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.The devastating diarrheal disease cholera is caused by the gram-negative, motile, curved-rod bacterium Vibrio cholerae (56). Over 200 serogroups of V. cholerae have been identified; however, epidemics are caused only by strains of serogroup O1 and the recently emerged serogroup O139 (27). Cholera is transmitted via the fecal-oral route. The infectious dose can vary tremendously, from 10 3 to 10 11 cells, depending on multiple factors, including the specific V. cholerae isolate as well as the diet, age, blood type, and health status of the patient (16,61,79). In addition, it has been recently reported that V. cholerae secreted by the host is more infectious than in vitrocultured V. cholerae (1,12,63). The existence of such a hyperinfectious state is supported by a mathematical model based on epidemiological data (41) and could help to explain the explosive nature of cholera outbreaks.Soon after oral ingestion, V. cholerae reaches the small bowel, its primary site of colonization, and induces virulence factors, such as toxin-coregulated pilus (TCP) and cholera toxin (CT) (17,42,87). A complex regulatory cascade including ToxT as well as the inner membrane proteins ToxR/S and TcpP/H controls the expression of virulence factors (54, 78). With the infant mouse and rabbit ileal loop animal models of infection, several factors of V. cholerae have been demonstrated to be important for colonization. Interestingly, a large number of these factors are associated with the outer membrane (OM), including lipopolysaccharide (LPS), OM porins (OMPs), TCP, and flagella (5,19,68,73,...

Acellular outer membrane vesicles of Brucella abortus strain 19 elicits both humoral and cell mediated immune response in mice

“…4). Immunogenic proteins of size between 35 to 45 kDa were reportedly seen in OMV of Vibrio cholera (Schild et al, 2008). Silver staining identified LPS in outer membrane vesicles of B. abortus which revealed both heavy and light silver-stained bands occurring within a repeating unit.…”

“…Discovered 40 years ago, the only licensed vaccine is Neisseiria meningitis vaccine used successfully in humans (Kimura et al, 2011). Vibrio cholera and Bordetella pertusis OMV elicit protection in mice model (Schild et al, 2008). OMV can be a vaccine candidate due to heterogeneous composition and diverse functions.…”

A Glimpse on Outer Membrane Vesicles as Vaccine Candidates

“…We successfully applied this strategy to isolate OMVs from a LPS acyltransferase mutant strain, demonstrating that reduction of OMV endotoxicity can be achieved without diminishing the immunogenic potential by genetic modification resulting in underacylated lipid A [10]. Overall, we demonstrated the induction of a specific, long-lasting, high-titer, protective immune response upon mucosal immunization of mice with V. cholerae OMVs [7,8]. Interestingly, throughout our studies protection against O1 and O139, representing the two clinically relevant serogroups of V. cholerae, was only achieved by immunization with a mixture of O1 and O139 OMVs.…”

Septic Shock by Gram-Negative Infections: Role of Outer Membrane Proteins

“…Thus, OMVs are likely a key factor in effecting an inflammatory response to pathogens, being immunogenic and capable of eliciting proinflammatory responses. Immunization with Vibrio cholera OMVs induces protection in mice (Schild, 2008); the OMVs immunized mice were protected against Salmonella infections (Alaniz, 2007). Furthermore, OMVs influence inflammation and disease in vivo; it was shown that, in response to Helicobacter pylori and Pseudomonas aeruginosa OMVs (Bauman, 2006), epithelial cells produce interleukin-8, a cytokine that plays a fundamental role in neutrophil and monocyte recruitment.…”