Advancements in Detection Approaches of Severe Acute Respiratory Syndrome Coronavirus 2

Abstract

Diagnostic testing to identify individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays a key role in selecting appropriate treatments, saving people's lives and preventing the global pandemic of COVID-19. By testing on a massive scale, some countries could successfully contain the disease spread. Since early viral detection may provide the best approach to curb the disease outbreak, the rapid and reliable detection of coronavirus (CoV) is therefore becoming increasingly important. Nucleic acid detection methods, especially real-time reverse transcription polymerase chain reaction (RT-PCR)-based assays are considered the gold standard for COVID-19 diagnostics. Some non-PCR-based molecular methods without thermocycler operation, such as isothermal nucleic acid amplification have been proved promising. Serologic immunoassays are also available. A variety of novel and improved methods based on biosensors, Clustered-Regularly Interspaced Short Palindromic Repeats (CRISPR) technology, lateral flow assay (LFA), microarray, aptamer etc. have also been developed. Several integrated, random-access, point-of-care (POC) molecular devices are rapidly emerging for quick and accurate detection of SARS-CoV-2 that can be used in the local hospitals and clinics. This review intends to summarize the currently available detection approaches of SARS-CoV-2, highlight gaps in existing diagnostic capacity, and propose potential solutions and thus may assist clinicians and researchers develop better technologies for rapid and authentic diagnosis of CoV infection.

Keywords: COVID-19; RT-qPCR; SARS-CoV-2; detection approach; nucleic acid.

Figure 1

Structural presentation of SARS-CoV-2 (A and B) and schematic diagram of its life cycle in host cells (C). (A) Four structural proteins of SARS-COV-2 are as follows: spike (S) surface glycoprotein (as purple colour); membrane (M) protein (as orange colour); nucleocapsid (N) protein (as blue colour); and envelope (E) protein (as green colour). Genomic RNA has been represented as encased in the N protein. (B) The arrangement of SARS-CoV-2 genome is in the following order: 5′-replicase (ORF1a/b)–structural proteins [S–E–M–N]–3′ (reprinted from Li et al. (11) with permission). (C) Life cycle starts after binding of S protein to the cellular receptor ACE2. Following receptor binding, the S protein undergoes conformational change thus facilitating viral envelope fusion with the cell membrane through the endosomal pathway. Then RNA is released from SARS-CoV-2 into the host cell. Genome RNA is translated into viral replicase polyproteins pp1a and 1ab, which are then cleaved into small products by viral proteinases. A series of sub genomic mRNAs is produced by the polymerase through transcription and finally they are translated into relevant viral proteins. The resultant viral proteins and genome RNA are subsequently assembled into virions in the ER and Golgi and then transported via vesicles to be released out of the cell. Notes: ACE2 = angiotensin-converting enzyme 2; ER = endoplasmic reticulum; ERGIC = ER–Golgi intermediate compartment [reprinted from Shereen et al. (17) with permission]

Figure 2

Schematic presentation of the RT-LAMP-VF assay: (A) Carrying out of RT-LAMP in a water bath maintaining constant temperature. (B) Detection of RT-LAMP products with a vertical flow visualisation strip [reprinted from Huang et al. (50) with permission]

Figure 3

(A) Schematic illustrations of CRISPR-COVID assay. The activation of collateral nuclease activity of Cas proteins occurs following specific binding of gRNA to the Orf1ab gene. Cleaved probes produce fluorescent signal which is then captured and thereby it indicates the presence of SARS-CoV-2 [reprinted from Hou et al. (66) with permission]. (B) Schematic presentation for RNA virus detection using Cas13 [reprinted from Freije et al. (76) with permission]