This post specifically pertains to the known science of the Wuhan virus/coronavirus.
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| Credit: CDC/ Alissa Eckert, MS; Dan Higgins, MAM. |
COVID-19(Coronavirus disease -2019), needs no introduction (obviously..!), corona viruses is a group of viruses that causes different types of diseases in different kinds of mammals and birds(In Humans it causes respiratory tract infections, and in cows and pigs it causes diarrhoea and so forth). COVID-19 is named by WHO chief in February-2020 after the disease-causing virus, SARS-CoV-2(severe acute respiratory syndrome-coronavirus-2, priorly known as 2019 novel coronavirus(2019 nCoV)). SARS-CoV-2 has a close genetic similarity to that of bats coronaviruses, and hence it is hypothesised that it may originate and spread from bats.
Under a cryo-electron microscope, this contagious virus looks like
Representative image.Credit:Reuters photo
Using the psyche of scientists and advanced computer simulations made the above to look like
This virus spreads through the aerosolised particles expelled while coughing and sneezing from an infected person to others
Inside the coronavirion, there is a nucleocapsid protein which encloses required RNA to cause a pandemic. The complete RNA sequence is found by the Chinese scientists and uploaded to a free public database (https://www.ncbi.nlm.nih.gov/genbank/sars-cov-2-seqs/) such that it would be easy to find a vaccine rather spending time on finding its RNA sequence. SARS-CoV-19 is completely RNA type virus.RNA viruses infect cells by injecting RNA into the cytoplasm of the host cells to transcribe and replicate viral proteins. The genome size of coronaviruses ranges from approximately 27 to 34 kilobases, the largest among known RNA viruses.
And next comes the lipid membrane which contains two layers of neatly packed lipids with the hydrophobic ends towards the middle of the membrane and hydrophilic ends towards the edges of the membrane.
At least this membrane is helping us to protect from the CoVID-19 disease(how and why will be explained in a while)
Attached to this lipid membrane there are three types of glycoproteins(which contains C-terminal and N-terminal) namely envelope protein, membrane protein and the most important one, The spike protein is the one which binds to certain unknown specific surface receptors in the plasma membrane of host cell via N-terminus and without this protein the virion losses its contour and will not be able to enter the host cells.
The membrane protein gets glycosylated(the enzymatic process that attaches glycans to proteins) in the Golgi apparatus. This protein helps the virion to regenerate in the host cell by the complex formation in the ERGIC(endoplasmic reticulum-Golgi apparatus intermediate compartment).
The envelope protein is the smallest of three, comprising 75-110 amino acids. Also, this protein plays a critical role in morphogenesis and assembly of the virions in the host cell
CoVID-19 COURSE
Now getting on to the trajectory of the virus
Firstly, it immigrates into the host mainly through the nose (it also enters through eyes and mouth), it attaches to a particular receptor on the surface of a body's cell, usually starting with cells in the mucus membranes in nose and throat, causing mild cough and cold, and to cells in the lungs (mucus and hair like batons called cilia) with the help of the spike protein by endocytosis process which is dependent on pH. On entering the cytoplasm of the cells, it disassembles its structure and transfers it's RNA genome(26-32kb comprising 7 genes) containing instructions, to replicate the virions, is carried from DNA to body's cells. This eventually leads to the production of millions of virions which hijack the cells function and ultimately causing cell death, causing viral pneumonia(inflammation of lungs). In severe cases the virus also leaks into the blood vessels, resulting in kidney failure. In utmost severe situation the virus spreads into the whole body through the blood vessels and ultimately leads to death.
As stated above, the virus itself contains a lipid membrane that helps us to kill the virus( upside also have a downside). This can be done by soap action on the virus. When soap(containing hydrophobic and hydrophilic end) is applied on the surface containing virions, soap gets near to the lipid membrane as it also contains two layers of lipids with the hydrophobic and hydrophilic end, the hydrophobic end of the soap gets attached to hydrophobic end of lipid in the membrane and vice Versa. Low amount of soap just gets attached to the membrane, but if a bit high amount of soap is applied it forms aggregates, and by the action of water the aggregates get removed from the surface and hence the virion losses its structure and will not be able to penetrate the cell, and so it's action will be terminated in the step one itself
IMMUNARY RESPONSE
When our immune system recognises that there’s a new virus in your body, it starts using signalling molecules called cytokines to start calling in reinforcements to the site of infection. Many of those cytokines end up causing fever in order to kill the virus
VACCINE DEVELOPMENT
Generally, vaccine development requires an actual virus sample which is inactivated by adding special chemicals before it's put into a vaccine. When the inactivated or weakened virus is injected into the body immune system recognises it as a foreign invader or an antigen. Vaccines use antigens to prime the body to protect against a particular virus. But vaccines developed with rapid response platforms work differently. Rather directly injecting the antigens into the bodies, these type of vaccines typically send instructions to the cell in the body. It gets the cells to produce antigen proteins that are specific to the virus is designed to defeat. These instructions are in the form of RNA or DNA. This process cuts down on development time, unlike normal vaccines, because they don't have to grow the whole virus. Additionally, once scientists identify and create the instructions for one virus, they can tweak those instructions to make a vaccine for a similar virus.
Vaccines of other types are also under experimentation which have potential to contain this pandemic.
But that's the idea for another sci-hole story.
REFERENCES/CITATIONS:
Tok TT, Tatar G. Structures and Functions of Coronavirus Proteins: Molecular
Modeling of Viral Nucleoprotein. Int J Virol Infect Dis. 2017;2(1): 001-007.
Graham RL, Baric RS. Recombination, reservoirs, and the modular spike:
mechanisms of coronavirus cross-species transmission. J Virol. 2010; 84:
3134-3146. https://goo.gl/89BVoZ.
Bárcena M, Oostergetel GT, Bartelink W, Faas FG, Verkleij A, Rottier PJ,
et al. Cryo-electron tomography of mouse hepatitis virus: Insights into the
structure of the coronavirion. Proc Natl Acad Sci U S A. 2009; 106: 582-587.
https://goo.gl/6eTwmf
Blau DM, Holmes KV. Human coronavirus HCoV-229E enters suscept l
cells via the endocytic pathway. Adv Exp Med, Biol. 2001; 494: 193-8.
https://goo.gl/nJGLVx.
Chu VC, McElroy LJ, Ferguson AD, Bauman BE, Whittaker GR. I
infectious bronchitis virus enters cells via the endocytic pathway. Adv Exp
Med Biol. 2006; 581: 309-312. https://goo.gl/UNbb12.
Eifart P, Ludwig K, Bottcher C, de Haan CA, Rottier PJ, Korte T, et al. Rol f
endocytosis and low pH in murine hepatitis virus strain A59 cell entry. J Virol.
2007; 81: 10758-68. https://goo.gl/v2e5eH.
Wang H, Yang P, Liu K, Guo F, Zhang Y, Zhang G, et al. SARS coronavirus
entry into host cells through novel clathrin - and caveolae-independent
endocytic pathway. Cell Res. 2008; 18: 290-301. https://goo.gl/xemCsE.
Nice information. Thank you for creating awareness
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