Article: T cells and COVID Vaccine
Mark Ciardiello
Bachelor of Science
BIOL302 Introduction of Immunology
4/5/2024
Our current understanding of how T cells play a role in cellular immunity has improved greatly since the outbreak of COVID-19. We have a better idea of what to look for in future vaccines and what we did achieve through mRNA vaccines, but it took a lot of trial and error. The article goes into how the COVID-19 vaccine functions, what immunity we’ve gained from the vaccine, and what immunity we still have to gain from further developments of the vaccine. After covering both B and T cell development, their activation pathways and attack methods, this article is very relevant to our coursework.
A vaccine is developed in the hopes that our bodies will develop both humoral and cellular immunity to whatever pathogen we are trying to vaccinate for. The current COVID-19 vaccine appears to only target the humoral side of immunity. Humoral immunity is mediated by antibodies and memory B cells, which the vaccine provides the “materials” for. The mRNA vaccine consists of instructions in the form of mRNA for our cells to use to produce spike proteins found on the surface of SARS-CoV-2. These spike proteins are recognized by antigen presenting cells (APCs) and displayed to CD4+ T cells, which in turn bind to specific B cells for that antigen, producing both memory B cells and plasma cells for the specific antibody that attacks the antigen. The B cells can also be activated by the antigen itself without T cell help if the antigen binds to the B cell receptor (BCR). The initial plasma cells can produce low quality, but immediate antibodies, while the memory B cells take time to go through germinal centers to eventually produce high quality antibodies. After antibodies are produced, the virus is attacked and has reduced ability to infect host cells (1). The article does a decent job at describing the antibody production process, explaining how low-affinity or low-quality antibodies are produced first while the higher-affinity antibodies are produced later by plasma cells that undergo somatic hypermutation. With that said, the article falls short in describing the interactions between T cells and B cells involving the antigen.
The antibodies produced in response to the antigen are effective, but viruses have a way to get around antibodies, mutation. When new variants mutate from SARS-CoV-2, they have different spike proteins, which can vary by a little or by a lot from the original virus. If the variation is enough, the antibodies our bodies made specifically for the original strain won’t function appropriately or perhaps at all. This is where cellular immunity comes into play, specifically the memory side. Cellular immunity includes the CD4+ T cells and the CD8+ T cells, but one of the most important immune cells are the memory T cells. Post infection, our immunity to SARS-Cov-2 is reliant on both antibodies and memory T cells. The antibodies are produced by memory B cells that quickly differentiate into antibody producing plasma cells. As said before, if variants change, these antibodies lose their efficacy, but memory T cells not so much. T cells aren’t limited to the RBD and NTD domains of the spike proteins, so they can continue to recognize variants like Omicron when original spike protein antibodies cannot (1). This leads us to believe that memory T cells after first infection are extremely important to the body’s immune health for future infections of SARS-CoV-2.
What this means for future vaccines is that we need to include more parts of the total virus in our immunizations for SARS-CoV-2. This would not just give us the spike protein antibodies we were looking for in a mRNA vaccine, it would also give us T cell protection, further increasing our resistance to viral mutations in the pathogen.
Overall, the article described the history of the COVID-19 vaccine in detail. It covered both the B-cell and T-cell side of immunity, with only missing out on some key details. The content from the article is easier to understand after reading and watching the lectures on chapters 10, 11, and 12.
References
- Wherry, E. J., Barouch, D. H. (2022) T cell immunity to COVID-19 vaccines. Science, https://www.science.org/doi/10.1126/science.add2897
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