“Naturally occurring antimicrobials to counteract lung infections in cystic fibrosis patients: cecropin A-melittin (CA-M) hybrid peptides and polymixins”

Background: The management of cystic fibrosis (CF) infections by Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) is significantly affected by the emergence of multidrug-resistant (MDR) strains. New therapeutic strategies are needed to circumvent these problems. Naturally occurring antimicrobials, such as antimicrobial peptides (AMPs), are being sought as “lead compound” for developing alternative antimicrobials. The design of enhanced synthetic variants to be used alone or in combination with other antibiotics could, therefore, represent an alternative strategy to counteract multidrug-resistant (MDR) strains. Hypothesis and objectives: The present project will be focused on the definition of novel therapeutic strategies in the treatment of CF lung infections based on the use of naturally occurring AMPs: Cecropin A-Melittin (CA-M) hybrid peptides and their derivates (CA-M hybrids), as well as polymixins. We aim to: i) explore the mechanisms of interaction of CA-M hybrids with bacterial cell envelope, in order to define the molecular requisites for resistance, adaptation and modulation of the host immune response by opportunistic CF pathogens such as P. aeruginosa and Bcc; and ii) evaluate the in vivo and in vitro activity of CA-M hybrids, alone and in combination with antibiotics commonly used in CF therapy (i.e., tobramycin), against planktonic and biofilm cells of CF MDR P. aeruginosa and Bcc strains. Material, methods: production of CA-M derivatives via synthetic methodologies; elucidation of the primary structure of bacterial lipopolysaccharide (LPS) via chemical, spectroscopic and spectrometric techniques; assessment of the pro-inflammatory activities of such isolates; characterization of the micro- and mesostructuring of lipopolysaccharide in lipid bilayers and study of the interaction of LPS-based bilayers with CA-M hybrids; Evaluation, in “CF-like” conditions, of CA-M hybrids activity against planktonic and biofilm phenotype of P. aeruginosa and Bcc; Assessment of toxicity of selected CA-M hybrids and protective effect in murine models of pulmonary acute and chronic infection including CF mice. Expected results and spin-offs: Elucidation of mechanisms of bacterial interaction with AMP (as CA-M hybrids) and definition of molecular requisite for resistance, adaptation and modulation of the host immune response. Characterization of the primary and supramolecular structure of LPS and of its interaction with CA-M hybrids; assessment of AMP in vitro and in vivo antimicrobial activity of CA-M hybrids and derivatives: evaluation of the antibacterial potential of CA-M hybrids, alone and in combination with antibiotics.