Polymerase Spiral Reaction Assay for Rapid and Real Time Detection of West Nile Virus From Clinical Samples

Polymerase Spiral Reaction (PSR) as a point-of-care diagnostic assay: A systematic review

INTRODUCTION

The current systematic review aimed to collect and analyze the comprehensive evidence regarding Polymerase Spiral Reaction (PSR) and to estimate its diagnostic performance and usefulness as a point-of-care (PoC) assay.

METHODS

Literature was retrieved systematically from 2015 to 2023 from PubMed and Scopus. Studies were screened and selected against pre-determined inclusion and exclusion criteria. Quality assessment and risk of bias were critiqued using QUADAS-2. A systematic, qualitative narrative synthesis was employed to synthesize the data.

RESULTS

11 studies were selected for the systematic review, testing diseases in humans utilizing PSR. Only 2 studies clinically validated the test with a sample size > 150. 5 studies were of poor quality; 3 studies were of moderate quality and 3 studies were deemed to be of high quality. 3 studies quantified the diagnostic throughput and reported clinical sensitivity and specificity of PSR approaching to be > 92% and ~ 100%, respectively.

CONCLUSION

Polymerase spiral reaction promises to be an optimistic isothermal assay; however, a huge research gap can be attributed to the lack of statistical and clinical evidence to validate the assay. Adequate research, focused on optimization, coupled with statistical and clinical validation, can help in estimating its true diagnostic potential and applicability.

REGISTRATION AND PROTOCOL

A detailed protocol of this review is registered and available in Prospero (registration number CRD42023406265).

Simplified visual detection of Kyasanur Forest Disease virus employing Reverse Transcriptase-Polymerase Spiral Reaction (RT-PSR)

Among recently prevalent tick-borne infections in India, Kyasanur Forest Virus Disease (KFD) is an important public health concern. During last decade the emergence of cases apart from endemic zone raised concern about case positivity. Early diagnosis is therefore very important in disease management and primary containment. This study, aimed to develop a simplified viral RNA extraction in combination to dry down format of novel isothermal assay for (Reverse Transcription- Polymerase Spiral reaction) specific and rapid identification of Kyasanur Forest Disease Virus targeting viral envelope gene. The one step method was optimized by magnetic bead based viral RNA extraction followed by isothermal RT-PSR assay in heat bath at 63⁰C for 60 minutes. Further, visual results interpretation was done by color change of Hydroxy Naphthol Blue dye. The detection limit of the assay was found 10 RNA copies/rxn with comparable to silica column based viral RNA combined real time qPCR. No cross reactivity was observed with other closely related flaviviruses. The assay was evaluated with clinical samples has shown >99% concordance between two methods. This is the first report of sample extraction coupled isothermal detection of KFD in a simplified manner without a need of any hi-end equipment. The assay developed here has potential to use as an alternate for field-based detection in resource limited settings for KFD.

Development of a Polymerase Spiral Reaction-Based Isothermal Assay for Rapid Identification of Thrips palmi

Thrips cause considerable economic losses to a wide range of food, feed, and forest crops. They also transmit several plant viruses. Being cryptic, it is often difficult to distinguish thrips species in crops and large consignments by conventional methods. Melon thrips (Thrips palmi Karny, Thysanoptera: Thripidae) is an invasive insect pest of vegetables, legumes, and ornamentals besides being vector to several viruses. It poses a threat to domestic and international plant biosecurity and can invade and establish in new areas. Here, we report a polymerase spiral reaction (PSR)-based isothermal assay for rapid, sensitive, specific, low-cost, and on-site detection of T. palmi. To the best of our knowledge, this is the first application of PSR in the identification of any insect species. A primer pair designed based on 3′-polymorphism of mtCOIII region can specifically identify T. palmi without any cross-reactivity with predominant thrips species. The assay uses crude lysate of a single thrips saving time and reagents involved in nucleic acid extraction. The presence of T. palmi is visualized by the appearance of bright fluorescence under ultraviolet light or a change in reaction color thus avoiding gel electrophoresis steps. The entire process can be completed in 70 min on-site using only an ordinary water bath. The assay is sensitive to detecting as little as 50 attograms of T. palmi template. The assay was validated with known thrips specimens and found to be efficient in diagnosing T. palmi under natural conditions. The described method will be useful for non-expert personnel to detect an early infestation, accidental introduction to a new area, restrict the spread of diseases and formulate appropriate management strategies.