Antimicrobial Activity of Peptide-Coupled Antisense Peptide Nucleic Acids in Streptococcus pneumoniae.

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia and is responsible for multiple other infectious diseases, such as meningitis and otitis media, in children. Resistance to penicillins, macrolides, and fluoroquinolones is increasing and, since the introduction of pneumococcal conjugate vaccines (PCVs), vaccine serotypes have been replaced by non-vaccine serotypes. Antisense peptide nucleic acids (PNAs) have been shown to reduce the growth of several pathogenic bacteria in various infection models. PNAs are frequently coupled to cell-penetrating peptides (CPPs) to improve spontaneous cellular PNA uptake. In this study, different CPPs were investigated for their capability to support translocation of antisense PNAs into S. pneumoniae. HIV-1 TAT- and (RXR)XB-coupled antisense PNAs efficiently reduced the viability of S. pneumoniae strains TIGR4 and D39 . Two essential genes, and , were used as targets for antisense PNAs. Overall, the antimicrobial activity of anti- PNAs was higher than that of anti- PNAs. Target gene transcription levels in S. pneumoniae were reduced following antisense PNA treatment. The effect of HIV-1 TAT- and (RXR)XB-anti- PNAs on pneumococcal survival was also studied using an insect infection model. Treatment increased the survival of infected Galleria mellonella larvae. Our results represent a proof of principle and may provide a basis for the development of efficient antisense molecules for treatment of S. pneumoniae infections. Streptococcus pneumoniae is the most common cause of community-acquired pneumonia and is responsible for the deaths of up to 2 million children each year. Antibiotic resistance and strain replacement by non-vaccine serotypes are growing problems. For this reason, S. pneumoniae has been added to the WHO "global priority list" of antibiotic-resistant bacteria for which novel antimicrobials are most urgently needed. In this study, we investigated whether CPP-coupled antisense PNAs show antibacterial activity in S. pneumoniae. We demonstrated that HIV-1 TAT- and (RXR)4XB-coupled antisense PNAs were able to kill S. pneumoniae . The specificity of the antimicrobial effect was verified by reduced target gene transcription levels in S. pneumoniae. Moreover, CPP-antisense PNA treatment increased the survival rate of infected Galleria mellonella larvae . Based on these results, we believe that efficient antisense PNAs can be developed for the treatment of S. pneumoniae infections.