Huajun Bai1 Xiaolong Cai1, 2*  Xiaoyan Zhang1
1. R&D Center, GeneMedi Co.Ltd., Shanghai, P.R. China (
2. Hanbio Research Center, Hanbio Tech Co. Ltd., Shanghai, P.R. China (

The outbreak of COVID-19, caused by 2019 novel coronavirus (2019-nCoV), has been a global public health threat and caught the worldwide concern. Scientists throughout the world are sparing all efforts to explore strategies for the determination of the 2019-nCoV virus and diagnosis of COVID-19 rapidly. Several assays are developed for COVID-19 test , including RT-PCR, coronavirus antigens-based immunoassays, and CRISPR-based strategies (Cas13a or Cas12a), etc. Different assays have their advantages and drawbacks, and people should choose the most suitable assay according to their demands. Here, we make a brief introduction about these assays and give a simple overview of them, hoping to help doctors and researchers to select the most suitable assay for the Coronavirus Disease 2019 test (COVID-19 test) .

Background of Coronavirus Disease 2019 (COVID-19, 2019-nCoV)

In Dec of 2019, one kind of novel viral pneumonia broke out in Wuhan of China and aroused worldwide concern. This virus was temporarily named as 2019 novel coronavirus (2019-nCoV) by the World Health Organization (WHO) on Jan 7th 2020 [1]. Then, this virus was re-termed as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) based on its sequence similarity to that of 2002-2003 SARS, and the disease it caused was called Coronavirus Disease 2019 (COVID-19) by WHO on Jan 12th, 2020.

SARS-CoV-2 is 60~200nm in diameter and encapsidates a large single-stranded RNA virus (26-32kb) with many spikes on the virus capsid (Fig. 1A). Several characteristic genes typical for coronaviruses (ORF) are observed in the genomes of SARS-CoV (Fig. 1B), such as spike (S), envelope (E), and nucleocapsid (N). Among them, the receptor-binding domain (RBD) of Spike subunit 1 (S1) is indispensable for the viral infection. To date, the mechanisms about how SARS-CoV transduces human cells have not been completely elucidated yet. Whereas a report shows SARS-CoV 2 infects human with similar processes to SARS by binding to the angiotensin-converting enzyme 2 (ACE2) receptor of target cells [2-4], such as respiratory epithelial cells. Once humans are infected with SARS-CoV-2, they will have the following symptoms: ① having fever and feeling fatigue systematically; ② sneezing, runny nose, sore throat, dry cough, and shortness of breath  in the respiratory system; ③ diseased function in kidney; ④ diarrhea in intestines; ⑤ deceased white blood cells.

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Figure 1. SARS-CoV-2 capsid structure and genome map. (A) Three-dimensional structure diagram of SARS-CoV-2. (B) Genome organization of SARS-CoV-2 [5]. ORF: open reading frame. E: envelope. M: membrane. N: nucleocapsid. HR1: heptad repeat 1. HR2: heptad repeat 2. SP: signal peptide. NTD: N-terminal domain. RBD: receptor binding domain. S: spike. S1: subunit 1. S2: subunit 2. TM: transmembrane domain.

It has been reported that person-to-person transmission from infected COVID-19 patients is really rapidly [5-7]. Although China government is basically in control of COVID-19 pathophoresis by separating patients from normal, forcing citizens to wear masks, and controlling traffic, now the viral pneumonia is globally threatening the health of people all over the world, especially in Europe and North America. Since no specific therapeutic drugs or vaccines are available for patients with COVID-19, it is really necessary and noteworthy to determine whether the patient is infected early and separate the infected patients from the healthy population immediately to avoid the widespread of SARS-CoV-2. To date, there are several strategies for COVID-19 test: ① real-time PCR (RT-PCR) method; ② immunoassay; ③ Crispr-Cas13a (SHERLOCK)-based test.


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Collection of COVID-19 landscape knowledge base

Viral vector-based vaccine; DNA-based vaccine; RNA based vaccine - A landscape for vaccine technology against infectious disease, COVID-19 and tumor.

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