Maternal thirdhand exposure to e-cigarette vapor alters lung and bone marrow immune cell responses in offspring in the absence or presence of influenza infection.

There is increasing evidence that thirdhand exposure to e-cigarette vapor (e-vapor) can have detrimental effects on the lungs. However, whether maternal exposure during pregnancy results in harmful changes to the offspring is unknown. Using two different e-cigarette settings (low vs. high power), BALB/c mice were subjected to thirdhand e-vapor (e-vapor deposited onto towels, towels changed daily) in the absence or presence of nicotine, before, during, and after pregnancy. Male adult offspring were then infected with mouse-adapted influenza A virus (A/PR/8/34 H1N1; Flu) and lung and bone marrow immune cell responses were assessed 7 days postinfection. Maternal thirdhand exposure to low-power (_MLP) or high-power (_MHP) e-vapor with nicotine (_MLP + NIC and _MHP + NIC, respectively) increased the percentage of lung immune cells and neutrophils in the bone marrow. Interestingly, Flu-infected offspring from _MLP + NIC and _MHP + NIC groups had lower percentages of lung alveolar macrophages and more pronounced increases in neutrophils in the bone marrow, when compared with offspring from _MSham Flu controls. Flu infection also decreased the percentage of lung CD4+ T cells and increased the percentage of lung CD8+ T cells, irrespective of maternal exposure (_MLP -/+ NIC and _MHP -/+ NIC). Significantly, both _MLP + NIC and _MHP + NIC resulted in blunted activation of lung CD4+ T cells, but only _MLP + NIC caused blunted activation of lung CD8+ T cells. Together, we show for the first time that maternal thirdhand exposure to e-vapor results in significant, long-lived effects on lung and bone marrow immune cell responses in offspring at baseline and response to Flu infection.NEW & NOTEWORTHY Maternal exposure to environmental residues of e-cigarette use has significant effects on immune cell responses in the lungs and bone marrow of offspring at both baseline and in response to influenza A virus (Flu) infection.