S-layer proteins from lactobacilli as vaccine delivery systems. Review

Abstract

The S-layer, crystalline arrays of proteinaceous subunits, seems to be a typical surface structure in several lactobacilli species. Due their self-assembly ability to recrystallize into isoporous monolayers in suspension, at liquid-surface interfaces, lipid structures and on solid supports, S-layers were demonstrated to possess a great potential for nanobiotechnological applications. Interest in lactobacilli S-layer has been reinforced by claimed and demonstrated probiotic properties for human and animal consumers. Several lactobacillar S-layer have been found to be involved in adherence to intestinal epithelial cells and to the mammalian extracellular matrix. Due to these observed adhesive properties, the possible therapeutic applications of lactobacillar S-layers have become increasingly of interest, e.g. as targeted antigen delivery vehicles to host tissues. In addition, S-layers may provide superior expression levels and surface density of antigens when compared to other bacterial antigen presentation systems. It has already been demonstrated that S-layer protein subunits can be modified to carry foreign epitopes as a uniform recombinant S-layer on the Lactobacillus cell surface. The adhesion and immunogenic functions of S-layer proteins, combined with the properties of Lactobacillus spp., could lead to new, safe, and stable liposomal particles for drug delivery.