Ricerc@Sapienza

This research group is mainly concerned with the structural-functional characterization of antimicrobial peptides (AMPs) derived from amphibian skin or de-novo designed analogues, for the development of novel therapeutic agents against multidrug resistant infections that pose a serious threat to global human health. In contrast with traditional antibiotics, AMPs have: (i) a rapid killing mechanism based on perturbation of the microbial cell membrane, causing irreparable damage that hardly induces resistance; (ii) an anti-biofilm activity and (iii) additional biological properties including the neutralization of the toxic effect  of the bacterial lipopolysaccharide as well as the promotion of wound healing activity

In the past years, a frog-skin derived peptide i.e. Esc(1-21) was found to display a significant in vivo efficacy in a mouse model of keratitis induced by the bacterium Pseudomonas aeruginosa. So far only a few in vivo experiments have provided signs of clinical benefit of AMPs against keratitis. At the same time, it was discovered how the stereochemical change of only two amino acids is sufficient to improve the peptide’s selectivity index, biostability, wound healing activity and in vivo therapeutic efficacy.  In parallel, it was found that this selective epimerization can affect the peptide’s ability to interact with the bacterial lipopolysaccharide (LPS) or model membranes (liposomes) as well as with nucleotides (i.e.guanosine pentaphosphate,ppGpp) preventing biofilm formation. 

Furthermore, it has been recently observed that these peptides are able to restore the functionality of the mutated CFTR channel in CF patients upon direct interaction with the mutated channel.

However, a key step for AMPs development is a proper delivery system to target AMPs at the site of infection at effective concentration, with minimal off-target effects. In this context, by means of nanotechnology approaches, it was demonstrated how encapsulation of these peptides inside engineered biodegradable polymeric nanoparticles is an excellent strategy (i) to overcome lung barriers (i.e. the sticky mucus lying the airways epithelia, mostly in cystic fibrosis sufferers) that usually interfere with the antibiotic treatment and (ii) to prolong the antimicrobial efficacy of the encapsulated peptide.

Consistent with the above goals, the main objectives of this research group include:

• The design and characterization of peptide analogs for structure-activity relationship studies and to optimize treatment of lung pathology in CF
• The development of antimicrobial medical devices, such as peptide-immobilized contact lenses, to prevent microbial colonization of the lenses and the incidence of ocular surface infections.
•  Functional characterization of biodegradable formulations to deliver peptides to the site of action.
•  Study of the mechanism of antimicrobial action by proteomic approach and model membranes

By using experimental conditions that allow both the determination of microbicidal activity and the measurement of peptide/membrane association directly in bacteria, the amount of cell-bound peptide molecules needed for killing a bacterium was identified. Studies aimed at assessing the exact site of association of peptides to bacterial cells are in progress.