Type I IFNs mediate development of postinfluenza bacterial pneumonia in mice
Arash Shahangian, Edward K. Chow, Xiaoli Tian, Jason R. Kang, Amir Ghaffari, Su Y. Liu, John A. Belperio, Genhong Cheng, Jane C. Deng
Arash Shahangian, Edward K. Chow, Xiaoli Tian, Jason R. Kang, Amir Ghaffari, Su Y. Liu, John A. Belperio, Genhong Cheng, Jane C. Deng
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Research Article Infectious disease

Type I IFNs mediate development of postinfluenza bacterial pneumonia in mice

Abstract

Influenza-related complications continue to be a major cause of mortality worldwide. Due to unclear mechanisms, a substantial number of influenza-related deaths result from bacterial superinfections, particularly secondary pneumococcal pneumonia. Here, we report what we believe to be a novel mechanism by which influenza-induced type I IFNs sensitize hosts to secondary bacterial infections. Influenza-infected mice deficient for type I IFN-α/β receptor signaling (Ifnar–/– mice) had improved survival and clearance of secondary Streptococcus pneumoniae infection from the lungs and blood, as compared with similarly infected wild-type animals. The less effective response in wild-type mice seemed to be attributable to impaired production of neutrophil chemoattractants KC (also known as Cxcl1) and Mip2 (also known as Cxcl2) following secondary challenge with S. pneumoniae. This resulted in inadequate neutrophil responses during the early phase of host defense against secondary bacterial infection. Indeed, influenza-infected wild-type mice cleared secondary pneumococcal pneumonia after pulmonary administration of exogenous KC and Mip2, whereas neutralization of Cxcr2, the common receptor for KC and Mip2, reversed the protective phenotype observed in Ifnar–/– mice. These data may underscore the importance of the type I IFN inhibitory pathway on CXC chemokine production. Collectively, these findings highlight what we believe to be a novel mechanism by which the antiviral response to influenza sensitizes hosts to secondary bacterial pneumonia.

Authors

Arash Shahangian, Edward K. Chow, Xiaoli Tian, Jason R. Kang, Amir Ghaffari, Su Y. Liu, John A. Belperio, Genhong Cheng, Jane C. Deng

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Figure 3

Lung homogenates from PR8/S. pneumoniae–infected Ifnar–/– mice contain higher levels of KC and Mip2.

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Lung homogenates from PR8/S. pneumoniae–infected Ifnar–/– mice contain h...
Production of KC and Mip2 in response to secondary pneumococcal infection, as determined by ELISA analysis of Ifnar+/+ and Ifnar–/– mice with prior influenza infection. Levels of other inflammatory cytokines were determined by multiplex cytokine protein analysis. Lung homogenates were obtained and analyzed 16 hours after secondary challenge with S. pneumoniae. n ≥ 4 mice per group.