- A new study has examined whether T cells induced by COVID-19 vaccines recognize variants of the SARS-CoV-2 virus.
- In addition to neutralizing antibodies and B cells, T cells play a crucial role in the immune response against disease.
- The study results suggest that SARS-CoV-2 variants of concern – including Delta and Omicron – are effectively recognized by T cells in the body.
In the body, antibodies recognize and destroy viruses before they cause infection in cells, while T cells are responsible for destroying cells with a viral infection.
In a recent study, scientists discovered that COVID-19 vaccines cause the body to make long-lasting T cells that are effective against the SARS-CoV-2 virus and its variants.
The results suggest that T cells are the key to limiting SARS-CoV-2 infection and may play a potential role in the prevention of serious diseases in the case of new variants.
The study is published in the journal
Co-study author Dr. Alba Grifoni, Ph.D.a scientist from the La Jolla Institute for Immunology, CA, explained the motivation behind the study to Medical news today:
“We have studied the role of immune responses (including neutralizing antibodies) and T cells in particular in SARS-CoV-2 since the beginning of the pandemic, first in infection and then in vaccination.”
“[SARS-CoV-2] variants are less susceptible to neutralizing antibodies, and vaccines have been relatively less effective in preventing infection from variants, “Dr. Grifoni explained, noting that vaccines are still” effective in preventing serious disease and hospitalization. “
“We wanted to see if variants in general and Omicron in particular were still effectively recognized by T cells,” she added.
“If this line of defense is still largely intact, it would fit with the fact that vaccines are still able to prevent serious illness in the case of Omicron infections,” concluded Dr. Grifoni.
The new study included 96 participants who received vaccines that were approved for use in the United States.
These individuals received the Pfizer BioNTech, Moderna, Johnson & Johnson, or Novavax vaccines.
The researchers collected blood samples from participants at four time intervals to examine how long T cells recognize SARS-CoV-2 variants. These intervals were as follows:
- 2 weeks after the first dose
- 2 weeks after the second dose
- 3.5 months after the last dose
- 5-6 months after the last dose
In addition, the trial leaders also recruited individuals who were improving after mild COVID-19. These participants served as a control group.
Finally, according to the availability of samples, the research team designed one
The researchers observed that 6 months after vaccination, a large majority of T cell responses were still conserved against the Omicron variant.
Interestingly, they also noted that robust T cell responses remained the same regardless of which vaccine was administered or the variants encountered.
In contrast, the research team noticed a significant overall decrease in the activities of B cells and neutralizing antibodies across all SARS-CoV-2 variants.
These results led the researchers to conclude that “most of the T cell responses may play an important role as a second-level defense against different variants.”
This view is consistent with the authors of another paper who looked at T cell responses after SARS-CoV-2 infection and COVID-19 vaccination. They write that:
“T-cell responses are an important weapon against viral infections, which in addition to helping with B-cell activation to generate antibodies, help provide protection against disease by eliminating virus-infected cells.”
“SARS-CoV-2 T cell responses induced by either natural infection or vaccines have been associated with rapid viral clearance and reduced disease severity, even when the neutralizing antibody response is reduced or absent.”
“Thus, if SARS-CoV-2 T cell responses persist, they are likely to help limit the severity of the disease in infections caused by Omicron, which apparently escapes neutralizing antibodies.”
A similar view is also shared Prof. Eric Topolfounder and director of the Scripps Research Translational Institute, CA.
As Prof. Topol explained Underlayis the main reason why Omicron has a lower frequency of hospitalizations, not that the SARS-CoV-2 virus is less virulent, but rather because of the wall of immunity that the body has built up through the pandemic.
In a further comment, he added that the body’s “last line of defense” is the T-cell memory that previous COVID-19 disease and vaccinations help create.
“[The T cell memory response] is not fast, does not protect against the first infection in our upper respiratory tract, but intervenes as needed to keep it there, ”says Prof. Topol, pointing out that“ this layer seems to be the main reason why Omicron seems mild. “
In a conversation with MNTDr. Grifoni reported several limitations of their research.
For example, they explained that their study did not look at natural SARS-CoV-2 infection. As a result, researchers do not know “how conserved T cell responses are in humans [who had a natural infection] and had COVID-19 before and [now have an Omicron infection]. “
In addition, Dr. Grifoni that their sample size was limited to the San Diego areas of the United States and therefore there is a bias in geographical location.
However, the study authors explained that they collaborated with other independent research groups, and they all reached “the same conclusions about T cells and Omicron.”
Nevertheless, they comply with the established COVID-19
As the study authors explain, “[Although] SARS-CoV-2 vaccines still provide an answer that helps limit the severity of the disease, [this protection] improved by getting a booster vaccination. ”
All things considered, the results of the study provide a crucial basis for future studies to build on.