A study discovered that the magnitude and quality of a key immune cell’s response to two doses of the Pfizer-BioNTech COVID-19 vaccine were significantly lower in individuals with earlier SARS-CoV-2 infection compared to individuals without previous infection.
Colorized scanning electron micrograph of a cell (red) infected with the Omicron strain of SARS-CoV-2 virus particles (blue), isolated from a patient sample. Image Credit: National Institute of Allergy and Infectious Diseases. Furthermore, the extent of this key immune cell that identifies the SARS-CoV-2 spike protein in unvaccinated individuals with COVID-19 was significantly lower than in vaccinated individuals who had never been infected.
Notably, people who recover from SARS-CoV-2 infection and then get vaccinated are better protected than unvaccinated people. These observations, which indicate that the virus interferes with a vital immune-cell response, were published today in the journal Immunity .
The research was funded in part by the National Institute of Allergy and Infectious Diseases (NIAID), which is part of the National Institutes of Health , and was guided by Mark M. Davis, PhD.
Dr Davis is the Director of Stanford University School of Medicine’s Stanford Institute for Immunity, Transplantation, and Infection and a Professor of microbiology and immunology. In addition, he is a Howard Hughes Medical Institute Investigator.
Dr Davis and co-workers created a highly sensitive tool to study how immune cells known as CD4+ and CD8+ T cells respond to SARS-CoV-2 infection and vaccination. These cells help to prevent COVID-19 by coordinating the immune system’s response to the virus and killing infected cells.
The tool was created to detect T cells that aim any of the dozens of distinct regions on the virus’ spike protein, and other viral regions. Parts of the SARS-CoV-2 spike protein are used in the Pfizer-BioNTech vaccine to evoke an immune response without causing infection.
The researchers looked at CD4+ and CD8+ T-cell responses in blood samples from three different groups of volunteers. One group had never had SARS-CoV-2 infection and obtained two doses of the Pfizer-BioNTech COVID-19 vaccine.
The second group had been infected with SARS-CoV-2 and got two doses of the vaccine. The third group had COVID-19 and had not been vaccinated.
The vaccine induced robust CD4+ and CD8+ T-cell responses to the virus’ spike protein in individuals who had never been infected with SARS-CoV-2, according to the researchers. Furthermore, these T cells produced a variety of cell-signaling molecules known as cytokines, which attract other immune cells, including antibody-producing B cells, to combat pathogens.
Individuals who had been infected with SARS-CoV-2 prior to vaccination, on the other hand, produced significantly fewer spike-specific CD8+ T cells—and with less functionality—than vaccinated people who had never been infected. Furthermore, unvaccinated people with COVID-19 had significantly lower levels of spike-specific CD8+ T cells than vaccinated people who had never been infected.
Taken together, the results indicate that SARS-CoV-2 infection impacts the CD8+ T cell response, an effect similar to that observed in previous studies demonstrating long-term immune system damage after infection with viruses like hepatitis C or HIV.
According to the researchers, the latest findings emphasize the need to develop vaccination strategies that particularly enhance antiviral CD8+ T cell responses in people who have previously been infected with SARS-CoV-2.
Source:
Journal reference:
Gao, F., et al . (2023). Robust T cell responses to Pfizer/BioNTech vaccine compared to infection and evidence of attenuated peripheral CD8+ T cell responses due to COVID-19. Immunity . doi.org/10.1016/j.immuni.2023.03.005 .
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