A Novel C5a-Derived Immunobiotic Peptide Reduces Streptococcus agalactiae Colonization through Targeted Bacterial Killing

Abstract

dStreptococcus agalactiae (group B Streptococcus [GBS]) is a Gram-positive bacterium that colonizes the cervicovaginal tract in approximately 25% of healthy women. Although colonization is asymptomatic, GBS can be vertically transmitted to newborns peripartum, causing severe disease such as pneumonia and meningitis. Current prophylaxis, consisting of late gestation screening and intrapartum antibiotics, has failed to completely prevent transmission, and GBS remains a leading cause of neonatal sepsis and meningitis in the United States. Lack of an effective vaccine and emerging antibiotic resistance necessitate exploring novel therapeutic strategies. We have employed a host-directed immunomodulatory therapy using a novel peptide, known as EP67, derived from the C-terminal region of human complement component C5a. Previously, we have demonstrated in vivo that EP67 engagement of the C5a receptor (CD88) effectively limits staphylococcal infection by promoting cytokine release and neutrophil infiltration. Here, using our established mouse model of GBS vaginal colonization, we observed that EP67 treatment results in rapid clearance of GBS from the murine vagina. However, this was not dependent on functional neutrophil recruitment or CD88 signaling, as EP67 treatment reduced the vaginal bacterial load in mice lacking CD88 or the major neutrophil receptor CXCr2. Interestingly, we found that EP67 inhibits GBS growth in vitro and in vivo and that antibacterial activity was specific to Streptococcus species. Our work establishes that EP67-mediated clearance of GBS is likely due to direct bacterial killing rather than to enhanced immune stimulation. We conclude that EP67 may have potential as a therapeutic to control GBS vaginal colonization.

In vitro and in vivo effects of beneficial vaginal lactobacilli on pathogens responsible for urogenital tract infections

“…Even though several research works have demonstrated the in vitro effects of vaginal lactobacilli on S. agalactiae (Bodaszewska et al , 2010; Juárez Tomás et al ; 2011; Ruiz et al , 2012), the in vivo effect of lactobacilli on this genital pathogen has not been assessed up to now. Cheng et al (2005) and Cavaco et al (2013) used murine models of S. agalactiae vaginal colonization to evaluate the effect of a bacteriophage lytic enzyme and an immunobiotic peptide. Both studies evidenced a reduction in S. agalactiae vaginal colonization.…”

Group B Streptococcal Maternal Colonization and Neonatal Disease: Molecular Mechanisms and Preventative Approaches

“…Bacteriostatic synthetic polymers may represent a barrier for selectively blocking GBS adherence to the vaginal mucosa, while allowing normal constituents of the vaginal flora, such as lactobacilli, to persist ( 268 ). Recently, a synthetic peptide mimicking human C5a was shown to be directly bacteriocidal toward GBS and displayed therapeutic in vivo activity in both peritonitis and vaginal colonization mouse models ( 269 ). Although these compounds show preclinical efficacy in controlling GBS in animal models, it has yet to be established if any of them are feasible or cost-effective for human use.…”

Stable Expression of Modified Green Fluorescent Protein in Group B Streptococci To Enable Visualization in Experimental Systems

“…Studies on GBS that have used fluorescence approaches to label the bacteria have principally applied labeling methods that incorporate DNA stains, such as LIVE/DEAD viability stains (23,(44)(45)(46)(47)(48)(49), nonspecific protein stains, such as fluorescein isothiocyanate (FITC) (17,(50)(51)(52)(53), or antibody-based immunostaining methods (12,54,55). Other previous studies have reported the expression of GFP in GBS, as follows: Périchon et al (11).…”