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MAGIC OF mRNA VACCINES
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- The mRNA vaccines (by Pfizer and Moderna) are scientifically quite sophisticated. They work in a logical and nature-mimicking manner
- Human immune system works using principles evolved over several lakh years. The immune cells attack anything foreign to the body, and if they see a protein or a virus or a bacteria or anything that it doesn’t recognize, it launches an attack.
- If the immune system is fighting off a virus, it takes some time to build up a full attack. The system tries to find what part of the virus to attack & produce chemicals or parts needed to attack those specific parts (of the virus).
- That does not happen instantly. It can take a few days. Meanwhile, the virus is replicating and expanding!
- Once the system has fought off the virus, though, it "remembers" it. The memory cells in the immune system do it, and if the body runs into that virus again, the memory cells will say “We’ve seen this before”. The body uses its past experience to demolish the virus before it can make you sick.
- VIRUS BASICS
- Viruses are inert outside the host cell. Small viruses, e.g., polio and tobacco mosaic virus, can even be crystallized.
- Viruses are unable to generate energy. As obligate intracellular parasites, during replication, they fully depend on the complicated biochemical machinery of eukaryotic or prokaryotic cells.
- The main purpose of a virus is to deliver its genome into the host cell to allow its expression (transcription and translation) by the host cell.
- A fully assembled infectious virus is called a virion.
- The simplest virions consist of two basic components: nucleic acid (single- or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.
- Capsid proteins are coded for by the virus genome. Because of its limited size the genome codes for only a few structural proteins (besides non-structural regulatory proteins involved in virus replication).
- Capsids are formed as single or double protein shells and consist of only one or a few structural protein species.
- Therefore, multiple protein copies must self assemble to form the continuous three-dimensional capsid structure. Self assembly of virus capsids follows two basic patterns: helical symmetry, in which the protein subunits and the nucleic acid are arranged in a helix, and icosahedral symmetry, in which the protein subunits assemble into a symmetric shell that covers the nucleic acid-containing core.
- Now, scientists in 2020 looked at the COVID-19 virus and found a protein on the outside of the virus that looked like a good candidate to launch an immune attack against.
- That protein is an important one for the virus. Why? Because it uses that protein to get into the body cells. That protein makes the virus more infectious.
- Now COVID-19 virus has RNA in it, that codes for all of its parts (not DNA). So scientists looked at the entire RNA sequence of this virus and found the sequence of RNA that is the blueprints for that target protein.
- DNA is the blueprint to make things in a cell. Cells take the DNA and transcribe it into RNA. The RNA is the instructions that tell the cell what to make. mRNA (literally messenger-RNA) literally just gives instructions to the cell to make something. Covid-19 has only RNA, no DNA.
- So scientists took the blueprint for the target protein on COVID-19 virus (SARS-CoV-2) and made an mRNA version of it. Literally just the instructions on how to make that protein.
- These instructions “are” the vaccine.
- The vaccine contains no actual part of the virus. It has only the instructions on how to make the target protein. So, a human can’t get infected with COVID from the vaccine. You just get these instructions.
- Remember the immune system hasn’t seen this protein before. It takes a while to "ramp up" production. Then it launches an all out war against the target protein. The fevers, chills, muscle soreness, etc. we might get as vaccine side effects is the body killing the target protein.
- So the body destroys the target protein (which in and of itself can’t infect you, it’s just a protein, not the virus).
- The memory cells ‘remember’ the target protein. They remember exactly how to destroy it.
- The body breaks down the mRNA instructions that you got with the vaccine pretty quickly too. That’s normal. We don’t need a bunch of instructions hanging around forever. Your body breaks those down and gets rid of them. So you’ve broken down the mRNA instructions. You’ve destroyed the target proteins. Everything from the vaccine is gone.
- Except for those memory cells who remember that protein very well. So when in the future, a real COVID virus enters the body, the body has never seen the virus before. But it’s seen that protein that’s on the outside of the virus. Your memory cells get activated and kill it.
- The body’s own ‘natural immune system’ quickly and efficiently launches an all out war, using the template it has from when it destroyed the target protein last time. It destroys the virus before it can take hold, replicate, and make you sick.
- Now, you’re immune to COVID! You’ve got the blueprints to defeat it as soon as it enters your body.
- What if the virus mutates so it doesn’t produce the target protein any more? Well, since it uses the target protein to get into your cells, if it mutates away from the target protein, it’ll probably also be less infectious.
- The question is - for how long will this stay effective? Scientists don’t know for sure. We have a very long memory for some viruses and shorter for others. So we’ll have to see for this one. Sometimes we make up for a shorter memory with a “booster” vaccine some ways down the road.
- What about the "viral load"? Can it be so huge that the vaccine is helpless?
- Most of the viral load comes from the virus replicating in the body, not by first exposure. But the vaccine is 95% effective, not 100%. A lot of that depends on how robust your own immune response is to the protein and how effective your memory cells are towards it.
- And what about reinfection? Reinfection from a virus you’ve had before could be because the virus mutated (in which case it’s technically a different virus) or because your ‘memory’ or that virus wasn’t as strong as you’d like.
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