ePortfolio #2

COVID-19 vaccines have provided extraordinary results in preventing severe illness and reducing transmission.  However, researchers and scientists have yet to establish an exact metric in measuring overall protection.  Protective immunity, whether induced by vaccination or infection, requires that components work together to recognize and respond to specific pathogens. When considering adaptive immunity, there are two types: humoral immunity, mediated by antibodies and memory B cells and cellular immunity, mediated by CD4+ T helper cells and CD8+ T cytotoxic cells.   

So far, most COVID-19 studies have focused on the humoral aspect of immunity, using neutralizing antibodies (Nab) as quantifiable evidence of protection against SARS-CoV-2 virus.  Neutralizing antibodies are proteins that can bind to the virus and prevent it from entering cells.   Unfortunately, results over time showed less than desirable outcomes and though high initially, Nab titers rapidly diminished within the span of 4-6 months (1).  It’s important to note that the presence of neutralizing antibodies is just one aspect of the immune response. T-cell responses and other components of the immune system also play an important role in providing protection. 

In the event that viral particles are able to evade recognition by antibodies, viral antigens presented by antigen presenting CD4+ helper T cells match with T cell receptors (TCRs) and trigger the release of numerous immune molecules to include cytokines (2).  These interactions stimulate proliferation and differentiation of immune cells. Helper T cells also interact with B cells (short-live and long-lived plasma cells) (1), promoting the production of memory B cells equipped with virus-specific antibodies.  Additionally, they assist in the activation of cytotoxic T cells.  CD8+ Cytotoxic T cells then recognize viral peptides presented on infected cells through major histocompatibility complex class I (MHC-I) molecules, resulting in the termination of infected cells through apoptosis (cell death) (3). 

As listed, the four main goals for SARS-CoV-2 vaccination are: “protection from acquisition of infection; prevention of transmission; protection from severe disease; and prevention of Long Covid (1).” With these goals in mind, it becomes necessary to analyze each aspect of the two components of adaptive immunity and how their performance could be evaluated.  In the graphic provided in the article T cell immunity to COVID-19 vaccines (1) we can see that high titers of neutralizing antibodies, block infection of the upper respiratory track, inhibiting severe acute respiratory syndrome coronavirus 2.  Evasion of viral particles occurs as NAb titers lessen.  Though T cells are unable to prevent infection, their response assists in protection from severe disease and prevention of Long Covid.  On a cellular level, T cells can block infection to the lower respiratory tract that results in the progression of severe disease. However, when both humoral and cellular immune responses are weak, disease progression occurs (1).

Research suggests that a better understanding of T cell immunity is imperative to the comprehension of COVID-19 vaccine responses.  T cell response and cellular immunity is becoming increasingly valuable as viral variants such as Omicron, with higher levels of infectivity, pose a greater risk of escaping Nab recognition and diminishing the role that humoral immunity plays in long term protection and immune response. Additionally, further knowledge will benefit in the production of more effective vaccines going into the future.  This article was able to succinctly connect the relevance of immunology with medicine, building an emphasis on the roles and interactions that occur between B and T cells, and how the activation of T cells occurs as a result of antigen presentation and compatibility, helping to regulate the rate of infection.   Concepts covered within our textbook, particularly those of chapters 3 and 10 discuss in greater detail the recognition and response, activation, differentiation and memory of T cells that coincide with this article.

References

  1. Wherry, J. E., & Barouch, D. H. (2022). T cell immunity to COVID-19 vaccines. Science. 377,821-822(2022). DOI:10.1126/science.add2897. https://www.science.org/doi/10.1126/science.add2897
  2. 2. Sapir, T., Averch, Z., Lerman, B., Bodzin, A., Fishman, Y., & Maitra, R. (2022). COVID-19 and the Immune Response: A Multi-Phasic Approach to the Treatment of COVID-19. International journal of molecular sciences, 23(15), 8606. https://doi.org/10.3390/ijms23158606
  3. Punt, J., Stranford, S., Jones, P., & Owen, J. (2019). Kuby Immunology (8th ed.). Macmillan Learning. https://store.macmillanlearning.com/us/;jsessionid=A37228D3401BC4CA570BE1C7C712CA2F.accstorefront-655f64bf49-slmhv?_ga=2.149373366.1464161725.1700273893-35203620.1694702811