A highly immunogenic vaccine platform against encapsulated pathogens using chimeric probiotic Escherichia coli membrane vesicles

Abstract

Vaccines against infectious diseases should elicit potent and long-lasting immunity, ideally even in those with age-related decline in immune response. Here we report a rational polysaccharide vaccine platform using probiotic Escherichia coli-derived membrane vesicles (MVs). First, we constructed a probiotic E. coli clone harboring the genetic locus responsible for biogenesis of serotype 14 pneumococcal capsular polysaccharides (CPS14) as a model antigen. CPS14 was found to be polymerized and mainly localized on the outer membrane of the E. coli cells. The glycine-induced MVs displayed the exogenous CPS14 at high density on the outermost surface, on which the CPS14 moiety was covalently tethered to a lipid A-core oligosaccharide anchor. In in vivo immunization experiments, CPS14+MVs, but not a mixture of free CPS14 and empty MVs, strongly elicited IgG class-switch recombination with a Th1/Th2-balanced IgG subclass distribution without any adjuvant. In addition, CPS14+MVs were structurally stable with heat treatment and immunization with the heat-treated MVs-elicited CPS14-specific antibody responses in mouse serum to levels comparable to those of non-treated CPS14+MVs. Notably, the immunogenicity of CPS14+MVs was significantly stronger than those of two currently licensed vaccines against pneumococci. The CPS14+MV-elicited humoral immune responses persisted for 1 year in both blood and lung. Furthermore, the CPS14+MV vaccine was widely efficacious in mice of different ages. Even in aged mice, vaccination resulted in robust production of CPS14-specific IgG that bound to the pneumococcal cell surface. Taken together, the present probiotic E. coli MVs-based vaccine platform offers a promising, generalizable solution against encapsulated pathogens.

Extracellular Vesicles of Probiotics: Shedding Light on the Biological Activity and Future Applications

“…These studies showed the protective effect of probiotic EVs on atopic dermatitis [ 139 ] and various intestinal pathologies (chemoresistant colorectal cancer [ 140 ] or intestinal infections made by enterotoxigenic E. coli [ 141 ]). It was also noticed that probiotic EVs have a strong immunomodulatory effect on the human body (including the intestines) [ 142 ], and that they can be used in the design of innovative vaccines against infectious diseases [ 143 ] and cancers [ 122 ]. In the last publication, attention was drawn to the participation of prophages in the secretion of EVs by the tested probiotic bacteria [ 144 ].…”

Mucosal adjuvanticity and mucosal booster effect of colibactin-depleted probiotic Escherichia coli membrane vesicles

“…MVs were isolated from supernatant from a 16-hour bacterial culture of EcNΔ flhD derivatives using a glycine induction method, 21 , 31 as described previously. 10 Isolated MVs were resuspended in 20 mM Tris-HCl (pH 8.0) and stored at -20°C. The protein concentration of MVs was determined using a Bradford assay 32 with bovine serum albumin (BSA) as the standard.…”

“… 9 We have recently characterized probiotic EcN chimera-derived MVs displaying serotype-14 pneumococcal capsular polysaccharide CPS14 at high density (CPS14 + MVs), which elicit potent IgG-dominant immune responses when subcutaneously (SC) administered. 10 …”

“… 14 The CPS14 + MV vaccine via SC route caused IgG production in blood, but failed to elicit IgA responses. 10 Based on these thoughts, it is interesting to examine whether IN booster with CPS14 + MVs elicits robust immune responses and/or triggers class-switch recombination (CSR) to not only IgG but also IgA in mice that have already been SC prime-immunized with the same MVs, when compared to the homologous SC administration.…”

Bacterial membrane vesicles in the pathogenesis and treatment of inflammatory bowel disease

“…The study revealed that the probiotic E. coli MVs-based vaccine platform provides a viable, broadly applicable defense against encapsulated pathogens. 174 Although there are still debates on the possible involvement of Mycobacterium avium subspecies paratuberculosis (MAP) in the onset of CD, Aitken et al successfully identified this organism in excised tissues of 18 IBD patients, with none detected in the 15 samples of non-IBD control. 175 A recent, in silico vaccine design from MVs derived from MAP, showed that the multi-epitope vaccine obtained by stitching antigenic, immunogenic, and IFN-γ-inducing B-cell, MHC-I, and MHC-II epitopes through linkers could be a promising vaccine candidate against MAP, although both in vitro and in vivo experiments are required for solid confirmation.…”