Analytical and clinical performance of a new molecular assay for Epstein-Barr virus DNA quantitation

The IPTA Nashville Consensus Conference on Post-Transplant lymphoproliferative disorders after solid organ transplantation in children: III - Consensus guidelines for Epstein-Barr virus load and other biomarker monitoring

The International Pediatric Transplant Association convened an expert consensus conference to assess current evidence and develop recommendations for various aspects of care relating to post-transplant lymphoproliferative disorders after solid organ transplantation in children. In this report from the Viral Load and Biomarker Monitoring Working Group, we reviewed the existing literature regarding the role of Epstein-Barr viral load and other biomarkers in peripheral blood for predicting the development of PTLD, for PTLD diagnosis, and for monitoring of response to treatment. Key recommendations from the group highlighted the strong recommendation for use of the term EBV DNAemia instead of "viremia" to describe EBV DNA levels in peripheral blood as well as concerns with comparison of EBV DNAemia measurement results performed at different institutions even when tests are calibrated using the WHO international standard. The working group concluded that either whole blood or plasma could be used as matrices for EBV DNA measurement; optimal specimen type may be clinical context dependent. Whole blood testing has some advantages for surveillance to inform pre-emptive interventions while plasma testing may be preferred in the setting of clinical symptoms and treatment monitoring. However, EBV DNAemia testing alone was not recommended for PTLD diagnosis. Quantitative EBV DNAemia surveillance to identify patients at risk for PTLD and to inform pre-emptive interventions in patients who are EBV seronegative pre-transplant was recommended. In contrast, with the exception of intestinal transplant recipients or those with recent primary EBV infection prior to SOT, surveillance was not recommended in pediatric SOT recipients EBV seropositive pre-transplant. Implications of viral load kinetic parameters including peak load and viral set point on pre-emptive PTLD prevention monitoring algorithms were discussed. Use of additional markers, including measurements of EBV specific cell mediated immunity was discussed but not recommended though the importance of obtaining additional data from prospective multicenter studies was highlighted as a key research priority.

Development of a Rapid Epstein-Barr Virus Detection System Based on Recombinase Polymerase Amplification and a Lateral Flow Assay

The quality of cellular products used in biological research can directly impact the ability to obtain accurate results. Epstein-Barr virus (EBV) is a latent virus that spreads extensively worldwide, and cell lines used in experiments may carry EBV and pose an infection risk. The presence of EBV in a single cell line can contaminate other cell lines used in the same laboratory, affecting experimental results. We developed three EBV detection systems: (1) a polymerase chain reaction (PCR)-based detection system, (2) a recombinase polymerase amplification (RPA)-based detection system, and (3) a combined RPA-lateral flow assay (LFA) detection system. The minimum EBV detection limits were 1 × 103 copy numbers for the RPA-based and RPA-LFA systems and 1 × 104 copy numbers for the PCR-based system. Both the PCR and RPA detection systems were applied to 192 cell lines, and the results were consistent with those obtained by the EBV assay methods specified in the pharmaceutical industry standards of the People's Republic of China. A total of 10 EBV-positive cell lines were identified. The combined RPA-LFA system is simple to operate, allowing for rapid result visualization. This system can be implemented in laboratories and cell banks as part of a daily quality control strategy to ensure cell quality and experimental safety and may represent a potential new technique for the rapid detection of EBV in clinical samples.

Comparison of four commercial EBV DNA quantitative tests to a new test at an early stage of development

BACKGROUND

Regular screening for Epstein-Barr virus (EBV) DNA using quantitative RT-PCR is recommended for early intervention in at-risk patients. Harmonization of quantitative RT-PCR assays is critical to avoid misinterpretation of results. Here, we compare quantitative results of the cobas® EBV assay to four commercial RT-qPCR assays.

METHODS

The cobas EBV, EBV R-Gene, artus EBV RG PCR, RealStar EBV PCR kit 2.0 and Abbott EBV RealTime assays were compared for analytic performance using a 10-fold dilution series of EBV reference material, normalized to the WHO standard. For clinical performance, their quantitative results were compared using anonymized, leftover EBV-DNA-positive EDTA plasma samples.

RESULTS

For analytic accuracy, the cobas EBV deviated -0.0097 log₁₀ from target values. The other tests showed deviations between 0.0037 and -0.12 log₁₀. For clinical performance, accuracy and linearity of cobas EBV data from both study sites were excellent. Bland-Altman bias and Deming regression analyses showed statistical correlation for cobas EBV to both EBV R-Gene and Abbott RealTime assays but an offset of cobas EBV to artus EBV RG PCR and RealStar EBV PCR kit 2.0.

CONCLUSION

The cobas EBV showed the closest correlation to the reference material, followed closely by EBV R-Gene and Abbott EBV RealTime. Values obtained are stated in IU/mL, facilitating comparison across testing sites and potentially improving utilization of guidelines for diagnosis, monitoring, and treatment of patients.

Detection of low-load Epstein-Barr virus in blood samples by enriched recombinase aided amplification assay

Epstein-Barr virus (EBV), a common human γ-herpesvirus, infects more than 90% of adults worldwide. The purpose of this study was to establish a novel EBV detection method by combining the recombinase aided amplification (RAA) assay with an initial enrichment step that utilizes magnetic beads coated with a recombinant human mannan-binding lectin (rhMBL, M1 protein). An M1 protein–protein A magnetic bead complex (M1 beads) was prepared and used to achieve separation and enrichment of EBV from blood. After nucleic acid extraction, DNA was amplified by RAA. Using 388 whole blood samples and 1 serum sample, we explored the specificity, sensitivity and applicability of the newly developed detection method and compared it with commercial quantitative real-time polymerase chain reaction (qPCR) following M1 bead enrichment, traditional qPCR and traditional RAA. After enrichment, the positivity rate of EBV was increased from 15.94% to 17.74% by RAA (P < 0.05) and from 7.20% to 15.17% by qPCR (P < 0.05). The viral loads after enrichment were increased by 1.13 to 23.19-fold (P < 0.05). Our data demonstrates that an RAA assay incorporating M1 bead enrichment is a promising tool for detecting low EBV viral loads in blood samples that will facilitate an early response to EBV infection.

The RAA with an enrichment step that utilizes magnetic beads coated with M1 protein.

A very effective method for detecting low-load virus in blood samples.

The first report describing virus detection using this method.

Automated quantification of Epstein-Barr virus in whole blood for post-transplant lymphoproliferative disorders monitoring

Background

Standardized and sensitive assays for Epstein Barr Virus (EBV) are needed to define universal cutoff for treatment initiation in allogeneic hematopoietic stem cells transplant recipients. In a context of accreditation and the availability of EBV international standard, we evaluated the Abbott RealTime EBV (RT) assay for EBV quantification in whole blood.

Methods

The RT assay was compared on 282 prospective clinical samples with the Artus EBV PCR Kit V1 assay (V1) and we analyzed the kinetics of EBV load in 11 patients receiving rituximab treatment.

Results

The estimated limit of detection was 88 IU/mL. The assay was linear (r² = 0.9974) in the range of all samples tested (100 to 1,000,000 IU/mL). Intra-assay coefficients of variation (CV) ranged between 0.35 and 1.35%, and inter-assay CV between 3.40 and 4.5%. On samples above the limit of quantification, the two assays were strongly correlated. EBV RT values were on average 0.30 log₁₀ IU/mL lower than those measured with the V1 assay. In patients treated with rituximab, the RT assay remained positive in 5 patients at the time it dropped below undetectable levels with the V1 assay.

Conclusions

In conclusion, the RT assay is a reliable assay for EBV load in whole blood. Its sensitivity will enable to estimate the kinetics of EBV load and the impact of treatments to control EBV reactivations.

Evaluation of the new Abbott Real-Time EBV assay: fully automated quantification of EBV in whole blood by targeting BLLF1

The accurate measurement of the Epstein-Barr virus (EBV) DNA level in the blood is required for managing EBV-associated diseases. A new commercial Abbott Real-Time EBV assay, which targets the BLLF1 gene, was evaluated on 120 clinical whole blood samples and the Qnostics EBV analytical panel. The limit of detection of the assay was 48.9 IU/mL (95% confidence interval, 48.1-49.8 IU/mL). The assay was linear from 2 to 5 log₁₀ IU/mL (R² = 0.997). The within-run coefficients of variation (CVs) ranged from 1.68% to 4.75% and the between-run CVs ranged from 1.73% to 12.83% for samples with high, medium, and low viral loads. EBV DNA loads measured by Abbott EBV assay strongly correlated with the results quantified by another commercial Nanogen EBV Real-Time Alert Q-PCR assay (r = 0.879, P < 0.0001). The fully automated Abbott Real-Time EBV assay targeting BLLF1 reduced both hands-on time and turnaround time and demonstrated a reliable performance for EBV DNA quantification in whole blood.

Automated quantification of Epstein-Barr Virus in whole blood of hematopoietic stem cell transplant patients using the Abbott m2000 system

BACKGROUND

Accurate quantification of Epstein-Barr virus (EBV) load in blood is essential for the management of post-transplant lymphoproliferative disorders. The automation of DNA extraction and amplification may improve accuracy and reproducibility. We evaluated the EBV PCR Kit V1 with fully automated DNA extraction and amplification on the m2000 system (Abbott assay).

METHODOLOGY

Conversion factor between copies and international units (IU), lower limit of quantification, imprecision and linearity were determined in a whole blood (WB) matrix. Results from 339 clinical WB specimens were compared with a home-brew real-time PCR assay used in our laboratory (in-house assay).

RESULTS

The conversion factor between copies and IU was 3.22 copies/IU. The lower limit of quantification (LLQ) was 1000 copies/mL. Intra- and inter-assay coefficients of variation were 3.1% and 7.9% respectively for samples with EBV load higher than the LLQ. The comparison between Abbott assay and in-house assay showed a good concordance (kappa = 0.77). Loads were higher with the Abbott assay (mean difference = 0.62 log10 copies/mL).

SIGNIFICANCE

The EBV PCR Kit V1 assay on the m2000 system provides a reliable and easy-to-use method for quantification of EBV DNA in WB.