Probiotics, Their Extracellular Vesicles and Infectious Diseases

Abstract

Probiotics have been shown to be effective against infectious diseases in clinical trials, with either intestinal or extraintestinal health benefits. Even though probiotic effects are strain-specific, some “widespread effects” include: pathogen inhibition, enhancement of barrier integrity and regulation of immune responses. The mechanisms involved in the health benefits of probiotics are not completely understood, but these effects can be mediated, at least in part, by probiotic-derived extracellular vesicles (EVs). However, to date, there are no clinical trials examining probiotic-derived EVs health benefits against infectious diseases. There is still a long way to go to bridge the gap between basic research and clinical practice. This review attempts to summarize the current knowledge about EVs released by probiotic bacteria to understand their possible role in the prevention and/or treatment of infectious diseases. A better understanding of the mechanisms whereby EVs package their cargo and the process involved in communication with host cells (inter-kingdom communication), would allow further advances in this field. In addition, we comment on the potential use and missing knowledge of EVs as therapeutic agents (postbiotics) against infectious diseases. Future research on probiotic-derived EVs is needed to open new avenues for the encapsulation of bioactives inside EVs from GRAS (Generally Regarded as Safe) bacteria. This could be a scientific novelty with applications in functional foods and pharmaceutical industries.

Lactobacilli extracellular vesicles: potential postbiotics to support the vaginal microbiota homeostasis

“…Recently, it was discovered that vaginal Lactobacillus strains release nanosized membrane particles, named extracellular vesicles (EVs), implicated in cell-to-cell and microbiota-host communications [ 8 ]. According to literature, EVs play a crucial role in a variety of physiological and pathological processes due to their capacity to carry bioactive macromolecules (i.e., proteins, DNA, and RNA) that can alter the biological properties of bacteria and/or host cells [ 22 ].…”

“…Compared to other human niches, only a few studies have been carried out on EVs released in the vaginal environment by beneficial lactobacilli, and our understanding of their biogenesis, composition, and functionality are still poor [ 22 , 23 ].…”

“…MRS-EVs average size were similar to those reported by Palomino et al [ 8 ] (150–160 nm) and characterized by a negative Z-potential value. Since it is generally recognized that bacterial EVs effect can be associated to their cargo [ 22 ], we decided to characterize Lactobacillus -EVs composition in terms of total protein and nucleic acids content. As previously reported by Palomino et al [ 8 ], we confirmed that L. crispatus BC5-EVs and L. gasseri BC12-EVs contain proteins and, for the first time, also DNA and RNA were recovered.…”

“…From our findings, it appears that the biological macromolecules of medium ingredients are also carried by nanometric vesicles. As far as we know, there is no characterization of nucleic acids delivered by Lactobacillus -EVs and further studies are required to deeply analyze EVs composition [ 22 ].…”

“…It has been reported that Lactobacillus -EVs metabolites, nucleic acids, and protein content can be associated to a peculiar biological role of EVs [ 18 , 22 ]. Regarding L. crispatus BC5-EVs and L. gasseri BC12-EVs protein content, Palomino et al identified some adhesins (i.e., enolases, elongation factor-TU, 30S ribosomal protein, pyruvate kinase, chaperon proteins) involved in Lactobacillus attachment to human cell receptors [ 8 , 30 – 32 ].…”