Induction of Endogenous Antibody Recruitment to the Surface of the Pathogen Enterococcus faecium

Abstract

For the foreseeable future, conventional small molecule antibiotics will continue to be the predominant treatment option due to wide patient coverage and low costs. Today, however, there is already a significant portion of patients that fail to respond to small molecule antibiotics and, according to the Centers for Disease Control and Prevention, this number is poised to increase in the coming years. Therefore, this rise in drug resistant bacteria must be countered with the development of nontraditional therapies. We propose a measure based on the re-engagement of the immune system toward pathogenic bacteria by grafting bacterial cell surfaces with immunogenic agents. Herein, we describe a class of cell wall analogues that selectively graft bacterial cell surfaces with epitopes that promote their opsonization. More specifically, synthetic analogues of peptidoglycan conjugated to haptens were designed to be incorporated by the cell wall biosynthetic machinery into live Enterococcus faecium. E. faecium is a formidable human pathogen that poses a considerable burden to healthcare and often results in fatalities. We showed that treatment of E. faecium and vancomycin-resistant strains with the cell wall analogues led to the display of haptens on the cell surface, which induced the recruitment of antibodies existing in the serum of humans. These results demonstrate the feasibility in using cell wall analogues as the basis of a class of bacterial immunotherapies against dangerous pathogens.

Structure Activity Relationship of the Stem Peptide in Sortase A mediated Ligation from Staphylococcus aureus

“…Our group, and others, previously showed that synthetic acyl-acceptor strands modified with an N-terminal fluorophore are well tolerated by cell wall crosslinking enzymes (PBPs and Ldts). [37][38][39][40][41][42][43] We envisioned that a similar tolerability would enable the structure-activity relationship of srtA. As wildtype S. aureus displays pentaglycine cross-bridge (G5) appended to its 3 rd position lysine sidechain, we first sought to determine the importance of the glycine cross-bridge length.…”

Antibody‐Recruitment as a Therapeutic Strategy: A Brief History and Recent Advances

“…Dalesandro and Pires recently reported synthetic peptidoglycans conjugated to antibody‐recruiting molecules, which were designed to be incorporated by the cell wall of live Enterococcus faecium and vancomycin‐resistant bacterial strains. Treatment with the conjugates led to covalent display of the ABDs, subsequent antibody‐recruitment, and macrophage phagocytosis [19] …”

“…Treatment with the conjugates led to covalent display of the ABDs, subsequent antibody-recruitment, and macrophage phagocytosis. [19] Another limitation of early generation ARMs is modest affinity between endogenous antibodies and the ABD. For example, while relatively simple ABDs like DNP are bound by a significant percentage of serum antibodies, the affinity of these interactions can be low (K D ~10 À 4 -10 À 6 M).…”

Non-invasive Fluorescence Imaging of Gut Commensal Bacteria in Live Mice

“…Instead, we envisioned that administration of a synthetic stem peptide analog conjugated to a NIR fluorophore would circumvent this challenge (Figure 4A). We [41][42][43][44] , and others [45][46][47] , have shown that treatment of bacterial cells with stem peptide analogs also result in their incorporation the PG by PG-related transpeptidases (Figure 4B). The principal advantage of stem peptide analogs is that our laboratory previously showed that the N-terminus of a tetra-or penta-stem peptide analog demonstrates tolerability to large chemical modifications.…”