Scientists recently expressed hope that a group of immune cells known as T cells, that can target and destroy cells that are infected by the virus, could provide some resistance to COVID-19, even if antibodies turn out less efficient at fighting the illness.
In connection to this, worries over coronavirus strains that might be partly resistant to antibody defenses have stimulated renewed interest in other immune reactions that shield from viruses.
Researchers have picked apart the available data, searching for indications that T cells could help in maintaining lasting immunity.
According to biotechnology analyst, Daina Graybosch, from the New York City-based investment bank SVB Leerink, "We know the antibodies are" probably less efficient, although maybe, "T cells can save us." She added, it's making sense biologically and even though they don't have the data, "we can hope."
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'Killer' T Cells
Along with antibodies, the immune system is producing a battalion of T cells that are capable of targeting viruses.
Some of these, identified as the CD8+ T cells or the killer T cells, search for and kill cells that are infested with the virus. Others, identified as CD4+ T cells or helper T cells on the other hand, are essential for various functions, which include triggering the antibody production and killer T cells.
T cells do not avert infection as they kick into action only after a virus has penetrated the body. However, they are essential for clearing an infection that has already begun.
In the COVID-19 case, according to immunologist Annika Karlsson, from the Karolinska Institute in Stockholm, killer T cells could mean "the difference between a mild infection and a severe one" that needs hospital confinement.
The immunologist added, if these can cell virus-infected cells prior to their transmission from the upper respiratory tract, it will affect "how sick you feel."
The could lower transmission too, by limiting the amount of virus spreading in an infected individual which means, that he sheds lesser virus elements into the community.
Potentially More Resistant than Antibodies
As indicated in the study, T cells could potentially be more resistant compared to antibodies to threats postured by emerging variants.
Studies by the California-based La Jolla Institute for Immunology immunologist Alessandra Sette and his colleagues have presented that people who have been infected with SARS-CoV-2 usually produce T cells that target at 15 to 20 different remains of coronavirus proteins
Studies by Sette and his colleagues have shown that people who have been infected with SARS-CoV-2 typically generate T cells that target at least 15-20 different fragments of coronavirus proteins.
However, which protein scraps are used as targets can differ widely from one person to another. Meaning, a population will produce a large variation of T cells that could entrap a virus.
Sette explained, that's making it quite hard for the virus "to mutate and escape cell recognition," not like the occurrence for antibodies.
Therefore, when the lab tests showed that the 501Y.V2 variant detected in South Africa, also identified as B.1.351 is partly resistant to antibodies raised as protection from previous coronavirus variants, scientists wondered if T cells could be less susceptible to mutations.
Early Findings
Early findings propose that this might be the case. In a preprint that came out in early February, study investigators found that most T-cell reactions to COVID-19 vaccinations or previous infections are not getting target regions that were mutated in two newly-discovered coronavirus strains, which include 501Y.V2.
Sette said, his team has initial evidence too, that the T-cell responses' vast majority are not likely to be affected by the mutations.
If T cells stay active against the said variant, they might shield against severe illness, elaborated John Wherry, immunologist at the Philadelphia-based University of Pennsylvania immunologist John Wherry.
However, it is difficult to know from available data thus far, cautioned Wherry. He added, they are trying to infer a lot of "scientific and mechanistic information from data."
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