Inhibition of the PI3K/AKT Signaling Pathway or Overexpression of Beclin1 Blocks Reinfection of Streptococcus pneumoniae After Infection of Influenza A Virus in Severe Community-Acquired Pneumonia.

Streptococcus pneumoniae (S. pneumoniae) and viruses are considered as primary risks of community-acquired pneumonia (CAP), and the effects of co-infection bacterial and virus in the prognosis of patients with severe CAP (SCAP) are poorly described. Therefore, this study is conducted to investigate the regulation of Beclin1-PI3K/AKT axis in reinfection of S. pneumoniae after influenza A virus in mice model of bronchoalveolar lavage fluid (BALF). Samples of sputum and BALF were collected from patients with SCAP for etiological detection. The expression of each gene was determined by RT-qPCR and western blot analysis. Influenza A/PR/8/34 and S. pneumoniae were used to establish the mice model of reinfection pneumonia. The virus quantity, expression levels of inflammatory factors, bacterial load, and myeloperoxidase (MPO) activity were tested. HE staining was applied to observe histopathology of lung tissue. The expression of Beclin1 was downregulated and the PI3K/AKT pathway was activated in viral pneumonia. In vivo experiment, the reinfection of S. pneumoniae following influenza A virus infection increased the number of S. pneumoniae population, the activity of MPO, and the expression of TNF-α, IL-6, and IFN-γ in BALF of mice. In contrast, inhibition of the PI3K/AKT pathway or overexpression of Beclin1 reduced the number of S. pneumoniae population, the activity of MPO, and the expression of TNF-α, IL-6, and IFN-γ in BALF of mice reinfected with S. pneumoniae after influenza A virus infection. Collectively, our study demonstrates that inhibition of the PI3K/AKT signaling pathway or overexpressed Beclin1 alleviates reinfection of S. pneumoniae after influenza A virus infection in SCAP.