Abstract
The development of safe live, attenuated Salmonella vaccines may be facilitated by detoxification of its LPS. Recent characterization of the lipid A 1-phosphatase, LpxE, from Francisella tularensis allowed us to construct recombinant, plasmid-free strains of Salmonella that produce predominantly 1-dephosphorylated lipid A, similar to the adjuvant approved for human use. Complete lipid A 1-dephosphorylation was also confirmed under low pH, low Mg(2+) culture conditions, which induce lipid A modifications. LpxE expression in Salmonella reduced its virulence in mice by five orders of magnitude. Moreover, mice inoculated with these detoxified strains were protected against wild-type challenge. Candidate Salmonella vaccine strains synthesizing pneumococcal surface protein A (PspA) were also confirmed to possess nearly complete lipid A 1-dephosphorylation. After inoculation by the LpxE/PspA strains, mice produced robust levels of anti-PspA Abs and showed significantly improved survival against challenge with wild-type Streptococcus pneumoniae WU2 compared with vector-only-immunized mice, validating Salmonella synthesizing 1-dephosphorylated lipid A as an Ag-delivery system.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Adjuvants, Immunologic / biosynthesis*
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Adjuvants, Immunologic / metabolism
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Animals
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Cell Line
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Cell Line, Tumor
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Endotoxins / immunology
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Endotoxins / pharmacology*
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Female
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Humans
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Lipid A / analogs & derivatives*
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Lipid A / biosynthesis
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Lipid A / genetics
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Lipid A / metabolism
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Lipopolysaccharides / biosynthesis*
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Membrane Proteins / genetics*
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Membrane Proteins / metabolism
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Mice
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Mice, Inbred BALB C
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Phosphoric Monoester Hydrolases / genetics*
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Phosphoric Monoester Hydrolases / metabolism
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Phosphorylation / immunology
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Rabbits
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Salmonella Vaccines / genetics
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Salmonella Vaccines / immunology
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Salmonella Vaccines / metabolism
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Salmonella enterica / genetics
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Salmonella enterica / immunology
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Salmonella enterica / metabolism
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Salmonella typhimurium / genetics
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Salmonella typhimurium / immunology*
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Salmonella typhimurium / metabolism*
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Streptococcus pneumoniae / genetics
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Streptococcus pneumoniae / immunology
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Streptococcus pneumoniae / metabolism
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Vaccines, Attenuated / administration & dosage
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Vaccines, Attenuated / genetics
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Vaccines, Attenuated / immunology
Substances
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Adjuvants, Immunologic
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Endotoxins
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Lipid A
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Lipopolysaccharides
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Membrane Proteins
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Salmonella Vaccines
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Vaccines, Attenuated
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LpxE protein, Francisella tularensis
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Phosphoric Monoester Hydrolases
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monophosphoryl lipid A