Peptidoglycan Recognition Protein 3 Does Not Alter the Outcome of Pneumococcal Pneumonia in Mice

Abstract

Pneumococci frequently cause community-acquired pneumonia, a disease with high mortality rates, particularly in young children and in the elderly. Endogenous antimicrobial peptides and proteins such as PGLYRP3 may contribute to the progression and outcome of this disease. Since increasing antibiotic resistant strains occur all over the world, these endogenous antimicrobial molecules are interesting new targets for future therapies. In this study, the expression pattern of PGLYRP3 was analyzed in alveolar epithelial cells, alveolar macrophages and neutrophils. Additionally, the function of PGLYRP3 during Streptococcus pneumoniae-induced pneumonia was investigated in a murine pneumococcal pneumonia model using PGLYRP3KO mice. PGLYRP3 is expressed in all selected cell types but pneumococcus-dependent induction of PGLYRP3 was observed only in neutrophils and alveolar macrophages. Interestingly, there were no significant differences in the bacterial loads within the lungs, the blood or the spleens, in the cytokine response, the composition of immune cells and the histopathology between wild type and PGLYRP3KO mice. Finally, we could neither observe significant differences in the clinical symptoms nor in the overall survival. Collectively, PGLYRP3 seems to be dispensable for the antibacterial defense during pneumococcal pneumonia.

Peptidoglycan Recognition Protein 2 Regulates Neutrophil Recruitment Into the Lungs After Streptococcus pneumoniae Infection

“…Mice were routinely analyzed for the genotype as described previously (Saha et al, 2009; Shrivastav et al, 2018). Briefly, tail tips were digested overnight in Tris-EDTA-SDS buffer and Proteinase K (Sigma-Aldrich, St. Louis, MO, United States).…”

“…For isolating PMNs, the femurs and tibiae of mice were flushed with PBS, and cells were filtered through a 70 μm cell strainer as described earlier (Shrivastav et al, 2018). PMNs were then positively isolated using the mouse anti-Ly6G MicroBead kit (Milteny Biotec GmbH, Telterow, Germany) according to manufacturer’s instruction, seeded in RPMI1640 containing 2% FCS and 1% Glu and infected immediately.…”

“…Lungs from mice infected with S. pneumoniae or PBS-instilled control mice were processed according to Shrivastav et al (2018). Briefly, lungs were perfused via the heart with HBSS, minced in RPMI1640 with 10% FCS and digested with Collagenase A and DNase I (both Roche) at 37°C for 1 h. A single cell suspension was generated, washed with HBSS and blocked with mouse serum.…”

“…However, reports of activity against pneumococci are rare. There is only one report for PGLYRP3 (Shrivastav et al, 2018), showing no effect on S. pneumoniae lung infection in mice. Furthermore, unpublished observations by our group show indirect immunomodulatory effects by PGLYRP4 in the same experimental setting.…”

Impact of the myeloid Krüppel like factor4 during pneumococcal pneumonia

“…The higher mortality of KLF4 -/mice in comparison to KLF4 +/+ mice during S. pneumoniae induced pneumonia are in line with the findings from Shen et al: they had reported earlier that KLF4 KO mice have lower survivability with respect to WT mice after infection with E. coli 166 . Previous reports have described that in order to understand the progression of pneumococcal pneumonia in a murine model, the mice have to be monitored 10 days after infection 177,229 . It has already been reported that various clinical symptoms associated with infection in mice include fall in body temperature, less responsiveness, dyspnea 230 .…”