PLNC8 αβ Potently Inhibits the Flavivirus Kunjin and Modulates Inflammatory and Intracellular Signaling Responses of Alveolar Epithelial Cells

PLNC8 αβ is a cationic antimicrobial peptide that previously has been reported to express both antibacterial and antiviral properties. This study aimed to further elucidate the antiviral effects of PLNC8 αβ and its impact on virus-induced cytotoxicity and inflammatory signaling in human alveolar epithelial cells (A549) infected with the flavivirus Kunjin. Complementary in silico analyses using molecular dynamics (MD) simulation were conducted to investigate the mechanism of action of PLNC8 αβ by studying the interaction of PLNC8 α and β with models of a flavivirus membrane and a eukaryotic plasma membrane, respectively. Our findings demonstrated that PLNC8 αβ significantly reduces both extracellular and intracellular viral loads, as confirmed by plaque reduction assays and RT-PCR. The peptide also mitigated virus-induced cytotoxicity and inflammation. Notably, PLNC8 αβ modulated the virus-induced dysregulation of key signaling and inflammatory genes, such as <i>TLR9</i>, <i>TLR3</i>, <i>NOD2</i>, <i>FOS</i>, <i>JUN</i>, <i>IL6</i>, and <i>CXCL8</i>. MD simulation revealed that PLNC8 αβ exhibits higher binding affinity for a flavivirus membrane model compared to a model of the plasma membrane, likely due to stronger electrostatic interactions with anionic phospholipids. This selective interaction possibly accounts for a potent antiviral activity of PLNC8 αβ combined with a minimal cytotoxicity toward human cells. Overall, PLNC8 αβ shows significant promise as an antiviral agent against flavivirus infections and warrants further exploration for peptide-based antiviral therapies.