Figure 1

Caging enrichment and influenza vaccination timeline. After arriving at the husbandry facility, 6-wk-old male BALB/c mice were housed in standard control caging for 14 d (day −14 to 0) for acclimatization. At d 0, mice were placed, five per cage, into either standard control caging (n = 20) or enriched EE caging (n = 20) for either 56 or 63 d. At d 28, all mice were injected intramuscularly with trivalent influenza vaccine (1 µg HA in 50 µL PBS) or vehicle (50 µL PBS). At 28 d after primary vaccination, half of the animals were euthanized for blood and tissue collection and half were given a second intramuscular vaccination (boost). Remaining animals were euthanized for blood and tissue collection 7 d after boost.