Identification of aging-associated immunotypes and immune stability as indicators of post-vaccination immune activation

Abstract

Immunosenescence describes immune dysfunction observed in older individuals. To identify individuals at-risk for immune dysfunction, it is crucial to understand the diverse immune phenotypes and their intrinsic functional capabilities. We investigated immune cell subsets and variation in the aging population. We observed that inter-individual immune variation was associated with age and cytomegalovirus seropositivity. Based on the similarities of immune subset composition among individuals, we identified nine immunotypes that displayed different aging-associated immune signatures, which explained inter-individual variation better than age. Additionally, we correlated the immune subset composition of individuals over approximately a year as a measure of stability of immune parameters. Immune stability was significantly lower in immunotypes that contained aging-associated immune subsets and correlated with a circulating CD38 + CD4+ T follicular helper cell increase 7 days after influenza vaccination. In conclusion, immune stability is a feature of immunotypes and could be a potential indicator of post-vaccination cellular kinetics.

FIGURE 1

VITAL vaccination study design

FIGURE 2

Age strongly correlates to immune cell subset percentages and absolute numbers. (a) Spearman correlations between age and immune cell subsets (flow cytometry immune phenotyping, percentage and absolute number). Spearman correlation coefficients (r) and p‐values (Bonferroni correction) are reported. Color gradient represents r. Dashed lines present the cut offs (−0.2 and 0.2 for r, 0.001 for p‐value). (b) Coefficient of variation for immune cell subset percentages and absolute numbers. The coefficient of variation is calculated for each immune subset across the cohort as a ratio of standard deviation to mean. (c) Comparison of coefficient of variances between percentage and absolute number of each immune cell subset (Wilcoxon signed‐rank test). (d–k) Spearman correlations between selected immune cell subsets and age are plotted. The area around the loess fitted regression line describes 95% confidence interval (p‐values are not false discovery rate corrected)

FIGURE 3

Age and CMV‐seropositivity is associated with increased inter‐individual immune variation. (a) Projection of 59 immune cell subsets (percentage) with minimal overlap onto the two Principal Components (PC). (b) Contribution of immune cell subsets on PCs. Top 10 contributing immune cell subsets are colored by their square of cosine (cos²). The higher cos² is, the higher contribution of variable on PCs. (c) Comparison of intra‐group similarity (spearman correlation) in age groups, (d) sex differences, (e) CMV‐seropositivity, and (f) EBV‐seropositivity based on percentage and absolute number of immune cell subsets (Dunn's test, Benjamini–Hochberg corrected p‐values)

FIGURE 4

Immunotypes display immune cell subset compositions associated with CMV‐seropositivity and signatures of aging‐associated immune subsets. (a) Boxplot displays age distribution in immunotypes. Immunotypes are ordered by increasing median age. Heatmap shows percentages of 59 immune cell subsets in immunotypes. (b–d) sex, CMV‐seropositivity, and EBV‐seropositivity in immunotypes. Borderline CMV and EBV cases were removed from the plots. (e–i) Boxplots depicting selected immune cell subsets in immunotypes. Significant differences of immune cell subsets between immunotypes are reported in Table S2 (Dunn's test, Benjamini–Hochberg corrected p‐values)

FIGURE 5

Immune stability is associated with immunotypes but not with sex, CMV‐seropositivity, and EBV‐seropositivity. (a) Intra‐individual immune subset correlation which reflects the immune stability ordered from low to high. Each point represents an individual colored by age groups they belong. (b) Spearman correlation between immune stability and age. (c–g) immune stability in age groups, sex, CMV‐seropositivity, EBV‐seropositivity, and immunotypes

FIGURE 6

Circulating CD38+ CD4+ T follicular cell kinetics 7 days after influenza vaccination in age groups and immunotypes (a) circulating CD38+ CD4+ T follicular cells before and 7 days after influenza vaccination in age groups and (b) in immunotypes. (c) Mean CD38+ CD4+ T follicular cell log₂ fold change between before and 7 days after influenza vaccination in immunotypes. (d) Spearman correlation between immune stability and circulating CD38+ CD4+ T follicular cell log₂ fold change between before and 7 days after influenza vaccination