Optimization and validation of RT-LAMP assay for diagnosis of SARS-CoV2 including the globally dominant Delta variant

Engineered two-dimensional nanomaterials based diagnostics integrated with internet of medical things (IoMT) for COVID-19

More than four years have passed since an inimitable coronavirus disease (COVID-19) pandemic hit the globe in 2019 after an uncontrolled transmission of the severe acute respiratory syndrome (SARS-CoV-2) infection. The occurrence of this highly contagious respiratory infectious disease led to chaos and mortality all over the world. The peak paradigm shift of the researchers was inclined towards the accurate and rapid detection of diseases. Since 2019, there has been a boost in the diagnostics of COVID-19 via numerous conventional diagnostic tools like RT-PCR, ELISA, etc., and advanced biosensing kits like LFIA, etc. For the same reason, the use of nanotechnology and two-dimensional nanomaterials (2DNMs) has aided in the fabrication of efficient diagnostic tools to combat COVID-19. This article discusses the engineering techniques utilized for fabricating chemically active E2DNMs that are exceptionally thin and irregular. The techniques encompass the introduction of heteroatoms, intercalation of ions, and the design of strain and defects. E2DNMs possess unique characteristics, including a substantial surface area and controllable electrical, optical, and bioactive properties. These characteristics enable the development of sophisticated diagnostic platforms for real-time biosensors with exceptional sensitivity in detecting SARS-CoV-2. Integrating the Internet of Medical Things (IoMT) with these E2DNMs-based advanced diagnostics has led to the development of portable, real-time, scalable, more accurate, and cost-effective SARS-CoV-2 diagnostic platforms. These diagnostic platforms have the potential to revolutionize SARS-CoV-2 diagnosis by making it faster, easier, and more accessible to people worldwide, thus making them ideal for resource-limited settings. These advanced IoMT diagnostic platforms may help with combating SARS-CoV-2 as well as tracking and predicting the spread of future pandemics, ultimately saving lives and mitigating their impact on global health systems.

Advanced technologies towards improved HPV diagnostics

Persistent infection with high-risk types of human papillomaviruses (HPV) is a major cause of cervical cancer, and an important factor in other malignancies, for example, head and neck cancer. Despite recent progress in screening and vaccination, the incidence and mortality are still relatively high, especially in low-income countries. The mortality and financial burden associated with the treatment could be decreased if a simple, rapid, and inexpensive technology for HPV testing becomes available, targeting individuals for further monitoring with increased risk of developing cancer. Commercial HPV tests available in the market are often relatively expensive, time-consuming, and require sophisticated instrumentation, which limits their more widespread utilization. To address these challenges, novel technologies are being implemented also for HPV diagnostics that include for example, isothermal amplification techniques, lateral flow assays, CRISPR-Cas-based systems, as well as microfluidics, paperfluidics and lab-on-a-chip devices, ideal for point-of-care testing in decentralized settings. In this review, we first evaluate current commercial HPV tests, followed by a description of advanced technologies, explanation of their principles, critical evaluation of their strengths and weaknesses, and suggestions for their possible implementation into medical diagnostics.

Reverse transcription loop‑mediated isothermal amplification has a high performance in the detection of SARS‑CoV‑2 in saliva samples and nasal swabs from asymptomatic and symptomatic individuals

The detection of coronavirus disease 2019 cases represents a significant challenge at the epidemiological level. Limitations exist in effectively detecting asymptomatic cases, achieving good follow-up in hospitals without the infrastructure for reverse transcription-quantitative PCR (RT-qPCR) or in difficult-to-access areas and developing methods with the need for less invasive sampling procedures. Therefore, the present study evaluated the performance of the direct reverse transcription loop-mediated isothermal amplification (RT-LAMP) test for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the saliva and nasal samples of asymptomatic individuals belonging to the university population. In addition, this test was also assessed for effectiveness in symptomatic individuals referred from a hospital with poor infrastructure in molecular biology and located outside the urban area. The RT-LAMP assay was compared with the results obtained from the RT-qPCR nasopharyngeal swab test, where the diagnosis was confirmed by lateral flow immunoassay test for rapid antigen detection. A total of 128 samples were analyzed, of which 43% were symptomatic positive individuals, 25% were asymptomatic positive individuals and 32% were SARS-CoV2-negative control individuals. Among positive individuals, no differences were found between the Cq values determined by RT-qPCR. A sensitivity of 96.5% and a specificity of 97.6% was reported for the detection of SARS-CoV-2 in symptomatic individuals by salivary and nasal RT-LAMP, as well as a sensitivity of 100% and a specificity of 97.6% for the detection of SARS-CoV-2 in asymptomatic individuals. These findings indicated that performance of the direct RT-LAMP test using saliva and nasal samples has high sensitivity and specificity, which in turn suggest that it is a viable and reliable alternative for use in epidemiological monitoring.

Development of loop-mediated isothermal amplification (LAMP) assays using five primers reduces the false-positive rate in COVID-19 diagnosis

The reverse-transcription loop-mediated isothermal amplification (RT-LAMP) is a cheaper and faster testing alternative for detecting SARS-CoV-2. However, a high false-positive rate due to misamplification is one of the major limitations. To overcome misamplifications, we developed colorimetric and fluorometric RT-LAMP assays using five LAMP primers, instead of six. The gold-standard RT-PCR technique verified the assays' performance. Compared to other primer sets with six primers (N, S, and RdRp), the E-ID1 primer set, including five primers, performed superbly on both colorimetric and fluorometric assays. The sensitivity of colorimetric and fluorometric assays was 89.5% and 92.2%, respectively, with a limit of detection of 20 copies/µL. The colorimetric RT-LAMP had a specificity of 97.2% and an accuracy of 94.5%, while the fluorometric RT-LAMP obtained 99% and 96.7%, respectively. No misamplification was evident even after 120 min, which is crucial for the success of this technique. These findings are important to support the use of RT-LAMP in the healthcare systems in fighting COVID-19.

Rapid, sensitive, and specific detection of SARS-CoV-2 in nasopharyngeal swab samples of suspected patients using a novel one-step loop-mediated isothermal amplification (one-step LAMP) technique

BACKGROUND

In the absence of effective antiviral drugs or vaccines, early and accurate detection of SARS-CoV-2 infection is essential to the COVID-19 pandemic. This study developed and evaluated a novel rapid One-Step LAMP assay to directly detect the SARS-CoV-2 RNA from nasopharyngeal (NP) swab samples of patients with suspected SARS-CoV-2 infection living in deprived areas in comparison to One-Step Real-time PCR.

METHODS

Two hundred fifty-four NP swab samples from patients suspected of COVID-19 infection living in deprived western areas of Iran were tested by TaqMan One-Step RT-qPCR and fast One-Step LAMP assays. Tenfold serial dilutions of SARS-CoV-2 RNA standard strain where the viral copy number in each dilution was previously determined using the qPCR and various templates were used to investigate the analytical sensitivity and specificity of the One-Step LAMP assay in triplicate. Also, the efficacy and reliability of the method compared to TaqMan One-Step RT-qPCR were evaluated using SARS-CoV-2 positive and negative clinical samples.

RESULTS

The results of the One-Step RT-qPCR and One-Step LAMP tests were positive in 131 (51.6%) and 127 (50%) participants, respectively. Based on Cohen's kappa coefficient (κ), the agreement between the two tests was 97%, which was statistically significant (P < 0.001). The detection limit for the One-Step LAMP assay was 1 × 10¹ copies of standard SARS-CoV-2 RNA per reaction in less than an hour in triplicates. Negative results in all samples with non-SARS-CoV-2 templates represent 100% specificity.

CONCLUSIONS

The results showed that the One-Step LAMP assay is an efficient consistent technique for detecting SARS-CoV-2 among suspected individuals due to its simplicity, speed, low cost, sensitivity, and specificity. Therefore, it has great potential as a useful diagnostic tool for disease epidemic control, timely treatment, and public health protection, especially in poor and underdeveloped countries.

RT-LAMP Multicenter Study for SARS-CoV-2 Genome Molecular Detection in Brazilian Swab and Saliva Samples

Reverse transcription loop-mediated isothermal amplification (RT-LAMP) is a rapid method that can replace RT-qPCR. A simple molecular assay for SARS-CoV-2 RNA detection in gold-standard diagnosis through swabs and alternative specimens such as saliva could be helpful in promoting genomic surveillance. A multicenter study was conducted to evaluate the RT-LAMP assay method as an alternative for the molecular detection of SARS-CoV-2 lineages in swab and saliva samples. A total of 350 swabs from individuals with (n = 276) or without (n = 74) COVID-19 tested by RT-qPCR were collected. Paired saliva was also collected from 90 individuals who had SARS-CoV-2 RNA that was detectable (n = 30) or undetectable (n = 60) via RT-qPCR. For the RT-LAMP methodology, six primers were used for ORF1 gene amplification. As for SARS-CoV-2 genotyping, 39 swabs had the whole genome sequenced by MinION. The sensitivity of RT-LAMP to the swab was 90.2%. For the swab samples with Ct ≤ 30, the sensitivity improved by 96%. Considering saliva with Ct ≤ 30 in RT-qPCR testing, the RT-LAMP sensitivity was 100%. The RT-LAMP specificity was 100% for both the swab and saliva samples. This RT-LAMP assay was capable of detecting all the SARS-CoV-2 lineages circulating in the Brazilian swab samples. The RT-LAMP method has significant potential for use in clinical routines since it was capable of detecting SARS-CoV-2 RNA in swab and saliva samples.

The Future of Point-of-Care Nucleic Acid Amplification Diagnostics after COVID-19: Time to Walk the Walk

Since the onset of the COVID-19 pandemic, over 610 million cases have been diagnosed and it has caused over 6.5 million deaths worldwide. The crisis has forced the scientific community to develop tools for disease control and management at a pace never seen before. The control of the pandemic heavily relies in the use of fast and accurate diagnostics, that allow testing at a large scale. The gold standard diagnosis of viral infections is the RT-qPCR. Although it provides consistent and reliable results, it is hampered by its limited throughput and technical requirements. Here, we discuss the main approaches to rapid and point-of-care diagnostics based on RT-qPCR and isothermal amplification diagnostics. We describe the main COVID-19 molecular diagnostic tests approved for self-testing at home or for point-of-care testing and compare the available options. We define the influence of specimen selection and processing, the clinical validation, result readout improvement strategies, the combination with CRISPR-based detection and the diagnostic challenge posed by SARS-CoV-2 variants for different isothermal amplification techniques, with a particular focus on LAMP and recombinase polymerase amplification (RPA). Finally, we try to shed light on the effect the improvement in molecular diagnostics during the COVID-19 pandemic could have in the future of other infectious diseases.

Accurate identification of SARS-CoV-2 variant delta using graphene/CRISPR-dCas9 electrochemical biosensor

Delta (B.1.617.2), a highly infectious variant of SARS-CoV-2, has been sweeping the world, and threatening the safety of human life seriously. It is urgent to develop a highly selective and sensitive assay to accurately identify the SARS-CoV-2 variant Delta. In this work, we constructed a graphene/CRISPR-dCas9 electrochemical biosensor to accurately identify SARS-CoV-2 variant Delta, where the signal was further amplified by embedded electrochemical probe [Ru(phen)₂dppz]BF₄. This detection assay could be finished within 47 min totally, with the detection limit of 1.2 pM and good reproducibility with a C·V.% of 2.48% (n = 5). And the biosensor could selectively identify Delta among SARS-CoV-2 and other variants, including Alpha, Beta, Gamma. This assay was further validated by 26 real clinical samples, showing 100% clinical sensitivity and 100% clinical specificity, which provides a new direction for identifying other SARS-CoV-2 variants in the future.

Rapid and convenient detection of SARS-CoV-2 using a colorimetric triple-target reverse transcription loop-mediated isothermal amplification method

Coronavirus Disease 2019 (COVID-19) caused by SARS-CoV-2 poses a significant threat to global public health. Early detection with reliable, fast, and simple assays is crucial to contain the spread of SARS-CoV-2. The real-time reverse transcription-polymerase chain reaction (RT-PCR) assay is currently the gold standard for SARS-CoV-2 detection; however, the reverse transcription loop-mediated isothermal amplification method (RT-LAMP) assay may allow for faster, simpler and cheaper screening of SARS-CoV-2. In this study, the triple-target RT-LAMP assay was first established to simultaneously detect three different target regions (ORF1ab, N and E genes) of SARS-CoV-2. The results revealed that the developed triplex RT-LAMP assay was able to detect down to 11 copies of SARS-CoV-2 RNA per 25 µL reaction, with greater sensitivity than singleplex or duplex RT-LAMP assays. Moreover, two different indicators, hydroxy naphthol blue (HNB) and cresol red, were studied in the colorimetric RT-LAMP assay; our results suggest that both indicators are suitable for RT-LAMP reactions with an obvious color change. In conclusion, our developed triplex colorimetric RT-LAMP assay may be useful for the screening of COVID-19 cases in limited-resource areas.

RT-PCR and Matrix-Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry Diagnostic Target Performance Reflects Circulating Severe Acute Respiratory Syndrome Coronavirus 2 Variant Diversity in New York City

As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to circulate, multiple variants of concern have emerged. New variants pose challenges for diagnostic platforms because sequence diversity can alter primer/probe-binding sites (PBSs), causing false-negative results. The Agena MassARRAY SARS-CoV-2 Panel (Agena Bioscience) uses RT-PCR and mass spectrometry to detect five multiplex targets across N and ORF1ab genes. Herein, we use a data set of 256 SARS-CoV-2-positive specimens collected between April 11, 2021, and August 28, 2021, to evaluate target performance with paired sequencing data. During this time frame, two targets in the N gene (N2 and N3) were subject to the greatest sequence diversity. In specimens with N3 dropout, 69% harbored the Alpha-specific A28095U polymorphism that introduces a 3'-mismatch to the N3 forward PBS and increases risk of target dropout relative to specimens with 28095A (relative risk, 20.02; 95% CI, 11.36 to 35.72; P < 0.0001). Furthermore, among specimens with N2 dropout, 90% harbored the Delta-specific G28916U polymorphism that creates a 3'-mismatch to the N2 probe PBS and increases target dropout risk (relative risk, 11.92; 95% CI, 8.17 to 14.06; P < 0.0001). These findings highlight the robust capability of Agena MassARRAY SARS-CoV-2 Panel target results to reveal circulating virus diversity, and they underscore the power of multitarget design to capture variants of concern.

Genome sequencing of SARS-CoV-2 reveals the prevalence of variant B 1.1.7 in Egypt

Recently, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) resulted in Coronavirus Disease 2019 (COVID-19) outbreak. A new SARS-CoV-2 strain is expected to emerge in late 2020, including B.1.1.7. The high transmission rate of SARS-CoV-2 B.1.1.7 has raised public health concerns in several countries. Hence, in this study, we assessed the sequencing of SARS-COV2 to reveals the prevalence of the SARS-CoV-2 Alpha variant (B 1.1.7) in Egypt. We found that the viral transmission of the alpha variant is expanding. Moreover, based on hospitalizations and case fatality rates, there is a potential for increasing severity. There was no effect on susceptibility to Emergency Use Authorization monoclonal antibody treatments. However, there was minimal impact on neutralization by convalescent and post-vaccination sera. Samples have been clustered into the 20D sub clade for the majority of them. The eight samples shown in our study are considered the first recorded samples with the Alpha variant in Egypt. Therefore, The Egyptian government, represented by the Ministry of Health, must take all measures to examine the compatibility of the currently used vaccines with this new strain and the feasibility of the treatment protocol presently used with such strains developed in the Arab Republic of Egypt.