Development of an internally controlled, homogeneous polymerase chain reaction assay for the simultaneous detection and discrimination of herpes simplex virus types 1 and 2 and varicella-zoster virus

Implementation and Evaluation of a Fully Automated Multiplex Real-Time PCR Assay on the BD Max Platform to Detect and Differentiate Herpesviridae from Cerebrospinal Fluids

A fully automated multiplex real-time PCR assay--including a sample process control and a plasmid based positive control--for the detection and differentiation of herpes simplex virus 1 (HSV1), herpes simplex virus 2 (HSV2) and varicella-zoster virus (VZV) from cerebrospinal fluids (CSF) was developed on the BD Max platform. Performance was compared to an established accredited multiplex real time PCR protocol utilizing the easyMAG and the LightCycler 480/II, both very common devices in viral molecular diagnostics. For clinical validation, 123 CSF specimens and 40 reference samples from national interlaboratory comparisons were examined with both methods, resulting in 97.6% and 100% concordance for CSF and reference samples, respectively. Utilizing the BD Max platform revealed sensitivities of 173 (CI 95%, 88-258) copies/ml for HSV1, 171 (CI 95%, 148-194) copies/ml for HSV2 and 84 (CI 95%, 5-163) copies/ml for VZV. Cross reactivity could be excluded by checking 25 common viral, bacterial and fungal human pathogens. Workflow analyses displayed shorter test duration as well as remarkable fewer and easier preparation steps with the potential to reduce error rates occurring when manually assessing patient samples. This protocol allows for a fully automated PCR assay on the BD Max platform for the simultaneously detection of herpesviridae from CSF specimens. Singular or multiple infections due to HSV1, HSV2 and VZV can reliably be differentiated with good sensitivities. Control parameters are included within the assay, thereby rendering its suitability for current quality management requirements.

Development of a multiplex real-time PCR for the simultaneous detection of herpes simplex and varicella zoster viruses in cerebrospinal fluid and lesion swab specimens

Herpes simplex viruses (HSV) and varicella zoster virus (VZV) can have very similar and wide-ranging clinical presentations. Rapid identification is necessary for timely antiviral therapy, especially with infections involving the central nervous system, neonates, and immunocompromised individuals. Detection of HSV-1, HSV-2 and VZV was combined into one real-time PCR reaction utilizing hydrolysis probes. The assay was validated on the LightCycler(®) (Roche) and Applied Biosystems 7500 Real-Time PCR System (Thermo Fisher Scientific Inc.) to detect alphaherpesviruses in cerebral spinal fluid (CSF) and lesion swab specimens, respectively. Validation data on blood and tissue samples are also presented. The multiplex assay showed excellent sensitivity, specificity and reproducibility when compared to two singleplex real-time PCR assays for CSF samples and direct fluorescent antigen/culture for lesion swab samples. Implementation of the multiplex assay has facilitated improved sensitivity and accuracy as well as reduced turn-around-times and costs. The results from a large data set of 16,622 prospective samples tested between August 16, 2012 to February 1, 2014 at the Provincial Laboratory for Public Health (Alberta, Canada) are presented here.

Development and Validation of a Laboratory-Developed Multiplex Real-Time PCR Assay on the BD Max System for Detection of Herpes Simplex Virus and Varicella-Zoster Virus DNA in Various Clinical Specimens

A multiplex real-time PCR (quantitative PCR [qPCR]) assay detecting herpes simplex virus (HSV) and varicella-zoster virus (VZV) DNA together with an internal control was developed on the BD Max platform combining automated DNA extraction and an open amplification procedure. Its performance was compared to those of PCR assays routinely used in the laboratory, namely, a laboratory-developed test for HSV DNA on the LightCycler instrument and a test using a commercial master mix for VZV DNA on the ABI7500fast system. Using a pool of negative cerebrospinal fluid (CSF) samples spiked with either calibrated controls for HSV-1 and VZV or dilutions of a clinical strain that was previously quantified for HSV-2, the empirical limit of detection of the BD Max assay was 195.65, 91.80, and 414.07 copies/ml for HSV-1, HSV-2, and VZV, respectively. All the samples from HSV and VZV DNA quality control panels (Quality Control for Molecular Diagnostics [QCMD], 2013, Glasgow, United Kingdom) were correctly identified by the BD Max assay. From 180 clinical specimens of various origins, 2 CSF samples were found invalid by the BD Max assay due to the absence of detection of the internal control; a concordance of 100% was observed between the BD Max assay and the corresponding routine tests. The BD Max assay detected the PCR signal 3 to 4 cycles earlier than did the routine methods. With results available within 2 h on a wide range of specimens, this sensitive and fully automated PCR assay exhibited the qualities required for detecting simultaneously HSV and VZV DNA on a routine basis.

Evaluation of non-extracted genital swabs for real-time HSV PCR

Nucleic acid extraction of clinical samples is accepted as a key requirement in molecular diagnostics. At Barts Health NHS Trust, swabs taken from patients with clinical suspicion of HSV infection were routinely extracted on the Qiagen MDx BioRobot prior to testing with a real-time triplex PCR for HSV1, HSV2, and VZV. The aim of this study was to adapt an existing HSV1/HSV2/VZV real-time PCR by replacing VZV with phocine herpesvirus 1 (PhHV) as an internal control (IC) and evaluate whether this adapted assay required the nucleic acid extraction step for predominantly genital swabs. First 313 non-extracted and extracted swabs were tested in parallel with the existing triplex HSV1/HSV2/VZV real-time PCR. The second stage involved testing 176 non-extracted swabs using a triplex real-time PCR for HSV1, HSV2, and PhHV and comparing the results with the samples extracted and tested by the original triplex assay. The results correlated well when the existing assay was used, with only three non-extracted samples that would have been reported as negative compared to the extracted sample result (Cq s 33, 39, 35-two samples HSV1, one sample HSV2). In the evaluation using the adapted assay containing the IC, two of 176 samples were discordant, where a HSV negative non-extracted sample result would have been reported differently to the extracted sample result (Cq s 32, 33-both HSV1). This study demonstrated that it is feasible to test non-extracted swabs for HSV in a real-time PCR that includes an IC. J. Med. Virol. 87: 125-129, 2015. © 2014 Wiley Periodicals, Inc.

Comparison of two multiplexed PCR assays for the detection of HSV-1, HSV-2, and VZV with extracted and unextracted cutaneous and mucosal specimens

BACKGROUND

Several analyte specific reagents (ASRs) are available for the detection and differentiation of HSV-1, HSV-2, and VZV in clinical specimens. However, there is limited data on the test performance of these reagents used in multiplexed PCR assays.

OBJECTIVE

This study compared the performance of two multiplexed ASR sets for detection of HSV-1, HSV-2, and VZV in dermal specimens.

STUDY DESIGN

Two commercially available ASRs were combined to produce multiplexed PCR assays for simultaneous detection of HSV-1, HSV-2, and VZV. Seeded samples were used to determine the limit of detection (LOD) for each assay. Patient samples (n=156) were tested in duplicate and results for each method compared to the reference standard of culture. Both extracted and unextracted specimens were used in the study.

RESULTS

Both multiplexed PCR assays showed similar test performance, with minimal LOD differences observed. The LOD was 10(3) copies/mL for HSV-1 and HSV-2 using the Focus assay compared to 5×10(3) copies/mL and 2×10(4) copies/mL, respectively for the EraGen assay. Both assays showed equal performance for VZV with a LOD of 5×10(3) copies/mL. Analytical specificity testing showed no cross reactivity with other selected DNA viruses. Both assays showed similar performance when clinical samples were tested using both extracted and unextracted specimens.

CONCLUSION

Commercially available ASRs can be successfully multiplexed for the PCR detection of HSV-1, HSV-2, and VZV using dermal specimens. Either direct testing or nucleic acid extracted specimens can be used with similar performance in these assays.

Challenges in designing a Taqman-based multiplex assay for the simultaneous detection of Herpes simplex virus types 1 and 2 and Varicella-zoster virus

To optimise molecular detection of herpesviruses an internally controlled multiplex Taqman-PCR for the detection of Herpes simplex virus 1 (HSV1), Herpes simplex virus 2 (HSV2) and Varicella-zoster virus (VZV) was developed. The selection of the dye combination working on the ABI 7700 cycler for this multiplex PCR revealed crosstalk phenomena between several combinations of reference dyes and reporter dyes. A final dye combination with CY5 as reference dye and FAM/JOE/TXR as reporter dyes was selected. The influence of the concentration of the internal positive control (IPC) concentration on the quantitative results of HSV1, HSV2 and VZV positive patient samples was analysed. The results indicate that high IPC concentrations are detrimental for the sensitivity of the multiplex assay and that the presence of the IPC molecule narrows the dynamic range of the duplex PCRs between any of the virus PCRs and the IPC-PCR. The optimised multiplex assay detecting HSV1, HSV2 and VZV using 10(3) IPC molecules showed a performance and sensitivity comparable to that of the individual assays.

Cryptosporidium--biotechnological advances in the detection, diagnosis and analysis of genetic variation

Cryptosporidiosis is predominantly a gastrointestinal disease of humans and other animals, caused by various species of protozoan parasites representing the genus Cryptosporidium. This disease, transmitted mainly via the faecal-oral route (in water or food), is of major socioeconomic importance worldwide. The diagnosis and genetic characterization of the different species and population variants (usually recognised as "genotypes" or "subgenotypes") of Cryptosporidium is central to the prevention, surveillance and control of cryptosporidiosis, particularly given that there is presently no broadly applicable treatment regimen for this disease. Although traditional phenotypic techniques have had major limitations in the specific diagnosis of cryptosporidiosis, there have been major advances in the development of molecular analytical and diagnostic tools. This article provides a concise account of Cryptosporidium and cryptosporidiosis, and focuses mainly on recent advances in nucleic acid-based approaches for the diagnosis of cryptosporidiosis and analysis of genetic variation within and among species of Cryptosporidium. These advances represent a significant step toward an improved understanding of the epidemiology as well as the prevention and control of cryptosporidiosis.

A multiplexed TaqMan assay for the detection of arthropod-borne flaviviruses

Arboviruses in the genus Flavivirus are major causes of human disease worldwide, and yet they are widely under reported. This is partially due to the classical methods of detection, using virologic or immunologic techniques, which typically lack sensitivity and specificity or require biological containment facilities in order to manipulate infectious cultures. Molecular detection assays based on broadly reactive (degenerate) primers also tend to have differential and lower sensitivity for many flaviviruses. In this study, an assay was designed to test for many flaviviruses using species-specific and group-specific primers in a single reaction. This real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay combines flavivirus species-specific and group-specific TaqMan primers and probes (some previously described) into a single tube and subjected it to a standardized thermocycling conditions. The multiplex assay contains specific detection for St. Louis encephalitis virus, West Nile virus, and consensus sequences for tick-borne encephalitis complex groups: Russian Spring-Summer encephalitis and Central European encephalitis viruses. The assay also contained group-specific primers for Dengue I, II, III and IV viruses. Viral RNA was extracted from infected cell-culture derived stock viruses, field samples, or was synthesized as subgenomic target RNA molecules. All flavivirus species and sample types were detected by the multiplex assay. A sensitivity analysis of the assay suggested that the multiplex was no less able to detect low virus titer samples than the single-virus assay. This technique allows for a collection of specific assays to be used to screen for the presence of many flaviviruses of interest while saving labor and reagents, and without sacrificing sensitivity. The results demonstrated that these viruses can be screened for specifically in multiplex reactions using the rapid and sensitive method of real time qRT-PCR.