T Cell Immunity in SARS-CoV-2 Infection and COVID-19

T cell immunity plays a pivotal role in the host defence against SARS-CoV-2, complementing humoral responses and contributing to viral clearance, disease modulation and long-term protection. Upon infection, antigen-presenting cells process viral proteins and present peptide fragments via human leukocyte antigen (HLA) molecules to T cells, triggering activation and proliferation of CD4+ helper and CD8+ cytotoxic subsets. CD4+ T cells orchestrate immune coordination through cytokine production and help to B cells, while CD8+ T cells directly lyse infected cells. Memory T cells, established after acute infection or vaccination, can persist for months to years, mediating rapid recall responses and reducing disease severity upon re-exposure. Heterogeneity in T cell phenotype and function reflects clinical outcomes: strong, polyfunctional T cell responses associate with mild disease, whereas dysregulated or insufficient T cell activation correlates with severe pathology. Age-related decline in T cell repertoire diversity, comorbidities and viral variants can impair T cell responses, underscoring the need for vaccines and immunotherapies that elicit broad and durable cellular immunity.

Research from Nature Portfolio

Studies have highlighted age and comorbidity as critical determinants of T cell responsiveness. Analysis in older adults receiving inactivated SARS-CoV-2 vaccines revealed delayed neutralising antibody kinetics and diminished CD8+ T cell expansion, linked to reduced antigen presentation capacity and narrowed T cell receptor repertoire. An mRNA-based vaccine strategy encoding conserved HLA-binding epitopes beyond spike antigen demonstrated potent CD8+ T cell responses in humanised mice and non-human primates, offering cross-variant protection and emphasising the importance of targeting multiple viral proteins. Investigations into vaccine responses in high-risk populations showed that chronic conditions such as diabetes and renal disease modulate CD4+ and CD8+ T cell frequencies and function, in part through altered antibody glycosylation and inflammatory cytokines, guiding the optimisation of vaccination protocols for vulnerable groups.

T Cell Immunity in SARS-CoV-2 Infection and COVID-19 publication trend

The graph below shows the total number of articles in t cell immunity in sars-cov-2 infection and covid-19 across all publications each year (not limited to Nature Index journals).

Technical terms

CD4+ T cell: A helper T cell subset that assists other immune cells by secreting cytokines and providing support to B cells.

CD8+ T cell: A cytotoxic T cell subset that kills virus-infected cells by recognising antigenic peptides presented on HLA class I molecules.

T follicular helper (TFH) cell: A specialised CD4+ T cell population that provides critical help to B cells during germinal centre reactions to promote antibody affinity maturation.

Memory T cell: A long-lived T cell that persists after an initial immune response and mounts a rapid, robust response upon re-encounter with the antigen.

Human leukocyte antigen (HLA): Molecules on antigen-presenting cells that display peptide fragments to T cells, central to the specificity of adaptive immunity.

Interferon-gamma release assay (IGRA): A test that measures interferon-gamma production by T cells in response to specific antigens, used to assess cellular immunity.

References

1. Insufficient epitope-specific T cell clones are responsible for impaired cellular immunity to inactivated SARS-CoV-2 vaccine in older adults. Nature Aging (2023).
2. An mRNA-based T-cell-inducing antigen strengthens COVID-19 vaccine against SARS-CoV-2 variants. Nature Communications (2023).
3. Robust and prototypical immune responses toward COVID-19 vaccine in First Nations peoples are impacted by comorbidities. Nature Immunology (2023).
4. Robust T Cell Immunity in Convalescent Individuals with Asymptomatic or Mild COVID-19. Cell (2020).
5. SARS-CoV-2 spike-specific TFH cells exhibit unique responses in infected and vaccinated individuals. Signal Transduction and Targeted Therapy (2023).
6. Evaluation of SARS-CoV-2-Specific T‑Cell Activation with a Rapid On-Chip IGRA. ACS Nano (2023).
7. Antigen-Specific Adaptive Immunity to SARS-CoV-2 in Acute COVID-19 and Associations with Age and Disease Severity. Cell (2020).