mRNA Vaccine Technology

An mRNA vaccine delivers laboratory-made messenger RNA containing instructions for producing a selected viral antigen. Host cells temporarily translate this mRNA into antigen, allowing the immune system to learn the pathogen's molecular signature without exposure to the infectious virus.

Delivery and antigen production

Because naked mRNA is fragile and enters cells inefficiently, it is commonly enclosed in lipid nanoparticles. After cellular uptake, the mRNA is released into the cytoplasm, where ribosomes translate it into the encoded viral antigen.

• The mRNA functions in the cytoplasm and does not need to enter the nucleus.
• The mRNA and delivery lipids are subsequently broken down through normal cellular processes.
• The vaccine supplies genetic instructions for an antigen, not a complete replication-competent virus.

Activation of adaptive immunity

The produced antigen, or its peptide fragments, is displayed to immune cells through major histocompatibility complex pathways. Antigen-presenting cells activate helper T cells, which coordinate antibody and cellular responses.

• Activated B cells differentiate into plasma cells that produce antigen-specific antibodies, including antibodies capable of neutralising the virus.
• Presentation through MHC class I can activate cytotoxic T cells, which recognise and destroy infected cells displaying the same antigen.
• Innate immune sensing of the vaccine also provides signals that support the development of adaptive immunity.

Formation of protection

Some activated lymphocytes become long-lived memory B cells and memory T cells. On later exposure, they generate a faster and stronger response than during first contact with the pathogen.

• Pre-existing antibodies can block viral attachment or entry into host cells.
• Memory responses rapidly replenish antibodies and expand antigen-specific T cells.
• Protection may reduce infection, severe disease, or both, depending on the antigen, pathogen and immune response.

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