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

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.

A novel one-step quantitative reverse transcription PCR assay for selective amplification of hepatitis B virus pregenomic RNA from a mixture of HBV DNA and RNA in serum

Current antiviral therapies against hepatitis B virus (HBV) infections, such as treatment with nucleos(t)ide analogs (NAs) and interferon alpha, can significantly lower HBV DNA titers, eventually to undetectable levels. However, it is still difficult to completely eliminate the stable template of HBV, the covalently closed circular DNA (cccDNA), and this contributes to viral rebound when treatment is discontinued. HBV pregenomic RNA (pgRNA), which was recently found to be present in the enveloped mature HBV viral particle in blood, is tentatively regarded, with still accumulating clinical evidence, as a novel bona fide virological marker reflecting the amount and status of cccDNA when serum HBV DNA becomes undetectable. HBV pgRNA and DNA share almost identical sequences, and it is therefore difficult to differentiate pgRNA from viral DNA using normal PCR methods. To exclude interference from viral DNA, methods for measuring pgRNA usually require a selective DNA degradation step, which is complicated and time-consuming and also compromises the accuracy of detection. In this study, we developed a simplified quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay with improved accuracy achieved by probing the polyA tail of pgRNA. Using clinical serum samples, we observed that not all patients share the same 3' sequence, suggesting slight differences between HBV strains in the way they end transcription. We then designed and evaluated a universal primer and probe set for distinguishing HBV pgRNA from HBV DNA. Our results demonstrated that a one-step qRT-PCR assay could selectively amplify HBV pgRNA from a mixture of HBV RNA and DNA, which is valuable for clinical applications.