Immunization with Vibrio cholerae Outer Membrane Vesicles Induces Protective Immunity in Mice

ABSTRACT The gram-negative bacterium Vibrio cholerae releases outer membrane vesicles (OMVs) during growth. In this study, we immunized female mice by the intranasal, intragastric, or intraperitoneal route with purified OMVs derived from V. cholerae. Independent of the route of immunization, mice induced specific, high-titer immune responses of similar levels against a variety of antigens present in the OMVs. After the last immunization, the half-maximum total immunoglobulin titer was stable over a 3-month period, indicating that the immune response was long lasting. The induction of specific isotypes, however, was dependent on the immunization route. Immunoglobulin A, for example, was induced to a significant level only by mucosal immunization, with the intranasal route generating the highest titers. We challenged the offspring of immunized female mice with V. cholerae via the oral route in two consecutive periods, approximately 30 and 95 days after the last immunization. Regardless of the route of immunization, the offspring was protected against colonization with V. cholerae in both challenge periods. Our results show that mucosal immunizations via both routes with OMVs derived from V. cholerae induce long-term protective immune responses against this gastrointestinal pathogen. These findings may contribute to the development of “nonliving,” OMV-based vaccines against V. cholerae and other enteric pathogens, using the oral or intranasal route of immunization.

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Comparative study of immune responses elicited by outer membrane vesicles of different Pseudomonas aeruginosa strains

Comparative Immunology Microbiology and Infectious Diseases ◽

10.1016/j.cimid.2019.101328 ◽

2019 ◽

Vol 66 ◽

pp. 101328 ◽

Cited By ~ 1

Author(s):

Fereshteh Satarian ◽

Taher Nejadsattari ◽

Farzam Vaziri ◽

Seyed Davar Siadat

Keyword(s):

Pseudomonas Aeruginosa ◽

Immune Responses ◽

Comparative Study ◽

Outer Membrane ◽

Membrane Vesicles ◽

Outer Membrane Vesicles

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Cholera Toxin Encapsulated within Several Vibrio cholerae O1 Serotype Inaba Outer Membrane Vesicles Lacks a Functional B-Subunit

Toxins ◽

10.3390/toxins11040207 ◽

2019 ◽

Vol 11 (4) ◽

pp. 207 ◽

Cited By ~ 2

Author(s):

Elnaz Rasti ◽

Angela Brown

Keyword(s):

Outer Membrane ◽

Cholera Toxin ◽

Vibrio Cholerae ◽

Membrane Vesicles ◽

Outer Membrane Vesicles ◽

Biologically Active ◽

Host Cells ◽

Free Form ◽

Type Ii Secretion ◽

Secondary Mechanism

Cholera toxin (CT), the major virulence factor of Vibrio cholerae, is an AB5 toxin secreted through the type II secretion system (T2SS). Upon secretion, the toxin initiates endocytosis through the interaction of the B pentamer with the GM1 ganglioside receptor on small intestinal cells. In addition to the release of CT in the free form, the bacteria secrete CT in association with outer membrane vesicles (OMVs). Previously, we demonstrated that strain 569B releases OMVs that encapsulate CT and which interact with host cells in a GM1-independent mechanism. Here, we have demonstrated that OMV-encapsulated CT, while biologically active, does not exist in an AB5 form; rather, the OMVs encapsulate two enzymatic A-subunit (CTA) polypeptides. We further investigated the assembly and secretion of the periplasmic CT and found that a major fraction of periplasmic CTA does not participate in the CT assembly process and instead is continuously encapsulated within the OMVs. Additionally, we found that the encapsulation of CTA fragments in OMVs is conserved among several Inaba O1 strains. We further found that under conditions in which the amount of extracellularly secreted CT increases, the concentration of OMV-encapsulated likewise CTA increases. These results point to a secondary mechanism for the secretion of biologically active CT that does not depend on the CTB-GM1 interaction for endocytosis.

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Naturally Occurring IgG Antibodies Provide Innate Protection against Vibrio cholerae Bacteremia by Recognition of the Outer Membrane Protein U

Journal of Innate Immunity ◽

10.1159/000443646 ◽

2016 ◽

Vol 8 (3) ◽

pp. 269-283 ◽

Cited By ~ 17

Author(s):

Kyaw Min Aung ◽

Annika E. Sjöström ◽

Ulrich von Pawel-Rammingen ◽

Kristian Riesbeck ◽

Bernt Eric Uhlin ◽

...

Keyword(s):

Membrane Protein ◽

Outer Membrane ◽

Vibrio Cholerae ◽

Outer Membrane Protein ◽

Membrane Vesicles ◽

Outer Membrane Vesicles ◽

Immune Defense ◽

Dependent Manner ◽

Naturally Occurring ◽

Serum Killing

Cholera epidemics are caused by Vibrio cholerae serogroups O1 and O139, whereas strains collectively known as non-O1/non-O139 V. cholerae are found in cases of extraintestinal infections and bacteremia. The mechanisms and factors influencing the occurrence of bacteremia and survival of V. cholerae in normal human serum have remained unclear. We found that naturally occurring IgG recognizing V. cholerae outer membrane protein U (OmpU) mediates a serum-killing effect in a complement C1q-dependent manner. Moreover, outer membrane vesicles (OMVs) containing OmpU caused enhanced survival of highly serum-sensitive classical V. cholerae in a dose-dependent manner. OMVs from wild-type and ompU mutant V. cholerae thereby provided a novel means to verify by extracellular transcomplementation the involvement of OmpU. Our data conclusively indicate that loss, or reduced expression, of OmpU imparts resistance to V. cholerae towards serum killing. We propose that the difference in OmpU protein levels is a plausible reason for differences in serum resistance and the ability to cause bacteremia observed among V. cholerae biotypes. Our findings provide a new perspective on how naturally occurring antibodies, perhaps induced by members of the microbiome, may play a role in the recognition of pathogens and the provocation of innate immune defense against bacteremia.

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Decoration of Outer Membrane Vesicles with Multiple Antigens by Using an Autotransporter Approach

Applied and Environmental Microbiology ◽

10.1128/aem.01941-14 ◽

2014 ◽

Vol 80 (18) ◽

pp. 5854-5865 ◽

Cited By ~ 41

Author(s):

Maria H. Daleke-Schermerhorn ◽

Tristan Felix ◽

Zora Soprova ◽

Corinne M. ten Hagen-Jongman ◽

David Vikström ◽

...

Keyword(s):

Immune Responses ◽

Outer Membrane ◽

Vaccine Development ◽

Membrane Vesicles ◽

Outer Membrane Vesicles ◽

Heterologous Proteins ◽

Content Type ◽

Serovar Typhimurium ◽

Heterologous Antigens

ABSTRACTOuter membrane vesicles (OMVs) are spherical nanoparticles that naturally shed from Gram-negative bacteria. They are rich in immunostimulatory proteins and lipopolysaccharide but do not replicate, which increases their safety profile and renders them attractive vaccine vectors. By packaging foreign polypeptides in OMVs, specific immune responses can be raised toward heterologous antigens in the context of an intrinsic adjuvant. Antigens exposed at the vesicle surface have been suggested to elicit protection superior to that from antigens concealed inside OMVs, but hitherto robust methods for targeting heterologous proteins to the OMV surface have been lacking. We have exploited our previously developed hemoglobin protease (Hbp) autotransporter platform for display of heterologous polypeptides at the OMV surface. One, two, or three of theMycobacterium tuberculosisantigens ESAT6, Ag85B, and Rv2660c were targeted to the surface ofEscherichia coliOMVs upon fusion to Hbp. Furthermore, a hypervesiculating ΔtolRΔtolAderivative of attenuatedSalmonella entericaserovar Typhimurium SL3261 was generated, enabling efficient release and purification of OMVs decorated with multiple heterologous antigens, exemplified by theM. tuberculosisantigens and epitopes fromChlamydia trachomatismajor outer membrane protein (MOMP). Also, we showed that delivery ofSalmonellaOMVs displaying Ag85B to antigen-presenting cellsin vitroresults in processing and presentation of an epitope that is functionally recognized by Ag85B-specific T cell hybridomas. In conclusion, the Hbp platform mediates efficient display of (multiple) heterologous antigens, individually or combined within one molecule, at the surface of OMVs. Detection of antigen-specific immune responses upon vesicle-mediated delivery demonstrated the potential of our system for vaccine development.

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