The study analyzed the response of the SARS-CoV-2 virus and three other common cold coronaviruses after administration of an mRNA-based COVID-19 vaccine. Blood samples from 30 healthcare workers who had not tested positive for COVID-19 were analyzed before and after they received the Pfizer-BioNTech or Moderna COVID-19 vaccine.
The study model focused on the coronavirus surface proteins – spike proteins – which help viruses gain access to host cells and infect them. A type of immune cell called helper T cells or CD4+ T cells recognize these viral proteins on the coronavirus-infected cells and encourage cell destruction. The mRNA-based COVID-19 vaccines contain a code that allows healthy cells to produce these spike proteins. This promotes the build-up of a CD4+ T cell response specific to coronavirus spike proteins. The CD4+ T cell response was analyzed using blood samples before and after vaccination to indicate the effectiveness of the vaccine.
As the research group expected, the vaccinated participants showed a greater CD4+ T cell response to SARS-CoV-2 after vaccination. But other coronavirus variants were tested too with the hopes of understanding the effectiveness of the COVID-19 vaccine against variants.
Variants of the SARS-CoV-2 differ in some of the building blocks of their spike proteins. In testing the common cold coronaviruses HCoV-NL63, HCoV-229E, and HCoV-OC43, researchers measured the degree of immunity provided when exposed to the variants.
The research group observed that there was a broad T cell response to the SARS-CoV-2 virus, and they were able to identify 23 distinct viral proteins targeted by coronavirus-specific T cells.
Of these 23 peptides, four may be altered in the UK B.1.1.7 and South African B.1.351 variants. This suggests that the 19 other peptides (building blocks) are constant among coronaviruses and would be targeted by vaccine-induced CD4+ T cells when exposed to the SARS-CoV-2 virus and other emerging variants.
Results from another study by the Johns Hopkins School of Medicine reiterated the significance of the CD4+ T cell response to SARS-Cov-2 and common cold coronaviruses. They tested the T cell response to spike proteins in patients who had recovered from COVID-19 as well as unexposed individuals. In 65% of participants, memory CD4+ T cells recognized spike proteins from SARS-CoV-2 and at least one other common cold coronavirus.2
The cross-recognition observed by CD4+ T cells have led researchers to conclude that mRNA-based COVID-19 vaccines may protect against SARS-CoV-2 variants. The effectiveness of the COVID-19 vaccine against variants needs to be studied further to fully understand the level of protection.
- Woldemeskel, B. A. et al. (2021). SARS-CoV-2 mRNA vaccines induce broad CD4+ T cell responses that recognize SARS-CoV-2 variants and HCoV-NL63. The Journal of Clinical Investigation, In-Press Preview. Doi: 10.1172/JCI149335.
- Dykema, A. G. et al. (2021). Functional characterization of CD4+ T-cell receptors cross-reactive for SARS-CoV-2 and endemic coronaviruses. The Journal of Clinical Investigation, In-Press Preview. Doi: 10.1172/JCI146922.
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