Targeting cell-cell communication systems of Streptococcus pneumoniae by molecularly imprinted polymers

Abstract

Streptococcus pneumoniae communicates through quorum sensing systems (QSS), which coordinate bacterial behaviour via pheromone signalling. Among peptide-mediated QSS, the regulatory gene family glycosyltransferase (Rgg) plays a crucial role in biofilm formation, virulence, bacteriocin production, and oxidative stress resistance, though its role in virulence and the possibility of being a drug target remain underexplored. This study investigated Rgg144 and Rgg1518, examining their regulatory interactions using isogenic mutants in growth studies, biochemical assays, and reporter gene analyses. The findings indicate that both Rggs contribute to mannose and galactose metabolism, as mutants exhibit attenuated growth and both systems were specifically induced by these sugars. Furthermore, full induction of each pathway required the presence of the other, indicating the inter-regulatory interactions between the two systems. Additionally, both Rggs play a significant role in protection against oxidative stress as evidence by the reduced expression of genes coding for superoxide dismutase (sodA) and thiol peroxidase (tpxD) in mutant strains and increased sensitivity to hydrogen peroxide and paraquat. Rgg144 and Rgg1518 were also implicated in pneumococcal colonisation and virulence, as mutant strains showed attenuated phenotypes in vivo. To disrupt pneumococcal communication, peptide-specific nano-molecularly imprinted polymers (nano-MIPs), shp144MIP and shp1518MIP, were synthesised. These nano-MIPs exhibited no toxicity in vivo (Galleria mellonella) or in vitro (S. pneumoniae growth) and effectively reduced disease progression, nasopharyngeal colonisation in a murine model, gene expression in reporter strains, and galactose utilisation. This study highlights the critical roles of Rgg144 and Rgg1518 in pneumococcal metabolism, oxidative stress response and colonisation, and introduces nano-MIPs as a promising therapeutic strategy to interfere with quorum sensing in Gram-positive bacterial infections, particularly S. pneumoniae.