{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,8]],"date-time":"2026-10-08T17:49:51Z","timestamp":1791481791309,"version":"4.3.4"},"reference-count":46,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2023,11,7]],"date-time":"2023-11-07T00:00:00Z","timestamp":1699315200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100007137","name":"Northern Norway Regional Health Authority Medical Research Programme","doi-asserted-by":"publisher","award":["HNF1474-19"],"award-info":[{"award-number":["HNF1474-19"]}],"id":[{"id":"10.13039\/501100007137","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Norwegian Surveillance Programme for Antimicrobial Resistance (NORM)","award":["HNF1474-19"],"award-info":[{"award-number":["HNF1474-19"]}]},{"name":"Institute for Medical Biology at UiT","award":["HNF1474-19"],"award-info":[{"award-number":["HNF1474-19"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Enterococcus faecium is a leading cause of nosocomial infections, particularly in immunocompromised patients. The rise of multidrug-resistant E. faecium, including Vancomycin-Resistant Enterococci (VRE), is a major concern. Vaccines are promising alternatives to antibiotics, but there is currently no vaccine available against enterococci. In a previous study, we identified six protein vaccine candidates associated with extracellular membrane vesicles (MVs) produced by nosocomial E. faecium. In this study, we immunized rabbits with two different VRE-derived MV preparations and characterized the resulting immune sera. Both anti-MV sera exhibited high immunoreactivity towards the homologous strain, three additional VRE strains, and eight different unrelated E.\u00a0faecium strains representing different sequence types (STs). Additionally, we demonstrated that the two anti-MV sera were able to mediate opsonophagocytic killing of not only the homologous strain but also three unrelated heterologous VRE strains. Altogether, our results indicate that E.\u00a0faecium MVs, regardless of the purification method for obtaining them, are promising vaccine candidates against multidrug-resistant E. faecium and suggest that these naturally occurring MVs can be used as a multi-antigen platform to elicit protective immune responses against enterococcal infections.<\/jats:p>","DOI":"10.3390\/ijms242216051","type":"journal-article","created":{"date-parts":[[2023,11,7]],"date-time":"2023-11-07T11:23:39Z","timestamp":1699356219000},"page":"16051","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":20,"title":["Enterococcal Membrane Vesicles as Vaccine Candidates"],"prefix":"10.3390","volume":"24","author":[{"given":"Theresa Maria","family":"Wagner","sequence":"first","affiliation":[{"name":"Research Group for Host-Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, N-9037 Troms\u00f8, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3134-7018","authenticated-orcid":false,"given":"Felipe","family":"Romero-Saavedra","sequence":"additional","affiliation":[{"name":"Division of Pediatric Infectious Diseases, Dr. von Hauner Children\u2019s Hospital, Ludwig Maximilians University, 80337 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Diana","family":"Laverde","sequence":"additional","affiliation":[{"name":"Division of Pediatric Infectious Diseases, Dr. von Hauner Children\u2019s Hospital, Ludwig Maximilians University, 80337 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mona","family":"Johannessen","sequence":"additional","affiliation":[{"name":"Research Group for Host-Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, N-9037 Troms\u00f8, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Johannes","family":"H\u00fcbner","sequence":"additional","affiliation":[{"name":"Division of Pediatric Infectious Diseases, Dr. von Hauner Children\u2019s Hospital, Ludwig Maximilians University, 80337 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1314-0497","authenticated-orcid":false,"given":"Kristin","family":"Hegstad","sequence":"additional","affiliation":[{"name":"Research Group for Host-Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, N-9037 Troms\u00f8, Norway"},{"name":"Norwegian National Advisory Unit on Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North Norway, N-9038 Troms\u00f8, Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,11,7]]},"reference":[{"key":"ref_1","unstructured":"WHO Regional Office for Europe, and European Centre for Disease Prevention and Control (2022). Antimicrobial Resistance Surveillance in Europe 2022\u20132020 Data, WHO Regional Office for Europe."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"eaar6115","DOI":"10.1126\/scitranslmed.aar6115","article-title":"Increasing Tolerance of Hospital Enterococcus faecium to Handwash Alcohols","volume":"10","author":"Pidot","year":"2018","journal-title":"Sci. Transl. Med."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"266","DOI":"10.1038\/nrmicro2761","article-title":"The Rise of the Enterococcus: Beyond Vancomycin Resistance","volume":"10","author":"Arias","year":"2012","journal-title":"Nat. Rev. Microbiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1901","DOI":"10.1007\/s10096-015-2430-x","article-title":"Environmental Survival of Vancomycin-Sensitive Ampicillin-Resistant Enterococcus faecium (AREfm)","volume":"34","author":"Wagenvoort","year":"2015","journal-title":"Eur. J. Clin. Microbiol. Infect. Dis."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e00276-19","DOI":"10.1128\/IAI.00276-19","article-title":"Development of Opsonic Mouse Monoclonal Antibodies against Multidrug Resistant Enterococci","volume":"87","author":"Kalfopoulou","year":"2019","journal-title":"Infect. Immun."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"3429","DOI":"10.1099\/mic.0.053207-0","article-title":"Identification of SagA as a Novel Vaccine Target for the Prevention of Enterococcus faecium Infections","volume":"157","author":"Kropec","year":"2011","journal-title":"Microbiology"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Romero-Saavedra, F., Laverde, D., Budin-Verneuil, A., Muller, C., Bernay, B., Benachour, A., Hartke, A., and Huebner, J. (2015). Characterization of Two Metal Binding Lipoproteins as Vaccine Candidates for Enterococcal Infections. PLoS ONE, 10.","DOI":"10.1371\/journal.pone.0136625"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Romero-Saavedra, F., Laverde, D., Wobser, D., Michaux, C., Budin-Verneuil, A., Bernay, B., Benachour, A., Hartke, A., and Huebner, J. (2014). Identification of Peptidoglycan-Associated Proteins as Vaccine Candidates for Enterococcal Infections. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0111880"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1816","DOI":"10.1021\/acsinfecdis.0c00063","article-title":"Synthetic Oligomers Mimicking Capsular Polysaccharide Diheteroglycan Are Potential Vaccine Candidates against Encapsulated Enterococcal Infections","volume":"6","author":"Laverde","year":"2020","journal-title":"ACS Infect. Dis."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Theilacker, C., Kaczy\u0144ski, Z., Kropec, A., Sava, I., Ye, L., Bychowska, A., Holst, O., and Huebner, J. (2011). Serodiversity of Opsonic Antibodies against Enterococcus faecalis\u2014Glycans of the Cell Wall Revisited. PLoS ONE, 6.","DOI":"10.1371\/journal.pone.0017839"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/S0008-6215(99)00046-4","article-title":"Structure of an Antigenic Teichoic Acid Shared by Clinical Isolates of Enterococcus faecalis and Vancomycin-Resistant Enterococcus faecium","volume":"316","author":"Wang","year":"1999","journal-title":"Carbohydr. Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1016\/j.jprot.2018.05.017","article-title":"Enterococcus faecium Produces Membrane Vesicles Containing Virulence Factors and Antimicrobial Resistance Related Proteins","volume":"187","author":"Wagner","year":"2018","journal-title":"J. Proteom."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1038\/nri3837","article-title":"Immune Modulation by Bacterial Outer Membrane Vesicles","volume":"15","author":"Ferrero","year":"2015","journal-title":"Nat. Rev. Immunol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1689","DOI":"10.1002\/biot.201400395","article-title":"Outer Membrane Vesicles as Platform Vaccine Technology","volume":"10","author":"Stork","year":"2015","journal-title":"Biotechnol. J."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"825","DOI":"10.1016\/S0140-6736(12)61961-8","article-title":"Immunogenicity and Safety of an Investigational Multicomponent, Recombinant, Meningococcal Serogroup B Vaccine (4CMenB) Administered Concomitantly with Routine Infant and Child Vaccinations: Results of Two Randomised Trials","volume":"381","author":"Vesikari","year":"2013","journal-title":"Lancet"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1093","DOI":"10.1016\/0140-6736(91)91961-S","article-title":"Effect of Outer Membrane Vesicle Vaccine against Group B Meningococcal Disease in Norway","volume":"338","author":"Bjune","year":"1991","journal-title":"Lancet"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Choi, C.-W., Park, E.C., Yun, S.H., Lee, S.-Y., Kim, S.I., and Kim, G.-H. (2017, December 11). Potential Usefulness of Streptococcus pneumoniae Extracellular Membrane Vesicles as Antibacterial Vaccines. Available online: https:\/\/www.hindawi.com\/journals\/jir\/2017\/7931982\/.","DOI":"10.1155\/2017\/7931982"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Choi, S.J., Kim, M.-H., Jeon, J., Kim, O.Y., Choi, Y., Seo, J., Hong, S.-W., Lee, W.-H., Jeon, S.G., and Gho, Y.S. (2015). Active Immunization with Extracellular Vesicles Derived from Staphylococcus aureus Effectively Protects against Staphylococcal Lung Infections, Mainly via Th1 Cell-Mediated Immunity. PLoS ONE, 10.","DOI":"10.1371\/journal.pone.0136021"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Askarian, F.-, Lapek, J.J., Dongre, M., Tsai, C.-M., Kumaraswamy, M., Kousha, A., Valderrama, J.A., Ludviksen, J.A., Cavanagh, P., and Uchiyama, S. (2018). Staphylococcus aureus Membrane-Derived Vesicles Promote Bacterial Virulence and Confer Protective Immunity in Murine Infection Models. Front. Microbiol., 9.","DOI":"10.3389\/fmicb.2018.00262"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1584","DOI":"10.1002\/eji.201646632","article-title":"Guidelines for the Use of Flow Cytometry and Cell Sorting in Immunological Studies","volume":"47","author":"Cossarizza","year":"2017","journal-title":"Eur. J. Immunol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1589","DOI":"10.1093\/infdis\/jiz357","article-title":"Conjugation of Different Immunogenic Enterococcal Vaccine Target Antigens Leads to Extended Strain Coverage","volume":"220","author":"Laverde","year":"2019","journal-title":"J. Infect. Dis."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.drup.2018.10.002","article-title":"Update on Prevalence and Mechanisms of Resistance to Linezolid, Tigecycline and Daptomycin in Enterococci in Europe: Towards a Common Nomenclature","volume":"40","author":"Bender","year":"2018","journal-title":"Drug Resist. Updat."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Poudel, A.N., Zhu, S., Cooper, N., Little, P., Tarrant, C., Hickman, M., and Yao, G. (2023). The Economic Burden of Antibiotic Resistance: A Systematic Review and Meta-Analysis. PLoS ONE, 18.","DOI":"10.1371\/journal.pone.0285170"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1086\/430909","article-title":"Comparison of Mortality Associated with Vancomycin-Resistant and Vancomycin-Susceptible Enterococcal Bloodstream Infections: A Meta-Analysis","volume":"41","author":"DiazGranados","year":"2005","journal-title":"Clin. Infect. Dis."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"435","DOI":"10.1016\/j.jhin.2019.08.014","article-title":"Enterococcus hirae, Enterococcus faecium and Enterococcus faecalis Show Different Sensitivities to Typical Biocidal Agents Used for Disinfection","volume":"103","author":"Suchomel","year":"2019","journal-title":"J. Hosp. Infect."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Geraldes, C., Tavares, L., Gil, S., and Oliveira, M. (2022). Enterococcus Virulence and Resistant Traits Associated with Its Permanence in the Hospital Environment. Antibiotics, 11.","DOI":"10.3390\/antibiotics11070857"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Kalfopoulou, E., and Huebner, J. (2020). Advances and Prospects in Vaccine Development against Enterococci. Cells, 9.","DOI":"10.3390\/cells9112397"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Lieberman, L.A. (2022). Outer Membrane Vesicles: A Bacterial-Derived Vaccination System. Front. Microbiol., 13.","DOI":"10.3389\/fmicb.2022.1029146"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"101433","DOI":"10.1016\/j.smim.2020.101433","article-title":"Outer Membrane Vesicle Vaccines","volume":"50","author":"Micoli","year":"2020","journal-title":"Semin. Immunol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"5262","DOI":"10.1016\/j.vaccine.2013.08.059","article-title":"Outer Membrane Vesicles Derived from Bordetella parapertussis as an Acellular Vaccine against Bordetella parapertussis and Bordetella pertussis Infection","volume":"31","author":"Bottero","year":"2013","journal-title":"Vaccine"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"472","DOI":"10.1128\/IAI.01139-08","article-title":"Characterization of Vibrio cholerae Outer Membrane Vesicles as a Candidate Vaccine for Cholera","volume":"77","author":"Schild","year":"2009","journal-title":"Infect. Immun."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Leitner, D.R., Lichtenegger, S., Temel, P., Zingl, F.G., Ratzberger, D., Roier, S., Schild-Pr\u00fcfert, K., Feichter, S., Reidl, J., and Schild, S. (2015). A Combined Vaccine Approach against Vibrio cholerae and ETEC Based on Outer Membrane Vesicles. Front. Microbiol., 6.","DOI":"10.3389\/fmicb.2015.00823"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"McCaig, W.D., Loving, C.L., Hughes, H.R., and Brockmeier, S.L. (2016). Characterization and Vaccine Potential of Outer Membrane Vesicles Produced by Haemophilus parasuis. PLoS ONE, 11.","DOI":"10.1371\/journal.pone.0149132"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"22324","DOI":"10.1038\/s41598-022-26846-z","article-title":"Pseudomonas aeruginosa PAO1 Outer Membrane Vesicles-Diphtheria Toxoid Conjugate as a Vaccine Candidate in a Murine Burn Model","volume":"12","author":"Rasooli","year":"2022","journal-title":"Sci. Rep."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"5705","DOI":"10.1016\/j.vaccine.2011.06.001","article-title":"Outer Membrane Vesicles as an Acellular Vaccine against Acinetobacter baumannii","volume":"29","author":"McConnell","year":"2011","journal-title":"Vaccine"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"e00699-20","DOI":"10.1128\/IAI.00699-20","article-title":"Salmonella Paratyphi A Outer Membrane Vesicles Displaying Vi Polysaccharide as a Multivalent Vaccine against Enteric Fever","volume":"89","author":"Gasperini","year":"2021","journal-title":"Infect. Immun."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Behrens, F., Funk-Hilsdorf, T.C., Kuebler, W.M., and Simmons, S. (2021). Bacterial Membrane Vesicles in Pneumonia: From Mediators of Virulence to Innovative Vaccine Candidates. Int. J. Mol. Sci., 22.","DOI":"10.3390\/ijms22083858"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"752168","DOI":"10.3389\/fimmu.2021.752168","article-title":"Multi-Antigen Outer Membrane Vesicle Engineering to Develop Polyvalent Vaccines: The Staphylococcus aureus Case","volume":"12","author":"Gagliardi","year":"2021","journal-title":"Front. Immunol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"uqab002","DOI":"10.1093\/femsml\/uqab002","article-title":"The Composition and Function of Enterococcus faecalis Membrane Vesicles","volume":"2","author":"Afonina","year":"2021","journal-title":"Microlife"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"5033","DOI":"10.1128\/IAI.71.9.5033-5041.2003","article-title":"An Enterococcus faecium Secreted Antigen, SagA, Exhibits Broad-Spectrum Binding to Extracellular Matrix Proteins and Appears Essential for E. faecium Growth","volume":"71","author":"Teng","year":"2003","journal-title":"Infect. Immun."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Micoli, F., Adamo, R., and Costantino, P. (2018). Protein Carriers for Glycoconjugate Vaccines: History, Selection Criteria, Characterization and New Trends. Molecules, 23.","DOI":"10.3390\/molecules23061451"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"100732","DOI":"10.1016\/j.drup.2020.100732","article-title":"Thirty Years of VRE in Germany\u2014\u201cExpect the Unexpected\u201d: The View from the National Reference Centre for Staphylococci and Enterococci","volume":"53","author":"Werner","year":"2020","journal-title":"Drug Resist. Updates"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1524","DOI":"10.1093\/gbe\/evt111","article-title":"Recent Recombination Events in the Core Genome Are Associated with Adaptive Evolution in Enterococcus faecium","volume":"5","author":"Cheng","year":"2013","journal-title":"Genome Biol. Evol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1213","DOI":"10.1128\/IAI.67.3.1213-1219.1999","article-title":"Isolation and Chemical Characterization of a Capsular Polysaccharide Antigen Shared by Clinical Isolates of Enterococcus faecalis and Vancomycin-Resistant Enterococcus faecium","volume":"67","author":"Huebner","year":"1999","journal-title":"Infect. Immun."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"2469","DOI":"10.1128\/JB.00153-10","article-title":"High-Quality Draft Genome Sequences of 28 Enterococcus Sp. Isolates","volume":"192","author":"Palmer","year":"2010","journal-title":"J. Bacteriol."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Rossmann, F.S., Laverde, D., Kropec, A., Romero-Saavedra, F., Meyer-Buehn, M., and Huebner, J. (2015). Isolation of Highly Active Monoclonal Antibodies against Multiresistant Gram-Positive Bacteria. PLoS ONE, 10.","DOI":"10.1371\/journal.pone.0118405"}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/24\/22\/16051\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:18:53Z","timestamp":1760131133000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/24\/22\/16051"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,11,7]]},"references-count":46,"journal-issue":{"issue":"22","published-online":{"date-parts":[[2023,11]]}},"alternative-id":["ijms242216051"],"URL":"https:\/\/doi.org\/10.3390\/ijms242216051","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,11,7]]}}}