovirus (CMV) infection in immuno-compromised patients. In order to evaluate a new commercially available CMV real-time PCR assay (CMV R-gene, Argene, France), a pp65 antigenemia assay and four different "in-house" real-time PCR assays were compared to the CMV R-gene for the detection and the quantitation of CMV load in 506 specimens of whole blood from transplant patients in four French hospital laboratories. The CMV R-gene was more sensitive than the pp65 antigenemia: there were 18% antigenemia-negative versus CMV R-gene-positive samples. A significant correlation was found between DNA quantitation by CMV R-gene and the number of positive cells detected by the pp65 antigenemia test (Spearman's rank test, r=0.63, p<0.0001). A CMV DNA load equivalent to 50 pp65-positive cells/200000 polymorphonuclear leukocytes was 5.26log(10)copies/mL of whole blood. When the CMV R-gene kit was compared to the four other "in-house" real-time PCR assays, there were few discordant results (6.7% total for the four laboratories), all detected with a weak positive CMV DNA viral load. Spearman's coefficients showed a good (r=0.82 for laboratory 1, r=0.66 for laboratory 3) to excellent (r=0.99 for laboratory 2, r=0.94 for laboratory 4) correlation between CMV R-gene and the four real-time "in-house" PCR assays. However, the results of CMV DNA viral load generated by CMV R-gene test were constantly higher than those generated by three out of four "in-house" PCR assays. This mean variation in CMV DNA viral load measured by CMV R-gene and "in-house" PCRs was of 0.77log(10), 0.04log(10), 0.77log(10) and 0.97log(10), for laboratories 1, 2, 3 and 4, respectively. We concluded that there was variability between results of different real-time PCR assays for CMV DNA quantitation. This observation emphasized the need of a standardised commercial assay to allow an "inter-laboratory" comparison of results. Our study showed that CMV R-gene is an accurate, efficient, reliable and versatile tool for rapid diagnosis and monitoring of CMV disease in transplantation recipients.

Association of the Outcome of Renal Transplantation with Antibody Response to Cytomegalovirus Strain--Specific Glycoprotein H Epitopes

BACKGROUND

Cytomegalovirus (CMV) is the most important pathogen affecting the outcome of renal transplantation. The combination of CMV-seronegative transplant recipients with CMV-seropositive transplant donors places recipients at the highest risk of CMV disease. In cases of congenital CMV infection, existing immunity only partially protected mothers from reinfection with a different genotypic strain. The effect of differences in infected CMV strains between CMV-seropositive transplant donors and CMV seropositive transplant recipients on the outcome of transplantation remains unclear.

METHODS

In this prospective multicenter study, the presence of antibodies against strain-specific glycoprotein H epitopes in 84 CMV-seropositive transplant donor/CMV-seropositive transplant recipient renal transplantation cases were determined, and their relationships to acute transplant rejection, CMV infection, degree of antigenemia, and CMV disease were evaluated.

RESULTS

Among the 84 donor/recipient pairs, 45 and 32 had matched and mismatched strain-specific glycoprotein H antibodies, respectively. Acute transplant rejection in the mismatched group was more frequent than it was in the matched group (63% vs. 22%; P=.005). CMV disease was also more frequently observed in the mismatched group (28% vs. 9%; P=.026). The mismatched group had a higher level of antigenemia (P=.019).

CONCLUSIONS

Our results illustrate more adverse events in the cases with a CMV-seropositive transplant donor and a CMV-seropositive transplant recipient in which the glycoprotein H antibodies are mismatched, suggesting that reinfection with a different CMV strain results in more complications.

Evaluation of real-time PCR laboratory-developed tests using analyte-specific reagents for cytomegalovirus quantification

Viral load testing for cytomegalovirus (CMV) has become the standard for the diagnosis of infection and monitoring of therapy at many transplant centers. However, no viral load test has been approved by the FDA. Therefore, many laboratories rely on laboratory-developed assays. This study evaluated the performance characteristics of two real-time PCR tests developed using the artus CMV analyte-specific reagents (ASRs). One version is distributed by Abbott Molecular and the other by QIAGEN. For plasma specimens, the Abbott test had a limit of detection of 2.3 log10 copies/ml and a linear range up to at least 6.0 log10 copies/ml. Comparison of plasma viral loads using the Abbott test and the Roche Amplicor Monitor test showed a mean difference of -0.012 log10 copies/ml. In addition, the Abbott test viral loads correlated with the Digene Hybrid Capture assay ratios. Viral loads obtained from plasma specimens tested by the Abbott and QIAGEN tests were in very close agreement (mean difference, 0.144 log10 copies/ml). When the QIAGEN test was evaluated with the QIAGEN, MagNA Pure, and easyMAG extraction methods, the viral loads for all three methods were within 0.370 log10 copies/ml. Thus, there is good agreement between viral loads obtained by the different tests using the same extraction method or by the same test using different extraction methods. The availability of real-time PCR ASRs provides additional reagents that can be used for CMV viral load testing.

Cytomegalovirus colitis complicating inflammatory bowel disease

When patients with inflammatory bowel disease (IBD) are admitted to the hospital with a flare of acute severe colitis, the possibility of a concurrent cytomegalovirus (CMV) infection causing or worsening the colitis is often considered. IBD patients are usually immunosuppressed, and therefore presumably at increased risk for active CMV infection and disease. Multiple techniques are used to diagnose CMV infection, including endoscopy, histology, serology, viral culture, CMV antigen testing, and CMV DNA testing. Immunohistochemistry (IHC) performed on colon biopsy specimens with monoclonal antibodies directed against CMV immediate early antigen is considered by most to be the current gold standard for diagnosis. The prevalence of CMV infection in acute severe colitis appears to be 21-34%, and the prevalence of CMV infection in the steroid refractory subgroup of these patients is 33-36%. After antiviral therapy, colitis remission rates in IBD patients with CMV infection range from 67% to 100%, though CMV histological infection or the presence of circulating virus alone is not always associated with steroid resistance, and may not require antiviral therapy.

Infections in pediatric solid organ transplant recipients

Despite the progress made in graft and patient survival in recent years, infectious complications remain a major source of morbidity and mortality in pediatric solid organ transplant recipients. The risk of infection after transplant is determined by the interaction of several factors, including age, type of organ transplanted, type and intensity of immunosuppression, environmental exposures, and the consequences of invasive procedures. Compared with adult transplant recipients, children are at higher risk of developing primary infection with various organisms after transplantation, as they often lack previous immunity from natural exposure to many microbes and often have not completed their primary immunization series at the time of transplantation. This article provides an overview of the risk factors, timing, and types of infectious complications associated with organ transplantation in children.

A case of systemic lupus erythematosus complicated by alveolar hemorrhage and cytomegalovirus colitis

We report a rare case of systemic lupus erythematosus (SLE) complicated by alveolar hemorrhage and cytomegalovirus (CMV) colitis. Despite the successful treatment of lupus nephritis by steroid pulse therapy, the patient developed an acute alveolar hemorrhage 2 months later. Cyclophosphamide pulse therapy ameliorated the hemorrhage. One month later, she suddenly developed melena secondary to CMV colitis. Antiviral therapy was successful. We emphasize the importance of timely and precise differential diagnosis for successful management of complicated SLE.

Comparative analysis of a double primer PCR assay with plasma, leukocytes and antigenemia for diagnosis of active human cytomegalovirus infection in bone marrow transplant patients

The aim of the study was to determine the prognostic value of a double primer PCR assay to detect human cytomegalovirus (HCMV) infection or disease in bone marrow transplant (BMT) recipients. A total of 209 blood samples including peripheral blood mononuclear cells (PBMN), polymorphonuclear (PMN) leukocytes and plasma from 26 BMT recipients were tested by PCR assay. To discriminate between latent and active HCMV infection, 177 blood samples were also tested by a quantitative antigenemia assay. HCMV serology status of donors and recipients was determined before transplantation by an enzyme immunosorbent assay method. Using the double primer PCR assay, the number of positive samples increased by an average of 11.6%. Symptomatic active HCMV infection was diagnosed in 14 (53.8%) out of 26 BMT patients. There was a good association between double primer PCR assay of PMN leukocytes and antigenemia assays for detection of active HCMV infection in all patients. Detection of HCMV DNA in PMN leukocytes of BMT patients by double primer PCR assay can be an alternative method for antigenemia assay. However, quantitative PCR methods will be necessary for monitoring antiviral treatment.

Analysis of a quantitative PCR assay for CMV infection in liver transplant recipients: an intent to find the optimal cut-off value

BACKGROUND

Preemptive therapy required highly predictive tests for CMV disease. CMV antigenemia assay (pp65 Ag) has been commonly used for rapid diagnosis of CMV infection. Amplification methods for early detection of CMV DNA are under analysis.

OBJECTIVES

To compare two diagnostic methods for CMV infection and disease in this population: quantitative PCR (qPCR) performed in two different samples, plasma and leukocytes (PMNs) and using a commercial diagnostic test (COBAS Amplicor Monitor Test) versus pp65 Ag.

STUDY DESIGN

Prospective study conducted in liver transplant recipients from February 2000 to February 2001.

RESULTS

Analyses were performed on 164 samples collected weekly during early post-transplant period from 33 patients. Agreements higher than 78% were observed between the three assays. Optimal qPCR cut-off values were calculated using ROC curves for two specific antigenemia values. For antigenemia >or=10 positive cells, the optimal cut-off value for qPCR in plasma was 1330 copies/ml, with a sensitivity (S) of 58% and a specificity (E) of 98% and the optimal cut-off value for qPCR-cells was 713 copies/5x10(6) cells (S:91.7% and E:86%). Using a threshold of antigenemia >or=20 positive cells, the optimal cut-off values were 1330 copies/ml for qPCR-plasma (S 87%; E 98%) and 4755 copies/5x10(6) cells for qPCR-cells (S 87.5%; E 98%). Prediction values for the three assays were calculated in patients with CMV disease (9 pts; 27%). Considering the assays in a qualitative way, the most sensitive was CMV PCR in cells (S: 100%, E: 54%, PPV: 40%; NPV: 100%). Using specific cut-off values for disease detection the sensitivity, specificity, PPV and NPV for antigenemia >or=10 positive cells were: 89%; 83%; 67%; 95%, respectively. For qPCR-cells >or=713 copies/5x10(6) cells: 100%; 54%; 33% and 100% and for plasma-qPCR>or=1330 copies/ml: 78%, 77%, 47%, 89% respectively.

CONCLUSIONS

Optimal cut-off for viral load performed in plasma and cells can be obtained for the breakpoint antigenemia value recommended for initiating preemptive therapy with high specificities and sensitivities. Diagnostic assays like CMV pp65 Ag and quantitative PCR for CMV have similar efficiency and could be recommended as methods of choice for diagnosis and monitoring of active CMV infection after transplantation.

Monitoring for human cytomegalovirus infection in solid organ transplant recipients through antigenemia and glycoprotein N (gN) variants: evidence of correlation and potential prognostic value of gN genotypes

Human cytomegalovirus (HCMV) ORF UL73 encodes the envelope glycoprotein gpUL73-gN, which shows seven genotypes (gN-1, gN-2, gN-3a, gN-3b, gN-4a, gN-4b, gN-4c). The goal of this study was to determine retrospectively the distribution of gN variants in solid organ transplant recipients with HCMV infection and to establish an association with parameters important for monitoring post-transplantation clinical course during a follow-up of up to 2 years. Peripheral blood leukocytes from 40 solid organ transplant recipients were analysed for pp65-antigen by immunofluorescence and gN genotyped by sequencing or RFLP analysis. A correlation between gN genotypes and antigenemia peak was found, showing a highly significant difference between gN-1 and gN-4b variants (P<0.005). In particular, gN-1 seems to be associated with patients developing low level antigenemia (<50 pp65-positive cells/2 x 10(5) PBLs; PPV = 90%), whereas gN-4b predicts significantly higher values (>50 pp65-positive cells/2 x 10(5) PBLs; PPV = 80%). Furthermore, the onset of positive antigenemia is significantly earlier in patients infected with a gN-4b strain, compared with those infected by a gN-1 variant. Reported data further support a role for gN genotypes in HCMV pathogenesis. gN-1 and gN-4b show a significantly different virulence and could serve as early predictors for the progression of HCMV infection in transplant patients.

Clinical and immunologic aspects of cytomegalovirus infection in solid organ transplant recipients

Primary cytomegalovirus (CMV) infection is a major cause of morbidity and mortality in recipients after solid organ transplantation (SOT). Widespread and prolonged use of antiviral drugs has changed the natural course of CMV disease by delaying its onset and causing drug resistance. CMV induces a strong cellular immune response, even in immunosuppressed patients, and has developed strategies to evade this immune surveillance. This review summarizes challenges in managing CMV infection in transplant recipients and highlights current insights in the cellular immune response against CMV.

Prospective study of relationship between cytomegalovirus pneumonia and viral load in renal transplant recipients

The present study prospectively examined the relationship between cytomegalovirus interstitial pneumonia (CMV-IP) and viral load among 56 renal transplant recipients. We sought to identify the cutoff of viral load to predict CMV-IP. Blood samples were obtained weekly within the first 2 months and every second week during 2 to 6 months after kidney transplantations. A commercial real-time polymerase chain reaction (PCR)-method was applied to quantify CMV-DNA in plasma or in leukocytes. Among 54 renal transplant recipients who were analyzed for CMV-DNA in the blood (96.4%), 8 experienced CMV-IP (14.3%) and 2 died (3.6%). After kidney transplantation, CMV-DNA loads were near 0 in plasma before the week 4 and before the week 3 in leukocytes among both groups. From week 5 (week 4, in leukocytes), plasma CMV-DNA loads in the CMV-IP group increased, the peak value reached at week 8 in plasma and the week 9 in leukocytes. Whereas, the CMV-DNA loads both in plasma and in leukocytes in the non-CMV-IP group fluctuated at lower levels, those in plasma were significantly different between the 2 groups at the weeks 5, 7, and 9. For CMV-DNA in leukocytes, there were significant differences between 2 groups from week 6 to week 11. The present study demonstrated that dynamic determination of CMV-DNA may predict the occurrence of CMV-IP. Viral loads over 10(4) copies/mL plasma continuing for 3 weeks may serve as a cutoff to predict CMV-IP.

Strategies for the prevention of cytomegalovirus infection and disease in pediatric liver transplantation recipients

Cytomegalovirus (CMV) is the most common opportunistic infection following solid organ transplantation. Prevention and management of CMV infection has assumed a higher priority as transplantation has become a frequent treatment for many congenital and acquired disorders, as more potent immunosuppressive agents have become available, new molecular and virologic assays to detect CMV have made their way from research to clinical laboratories and new antiviral medications and biologics have been developed. Management strategies are diverse; however, there are little or no data from large controlled pediatric trials demonstrating the superiority of any particular approach. This review outlines the current strategies employed to prevent CMV infection and disease and summarizes the strengths and limitations of each regimen to guide clinicians in the selection of the optimal preventative approach.

Sequential cytomegalovirus antigenemia monitoring in kidney transplant patients treated with antilymphocyte antibodies

BACKGROUND

Antilymphocyte antibodies (ALA) use is related to disseminated cytomegalovirus (CMV) disease after kidney transplantation. Strict surveillance of CMV infection, preemptive antiviral treatment or concomitant ganciclovir and ALA use are proposed as an attempt to prevent related clinical complications. Our objective was to describe the pattern of CMV infection, based on sequential antigenemia detection, after ALA treatment.

PATIENTS AND METHODS

Thirty renal transplant patients were prospectively screened for CMV infection after ALA treatment. CMV antigenemia (pp65 antigen detection) was monitored twice a week in the first month and weekly until 60 days after the beginning of ALA therapy. Any positive value of antigenemia was considered CMV infection.

RESULTS

Twenty-eight (93.3%) patients were CMV positive (IgG) before transplantation. The mean duration of ALA treatment was 12.1+/-2.4 days. Positive antigenemia was detected in 24 (80%) patients, a mean of 52.5+/-15 days after transplant and 44.7+/-14 days after the beginning of ALA treatment. The median antigenemia count was 7 positive cells/300,000 neutrophils (range: 1-227). Antigenemia preceded clinical symptoms by 5.8 days (0-28 days). Eighteen (75%) of 24 positive patients received ganciclovir treatment: 8 patients (26.7%) for viral syndrome, 2 patients (33.3%) for invasive disease, and 8 patients (26.7%) as part of preemptive therapy, asymptomatic with high antigenemia values. Six pp65-positive patients with low counts were followed up until a negative result and remained asymptomatic without any specific treatment.

CONCLUSION

CMV infection was frequent after ALA treatment in this group and generally occurred late after completion of treatment. Antigenemia was a reliable tool to guide preemptive treatment in these patients, and such strategy is an alternative option compared to the prophylactic use of ganciclovir with ALA treatment.

[Early diagnosis of cytomegalovirus infections in organ recipients]

INTRODUCTION

Cytomegalovirus (CMV) infections and acute rejection of organs are the commonest complications in the early posttransplantation period. Clinical picture of CMV reactivation in organ recipients may have a dramatic course, occasionally even with a fatal outcome.

DIAGNOSIS OF CMV

In order to prevent acute rejection of organs in the posttransplantation period, patients are subjected to immunosuppressive therapy, which sustains reactivation of CMV. Thus, early diagnosis of CMV infections before clinical assay of CMV, is of crucial importance. Early diagnosis allows preventive antiviral therapy. Conventional and contemporary diagnostic tests are presented, with particular review on their interpretation and significance in prevention of CMV infections. Present serologic tests are positive a few weeks after infection, which is late for organ recipients. Cytopathogenic effects characteristic for CMV occur several weeks later. Antigenemia assay is a fast, quantitative test for detection of early CMV antigen pp65. Methods of molecular biology represent the latest innovation in the laboratory diagnosis of posttransplantation CMV infections. However, they have been in use only lately, and therefore their use and significance are still not sufficiently experienced. Standardization is thus required, in order to provide comparison between various diagnostic centres.

Clinical usefulness of human cytomegalovirus antigenemia assay after kidney transplantation

BACKGROUND

Human (H) cytomegalovirus (CMV) infections are a major cause of morbidity and mortality among kidney transplants. We performed a prospective study to evaluate the clinical usefulness of HCMV antigenemia assay for preemptive treatment after kidney transplantation.

METHODS

A total of 100 patients were followed up by HCMV antigenemia assay at posttransplantation weeks 1, 3, 5, 7, 9, 13, 17, and 21. Asymptomatic patients with positive antigenemia were observed without specific antiviral therapy.

RESULTS

Most patients had been given cyclosporine A- and prednisolone-based immunosuppressive therapy (99.0%) and were HCMV seropositive before transplantation (99.0%). A positive antigenemia assay was detected in 41 patients among 97 eligible patients. Symptomatic CMV diseases were observed in 10 of 41 patients. HCMV infections were related to history of acute rejection and use of antithymocyte globulin. HCMV-related symptoms and signs were clearly correlated with the level of antigenemia. All patients who had an HCMV antigenemia titer of higher than 50 per 400,000 leukocytes developed HCMV-related symptoms and signs during the follow-up period. This criterion showed the highest positive predictive value and specificity in the development of symptomatic HCMV infection.

CONCLUSIONS

Data suggest that HCMV antigenemia titer can be used as a useful guide to preemptive treatment of HCMV infection after kidney transplantation in HCMV-positive donor and recipient.

Cytomegalovirus disease is not a major risk factor for ischemic heart disease after renal transplantation

BACKGROUND

It has been suggested that cytomegalovirus infection increases the risk of ischemic heart disease. Both cytomegalovirus and ischemic heart disease are common after renal transplantation, suggesting a possible causal association in this population.

METHODS AND PATIENTS

We studied 1004 consecutive renal transplants with no prior history of ischemic heart disease and grafts that functioned at least 12 months. We performed univariate and multivariate analyses to examine the effect of cytomegalovirus disease and other risk factors (measured during the first posttransplant year) on the development of primary ischemic heart disease events after the first posttransplant year.

RESULTS

More than 1 year after transplantation, 116 patients (11.6%) experienced their first ischemic event (75 myocardial infarction, 12 percutaneous angioplasty, 18 bypass grafting, and 11 deaths). Patients with ischemic heart disease were more likely to have known risk factors (age, diabetes, smoking, hypercholesterolemia, systolic blood pressure, low serum albumin, and acute rejections). However, the incidence of cytomegalovirus disease was not different for those with or without ischemic heart disease (36.2% vs. 31.1%). Moreover, a similar proportion of those with and without ischemic heart disease (19.8% vs. 15.5%) had a rise in cytomegalovirus antibodies during follow-up. By multivariate analysis, risk factors for ischemic heart disease (P<0.05) were age, diabetes, smoking, low serum albumin, and two or more acute rejections during the first year. Cytomegalovirus disease was not associated with ischemic heart disease events: unadjusted relative risk=1.14 (95% confidence interval 0.78-1.67, P=0.485). After adjusting for multiple risk factors, the relative risk was 0.91 (0.60-1.37, P=0.657).

CONCLUSION

These data suggest that cytomegalovirus disease is not a significant risk factor for the development of primary ischemic heart disease after renal transplantation.

Late and atypical cytomegalovirus disease in solid-organ transplant recipients

Posttransplantation cytomegalovirus (CMV) disease typically occurs 1-4 months after solid-organ transplantation. The case definition invariably includes unexplained fever for > or =3 days, often with leukopenia. Late and atypical presentation of CMV disease has been rarely reported. Five cases of late and atypical CMV disease in heart (n = 1), liver (n = 1), and kidney (n = 3) transplant recipients occurred within a 4-month period in early 1999. These patients presented at a median of 25 months after organ transplantation (range, 6 months to 22 years). Atypical findings included absence of fever in 3 patients, elevated white blood cell counts in 4 patients, and normal platelet counts in 4 patients. Four patients were at risk for primary CMV infection, and 3 received ganciclovir prophylaxis for 3 months. One patients was treated for rejection, and 2 patients had induction muromonab-CD3 (Orthclone; Orthobiotech). Two of the patients had pulmonary CMV disease, but neither of these patients had hypoxia. Two patients had enterocolitis, one of whom had chronic colitis for a year. These cases may represent a changing epidemiology and clinical presentation of CMV disease in solid-organ transplant recipients in an era of changing immunosuppression and improved CMV disease prevention in the early posttransplantation period.

Management of cytomegalovirus infection and disease after solid-organ transplantation

Cytomegalovirus (CMV) continues to be a cause of substantial morbidity and death after solid-organ transplantation. There are 3 major consequences of CMV infection: CMV disease, including a wide range of clinical illnesses; superinfection with opportunistic pathogens; and injury to the transplanted organ, possibly enhancing chronic rejection. This article discusses the considerable progress that has been made in elucidating risk factors for CMV disease, in the rapid detection of CMV in clinical specimens, and in the use of antiviral chemotherapy and immunoglobulin to prevent and treat CMV disease after solid-organ transplantation.

Comparison of quantitative and qualitative PCR assays for cytomegalovirus DNA in plasma

We analyzed the performance characteristics of the qualitative AMPLICOR CMV Test (Roche Molecular Systems, Pleasanton, Calif.) and quantitative COBAS AMPLICOR CMV MONITOR Test (Roche Molecular Systems) assays and compared the performance of the AMPLICOR quantitative assay with an in-house-developed cytomegalovirus (CMV) DNA PCR assay. The quantitative AMPLICOR assay was found to be more sensitive than the qualitative AMPLICOR assay. The quantitative AMPLICOR assay has a lower limit of sensitivity of 400 CMV DNA copies/ml of plasma and is linear to 50,000 CMV DNA copies/ml of plasma. Compared to the in-house PCR assay, the AMPLICOR quantitative assay gave lower viral load values at all concentrations tested, but the difference between the two assays was not consistent across the entire dynamic range of the AMPLICOR quantitative assay. At the lower end of the assay, the viral load values obtained with the in-house PCR assay were three- to fivefold (0.5 to 0.7 log units) higher than those measured with the AMPLICOR assay. At higher input concentrations, the differences between the two assays approached 10-fold. This direct comparison of the in-house assay and the quantitative AMPLICOR assay provides the ability to compare previously published in-house data with an assay widely available for future research and clinical monitoring of patients with CMV infections.

Comparison between antigenemia and a quantitative-competitive polymerase chain reaction for the diagnosis of cytomegalovirus infection after heart transplantation

BACKGROUND

Antigenemia and quantitative polymerase chain reaction (PCR) are widely used for cytomegalovirus (CMV) diagnosis after heart transplantation due to their enhanced predictive values for disease detection when specific cut-off values are used. The purpose of this study was to compare, in the same patient setting, the predictive values of quantitative PCR and antigenemia for CMV disease detection, using specific cut-off values.

METHODS

Thirty heart transplant receptors were ch prospectively monitored for active CMV infection and disease detection, using quantitative PCR and anti- po genemia. Positive and negative predictive values for pr CMV disease detection were calculated using cut-off pr values for both antigenemia (5 and 10 positive cells/300,000 neutrophils) and quantitative-PCR (50,000 and 100,000 copies/10(6) leukocytes).

RESULTS

Active CMV infection was diagnosed in 93.3% of patients and CMV disease in 23.3%. The positive and negative predictive (%) values for CMV disease detection were 35/100 and 46.7/100, respectively, for quantitative PCR and antigenemia. Using 5 and 10 positive cells/300,000 neutrophils as cut-off values for antigenemia, the positive and negative predictive values (%) for disease detection were respectively 63.6/100 and 70/100. For quantitative PCR, the positive and th negative predictive values (%) for cut-off values of to 50,000 and 100,000 copies/10(6) leukocytes were 53.8/100 and 60/94.1, respectively.

CONCLUSION

In our series, antigenemia and quantitative-PCR had enhanced and similar predictive values for CMV disease detection when specific cut-off values were used. The choice between these two methods for disease detection may rely less on their efficiency and more on the experience and familiarity with them.

Predictive value of quantitative PCR-based viral burden analysis for eight human herpesviruses in pediatric solid organ transplant patients

Human herpesviruses can cause significant morbidity and mortality in pediatric solid organ transplant recipients. It was hypothesized that viral burden quantification by polymerase chain reaction using an internal calibration standard could aid in distinguishing between viral disease and latency. Here we report the results of a 2-year prospective study of 27 pediatric solid organ (liver, kidney, or heart) transplant recipients in which multiple samples were analyzed for levels of all eight human herpesviruses by internal calibration standard-polymerase chain reaction. Herpes simplex viruses 1 and 2, varicella-zoster virus, and Kaposi's sarcoma-associated herpesvirus were not detected in any of these samples. Human herpesvirus types 6 and 7 were detected in half of the patients, but were present at low levels, similar to those found in reference populations. Epstein-Barr virus (EBV) and cytomegalovirus (CMV) were detected in 89% and 56% of the patients, respectively. Viral burden analysis suggested distinct patient populations for CMV, with a natural cutoff of 10,000 viral targets/ml blood strongly associated with disease. In some cases, a dramatic increase in CMV levels preceded clinical evidence of disease by several weeks. EBV viral burden was relatively high in the only patient presenting with an EBV syndrome. However, two other patients without evidence of EBV disease had single samples with high EBV burden. Rapid reduction in both EBV and CMV burden occurred with antiviral treatment. These data suggest that viral burden analysis using internal calibration standard-polymerase chain reaction for CMV, and possibly other herpesviruses, is an effective method for monitoring pediatric transplant patients for significant herpesvirus infection and response to therapy.

Analytical performance and clinical utility of a nucleic acid sequence-based amplification assay for detection of cytomegalovirus infection

A nucleic acid sequence-based amplification (NASBA) assay for qualitative detection of human cytomegalovirus (CMV) pp67 mRNA was evaluated in a multicenter study. Negative results were obtained for all specimens from 50 CMV-seronegative and 50 CMV-seropositive low-risk whole-blood donors. No interference with CMV mRNA amplification was observed in the testing of 288 specimens containing various potential interfering substances, nonspecifically reacting substances (including mRNA from other herpesviruses), and three anticoagulants. A total of 95% (50 of 51) of CMV-positive (cell culture- and antigenemia immunofluorescence [AG-IFA]-positive) clinical specimens were positive by the NASBA assay. Results from different operators over multiple testing days were consistent for each of four panel members containing different concentrations of CMV mRNA, indicating the reproducibility of the assay. The estimated 95% reliable upper detection limit of the assay was 600 mRNA copies; the lower limit of detection was less than 25 mRNA copies. The clinical utility of the assay was evaluated with longitudinally collected specimens from solid-organ transplant patients (n = 21). A total of 98% (81 of 83) of the specimens from CMV-negative patients were negative by the NASBA assay, while 90% (10 of 11) of patient specimens that were positive by cell culture or AG-IFA were positive by the NASBA assay. Positive NASBA assay results were obtained earlier than AG-IFA or cell culture results for 55% of the patients and at the same time for the remainder of the patients (45%). The overall agreement between the NASBA assay and current reference tests was 86% when active CMV infection was present. These studies indicate that the CMV pp67 mRNA NASBA assay has reproducible and sensitive performance characteristics that should enable more rapid diagnosis of CMV infection.

Real-time automated PCR for early diagnosis and monitoring of cytomegalovirus infection after bone marrow transplantation

The purpose of this study was to assess the usefulness of real-time automated PCR as a quantitative, highly reproducible, and sensitive method to detect cytomegalovirus (CMV) DNA in blood specimens. Intra- and interassay precision rates were 0.89% (small number of copies [L]), 1.43% (middle number of copies [M]), and 1.12% (high number of copies [H]), and 4.46% (L), 1.51% (M), and 2.28% (H), respectively. The linearity of this assay was obtained between 10 and 10(7) copies/well, with a minimum detection limit of 20 copies/well. Specimens from 55 of 70 healthy subjects were found to be positive for CMV antibody, but CMV DNA was not detected in any of them. In the qualitative assessment of each specimen, the results of the CMV antigenemia assay and those of the real-time PCR assay agreed in 80% (plasma specimens), 79% (all nucleated cells), and 86% (blood) of the cases examined. For eight patients diagnosed as having CMV infection or disease, no sample was positive in the antigenemia assay earlier than in the real-time PCR assay. Furthermore, the results of this assay could be obtained within 8 h. We concluded that the real-time PCR assay is useful for rapid diagnosis of CMV infection and monitoring of clinical courses.

Comparison of quantitative cytomegalovirus (CMV) PCR in plasma and CMV antigenemia assay: clinical utility of the prototype AMPLICOR CMV MONITOR test in transplant recipients

The correlation between the prototype AMPLICOR CMV MONITOR test (Roche Molecular Systems), a quantitative PCR assay, and the cytomegalovirus (CMV) pp65 antigenemia assay was evaluated in transplant recipients. Sequential blood specimens were collected on 29 patients (491 specimens), the leukocyte fraction was tested by CMV antigenemia, and quantitative PCR was performed on plasma specimens. None of the 15 patients (242 specimens) who were antigenemia negative were positive for CMV DNA by PCR, and none of these patients developed active CMV disease. There were 14 antigenemia-positive patients, 8 of whom developed active CMV disease. In all patients, there was a good association between the antigenemia and PCR assays. Ganciclovir-resistant virus was isolated from three patients with active CMV disease. These three patients had persistently elevated levels of antigenemia and CMV DNA by PCR when resistance to ganciclovir developed. This standardized, quantitative CMV PCR assay on plasma has clinical utility for the diagnosis of active disease and in monitoring the response to antiviral therapy in transplant recipients.

Low dose antithymocyte globulins in renal transplantation: daily versus intermittent administration based on T-cell monitoring

BACKGROUND

Despite the long history of use of antithymocyte globulins (ATG) in renal transplantation, ideal doses and duration of ATG administration based on the monitoring of T lymphocytes have yet to be defined.

METHODS

Two immunosuppressive regimens based on low-dose rabbit ATG (Thymoglobuline; Imtix-Sang-stat, Lyon, France) were assessed during the first year after transplantation: daily ATG (DATG; n=23) where 50 mg of ATG was given every day and intermittent ATG (IATG; n=16) where similar doses of ATG were given for the first 3 days and then intermittently only if CD3+ T lymphocytes (measured by flow cytometry) were > 10/mm3. Both groups received steroids, azathioprine, and cyclosporine.

RESULTS

ATG-induced depletion was similar for peripheral blood lymphocytes and T cells in both groups: it began at day 1 after transplantation, was submaximal at day 3, and reached maximum intensity between days 6 and 8, from which time cell counts progressively increased. However, T-cell depletion was still present at day 20. The total ATG dose per patient (381.5+/-121 vs. 564+/-135 mg/patient) and the mean cumulative daily dose of ATG (0.60+/-0.17 vs. 0.80+/-0.14 mg/kg/day) were significantly lower in the IATG group (P=0.0001 and 0.0006, respectively). The overlap of ATG and cyclosporine treatment was 6.7+/-3 vs. 7.4+/-4.3 days (P=NS), and the mean duration of ATG therapy was 11.3+/-3.2 vs. 11.6+/-2.7 days in the IATG and DATG groups, respectively (P=NS). ATG was given in an average of one dose every 1.6 days in the IATG group compared with one dose daily in the DATG group (P=7 x 10(-7)). There was no significant difference in renal graft function, the number of acute graft rejections, or ATG-related side effects and complications. Despite the daily immunological follow-up, there was a net saving of $760/patient in the cost of treatment in the IATG group.

CONCLUSION

IATG had the advantage of a reduction in the dose of ATG and in the cost of treatment, while offering similar T-cell depletion and effective immunosuppression. This approach could be proposed as an induction protocol, particularly for patients with poor graft function in whom cyclosporine introduction has to be delayed or those with increased risk of cytomegalovirus infections or secondary malignancies.

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.

Cytomegalovirus PP65 antigenemia monitoring as a guide for preemptive therapy: a cost effective strategy for prevention of cytomegalovirus disease in adult liver transplant recipients

BACKGROUND

The aim of the study was to assess the incidence of cytomegalovirus (CMV) infection and disease in adult liver transplant recipients, using routine preemptive therapy guided by the pp65 antigenemia test.

METHODS

Antigenemia was monitored weekly after liver transplantation (OLTX) for the first 3 months, and once a month for another 3 months. CMV seronegative recipients were treated preemptively for the first positive antigenemia. Seropositive recipients were treated only when their antigenemia count reached a threshold of > or =100 positive cells per 200,000 leukocytes.

RESULTS

A total of 144 patients were included between June 1994 and April 1995, of which 137 (95%) were primary OLTX. The percentage of positive antigenemia and CMV disease was 55 and 8%, respectively. Seventy-eight (54%) patients were protocol-monitored for the entire follow-up (group 1) and received appropriate preemptive therapy, although 66 (46%) patients had protocol violation by having missed blood samples or blood drawn at unscheduled times (group 2). Using Cox's proportional hazards model, patients with a first antigenemia count of >11 leukocytes had a significantly higher rate of CMV disease compared to patients with an antigenemia count < or =11 leukocytes (RR = 7.3, 95% confidence interval = 2.2 to 24.5). In a multivariate Cox regression analysis, adjustments were made to control for: group 1 versus group 2, use of OKT3, and serology risk categories. This analysis showed that the relative rate of CMV disease was still significantly higher among patients with antigenemia count >11 leukocytes (adjusted RR = 4.9, 95% confidence interval = 1.3 to 18.1). The estimated cost of preemptive therapy was less than that of prophylaxis with i.v. (14-day course) or oral (90-day course) ganciclovir.

CONCLUSIONS

Preemptive therapy guided by pp65 antigenemia is a useful and cost effective strategy for prevention of CMV disease.

Prevention and treatment of cytomegalovirus infection in organ transplant recipients

Cytomegalovirus (CMV) is the most common viral pathogen in organ transplant recipients. The patients at highest risk of developing CMV disease are seronegative recipients of seropositive donors, and seropositive recipients who receive antilymphocyte agents such as OKT3 and antithymocyte globulin (ATG) for induction or for rejection. There have been many trials of CMV prevention, but they are difficult to compare with one another because of variability in definitions and end points. Two modalities that have been used to prevent CMV disease are prophylaxis and preemptive therapy. In prophylaxis all patients are given an antiviral agent in order to prevent CMV disease, while in preemptive therapy (also called targeted prophylaxis) only patients who are identified as 'high risk' are selected for treatment. Selected trials of prophylaxis and preemptive therapy in solid-organ recipients are reviewed. The factors to be considered in using one modality or the other are side effects from antivirals, cost of monitoring and antivirals, efficacy of the two modalities, and potential emergence of drug resistance. Sensitive tests that have been used for early diagnosis and monitoring of CMV are antigenemia and the polymerase chain reaction (PCR). Antigen pp65 is a lower matrix protein and can be detected in peripheral blood leukocytes. The sensitivity and specificity are high and vary from 89% to 100% and 92% to 96%, respectively. Currently, many authors believe that the antigenemia test is more useful than the PCR test. The antigenemia test is useful for viral monitoring as a guide for preemptive therapy after organ transplantation. Persistence of high counts of antigenemia may indicate inadequate antiviral therapy or emergence of resistance. Recurrence of positive antigenemia after treatment of CMV disease can be a sign of relapse. Transplant patients who develop resistance to antiviral drugs are usually seronegative recipients who receive an organ from a seropositive donor and have several courses of antivirals for CMV disease. Ganciclovir is the most frequent antiviral agent used in transplant recipients and is usually well tolerated. Resistance to ganciclovir may occur and is usually secondary to virus mutation in the UL97 gene. The availability of sensitive diagnostic tests such as pp65 antigenemia has made the early diagnosis of CMV possible in organ transplant recipients. CMV is being treated much earlier now, and progression to disseminated disease is uncommon. Prudent use of antiviral drugs will hopefully limit the problem of drug resistance.