Vaccines teach your body to recognize and fight off viruses and bacteria. Vaccines contain a telltale sign(s) of a disease-causing microbe or pathogen.
By Jamshed Arslan
Covid vaccines generally contain either a part or the instructions for producing a part of Coronavirus that can elicit body’s defensive response. This essay will explain your body’s immune response and why the recent news of Coronavirus variants from UK, South Africa, Brazil and others is problematic for currently available vaccines.
Immune response to virus
White blood cells (WBCs) are your body’s police. One fifth or more of WBCs in your blood are lymphocytes. B and T cells are two of the broad categories of lymphocytes. B cells are famous for producing antibodies when they recognize and encounter an antigen. Antigen is anything that can alarm your body’s police. T cells, on the other hand, help B cells in their functioning. T cells can directly kill the virus and virus-infected body cells. Macrophages are also expert in engulfing and destroying viruses. If all goes according to plan, you would not even know that you faced a pathogen; thanks to macrophages and B and T cells!
What happens when you receive current Covid vaccine(s)?
Covid jab allows your body to neutralize and destroy the virus. To understand this, consider the fact that a typical antibody is a Y-shaped structure with an area called Fc-region. In most of the people receiving current Coronavirus vaccines, the vaccine-induced antibodies detect viral antigens and render the virus harmless, a process called neutralization. Many WBCs have Fc-receptors. T cells and macrophages are among the macrophages that have the Fc-receptors to recognize and attach to Fc-region of the antibody. Since antibody is already attached to the virus, Fc-receptor containing macrophages gobble up the virus and destroy it.
Problem with Coronavirus variants
Imagine you received the Covid jab and now you have the antibodies that can neutralize the most prevalent variety of Coronavirus. However, if your body encounters a different Coronavirus variety, your antibodies may still bind to the virus, but they would not be able to neutralize the virus. In other words, your jab trained your B cells to recognize Coronavirus that is of different variety than the one you encountered. In such cases, the virus can remain functional despite being attached to the vaccine-produced antibody. Your macrophages will eat up the antibody-bound virus. That is exactly what will harm your body.
Now that the functional virus is inside the macrophages, it is rather protected from body’s immune system. This is the ideal situation for the virus. It will take over the functions of macrophages, essentially making them virus-producing factories. These factories will produce a variant form of Coronavirus and the entire cycle keeps repeating: vaccine-produced antibodies bind to mutant virus, macrophages eat up antibody-bound virus via Fc-receptors, and the virus takes control of the macrophages to produce more and more Coronavirus variants. This is called antibody-dependent enhancement (ADE).
Vaccines cannot prevent infection in the presence of ADE. In fact, ADE is responsible for failure of many vaccine trials. ADE keeps your immune system busy, but without any benefits. The result is inflammation that may not be limited to only one tissue or organ. One means of avoiding ADE is to generate vaccines that contain multiple parts of the virus.
Vaccines with multiple targets
Coronavirus contains four structural proteins. Current vaccines primarily target only one of these proteins called the spike protein. Instead of generating antibodies that could recognize only one part of the virus, many vaccines are under trial that can train your body to recognize and produce antibodies against all the structural proteins of the virus. It is easier for mutation(s) to occur in one protein than in all the four proteins. In this way, the next-generation vaccines can avoid the potential problem of ADE.
Meanwhile, please get vaccinated if possible, wear mask, wash your hands, and support the scientific research on Covid therapies.
References
Lee, W.S., Wheatley, A.K., Kent, S.J. et al. (2020). Antibody-dependent enhancement and SARS-CoV-2 vaccines and therapies. Nature Microbiology, 5, 1185–1191. https://doi.org/10.1038/s41564-020-00789-5.
World Health Organization. (2021). COVID-19 vaccines. https://www.who.int/emergencies/diseases/novel-coronavirus-2019/covid-19-vaccines.