Raging Epidemic
Infectious diseases, as one of the greatest enemies of the mankind in history, have been a serious threat to human health and social development, causing more deaths than the major wars collectively. Since the beginning of 2020, a sudden outbreak of COVID-19 has swept across China and the rest of the world, seriously threatening the lives and health of people, as well as the economy, around the world [1].
In the first half of 2021, the epidemic was brought under control and then mass vaccination started. However, the Delta variant of the SARS-CoV-2 appeared and began to spread rapidly around the world, setting off wave after wave of new outbreaks.
The vaccine currently in use around the world is much less effective in preventing the infection of the Delta variant strain than that of the original strain. Currently, the problem of inequitable distribution of COVID-19 vaccines is still prominent, and the numbers of infected cases in many countries are still rising [2]. As of September, 2021, there are more than 230 million confirmed cases of COVID-19 [3].
In addition, for the comprehensive development of our detection system, improving the specificity, sensitivity and simplicity of the detection is still essential. For this reason, we have also made efforts. We hope that any visitor can understand our conceptual process by browsing this page, and then initiate your own thinking.
Current Detection Methods & Current Problems
Novel coronavirus detection approaches mainly include antigen detection, antibody detection, nucleic acid detection and other methods.
However, the rate of antigen detection is low, and the preparation process is tedious and time-consuming, requiring the generation of recombinant antigen and monoclonal antibody, which takes about two to three months. Antibody detection may have false positive results, due to the presence of rheumatoid factor, heterophil sex antibody and autoantibody in individual patient blood, as well as medicaments and tumor cells, which may have cross reactions in the test. Nucleic acid test is currently the "gold standard" for the diagnosis of COVID-19, but the real-time fluorescent quantitative RT-PCR technology used in these tests requires advanced precise equipment or platforms. RT-PCR machines with high sensitivity are expensive, and requires high levels of laboratory cleanliness and professional operators. In addition, current nucleic acid test is time-consuming, and may take at least several hours to get the results [4].
Limitations of the Novel Coronavirus Test Method
| Antigen Detection | Antibody Detection | Nucleic Acid Detection |
|---|---|---|
| low detection rate, tedious preparation process, time-consuming | appearing false positive, easily affected by internal material interference | high technical requirements, time-consuming |
Our Plan
Based on the limitations of the above detection methods, we simulated and analyzed different detection methods by establishing a SEIR infectious disease model. Our goal was to determine how these limitations would individually affect the spread of the epidemic. We focus on the regions and countries that are less developed, and the results of our simulations are presented on the [Model] page.We concluded that increasing testing levels in all regions of the world was both effective and necessary to efficiently respond to potential future pandemics. Less developed countries and regions often do not have access to multiple tests to ensure efficient and reliable diagnoses. Therefore, we hope to propose a very broad-spectrum detection scheme: the G-quadruplex-based colorimetric virus detection system.
We employed the recombinase polymerase amplification technique to selectively amplify virus samples, and generated nicking and strand displacement using nickase and polymerase, respectively. The products of the strand displacement initiate the expansion of rolling ring to produce a large amount of G-quadruplex sequences [5]. The peroxidase activity of G-quadruplex makes it as a reporter of our detection system. It can catalyze the chromogenic reaction and allow us to visualize the visible discoloration. All reactions can be carried out at ambient temperatures with limited requirement of instrument, which allows the method to be used under all circumstances.
The outstanding advantages of our scheme include the sensitivity, specificity and convenience. Cascaded signal amplification was achieved by two isothermal amplifications to ensure sensitivity. Nicking and strand displacement can avoid false positives, which promotes its selectivity. The characteristic of G-quadruplex allows us to observe obvious color reaction to judge whether the object is infected or not under ordinary light conditions without any excitation of ultraviolet and other electrical equipment, which greatly improves the detection convenience. In addition, the design and development cycle of our program is fast. If a new epidemic occurs, we only need to change individual components and then put it into use immediately, which greatly improves the response speed of its uses in any area of an infectious disease, and saves time and material cost of testing. Therefore, as long as the nucleic acids of new pathogens are acquired, we can achieve rapid detection of them.
References
- Guo, Y et al. Zhonghua liu xing bing xue za zhi = Zhonghua liuxingbingxue zazhi vol. 41,5 (2020): 642-647. doi:10.3760/cma.j.cn112338-20200301-00222
- Rahman, Fahad Imtiaz et al. “The "Delta Plus" COVID-19 variant has evolved to become the next potential variant of concern: mutation history and measures of prevention.” Journal of basic and clinical physiology and pharmacology, 10.1515/jbcpp-2021-0251. 27 Sep. 2021, doi:10.1515/jbcpp-2021-0251
- Coronavirus disease (COVID-19) ( who.int) https://www.who.int/emergencies/diseases/novel-coronavirus-2019
- Majumder, Joydeb, and Tamara Minko. “Recent Developments on Therapeutic and Diagnostic Approaches for COVID-19.” The AAPS journal vol. 23,1 14. 5 Jan. 2021, doi:10.1208/s12248-020-00532-2
- Fay, Marta M et al. “RNA G-Quadruplexes in Biology: Principles and Molecular Mechanisms.” Journal of molecular biology vol. 429,14 (2017): 2127-2147. doi:10.1016/j.jmb.2017.05.017
