T cell immune responses seen a year after infection

Context

A new study from Wuhan, evaluates the protective effect of memory T cell immune responses against severe disease 12 months after primary infection.

About

Key Findings:

Independent of severity:
It is found that neutralising antibodies were detectable even 12 months after infection in “most individuals”, and it remained stable 6-12 months after initial infection in people younger than 60 years.
The researchers found that multifunctional T cell responses were detected for all SARS-CoV-2 viral proteins tested.
Neutralising antibodies:
SARS-CoV-2-specific neutralising antibody and T cell responses were retained 12 months after initial infection.
Neutralising antibodies to the D614G, Beta, and Delta were reduced compared with those for the original strain, and were diminished in general.
Memory T cell responses to the original strain were not disrupted by new variants.
Robustness of T cells:
The study reveals the durability and robustness of the T cell responses against variants, including Delta, even after one year of infection.
Most importantly, the robust and longstanding T cell responses were seen in people who have not been reinfected or vaccinated.
This would mean even in the absence of vaccination, a person who has been infected by the virus even one year ago would have robust immune responses, which would offer protection against disease progressing to a severe form requiring hospitalisation.
Lack of studies:
No studies have been done to evaluate if booster doses improve T cell immune responses, which is the most important criterion of vaccination.
Response to strains
A year after infection, 82% individuals had neutralising antibodies against the original strain from Wuhan, China.
In contrast, only 48% had neutralising antibodies against D614G,
23% had neutralising antibodies against the Beta variant, and
49% had neutralising antibody responses against the Delta variant.

About T cell:

T cells are a part of the immune system that focuses on specific foreign particles.
Rather than generically attack any antigens, T cells circulate until they encounter their specific antigen.
As such, T cells play a critical part in immunity to foreign substances.
T cells are part of the immune system and develop from stem cells in the bone marrow.
They help protect the body from infection and may help fight cancer.
Also called T lymphocyte and thymocyte.