Lung infections associated with Staphylococcus aureus and Pseudomonas aeruginosa bacteria represent a major life threat, especially in elderly. This is mainly due to the ability of these pathogens to form biofilms which are very difficult to eradicate by the currently-used antibiotics. In addition, the presence of a compromised immune system related to age, including deficiency of vitamin D, contributes to the establishment of such infections.
Antimicrobial peptides (AMPs) hold promise for the generation of new therapeutics. We identified a short-sized AMP from amphibian skin, Esc(1-21), which rapidly kills these microbes with a membrane-perturbing mechanism. This prevents bacteria from developing resistance. However, some major tasks need to be reached to make AMPs as good candidates for therapy: minimal enzymatic degradation/cytotoxicity and a suitable formulation for peptide delivery. In line with the above, we synthesized a diastereomer of Esc(1-21) by replacing two L-amino acids with the corresponding D-enantiomers. It resulted to be more stable; less toxic to mammalian cells and more efficient in reducing lung bacterial burden. Importantly, before bringing AMPs to clinical use, it is crucial the development of pharmaceutical formulations to assist peptide diffusion through extracellular barriers and to provide a sustained peptide release prolonging its therapeutic efficacy.
In addition, combination therapy of AMPs with traditional antibiotics is a valuable strategy to maximize the efficacy of single drugs and to reduce the resistance selection pressure.
In this Project, we will properly evaluate:
- the biochemical/biological properties of selected AMPs (i.e. temporins and Esc-peptides) in lung mimicking environment;
- the synergistic effect with conventional antibiotics, suitably selected by a novel software tool;
- the efficacy in lung bacterial clearance;
- the in vitro and in vivo efficacy of polymeric nanoparticles for lung delivery of AMPs.
This project aims at developing novel therapeutic approaches, based on the usage of amphibian-skin derived AMPs, either alone or in combination with conventional drugs, for local treatment of bacterial pulmonary infections, which represent a serious life threat, especially in the elderly. In addition, the purpose of the Project is to find out the best nanoformulation to assist the peptide delivery at lung upon intratracheal instillation and to provide a sustained release of the peptide at the site of infection with minimal side-effects. Furthermore, the achievement of our goals will contribute to clarify the potency of the selected drug combination in defeating bacterial lung infections also during vitamin D deficiency.
It is widely known that both S. aureus and P. aeruginosa are opportunistic pathogens difficult to eradicate mainly due to their ability to form sessile communities and to be resistant to the available antibiotics. Therefore, the discovery of new antimicrobials is highly demanded and naturally-occurring AMPs or derivatives hold promise for the generation of a novel class of anti-infective agents.
Importantly, our studies will highly contribute to remove the hurdles (e.g. susceptibility to proteolytic degradation, low safety, low bioavailability) that have prevented sofar the adoption of AMPs in clinical settings. Moreover, the use of AMPs in concert with conventional antibiotics will help in slowing down the incidence of resistance in the latter and present an alternative first-line strategy while new antimicrobials are being settled in.
Efforts to develop (i) amphibian skin AMPs as novel anti-infective drugs with the ability to favour repair of the injured bronchial epithelium; (ii) procedures to evaluate either their structure or their efficacy/toxicity in pathophysiological context and (iii) nanoformulations to increase their bioavailability at lung level will have high potential to bring these molecules closer to clinical use.
Remarkably, the achievement of the Project will likely allow to yield a peptide-based formulation to treat P. aeruginosa/S. aureus lung infection and to promote healing of the damaged lung tissue. Furthermore, the obtained peptide-loaded NPs could be further developed into dry powders for inhalation allowing a much easier and faster administration route in comparison to nebulized liquid formulation or intravenous injection.
This will be of great impact for patients and for small/medium-sized biotech companies that would benefit from the exploitation of this project and likely transfer our technologies to larger pharmaceutical companies for the final clinical translation. The direct economic benefits arising from these industrial applications, however represent only a fraction of the socio-economic impact of adding even a single new component to the declining arsenal of weapons against the sprouting antibiotic-resistance health threat.
Overall, our Project activities fall within the European Framework Programme for Research and Innovation priorities. Furthermore, the multidisciplinary approach that characterizes this Proposal will allow to integrate resources and knowledge from different fields in order to create a consolidated base for the future advancement of bio-nanomedicine.
Besides being published in peer-reviewed scientific journals and presented at national and international meetings, results achieved from these studies will be disseminated through public meetings also to a wider non-specialist public, to inform people about the risks of antibiotic resistance and the measures that can be taken in order to control and to reduce this phenomenon.