Immunofluorescence staining for the complement component deposition on the middle ear epithelium on day 1 post Spn infection showed increased C3, C5aR (Fig. 6A), and C5b-9 (Fig. 6B) deposition on the inflammatory middle ear epithelium in the cohorts infected with both IAV and Spn compared to those infected with either pathogen alone. This evidence concerns the gene C5AR1 and infection.