Cigarette smoke impacts immune inflammatory responses to influenza in mice

Rationale: Studies have shown that cigarette smoke impacts respiratory host defense mechanisms; however, it is poorly understood how these smoke-induced changes impact the overall ability of the host to deal with pathogenic agents. Objective. The objective of this study was to investigate the impact of mainstream cigarette smoke exposure on immune inflammatory responses and viral burden after respiratory infection with influenza A. Methods: C57BL/6 mice were sham- or smoke-exposed for 3 to 5 mo and infected with either 2.5 x 10(3) pfu (low dose) or 2.5 x 101 pfu (high dose) influenza virus. Measurements and Main Results: Although smoke exposure attenuated the airway's inflammatory response to low-dose infection, we observed increased inflammation in smoke-exposed compared with sham-exposed mice after infection with high-dose influenza, despite a similar rate of viral clearance. The heightened inflammatory response was associated with increased expression of tumor necrosis factor-alpha, interleukin-6, and type 1 IFN in the airway, and increased mortality. Importantly, smoke exposure did not interfere with the development of influenza-specific memory responses; sham- and smoke-exposed animals were equally protected upon viral rechallenge. Conclusion: Our study suggests that, in mice, cigarette smoke affects primary antiviral immune-inflammatory responses, whereas secondary immune protection remains intact.