Related Experiment Video
Updated: Jun 17, 2026
Modeling Dysplastic and Functional Lung Alveolar Repair after Influenza Infection
Published on: September 19, 2025
Dysregulated macrophage-inflammatory protein-2 expression drives illness in bacterial superinfection of influenza
Caleb C J Zavitz1, Carla M T Bauer, Gordon J Gaschler
1Medical Sciences Program, McMaster University, Hamilton, Ontario, Canada.
Abstract:
Influenza virus infection is a leading cause of death and disability throughout the world. Influenza-infected hosts are vulnerable to secondary bacterial infection, however, and an ensuing bacterial pneumonia is actually the predominant cause of influenza-attributed deaths during pandemics. A number of mechanisms have been proposed by which influenza may predispose to superinfection with an unrelated or heterologous pathogen, but the subsequent interaction between the host, virus, and bacteria remains an understudied area. In this study, we develop and examine a novel model of heterologous pulmonary infection in which an otherwise subclinical Bordetella parapertussis infection synergizes with an influenza virus infection to yield a life-threatening secondary pneumonia. Despite a profound pulmonary inflammatory response and unaltered viral clearance, bacterial clearance was significantly impaired in heterologously infected mice. No deficits were observed in pulmonary or systemic adaptive immune responses or the viability or function of infiltrating inflammatory cells to explain this phenomenon, and we provide evidence that the onset of severe pulmonary inflammation actually precedes the increased bacterial burden, suggesting that exacerbated inflammation is independent of bacterial burden. To that end, neutralization of the ELR(+) inflammatory chemokine MIP-2 (CXCL2/GRO-beta) attenuated the inflammation, weight loss, and clinical presentation of heterologously infected mice without impacting bacterial burden. These data suggest that pulmonary inflammation, rather than pathogen burden, is the key threat during bacterial superinfection of influenza and that selective chemokine antagonists may be a novel therapeutic intervention in cases of bacterial superinfection of influenza.
Insights
Influenza virus infection increases vulnerability to secondary bacterial pneumonia. Targeting inflammatory chemokines, not bacterial load, may treat severe superinfections.
Area of Science:
- * Immunology
- * Infectious Diseases
- * Pulmonary Medicine
Background:
- * Influenza virus infection is a major global health threat, often leading to fatal secondary bacterial pneumonia.
- * Mechanisms underlying influenza-induced susceptibility to heterologous bacterial superinfection are not fully understood.
- * Bacterial pneumonia is the primary cause of influenza-associated mortality, especially during pandemics.
Purpose of the Study:
- * To investigate the synergistic interaction between influenza virus and Bordetella parapertussis in a novel pulmonary infection model.
- * To elucidate the host-pathogen dynamics and identify key factors driving severe secondary pneumonia.
- * To evaluate the therapeutic potential of targeting inflammatory mediators in influenza-bacterial superinfection.
Main Methods:
- * Development of a mouse model combining influenza virus infection with subclinical Bordetella parapertussis.
- * Assessment of viral and bacterial clearance, pulmonary inflammation, and host immune responses.
- * In vivo neutralization of the chemokine MIP-2 (CXCL2/GRO-beta) to evaluate its impact on disease severity.
Main Results:
- * Heterologous infection led to severe pneumonia with impaired bacterial clearance despite efficient viral clearance.
- * Exacerbated pulmonary inflammation preceded increased bacterial burden, indicating inflammation is not solely driven by bacterial load.
- * MIP-2 neutralization reduced inflammation and clinical symptoms without affecting bacterial burden.
Conclusions:
- * Pulmonary inflammation, rather than bacterial pathogen burden, is the critical determinant of severity in influenza-bacterial superinfection.
- * Targeting specific inflammatory chemokines like MIP-2 shows promise as a therapeutic strategy.
- * Selective chemokine antagonists represent a potential novel treatment for secondary bacterial pneumonia following influenza.
Related Concept Videos
02:28Leaky Scanning
01:27Influenza
01:25Inflammatory Bowel Disease III: Crohn's Disease