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← Theoretical B

Q48 — mRNA Nucleotide Modifications and Vaccine Design

Theoretical B Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Immune Physiology

An mRNA vaccine is a type of vaccine where a pathogenic antigen is encoded in an mRNA sequence. Upon delivery to the human body, cells translate this mRNA and make protein antigens — examples of mRNA vaccines include vaccines developed against the SARS-CoV-2 virus.

Before the development of mRNA vaccines, various forms of RNA nucleotide modifications had been tested for the immunogenic potential of mRNA itself (Figure 1). Note that under normal physiological conditions, RNA can exist outside cells in body fluids.

Two-panel figure: panel A shows four flow-cytometry dot plots (unmodified RNA, m5C, pseudouridine (Ψ), and s2U) plotting CD83 against MHC-II expression in dendritic cells, each with the percentage of cells above and below an activation threshold; panel B is a bar chart of fold-increase in translation for mRNA with different nucleotide modifications (unmodified, Ψ, m5U, s2U, m5C, m6A, and 5%-m6A). Figure 1. A Activatory response of antigen-presenting dendritic cells to specific RNA nucleotide modifications, recorded as cell-surface receptor levels (UN: unmodified). Each dot represents a single dendritic cell; above the threshold, dendritic cells are activated, expressing higher levels of both CD83 and MHC-II. B Efficiency of modified mRNAs’ translation by cells (UN: unmodified).

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. It is expected that the body's mRNA is modified to prevent auto-immune response.
B. mRNA vaccines having s2U modifications will have the highest efficiency in generating viral antigens.
C. mRNA vaccines against SARS-CoV-2 are more likely to contain m5C than pseudouridine (Ψ).
D. Both leukocytes and erythrocytes can serve as a host to produce antigens encoded in mRNA vaccines.
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Question reproduced from IBO 2024, Theoretical Exam Part B, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF