Synergistic stimulation of type I interferons during influenza virus coinfection promotes Streptococcus pneumoniae colonization in mice

Shigeki Nakamura, Kimberly M. Davis, and Jeffrey N. Weiser

 J Clin Invest. (2011) 121:3657-3665

Speaker: Miao-Huei Cheng (鄭妙慧)                            Time: 15:10~16:00, May 16, 2012

Commentator: Dr. Lien-I Hor (何漣漪老師)               Place: Room 601

Abstract

Streptococcus pneumoniaes known as pneumococcus is an important pathogen causing invasive diseases and respiratory tract infections. Recent studies showed that coinfection with influenza and bacterial pathogens occurred more frequently in pandemic rather than in seasonal influenza periods. In addition, many studies showed that bacterial coinfections with influenza virus can cause life-threatening diseases such as sepsis, meningitis, and pneumonia. The most common bacterial coinfections with influenza virus are due to S. pneumoniae, H. influenzae, Staphylococcus spp., andStreptococcus spp. Of these, S. pneumoniae is the most common cause of bacterial coinfection with influenza and account for 40.8% and 16.6% of bacterial coinfections during pandemic and seasonal periods, respectively [1]. The results in the study show that coinfection with influenza virus andpneumococcus leads to synergistic stimulation of type I IFNs and that this impairs the recruitment of macrophages, by decreasing chemokine CCL2 production in the mouse model. The stimulation of CCL2 by macrophages upon pneumococcal infection alone requires the pattern recognition receptor Nod2 and expression of the pore-forming toxin pneumolysin. Furthermore, the type I IFNs are sufficient to inhibit Nod2 signaling and decrease the expression of pneumolysin, which is a Nod2-depended response to S. pneumonia. This event leads to increased bacterial colonization in the respiratory tract and causes higher rates of disease associated with coinfection in humans. Therefore, altered colonization dynamics during influenza virus infection may contribute to bacterial clearance.

Reference

1.          Xuan-YiWang et al. Influenza and Bacterial Pathogen Coinfections in the 20th Century. Interdisciplinary Perspectives on Infectious Diseases 2011:1-6 (2011)