New molecular assays to predict occurrence of cytomegalovirus disease in renal transplant recipients

Distinct expression profile of HCMV encoded miRNAs in plasma from oral lichen planus patients

Background

Oral lichen planus (OLP) is a T cell-mediated autoimmune disease. The aetiology and molecular mechanisms of OLP remain unclear. Human cytomegalovirus (HCMV) infection is a causal factor in the development of various diseases, but the clinical relevance of HCMV in OLP has not been thoroughly investigated.

Methods

In the present study, we firstly examined twenty-three HCMV-encoded microRNA (miRNA) expression profiles in plasma from training set that including 21 OLP patients and 18 healthy controls using RT-qPCR technology. Dysregulated miRNAs were subsequently confirmed in another larger cohort refereed as validation set consisting of 40 OLP patients and 33 healthy controls. HCMV DNA in peripheral blood leukocytes (PBLs) was also measured in an additional cohort of 13 OLP patients and 12 control subjects. Furthermore, bioinformatics analyses, luciferase reporter assay and western blotting were also performed to predict and verify the direct potential targets of HCMV-encoded miRNAs.

Results

The RT-qPCR results showed that the plasma levels of five HCMV-encoded miRNAs including hcmv-miR-UL112-3p, hcmv-miR-UL22a-5p, hcmv-miR-UL148d, hcmv-miR-UL36-5p and hcmv-miR-UL59 were significantly increased in OLP patients in both training and validation sets. HCMV DNA in PBLs was also significantly higher in OLP patients than in control subjects. Additionally, by using a combination of luciferase reporter assay and western blotting, we demonstrated that cytomegalovirus UL16-binding protein 1, a molecule that mediates the killing of virus-infected cells by natural killer cells, is a direct target of hcmv-miR-UL59.

Conclusions

Our results demonstrate a distinct expression pattern of HCMV-encoded miRNAs in OLP patients, which may provide insight into the relationship between HCMV infection and OLP, and warrants additional study in the diagnosis and aetiology of OLP.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1222-8) contains supplementary material, which is available to authorized users.

Detection of human cytomegalovirus DNA in various blood components after liver transplantation

The quantification of human cytomegalovirus (HCMV DNA) by real-time PCR is currently a primary option for laboratory diagnosis of HCMV infection. However, the optimal sample material remains controversial due to the use of different PCR assays. To explore the best blood component for HCMV DNA surveillance after liver transplantation, whole blood (WB), serum (SE), and plasma (PL) specimens were collected simultaneously from targeted patients and examined for HCMV DNA using one commercially available assay. The HCMV DNA-positive rate with WB (16.67%) was higher than that with either SE or PL (8.33%, both P<0.01). Quantitative DNA levels in WB were of greater magnitude than those in SE (WB-SE mean log-transformed difference, 0.99; 95%CI=0.74-1.25; P<0.0001) and PL (WB-PL mean log-transformed difference, 1.37; 95%CI=1.07-1.66; P<0.0001). Dynamic monitoring revealed that HCMV DNA in WB was positive sooner and had higher values for a longer period of time during therapy. With earlier positive detection, higher sensitivity, and yield of greater viral loads, WB compared favorably to SE or PL and hence is recommended as the superior material for HCMV DNA surveillance after liver transplantation. In addition, infant recipients require more intensive monitoring and prophylactic care because of their higher susceptibility to primary HCMV infection.

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.

Quantification of cytomegalovirus viral load

Cytomegalovirus (CMV), a member of the Herpesviridae family, is worldwide distributed. After the primary infection, CMV induces a latent infection with possible reactivation(s). It is responsible for severe to life-threatening diseases in immunocompromised patients and in foetuses and newborns of infected mothers. For monitoring CMV load, classical techniques based on rapid culture or pp65 antigenemia are progressively replaced by quantitative nuclear acid tests (QNAT), easier to implement and standardize. A large variety of QNAT are available from laboratory-developed assays to fully-automated commercial tests. The indications of CMV quantification include CMV infection during pregnancy and in newborns, and viral surveillance of grafted and non-grafted immunocompromised patients, patients with bowel inflammatory diseases and those hospitalised in intensive care unit. A close cooperation between virologists and clinicians is essential for optimizing the benefit of CMV DNA monitoring.

Prediction of cytomegalovirus (CMV) plasma load from evaluation of CMV whole-blood load in samples from renal transplant recipients

In a prospective cohort of 82 renal transplant recipients, we evaluated the capacity of the cytomegalovirus (CMV) load in whole blood (WB) to predict the plasma CMV load, aiming to identify active CMV infections by using WB samples only and to deduce a WB threshold. Using quantitative real-time PCR, a total of 1,474 WB samples were assayed, of which 279 were positive for CMV, and 140 out of the 276 paired plasma samples tested positive. Thirty (36.6%) patients presented with at least one positive plasma PCR result, and 21 infection episodes (19 patients) required curative treatment (median follow-up time, 12 months). When the plasma CMV load was >500 copies/ml (n = 70), more than 94% (95% confidence interval, 86.0%, 98.4%) of WB samples had >500 copies/ml. Two prediction models were built: log(10) plasma viral load (VL) was calculated as -0.3777 + 0.9342 x log(10) WB VL and as -0.3777 + 0.8563 x log(10) WB VL for patients with and without treatment, respectively. In the validation sample (578 routine samples), 77.2% of the observed and expected plasma viral loads were concordant (95% confidence intervals, 73.5 and 80.5%). According to the model, the plasma viral load was >500 copies/ml when the WB load was >3,170 or >4,000 copies/ml in patients with or without treatment, respectively. WB seems to be an appropriate candidate for routine CMV monitoring of transplant recipients by using a single assay.

Association of Elevated Pretransplant sCD30 Levels With Graft Loss in 206 Patients Treated With Modern Immunosuppressive Therapies After Renal Transplantation

BACKGROUND

Recent reports suggest that high pretransplant serum levels of soluble CD30 (sCD30) are a risk factor for rejections after kidney transplantation. The aim of our study was to elucidate the predictive value of pretransplant sCD30 levels for kidney transplantation outcome in a single-center patient cohort that has been treated with modern immunosuppressive therapies after transplantation.

METHODS

We retrospectively analyzed sCD30 in multiple pretransplant sera from 206 patients, of whom 174 were transplanted with a cadaveric kidney and 32 patients received an allograft from a living donor. Renal function after transplantation was estimated by measuring serum creatinine and by rejection diagnosis.

RESULTS

We could demonstrate a statistically significant association between increased pretransplant sCD30 values and graft failures (P=0.005). Receiver operating curve analysis revealed a cutoff value of 124 U/mL pretransplant sCD30. A multivariate analysis confirmed pretransplant sCD30 values >124 U/mL (P=0.011) and rejection episodes (P<0.0001) as independent risk factors for graft loss.

CONCLUSION

Our study revealed a strong correlation between pretransplant sCD30 levels and the incidence of graft failure, but we could not confirm that the development of rejection episodes is correlated with pretransplant sCD30 values.

Diagnostic value of reverse transcription-PCR for detection of cytomegalovirus pp67 in samples from solid-organ transplant recipients

We evaluated a highly sensitive quantitative real-time one-step reverse transcription-PCR (RT-PCR) for detection of human cytomegalovirus pp67 transcripts in monitoring of solid-organ transplant recipients. Results were compared with those of pp65 antigen testing and quantitative DNA-PCR. Due to a low clinical sensitivity, the pp67 RT-PCR was not able to replace these assays.

Clinical utility of CMV early and late transcript detection with NASBA in bronchoalveolar lavages

BACKGROUND

Cytomegalovirus (CMV) infection can cause severe disease in immunocompromised individuals, with CMV pneumonia, most commonly seen in lung or bone marrow transplant recipients, carrying a particularly high fatality rate. Early and accurate diagnosis of CMV pneumonia is therefore critical.

OBJECTIVES

Current diagnostic tests for CMV pneumonia in bronchoalveolar lavage (BAL) specimens are either insensitive or poor prognostic indicators of disease. We therefore examined nucleic acid sequence-based amplification (NASBA) assays for CMV transcripts in BAL for the prediction of CMV pneumonia and associated diseases.

STUDY DESIGN

A total of 220 BAL specimens from lung transplant recipients and other patients with suspected viral pneumonia were studied. Ninety-nine samples had previously tested positive for CMV by shell vial (SV) culture, while the other 121 had tested negative. All specimens were assayed for CMV pp67 and immediate early (IE) transcripts by NASBA. Results were correlated with evidence of concurrent or subsequent CMV pneumonia, rejection, and infection with other microbes.

RESULTS

From a total of 220 BAL specimens, 27 tested positive for pp67 mRNA, 25 tested positive for IE mRNA, and 17 tested positive for both. Only 10 specimens tested positive for CMV by either or both NASBA assays while testing negative by SV assay. However, 74 specimens were SV positive but negative in both NASBA assays. Detection of CMV by any of the three methods was associated with an increased prevalence of pneumonia (i.e., pulmonary interstitial inflammation with radiographic or clinical evidence of lung injury), but not with pulmonary CMV pathology. Detection of CMV by SV was associated with moderate to severe graft rejection. There was no evidence of increased bacterial or fungal pulmonary infections associated with a positive CMV result by any of the three assays.

CONCLUSIONS

Detection of either CMV pp67 or IE mRNA transcripts by NASBA in BAL specimens can occasionally identify CMV infections that are negative by conventional shell vial culture, but does not have sufficient sensitivity or positive predictive value to be employed routinely for pre emptive management of pulmonary CMV disease in transplant recipients.

Whole blood real-time quantitative PCR for cytomegalovirus infection follow-up in transplant recipients

BACKGROUND

Cytomegalovirus (CMV) remains a major opportunistic agent among transplant recipients. While detection of CMV pp65-lower matrix protein (pp65Ag) is still widely used for monitoring CMV infection, real-time PCR assays have been recently developed for routine quantitation of CMV DNA. However, correlations are lacking between results of pp65Ag and quantitative PCR assays and there is no consensus yet as to the more appropriate blood compartment (whole blood (WB), leukocytes, plasma) to be tested with PCR assays.

OBJECTIVES

The aims of the study were to determine, in a population of transplant recipients: (i) the correlation between pp65Ag and CMV quantitative real-time PCR in our setting and (ii) the utility of plasma CMV DNA quantitation in comparison to WB quantitation.

METHODS

In 170 blood samples (from 61 solid organ or bone marrow transplant recipients) with pp65Ag results, CMV quantitation was performed in WB and plasma using an in-house real-time quantitative PCR.

RESULTS

Real-time PCR and pp65Ag results in WB were correlated: thresholds of 10 and 50(+) cells/200,000 cells were equivalent to 3.3 log(10)copies/mL (2,000 copies/mL) and 3.8 log(10)copies/mL (6,300 copies/mL), respectively. When WB viral load was >or=3.6 log(10)copies/mL, the risk to have a negative plasma CMV DNA result was <or=2.5%.

CONCLUSIONS

For the routine exploration of a single compartment, whole blood would represent a suitable compromise: easy processing for a sensitive assay. The 3.6 log(10)copies/mL threshold, which could help in identifying active CMV infection, deserves further evaluation.

Clinical utility of cytomegalovirus (CMV) serology testing in high-risk CMV D+/R- transplant recipients

Late-onset cytomegalovirus (CMV) disease is a significant problem in D+/R- solid organ transplant (SOT) patients who receive antiviral prophylaxis. We assessed the clinical utility of CMV IgG and IgM serology testing for predicting late-onset CMV disease. We evaluated 352 D+/R- transplant recipients who participated in a trial comparing 100 days of ganciclovir versus valganciclovir prophylaxis. CMV serology was assessed on day 28, 56, 100, and 6 and 12 months post-transplant. IgG seroconversion occurred in 26.9% of patients by day 100, and in 63.4% and 75.3% by 6 and 12 months, respectively. IgM seroconversion occurred in 8.3%, 41.8% and 54.9% by day 100, month 6 and month 12, respectively. Seroconversion by day 100 (end of prophylaxis) was not predictive of subsequent CMV disease (CMV disease 13.3% if seropositive vs. 17.8% if seronegative; p = NS). However, at 6 months post-transplant, IgG serostatus was predictive of subsequent CMV disease between month 6 and 12 (CMV disease 1.3% if seropositive vs. 10.0% if seronegative; p = 0.002). In D+/R- patients, CMV serology testing is for the most part not clinically useful for predicting subsequent disease. However, seroconversion by 6 months may be useful for identifying patients at risk of late-onset CMV disease.

Quantitative pp65 antigenemia in the diagnosis of cytomegalovirus disease: prospective assessment in a cohort of solid organ transplant recipients

OBJECTIVES

To assess the accuracy of quantitative pp65 antigenemia (pp65Ag) in the diagnosis of CMV disease, in a cohort of solid-organ transplant recipients.

METHODS

Prospective observational study during the first 6 months following transplantation, with determination of pp65Ag at weeks 2, 4, 6, 8, 10, 11, 12, 14 and 16. Sensitivity (S), specificity (E), positive and negative predictive values (PPV, NPV), and the optimal cut-off point for diagnosing CMV disease, were determined.

RESULTS

The cohort consisted of 35 liver, 26 renal and 12 heart graft recipients. Thirteen (17.2%) were seronegative and received a seropositive graft. Of 583 blood samples, pp65Ag was positive in 109 (18.7%) from 37 patients (51%). Twenty-two patients developed CMV disease (0.3 episodes/patient); gastrointestinal disease was the most frequent (15 episodes), followed by viral syndrome (3 episodes). Patients with positive pp65Ag had a relative risk for CMV disease of 6.19 [IC95%=1.99-19.04], (P=.0001). Diagnostic values of pp65Ag were: S=86%, E=65%, PPV=51%, NPV=92%. The cut-off of > or =10 infected cells/10(5), at weeks 2, 4, 6 and 8 obtained the best PPV (0, 67, 91 and 54%), and NPV (47, 52, 67 and 50%).

CONCLUSIONS

In the studied population, the presence of positive pp65Ag was associated with a high risk of developing CMV disease, and the most useful cut-off point for the diagnosis was > or =10 infected cells/10(5).

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.

Assessment of CMV load in solid organ transplant recipients by pp65 antigenemia and real-time quantitative DNA PCR assay: Correlation with pp67 RNA detection

After bone marrow (BM) or solid-organ (SO) transplantation viremic Cytomegalovirus (CMV) infection is observed frequently. Quantitative assay of CMV in blood helps the management of this clinical condition. In the present report, 83 samples from 39 solid organ recipients, three CMV assays were compared simultaneously for the first time: the Nuclisens CMV pp67 assay (nucleic acid sequence-based amplification, NASBA), an "in-house" quantitative real-time PCR assay (TaqMan) for CMV DNA, and pp65 antigenemia. The relation between CMV DNA and pp65 antigenemia, the quantitative assays, was evaluated on a larger group including 251 blood samples from 118 solid organ recipients. Real-time PCR provided the best results; > or =130 CMV DNA copies/2 x 10(5) peripheral blood leukocytes (PBLs) predicted > or =1 pp65 antigen positive (Ag+) cell/2 x 10(5) PBLs. By taking pp65 antigenemia as the "gold standard," the sensitivity of CMV DNA quantitation and of the pp67 RNA assay were 0.95 and 0.20, respectively, while the corresponding specificity values were 0.50 and 0.93. When real-time PCR was considered as the "gold standard," the sensitivity and specificity of the pp65 antigenemia were 0.65 and 0.91, respectively. Among the three tests examined, the sensitivity of the pp67 RNA assay was the lowest. On the other hand, the pp67 RNA assay was highly specific and effective in pinpointing high viremia patients. The present report, by providing predictive values for all three diagnostic profiles, DNA load, antigenemia, and pp67RNA, is a contribution for validation of real-time PCR as a new standard for quantitative assessment of CMV viremia in clinical settings.

Clinical utility of cytomegalovirus viral load testing for predicting CMV disease in D+/R- solid organ transplant recipients

Despite prophylaxis, cytomegalovirus (CMV) disease is common in donor seropositive (D+)/recipient seronegative (R-) transplant patients after cessation of prophylaxis. Early detection of CMV may allow for pre-emptive therapy to prevent active disease. The clinical utility of quantitative plasma viral load measurements for predicting CMV disease was determined in 364 D+/R- organ transplant patients receiving prophylaxis (100 d of valganciclovir or oral ganciclovir). Measurements were performed every 2 weeks until day 100 and at months 4, 4.5, 5, 6, 8 and 12 post-transplant. CMV disease occurred in 64 (17.6%) patients by 12 months. Using a positive cut-off value of >400 copies/mL, sensitivity was 38%, specificity 60%, positive predictive value 17%, and negative predictive value 82% for prediction of CMV disease. Therefore, routine monitoring would have predicted disease in only 24/64 (38%) patients. The test characteristics were not improved by changing the viral load cut-off point for defining a positive result. Similarly, single time point measures at the end of prophylaxis or month 4 had low sensitivity for disease prediction. Overall, regular CMV plasma viral load measurements were only of modest value in predicting CMV disease.

Comparison of DNA amplification, mRNA amplification, and DNA hybridization techniques for detection of cytomegalovirus in bone marrow transplant recipients

A total of 676 specimens from 63 recipients of bone marrow allografts were tested for cytomegalovirus (CMV) by the following assays: CMV pp67 NucliSens (NS), AMPLICOR CMV MONITOR (RA), and the Digene CMV DNA test (DG). In a consensus analysis, the sensitivities and specificities were 60 and 99% (NS), 96 and 98% (RA), and 90 and 76% (DG), respectively; for detection of symptomatic CMV infection, they were 60 and 97% (NS), 65 and 97% (RA), and 95 and 77% (DG), respectively. In multivariate analysis, the major risk factor for symptomatic CMV infection was an increase in the viral load in the DG assay; in univariate analyses, maximum viral loads in both DG and RA assays and a rising viral load in the RA assay were also significant. The earliest detection of CMV replication was provided by the RA assay (mean, 39 days posttransplantation), followed by the DG assay (mean, 48 days) and the NS assay (mean, 58 days).

Automated extraction and quantification of human cytomegalovirus DNA in whole blood by real-time PCR assay

The measurement of human cytomegalovirus (HCMV) DNA in blood is becoming the standard method for monitoring HCMV infection in immune-suppressed and unsuppressed patients. As various blood compartments can be used, we have compared the HCMV DNA measured in whole blood (WB), peripheral blood leukocytes (PBL), and plasma by real-time PCR. We tested 286 samples: HCMV DNA was extracted automatically from WB and PBL with the MagNA Pure instrument (Roche Molecular Biochemicals) and manually from plasma samples. The HCMV DNA from WB, PBL, and plasma was measured by real-time Light Cycler PCR. Primers and probe were located in the UL 83 region. HCMV DNA was detected more frequently in WB (88.5%) than in the PBL (65.7%) (P < 0.0001) or the plasma (55.2%) (P < 0.0001). There was a good correlation between the positive results in WB and in PBL (r = 0.68; P < 0.0001), and 3.15 log(10) genome copies in 200000 PBL, equivalent to the threshold value of 50 pp65-positive polymorphonuclear cells per 200000 leukocytes, was equivalent to 3.4 log(10) genome copies in 200 microl of WB. WB was shown to be suitable for automated extraction and the quantitation of HCMV DNA by real-time Light Cycler PCR by analysis of serial samples from representative patients of various populations. This system may be very useful for monitoring of immune-suppressed and unsuppressed patients.

Comparison of LightCycler-based PCR, COBAS amplicor CMV monitor, and pp65 antigenemia assays for quantitative measurement of cytomegalovirus viral load in peripheral blood specimens from patients after solid organ transplantation

In order to evaluate the LightCycler-based PCR (LC-PCR) as a diagnostic assay technique, a classical pp65 antigenemia assay and the commercially available COBAS Amplicor CMV Monitor (CACM) assay were compared to the LC-PCR assay for the detection and quantitation of cytomegalovirus (CMV) load in 404 parallel specimens of peripheral blood from 66 patients after solid organ transplantation. A good correlation existed among these three assays (r congruent with 0.6, P < 0.0001). The LC-PCR assay was the most sensitive (54% of specimens positive) compared to the CACM (48.6%) and the pp65 antigenemia (26%) assays. The LC-PCR assay detected all samples found positive by using both the CMV pp65 antigenemia assay and the CACM assay. The LC-PCR also had the widest dynamic range (from 250 to 10(7) DNA copies/ml of plasma). No cross-reactions were found among CMV and Epstein-Barr virus, varicella-zoster virus, or herpes simplex virus in the LC-PCR by using amplification with specifically designed primer pairs. Precision, expressed as the coefficient of variation, was <3% with standard DNA from cell cultures and between 6.55 and 14.1% with clinical specimens in repeat LC-PCR runs. One run of the LC-PCR took half of the time required for the semiautomated CACM procedure. Because of its sensitivity, specificity, cost-effectiveness, and simplicity, the LC-PCR assay could replace the pp65 antigenemia and the CACM assays as the preferred technique for the surveillance, diagnosis, and monitoring of response of CMV diseases in high-risk populations.

A real-time TaqMan PCR for routine quantitation of cytomegalovirus DNA in crude leukocyte lysates from stem cell transplant patients

A real-time TaqMan PCR based on the cytomegalovirus (CMV) polymerase (pol) gene was developed for quantitation of CMV DNA in crude peripheral blood leukocyte (PBL) lysate from stem cell transplantation (SCT) patients. The dynamic range of the assay was between 10 and 4x10(6) copies. Both intra- and inter-assay variability were well within +/-0.25 log10 S.D. Thus, a pooled PBL sample that was used as positive control in 57 consecutive TaqMan PCR runs over 7 months showed a stable CMV quantity (4.12+/-0.13, log10 mean+/-S.D.). The sensitivity of the pol TaqMan PCR was validated by parallel analysis of 177 PBL samples with a nested PCR. The use of crude PBL lysate as PCR input did not cause PCR inhibition. We demonstrated further the clinical utility of the newly developed TaqMan PCR by monitoring changes in CMV levels in eight patients receiving antiviral therapy. This TaqMan PCR was highly sensitive, reproducible, and stable and has served a useful tool for monitoring CMV DNA levels in large number of clinical samples in a routine diagnostic setting for over 1 year.

Quantitation of human cytomegalovirus in recipients of solid organ transplants by real-time quantitative PCR and pp65 antigenemia

Human cytomegalovirus (HCMV) infections and anti-HCMV treatment are usually monitored by measuring pp65 antigenemia. This method is time-consuming, labour-intensive and requires skilled operators. We have compared results obtained using real-time Light Cycler quantitative PCR (QPCR) and the pp65 antigen assay on serial samples collected from recipients of solid organ transplants. We collected 198 blood samples from 14 solid organ transplant recipients and assayed them for pp65 antigen and with Light Cycler PCR. HCMV DNA was extracted from leukocytes and measured using primers and probe located in the UL83 region. The quantity of HCMV DNA was calculated using a standard curve prepared from a plasmid containing the target sequence. There was a good correlation between the number of pp65-positive cells and the DNA copy number (r = 0.57, P < 0.0001). A clinical threshold of 50 positive polymorphonuclear leukocytes/200,000 cells was equivalent to two log10 genome copies per capillary by Light Cycler PCR. HCMV DNA was detected before pp65 antigen in three patients at a mean time of 10 days, whereas the two tests were positive simultaneously for eight patients. Both the pp65 antigen data and DNA copy number decreased over time during antiviral treatment, although the QPCR was positive 28.2 days after the pp65 antigen assay had become negative. The real-time Light Cycler quantitative PCR assay is a rapid and labour-saving technique. This molecular method could be useful for monitoring infections and antiviral treatment in recipients of solid organ transplants.

Human cytomegalovirus DNA in plasma and serum specimens of renal transplant recipients is highly fragmented

Quantitation of cytomegalovirus (CMV) DNA in plasma and serum by PCR is increasingly used to identify patients at risk for developing CMV disease and to monitor the efficacy of antiviral therapy. Although CMV DNA levels are generally interpreted as viral loads, the exact nature of the viral DNA in these specimens is unknown. We studied the state of CMV DNA in plasma and serum specimens obtained from three renal transplant recipients at peak viral DNA levels during primary CMV infection. For this purpose, DNA isolated from these specimens was fractionated by size, and CMV DNA levels in the resulting DNA fractions were measured by quantitative PCR targeted at large (578-bp) and small (134-bp) amplicons. These experiments showed that the molecular sizes of DNA fragments from which CMV DNA is amplified were small (<2,000 bp), indicating that CMV DNA in plasma and serum is highly fragmented. Furthermore, CMV DNA levels were consistently higher when targeted at the smaller amplicon, providing additional evidence for the fragmentation of viral DNA. In conclusion, the first results with three patients have shown that CMV DNA in plasma and serum is highly fragmented and does not necessarily reflect the amount of infectious virus. These observations have potential consequences for understanding CMV pathogenesis and interpreting CMV DNA levels in individual patient management.

Diagnostic testing in Epstein-Barr virus infection

Laboratory diagnosis of Epstein-Barr virus (EBV) infection is improving with the development of new technologies. Quantification of the virus by real-time polymerase chain reaction (PCR) and evaluation of EBV-specific T cells, especially by tetrameric human leukocyte antigens, are noteworthy candidates for monitoring procedures in clinical laboratories involved in the management of transplant recipients. Standardization of PCR is essential for improving the quality of these monitoring procedures.

Single-copy gene detection using branched DNA (bDNA) in situ hybridization

We have developed a branched DNA in situ hybridization (bDNA ISH) method for detection of human papillomavirus (HPV) DNA in whole cells. Using human cervical cancer cell lines with known copies of HPV DNA, we show that the bDNA ISH method is highly sensitive, detecting as few as one or two copies of HPV DNA per cell. By modifying sample pretreatment, viral mRNA or DNA sequences can be detected using the same set of oligonucleotide probes. In experiments performed on mixed populations of cells, the bDNA ISH method is highly specific and can distinguish cells with HPV-16 from cells with HPV-18 DNA. Furthermore, we demonstrate that the bDNA ISH method provides precise localization, yielding positive signals retained within the subcellular compartments in which the target nucleic acid sequences are localized. As an effective and convenient means for nucleic acid detection, the bDNA ISH method is applicable to the detection of cancers and infectious agents. (J Histochem Cytochem 49:603-611, 2001)

Diagnostic implications of human cytomegalovirus immediate early-1 and pp67 mRNA detection in whole-blood samples from liver transplant patients using nucleic acid sequence-based amplification

Nucleic acid sequence-based amplification (NASBA) was used for detection of the human cytomegalovirus (CMV) immediate early-1 (IE) and the late pp67 mRNA in 353 blood samples collected from 34 liver transplant patients. The diagnostic value of these assays was compared to that of the pp65 antigenemia assay. Overall, 95 and 42% of the antigenemia-positive samples were IE NASBA and pp67 NASBA positive, respectively. Although the results from pp67 NASBA and the antigenemia assay appeared to correspond poorly, a clear correlation was seen between pp67 NASBA-negative results and low numbers of pp65 antigen-positive cells. Twenty patients (59%) were treated with ganciclovir after the diagnosis of symptomatic CMV infection. Before initiation of the antiviral therapy, the antigenemia assay detected the onset of symptomatic infection in all patients, whereas 95 and 60% of these patients were IE NASBA and pp67 NASBA positive, respectively. Although the sensitivity of IE NASBA was very high, the positive predictive value (PPV) of this assay for the onset of a symptomatic infection was only 63%. The PPV of the antigenemia assay as well as pp67 NASBA was considerably higher (80 and 86%, respectively). Thus, the detection of IE mRNA using NASBA appears to be particularly useful as a marker for early initiation of antiviral therapy in patients at high risk for the development of a symptomatic infection. Also, IE NASBA was found to be more sensitive than the antigenemia assay for monitoring CMV infection during antiviral therapy. On the contrary, pp67 NASBA did not appear to have additional diagnostic value compared to the antigenemia assay.