Armored long RNA controls or standards for branched DNA assay for detection of human immunodeficiency virus type 1

Virus-like particles derived from bacteriophage MS2 as antigen scaffolds and RNA protective shells

The versatile potential of bacteriophage MS2-derived virus-like particles (VLPs) in medical biotechnology has been extensively studied during the last 30 years. Since the first reports showing that MS2 VLPs can be produced at high yield and relatively easily engineered, numerous applications have been proposed. Particular effort has been spent in developing MS2 VLPs as protective capsules and delivery platforms for diverse molecules, such as chemical compounds, proteins and nucleic acids. Among these, two are particularly noteworthy: as scaffolds displaying heterologous epitopes for vaccine development and as capsids for encapsulation of foreign RNA. In this review, we summarize the progress in developing MS2 VLPs for these two areas.

Development and evaluation of an external quality control and internal quality control containing real-time RT-PCR assay for the detection of o'nyong-nyong virus

O'nyong-nyong fever is a mosquito-borne tropical viral disease while few molecular diagnostic tools have been established for its surveillance until now. In the current study, a single-step, dual-color real-time reverse transcription polymerase chain reaction (RT-PCR) assay which contained both external quality control (EQC) and internal quality control (IQC) prepared by armored RNA technique was developed and evaluated for the detection of o'nyong-nyong virus (ONNV). Results showed that the assay was established successfully without cross-reaction with genetically related or symptom-alike diseases, which showed high specificity of the assay. The coefficient of variation of the assay was 0.97%, far less than 5%, indicating good repeatability of the assay. The lower limit of detection of the assay could reach as low as 100 copies of genome equivalent. During evaluation, the assay could correctly detect ONNV from spiked human serum samples and Anopheles species mosquito samples, while no ONNV positive was observed either from serum samples of patients with acute febrile illness or from local Anopheles species mosquitoes, suggesting no ONNV had been transmitted locally. In conclusion, the assay could potentially provide a valuable platform for ONNV molecular detection, which may improve the preparedness for future o'nyong-nyong fever outbreaks.

Assessing the comparability of cycle threshold values derived from five external quality assessment rounds for omicron nucleic acid testing

BACKGROUND

A variety of open-system real-time reverse transcriptase polymerase chain reaction (RT-PCR) assays for several acute respiratory syndrome coronavirus 2 are currently in use. This study aimed to ensure the quality of omicron nucleic acid testing and to assess the comparability of cycle threshold (Ct) values derived from RT-PCR.

METHODS

Five external quality assessment (EQA) rounds using the omicron virus-like particles were organized between February 2022 and June 2022.

RESULTS

A total of 1401 qualitative EQA reports have been collected. The overall positive percentage agreement was 99.72%, the negative percentage agreement was 99.75%, and the percent agreement was 99.73%. This study observed a significant variance in Ct values derived from different test systems. There was a wide heterogeneity in PCR efficiency among different RT-PCR kits and inter-laboratories.

CONCLUSION

There was strong concordance among laboratories performing qualitative omicron nucleic acid testing. Ct values from qualitative RT-PCR tests should not be used for clinical or epidemiological decision-making to avoid the potential for misinterpretation of the results.

Current status and progress of the development of prostate cancer vaccines

At present, common treatments of prostate cancer mainly include surgery, radiotherapy, chemotherapy and hormone therapy. However, patients have high recurrence rate after treatment, and are prone to castration-resistant prostate cancer. Tumor vaccine is based on tumor specific antigen (TSA) and tumor associated antigen (TAA) to activate specific immune response of the body to cancer cells. With continuous maturity of tumor vaccine technology, different forms of prostate cancer vaccines have been developed, such as cellular vaccines, extracellular-based anti-tumor vaccines, polypeptide vaccines, and nucleic acid vaccines. In this review, we summarize current status and progress in the development of prostate cancer vaccines.

Simple Low-Cost Production of DNA MS2 Virus-Like Particles As Molecular Diagnostic Controls

Suitable controls are integral for the validation and continued quality assurance of diagnostic workflows. Plasmids, DNA, or in vitro transcribed RNA are often used to validate novel diagnostic workflows, however, they are poorly representative of clinical samples. RNA phage virus-like particles (VLPs) packaged with exogenous RNA have been used in clinical diagnostics as workflow controls, serving as surrogates for infectious viral particles. Comparable controls for DNA viruses are more challenging to produce, with analogous DNA phages being infectious and packaging of DNA within RNA phages requiring complex purification procedures and expensive chemical linkers. We present a simple and inexpensive method to produce Emesvirus zinderi (MS2) VLPs, packaged with DNA, that makes use of affinity chromatography for purification and enzymatic production of exogenous DNA suitable for packaging. The produced VLPs were packaged with hepatitis B virus DNA and were then quantified using droplet digital PCR and calibrated against the WHO international standard using a commercial assay in an accredited clinical laboratory.

Programmable polymorphism of a virus-like particle

Virus-like particles (VLPs) have significant potential as artificial vaccines and drug delivery systems. The ability to control their size has wide ranging utility but achieving such controlled polymorphism using a single protein subunit is challenging as it requires altering VLP geometry. Here we achieve size control of MS2 bacteriophage VLPs via insertion of amino acid sequences in an external loop to shift morphology to significantly larger forms. The resulting VLP size and geometry is controlled by altering the length and type of the insert. Cryo electron microscopy structures of the new VLPs, in combination with a kinetic model of their assembly, show that the abundance of wild type (T = 3), T = 4, D3 and D5 symmetrical VLPs can be biased in this way. We propose a mechanism whereby the insert leads to a change in the dynamic behavior of the capsid protein dimer, affecting the interconversion between the symmetric and asymmetric conformers and thus determining VLP size and morphology.

Optimizing the synthesis and purification of MS2 virus like particles

Introducing bacteriophage MS2 virus-like particles (VLPs) as gene and drug delivery tools increases the demand for optimizing their production and purification procedure. PEG precipitation method is used efficiently to purify VLPs, while the effects of pH and different electrolytes on the stability, size, and homogeneity of purified MS2 VLPs, and the encapsulated RNA sequences remained to be elucidated. In this regard, a vector, capable of producing VLP with an shRNA packed inside was prepared. The resulting VLPs in different buffers/solutions were assessed for their size, polydispersity index, and ability to protect the enclosed shRNA. We report that among Tris, HEPES, and PBS, with or without NaNO3, and also NaNO3 alone in different pH and ionic concentrations, the 100 mM NaNO3-Tris buffer with pH:8 can be used as a new and optimal MS2 VLP production buffer, capable of inhibiting the VLPs aggregation. These VLPs show a size range of 27-30 nm and suitable homogeneity with minimum 12-month stability at 4 °C. Moreover, the resulting MS2 VLPs were highly efficient and stable for at least 48 h in conditions similar to in vivo. These features of MS2 VLPs produced in the newly introduced buffer make them an appropriate candidate for therapeutic agents' delivery.

External Quality Assessment for Molecular Detection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Clinical Laboratories

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses a huge threat to public health. Viral nucleic acid testing is the diagnostic gold standard and can play an important role in the prevention and control of this infection. In this study, bacteriophage MS2 virus-like particles encapsulating specific RNA sequences of SARS-CoV-2 and other coronaviruses were prepared by genetic engineering. The assessment panel, consisting of four positive samples with concentrations of 2.8, 3.5, 4.2, and 4.9 log₁₀ copies/mL and five negative samples with other human coronaviruses, was prepared and distributed to evaluate the accuracy of routine viral RNA detection. Results of 931 panels from 844 laboratories were collected. The overall percentage agreement, positive percentage agreement (PPA), and negative percentage agreement, defined as the percentage of agreement between the correct results and total results submitted for all, positive, and negative samples were 96.8% (8109/8379), 93.9% (3497/3724), and 99.1% (4612/4655), respectively. For samples with concentrations of 4.9 and 4.2 log₁₀ copies/mL, the PPAs were >95%. However, for 3.5 and 2.8 log₁₀ copies/mL, the PPAs were 94.6% (881/931) and 84.9% (790/931), respectively. For all negative samples, the negative percentage agreement values were >95%. Thus, most laboratories can reliably detect SARS-CoV-2. However, further improvement and optimization are required to ensure the accuracy of detection in panel members with lower concentrations of viral RNA.

Standardization of BCR-ABL1 quantification on the international scale in China using locally developed secondary reference panels

For patients with chronic myeloid leukemia, reverse transcription quantitative polymerase chain reaction is widely used in laboratories to quantify BCR-ABL1 fusion gene transcripts for disease management. Many efforts have been made to standardize the BCR-ABL1 testing assay, including the primary and secondary reference reagents, but the secondary standards have not been developed and used in the standardization program in China. With the use of armored RNA technology, armored RNA of BCR-ABL1 and control genes was manufactured to prepare the secondary reference material anchored to the World Health Organization primary reference calibrators for standardization of BCR-ABL1 testing assays. The secondary reference was sent to 30 laboratories in China for validation. Data from an external quality assessment after the standardization process were collected and analyzed as well. The assigned %BCR-ABL1/ABL1^IS values of the four levels of the secondary material panels were 0.0118, 0.1345, 1.3808, and 19.4266, respectively. In validation trials, 70.0% (21/30) of laboratories obtained valid conversion factors for the BCR-ABL1 assay. All valid conversion factors from 11 international scale laboratories were equivalent to their respective previous values. External quality assessment data indicated that the accuracy and precision between laboratories were improved. Moreover, the quantity of the panels is abundant to be used as quality control samples for monitoring the shift of data. In this study, we established a secondary genetic reference panel for BCR-ABL1 quantification. This study will play a role in facilitating the worldwide dissemination of the international scale, especially in promoting the standardization of molecular monitoring in China.

Development and Evaluation of a Novel Armored RNA Technology Using Bacteriophage Qβ

Foodborne viruses are a global threat to food safety. Real-time reverse transcription polymerase chain reaction (RT-PCR) is the most commonly used method to detect viral RNA in food. Armored RNA (AR) prepared using the MS2 phage system is a successful positive control for detecting foodborne viruses and is an important quality control process when using real-time RT-PCR. In this study, we report a novel technology for preparing AR using bacteriophage Qβ and compare its stability with AR prepared using the MS2 phage system for packaging norovirus detection target RNA. AR could be successfully and efficiently produced using the developed bacteriophage Qβ system. Two types of AR-AR-QNoV prepared using the Qβ system and AR-MNoV prepared using the MS2 system-were stored at different temperatures for different durations. After incubating at - 20 °C for 360 days, the copy numbers of AR-QNoV and AR-MNoV decreased by 8.9% and 35.9%, respectively. After incubating at 4 °C for 60 days, the copy numbers of AR-QNoV and AR-MNoV decreased by 12.0% and 38.9%, respectively. After incubating at 45 °C, the copy numbers of AR-QNoV decreased by 71.8% after 5 days, whereas those of AR-MNoV decreased by 92.9% after only 4 days. After 5 days, AR-MNoV could not be detected using real-time RT-PCR. There was a significant difference in copy numbers decrease rate between AR-QNoV and AR-MNoV at three different temperatures (P < 0.05 ). Therefore, AR prepared using the new bacteriophage Qβ system is more stable than the traditional AR, making the developed strategy a good candidate for AR preparation and quality control.

Bacteriophage MS2 displays unreported capsid variability assembling T = 4 and mixed capsids

Bacteriophage MS2 is a positive-sense, single-stranded RNA virus encapsulated in an asymmetric T = 3 pseudo-icosahedral capsid. It infects Escherichia coli through the F-pilus, in which it binds through a maturation protein incorporated into its capsid. Cryogenic electron microscopy has previously shown that its genome is highly ordered within virions, and that it regulates the assembly process of the capsid. In this study, we have assembled recombinant MS2 capsids with non-genomic RNA containing the capsid incorporation sequence, and investigated the structures formed, revealing that T = 3, T = 4 and mixed capsids between these two triangulation numbers are generated, and resolving structures of T = 3 and T = 4 capsids to 4 Å and 6 Å respectively. We conclude that the basic MS2 capsid can form a mix of T = 3 and T = 4 structures, supporting a role for the ordered genome in favouring the formation of functional T = 3 virions.

Clinician-friendly reports of molecular measurable residual disease monitoring in acute promyelocytic leukemia

Molecular measurable residual disease (MRD) monitoring based on real-time quantitative reverse transcription PCR (RT-qPCR) plays an important role in acute promyelocytic leukemia (APL) management, but the performance status of clinical reports is unknown. This study focuses on the specific elements in molecular MRD monitoring report and their impact on clinical decision-making. The participating laboratories were asked to submit real and formal clinical reports for mock samples panel with APL clinical case. The MRD-specific elements were analyzed and summarized. The significance of longitudinal MRD monitoring curve and the missing MRD-specific elements for clinical decision-making were assessed. MRD-specific elements were significantly missing in clinical reports. The element "testing results" existed great inconsistencies in the written form of testing items and data. The longitudinal MRD monitoring curve of false-negative or false-positive MRD result was obviously different from all-correct. It not only identified MRD time point of tissue sampling relative to treatment and ensured the reliability of the negative MRD results, but also gave MRD diagnosis, clinical interpretation, and further recommendation. Clinician-friendly reports with MRD-specific elements can better serve clinical practice. The correctly intuitive results and clinically important MRD-specific elements can provide a good description of the reliability and clinical significance of MRD results.

External quality assessment for PML-RARα detection in acute promyelocytic leukemia: Findings and summary

BACKGROUND

The confirmation of clinical diagnosis, molecular remission, and sequential minimal residual disease monitoring required PML-RARα detection in acute promyelocytic leukemia (APL). The current status of PML-RARα detection in various laboratories remains unknown.

METHODS

In 2018, external quality assessment (EQA) for PML-RARα detection was carried out in China. Three EQA sample panels for PML-RARα isoform L/S/V were prepared by different mock leukocyte samples. The performances of PML-RARα detection, including admission screening, and qualitative and quantitative detection by real-time quantitative reverse transcription PCR (RT-qPCR), were assessed based on APL simulated clinical case.

RESULTS

The mock leukocyte samples met the requirements of a clinically qualified sample for PML-RARα EQA panel. Among the laboratories, 13/50 (26.0%) were "competent," 21/50 (42%) classified as "acceptable," and 16/50 (32.0%) classified as "improvable." One (1/50, 2.0%) laboratory reported one screening mistake. Twenty-six (26/50, 52.0%) laboratories reported 29 false-positive and 19 false-negative results. Twenty-three (23/50, 46.0%) laboratories reported 42 quantitative incorrect results.

CONCLUSION

Significant differences were not found in PML-RARα detection performance among laboratories that used different extraction methods. The performances of qualitative and quantitative RT-qPCR detection were worse accurate for PML-RARα isoform V. Quantitative variation was higher for low-level samples. Further continuous external assessment and education are needed in the management of PML-RARα detection.

External quality assessment of p210 BCR-ABL1 transcript quantification by RT-qPCR: Findings and recommendations

INTRODUCTION

External quality assessment (EQA) is an essential tool for quality assurance of analytical testing processes of p210 BCR-ABL1 transcripts by RT-qPCR. As an EQA provider, the National Center for Clinical Laboratories organized an EQA scheme of p210 BCR-ABL1 testing in China for the first time to identify existing problems and ensure the reliability of p210 BCR-ABL1 testing.

METHODS

Using armored RNA technology, we first constructed pACYC-MS2-p210 and CG recombinant plasmids and expressed p210 and CG armored RNAs, with packaging segments of p210 BCR-ABL1 fusion gene (FG) and four common control gene (CG) transcripts. Using these armored RNAs, we prepared lyophilized p210 quality control (QC) sample panels and evaluated detection performance of participating laboratories in China.

RESULTS

Of the 66 participating laboratories, great variation was found with coefficient of variation (CV%) of raw p210 BCR-ABL1 results basically ranging from 60.0% to 100.0%. In 24 International Scale (IS) laboratories, the CV% of results decreased from 82.4% to 61.6%, and the percentage of laboratories within 2-, 3-, and 5-fold of the median values increased from 78.2%, 87.0%, and 92.1% to 80.1%, 89.4%, and 97.2%, respectively, after conversion with a laboratory-specific conversion factor (CF); however, poorly converted results were also observed in laboratories resulting from changed components of RT-qPCR procedures. False-negative and false-positive results were also found in the EQA.

CONCLUSIONS

Various problems were found for p210 BCR-ABL1 detection in the EQA. By solving the existing problems, the performance of p210 BCR-ABL1 detection can be improved, ensuring robust laboratory diagnostic capacities in China.

Development and evaluation of armored RNA-based standards for quantification of BCR-ABL1p210/p190 fusion gene transcripts

BACKGROUND

Standards play an important role in detection of the BCR-ABL1 fusion gene (FG) transcript. However, the standards widely used in laboratories are mainly based on plasmids or cDNA, which cannot accurately reflect the process of RNA extraction and cDNA synthesis. Therefore, we aimed to develop armored RNA-based standards for p210 and p190 BCR-ABL1FG transcripts' quantification.

METHODS

Using overlapping polymerase chain reaction (PCR) technology, we first linked a segment of the p210 or p190 BCR-ABL1FG transcript with four control genes (CGs; ABL1, BCR, GUSB, and B2M) to form p210FG-CG and p190FG-CG. Subsequently, using armored RNA technology, we prepared p210FG-CG- and p190FG-CG-armored RNAs and the p210FG-CG and p190FG-CG standards, the values of which were assigned by digital PCR (dPCR).

RESULTS

The p210FG-CG and p190FG-CG standards were stable and homogeneous, and were significantly linear with r²  > 0.98. A field trial including 52 laboratories across China showed that the coefficient of variation (CV%) of BCR-ABL1 values among samples was in the range of 58.6%-129.6% for p210 samples and 73.2%-194.0% for p190 samples when using local standards. By contrast, when using the p210FG-CG and p190FG-CG standards, the CV% of BCR-ABL1 values was decreased to 35.6%-124.9% and 36.6%-170.6% for p210 and p190 samples, respectively. In addition, 33.3% (3/9) of the p210 and p190 samples had CV% values <50.0%, whereas 44.4% (4/9) and 77.8% (7/9) of the samples had lower CV% values when using the p210FG-CG and p190FG-CG standards.

CONCLUSION

The overall variability of detection of BCR-ABL1 transcripts decreased significantly when using the p210FG-CG or p190FG-CG standards, especially the p190FG-CG standard.

Preparation and Evaluation of Ribonuclease-Resistant Viral HIV RNA Standards Based on Armored RNA Technology

Background:

The human immunodeficiency virus type 1 (HIV-1) is an infectious viral agent that gradually extinguishes the immune system, resulting in acquired immune deficiency syndrome (AIDS). The aim of this study was to construct an RNA-positive control based on armored (AR) RNA technology, using HIV-1 RNA as a model.

Methods:

The MS2 maturase, a coat protein gene (at positions 1765 to 1787) and HIV-1 pol gene were cloned into pET-32a plasmid. The prepared plasmid was transformed into Escherichia coli strain BL2 (DE3), and the expression of the construct was induced by 1 mM of isopropyl-L-thio-D-galactopyranoside (IPTG) at 37 °C for 16 h to obtain the fabricated AR RNA. The AR RNA was precipitated and purified using polyethylene glycol and Sephacryl S-200 chromatography.

Results:

The stability of AR RNA was evaluated by treatment with DNase I and RNase A and confirmed by transmission electron microscopy and gel agarose electrophoresis. Tenfold serial dilution of AR RNA from 10¹ to 10⁵ was prepared. Real-time PCR assays had a range of detection between 10¹ and 10⁵. In addition, R² value was 0.998, and the slope of the standard curve was -3.33.

Conclusion:

Prepared AR RNA, as a positive control, could be used as a basis for launching an in-house HIV-1 virus assay and other infectious agents. It can be readily available to laboratories and HIV research centers. The AR RNA is non-infectious and highly resistant to ribonuclease enzyme and can reduce the risk of infection in the clinical laboratory.

Implications of and lessons learned from external assurance of eight influenza diagnostics in China

This study evaluated the ability of laboratories in the Chinese mainland to conduct molecular detection of seasonal A(H1N1), A(H1N1)pdm09, A(H3N2), A(H5N1), A(H7N9), A(H9N2), B(Victoria), and B(Yamagata). Based on a genetically engineered system of virus-like particles (VLPs), the National Center for Clinical Laboratories of China (NCCLs) developed an external quality assessment (EQA) panel. The panel was distributed to 35 laboratories in mainland China to investigate the proficiency of the 16 assays for influenza molecular detection. Using genetic engineering technology, VLPs encapsulating the 37 target genes of 8 influenza viruses were generated. After verification and quantification, 26 influenza virus surrogates with different concentrations were prepared for EQA. Among the 35 participating laboratories, 319 datasets were returned to the NCCLs. Overall, 95.6% (305/319) of datasets correctly reported all 30 samples, while 2.2% (7/319) of datasets with more than one incorrect result were considered as "improvable". A total of 16 misdiagnosed and 18 undiagnosed results were reported. The data analyzed in this study showed good reproducibility in China, but improvements are needed to decrease misdiagnosed and undiagnosed cases, particularly for the A(H9N2) NA gene. Moreover, VLPs are a good alternative specimen type for assay training and proficiency testing purposes.

Armored long non-coding RNA MEG3 targeting EGFR based on recombinant MS2 bacteriophage virus-like particles against hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequently diagnosed cancers worldwide. However, the treatment of patients with HCC is particularly challenging. Long non-coding RNA maternally expressed gene 3 (MEG3) has been identified as a potential suppressor of several types of tumors, but the delivery of long RNA remains problematic, limiting its applications. In the present study, we designed a novel delivery system based on MS2 virus-like particles (VLPs) crosslinked with GE11 polypeptide. This vector was found to be fast, effective and safe for the targeted delivery of lncRNA MEG3 RNA to the epidermal growth factor receptor (EGFR)-positive HCC cell lines without the activation of EGFR downstream pathways, and significantly attenuated both in vitro and in vivo tumor cell growth. Our study also revealed that the targeted delivery was mainly dependent on clathrin-mediated endocytosis and MEG3 RNA suppresses tumor growth mainly via increasing the expression of p53 and its downstream gene GDF15, but decreasing the expression of MDM2. Thus, this vector is promising as a novel delivery system and may facilitate a new approach to lncRNA based cancer therapy.

One-plasmid double-expression His-tag system for rapid production and easy purification of MS2 phage-like particles

MS2 phage-like particles (MS2 PLP) are artificially constructed pseudo-viral particles derived from bacteriophage MS2. They are able to carry a specific single stranded RNA (ssRNA) sequence of choice inside their capsid, thus protecting it against the effects of ubiquitous nucleases. Such particles are able to mimic ssRNA viruses and, thus, may serve as the process control for molecular detection and quantification of such agents in several kinds of matrices, vaccines and vaccine candidates, drug delivery systems, and systems for the display of immunologically active peptides or nanomachines. Currently, there are several different in vivo plasmid-driven packaging systems for production of MS2 PLP. In order to combine all the advantages of the available systems and to upgrade and simplify the production and purification of MS2 PLP, a one-plasmid double-expression His-tag system was designed. The described system utilizes a unique fusion insertional mutation enabling purification of particles using His-tag affinity. Using this new production system, highly pure MS2 PLP can be quickly produced and purified by a fast performance liquid chromatography (FPLC) approach. The system can be easily adapted to produce other MS2 PLP with different properties.

Use of a rapid reverse-transcription recombinase aided amplification assay for respiratory syncytial virus detection

In this study, a rapid reverse-transcription recombinase aided amplification (RT-RAA) assay was developed to detect respiratory syncytial virus (RSV) subgroups A and B, respectively. The reaction was performed at 39°C in less than 30min. The analytical sensitivities of RSVA and RSVB at 95% probability by probit regression analysis were 38copies per reaction and 35 copies per reaction, respectively, and no cross reactions with other related respiratory viruses were observed. The RT-RAA assay was further utilized to detect and subgroup 306 clinical specimens and the results showed that 79(25.82%, 79/306) samples were positive for RSV, of those 16(20.25%, 16/79) were identified as RSVA and 63(79.75%, 63/79) were RSVB, which is completely consistent with the results obtained by RSV RT-qPCR assay. In conclusion, the developed RAA assay will be of benefit as a faster, sensitive and specific alternative tool for detection of RSV.

Internal control for real-time polymerase chain reaction based on MS2 bacteriophage for RNA viruses diagnostics

BACKGROUND

Real-time reverse transcription polymerase chain reaction (RT-PCR) is routinely used to detect viral infections. In Brazil, it is mandatory the use of nucleic acid tests to detect hepatitis C virus (HCV), hepatitis B virus and human immunodeficiency virus in blood banks because of the immunological window. The use of an internal control (IC) is necessary to differentiate the true negative results from those consequent from a failure in some step of the nucleic acid test.

OBJECTIVES

The aim of this study was the construction of virus-modified particles, based on MS2 bacteriophage, to be used as IC for the diagnosis of RNA viruses.

METHODS

The MS2 genome was cloned into the pET47b(+) plasmid, generating pET47b(+)-MS2. MS2-like particles were produced through the synthesis of MS2 RNA genome by T7 RNA polymerase. These particles were used as non-competitive IC in assays for RNA virus diagnostics. In addition, a competitive control for HCV diagnosis was developed by cloning a mutated HCV sequence into the MS2 replicase gene of pET47b(+)-MS2, which produces a non-propagating MS2 particle. The utility of MS2-like particles as IC was evaluated in a one-step format multiplex real-time RT-PCR for HCV detection.

FINDINGS

We demonstrated that both competitive and non-competitive IC could be successfully used to monitor the HCV amplification performance, including the extraction, reverse transcription, amplification and detection steps, without compromising the detection of samples with low target concentrations. In conclusion, MS2-like particles generated by this strategy proved to be useful IC for RNA virus diagnosis, with advantage that they are produced by a low cost protocol. An attractive feature of this system is that it allows the construction of a multicontrol by the insertion of sequences from more than one pathogen, increasing its applicability for diagnosing different RNA viruses.

Preparation of MS2-based nanoparticles as control and standard materials for the molecular detection of dengue virus serotypes

To quantify dengue virus (DENV) and evaluate the performance of clinical laboratories using quantitative real-time polymerase chain reaction (qRT-PCR) assays, we constructed high-efficiency expression systems to produce DENV-1 to 4 nanoparticles and assessed their suitability as standard and control materials in 20 laboratories across China. Targeted gene sequences of DENV-1 to 4 were synthesized and inserted into pACYC-Duet 1-MS2 recombinant plasmids to generate corresponding nanoparticle expression systems. After collection, verification, and quantification by digital PCR (dPCR), DENV-1 to 4 nanoparticles were prepared as control and standard materials. Five positive and three negative samples of each DENV serotype in every panel were used for assessing the performance of the participating laboratories across China, as well as standard materials for the quantitative detection of DENV using qRT-PCR assays. The accuracy, sensitivity, and specificity of qRT-PCR used by the 20 evaluated laboratories were 89.6 (569/635), 85.1 (336/395), and 97.1% (233/240), respectively. Overall, sixteen (80.0%) laboratories were qualified in detecting DENV, among which five (25.0%) were designated as "competent", eleven (55.0%) were defined as "acceptable", and four (20%) were considered to be "improvable". The results generated from the DENV standard samples were significantly positively correlated with those generated by dPCR (r²=0.8698, P<0.001). In summary, DENV nanoparticles could potentially be used as controls for improving the performance of laboratories and as standards for the quantitative detection of DENV.

Fast preparation of a long chimeric armored RNA as controls for external quality assessment for molecular detection of Zika virus

BACKGROUND

The emergence of Zika virus demands accurate laboratory diagnostics. Nucleic acid testing is currently the definitive method for diagnosis of Zika infection. In 2016, an external quality assurance (EQA) for assessing the quality of molecular testing of Zika virus was carried out in China.

METHODS

A single armored RNA encapsulating a 4942-nucleotides (nt) long specific RNA sequence of Zika virus was prepared and used as positive samples. A pre-tested EQA panel, consisting of 4 negative and 6 positive samples with different concentrations of armored RNA, was distributed to 38 laboratories that perform molecular detection of Zika virus.

RESULTS

A total of 39 data sets (1 laboratory used two test kits in parallel), produced by using commercial (n=38) or laboratory developed (n=1) quantitative reverse-transcriptase PCR (qRT-PCR) kits, were received. Of these, 35 (89.7%) had correct results for all 10 samples, and 4 (10.3%) reported at least 1 error (11 in total). The testing errors were all false-negatives, highlighting the need of improvements in detecting sensitivity.

CONCLUSIONS

The EQA reveals that the majority of participating laboratories are proficient in molecular testing of Zika virus.

Preparation of MS2 Phage-Like Particles and Their Use As Potential Process Control Viruses for Detection and Quantification of Enteric RNA Viruses in Different Matrices

The detection and quantification of enteric RNA viruses is based on isolation of viral RNA from the sample followed by quantitative reverse transcription polymerase chain reaction (RT-qPCR). To control the whole process of analysis and in order to guarantee the validity and reliability of results, process control viruses (PCV) are used. The present article describes the process of preparation and use of such PCV– MS2 phage-like particles (MS2 PLP) – in RT-qPCR detection and quantification of enteric RNA viruses. The MS2 PLP were derived from bacteriophage MS2 carrying a unique and specific de novo-constructed RNA target sequence originating from the DNA of two extinct species. The amount of prepared MS2 particles was quantified using four independent methods – UV spectrophotometry, fluorimetry, transmission electron microscopy and a specifically developed duplex RT-qPCR. To evaluate the usefulness of MS2 PLP in routine diagnostics different matrices known to harbor enteric RNA viruses (swab samples, liver tissue, serum, feces, and vegetables) were artificially contaminated with specific amounts of MS2 PLP. The extraction efficiencies were calculated for each individual matrix. The prepared particles fulfill all requirements for PCV – they are very stable, non-infectious, and are genetically distinct from the target RNA viruses. Due to these properties they represent a good morphological and physiochemical model. The use of MS2 PLP as a PCV in detection and quantification of enteric RNA viruses was evaluated in different types of matrices.

Preparation and evaluation of MS2 bacteriophage-like particles packaging hepatitis E virus RNA

Hepatitis E virus (HEV) is the pathogen causing hepatitis E (HE). It arouses global public health concern since it is a zoonotic disease. The objective of this letter is to report a cost-effective internal control prepared for monitoring procedures of HEV reverse transcriptase (RT)-PCR detection. A selected conserved HEV RNA fragment was integrated into the downstream of the truncated MS2 bacteriophage genome based on Armored RNA technology. The resulting MS2-HEV gene harbored by the pET-28b-MS2-HEV plasmid was transformed into E. coli BL21(DE3) for expression analysis by SDS-PAGE. The expression products were purified and concentrated by ultrasonication and ultrafiltration separation. The morphology and stability properties of the virus-like particles (VLPs) were evaluated by electron microscopy scanning and nuclease challenges, respectively. SDS-PAGE results showed that the constructed MS2-HEV gene expressed efficiently and the purity of the VLPs was highly consistent with the result in electron microscopy. Stability evaluation results demonstrated that the prepared VLPs exhibited strong resistance to DNase I and RNase A attacks and also performed long-lasting protection of coated HEV RNA for at least 4 months at -20°C. These data revealed that the prepared VLPs meet the basic requirements of use as internal control material in the HEV RNA amplification assay.

Design of virus-based nanomaterials for medicine, biotechnology, and energy

This review provides an overview of recent developments in "chemical virology." Viruses, as materials, provide unique nanoscale scaffolds that have relevance in chemical biology and nanotechnology, with diverse areas of applications. Some fundamental advantages of viruses, compared to synthetically programmed materials, include the highly precise spatial arrangement of their subunits into a diverse array of shapes and sizes and many available avenues for easy and reproducible modification. Here, we will first survey the broad distribution of viruses and various methods for producing virus-based nanoparticles, as well as engineering principles used to impart new functionalities. We will then examine the broad range of applications and implications of virus-based materials, focusing on the medical, biotechnology, and energy sectors. We anticipate that this field will continue to evolve and grow, with exciting new possibilities stemming from advancements in the rational design of virus-based nanomaterials.

Clinical Evaluation of a Single-Tube Multiple RT-PCR Assay for the Detection of 13 Common Virus Types/Subtypes Associated with Acute Respiratory Infection

Respiratory viruses are among the most important causes of human morbidity and mortality worldwide, especially for infants and young children. In the past years, a few commercial multiplex RT-PCR assays have been used to detect respiratory viruses in spite of the high cost. In the present study, an improved single-tube multiplex reverse transcription PCR assay for simultaneous detection of 13 respiratory viruses was evaluated and compared with a previously reported two-tube assay as the reference method using clinical nasopharyngeal aspirates samples. Of 310 prospectively tested respiratory specimens selected from children hospitalized with acute respiratory illness, 226 (72.90%, 226/310) and 214 (69.03%, 214/310) positive for one or more viruses were identified by the single-tube and the two-tube assays, respectively, with combined test results showing good concordance (Kappa value = 0.874). Individually, the single-tube assay for adenovirus (Adv), human metapneumovirus (HMPV), human rhinovirus (HRV), parainfluenza virus type 1 (PIV1), parainfluenza virus type 3 (PIV3) and parainfluenza virus type 4 (PIV4) showed the significantly superior sensitivities to those of the two-tube assay. No false positives were found. In conclusion, our results demonstrates the one-tube assay revealed significant improvements over the two-tube assay in terms of the better sensitivity, more accurate quality control, less nonspecific amplification, more cost-effective and shorter turn-around time and will be a valuable tool for routine surveillance of respiratory virus infection in China.

External quality assessment for the molecular detection of MERS-CoV in China

BACKGROUND

In May 2015, an imported case of Middle East respiratory syndrome coronavirus (MERS-CoV) infection occurred in China, so rapid and reliable diagnosis of suspected cases was necessary.

OBJECTIVES

An external quality assessment (EQA) program for the molecular detection of MERS-CoV was organized by the National Center for Clinical Laboratories (NCCL).

STUDY DESIGN

MS2 virus-like particles (VLPs) encapsulating specific RNA sequences of MERS-CoV were prepared as positive specimens. The assessment panel, which comprised of three negative and seven positive samples with different concentrations of VLPs, was distributed to 56 laboratories from 16 provinces, municipalities, or autonomous regions for molecular detection.

RESULTS

Among the received data sets, three employed an in-house-developed real-time reverse-transcription polymerase chain reaction (rRT-PCR) assay and the others applied various commercial rRT-PCR kits. Overall, the majority of laboratories (46/56, 82.1%) could achieve 100% accuracy for MERS-CoV detection, but three laboratories (5.4%) still had room for improvement. Consequently, all negative samples were identified correctly, reaching 100% specificity. The false-negative rate was 3.1%, and most of the false-negative results were obtained from samples with relatively low concentration, indicating an urgent need to improve detection in weak-positive specimens.

CONCLUSIONS

The majority of participants possessed reliable diagnostic capacity for the detection of MERS-CoV. Moreover, EQA is indispensable because it can help enhance the diagnostic capability for the surveillance of MERS-CoV infections and allow comparison of the results among different laboratories.

A novel delivery platform based on Bacteriophage MS2 virus-like particles

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Here we reviewed Bacteriophage MS2 virus-like particles, including introduction to their structure, their potential as a delivery platform, and their expected use in medicine and other fields.

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Bacteriophage MS2 virus-like particles represent the novel delivery platform.

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Bacteriophage MS2 virus-like particles possess promising application prospect.

Our objective here is to review the novel delivery platform based on Bacteriophage MS2 virus-like particles (VLPs), including introduction to their structure, their potential as a delivery platform, and their expected use in medicine and other fields. Bacteriophage MS2 VLPs are nanoparticles devoid of viral genetic material and can self-assemble from the coat protein into an icosahedral capsid. As a novel delivery platform, they possess numerous features that make them suitable and attractive for targeted delivery of RNAs or DNAs, epitope peptides, and drugs within the protein capsid. In short, as a novel delivery platform, MS2 VLPs are suitable for delivery of targeted agents and hold promise for use in diagnostics, vaccines, and therapeutic modalities.

External Quality Assessment for the Detection of Measles Virus by Reverse Transcription-PCR Using Armored RNA

In recent years, nucleic acid tests for detection of measles virus RNA have been widely applied in laboratories belonging to the measles surveillance system of China. An external quality assessment program was established by the National Center for Clinical Laboratories to evaluate the performance of nucleic acid tests for measles virus. The external quality assessment panel, which consisted of 10 specimens, was prepared using armored RNAs, complex of noninfectious MS2 bacteriophage coat proteins encapsulated RNA of measles virus, as measles virus surrogate controls. Conserved sequences amplified from a circulating measles virus strain or from a vaccine strain were encapsulated into these armored RNAs. Forty-one participating laboratories from 15 provinces, municipalities, or autonomous regions that currently conduct molecular detection of measles virus enrolled in the external quality assessment program, including 40 measles surveillance system laboratories and one diagnostic reagent manufacturer. Forty laboratories used commercial reverse transcription-quantitative PCR kits, with only one laboratory applying a conventional PCR method developed in-house. The results indicated that most of the participants (38/41, 92.7%) were able to accurately detect the panel with 100% sensitivity and 100% specificity. Although a wide range of commercially available kits for nucleic acid extraction and reverse transcription polymerase chain reaction were used by the participants, only two false-negative results and one false-positive result were generated; these were generated by three separate laboratories. Both false-negative results were obtained with tests performed on specimens with the lowest concentration (1.2 × 10⁴ genomic equivalents/mL). In addition, all 18 participants from Beijing achieved 100% sensitivity and 100% specificity. Overall, we conclude that the majority of the laboratories evaluated have reliable diagnostic capacities for the detection of measles virus.

A novel method to produce armored double-stranded DNA by encapsulation of MS2 viral capsids

With the rapid development of molecular diagnostic techniques, there is a growing need for quality controls and standards with favorable properties to monitor the entire detection process. In this study, we describe a novel method to produce armored hepatitis B virus (HBV) and human papillomavirus (HPV) DNA for use in nucleic acid tests, which was confirmed to be stable, homogeneous, noninfectious, nuclease resistant, and safe for shipping. We demonstrated that MS2 bacteriophage could successfully package double-stranded DNA of 1.3-, 3-, 3.5-, and 6.5-kb length into viral capsids with high reassembly efficiency. This is the first application of RNA bacteriophage MS2 as a platform to encapsulate double-stranded DNA, forming virus-like particles (VLPs) which were indistinguishable from native MS2 capsids in size and morphology. Moreover, by analyzing the interaction mechanism of pac site and the MS2 coat protein (CP), we found that in addition to the recognized initiation signal TR-RNA, TR-DNA can also trigger spontaneous reassembly of CP dimers, providing a more convenient and feasible method of assembly. In conclusion, this straightforward and reliable manufacturing approach makes armored DNA an ideal control and standard for use in clinical laboratory tests and diagnostics, possessing prospects for broad application, especially providing a new platform for the production of quality controls for DNA viruses.

Methods for Preparation of MS2 Phage-Like Particles and Their Utilization as Process Control Viruses in RT-PCR and qRT-PCR Detection of RNA Viruses From Food Matrices and Clinical Specimens

RNA viruses are pathogenic agents of many serious infectious diseases affecting humans and animals. The detection of pathogenic RNA viruses is based on modern molecular methods, of which the most widely used methods are the reverse transcription polymerase chain reaction (RT-PCR) and the real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). All steps of RT-PCR and qRT-PCR should be strictly controlled to ensure the validity of obtained results. False-negative results may be caused not only by inhibition of RT or/and PCR steps but also by failure of the nucleic acid extraction step, particularly in the case of viral RNA extraction. The control of nucleic acid extraction generally involves the utilization of a non-pathogenic virus (process control virus) of similar structural properties to those of the target virus. Although in clinical samples the use of such process control virus is only recommended, in other kinds of settings such as food matrices its use is necessary. Currently, several different process control viruses are used for these purposes. Process control viruses can also be constructed artificially using technology for production of MS2 phage-like particles, which have many advantages in comparison with other used controls and are especially suited for controlling the detection and quantification of certain types of RNA viruses. The technology for production of MS2 phage-like particles is theoretically well established, uses the knowledge gained from the study of the familiar bacteriophage MS2 and utilizes many different approaches for the construction of the various process control viruses. Nevertheless, the practical use of MS2 phage-like particles in routine diagnostics is relatively uncommon. The current situation with regard to the use of MS2 phage-like particles as process control viruses in detection of RNA viruses and different methods of their construction, purification and use are summarized and discussed in this review.

Evaluation of a commercially available synthetic RNA lipid enveloped control molecule

Detection of viral ribonucleic acid with RT PCR is a useful tool for viral detection. One of the drawbacks of this technique is the difficulty in including an internal control molecule to ensure the validity of the extraction and amplification process. In this study the potential usefulness of a novel lipid enveloped commercially available RNA control molecule is investigated. Initial optimisation of the detection assay was performed by amplification of IC (internal control) spiked into PCR water. Thirty-two clinical respiratory samples were spiked with the IC before and after extraction and RT PCR was then performed. Inefficient extraction was simulated. Inhibition of the RT PCR was achieved by serial dilution of heparin sulfate into samples post extraction. No Targets that matched the IC (Internal Control) primers were identified in 32 extracted sputum samples as determined by the absence of non specific amplification curves. The unextracted IC had an increased CT (cycle threshold) value compared to IC that had been extracted. Inefficient extraction was detected by an increased CT. Increasing concentrations of heparin inhibited the PCR in a predictable fashion. The Bioline IC molecule provides a stable RNA IC that has acceptable performance characteristics.

Development of a versatile and stable internal control system for RT-qPCR assays

RT-qPCR, an established method for the detection of RNA viruses, requires internal RNA controls for the correct interpretation of PCR results. Robust and versatile RT-PCR controls can be achieved for example by packaging RNA into a virus-derived protein shell. In this study a MS2-based internal control system was developed, that allows stable and universal packing of different RNAs into non-infectious, non-lytic MS2-based viral like particles (VLPs). Two competitive internal controls for a hantavirus assay and a Crimean-Congo Hemorrhagic Fever Virus (CCHFV) assay were cloned for the expression of VLPs. The expression of VLPs containing the RNA of interest could be induced with arabinose in Escherichia coli. The VLPs proved to be temperature resistant and could be frozen and thawed several times without degradation. Distinction of IC RNA from the target RNA was facilitated by a clear shift in the melting temperature or by specific hybridization signals. Furthermore, target and IC PCR amplification could be easily distinguished by their size in gel-electrophoretic analyses. Limits of detection were determined, demonstrating that the application of the IC did not reduce the sensitivity of the target RT-qPCR reactions. The system can be adapted to nearly any required sequence, resulting in a highly flexible method with broad range applications.

External quality assessment for Avian Influenza A (H7N9) Virus detection using armored RNA

An external quality assessment (EQA) program for the molecular detection of avian influenza A (H7N9) virus was implemented by the National Center for Clinical Laboratories (NCCL) of China in June 2013. Virus-like particles (VLPs) that contained full-length RNA sequences of the hemagglutinin (HA), neuraminidase (NA), matrix protein (MP), and nucleoprotein (NP) genes from the H7N9 virus (armored RNAs) were constructed. The EQA panel, comprising 6 samples with different concentrations of armored RNAs positive for H7N9 viruses and four H7N9-negative samples (including one sample positive for only the MP gene of the H7N9 virus), was distributed to 79 laboratories in China that carry out the molecular detection of H7N9 viruses. The overall performances of the data sets were classified according to the results for the H7 and N9 genes. Consequently, we received 80 data sets (one participating group provided two sets of results) which were generated using commercial (n = 60) or in-house (n = 17) reverse transcription-quantitative PCR (qRT-PCR) kits and a commercial assay that employed isothermal amplification method (n = 3). The results revealed that the majority (82.5%) of the data sets correctly identified the H7N9 virus, while 17.5% of the data sets needed improvements in their diagnostic capabilities. These "improvable" data sets were derived mostly from false-negative results for the N9 gene at relatively low concentrations. The false-negative rate was 5.6%, and the false-positive rate was 0.6%. In addition, we observed varied diagnostic capabilities between the different commercially available kits and the in-house-developed assays, with the assay manufactured by BioPerfectus Technologies (Jiangsu, China) performing better than the others. Overall, the majority of laboratories have reliable diagnostic capacities for the detection of H7N9 virus.

Optimization of PCR for quantification of simian immunodeficiency virus genomic RNA in plasma of rhesus macaques (Macaca mulatta) using armored RNA

INTRODUCTION

Quantification of plasma viral load (PVL) is used to monitor disease progression in SIV-infected macaques. This study was aimed at optimizing of performance characteristics of the quantitative PCR (qPCR) PVL assay.

METHODS

The PVL quantification procedure was optimized by inclusion of an exogenous control hepatitis C virus armored RNA (aRNA), a plasma concentration step, extended digestion with proteinase K, and a second RNA elution step. Efficiency of viral RNA (vRNA) extraction was compared using several commercial vRNA extraction kits. Various parameters of qPCR targeting the gag region of SIVmac239, SIVsmE660, and the LTR region of SIVagmSAB were also optimized.

RESULTS

Modifications of the SIV PVL qPCR procedure increased vRNA recovery, reduced inhibition and improved analytical sensitivity. The PVL values determined by this SIV PVL qPCR correlated with quantification results of SIV RNA in the same samples using the 'industry standard' method of branched-DNA (bDNA) signal amplification.

CONCLUSIONS

Quantification of SIV genomic RNA in plasma of rhesus macaques using this optimized SIV PVL qPCR is equivalent to the bDNA signal amplification method, less costly and more versatile. Use of heterologous aRNA as an internal control is useful for optimizing performance characteristics of PVL qPCRs.

Messenger RNA vaccine based on recombinant MS2 virus-like particles against prostate cancer

Prostate cancer (PCa) is the most diagnosed cancer in the western male population with high mortality. Recently, alternative approaches based on immunotherapy including mRNA vaccines for PCa have shown therapeutic promise. However, for mRNA vaccine, several disadvantages such as the instability of mRNA, the high cost of gold particles, the limited production scale for mRNA-transfected dendritic cells in vitro, limit their development. Herein, recombinant bacteriophage MS2 virus-like particles (VLPs), which based on the interaction of a 19-nucleotide RNA aptamer and the coat protein of bacteriophage MS2, successfully addressed these questions, in which target mRNA was packaged by MS2 capsid. MS2 VLP-based mRNA vaccines were easily prepared by recombinant protein technology, nontoxic and RNase-resistant. We show the packaged mRNA was translated into protein as early as 12 hr after phagocytosed by macrophages. Moreover, MS2 VLP-based mRNA vaccines induced strong humoral and cellular immune responses, especially antigen-specific cytotoxic T-lymphocyte (CTL) and balanced Th1/Th2 responses without upregulation of CD4(+) regulatory T cells, and protected C57BL/6 mice against PCa completely. As a therapeutic vaccine, MS2 VLP-based mRNA vaccines delayed tumor growth. Our results provide proof of concept on the efficacy and safety of MS2 VLP-based mRNA vaccine, which provides a new delivery approach for mRNA vaccine and implies important clinical value for the prevention and therapy of PCa.

Development of a microRNA delivery system based on bacteriophage MS2 virus-like particles

Recently, microRNA (miRNA)-mediated RNA interference has been developed as a useful tool in gene function analysis and gene therapy. A major obstacle in miRNA-mediated RNAi is cellular delivery, which requires an efficient and flexible delivery system. The self-assembly of the MS2 bacteriophage capsids has been used to develop virus-like particles (VLPs) for RNA and drug delivery. However, MS2 VLP-mediated miRNA delivery has not yet been reported. We therefore used an Escherichia coli expression system to produce the pre-miR 146a contained MS2 VLPs, and then conjugated these particles with HIV-1 Tat(47-57) peptide. The conjugated MS2 VLPs effectively transferred the packaged pre-miR146a RNA into various cells and tissues, with 0.92-14.76-fold higher expression of miR-146a in vitro and about two-fold higher expression in vivo, and subsequently suppressed its targeting gene. These findings suggest that MS2 VLPs can be used as a novel vehicle in miRNA delivery systems, and may have applications in gene therapy.

External quality assessment for enterovirus 71 and coxsackievirus A16 detection by reverse transcription-PCR using armored RNA as a virus surrogate

Three armored RNAs (virus-like particles [VLPs]) containing target sequences from enterovirus 71 (EV71) and coxsackievirus A16 (CA16) and a pan-enterovirus (pan-EV) sequence were constructed and used in an external quality assessment (EQA) to determine the performance of laboratories in the detection of EV71 and CA16. The EQA panel, which consisted of 20 samples, including 14 positive samples with different concentrations of EV and either EV71 or CA16 armored RNAs, 2 samples with all 3 armored RNAs, and 4 negative-control samples (NaN(3)-preserved minimal essential medium [MEM] without VLPs), was distributed to 54 laboratories that perform molecular diagnosis of hand, foot, and mouth disease (HFMD) virus infections. A total of 41 data sets from 41 participants were returned; 5 (12.2%) were generated using conventional in-house reverse transcription-PCR (RT-PCR) assays, and 36 (87.8%) were generated using commercial real-time RT-PCR assays. Performance assessments of laboratories differed; 12 (29.3%) showed a need for improvement. Surprisingly, 4 laboratories were unable to detect EV71 RNA in any samples, even those containing the highest concentration of 10(7) IU/ml. Furthermore, the detection sensitivity for EV71 among all laboratories (82.1%) was substantially lower than that for EV (97.4%) or CA16 (95.1%). Overall, the results of the present study indicate that EQA should be performed periodically to help laboratories monitor their ability to detect HFMD viruses and to improve the comparability of results from different laboratories.

Failure to detect Xenotropic murine leukaemia virus-related virus in Chinese patients with chronic fatigue syndrome

Background

Recent controversy has surrounded the question of whether xenotropic murine leukaemia virus-related virus (XMRV) contributes to the pathogenesis of chronic fatigue syndrome (CFS). To investigate the question in a Chinese population, 65 CFS patients and 85 blood donor controls were enrolled and multiplex real-time PCR or reverse transcriptase PCR (RT-PCR) was developed to analyze the XMRV infection status of the study participants. The assay was standardized by constructing plasmid DNAs and armored RNAs as XMRV standards and competitive internal controls (CICs), respectively.

Results

The sensitivities of the multiplex real-time PCR and RT-PCR assays were 20 copies/reaction and 10 IU/ml, respectively, with 100% specificity. The within-run precision coefficient of variation (CV) ranged from 1.76% to 2.80% and 1.70% to 2.59%, while the between-run CV ranged from 1.07% to 2.56% and 1.06% to 2.74%. XMRV was not detected in the 65 CFS patients and 65 normal individuals out of 85 controls.

Conclusions

This study failed to show XMRV in peripheral blood mononuclear cells (PBMCs) and plasma of Chinese patients with CFS. The absence of XMRV nucleic acids does not support an association between XMRV infection and the development of CFS in Chinese.

A novel duplex real-time reverse transcriptase-polymerase chain reaction assay for the detection of hepatitis C viral RNA with armored RNA as internal control

BACKGROUND

The hepatitis C virus (HCV) genome is extremely heterogeneous. Several HCV infections can not be detected using currently available commercial assays, probably because of mismatches between the template and primers/probes. By aligning the HCV sequences, we developed a duplex real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay using 2 sets of primers/probes and a specific armored RNA as internal control. The 2 detection probes were labelled with the same fluorophore, namely, 6-carboxyfluorescein (FAM), at the 5' end; these probes could mutually combine, improving the power of the test.

RESULTS

The limit of detection of the duplex primer/probe assay was 38.99 IU/ml. The sensitivity of the assay improved significantly, while the specificity was not affected. All HCV genotypes in the HCV RNA Genotype Panel for Nucleic Acid Amplification Techniques could be detected. In the testing of 109 serum samples, the performance of the duplex real-time RT-PCR assay was identical to that of the COBAS AmpliPrep (CAP)/COBAS TaqMan (CTM) assay and superior to 2 commercial HCV assay kits.

CONCLUSIONS

The duplex real-time RT-PCR assay is an efficient and effective viral assay. It is comparable with the CAP/CTM assay with regard to the power of the test and is appropriate for blood-donor screening and laboratory diagnosis of HCV infection.