Abstract Rationale The adverse health effects of combustible cigarette smoke are well-established, but the impact ofelectronic cigarette (e-cigarette) use remains less clear. A considerable proportion of e-cigarette usersalso smoke conventional cigarettes (dual use), potentially compounding respiratory risk. Bothexposures modulate systemic and pulmonary inflammation, which may alter host defenses againstrespiratory viruses. Influenza continues to cause significant morbidity among smokers, and emergingevidence suggests that e-cigarette users may also be vulnerable. However, data on dual exposures arescarce. This study examined how prior single or combined exposure to cigarette smoke and e-cigaretteaerosols influences survival, viral burden, and immune responses during lethal influenza A virusinfection in mice. Methods Female BALB/c mice (7-8 weeks old) were exposed to cigarette smoke, e-cigarette aerosols, or bothusing a whole-body inhalation system (SciReq, Emka). E-cigarette aerosols included: (1) propyleneglycol/vegetable glycerin (PG/VG, 30/70%), (2) PG/VG with nicotine salts (59 mg/mL), and (3) JUUL™Tobacco pods (59 mg/mL nicotine). Cigarette smoke exposures used 3R4F reference cigarettes. Miceunderwent daily exposures (2 h/day, 8 weeks); dual-use groups received 1 h of each inhalant. Air-exposed mice served as controls. After exposure, animals were infected intranasally with influenzaA/PR/8/34 (H1N1) at the LD50 dose. Survival, body weight, and immune parameters were assessed.Viral titers, immune cells and cytokines were quantified at day 7 post-infection, and flow cytometry wasused to evaluate immune cell recruitment and activation in lungs, bronchoalveolar lavage (BAL), andmediastinal lymph nodes (MLNs). Results All exposure groups exhibited comparable early weight loss after infection, but air controls showed theslowest recovery. Survival was lowest in air (50%) and cigarette smoke groups (84%), while PG/VG,JUUL, and dual-use groups achieved 100% survival. Viral titers were similar across groups. Cytokineanalysis revealed reductions in IFNβ, IFNλ, IFNγ, and IL-10 in dual-exposed mice, and decreasedIFNβ/IFNλ in cigarette smoke exposure. Amphiregulin expression was uniquely reduced in dual users.Cigarette smoke lowered pulmonary CD4+ T-cell counts, and JUUL exposure increased BAL B cells.Macrophage and neutrophil activation profiles varied across exposure types, and MLNs showedreduced CD4+ and CD8+ T cells in all inhalant-exposed mice. Conclusions Single and dual exposures to e-cigarettes and cigarette smoke alter immune profiling and survivalduring lethal influenza infection. Despite similar viral clearance, the data suggest an exposure-inducedimmunomodulatory state with potential impairment of adaptive T-cell responses. Further studies areneeded to define the mechanisms underlying these differential outcomes. This abstract is funded by: TRDRP and NIH
Silva et al. (Fri,) studied this question.