We are a group of scientists from the Biochemistry department at Lund University, Sweden. We are interested in understanding structure and function of different biological molecules including viruses. Currently we are holding journal reading clubs where we try to learn more about SARS-CoV-2 virus, or the "new corona virus". As scientists we have capability and responsibility to analytically read, discuss and share our thoughts with a broader audience and we therefore created this webpage and we plan to update regularly. We will do our best in understanding and interpreting results from scientific papers we read. However we cannot have a full insight into quality of performed research. When one tries to summarize the information from scientific literature, it is not always possible to include all details and the authors conclusions might be misinterpret. We hope that this resource can answer some questions related to coronaviruses, and explain the scientific literature that we have read so that those of you who are not scientists can get some of the information that they supply.. We will format this page in question and answers schemes and we will always provide reference to the original source.
Q1: What is coronavirus?
A1: Coronaviridae is a family of viruses that cause disease in humans or other animals. Coronaviruses cause a range of diseases from common colds to Severe Acute Respiratory Syndrome (SARS) and Covid-19. Like other viruses the coronaviruses need to hijack host cells from another organism in order to replicate. The virus particles need a way to enter the cells of the host and then the host cell is used to replicate the viral genome and produce more virus particles. Coronaviruses are so called enveloped viruses. Their core which contains their genetic material, RNA, is surrounded by a lipid membrane held together by envelope proteins. On the surface, the coronaviruses have a protein called the spike protein which they use to recognize and bind to host organism cells in order to penetrate the cells and use their machinery to replicate.(https://www.immunology.org/public-information/bitesized-immunology/pathogens-and-disease/virus-replication) (https://mmbr.asm.org/content/62/4/1171), (https://virologyj.biomedcentral.com/articles/10.1186/s12985-019-1182-0)
Q2: How many corona viruses haven been discovered?
A2: Many coronaviruses have been discovered, the family Coronaviridae contains 3500 species that scientists have sequenced the complete genome of. The most known coronaviruses are the variants that have caused recent epidemics. Severe Acute Respiratory Syndrome (SARS) spread to several countries in 2002-2003 was caused by the virus called SARS-CoV, Middle Eastern Respiratory Syndrom (MERS) spread in 2012 was caused by the virus MERS-CoV. The current pandemic of Covid-19 is caused by the virus SARS-CoV-2.(https://www.viprbrc.org/brc/home.spg?decorator=corona)
Q3: What is the origin of human coronaviruses MERS-CoV, SARS-CoV and SARS-CoV-2 (Covid-19 virus)?
A3: Human coronaviruses MERS-CoV and SARS-CoV originates from bats and were transmitted to humans via camels and civets. Other human coronaviruses have originated from bats or rodents and have been transmitted through intermediate organisms to humans. The "new coronavirus" SARS-CoV-2 we don't yet know the origin of but it has been found that it has great similarity with a variant that is found in bats. We also don't know if there is other intermediate organisms involved in transmission to humans. (https://www.nature.com/articles/s41579-018-0118-9er) (https://www.nature.com/articles/s41586-020-2179-y) (https://www.ncbi.nlm.nih.gov/pubmed/20567988)
Q4: Does SARS-CoV-2 require intermediate organism?
A4:
Q5: Why do so many viruses that cause epidemics originate in bats?
A5: Bats are known for hosting a wide variety of viruses, including the corona viruses. The bats seem to not be very affected by the infection by these viruses. The reason why the bats are not as sick from these viruses as us humans is suggested to be that they have evolved a different strategy for virus control. While lacking some components in the immune system, bats increase their body temperature when they fly and they have an increased metabolism. This helps them to stay healthy while the viruses can evolve in the bat population. When the virus spills over to other mammals or humans, the new host is not prepared for fighting the virus since they lack the mechanism that bats have. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4012789/)
Q6: How does the SARS-CoV-2 recognize human cells?
A6: SARS-CoV-2 and SARS-CoV uses its receptor binding domain (part of a spike protein on the surface of the virus) to bind a human enzyme (ACE2), through a tightly controlled structural interface. ACE2 is an enzyme that has a role in regulation of blood pressure. It is located on the outside of the cell membrane in eg. lung epithelial cells. Binding of the virus spike protein to ACE2 on a cell facilitates the entry of the virus into the cell. SARS-CoV-2 have a few mutations in the receptor binding domain compared to SARS-CoV but they bind to and recognize human cells at the same receptor, ACE2. (https://onlinelibrary.wiley.com/doi/full/10.1002/path.1570) (https://www.nature.com/articles/s41586-020-2179-y) (https://www.ncbi.nlm.nih.gov/pubmed/20567988)
Q7: Is SARS-CoV-2 more efficent in recognizing human cells compare to SARS-CoV?
A7:
Q8: How many protein are encoded in virus genome and what do they do?
A8:T he RNA genome of SARS-CoV-2 has 29,811 nucleotides and encodes 29 proteins (though one may not get expressed). These proteins carry out a range of jobs from making copies of the coronavirus to suppressing the body’s immune responses. Of the 29 SARS-CoV-2 proteins, four make up the virus’s actual structure, including the S protein. One group of the other 25 coronavirus proteins regulates how the virus assembles copies of itself and how it sneaks past the host immune system. These so-called nonstructural proteins are expressed as two huge polyproteins that are then cleaved into 16 smaller proteins. An enzyme called the main protease, which performs 11 of those cleavages, is also a highly promising drug target. https://www.nature.com/articles/s41586-020-2008-3, https://www.nytimes.com/interactive/2020/04/03/science/coronavirus-genome-bad-news-wrapped-in-protein.html, https://www.biorxiv.org/content/10.1101/2020.03.12.988865v2.full.pdf
Q9: What are potential antiviral therapies?
A9
Q10: Why do we observe outbreak of coronaviruses in XXI century?
A10: "It is widely accepted that many viruses have existed intheir natural reservoirs for a very long time. The constant spillover of viruses from natural hosts to humans and other animals is largely due to human activities, including modern agricultural practices and urbanization. Therefore, the most effective way to prevent viral zoonosis is to maintain the barriers between natural reservoirs and human society, in mind of the ‘one health’ concept." (https://www.ncbi.nlm.nih.gov/pubmed/20567988)