HLA class II–presented SARS-CoV-2 spike protein epitopes (SARS-CoV-2 S HLA-II epitopes)

HLA class II–presented SARS-CoV-2 spike protein epitopes are peptide fragments derived from the SARS-CoV-2 spike protein that are displayed on the surface of antigen-presenting cells by Human Leukocyte Antigen (HLA) class II molecules (Grifoni et al., 2020, Cell). These epitopes are critical for the activation of CD4+ T cells, which orchestrate the adaptive immune response by promoting B-cell antibody production and coordinating cellular immunity (Sette & Crotty, 2021, Cell). In the context of COVID-19, these epitopes are the primary targets for vaccine-induced T-cell responses, as seen with mRNA and viral vector vaccines like BNT162b2 and Ad26.COV2.S (Sahin et al., 2020, Nature). The identification of immunodominant epitopes within the spike protein is essential for monitoring long-term immunity and assessing the impact of viral mutations found in variants of concern (Tarke et al., 2021, Cell Reports Medicine). Because HLA molecules are highly polymorphic, the specific epitopes presented can vary significantly between individuals, influencing the breadth and depth of the immune response (Mateus et al., 2020, Science). These epitopes are also utilized in diagnostic assays, such as ELISpot or intracellular cytokine staining, to measure the efficacy of vaccines and natural infection in generating T-cell memory.

Other names

SARS-CoV-2 spike CD4+ T-cell epitopesMHC class II-restricted spike peptidesSARS-CoV-2 S-protein HLA-II epitopesSpike protein HLA-II restricted antigens

These epitopes are presented by HLA class II molecules on the surface of antigen-presenting cells to CD4+ T cells. The recognition of the epitope-HLA complex by the T-cell receptor (TCR) triggers T-cell activation, leading to the secretion of cytokines and providing essential help to B cells for the production of high-affinity neutralizing antibodies and the generation of long-lived memory cells.