title: Listeria monocytogenes as a vaccine vector: virulence attenuation or existing antivector immunity does not diminish therapeutic efficacy.
abstract: The bacterium L. monocytogenes is a proposed vaccine carrier based upon the observation that this pathogen replicates within the intracytoplasmic environment facilitating delivery of Ag to the endogenous Ag processing and presentation pathway with subsequent stimulation of peptide specific MHC class I-restricted CD8(+) effector cells. In this report, we evaluate virulence-attenuated strains of Listeria monocytogenes as vaccine vectors and examine whether existing antivector (antilisterial) immunity limits or alters its efficacy as a therapeutic cancer vaccine. Following immunization with virulence-attenuated mutants, we found that the effectiveness of L. monocytogenes as a recombinant cancer vaccine remains intact. In addition, we found that antibiotic treatment initiated 24 or 36 h following therapeutic immunization with recombinant L. monocytogenes allows full development of the antitumor response. We also demonstrate that the vaccine vector potential of L. monocytogenes is not limited in animals with existing antilisterial immunity. For these latter studies, mice previously immunized with wild-type L. monocytogenes were infused with melanoma cells and then 5 days later challenged with recombinant tumor Ag expressing L. monocytogenes. Collectively, these results add additional support for the use of L. monocytogenes as a vaccine vector and underscore its potential to be used repeatedly for stimulation of recall responses concomitant with primary cell-mediated responses to newly delivered heterologous tumor-associated epitopes.
authors.affiliation: Veterans Affairs Medical Center, Earle A. Chiles Research Institute, Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, Portland, OR 97201, USA.
authors.forename: Holly
authors.initials: H
authors.lastname: Starks
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Bruhn
authors.forename: Hao
authors.initials: H
authors.lastname: Shen
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Barry
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Dubensky
authors.forename: Dirk
authors.initials: D
authors.lastname: Brockstedt
authors.forename: David J
authors.initials: DJ
authors.lastname: Hinrichs
authors.forename: Darren E
authors.initials: DE
authors.lastname: Higgins
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Miller
authors.forename: Martin
authors.initials: M
authors.lastname: Giedlin
authors.forename: H G Archie
authors.initials: HG
authors.lastname: Bouwer
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D019496:Cancer Vaccines / Q000627:therapeutic use*; D002460:Cell Line; D005260:Female; D005822:Genetic Vectors; D019746:Intramolecular Oxidoreductases / Q000235:genetics* / Q000276:immunology; D008089:Listeria monocytogenes / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D008546:Melanoma, Experimental / Q000628:therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014614:Vaccines, Synthetic / Q000627:therapeutic use*; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D019496:Cancer Vaccines; D014614:Vaccines, Synthetic; D019746:Intramolecular Oxidoreductases; C042501:dopachrome isomerase