Co-infections with respiratory virus and Streptococcus pneumoniae have been frequently reported in epidemiologic studies. Here, we explore how inoculating A549 and Hep-2 cell monolayers with human metapneumovirus (hMPV) affected subsequent in vitro infections with pneumococcus serotypes 3 and 14. The different serotypes had variable adherence, but the A549 cells with a preceding hMPV infection had significantly enhanced bacterial adherence. Also, BALB/c mice infected with hMPV had increased adhesion of pneumococcus to the bronchial epithelium. The lungs of mice with a preceding hMPV inoculation had delayed bacterial clearance and exacerbated histopathology after they were infected with Streptococcus pneumoniae. Additionally, the mice with a preceding hMPV infection had inhibited recruitment of airway neutrophil and decreased expression of neutrophil chemoattractants. Our results suggest that
airways infected with hMPV, especially lower airway epithelium, allow increased adherence of Streptococcus pneumoniae and
hMPV-infected mice have impaired recruitment of airway neutrophils that may cause delayed bacterial clearance and exacerbated pulmonary inflammation.