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28th March 2022 (6 Topics)

T cell immune responses seen a year after infection


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


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.

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