SEARCH RESULTS FOR: Adenovirus-Vector-Vaccines-Against-COVID19-Production-and-Mechanism-of-Action

Adenovirus-Vector-Vaccines-Against-COVID19-Production-and-Mechanism-of-Action

Adenovirus Vector Vaccines Against COVID-19: Production and Mechanism of Action Johnson & Johnson Adenovirus type 26 (Ad26), a mild human adenovirus, is isolated Previous exposure to Ad5 or Ad26 may have sensitized immune system to the adenovirus vector1 Potential for human adenovirus vaccine to fail due to previous exposureàimmunity not built against spike protein CanSino Adenovirus type 5 (Ad5), a mild human adenovirus, is isolated Oxford/AstraZeneca Chimpanzee adenovirus AZD1222 (ChAdOx1), previously shown to be safe & to elicit an immune response in humans2, is isolated Vaccine Production SARS-CoV-2 (virus causing COVID-19) synthetic DNA library sequenced from viral RNA using reverse transcriptase polymerase chain reaction and whole genome sequencing technology Spike protein DNA sequence isolated from SARS-CoV-2 genome A promoter sequence is added to the spike protein DNA sequence, allowing human RNA polymerase to recognize and transcribe the spike protein DNA when introduced into human cells Recombinant genetic technology inserts the modified spike protein DNA into a plasmid: a circular piece of DNA that acts as a shuttle allowing for the insertion of new genes (such as the spike protein gene) into host genomes (like the adenovirus vector DNA genome) Adenoviral DNA isolated using various lytic & washing reagents (chemicals that break open cell membranes and remove non- nucleic acid cellular materials) Adenoviral DNA sequenced using whole genome sequencing, then modified as follows: Chimpanzee virus negates possibility of previous immunity to the viral vector1 Chimpanzee viral vector more likely to successfully generate immune response to the spike protein E1 region of adenoviral genome E3 region of adenoviral genome deleted to create deleted to block viral replication3 room for insertion of SARS-CoV-2 spike protein DNA3 Adenovirus used in the final vaccine cannot replicate within human cells and cannot cause human disease References 1. ACS Nano 2020, 14, 10, 12522–12537, Publication Date: October 9, 2020, https://doi.org/10.1021/acsnano.0c07197 Modified adenoviral DNA genome is reinserted into The viral vector & the spike protein plasmid are mixed together, and DNA recombination the adenovirus particle, creating the “viral vector” technology inserts the spike protein gene from the plasmid into the adenovirus DNA2 Adenovirus containing transcribable SARS-CoV-2 spike protein DNA is introduced into a special cellular culture, allowing the virus to replicate despite its modified DNA2, 3 Authors: Ryan Brenneis, Yan Yu* Reviewers: Davis MacLean, Hannah Yaphe Stephen Vaughan* * MD at time of publication 2. Nature 2020, 586, 578–582, Publication Date: October 20, 2020, https://doi.org/10.1038/s41586- 020-2608-y 3. Frontiers in Immunology 2018, 9, 1963, Publication Date: September 19, 2018, doi: 10.3389/fimmu.2018.01963 4. NPJ Vaccines 2020, 5, 69, Publication Date: July 27, 2020, doi: 10.1038/s41541-020-00221-3 5. The Lancet 2020, Publication Date: Dec. 8, 2020, https://doi.org/10.1016/S0140-6736(20)32623-4 6. BMJ 2000, 321, 7271, 1237-1238, Publication Date: November 18, 2000, DOI: 10.1136.bmj.321.7271.1237 7. NEJM 2021, Publication Date: Jan. 13, 2021, DOI: 10.1056/NEJMoa2034201 Adenovirus containing transcribable SARS-CoV-2 spike protein DNA is isolated and concentrated to a high enough level for administration as a vaccine Adenoviruses have an outer protein layer (called a capsid) to protect its DNA DNA is more stable than mRNA due to deoxyribose sugar backbone and intermolecular bonds between strands Enhanced stability compared to mRNA lipid nanoparticle vaccines Can be stored at 2-8°C for up to 3-6 months Muscles are preferred injection sites as they have greater blood supply than other body tissues Immune cells arrive faster to The viral vector vaccine is injected intramuscularly into a healthy person process foreign antigens6 Foreign substance can cause local tissue inflammation Pain, redness, swelling at injection site (Transient) Note: The Johnson and Johnson vaccine may be 90% effective after a single dose7 Foreign vaccine material drains away fasterà minimizing local reactions6 2nd dose after 28 days recommended to strengthen the immune response (to a level exceeding the immune response in patients recovered from Covid-19), boosting vaccine efficacy especially in older individuals5 Vaccine Action Cell-mediated Immunity Spike protein degraded by intracellular enzymes into fragments Adenovirus surface antigens interact with human cellular receptors, allowing viral entry into human cell via endocytosis3 Adenovirus vector travels to cell nucleus, merges with nuclear envelope and injects its DNA (including the spike protein DNA) into the nucleus RNA polymerases in the nucleus transcribe the viral DNA, making messenger RNA (mRNA) for SARS-CoV-2 spike protein mRNA is transported back into the cytosol & translated by ribosomes naturally found there, producing full length SARS-CoV-2 spike protein 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 are 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 mature3 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 SARS-CoV-2 spike spike protein Cytotoxic T cells bind to human cells expressing spike protein or spike protein fragments (e.g. future COVID-19 infection) Cytotoxic T cells release enzymes perforating infected human cells, causing cell death to occur Immune system can now more quickly identify & destroy human cells showing signs of COVID-19 infection Some 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 exposure to spike protein in the future 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) Note: Duration of cellular/ humoral immunity is unknown 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)3 Legend: Pathophysiology Mechanism Sign/Symptom/Clinical Finding End result Published February 11, 2021 on www.thecalgaryguide.com