Written By: Longjam Dineshwori | Updated : July 5, 2021 12:57 PM IST
Several variants of SARS-CoV-2 have been emerging and circulating around the world. The B.1.1.7 (Alpha), B.1.351 (Beta), B.1.617.2 (Delta) and P.1 (Gamma) variants are classified as variants of concern. The Delta variant, which was first detected in India last October, is the "most transmissible" of all the variants identified so far, according to the World Health Organisation (WHO). The UN health agency has confirmed that the Delta variant has been detected in 96 countries and it is becoming the dominant strain worldwide. This has raised concerns on whether the approved vaccines can protect us from the Delta variant. The good news is that several vaccine makers, including Moderna and Pfizer, have claimed that their vaccines are highly effective against most prevalent Variants of Concern.
Now, a new study by researchers at La Jolla Institute for Immunology (LJI) have found that Moderna and Pfizer-BioNTech vaccines can prime T cells to fight SARS-CoV-2 variants. It includes data on four of the most prevalent VOCs: Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1) and Epsilon (B.1.427/B.1.429).
The study has now been expanded to a larger panel of variants, including the Delta (B.1.617.2) variant, which became prevalent after this study had been initiated.
They found that both CD4+ "helper" T cells and CD8+ "killer" T cells from people who have recovered from COVID-19 or received the Moderna or Pfizer-BioNTech vaccines can still recognize several concerning SARS-CoV-2 variants. Further, the study also suggests that the impact of mutations found in the variants of concern is limited.
Several studies have linked Variants of Concern (VOCs) to lower levels of virus-fighting antibodies. But the new study showed that even if there is a decrease in antibodies, the T cells remain largely unaffected and the two mRNA vaccines still work, stated LJI Instructor Alba Grifoni, Ph.D.
However, the Johnson & Johnson/Janssen COVID-19 vaccine was not included in the study because it was not available when the study was launched.
For the study, the researchers analyzed T cells from people who had recovered from COVID-19, people who had received either the Moderna or Pfizer-BioNTech vaccines, and people who were never exposed to SARS-CoV-2. The researchers wanted to see whether people with T cells trained to recognize the "ancestral lineage" of SARS-CoV-2 strain would also recognize the new variants. So, they tested T cell responses from the donor groups against four prominent VOCs: Alpha, Beta, Gamma and Epsilon.
The researchers found that both recovered patients and those who had received either Moderna or Pfizer-BioNTech vaccines had cross-reactive T cells that could target these variants.
Based on their findings, study co-author and LJI Professor Shane Crotty, Ph.D., stressed the importance of enlisting T cells in fighting SARS-CoV-2.
Crotty noted that while all the approved COVID vaccines are able to make antibodies that stop SARS-CoV-2 infections, some of them do less well at stopping infections from variants. "You can think of T cells as a backup system: if the virus gets past the antibodies -- if you have vaccine T cells the T cells can probably still stop the variant coronavirus infection before you get pneumonia," he said, as quoted by Science Daily.
He suggested incorporating T cell targets into future COVID vaccines to make sure future variants can't escape the vaccines.
Grifoni, on the other hand, suggested that future "booster" shots could increase immunity by prompting the body to produce more antibodies against the variants and/or by adding additional parts of the virus recognized by T cells. This research also indicates that a pan-coronavirus vaccine is feasible, added Grifoni.
The results of the study were published online recently in Cell Reports Medicine.
