Related Experiment Video
Updated: Apr 26, 2026
An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection
Published on: December 10, 2013
Regulation of IFN-γ by IL-13 dictates susceptibility to secondary postinfluenza MRSA pneumonia
Agnieszka Rynda-Apple1, Ann Harmsen, Anfin S Erickson
1Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA.
Abstract:
Superinfection in mice at day 7 postinfluenza infection exacerbates bacterial pneumonia at least in part via downstream effects of increased IFN-γ signaling. Here we show that up to 3 days postinfluenza infection, mice have reduced susceptibility to superinfection with methicillin-resistant Staphylococcus aureus (MRSA), but that superinfection during that time exacerbated influenza disease. This was due to IL-13 signaling that was advantageous for resolving MRSA infection via inhibition of IFN-γ, but was detrimental to the clearance of influenza virus. However, if superinfection did not occur until the near resolution of influenza infection (day 7), IL-13 signaling was inhibited, at least in part by upregulation of IL-13 decoy receptor (IL-13Rα2), which in turn caused increases in IFN-γ signaling and exacerbation of bacterial infection. Understanding these cytokine sequelae is critical to development of immunotherapies for influenza-MRSA coinfection since perturbations of these sequelae at the wrong time could increase susceptibility to MRSA and/or influenza.
Insights
Superinfection with MRSA during early influenza infection exacerbates viral disease by altering IL-13 signaling. Later superinfection, however, worsens bacterial pneumonia due to suppressed IL-13 and increased IFN-γ signaling.
Area of Science:
- Immunology
- Respiratory Infections
- Microbiology
Background:
- Influenza virus infection can predispose individuals to secondary bacterial infections.
- The timing of secondary bacterial superinfection influences disease severity and outcomes.
- Cytokine signaling pathways play a critical role in host defense against viral and bacterial pathogens.
Purpose of the Study:
- To investigate the impact of methicillin-resistant Staphylococcus aureus (MRSA) superinfection timing on influenza disease severity in a mouse model.
- To elucidate the underlying cytokine mechanisms, specifically involving Interleukin-13 (IL-13) and Interferon-gamma (IFN-γ), that mediate the effects of superinfection.
- To understand how manipulating these cytokine pathways could inform immunotherapies for coinfections.
Main Methods:
- A mouse model was used to study superinfection with MRSA at different time points (day 3 and day 7) following influenza virus infection.
- Quantitative analysis of viral load and bacterial burden was performed.
- Cytokine levels and signaling pathways, including IL-13 and IFN-γ, were assessed, along with the expression of IL-13 receptor alpha 2 (IL-13Rα2).
Main Results:
- Superinfection with MRSA up to day 3 post-influenza exacerbated influenza disease, mediated by IL-13 signaling that inhibited IFN-γ but impaired viral clearance.
- Superinfection at day 7 post-influenza, near influenza resolution, exacerbated bacterial pneumonia.
- This late-stage exacerbation was linked to inhibited IL-13 signaling, partly due to increased IL-13Rα2, leading to enhanced IFN-γ signaling.
Conclusions:
- The timing of MRSA superinfection critically dictates the host immune response and disease outcome during influenza.
- Dysregulation of IL-13 and IFN-γ signaling pathways underlies the differential effects of early versus late superinfection.
- Targeting these cytokine sequelae requires careful consideration of the infection stage to develop effective immunotherapies for influenza-MRSA coinfection.
More Related Videos
Related Concept Videos
01:29Pneumonia II: Pathophysiology
01:24T Cell Types and Functions
Th1 cells stimulate dendritic cells to express necessary co-stimulatory molecules on their surfaces for...