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mrna-vaccines-against-coronavirus-disease-2019-covid-19-production-and-mechanism-of-action

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 • • 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