Role of B Cells and T Cells in COVID Vaccine Strategies

As of this writing, various vaccines are in production to fight SARS-CoV-2, the virus responsible for COVID-19. Important questions about each vaccine include what type of immune response it produces — and the longevity of that response. There are three possible immune responses generated by a successful vaccine: the production of B cells or T cells — or both.

Antibodies produced by B cells attack the virus directly. Reports indicate that antibodies produced by the B cell response to COVID-19 are relatively short-lived. This response is similar to that seen for other types of coronaviruses, such as the common cold. Experience has shown that antibodies produced to seasonal influenza are also short-lived. Optimally, antibodies would be active over the long term. In lieu of this, it is possible that individuals who have been infected with, or vaccinated against, COVID-19 could develop a rapid antibody response to any subsequent exposure based on B cell “memory.”

Recent data indicate that another form of immune response has the ability to provide longer-term protection against COVID-19. This second line of defense is provided by T cells. Unlike B cells, T cells do not attack the virus directly, but instead target infected cells — thus stopping the virus was reproducing. It has long been suspected that individuals infected with SARS-CoV-2 develop T cell-based immunity. One of the problems in proving this is that T cells are harder to measure than antibodies, and thus have not been extensively studied in COVID-19 patients.

UNLIKE B CELLS, T CELLS DO NOT ATTACK THE VIRUS DIRECTLY, BUT INSTEAD TARGET INFECTED CELLS

New information on this topic hails from a study headed by Shamez N. Ladhani, MRCPCH, PhD, a consulting epidemiologist with Public Health England. His group produced data on the long-term effect of T cells in 100 patients who had been exposed to COVID-19. Regardless of the degree of clinical symptoms, six months after infection all of these patients had elevated levels of T cells that were directed against the virus. These were found to be independent of the patient’s antibody response. A working hypothesis is that long-term T cell immunity may be found in COVID-19 cases. This theory is supported by research by Paul Moss, PhD, a hematologist at the University of Birmingham, who reports that individuals exposed to the original SARS virus in 2002 to 2003 still had T cell immunity up to 10 years later.

Some of the companies developing COVID-19 vaccines have decided it is important to stimulate both the T cell and B cell response — and, in fact, Pfizer/BioNTech, AstraZeneca Oxford and Moderna have developed vaccines that stimulate both forms of response. Of course, other approaches are in play among the numerous vaccines being developed globally.

Ultimately, time will tell whether a vaccine that stimulates both types of cells will help ameliorate the current pandemic. But these are certainly developments worth watching.

Thomas G. Wilson Jr., DDS
Editor in Chief
twilson@belmontpublications.com

From Decisions in Dentistry. December 2020;6(11): 4.