Summary of T Cell Immunity to COVID-19 Vaccines

Amanda Days

Biomedical Sciences

Introduction to Immunology BIOL 302

Professor Clayton Wright

3/17/2023

            Many studies focusing on the mechanism of immune responses from the Covid-19 vaccines showed that T cells could have a major role in vaccine protection. This information could help develop better vaccines and increase the understanding of how the vaccine works with immunity.

            The type of protection caused by vaccines and also infections is protective immunity which is part of the adaptive immune system. This system corresponds to either the immunity ran by antibodies and memory B cells, or the type involved with T cells.  Memory T cells are also involved in this immunity, but there is a lack of prevention of an infection with T cells. While T Cells are able to clear out virus-infected cells, it does not make for a suitable vaccine on its own because vaccines should be able to prevent as well as protect. That posed the question to today’s vaccine being could they continue to complete these goals and how long could they remain effective? This has been put to the test by the variant virus strain, Omicron, that had increased transmissibility and was resistant to neutralizing antibodies which reduced the ability of NAb blocking infections, the original proposed mechanism of the vaccine. Even with this variant though, hospitalization was still low enough to determine that alternative mechanisms of immunity introduced by the vaccine were effective in dealing with the virus.

            This being said, neutralizing antibodies are not the only factor that go into this system, it is instead a combination of the memory and protective immunity. B cells produce antibodies that first are short lived plasma cells which is then followed by a round of long lasting, effective antibodies and memory B cells. These cells will continue to persist after the initial infection and will work with T cells to generate an effective immune response. T cells work by recognizing molecules in complex with human leukocyte antigen class I and II molecules. This gives the cells an idea on the state of the one presenting the HLA molecules as in its health or if it is infected. This recognition ability allows memory cells to quickly be made when needed to limit viral replication, infection, and spread from host to host. Two types of these effective T cells are CD8+ T cells, which kill infected cells, and CD4+ T cells, which support B cells in their actions against infections.

            These different methods of immunity play into the effectiveness of the vaccines. For example, the NAbs bind to certain sites which block receptors, but those sites are prone to mutation making binding sometimes very difficult for antibodies. The T cell mechanism however does not involve such sites making it more effective against variants and more effective as a vaccine. This with the addition of memory T cells can cause long lasting immunity. In conclusion, the Covid-19 vaccine is not dependent on NAbs alone, but instead multiple different mechanisms that go into creating effective immunity. T cells are not enough to prevent infection alone, but when combined with B cells and other immunities produce long lasting effects. This could go on to play into future research by testing whether or not the T cells will continue to contribute to the vaccine efficacy or not. Overall T cells are extremely important in the effectiveness of the Covid-19 vaccine and could continue to provide further advancements in the field of immunity.