Durability and Cross-Reactivity of Memory T-Cell Responses to SARS-CoV-2 Variants

Recent Study on T-Cell Response to SARS-CoV-2

A recent study published in the journal Cell Host & Microbe has shed light on the T-cell response to SARS-CoV-2, specifically focusing on the memory T-cell responses to the hypermutated BA.2.86 variant. The research included 39 healthcare workers who had a history of vaccination and infection. The primary finding was that the majority of participants demonstrated a robust CD4+ T-cell response to the ancestral spike protein even after 1.5 years since their last infection.

Robust T-cell Memory Over Time

Remarkably, the study also highlighted the preservation of T-cell responses against Omicron variants and the maintenance of T-cell memory over time. This suggests a robust memory T-cell response in healthcare workers more than 1.5 years post-Omicron wave. The findings point towards the fact that hybrid immunity results in an accumulation of spike- and non-spike-specific T-cells, with preserved recognition of highly mutated variants.

Results from Blood Samples

For the study, blood samples were obtained from the healthcare workers in mid-late 2023. The researchers measured cytokine production in response to spike peptide pools of the ancestral strain and Omicron variants. The results showed that an impressive 95% of participants mounted a robust CD4 T cell response to the ancestral spike protein. However, the CD8 T cell responses to the ancestral spike protein were lower, but preserved against Omicron variants. Additionally, T cell responses to nucleocapsid and membrane proteins were detected in 35 participants.

Memory T Cell Subsets

The researchers identified four spike-specific memory T cell subsets, concluding that these findings indicate robust memory T cell responses in healthcare workers. This robustness could be related to recurrent SARS-CoV-2 exposure, expanding T cell memory pool, or durable responses lasting from before infection and vaccination.

Dual IFN γ and IL 2 Detection

The study also aimed to assess the dual IFN γ and IL 2 detection using a SARS CoV 2 specific fluorescence ELISPOT in patients undergoing acute disease during convalescence and after vaccination. The results show that IFN γ in combination with IL 2 increases response detection in acute and convalescent individuals. Additionally, IFN γ detection can be a useful biomarker for monitoring severe acute patients.

Effectiveness of Memory T Cells

Memory T cells have proven to be effective in recognizing the SARS-CoV-2 hypermutated BA.2.86 variant. This is a significant finding as it indicates that our immune system's memory T cells can effectively identify and respond to highly mutated variants of the virus.

Immunity Response in Cancer Patients

Another study conducted on patients with late-stage lung cancer who were vaccinated against the SARS-CoV-2 virus found that booster vaccines induced a CD8 T cell response against the ancestral SARS-CoV-2 strain and the Omicron variant in both non-cancer subjects and patients with lung cancer. However, only a marginal induction was detected for CD4 T cells. This highlights the need for heightened protective measures for patients with cancer to minimize the risk of breakthrough infection with the Omicron and other future variants.