CrossFit | Simplified Viral Anatomy

Simplified Viral Anatomy

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ByCrossFitApril 8, 2020

A virus is a unique microscopic agent that does not fit neatly into the biological package we call a cell. A cell has:

  1. Defined cellular structure with organelles 
  2. Metabolic infrastructure and function – The ability to convert consumed non-living materials into biological energy and cellular components
  3. Homeostatic controls – The ability to regulate the internal environment
  4. Reproductive capacity – The ability to produce offspring
  5. Responsiveness – The ability to respond to external stimuli and conditions
  6. Capacity for growth
  7. Capacity for adaptation – The ability to alter form, function, or both over time in response to environmental challenges

A virus is structurally and functionally different. It is essentially an organized fusion of proteins and nucleic acids (genetic information). As such, a virus lacks:

  1. Defined cellular structure – Cytoplasm, a cell wall or cell membrane, ribosomes, and mitochondria are all lacking.
  2. Metabolic infrastructure – Without metabolic enzymes of its own, a virus is parasitic, relying on invaded cells for provision of metabolic capacity.
  3. Reproductive capacity – In an isolated state, a virus can’t reproduce itself and relies on the exploitation of invaded host cells to enable replication.

In most high school and college biology courses, we learn about the structure of a virus through the presentation of how a bacteriophage is built.

Figure 1: Bacteriophages possess a nucleic acid molecule surrounded by a protein structure, the head. The tail of the virus is composed of proteins and subdivided into the collar, sheath, base plate, and tail fibers. The tail fibers recognize complementary proteins on a target cell’s membrane and exploit those proteins to form bridging bonds with that cell.

A bacteriophage’s structure differs dramatically from other virus forms, such as the tobacco mosaic virus, the influenza virus, and the currently active SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), which drives the COVID-19 disease state (coronavirus disease originating in 2019). The bacteriophage, however, remains a good representation of the basic stages of the viral cycle:

  1. Adsorption – Attachment of the virus to a target cell
  2. Penetration – Once bound to the cell membrane, the virus transfers its nucleic acid contents into the cell to be invaded.
  3. Synthesis of viral proteins – The invaded cell’s internal machinery is involuntarily co-opted to produce viral proteins.
  4. Replication of viral nucleic acids – Instead of producing cellular genetic materials, the invaded cell replicates the viral genome.
  5. Packaging of viral genome and viral proteins – New viruses are assembled.
  6. Lysis – The invaded cell is ruptured to release newly formed viruses into extracellular spaces to amplify infection.

While these stages represent a valid generalization of how all viruses work, there are multiple types of viruses with different anatomical schemes. Each variant effects some change in the viral cycle, and each variant affects host selection and virulence. Viral categorization is most frequently done by morphology:

  1. Head and tail virus – These are the prototypical teaching examples; they are bacteriophages — i.e., viruses that infect bacteria.
  2. Filamentous virus – Many plant viruses fall into this category.
  3. Isometric or icosahedral virus – Poliovirus and the herpes viruses fall into this category.
  4. Enveloped virus – These viruses have membranes surrounding their protein shells, or capsids. Most animal viruses — including the variola virus (smallpox), human immunodeficiency virus, influenza viruses, and the coronaviruses (e.g., SARS-CoV and MERS-CoV) — fall into this category.

The most pressing epidemiological virus we currently face is the SARS-CoV-2 variant of the envelope virus. What makes this particular virus so insidious is not that it is dramatically more deadly than other similar viruses but that it appears to be more infectious. Biologists are currently working to understand which anatomical features of the virus create this anomalous efficiency in its entry into cells.

Figure 2: SARS-CoV-2 possesses nucleic acid materials contained within a proteinaceous envelope. Additional proteins are embedded in the envelope. Some of these proteins occur as protruding stalks with spike proteins at the terminus. These proteins recognize complementary proteins on a target cell’s membrane and exploit those proteins to form bridging bonds with that cell.

A prominent track of the rapidly evolving research into SARS-CoV-2 relates to the spike proteins of the protein capsule. These proteins interact with the cell to be invaded. Some believe targeting the spike proteins and blocking their binding capacity will provide a solution to the problem of infection. This is just one avenue scientists are investigating to get a handle on the virus and help us all return to as normal a life as possible soon.

Comments on Simplified Viral Anatomy

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Luke Palmisano
April 9th, 2020 at 7:25 pm
Commented on: Simplified Viral Anatomy

This is great. Zinc seems to have a heightened role in the specificity of processing nucleic acids (manufacturing DNA/RNA) and theory is that Zinc supplementation can help fight off viruses by improving the body's own specificity and picking up on abnormal DNA/RNA production. Any thoughts on this from a basic scientist? I am a practicing ER doctor, with a ton of virus treating experience though minimal basic science research/lab experience.

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Marcel Ferreira Martins
April 9th, 2020 at 6:19 pm
Commented on: Simplified Viral Anatomy

M, 242lbs, box 30", tuck hold 30".

Time 17'26"

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Mary Dan Eades
April 9th, 2020 at 6:13 pm
Commented on: Simplified Viral Anatomy

A great, simple, clear explanation of virus structure that just about anyone can easily understand. Helpful to know in this current covid situation and will illuminate discussion of what's going on in potential therapies. Of particular note is that in the course of viral attack, if you can prevent or slow steps 1 and 2 you can make headway against the virus. In that light, we read a really interesting article today that helps to explain why the metabolically fragile (meaning the 2/3 of Americans with pre-diabetes or frank diabetes and obesity) might be at greater risk. In the attachment step, ambient tissue glucose levels may play a role -- higher glucose favors easier attachment of the virus to a target host cell. And another article suggests that a mechanism for the anecdotal positive reports with the hydroxychloroquine/zithromax/zinc regimen may involve that same step -- interfering with attachment of the virus. Time and testing will tell.

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Stephanie Jones
April 9th, 2020 at 12:45 pm
Commented on: Simplified Viral Anatomy

I was so pleased to see this article come into my inbox today. I know nothing of viral anatomy so I learnt a little bit from this article and the comments following. Thank you for sharing information that is relevant to health in all respects!

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Sylvia Berrios
April 10th, 2020 at 11:51 pm

SO with you on this one Stephanie! I will be sharing this one as well as we all need to be informed in a more easier way such as this posting! Love the comments and questions also regarding researches done by some... so many smart folk here! Very much appreciated CrossFit.com!

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Erron Brady
April 9th, 2020 at 11:12 am
Commented on: Simplified Viral Anatomy

Very nice, basic article. Except the last part where the suggestion of targeting the spike protein as a possible solution. I don’t believe many people recommend this as in the past this has only made the disease worse. The current hope is to create a live attenuated vaccine. All other treatments for SARS-CoV I have proven ineffective except for some limited success in anti-viral medications. The spike protein has been found to bind to the ACE-2 cellular protein. Currently L-Arginine 700mg, Beet root extract, Black pepper, 5-10mg melatonin/daily and Vitamin C 1,000mg/ twice daily are shown to help prevent the severity of the disease (and yes I’ve read your articles that show your disdain for “vitamins” for the average healthy person).

IBU is shown to worsen the symptoms along with ACE inhibitors, ARB (ie...lisinopril amd losartan) , vitamin D and selenium (consult your doctor but most need to stop these if sick). 

As our knowledge of this disease changes daily it’s wonderful to see Crossfitters exchanging their knowledge. Thank you for your articles!!!

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John Smith
April 9th, 2020 at 1:24 pm

Agreed, the ACE-2 receptor of the host cell is key, and a treatment to protect the ACE-2 receptor is likely to be more broad-spectrum--working on all potential invaders--not just a specific strain of coronavirus. Flavonoids have been highly ranked by SUMMIT, the IBM's supercomputer, as having a molecular composition and shape well suited to bind to ACE-2 receptors and therefore block coronavirus S-protein spikes.

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Robert Sabbatino
April 9th, 2020 at 7:13 am
Commented on: Simplified Viral Anatomy

Been a health care professional for 54 years. The aforementioned article was probably the best presentation of virus information for the layperson (with minimal knowledge of biology) I’ve ever read. Emails from CrossFit are the first thing I read when I awake in AM. CrossFit-absolutely the BEST. A thousand kudos! Robert J. Sabbatino RPh

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Marcelino Ortiz
April 9th, 2020 at 4:40 am
Commented on: Simplified Viral Anatomy

Thanks for this explanation! I love de biology and appreciate a lot this info, really!

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Grace Patenaude
April 9th, 2020 at 2:33 am
Commented on: Simplified Viral Anatomy

Thank you for the very informative article so pertinent in our current state of affairs.

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