Sara van den Berg

95 4 CMV on influenza infection singed-rank test. Correlations were tested with Spearman’s rank correlation coefficient. For all analyses p values < 0.05 were considered statistically significant. Data were analyzed using GraphPad Prism 8.3 and SPSS statistics 22 for Windows (SPSS Inc., Chicago, IL, USA). RESULTS Characteristics of study population Healthy individuals were on average 59.2±19.1 years old (range 21-82 year) (n=96). They were categorized into young (21-52 years old) (n=34) and old (>60 years old) (n=62) individuals, of whom respectively 55.9% and 59.7% were CMV-infected ( Table 1 ). No significant differences in age or sex were observed between CMV- and CMV+ individuals ( Table 1 ). In addition to healthy individuals, older adults with confirmed influenza virus infection were included in this study (n=72). Also for the influenza virus-infected older adults, no significant differences in age or sex were observed between CMV+ and CMV- individuals ( Table 1 ). The majority of individuals were infected with the H3N2 strain (n=64), while some were infected with the H1N1 strain of influenza (n=8). All individuals in the latter group turned out to be CMV-. Healthy young adults Total (n=34) CMV- (n=15) CMV+ (n=19) Statistics Age (mean±SD) 35.9 ±10.3 35.3±10.8 36.4±10.1 ns Sex (% women) 61.8% 53.3% 68.4% ns CMV-serostatus (CMV+) 55.9% . . . Healthy older adults Total (n=65) CMV- (n=25) CMV+ (n=37) Statistics Age (mean±SD) 71.8±6.5 70.9±6.8 72.5±6.5 ns Sex (% women) 38.5% 33.3% 44.7% ns CMV-serostatus (CMV+) 58.5% . . Influenza virus infected older adults Total (n=72) CMV- (n=35) CMV+ (n=37) Statistics Age (mean±SD) 69.9±6.1 69.2±5.3 70.4±6.9 ns Sex (% women) 41.7% 37.1% 45.9% ns CMV-serostatus (CMV+) 51.4% . . . Influenza virus strain (%H1N1) 11.1% 22.9% 0.0% P=0.002 Table 1. Characteristics of the study population CMV induces an increase in senescence associated markers in the T-cell pool in older adults We assessed the effect of latent CMV infection on the CD8 + T-cell pool of all healthy individuals, by performing a cluster analysis (tSNE) based on memory T-cell markers CD27, CCR7, CD95, CD45RO, and CXCR3, and senescence-associated T-cell markers CD57 and KLRG-1, known to be altered in CMV infection [47]. Cluster analysis indeed conformed the large differences between the CMV-negative (n=40) and CMV-positive (n=56) group ( Figure 1A ), and six different clusters were identified. Clusters 1-3 containing non-senescent CD27 high CCR7 high CD57 low cells are predominantly expressed in CMV-negative individuals ( Figure 1B, Supplementary Figure 1A ). In contrast, clusters 4-6 containing the more