Fig. 3: 2nd hit susceptibility of offspring from influenza infected dams to early life infections.

a Second-hit experiments were performed in 2-week-old offspring using influenza B virus (IBV) or Methicillin-resistant Staphylococcus aureus (MRSA) for a respiratory challenge. b Survival of 2-week-old male offspring born to IAV-infected dams (n = 11 [day 3], n = 9 [day 6], n = 7 [day 14]) or born to control treated dams with polyinosinic:polycytidylic acid (poly(I:C))-treated (n = 11 [day 3], n = 9 [day 6], n = 7 [day 14]) or PBS (n = 9 [day 3], n = 7 [day 6], n = 5 [day 14]) after infection with 10⁵ plaque forming units (PFU) of IBV; p = 0.0355. c Survival of 2-week-old female offspring born to IAV-infected dams (n = 13 [day 3], n = 11 [day 6], n = 9 [day 14]) or born to control treated dams with poly(I:C)-treated (n = 11 [day 3], n = 9 [day 6], n = 7 [day 14]) or PBS (n = 8 [day 3], n = 6 [day 6], n = 4 [day 14]) after infection with 10⁵ PFU of IBV. Survival was monitored in three independent experiments. d 2-week-old offspring (both sexes) born to poly(I:C)-treated (n = 21 [day 1], 14 [day 3], 7 [day 6]) or IAV-infected (n = 55 [day 1], 34 [day 3], 16 [day 6]) dams were infected with 10⁸ CFU of MRSA; p = 0.0167. Offspring born to PBS-treated dams (n = 38 [day 1], 25 [day 3], 12 [day 6]) were used as controls. Survival was monitored on day 1, 3 or 6 p.i. in three independent experiments. e–g Cytokines (TNF (e), IL-6 (f), and IL-2 (g)), p = 0.0034 poly(I:C), p = 0.0219 measured by Luminex assay in lungs of 2-week-old offspring (both sexes) born to PBS- or poly(I:C)-treated or IAV-infected offspring (n = 4) after infection with 10⁵ PFU of IBV measured at 1, 3, or 6 d p.i. h–j Cytokines (TNF (h), IL-6 (i), and IL-2 (j)) measured by Luminex assay in lungs of 2-week-old offspring (both sexes) born to PBS- (n = 10) or poly(I:C)-treated (n = 7) or IAV-infected offspring (n = 11) after infection with 10⁸ CFU of MRSA measured at 1, 3, or 6 d p.i. k IBV lung titer in 2-week-old offspring (both sexes) born to PBS-, poly(I:C)-treated, or IAV-infected (n = 4) dams, measured on day 1, 3 (p = 0.0270), and 6 p.i. is shown as fold-change in lung titers compared to the respective PBS group of the indicated time point. l MRSA lung titer in 2-week-old offspring (both sexes) born to PBS- (n = 10 [1 d p.i.], 10 [3 d p.i.], 7 [6 d p.i.]), poly(I:C)-treated (n = 7 [1 d p.i.], 7 [3 d p.i.], 4 [6 d p.i.]) or IAV-infected (n = 11 [1 d p.i.], 13 [3 d p.i., p = 0.0189], 9 [6 d p.i., p = 0.0223]) dams, measured on days 1, 3, and 6 p.i. is shown as fold-change in lung titers compared to the respective PBS group of the indicated time point. All n represent number of male and/or female offspring from respective groups. Groups were merged for clarity if no difference between males and females was observed. Data in (e–j) are presented as mean and SD. Different groups of male offspring are depicted in dark circles (PBS, medium squares (Poly(I:C)) or light triangles (IAV) in blue colors and female offspring in red colors. Different groups of offspring that were not stratified by sex are depicted in orange colors with the same icons. Cytokine levels that were below detection limit were set to the kit’s lower detection limit of 1 pg/g. The statistical significance was calculated by Welch’s t test (two-tailed) (e–j, k, l) without multiple comparison or Log Rank test (b–d) (*p < 0.05, **p < 0.01). PBS-treated groups were used as a reference and compared to IAV-infected groups in all statistical analyses unless stated otherwise. Source data are provided as a Source Data file.