SslE Elicits Functional Antibodies That Impair In Vitro Mucinase Activity and In Vivo Colonization by Both Intestinal and Extraintestinal Escherichia coli Strains

Abstract

SslE, the Secreted and surface-associated lipoprotein from Escherichia coli, has recently been associated to the M60-like extracellular zinc-metalloprotease sub-family which is implicated in glycan recognition and processing. SslE can be divided into two main variants and we recently proposed it as a potential vaccine candidate. By applying a number of in vitro bioassays and comparing wild type, knockout mutant and complemented strains, we have now demonstrated that SslE specifically contributes to degradation of mucin substrates, typically present in the intestine and bladder. Mutation of the zinc metallopeptidase motif of SslE dramatically impaired E. coli mucinase activity, confirming the specificity of the phenotype observed. Moreover, antibodies raised against variant I SslE, cloned from strain IHE3034 (SslEIHE3034), are able to inhibit translocation of E. coli strains expressing different variants through a mucin-based matrix, suggesting that SslE induces cross-reactive functional antibodies that affect the metallopeptidase activity. To test this hypothesis, we used well-established animal models and demonstrated that immunization with SslEIHE3034 significantly reduced gut, kidney and spleen colonization by strains producing variant II SslE and belonging to different pathotypes. Taken together, these data strongly support the importance of SslE in E. coli colonization of mucosal surfaces and reinforce the use of this antigen as a component of a broadly protective vaccine against pathogenic E. coli species.

Murine Model of Chemotherapy-Induced Extraintestinal Pathogenic Escherichia coli Translocation

“…SslE encodes a 1,528-amino-acid protein that was initially identified in a reverse vaccinology screen for E. coli proteins that protect against intraperitoneal or intravenous injection of ExPEC (58). Follow-up studies also demonstrated the efficacy of the vaccine in a murine model of ascending urinary tract infection (57). The gene encoding this protein is found in a majority of ExPEC strains and is localized to both the outer membrane (59) and medium, its secretion being dependent on the type II secretion system (T2SS) (58,72).…”

“…SslE is annotated as a M60-like metallopeptidase domain located between amino acids 1090 and 1386, the latter being widely distributed in bacteria associated with mucosal surfaces (73). The M60-like domain of SslE cleaves the intestinal mucins Muc 2 and 3, an activity that facilitates the access of heat-labile enterotoxin (LT) from enterotoxigenic E. coli (ETEC) to intestinal enterocytes (56) and is necessary for the passage of ExPEC through a synthesized mucin matrix (57,74). Given this knowledge, it is possible that the lack of translocation observed for ExPEC devoid of sslE is because this strain cannot degrade the thick mucus barrier to gain access to the underlying intestinal epithelium.…”

“…Both of these genes have been implicated in ExPEC virulence (34,36). We also decided to make a strain of ExPEC that lacks E. coli k1.3385 (ecok1.3385), a gene of uncharacterized function that likely encodes a secreted protein with mucinase activity (56,57) and was previously reported to demonstrate broad protection against ExPEC in a screen for vaccine antigens (58). The gene product was subsequently named SslE (for "secreted and surfaceassociated lipoprotein from E. coli") (59,60).…”

Genome-Wide Investigation of Biofilm Formation in Bacillus cereus

“…Similar peptidases in the M60-like family were shown to play roles in bacterium-host interactions (41). For example, SslE from E. coli, an outer-surfaceassociated M60 family peptidase, was reported to be important for the colonization of E. coli cells onto the mucosal surfaces (42). More interestingly, in B. cereus, next to the peptidase gene is a gene (bc5056) that encodes a collagen-like adhesion protein (Fig.…”

A stable luciferase reporter plasmid for in vivo imaging in murine models of Staphylococcus aureus infections

“…This approach allows monitoring the progression of the infection in mice (Gahan 2012;Kuklin et al 2003;Melican and Richter-Dahlfors 2009;Plaut et al 2013) or the spatial and temporal Electronic supplementary material The online version of this article (doi:10.1007/s00253-015-7229-2) contains supplementary material, which is available to authorized users. functionality of specific bacterial promoters (Lane et al 2007; Morin and Kaper 2009;Nesta et al 2014). In both cases, the bioluminescent signals are followed over time in the same live mice, without the need to kill them at fixed time points.…”