Fig. 1

Time of infection affects survival in influenza A virus (IAV) disease. Experimental design: two groups of mice were maintained in 12 h light: dark cycles. Mice were infected with 40 PFU of IAV (PR8; H1N1) intransally (i.n.) at either the start of the light cycle (ZT23; ZT0 being the time at which light go on in a 12 h LD cycle) or at the start of the dark cycle (ZT11). Mice infected at ZT11 were always weighed and scored at ZT11 at serial time points following infection and likewise for ZT23 group. This ensured that the time from infection to evaluation was identical for both groups. a Survival curves are a composite of three independent experiments [total n = 8/control group; n = 20–24/IAV group, log-rank (Mantel–Cox) test, p < 0.0001]. b Disease progression is expressed as the percent of weight change following IAV infection. c Disease progression was also measured as clinical scores. The data represented as median ± SEM (total n = 17 per group; Student’s t test, *p < 0.05, **p < 0.01, ***p < 0.001). d Two groups of mice were maintained in constant darkness for 72 h, and were infected i.n. with 40 PFU of IAV (PR8) either at the times corresponding to start of the light cycle (CT23) or the start of dark cycle (CT11). Survival curves composite of two independent experiments [total n = 8–12 per group, log-rank (Mantel–Cox) test, *p < 0.05]. e, f Experimental design: Bmal1^fl/fl ERcre⁺ mice and their cre⁻ littermates were treated with tamoxifen at 6–8 weeks of age, and acclimatized to reverse cycles of 12 h LD for 2 weeks. Thereafter, they were maintained in constant darkness for 2–4 days prior to administering IAV (PR8) at CT23 and CT11. e Survival (f) weight change trajectory [n = 12–13 in cre⁺ group and n = 41, 47 in cre⁻ group from three independent experiments]. Compiled data are expressed as mean ± SEM in panel b and f. Source data are provided as a Source Data file