Oral Immunogenicity of Enterotoxigenic Escherichia coli Outer Membrane Vesicles Encapsulated into Zein Nanoparticles Coated with a Gantrez® AN–Mannosamine Polymer Conjugate

Abstract

Enterotoxigenic Escherichia coli (ETEC) represents a major cause of morbidity and mortality in the human population. In particular, ETEC infections affect children under the age of five from low-middle income countries. However, there is no licensed vaccine against this pathogen. ETEC vaccine development is challenging since this pathotype expresses a wide variety of antigenically diverse virulence factors whose genes can be modified due to ETEC genetic plasticity. To overcome this challenge, we propose the use of outer membrane vesicles (OMVs) isolated from two ETEC clinical strains. In these OMVs, proteomic studies revealed the presence of important immunogens, such as heat-labile toxin, colonization factors, adhesins and mucinases. Furthermore, these vesicles proved to be immunogenic after subcutaneous administration in BALB/c mice. Since ETEC is an enteropathogen, it is necessary to induce both systemic and mucosal immunity. For this purpose, the vesicles, free or encapsulated in zein nanoparticles coated with a Gantrez®–mannosamine conjugate, were administered orally. Biodistribution studies showed that the encapsulation of OMVs delayed the transit through the gut. These results were confirmed by in vivo study, in which OMV encapsulation resulted in higher levels of specific antibodies IgG2a. Further studies are needed to evaluate the protection efficacy of this vaccine approach.

Biodistribution of 89Zr-DFO-labeled avian pathogenic Escherichia coli outer membrane vesicles by PET imaging in chickens

“…The use of PET imaging allows qualitative and quantitative visualization of the presence of radiometabolites and free radioisotopes through radiotracers while offering the advantage of high sensitivity and noninvasive ( Patel et al., 2022 ). Berzosa et al attempted to develop radioisotope-labeled OMVs to assess biodistribution, but they only showed in-vitro biodistribution over 10 h, which was related to a 99 m Tc half-life of only 6 h ( Berzosa et al., 2022 ). Jang et al.…”

“…The ability of single photon emission computed tomography ( SPECT ) based detection of radioisotope-labeled OMVs has been used for in vivo tracing of OMVs of bacterial pathogens ( Berzosa et al., 2022 ). The technique of SPECT has excellent sensitivity for deep tissue imaging and allows quantitative measurements but is not superior in terms of spatial resolution and imaging time ( Choi et al., 2022 ).…”

Comparative study of subcutaneous, intramuscular, and oral administration of bovine pathogenic Escherichia coli bacterial ghost vaccine in mice

“…Oral immunization was more convenient than injection, but it is susceptible to loss and can lead to unstable immunological effects. Previous studies have demonstrated that outer membrane vesicles (OMVs) from E. coli encapsulated into Zein Nanoparticles coated with a Gantrez ® AN–Mannosamine Polymer Conjugate elicited high levels of IgG antibodies, while oral administration of the outer membrane protein alone did not elicit an antibody response ( 43 ). In contrast, displaying CD0873 on liposomes without encapsulation elicited significantly different IgG and IgA titers from the control group after three oral immunizations ( 44 ).…”

Vaccine development for bacterial pathogens: Advances, challenges and prospects

“…Recently, an OMV conjugated with a nanomaterial was shown to be highly effective against ETEC [165]. Also, in an investigation by Blackwood et al [166], a whole‐cell vaccine administered intranasally in a mice model reduced bacterial load and protected the mice against P. aeruginosa and B. pertussis .…”