Characterization and vaccine potential of membrane vesicles produced by Francisella noatunensis subsp. orientalis in an adult zebrafish model

Leidy Lagos, Julia I. Tandberg, Urska Repnik, Preben Boysen, Erik Ropstad, Deepa Varkey, Ian T. Paulsen, Hanne C. Winther-Larsen*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    28 Citations (Scopus)


    Vaccine development against extracellular bacteria has been important for the sustainability of the aquaculture industry. In contrast, infections with intracellular pathogens remain largely an unresolved problem. Francisella noatunensis subsp. orientalis is a Gram-negative, facultative intracellular bacterium that causes the disease francisellosis in fish. Francisellosis is commonly characterized as a chronic granulomatous disease with high morbidity and can result in high mortality depending on the host. In this study, we explored the potential of bacterial membrane vesicles (MVs) as a vaccine agent against F. noatunensis subsp. orientalis. Bacterial MVs are spherical structures naturally released from the membrane of bacteria and are often enriched with selected bacterial components such as toxins and signaling molecules. MVs were isolated from broth-cultured F. noatunensis subsp. orientalis in the present work, and proteomic analysis by mass spectrometry revealed that MVs contained a variety of immunogenic factors, including the intracellular growth proteins IglC and IglB, known to be part of a Francisella pathogenicity island (FPI), as well as outer membrane protein OmpA, chaperonin GroEL, and chaperone ClpB. By using flow cytometry and electron microscopy, we observed that F. noatunensis subsp. orientalis mainly infects myelomonocytic cells, both in vivo and in vitro. Immunization with MVs isolated from F. noatunensis subsp. orientalis protects zebrafish from subsequent challenge with a lethal dose of F. noatunensis subsp. orientalis. To determine if MVs induce a typical acute inflammatory response, mRNA expression levels were assessed by quantitative real-time PCR. Expression of tnfa, il1b, and ifng, as well as mhcii, mpeg1.1, and ighm, was upregulated, thus confirming the immunogenic properties of F. noatunensis subsp. orientalis-derived MVs.

    Original languageEnglish
    Article numbere00557-16
    Pages (from-to)1-19
    Number of pages19
    JournalClinical and Vaccine Immunology
    Issue number5
    Publication statusPublished - 1 May 2017

    Bibliographical note

    Copyright the Author(s) 2017. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


    • Fish pathogens
    • Francisella noatunensis subsp. orientalis
    • Francisellosis
    • Immune response
    • Immunization
    • Immunology
    • Membrane vesicles
    • MVs
    • Vaccine
    • Zebrafish


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