This diagram shows a labeled COVID 19 virus. 

Diagram of Virology of COVID 19 virus

The spike glycoprotein (S) is responsible for attachment between the virus and a cell-surface receptor, leading to the fusion of virus to the cell membrane. This membrane-fusion activity can only occur with the proteolytic cleavage of the S glycoprotein into S1 and S2 subunits, which continue to remain associated with one another after cleavage. 


Spike glycoprotein (S)

Accessory proteins play important roles as virulence factors affecting pathogenicity, release, and stability of SARS-CoV2 and aid in infection, replication, and transmission of the virus between individuals. The SARS-CoV2 accessory proteins are 3a, 3b, p6, 7a, 7b, 8b, 9b, and ORF14.

Accessory Proteins of SARS-CoV2

The nucleocapsid protein (N) is bound to the viral RNA within a coronavirus particle. The N protein plays important roles in viral transcription and replication, which are parts of the viral life cycle. 

Nucleocapsid protein (N)

SARS-CoV-2 is comprised of four main structural components: the spike glycoprotein (S), the small envelope glycoprotein (E), the membrane glycoprotein (M), and the nucleocapsid protein (N). There are also several accesory proteins. 

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- Animal Studies on SARS-CoV-2 Virology
- Antigen Detection
- Classification
- Evolution and Mutations
- Methods of Host Cell Infection and Exploitation
- Stability in different environmental conditions
- Structure
- Vaccine Candidates, Immunogenicity, and Adaptive Immunity
- Reinfection

Focuses of Virology of COVID-19

Astuti, I, & Ysrafil. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): An overview of viral structure and host response. Diabetes & Metabolic Syndrome: Clinical Research & Reviews. 2020. doi:10.1016/j.dsx.2020.04.020
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7165108/#:~:text=Structurally%2C%20SARS%2DCoV%2D2,several%20accessory%20proteins%20%5B9%5D.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): An overview of viral structure and host response

Structure of SARS-CoV-2

- Manipulation of Innate Immune and Pro-inflammatory Response

Methods of Host Cell Infection and Exploitation

A study found that SARS-CoV-2 can be highly sensitive to heat. The virus was still detectable after being left out for 14 days in a 4°C room, while the virus inactive 5 minutes after being left in a 70°C. The study also found a difference in stability on different surfaces, such as paper, plastic, and metal.  At room temperature, the virus is highly stable in a range of pH3 - pH10. However, the standard disinfectant method was still able to affect the virus, with the researchers finding no active infection in different disinfectants after an incubation of 5 minutes (except for hand soap).

Stability of SARS-CoV-2 in different environmental conditions

Investigations are still ongoing in determining the current evolution and mutating nature of SARS-CoV-2, which will aid scientists in understanding more about this virus and in developing effective treatments and vaccines against the disease. 

Evolution and Mutations of SARS-CoV-2

- Application of Rhesus Macaques for Studying SARS-CoV-2 Virology
- Application of Syrian Hamsters for Studying SARS-CoV-2 Virology
- Application of Mosquitoes for Studying SARS-CoV-2 Virology
- Application of African Green Monkeys for Studying SARS-CoV-2 Virology

Animal Studies on SARS-CoV-2 Virology

So far, vaccines consist of either inactivated or weakened versions of antigens or virions. Many pharmaceutical companies like Pfizer and Moderna are developing inactivated antigens in the form of mRNA, DNA, and proteins from the viral envelope or capsid that are often fragmented. 

Vaccine Candidates, Immunogenicity, and Adaptive Immunity

Until vaccine has passed all preclinical and clinical trials as well as FDA approval, the best approach to containing the pathogenicity and infectivity of COVID-19 will involve testing. The Safra center at Harvard advised to have up to 5 million tests being conducted within a day. Testing will not only slow down the spread, but also allow reopening of businesses and schools. So far, many testing methods involve viral RNAs or antigens. For detecting viral RNAs, most involve using RT-qPCR conjugated with Next Generation Sequencing to identify specific unique viral sequences. Recently, SHERLOCK detection technique utilizing CRISPR-Cas13 was tested in Broad Institute using a catalytically dead Cas13 to bind to specific viral sequences. On the other hand, detection of viral antigens involve either using ELISA with selected antibodies against viral antigens or using lateral flow assay.

Antigen Detection

Until August 28, 2020, there has been several cases of reinfections around the world (Hong Kong, Belgium, the Netherlands, and the US). 

Reinfection of SARS-CoV-2

The coronaviruses belong to the broad viral order Nidovirales within the family, Coronaviridae, notoriously known to be infecting mammals and humans in the recent years. In general, they can be commonly distinguished by their unique morphological structures of spherical or disk-like envelopes embedded with glycoproteins (Burrell et al., 2017). In terms of its genetic composition, it has a large positive sense RNA (33.5 kb) belonging to Group VI in the Baltimore classification. Other shared similarities include highly conserved genomes, Replicase gene upstream of structural and accessory genes as well as the translation of many nonstructural mRNAs from ribosomal frameshift. These viruses are very diverse and can be further subdivided into 4 subfamilies: alpha-, beta-, delta-, and gamma-coronaviruses based on serology (Fehr et al., 2015). 

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