Synergistic Effects Of Lysins Targeting Streptococcus Pneumoniae

Streptococcus pneumoniae is one of the most common bacterial pathogens with high morbidity and mortality rates worldwide.This important pathogen can cause both invasive and non-invasive diseases such as severe sepsis among others,causing deaths in children under 5 years of age worldwide.Due to insufficient vaccine coverage,serotype replacement problems in the later stages of vaccine usage,and the increasing resistance of S.pneumoniae to traditional antibiotics,the current clinical treatment and prevention of S.pneumoniae face enormous challenges that prompt for studies into new drug and vaccine.Choline binding proteins(CBP)are a family of peptides found in S.pneumoniae and related species that have modular structures(functional modules(FM)and choline binding modules(CBM))which use non-convalent interactions to anchor a protein to the choline residues located in the cell wall.Pneumococcal CBP include cell wall hydrolases,adhesins,and other virulence factors,which play important physiological roles in bacterial viability and virulence.Endolysins(or lysins)are evolved bacteriophage encoded enzymes that specifically hydrolyze peptidoglycan bonds,and allowing the releasing of the phage progeny particles by disrupting the integrity of the bacterial cell wall.Most the endolysins identified from pneumococcal phages are characterized by a two-module structure,a N-terminal catalytic domain,and a C-terminal cell wall binding domain.Pneumococcal endolysins lack signal sequences,so the translocation through the cytoplasmic membrane to access their substrate in the peptidoglycan is mediated by holin-lysin system.In this study,we investigated the synergistic effects among three S.pneumoniae targeted lysins,ClyJ,Cpl-1 and ClyR,in which the cell-wall binding modules of ClyJ and Cpl-1 consist of a typical CBM.According to in vivo and in vitro assays,the synergy between the catalytic domains lays a foundation for the combined applications of lysin enzymesThe experimental results showed that there is a significant synergistic effect between S.pneumoniae lysins ClyJ and Cpl-1,showing obviously improved bactericidal activity in vitro and in mouse protection experiments.At the same time,preliminary results from mice immunized with lysin enzymes containing the CBMstructure showed that lysin enzymes could have good immunoprotective effects.The results of this study further confirmed the safety of combined lysin dosage strategy and their bactericidal efficiency both in vitro and in vivo.More importantly,this strategy can not only reduce the bacterial resistance,but can also be used in the development of novel antibacterials antigens and vaccine.