Exposure to Electronic Cigarettes Impairs Pulmonary Anti-Bacterial and Anti-Viral Defenses in a Mouse Model

Study of mouse models for resistance to flu and pneumonia after 2 weeks being submitted to vapour 3 hours per day.

It shows that free radicals are present in the vapour, leading to reduced immunity to flu and pneumonia. But those radicals are only at a level equivalent to 1% of the one found in combustible cigarette smoke.

Published: 04 February 2015

Positive: N/A

Link to publication: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0116861#sec011

DOI: 10.1371/journal.pone.0116861

Comments from Jacques Le Houezec (in French): JLH Comments

Bernd Mayer’s point of view, with a set of studies debunking the results: http://www.bernd-mayer.com/electronic-cigarettes-airway-infections-update/

ECITA’s comments: http://www.ecita.org.uk/ecita-blog/new-study-mice-shows-remarkably-little-acute-toxicity-despite-major-methodology-problems


Thomas E. Sussan
Sachin Gajghate
Rajesh K. Thimmulappa
Jinfang Ma
Jung-Hyun Kim
Kuladeep Sudini
Nicola Consolini
Stephania A. Cormier
Slawo Lomnicki
Farhana Hasan
Andrew Pekosz
Shyam Biswal


Electronic cigarettes (E-cigs) have experienced sharp increases in popularity over the past five years due to many factors, including aggressive marketing, increased restrictions on conventional cigarettes, and a perception that E-cigs are healthy alternatives to cigarettes. Despite this perception, studies on health effects in humans are extremely limited and in vivo animal models have not been generated. Presently, we determined that E-cig vapor contains 7×1011 free radicals per puff. To determine whether E-cig exposure impacts pulmonary responses in mice, we developed an inhalation chamber for E-cig exposure. Mice that were exposed to E-cig vapor contained serum cotinine concentrations that are comparable to human E-cig users. E-cig exposure for 2 weeks produced a significant increase in oxidative stress and moderate macrophage-mediated inflammation. Since, COPD patients are susceptible to bacterial and viral infections, we tested effects of E-cigs on immune response. Mice that were exposed to E-cig vapor showed significantly impaired pulmonary bacterial clearance, compared to air-exposed mice, following an intranasal infection with Streptococcus pneumonia. This defective bacterial clearance was partially due to reduced phagocytosis by alveolar macrophages from E-cig exposed mice. In response to Influenza A virus infection, E-cig exposed mice displayed increased lung viral titers and enhanced virus-induced illness and mortality. In summary, this study reports a murine model of E-cig exposure and demonstrates that E-cig exposure elicits impaired pulmonary anti-microbial defenses. Hence, E-cig exposure as an alternative to cigarette smoking must be rigorously tested in users for their effects on immune response and susceptibility to bacterial and viral infections.


In conclusion, E-cig exposure results in immunomodulatory effects that are similar to those observed after exposure to cigarette smoke. Since bacterial and viral exacerbations are major drivers of COPD disease progression, this study raises a concern that COPD patients who switch from cigarettes to E-cigs may not observe substantial improvement in their disease progression. Furthermore, popularity of E-cigs among teenagers is rapidly rising, which may lead to an emerging threat to public health with regards to recurrent bacterial or viral infections. Despite the common perception that E-cigs are safe, this study clearly demonstrates that E-cig use, even for relatively brief periods, may have significant consequences to respiratory health in an animal model; and hence, E-cigs need to be tested more rigorously, especially in susceptible populations.

Complete study here: Exposure of Mice to Vapor and Resistance to Flu and Pneumonia 2015