Figure 4.

SARS-CoV-2-Specific CD4+ T Cells Express CD127 and Can Persist for Over 2 Months

(A) A subset of SARS-CoV-2-specific CD4+ T cells express CD127. The indicated cell populations were examined for expression levels of the terminal differentiation marker CD57 and the IL-7 receptor CD127. Numbers correspond to the percentages of the corresponding populations within the gates.

(B) SARS-CoV-2-specific CD4+ T cells can persist for over 2 months. Shown are t-SNE plots of CyTOF datasets of CD4+ T cells from two COVID-19 convalescent donors who were sampled longitudinally at the indicated time points post-infection (infection was defined as the time of testing positive for SARS-CoV-2). Cells shown in gray correspond to total CD4+ T cells from specimens stimulated with anti-CD49d/CD28 in the absence of any peptides. The locations of SARS-CoV-2-specific cells are shown as red contours. The percentage of CD4+ T cells that are SARS-CoV-2 specific is indicated at the bottom right of each plot.

(C) Persistent SARS-CoV-2-specific CD4+ T cells retain CD127 expression. Longitudinal specimens characterized in (B) were analyzed for expression levels of CD57 and CD127. SARS-CoV-2-specific CD4+ T cells are shown as red contours, whereas total CD4+ T cells are shown as gray dots. The percent of SARS-CoV-2-specific CD4+ T cells in the gates is shown at the top right of each plot. Note that the proportions of CD127+ SARS-CoV-2-specific CD4+ T cells do not decrease over time.

(D) SARS-CoV-2-specific CD4+ T cells can proliferate homeostatically in response to IL-7. PBMCs from convalescent donor PID4102 were labeled with CFSE and cultured for 5 days in the absence or presence of IL-7. Thereafter the cells were treated for 6 h with co-stimulation alone or in the presence of overlapping peptides from SARS-CoV-2 spike and then analyzed by flow cytometry. Homeostatic proliferation, as assessed by CFSE dye dilution, only occurred in the presence of IL-7 (top). A subpopulation of CFSE^low cells produced IFNγ in response to peptide stimulation (bottom), demonstrating that cells driven to proliferate by IL-7 treatment included SARS-CoV-2-specific CD4+ T cells. Results are gated on live singlet CD3+CD4+CD8− cells and are representative of one of two donors.

(E) CD127+ SARS-CoV-2-specific CD4+ T cells are distributed similarly as their CD127- counterparts. Shown are t-SNE plots of CD127− (purple) and CD127+ (pink) SARS-CoV-2-specific CD4+ T cells overlaid on total CD4+ T cells treated with co-stimulation alone (gray). Note that, for each donor, CD127+ cells occupy similar regions of t-SNE space as CD127− cells.

(F) CD127+ SARS-CoV-2-specific CD4+ T cells express CXCR5 and ICOS.