Pro-inflammatory Effects of Influenza Type A Virus PB1-F2 Protein-derived Peptide in Lipopolysaccharide-treated Macrophages

Abstract

Influenza A virus (IAV) has the potential to cause pandemics with considerable health and socio-economic burdens. A viral protein, polymerase basic 1- frame2 (PB1-F2), as a virulence factor, has pro-apoptotic activity and contributes to viral pathogenesis by delaying viral clearance and inducing inflammation. Macrophages are susceptible to IAV infection and produce high levels of inflammatory cytokines and chemokines. In the present study, the pro-inflammatory effects of PB1-F2 derived peptide was evaluated by measuring the expression of key inflammatory mediators in murine macrophage cell line J774.1. PB1-F2 treated macrophages were examined for nitric oxide (NO) production, inflammatory cytokines, and enzymes expression and pro-inflammatory cytokines secretion using Griess reagent, real-time polymerase chain reaction (PCR) and ELISA, respectively. Our results have shown that PB1-F2 peptide at non-cytotoxic concentrations (0.1–0.8 µmol/mL) had no effect on NO production. When applied to Lipopolysaccharide (LPS)-treated macrophages, PB1-F2 peptide at 0.8 μmol/mLincreasedinducible NO synthase (iNOS), cyclooxygenase (COX)-2, and interleukin (IL)-6 genes expression to 2.02, 3.81, and 3.65 folds, respectively. PB1-F2 at concentrations of 0.4 and 0.8 µm/mL increased tumor necrosis factor (TNF)-α transcription by 4.15 and 5.55 fold. At posttranslational level, TNF-α increased from 166.5±13.88 in LPS-treated cells to 773.6±95.27 and 1485±76.31 at concentrations of 0.4 and 0.8 μmol/mL in PB1-F2
peptide, respectively. However, PB1-F2 Peptide did not have any significant effect on IL-6 production. These findings suggest that PB1-F2 peptide may partly exert its enhancing role in viral pathogenicity through the induction of inflammatory mediators in macrophages. Hence, targeting PB1-F2 peptide would be helpful in the reduction of viral infection complications.