title: Francisella tularensis Live Vaccine Strain deficient in capB and overexpressing the fusion protein of IglA, IglB, and IglC from the bfr promoter induces improved protection against F. tularensis respiratory challenge.
abstract: A safer and more effective vaccine than the unlicensed Francisella tularensis Live Vaccine Strain (LVS) is needed to protect against the biowarfare agent F. tularensis. Previously, we developed an LVS ΔcapB mutant that is significantly safer than LVS and provides potent protective immunity against F. tularensis respiratory challenge when administered intranasally but limited protection when administered intradermally unless as part of a prime-boost vaccination strategy. To improve the immunogenicity and efficacy of LVS ΔcapB, we developed recombinant LVS ΔcapB (rLVS ΔcapB) strains overexpressing various F. tularensis Francisella Pathogenicity Island (FPI) proteins - IglA, IglB and IglC, and a fusion protein (IglABC) comprising immunodominant epitopes of IglA, IglB, and IglC downstream of different Francisella promoters, including the bacterioferritin (bfr) promoter. We show that rLVS ΔcapB/bfr-iglA, iglB, iglC, and iglABC express more IglA, IglB, IglC or IglABC than parental LVS ΔcapB in broth and in human macrophages, and stably express FPI proteins in macrophages and mice absent antibiotic selection. In response to IglC and heat-inactivated LVS, spleen cells from mice immunized intradermally with rLVS ΔcapB/bfr-iglC or bfr-iglABC secrete greater amounts of interferon-gamma and/or interleukin-17 than those from mice immunized with LVS ΔcapB, comparable to those from LVS-immunized mice. Mice immunized with rLVS ΔcapB/bfr-iglA, iglB, iglC or iglABC produce serum antibodies at levels similar to LVS-immunized mice. Mice immunized intradermally with rLVS ΔcapB/bfr-iglABC and challenged intranasally with virulent F. tularensis Schu S4 survive longer than sham- and LVS ΔcapB-immunized mice. Mice immunized intranasally with rLVS ΔcapB/bfr-iglABC - but not with LVS - just before or after respiratory challenge with F. tularensis Schu S4 are partially protected; protection is correlated with induction of a strong innate immune response. Thus, rLVS ΔcapB/bfr-iglABC shows improved immunogenicity and protective efficacy compared with parental LVS ΔcapB and, in contrast to LVS, has partial efficacy as immediate pre- and post-exposure prophylaxis.
authors: Division of Infectious Diseases, Department of Medicine, 37-121 Center for Health Sciences, School of Medicine, University of California - Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90095-1688, United States. Electronic address: QJia@mednet.ucla.edu.
authors: Qingmei
authors: Q
authors: Jia
authors: Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, United States. Electronic address: rbowen@rams.colostate.edu.
authors: Richard
authors: R
authors: Bowen
authors: Division of Infectious Diseases, Department of Medicine, 37-121 Center for Health Sciences, School of Medicine, University of California - Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90095-1688, United States. Electronic address: BaLee@mednet.ucla.edu.
authors: Bai-Yu
authors: BY
authors: Lee
authors: Division of Infectious Diseases, Department of Medicine, 37-121 Center for Health Sciences, School of Medicine, University of California - Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90095-1688, United States. Electronic address: BDillon@mednet.ucla.edu.
authors: Barbara Jane
authors: BJ
authors: Dillon
authors: Division of Infectious Diseases, Department of Medicine, 37-121 Center for Health Sciences, School of Medicine, University of California - Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90095-1688, United States. Electronic address: SGalic@mednet.ucla.edu.
authors: Saša
authors: S
authors: Masleša-Galić
authors: Division of Infectious Diseases, Department of Medicine, 37-121 Center for Health Sciences, School of Medicine, University of California - Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90095-1688, United States. Electronic address: MHorwitz@mednet.ucla.edu.
authors: Marcus A
authors: MA
authors: Horwitz
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D001428:Bacterial Vaccines / Q000276:immunology*; D003573:Cytochrome b Group / Q000235:genetics; D005260:Female; D005293:Ferritins / Q000235:genetics; D005604:Francisella tularensis / Q000235:genetics; D044404:Genomic Islands / Q000276:immunology; D006801:Humans; D000071497:Immunogenicity, Vaccine; D007371:Interferon-gamma / Q000276:immunology; D020381:Interleukin-17 / Q000276:immunology; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D056990:Post-Exposure Prophylaxis; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000276:immunology; D017384:Sequence Deletion; D000074084:THP-1 Cells; D014406:Tularemia / Q000517:prevention & control*; D000069376:Type VI Secretion Systems / Q000235:genetics / Q000276:immunology*; D014613:Vaccines, Attenuated / Q000276:immunology; D014614:Vaccines, Synthetic / Q000276:immunology
chemical_list: D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D003573:Cytochrome b Group; D020381:Interleukin-17; D011993:Recombinant Fusion Proteins; D000069376:Type VI Secretion Systems; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic; D007371:Interferon-gamma; D005293:Ferritins; C018032:bacterioferritin
keywords: Bioterrorism; Francisella pathogenicity island; Francisella tularensis; LVS ΔcapB; Type VI secretion system; Vaccine