COVID-19 Vaccines and Protection Against Variants

Study Overview

A research team from the Johns Hopkins University School of Medicine has released a study indicating that certain COVID-19 vaccines may offer protection against variant strains of the coronavirus, specifically those first identified in the U.K. and South Africa. The study focused on the immune response elicited by mRNA-based COVID-19 vaccines.

Methodology

The researchers analyzed blood samples from 30 healthcare workers who had not previously tested positive for COVID-19. These samples were collected before and after the participants received either the Pfizer-BioNTech or Moderna COVID-19 vaccine. The study specifically examined the coronavirus surface proteins known as spike proteins, which facilitate the virus’s entry into host cells.

Immune Response Analysis

Helper T cells, or CD4+ T cells, play a crucial role in identifying these viral proteins on infected cells and promoting their destruction. The mRNA vaccines encode a sequence that enables healthy cells to produce spike proteins, leading to an enhanced CD4+ T cell response specific to these proteins. The effectiveness of the vaccines was assessed by comparing CD4+ T cell responses in blood samples taken before and after vaccination.

Findings on Variant Response

As expected, participants who received the vaccines exhibited a heightened CD4+ T cell response to SARS-CoV-2 post-vaccination. The study also evaluated other coronavirus variants to gauge the vaccines’ effectiveness against them. Variants of SARS-CoV-2 possess variations in their spike protein building blocks.

In addition to SARS-CoV-2, the researchers tested responses to common cold coronaviruses HCoV-NL63, HCoV-229E, and HCoV-OC43, measuring the immunity conferred upon exposure to these variants. The team observed a broad T cell response to the SARS-CoV-2 virus, identifying 23 distinct viral proteins targeted by coronavirus-specific T cells.

Implications of the Findings

Among the 23 peptides identified, four may have alterations in the U.K. B.1.1.7 and South African B.1.351 variants. This suggests that the remaining 19 peptides remain constant across coronaviruses and are likely targeted by vaccine-induced CD4+ T cells when encountering SARS-CoV-2 and other emerging variants.

Additional Research Insights

Another study from the Johns Hopkins School of Medicine further emphasized the importance of the CD4+ T cell response to both SARS-CoV-2 and common cold coronaviruses. This research assessed the T cell responses to spike proteins in both recovered COVID-19 patients and unexposed individuals. Notably, 65% of participants exhibited memory CD4+ T cells that recognized spike proteins from both SARS-CoV-2 and at least one common cold coronavirus.

Conclusion

The cross-recognition of spike proteins by CD4+ T cells suggests that mRNA-based COVID-19 vaccines may provide protection against SARS-CoV-2 variants. However, further studies are necessary to fully understand the extent of this protection against emerging variants.

References

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.