title: Characterization of Two Metal Binding Lipoproteins as Vaccine Candidates for Enterococcal Infections.
abstract: BACKGROUND
  Enterococcus faecium and faecalis are Gram-positive opportunistic pathogens that have become leading causes of nosocomial infections over the last decades. Especially multidrug resistant enterococci have become a challenging clinical problem worldwide. Therefore, new treatment options are needed and the identification of alternative targets for vaccine development has emerged as a feasible alternative to fight the infections caused by these pathogens.
  
  
  RESULTS
  We extrapolate the transcriptomic data from a mice peritonitis infection model in E. faecalis to identify putative up-regulated surface proteins under infection conditions in E. faecium. After the bionformatic analyses two metal binding lipoproteins were identified to have a high homology (>72%) between the two species, the manganese ABC transporter substrate-binding lipoprotein (PsaAfm,) and the zinc ABC transporter substrate-binding lipoprotein (AdcAfm). These candidate lipoproteins were overexpressed in Escherichia coli and purified. The recombinant proteins were used to produce rabbit polyclonal antibodies that were able to induce specific opsonic antibodies that mediated killing of the homologous strain E. faecium E155 as well as clinical strains E. faecium E1162, Enterococcus faecalis 12030, type 2 and type 5. Mice were passively immunized with the antibodies raised against recombinant lipoproteins, showing significant reduction of colony counts in mice livers after the bacterial challenge and demonstrating the efficacy of these metal binding lipoproteins as promising vaccine candidates to treat infections caused by these enterococcal pathogens.
  
  
  CONCLUSIONS
  Overall, our results demonstrate that these two metal binding lipoproteins elicited specific, opsonic and protective antibodies, with an extensive cross-reactivity and serotype-independent coverage among these two important nocosomial pathogens. Pointing these two protein antigens as promising immunogens, that can be used as single components or as carrier proteins together with polysaccharide antigens in vaccine development against enterococcal infections.
authors: Division of Infectious Diseases, Department of Medicine, University Medical Center Freiburg, Freiburg, Germany; EA4655 U2RM Stress/Virulence, University of Caen Lower-Normandy, Caen, France.
authors: Felipe
authors: F
authors: Romero-Saavedra
authors: Division of Infectious Diseases, Department of Medicine, University Medical Center Freiburg, Freiburg, Germany; EA4655 U2RM Stress/Virulence, University of Caen Lower-Normandy, Caen, France.
authors: Diana
authors: D
authors: Laverde
authors: EA4655 U2RM Stress/Virulence, University of Caen Lower-Normandy, Caen, France.
authors: Aurélie
authors: A
authors: Budin-Verneuil
authors: EA4655 U2RM Stress/Virulence, University of Caen Lower-Normandy, Caen, France.
authors: Cécile
authors: C
authors: Muller
authors: Proteogen platform SFR ICORE 4206, University of Caen Lower-Normandy, Caen, France.
authors: Benoit
authors: B
authors: Bernay
authors: EA4655 U2RM Stress/Virulence, University of Caen Lower-Normandy, Caen, France.
authors: Abdellah
authors: A
authors: Benachour
authors: EA4655 U2RM Stress/Virulence, University of Caen Lower-Normandy, Caen, France.
authors: Axel
authors: A
authors: Hartke
authors: Division of Infectious Diseases, Department of Medicine, University Medical Center Freiburg, Freiburg, Germany; Division of Pediatric Infectious Diseases, Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, Germany.
authors: Johannes
authors: J
authors: Huebner
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000276:immunology*; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000276:immunology; D001428:Bacterial Vaccines / Q000276:immunology*; D027682:Cation Transport Proteins / Q000276:immunology; D013293:Enterococcus faecalis / Q000276:immunology*; D016984:Enterococcus faecium / Q000276:immunology*; D005260:Female; D016908:Gram-Positive Bacterial Infections / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D007074:Immunoglobulin G / Q000097:blood; D008074:Lipoproteins / Q000276:immunology*; D008345:Manganese / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D009895:Opsonin Proteins / Q000276:immunology; D010538:Peritonitis / Q000382:microbiology; D010587:Phagocytosis / Q000276:immunology; D014611:Vaccination; D015032:Zinc / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D027682:Cation Transport Proteins; D007074:Immunoglobulin G; D008074:Lipoproteins; D009895:Opsonin Proteins; D008345:Manganese; D015032:Zinc