mRNA Vaccines against Coronavirus Disease 2019 (COVID-19):
Production and Mechanism of Action
Vaccine Production
The “spike protein” is known to be a major viral surface
Authors: Ryan Brenneis, Yan Yu* Reviewers: Davis MacLean, Hannah Yaphe, Timothy Fu, Stephen Vaughan* * MD at time of publication
References
1. ACS Nano 2020, 14, 10, 12522–12537, Publication Date: October 9, 2020, https://doi.org/10.1021/acsnano.0c07197
2. NEJM 2020, Publication Date: December 10, 2020, DOI: 10.1056/NEJMoa2034577
3. Expert Review of Vaccines 2017, 16, 9, 871-881, Publication Date: 2017, DOI: 10.1080/14760584.2017.1355245
4. NEJM 2020, 383, 2439-2450, Publication Date: December 17, 2020, DOI: 10.1056/NEJMoa2027906
5. NEJM 2020, 383, 2427-2438, Publication Date: December 17, 2020, DOI: 10.1056/NEJMoa2028436
6. BMJ 2000, 321, 7271, 1237-1238, Publication Date: November 18, 2000, DOI: 10.1136.bmj.321.7271.1237
Notes:
SARS-CoV-2 (RNA virus causing COVID-19) collected from an infected patient (ie. with a nasopharyngeal swab)
Various reagents are added to the sample containing both human cells and viral constituents
Reagents cause cell/viral membrane lysisàspilling cell contents, viral particles, and viral RNA
Fats, proteins, and carbohydrates removed through various washing reagents, leaving nucleic acids (like RNA)
Reverse transcriptase polymerase chain reaction produces complementary DNA (cDNA) from viral RNA
cDNA library allows for SARS-CoV-2 genome to be mapped through whole-genome sequencing technology
SARS-CoV-2’s spike protein DNA sequence is identified, and is used as a template to create synthetic viral spike protein mRNA
Extra RNA bases are added to this mRNA strand to promote its stabilityàresulting RNA strand is now called “nucleoside-modified RNA” (“modRNA”)
antigen (substance that elicits an immune response) from studies of other coronaviruses (e.g. SARS- CoV-1 and MERS-CoV)
Pfizer/BNT162b2 vaccine contents:
Moderna mRNA-1273 vaccine:
Note: Lipid nano- particles are spherical hollow “balls” made of an outer lipid membrane plus other emulsifiers and membrane stabilizers.
Lipid nanoparticles are capable of engulfing smaller molecules (like RNA) and merging with normal cell membranes
Spike protein modRNA is then isolated (using a series of precipitation, extraction, and chromatography methods)
Final modRNA lipid nanoparticle vaccine is now created and ready for intramuscular injection
The modRNA vaccine is injected intramuscularly into a healthy person 2nd dose after 3-4 weeks needed to strengthen the immune response
(to a level exceeding the immune response in patients recovered from Covid-19), boosting vaccine efficacy especially in older individuals4,5
Lipid nanoparticle fuses with human cells’ phospholipid membranes via endocytosis, releasing modRNA into the cell’s cytosol
modRNA is translated by human ribosomes naturally found in the cell’s cytosol, producing viral spike protein components
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Foreign substance can cause local tissue inflammation
The spike proteins encoded by the modRNA of each of the two vaccines are similar
It is the proprietary lipid nanoparticle formulation (unknown to the public) that is unique to each vaccine
Pain, redness, swelling at injection site (Transient)
Proprietary Pfizer/ BioNTech lipid nanoparticle
The modRNA encodes a
full-length spike protein modified with two proline amino acids (for stability and immunogenicity)2
The modRNA encodes a full-length spike protein modified with two proline amino acids (for stability)1
Proprietary Moderna lipid nanoparticle
Encapsulating this modRNA within Pfizer/ BioNTech’s lipid nanoparticle creates the 162b2 vaccine
This specific formulation requires colder storage temperatures (-700C)
Encapsulating this modRNA within Moderna’s lipid nanoparticle creates the mRNA-1273 vaccine
This specific formulation can be stored at slightly warmer temperatures (-200C)
Muscles are preferred injection sites as they have greater blood supply than other body tissues
Vaccine Action
Able to bring in immune cells faster to process foreign antigens6
Able to drain away foreign vaccine material fasterà minimizing local reactions6
Cell-mediated Immunity
Spike protein degraded by intracellular enzymes into fragments
Humoral Immunity
Natural cellular processes release spike protein components from the cell into the bloodstream
Spike protein components are engulfed by antigen presenting cells (dendritic cells, B cells, macrophages), fragmented, & bound to unique MHC Class II proteins
MHC Class II proteins bring spike protein fragments to the antigen presenting cell’s surface, to present them to circulating naïve CD4+ (helper) T cells
Some naïve helper T cells are able to successfully bind to the spike protein-MHC Class II protein complexes
Binding activates these spike-protein specific helper T cells
Spike protein fragments bound by MHC Class I proteins
MHC Class I proteins bring spike protein fragments to the human cell surface
MHC Class I proteins present spike protein fragments to naïve CD8+ T cell
Naïve CD8+ T cells that able to bind to the spike protein-MHC Class I protein complex become activated, and travel to the lymphatic system to mature
MHC = Major Histocompatability Complex; cell surface proteins key to immune function
CD = Cluster of Differentiation; glycoproteins on T cell surfaces that are co-receptors and facilitate T cell binding to antigens/MHC complexes. They also distinguish the types of T cells.
Some of these T-Cells mature into cytotoxic T cells that now recognize the viral spike protein
Cytotoxic T-cells bind to human cells infected with SARS-CoV-2 expressing spike protein or spike protein fragments
Cytotoxic T cell releases enzymes perforating infected cell, causing cell death to occur
Immune system identifies and destroys human cells infected with SARS-CoV-2, slowing viral spread
Other T cell’s can mature into memory T cells (stimulated by cytokines released by helper T cells)
Memory T cells travel to lymphatic tissue, awaiting activation from future exposure to spike protein
More rapid cell-mediated immune response to future SARS-CoV-2 infection (immunity)
Activated helper T cells specific to the viral spike protein secrete cytokines to stimulate immune activity
Systemic cytokine releaseàsystemic reactions like fever, chills, fatigue, myalgias (Transient)
Some B cells mature into plasma cells that produce IgG antibodies against the viral spike protein
Antibodies to spike protein mark SARS-CoV-2, allowing immune system to destroy virus
Eradication of SARS-CoV-2 in extracellular compartments
Activated helper T cell interacts with
naïve B cells in lymphatic tissue
Some B cells mature into memory B cells specific to SARS-CoV- 2 spike protein
Future exposure to spike protein re-activates memory B cell in lymphatic tissue & creates plasma cells, producing antibodies more rapidly
Rapid humoral immune response to future SARS-CoV-2 infection (immunity)
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Clinical Finding
End Result
Published December 19, 2020 on www.thecalgaryguide.com