use-invertebrate-galleria-mellonella-as-an-infection-model-to-study

Use of the Invertebrate <em>Galleria mellonella</em> as an Infection Model to Study the <em>Mycobacterium tuberculosis</em> Complex

Tuberculosis is the leading global cause of infectious disease mortality and roughly a quarter of the world&#8217;s population is believed to be infected ...

Imperial College London

National University of Singapore

The emergence of MDR-TB, coupled with shrinking antibiotic pipelines, has increased demands for new antimicrobials with novel mechanisms of action. Antimicrobial peptides have increasingly been explored as promising alternatives to antibiotics, but their inherent poor in vivo stability remains an impediment to their clinical utility. We therefore systematically evaluated unnatural amino acid-modified peptides to design analogues with enhanced anti-mycobacterial activities.

Unnatural amino acid analogues of membrane-active helical peptides with anti-mycobacterial activity and improved stability.

The escalating threat of antimicrobial resistance has increased pressure to develop novel therapeutic strategies to tackle drug-resistant infections. Antimicrobial peptides have emerged as a promising class of therapeutics for various systemic and topical clinical applications. In this study, the de novo design of α-helical peptides with idealized facial amphiphilicities, based on an understanding of the pertinent features of protein secondary structures, is presented. Synthetic amphiphiles composed of the backbone sequence (XYYX), where X and X are hydrophobic residues (Leu or Ile or Trp), Y and Y are cationic residues (Lys), and n is the number repeat units (2 or 2.5 or 3), demonstrated potent broad-spectrum antimicrobial activities against clinical isolates of drug-susceptible and multi-drug resistant bacteria. Live-cell imaging revealed that the most selective peptide, (LKKL), promoted rapid permeabilization of bacterial membranes. Importantly, (LKKL) not only suppressed biofilm growth, but effectively disrupted mature biofilms after only 2h of treatment. The peptides (LKKL) and (WKKW) suppressed the production of LPS-induced pro-inflammatory mediators to levels of unstimulated controls at low micromolar concentrations. Thus, the rational design strategies proposed herein can be implemented to develop potent, selective and multifunctional α-helical peptides to eradicate drug-resistant biofilm-associated infections.

Disruption of drug-resistant biofilms using de novo designed short α-helical antimicrobial peptides with idealized facial amphiphilicity.

Animal models have long been used in tuberculosis research to understand disease pathogenesis and to evaluate novel vaccine candidates and anti-mycobacterial drugs. However, all have limitations and there is no single animal model which mimics all the aspects of mycobacterial pathogenesis seen in humans. Importantly mice, the most commonly used model, do not normally form granulomas, the hallmark of tuberculosis infection. Thus there is an urgent need for the development of new alternative in vivo models. The insect larvae, Galleria mellonella has been increasingly used as a successful, simple, widely available and cost-effective model to study microbial infections. Here we report for the first time that G. mellonella can be used as an infection model for members of the Mycobacterium tuberculosis complex. We demonstrate a dose-response for G. mellonella survival infected with different inocula of bioluminescent Mycobacterium bovis BCG lux, and demonstrate suppression of mycobacterial luminesence over 14 days. Histopathology staining and transmission electron microscopy of infected G. mellonella phagocytic haemocytes show internalization and aggregation of M. bovis BCG lux in granuloma-like structures, and increasing accumulation of lipid bodies within M. bovis BCG lux over time, characteristic of latent tuberculosis infection. Our results demonstrate that G. mellonella can act as a surrogate host to study the pathogenesis of mycobacterial infection and shed light on host-mycobacteria interactions, including latent tuberculosis infection.

Article	Year
Unnatural amino acid analogues of membrane-active helical peptides with anti-mycobacterial activity and improved stability. The Journal of antimicrobial chemotherapy\| PubMed ID: 27118774	2016
Disruption of drug-resistant biofilms using de novo designed short α-helical antimicrobial peptides with idealized facial amphiphilicity. Acta biomaterialia\| PubMed ID: 28457962	2017
Galleria mellonella - a novel infection model for the Mycobacterium tuberculosis complex. Virulence\| PubMed ID: 30067135	2018

Jasmeet Singh Khara

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