compounds to protect against pH fluctuation in the solution

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Recent reports found that Moderna’s mRNA-1273 vaccine is over 94% effective against Covid-19 infection. This news is a bright spot in what has been a dark and challenging year.
Now that the vaccine is set to be rolled out, let’s take a look at the ingredient list.

The Basics
Moderna’s mRNA-1273 is an mRNA vaccine made up of strands of RNA packed into lipid nanoparticles. These particles, when injected into the human body will fuse to the cell membrane of human cells and allow the mRNA to gain access to the machinery needed to translate it into viral proteins. Once these proteins are generated, they are packed by the native vesicles within our own cells and released outside of the cell.
Once the viral proteins are released our immune system has the opportunity to generate antibodies against them.
Lipid Nanoparticle Technology
If the mRNA is the “message” of the vaccine, the lipid nanoparticle is the “envelope.” Lipid nanoparticles are created in the image of our own cell membranes, allowing them to travel within our bodies and fuse with human cells.
The lipid wall of the mRNA-1273 vaccine is made up of four different compounds:
SM-102 — a proprietary phospholipid that makes up the basic structure of the nanoparticle wall
DSPC — another commercially available phospholipid that will aid in the nanoparticle wall structure
Cholesterol — native to all of our cell membranes, cholesterol helps to add fluidity or stiffness to a cell membrane depending on temperature. The addition of cholesterol will aid in the stability of the nanoparticle.
PEG-2000 DMG — a lipid fused to polyethylene glycol with aids in the formation of the nanoparticle
The mRNA component of Moderna’s vaccine provides the human body the blueprint to generate copies of specific coronavirus antigens that elicit an immune response.
mRNA is lab generated using a DNA template built into a loop structure called a plasmid. Plasmids were derived from bacterial genomes, and are now common biotech tools used to shuttle or clone genes. The DNA template was derived from SARS-CoV-2 viruses isolated in Wuhan, China at the emergence of the pandemic. The genome from isolated viruses was then sequenced, and the code for specific antigens were made publicly available.
Using an enzyme called RNA polymerase, specific mRNA molecules can be generated using a template plasmid. These sequences also need a few key features to make them recognizable to the human cell, and safe from degradation. These include:
5' cap
5' untranslated region (UTR)
Coding Sequence (CDS) for SARS-CoV-2 spike protein
3' untranslated region (UTR)
Poly-adenosine (Poly-A) Tail
Additional Ingredients
Beyond the compounds used in making the nanoparticle, there are some ingredients used to control the aqueous environment that the vaccine is delivered in. These include:
Tris buffer — trisaminomethane (Tris) is a commonly used buffer in biological compounds to protect against pH fluctuation in the solution.
Sucrose — lab grade table sugar increases temperature stability of the nanoparticle
Sodium acetate — a compound very similar to vinegar that helps stabilize the particle.
The ingredient list for this vaccine is relatively simple compared to some preparations. Because these vaccines need to be stored at very cold temperatures, there is no need for preservative agents.
Also, because most of the compounds involved in this vaccine are native (or derived from native) compounds to our body, they do not pose any risk for adverse reactions. The main risk that could be associated with vaccines of this type are expected reactions like injection site redness and soreness, fatigue or headache — all of which resolve on their own within a day or two.
The mRNA-1273 vaccine appears to confer powerful immunity agianst Covid-19 in a safe manner. RNA vaccines are relatively fast and easy to manufacture. With Moderna’s improved temperature storage and delivery protocols, this vaccine appears to a strong candidate for widespread vaccination efforts in 2021.
For more information here is Moderna’s full protocol for the mRNA-1273 vaccine.

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