Cigarette smokers are at increased risk of acquiring influenza, developing severe disease and requiring hospitalisation/intensive care unit admission following infection. However, immune mechanisms underlying this predisposition are incompletely understood, and therapeutic strategies for influenza are limited.

We used a mouse model of concurrent cigarette smoke exposure and H1N1 influenza infection, colony-stimulating factor (CSF)3 supplementation/receptor (CSF3R) blockade and single-cell RNA sequencing (scRNAseq) to investigate this relationship.

Cigarette smoke exposure exacerbated features of viral pneumonia such as oedema, hypoxaemia and pulmonary neutrophilia. Smoke-exposed infected mice demonstrated an increase in viral (v)RNA, but not replication-competent viral particles, relative to infection-only controls. Interstitial rather than airspace neutrophilia positively predicted morbidity in smoke-exposed infected mice. Screening of pulmonary cytokines using a novel dysregulation score identified an exacerbated expression of CSF3 and interleukin-6 in the context of smoke exposure and influenza. Recombinant (r)CSF3 supplementation during influenza aggravated morbidity, hypothermia and oedema, while anti-CSF3R treatment of smoke-exposed infected mice improved alveolar–capillary barrier function. scRNAseq delineated a shift in the distribution of Csf3⁺ cells towards neutrophils in the context of cigarette smoke and influenza. However, although smoke-exposed lungs were enriched for infected, highly activated neutrophils, gene signatures of these cells largely reflected an exacerbated form of typical influenza with select unique regulatory features.

This work provides novel insight into the mechanisms by which cigarette smoke exacerbates influenza infection, unveiling potential therapeutic targets (e.g. excess vRNA accumulation, oedematous CSF3R signalling) for use in this context, and potential limitations for clinical rCSF3 therapy during viral infectious disease.

吸烟者感染流感、发展为严重疾病以及感染后需要住院/入住重症监护室的风险增加。然而，这种易感性背后的免疫机制尚不完全清楚，流感的治疗策略也有限。

我们使用同时​​暴露于香烟烟雾和 H1N1 流感感染的小鼠模型、集落刺激因子 (CSF)3 补充/受体 (CSF3R) 阻断和单细胞 RNA 测序 (scRNAseq) 来研究这种关系。

接触香烟烟雾会加剧病毒性肺炎的症状，例如水肿、低氧血症和肺中性粒细胞增多。与仅感染的对照组相比，暴露于烟雾的受感染小鼠的病毒 (v)RNA 有所增加，但具有复制能力的病毒颗粒没有增加。间质而非气腔中性粒细胞增多可以积极预测暴露于烟雾的受感染小鼠的发病率。使用一种新的失调评分对肺部细胞因子进行筛查，发现在烟雾暴露和流感的情况下 CSF3 和白细胞介素 6 的表达加剧。流感期间补充重组 (r)CSF3 会加重发病率、体温过低和水肿，而对暴露于烟雾的感染小鼠进行抗 CSF3R 治疗可改善肺泡毛细血管屏障功能。 scRNAseq 描述了在香烟烟雾和流感的背景下Csf3 ⁺细胞分布向中性粒细胞的转变。然而，尽管暴露在烟雾中的肺部富含受感染的、高度活化的中性粒细胞，但这些细胞的基因特征在很大程度上反映了具有特定独特调节特征的典型流感的恶化形式。

这项工作为香烟烟雾加剧流感感染的机制提供了新的见解，揭示了在此背景下使用的潜在治疗靶点（例如过量的 vRNA 积累、水肿性 CSF3R 信号传导），以及病毒感染性疾病期间临床 rCSF3 治疗的潜在局限性。