False-positive results of plasma PCR for cytomegalovirus DNA due to delayed sample preparation

Causes of fever in Gabonese children: a cross-sectional hospital-based study

The causes of infections in pediatric populations differ between age groups and settings, particularly in the tropics. Such differences in epidemiology may lead to misdiagnosis and ineffective empirical treatment. Here, we investigated the current spectrum of pathogens causing febrile diseases leading to pediatric hospitalization in Lambaréné, Gabon. From August 2015 to March 2016, we conducted a prospective, cross-sectional, hospital-based study in a provincial hospital. Patients were children ≤ 15 years with fever ≥ 38 °C and required hospitalization. A total of 600 febrile patients were enrolled. Malaria was the main diagnosis found in 52% (311/600) patients. Blood cultures revealed septicemia in 3% (17/593), among them four cases of typhoid fever. The other causes of fever were heterogeneously distributed between both bacteria and viruses. Severe infections identified by Lambaréné Organ Dysfunction Score (LODS) were also most often caused by malaria, but children with danger signs did not have more coinfections than others. In 6% (35/600) of patients, no pathogen was isolated. In Gabon, malaria is still the major cause of fever in children, followed by a bacterial and viral disease. Guidelines for both diagnosis and management should be tailored to the spectrum of pathogens and resources available locally.

Epidemiology of Multiple Herpes Viremia in Previously Immunocompetent Patients With Septic Shock

Background

Systemic reactivations of herpesviruses may occur in intensive care unit (ICU) patients, even in those without prior immune deficiency. However, the clinical relevance of these events is uncertain.

Methods

In this study we selected patients admitted with septic shock and treated for more than 4 days from a prospectively enrolled cohort of consecutive adults in the mixed ICUs of 2 tertiary care hospitals in the Netherlands. We excluded patients who had received antiviral treatment in the week before ICU admission and those with known immunodeficiency. We studied viremia episodes with cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), and varicella zoster virus (VZV) by weekly polymerase chain reaction in plasma.

Results

Among 329 patients, we observed 399 viremia episodes in 223 (68%) patients. Viremia with CMV, EBV, HHV-6, HSV-1, HSV-2, and VZV was detected in 60 (18%), 157 (48%), 80 (24%), 87 (26%), 13 (4%), and 2 (0.6%) patients, respectively; 112 (34%) patients had multiple concurrent viremia events. Crude mortality in the ICU was 36% in this latter group compared to 19% in remaining patients (P < .01). After adjustment for potential confounders, time-dependent bias, and competing risks, only concurrent CMV and EBV reactivations remained independently associated with increased mortality (adjusted subdistribution hazard ratio, 3.17; 95% confidence interval, 1.41-7.13).

Conclusions

Herpesvirus reactivations were documented in 68% of septic shock patients without prior immunodeficiency and frequently occurred simultaneously. Concurrent reactivations could be independently associated with mortality.

Clinical Trials Registration

NCT01905033.

Human herpesvirus infections of the central nervous system: laboratory diagnosis based on DNA detection by nested PCR in plasma and cerebrospinal fluid samples

Infections of the central nervous systems (CNS) present a diagnostic problem for which an accurate laboratory diagnosis is essential. Invasive practices, such as cerebral biopsy, have been replaced by obtaining a polymerase chain reaction (PCR) diagnosis using cerebral spinal fluid (CSF) as a reference method. Tests on DNA extracted from plasma are noninvasive, thus avoiding all of the collateral effects and patient risks associated with CSF collection. This study aimed to determine whether plasma can replace CSF in nested PCR analysis for the detection of CNS human herpesvirus (HHV) diseases by analysing the proportion of patients whose CSF nested PCR results were positive for CNS HHV who also had the same organism identified by plasma nested PCR. In this study, CSF DNA was used as the "gold standard," and nested PCR was performed on both types of samples. Fifty-two patients with symptoms of nervous system infection were submitted to CSF and blood collection. For the eight HHV, one positive DNA result-in plasma and/or CSF nested PCR-was considered an active HHV infection, whereas the occurrence of two or more HHVs in the same sample was considered a coinfection. HHV infections were positively detected in 27/52 (51.9%) of the CSF and in 32/52 (61.5%) of the plasma, difference not significant, thus nested PCR can be performed on plasma instead of CSF. In conclusion, this findings suggest that plasma as a useful material for the diagnosis of cases where there is any difficulty to perform a CSF puncture.

Recent developments in human cytomegalovirus diagnosis

Since the early 1990s, great efforts have been made in the field of human cytomegalovirus (HCMV) diagnosis. Besides HCMV diagnosis in immunosuppressed patients (solid organ transplant recipients, hematopoietic stem cell transplant patients and AIDS patients), diagnosis in connection with congenital HCMV infection is of great interest. This review focuses on the development and clinical utility of serological assays, as well as on virological tests (molecular and nonmolecular assays). Interpretation of these tests is strongly dependent on the patient group (solid organ transplant recipients and hematopoietic stem cell transplant patients) and whether the tests are used for screening, risk stratification or diagnosis. Furthermore, a better understanding of HCMV infection has led to new approaches in HCMV diagnosis and monitoring. Thus, assays for viral resistance testing and assays for monitoring the HCMV-specific cellular immune response are increasingly important for the guidance of antiviral therapy.

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.

Comparative analysis of rodent tissue preservation methods and nucleic acid extraction techniques for virus screening purposes

The polymerase chain reaction (PCR) has become an essential method for the detection of viruses in tissue specimens. However, it is well known that the presence of PCR inhibitors in tissue samples may cause false-negative results. Hence the identification of PCR inhibitors and evaluation and optimization of nucleic acid extraction and preservation methods is of prime concern in virus discovery programs dealing with animal tissues. Accordingly, to monitor and remove inhibitors we have performed comparative analyses of two commonly used tissue storage methods and five RNA purification techniques using a variety of animal tissues, containing quantified levels of added MS2 bacteriophages as the indicator of inhibition. The results showed (i) no significant difference between the two methods of sample preservation, viz. direct storage at -80°C or 4°C in RNAlater, (ii) lung rodent tissues contained lower levels of inhibitor than liver, kidney and spleen, (iii) RNA extraction using the EZ1+PK RNA kit was the most effective procedure for removal of RT-PCR inhibitors.

Cytomegalovirus DNA stability in EDTA anti-coagulated whole blood and plasma samples

BACKGROUND

Cytomegalovirus (CMV) DNA viral load testing is routinely performed in centers that serve patients that are immunosuppressed from organ or hematopoietic stem cell transplantation. Clinical laboratories that offer this testing often face practical concerns about the storage of these specimens to ensure accurate measurement for patient care. The published studies that assess CMV DNA stability at 4°C have done so only up to 72 h.

OBJECTIVE

Our objective was to determine the stability of CMV DNA in whole blood and plasma for clinical viral load testing over a 14 day period.

STUDY DESIGN

Twenty-one plasma samples that were CMV-positive and twenty whole blood samples (including eleven CMV-negative whole blood samples spiked with CMV-positive plasma) were stored at 4°C and underwent extraction and amplification at 3 time points: Day 0, Day 7, and Day 14.

RESULTS

Log(10) values were calculated and t-test was performed on the values comparing Day 0 to Day 14 for plasma and whole blood. There was no statistically significant difference between Day 0 and Day 14 for both specimen types, including the CMV-negative whole blood specimens that were spiked with CMV-positive plasma.

CONCLUSIONS

CMV DNA in plasma and whole blood is stable for 14 days at a temperature of 4°C.

Active cytomegalovirus infection is common in mechanically ventilated medical intensive care unit patients

OBJECTIVE

To assess the incidence, risk factors, and outcome of active cytomegalovirus (CMV) infection in nonimmunosuppressed intensive care unit (ICU) patients.

DESIGN

Prospective epidemiologic study.

SETTING

A medical ICU in a university hospital.

PATIENTS

Two hundred forty-two nonimmunosuppressed ICU patients mechanically ventilated for >or=2 days.

INTERVENTIONS

Routine pp65 antigenemia and serology for CMV were performed at admission, and then weekly. Bronchoalveolar lavage viral cultures were done when pneumonia was suspected.

MEASUREMENTS AND MAIN RESULTS

Thirty-nine of the 242 ICU patients (16.1%, confidence interval 11.5% to 20.7%) developed an active CMV infection, as diagnosed by positive antigenemia (85%) and/or positive rapid viral culture in bronchoalveolar lavage (26%). Antiviral treatment was initiated in 21 (54%) patients. ICU mortality (54% vs. 37%, p = 0.082) and in-hospital mortality (59% vs. 41%, p = 0.058) were increased in patients with active CMV infection, as compared with those without active CMV infection. Active CMV infection and Simplified Acute Physiology Score II at admission were associated with ICU death on multivariate analysis. The patients with active CMV infection had longer mechanical ventilation and longer ICU stay and were significantly more prone to developing bacterial nosocomial infections (p < 0.001). Logistic regression analysis showed that prior admission to other wards (p = 0.043; odds ratio [OR], 2.49), blood transfusions (p = 0.04; OR, 3.31), enteral feeding (p = 0.005; OR, 3.00), recent corticosteroid use before ICU admission (p = 0.08; OR, 2.26), and age (p = 0.07; OR, 1.026) were associated with the occurrence of active CMV infection.

CONCLUSIONS

: Active CMV infection is common among previously healthy patients under mechanical ventilation in a medical ICU. Further studies are needed to evaluate the role of antiviral treatments to reduce both the incidence and the outcome impact of active CMV infection.

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.

Detection of HCMV DNA in placenta, amniotic fluid and fetuses of seropositive women by nested PCR

Human cytomegalovirus (HCMV) is the most common viral cause of intrauterine infection throughout the world. Its distribution patterns in different clinical samples are poorly understood. This study was performed to determine the frequency of CMV DNA positivity in maternal/fetus sera, placentas and amniotic fluid, together with maternal/fetus serology. Clinical specimens were obtained from 92 pregnant women who delivered by cesarean section. 98% of women and their neonates were HCMV IgG positive and 5.4% of these mothers were IgM positive, while no IgM was detected in neonates of IgM positive mothers. Among the IgG positive mothers, IgM was detected in 3.3% of their fetuses. 5.4% and 3.3% of maternal and fetal sera were HCMV DNA positive, respectively. The three neonates who were positive for HCMV DNA in sera were also positive for HCMV IgM and the PCR of their amnions was positive (p < 0.0001). 9.8% of placenta samples and 4.3% of amniotic fluid specimens were positive for HCMV DNA while among these placenta samples, two amnions were PCR positive (p = 0.046). Our results showed that there is not always a correlation between placenta and amnion infections. This may be due to reactivation of HCMV leading to placenta infection, as all affected placentas do not pass infection to fetuses and amniotic fluids. Detection of HCMV DNA in amnion and fetus plasma and the existence of fetus IgM against HCMV can also occur without clinical symptoms.

Analytic Validation of a Quantitative Real-time PCR Assay to Measure CMV Viral Load in Whole Blood

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in immunocompromised patients. We compared the CMV pp65 antigenemia test with a less labor intensive quantitative polymerase chain reaction (PCR) assay in 109 whole blood samples predominantly from transplant patients and patients with AIDS. DNA was amplified on an Applied Biosystems 7900 instrument using a TaqMan probe targeting the CMV polymerase gene and the APOB human control gene. The DNA assay was linear over a 6-log range from 8 to 800,000 CMV genomes per reaction; coefficient of variation was 20%. CMV DNA was undetectable in 20 blood samples from healthy donors whereas it was detected in 55 of 109 patient samples. Results were concordant in a nonlinear fashion with those of the antigenemia test in 90/109 (83%). Evaluation of the discrepancies suggested that either PCR or antigenemia assays could be falsely negative when virus levels were quite low. A point mutation interfered with probe binding in 1 sample. A second real-time PCR targeting the immediate early gene was even more likely to be false negative. In summary, CMV viral load measurement targeting the polymerase gene is nearly equivalent to the antigenemia assay for detecting and monitoring active CMV infection in whole blood samples.

Human herpesvirus-6 (HHV-6) DNA in plasma reflects the presence of infected blood cells rather than circulating viral particles

BACKGROUND

The presence of HHV-6 DNA in plasma or serum is considered a good marker of active infection. However, it is ignored whether this DNA corresponds to virus particles produced by lymphoid tissue infection or virus-free DNA released from infected circulating blood cells.

OBJECTIVES

To investigate whether HHV-6 DNA in whole plasma is nonencapsidated and its amount is correlated to cellular and human herpesvirus-7 (HHV-7) DNA loads in plasma subfractions as well as in corresponding peripheral blood mononuclear cells (PBMCs).

STUDY DESIGN

Whole plasma samples from immunocompromised patients were submitted to a DNase-resistance test. Plasma samples from a second group of patients were split up into three subfractions: P1 (pellet of clarification), P2 (pellet of ultracentrifugation), and S (supernatant of ultracentrifugation). HHV-6, HHV-7, and cellular DNA loads were determined in each fraction and PBMCs using specific real-time PCR.

RESULTS

Among 14 whole plasma samples, the majority of HHV-6 DNA detected was unprotected against DNase, i.e. nonencapsidated. The study of 35 other plasma samples revealed that cellular DNA was present in all subfractions from all samples whereas HHV-6 DNA was detected in 13 P1, 12 P2, 10 S fractions, and HHV-7 DNA in only one P1 fraction. Accordingly, median HHV-6 DNA load was significantly higher in P1 than in P2 and S fractions. The detection of HHV-6 DNA in plasma subfractions was statistically associated with a higher HHV-6 viral load in PBMCs (p<or=0.0003).

CONCLUSIONS

Taken together, these data tend to favour the hypothesis of a release of HHV-6 and cellular DNA into plasma following the lysis of infected PBMCs. HHV-6 DNA in plasma does not necessarily reflect the amount of virus produced by the active infection of distant lymphoid tissue and organs.

Electrical detection of viral DNA using ultramicroelectrode arrays

A fully electrical array for voltammetric detection of redox molecules produced by enzyme-labeled affinity binding complexes is shown. The electronic detection is based on ultramicroelectrode arrays manufactured in silicon technology. The 200-microm circular array positions have 800-nm-wide interdigitated gold ultramicroelectrodes embedded in silicon dioxide. Immobilization of oligonucleotide capture probes onto the gold electrodes surfaces is accomplished via thiol-gold self-assembling. Spatial separation of probes at different array positions is controlled by polymeric rings around each array position. The affinity bound complexes are labeled with alkaline phosphatase, which converts the electrochemically inactive substrate 4-aminophenyl phosphate into the active 4-hydroxyaniline (HA). The nanoscaled electrodes are used to perform a sensitive detection of enzyme activity by signal enhancing redox recycling of HA resulting in local and position-specific current signals. Multiplexing and serial readout is realized using a CMOS ASIC module and a computer-controlled multichannel potentiostat. The principle of the silicon-based electrical biochip array is shown for different experimental setups and for the detection of virus DNA in real unpurified multiplex PCR samples. The fast and quantitative electronic multicomponent analysis for all kinds of affinity assays is robust and particle tolerant.

Cytomegalovirus quantitation by real-time PCR is unaffected by delayed separation of plasma from whole blood

A previous study suggested that delayed sample preparation can cause a false-positive plasma cytomegalovirus (CMV) PCR. We evaluated 78 samples submitted for CMV testing, and we report that a 24-h delay in plasma separation did not affect viral quantitation by real-time PCR. Laboratories should evaluate specimen handling requirements for their own PCR technology.

Molecular diagnosis of viral infections in renal transplant recipients

PURPOSE OF REVIEW

To discuss biological and methodological aspects of virus infection monitoring in the renal transplant setting.

RECENT FINDINGS

New insights on the molecular pathogenesis of acute and persistent virus infections and rapid developments in real-time monitoring techniques are changing the current diagnostic routine. Accurate risk-assessment prior to transplantation and quantitative monitoring of parameters that reflect virus activity in the post-transplant period, including genome load fluctuations and aberrant viral mRNA or protein expression, provide early signs of undesired viral behaviour and allow pre-emptive therapeutic intervention. As opposed to prophylactic administration of antiviral drugs, a pre-emptive approach is more selective and will allow for antiviral immune responses to build, which may have a long-term beneficial effect. In addition, these virus-monitoring techniques allow for on-line assessment of therapeutic efficacy and rapid identification of emerging resistant strains. The combination of virus-monitoring techniques with rapid assessment of host immune responses using FACS and ELISPOT techniques, will improve overall patient management and long-term survival.

SUMMARY

Viral infections continue to be a significant complication in the transplant setting. Diagnostic monitoring allows timely and accurate therapeutic intervention. Knowledge of pathogenic mechanisms leading to disease is important for clinical decision making as well as for the selection of appropriate molecular parameters discriminating normal and disease-related activity of human pathogenic viruses. The increasing availability of effective antiviral drugs permits pre-emptive intervention that strongly depends on accurate viral monitoring procedures.

Multiplex, quantitative, real-time PCR assay for cytomegalovirus and human DNA

We created a multiplex, quantitative, real-time PCR assay that amplifies cytomegalovirus (CMV) and human DNA in the same reaction tube, allowing for a viral load determination that is normalized to measured human DNA. The assay targets a conserved region of the CMV DNA polymerase gene that is not affected by known drug resistance mutations. All 36 strains of CMV detected by culture or qualitative PCR in a population of lung transplant recipients were detected. The assay detected 1 to 10 copies of CMV plasmid DNA. The analytic sensitivity was not affected by the presence of DNA from 10(6) human cells but was reduced approximately 10-fold by alkaline lysates of leukocyte preparations. CMV quantitation was linear over a range of 10(1) to 10(6) copies. The intraassay and interassay coefficients of variation were 29 and 40%. Human DNA was regularly detected in patient plasma samples, and the amount was increased by storage of blood at room temperature before plasma separation and by plasma separation techniques that allowed leukocyte contamination. Applied to whole blood, the assay provides a measurement of CMV DNA in relation to cellular content without a need for cell counting procedures. Applied to plasma, the assay can reveal artifactual increases in plasma CMV levels resulting from leukocyte contamination. Further study of the utility of this assay to monitor patient populations at risk for CMV disease is warranted.

Role of Epstein-Barr virus DNA load monitoring in prevention and early detection of post-transplant lymphoproliferative disease

Posttransplant lymphoproliferative disease (PTLD) is a severe and life-threatening complication after stem cell or solid-organ transplantation, virtually always associated with presence of Epstein-Barr virus (EBV) in the proliferating cells. PTLD is probably caused by the iatrogenically impaired T-cell response allowing outgrowth of EBV-positive B-cells. Quantitative EBV DNA load monitoring is a minimally invasive technique increasingly recognized as a valuable tool in posttransplant patient management. In this review, we focus on the clinical utility of EBV DNA load monitoring in the peripheral blood of transplant recipients using PCR and we discuss the currently most-widely used techniques and their value and limitations in predicting and diagnosing PTLD. Options for EBV DNA load-guided pre-emptive therapy and application of monitoring EBV DNA load dynamics in the prediction of clinical response after therapy are described. Origins of elevated EBV DNA loads in immunosuppressed patients and recent insights in the EBV life cycle in the immuncompromised host are discussed. Finally, a standardization of methodology, clinical specimen type, and cut-off values is proposed. This is essential for comparisons between different institutes and more adequate patient management.

Fulminant disseminated Varicella Zoster virus infection without skin involvement

BACKGROUND

Varicella Zoster virus (VZV) infection is potentially very serious in bone marrow transplant recipients, and may manifest as a disseminated visceral infection. This condition is generally accompanied by a vesicular rash.

OBJECTIVES

We review here a case of fulminant fatal disseminated VZV infection, not accompanied by skin involvement, and the laboratory approaches currently available to diagnose this disease.

STUDY DESIGN

Post mortem tissue samples were subjected to histopathological examination, and tested for herpesviruses by electron microscopy and PCR.

RESULTS

Intranuclear inclusions were noted by histological examination in the lungs, liver, kidneys and bone marrow. Particles with a herpesvirus morphology were visualized in liver tissue. VZV DNA was detected in liver and bone marrow by PCR followed by sequencing of the amplicons. Viremia was documented by retrospective testing of the serum by PCR.

CONCLUSIONS

A disseminated VZV infection which proved rapidly fatal was demonstrated in a case without skin manifestations. This rare presentation of VZV infection is potentially underdiagnosed. Testing for VZV viremia by PCR can at the very least suggest the diagnosis although whether plasma-associated viremia is truly pathognomonic of visceral disseminated infection remains to be established.