Analytical and Clinical Evaluation of a TaqMan Real-Time PCR Assay for the Detection of Chikungunya Virus

Selection of DNA aptamers against Chikungunya virus Envelope 2 Protein and their application in sandwich ELASA

Chikungunya fever, caused by Chikungunya virus (CHIKV) exhibits clinical features that mimic that of other arbovirus infections such as dengue. CHIKV Envelope 2 (E2) protein, an antigenic epitope of CHIKV, has been identified as an ideal marker for diagnostics. The current CHIKV antigen detection tests are largely based on antibodies but are beleaguered by issues such as sensitivity to high temperature, expensive and prone to batch-to-batch variations. Aptamers are suitable alternatives to antibodies as they are cheaper and have no batch-to-batch variations compared to antibodies. In this study, DNA aptamer selection against CHIKV E2 proteins was performed using two different randomized ssDNA libraries. Chik-2 (96-mer) and Chik-3 (76-mer) were isolated from these two libraries and were identified as the potential aptamers against CHIKV E2 protein. The binding affinity of Chik-2 and Chik-3 against CHIKV E2 protein was estimated at 177.5 ± 32.69 nM and 30.01 ± 3.60 nM, respectively. A sandwich ELASA was developed, and this assay showed a detection limit of 2.17 x 103 PFU/mL. The sensitivity and specificity of the assay were 80 % and 100 %, respectively. The assay showed no cross-reactivity with dengue-positive samples, demonstrating the enormous diagnostic potential of these aptamers for the detection of CHIKV.

Dengue and chikungunya virus dynamics, identification, and monitoring in wastewater

Monitoring wastewater is an effective strategy for supporting clinical surveillance for viral infections. Wastewater monitoring, also known as wastewater-based epidemiology (WBE), uses existing wastewater collection networks to obtain a composite sample of a population that can be used to predict disease dynamics in a specific area. Viruses such as dengue and chikungunya are primarily transmitted through the bites of infected Aedes mosquito species. The prevalence of the Aedes mosquito in tropical and subtropical regions makes these diseases a serious threat to public health. Employing wastewater surveillance, monitoring, and regulating the spread of diseases like dengue and chikungunya-notably caused by mosquitoes-has been recommended. However, understanding the dynamics of viral release and its persistence in wastewater is critical for monitoring purposes. Although methods for recovering RNA for some viruses from wastewater have been developed, the same approach does not work equally well for viruses such as dengue and chikungunya due to low levels of viral RNA and susceptibility to degradation. As a result, a tailored approach to recovering these viruses from wastewater is required. This review summarizes viral release from infected hosts, its dynamics, and approaches for dengue and chikungunya wastewater surveillance. The review also identifies existing knowledge gaps in viral persistence in wastewater and recovery.

Rapid and sensitive detection of chikungunya virus using one-tube, reverse transcription, semi-nested multi-enzyme isothermal rapid amplification, and lateral flow dipstick assays

Chikungunya fever is an acute infectious disease caused by chikungunya virus (CHIKV), which is transmitted by Aedes mosquitoes. Simple, rapid, and sensitive detection of CHIKV is critical for its prevention and spread. To address this issue, we combined one-tube, reverse transcription semi-nested, multi-enzyme isothermal rapid amplification, and lateral flow dipstick strips assay to detect CHIKV RNA. The study used a 318-bp gene fragment of CHIKV NSP4 as the target of the assay. This method of amplification takes 30 min for two-step amplification at 39°C. The dilution of amplification products was added to the LFD strip with results visible to the naked eye after 10 min. The method has a sensitivity of 1 copy/μL for the detection of CHIKV RNA, which is 100-fold higher than the conventional reverse transcription-multi-enzyme isothermal rapid amplification and 10-fold higher than the reverse transcription quantitative PCR (RT-qPCR) method. In addition, the method demonstrated good specificity and a better detection rate (85.7%, 18 of 21) than RT-qPCR (80.9%, 17 of 21) in clinically confirmed patient plasma samples. Thus, the rapid CHIKV RNA assay developed in this study will be an important tool for the rapid and accurate screening of patients for chikungunya fever.

IMPORTANCE

This study presents a new one-tube, reverse transcription semi-nested, multi-enzyme isothermal rapid amplification assay combined with lateral flow dipstick strips for the detection of CHIKV. This technique significantly improves sensitivity and outperforms RT-qPCR for the detection of CHIKV, especially in samples with low viral loads. It is also significantly faster than conventional RT-qPCR and does not require special equipment or a standard PCR laboratory. The combination of the isothermal amplification technology developed in this study with point-of-care molecular testing offers the potential for rapid, on-site, low-cost molecular diagnosis of CHIKV.

An improved alphaviruses-specific RT-qPCR facilitates monitoring and prevention of alphaviruses

Molecular surveillance is vital for monitoring arboviruses, often employing genus-specific quantitative reverse-transcription polymerase chain reaction (RT-qPCR). Despite this, an overlooked chikungunya fever outbreak occurred in Yunnan province, China, in 2019 and false negatives are commonly encountered during alphaviruses screening practice, highlighting the need for improved detection methods. In this study, we developed an improved alphaviruses-specific RT-qPCR capable of detecting chikungunya virus, eastern equine encephalitis virus, western equine encephalitis virus, Venezuelan equine encephalitis virus, Sindbis virus, Mayaro virus, and Ross River virus with high sensitivity and specificity. The assay identified three chikungunya virus-positive cases out of 188 sera retrospectively. Later genetic characterization suggested that imported cases from neighboring countries may be responsible for the neglected chikungunya fever outbreak of 2019 in Yunnan. Our findings underscore the value of improved alphaviruses-specific RT-qPCR in bolstering alphaviruses surveillance and informing preventive strategies.

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).