The SARS-CoV-2 virus

The causative agent of the ongoing pandemic, the SARS-CoV-2, is a viral particle with a diameter between 50–200 nanometers and a simple architecture consisting essentially of four structural proteins. The nucleocapsid (N) protein holds the viral RNA together inside the particle. The spike protein (S), envelope (E), and membrane (M) proteins form the viral envelope that protects the genetic material (Chang et al., 2014). Currently, most COVID-19 testing is performed using viral RNA extraction followed by RT-qPCR to amplify the genes of some of the above-mentioned proteins (Chu et al., 2020; Corman et al., 2020).


February 23, 2021
Viruses are non-living particles containing genetic information in the form of DNA or RNA. They are fascinating because they are not considered a form of life even though they evolve in the same way all living organisms do. Viruses are so-called obligate pathogens because they cannot multiply unless they infect and hijack the cellular machinery in living organisms.
The causative agent of the ongoing pandemic, the SARS-CoV-2, is a viral particle with a diameter between 50-200 nanometers and a simple architecture consisting essentially of four structural proteins. The nucleocapsid (N) protein holds the viral RNA together inside the particle. The spike protein (S), envelope (E), and membrane (M) proteins form the viral envelope that protects the genetic material (Chang et al., 2014). Currently, most COVID-19 testing is performed using viral RNA extraction followed by RT-qPCR to amplify the genes of some of the above-mentioned proteins (Chu et al., 2020;Corman et al., 2020). Different mechanisms allow viruses to enter our cells. By mimicking host molecules, viruses gain entry into cells and evade the immune response. The S-protein of SARS-CoV-2 can bind to the human angiotensinconverting enzyme 2 (ACE2) by wearing the disguise of a particular epithelial sodium channel (ENaC-α) in humans (Yan et al., 2020;Lan et al., 2020). To exert its function, ENaC-α binds to ACE2 and is recognized and cut by a specialized protein called transmembrane protease serine 2 (TMPRSS2). The site at which TMPRSS2 cuts ENaC-α is identical to a small part of the S-protein of SARS-CoV-2. Given the high structural similarity between the S-protein and our own ENaC-α, both the ACE2 and TMPRSS2 cannot discriminate between the virus and our molecules and allows viral particles to enter our cells (Anand et al., 2020;Vkovski et al., 2020).
Once inside our cells, the viral particle disassembles and releases its RNA. The viral RNA serves as a manual for our ribosomes to produce the components required to generate more viral particles. The first viral protein that our cells synthesize is called replicase, and it makes thousands of copies of the viral RNA. These thousands of viral RNA copies are used to produce more viral components and assemble thousands of new viral particles that will be released by the infected cell upon its death. The newly generated viruses are ready to infect thousands of cells and start a new cycle of infection, replication, and dissemination (El País -Así infecta el coronavirus, 2020; COVID-19 Animation, n.d.).
A potential therapy against SARS-CoV-2 could aim at interfering with the binding of the S-protein to ACE2, thereby preventing the virus from entering our cells. This could be achieved by designing small peptides that can bind to the S-protein. During an active SARS-CoV-2 infection, these small peptides would bind the viral particle hiding the part of the S-protein that interacts with ACE2, effectively limiting the number of infected cells and slowing down the infection.
Although SARS-CoV-2 initially infects the respiratory tract, and lung cells, the ACE2 protein is expressed by cells from the heart, kidneys, and intestine. COVID-19 was initially described as a respiratory disease. However, as we advanced our knowledge of the virus's fundamental interactions with our cells, we learned that this disease affects multiple organs and cell types. To develop efficient therapies and vaccines against SARS-CoV-2, we need to better understand the origins of the virus, characterize the structure of its proteins and the function of its genes, and deepen our understanding of how it affects us. Drawing a clear and comprehensive picture of SARS-CoV-2 will reveal its strengths and weaknesses and provide us with the information needed to design effective therapies in the future. On the other hand, as a result of many years of fundamental research, some of the new vaccines against COVID-19 are showing impressive efficacy and are helping to control the current pandemic. Therefore, supporting fundamental research remains crucial for granting scientific progress in the future.