Figure 5.

Evidence of sustained cellular inflammation after mild SARS-CoV-2 infection. (a) There was a trend towards a decreasing ratio of myeloid to lymphoid cells after SARS-CoV-2 infection, compared to individuals recovered from other infections, which was driven by a decrease in circulating neutrophils (b). Although total monocyte numbers did not change after infection (c), surface expression of the migratory markers CX₃CR₁ and CCR2 decreased transiently (d). Concurrent increases in surface expression of the migration and activation marker CD11b implies that the monocytes were activated. (e) Correlation analysis (Spearman’s correlation) of SARS-CoV-2 specific CD4⁺ and CD8⁺ T-cell responses with measures of monocyte activation and migratory potential. Multiple group comparisons in (a–d) were tested using Welch’s One-Way ANOVA and the Games–Howell post-hoc test; in (a–c) bars are presented as mean ± standard deviation, and each dot indicates a participant. The spread of expression of monocyte surface markers in d was visualized by concatenating uncompensated CD45⁺CD19⁻CD3⁻CD56⁻CD11b⁺HLADR⁺CD14⁺ events in FlowJo for each infection group prior to overlaying geometric mean fluorescence intensity expression data from all participants onto the same histogram plot. Other respiratory infection (grey) n = 11, 1–3 months after COVID-19 infection (red) n = 14, 6–9 months from COVID-19 infection (pink) n = 8. ns—not statistically significant. Data in (e) were assessed with the rcorr function in the Hmisc package in R, and only statistically significant associations are shown. * p < 0.05.