Plantaricin NC8

Potent broad-spectrum antiviral agents are urgently needed to combat existing and emerging viral infections. This is particularly important considering that vaccine development is a costly and time consuming process and that viruses constantly mutate and render the vaccine ineffective. Antimicrobial peptides (AMP), such as bacteriocins, are attractive candidates as antiviral agents against enveloped viruses. One of these bacteriocins is PLNC8 αβ, which consists of amphipathic peptides with positive net charges that display high affinity for negatively charged pathogen membrane structures, including phosphatidylserine rich lipid membranes of viral envelopes. Due to the morphological and physiological differences between viral envelopes and host cell plasma membranes, PLNC8 αβ is thought to have high safety profile by specifically targeting viral envelopes without effecting host cell membranes. In this study, we have tested the antiviral effects of PLNC8 αβ against the flaviviruses Langat and Kunjin, coronavirus SARS-CoV-2, influenza A virus (IAV), and human immunodeficiency virus-1 (HIV-1). The concentration of PLNC8 αβ that is required to eliminate all the infective virus particles is in the range of nanomolar (nM) to micromolar (μM), which is surprisingly efficient considering the high content of cholesterol (8-35%) in their lipid envelopes. We found that viruses replicating in the endoplasmic reticulum (ER)/Golgi complex, e.g. SARS-CoV-2 and flaviviruses, are considerably more susceptible to PLNC8 αβ, compared to viruses that acquire their lipid envelope from the plasma membrane, such as IAV and HIV-1. Development of novel broad-spectrum antiviral agents can significantly benefit human health by rapidly and efficiently eliminating infectious virions and thereby limit virus dissemination and spreading between individuals. PLNC8 αβ can potentially be developed into an effective and safe antiviral agent that targets the lipid compartments of viral envelopes of extracellular virions, more or less independent of virus antigenic mutations, which faces many antiviral drugs and vaccines.

Multidrug resistance bacteria constitue an increasing global health problem and the development of novel therapeutic strategies to face this challenge is urgent. Antimicrobial peptides have been proven as potent agents against pathogenic bacteria shown by promising in vitro results. The aim of this study was to characterize the antimicrobial effects of PLNC8 αβ on cell signaling pathways and inflammatory responses of human keratinocytes infected with S. aureus. PLNC8 αβ did not affect the viability of human keratinocytes but upregulated several cytokines (IL-1β, IL-6, CXCL8), MMPs (MMP1, MMP2, MMP9, MMP10) and growth factors (VEGF and PDGF-AA), which are essential in cell regeneration. S. aureus induced the expression of several inflammatory mediators at the gene and protein level and PLNC8 αβ was able to significantly suppress these effects. Intracellular signaling events involved primarily c-Jun via JNK, c-Fos and NFκB, suggesting their essential role in the initiation of inflammatory responses in human keratinocytes. PLNC8 αβ was shown to modulate early keratinocyte responses, without affecting their viability. The peptides have high selectivity towards S. aureus and were efficient at eliminating the bacteria and counteracting their inflammatory and cytotoxic effects, alone and in combination with low concentrations of gentamicin. We propose that PLNC8 αβ may be developed to combat infections caused by Staphylococcus spp.

Plantaricin NC8, a two-peptide non-lantibiotic class IIb bacteriocin composed of PLNC8α and PLNC8β and derived from Lactobacillus plantarum ZJ316, has been shown to be highly potent against a range of bacteria and fungi. In this study, we assessed the antimicrobial mechanism of plantaricin NC8 against the most sensitive bacterial strain, Micrococcus luteus CGMCC 1.193. The results showed that plantaricin NC8 induced membrane permeabilization and caused cell membrane disruption to M. luteus CGMCC 1.193 cells, as evidenced by electrolyte efflux, loss of proton motive force, and ATP depletion within a few minutes of plantaricin NC8 treatment. Furthermore, scanning and transmission electron microscopy showed that plantaricin NC8 had a drastic impact on the structure and integrity of M. luteus CGMCC 1.193 cells. In addition, we found that either PLNC8α or PLNC8β alone exhibited membrane permeabilization activity, but that PLNC8β had higher permeabilization activity, and their individual effects were not as strong as that of the combined compounds as plantaricin NC8. Finally, we showed that lipid II is not the specific target of plantaricin NC8 against M. luteus CGMCC 1.193. Our study reveals the antimicrobial mechanism of plantaricin NC8 against M. luteus CGMCC 1.193.