scholarly journals The C-Terminal Domain of Salmonella enterica Serovar Typhimurium OmpA Is an Immunodominant Antigen in Mice but Appears To Be Only Partially Exposed on the Bacterial Cell Surface

2003 ◽  
Vol 71 (7) ◽  
pp. 3937-3946 ◽  
Author(s):  
Shiva P. Singh ◽  
Yvonne U. Williams ◽  
Stephanie Miller ◽  
Hiroshi Nikaido
Keyword(s):  
Cell Surface ◽  
Outer Membrane ◽  
Bacterial Cell ◽  
Salmonella Enterica ◽  
Competitive Inhibition ◽  
Enzyme Linked Immunosorbent Assay ◽  
Intact Cells ◽  
Bacterial Cell Surface ◽  
Terminal Domain ◽  
Serovar Typhimurium

ABSTRACT We examined the way the major outer membrane protein OmpA of Salmonella enterica serovar Typhimurium is recognized by the mouse immune system, by raising a panel of 12 monoclonal antibodies (MAbs) against this protein. Interaction between OmpA and these MAbs is competitively inhibited with several-hundredfold dilutions of mouse polyclonal sera obtained by immunization with live or heat-killed whole cells, suggesting that OmpA is one of the immunodominant antigens of serovar Typhimurium. All of the MAbs were specific for an identical epitope(s) located on the C-terminal domain of OmpA, as indicated by the use of OmpA fragments generated by protease or cyanogen bromide treatment and by competitive inhibition enzyme-linked immunosorbent assay. This epitope was highly conserved within (but not outside) the family Enterobacteriaceae. The strong immunogenicity of this epitope was surprising because the C-terminal domain of OmpA, usually thought to be located in the periplasm, is not expected to be exposed on the bacterial cell surface. A MAb, however, reacted in a cytofluorometry assay more strongly with outer-membrane-permeabilized cells than with untreated cells, a result supporting the predominantly periplasmic localization of the epitope. Significant, though low-level, reactivity of intact cells nevertheless suggests that in some cells the C-terminal domain of OmpA is exposed on the surface, a result consistent with the proposal that OmpA can fold into one of the two alternate conformations.

scholarly journals Expression of the Plasmodium falciparum Immunodominant Epitope (NANP)4 on the Surface of Salmonella enterica Using the Autotransporter MisL

2002 ◽  
Vol 70 (7) ◽  
pp. 3611-3620 ◽  
Author(s):  
Fernando Ruiz-Pérez ◽  
Rocío León-Kempis ◽  
Araceli Santiago-Machuca ◽  
Guadalupe Ortega-Pierres ◽  
Eileen Barry ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Plasmodium Falciparum ◽  
Outer Membrane ◽  
Salmonella Enterica ◽  
Secretory Pathway ◽  
Cell Epitope ◽  
Bacterial Strains ◽  
Gram Negative ◽  
Terminal Domain ◽  
Serovar Typhimurium

ABSTRACT Gram-negative bacterial proteins which are exported from the cytosol to the external environment by the type V secretion system are also known as autotransporters. Once translocated to the periplasmic compartment by the sec-dependent general secretory pathway, their C-terminal domain forms a pore through which the N-terminal domain travels to the outer membrane without the need of other accessory proteins. MisL (protein of membrane insertion and secretion) is a protein of unknown function located in the pathogenicity island SPI-3 of Salmonella enterica and classified as an autotransporter due to its high homology to Escherichia coli AIDA-I. In the present work, the MisL C-terminal translocator domain was used to display the immunodominant B-cell epitope of the circumsporozoite protein (CSP) from Plasmodium falciparum on the surface of Salmonella enterica serovar Typhimurium (serovar Typhimurium SL3261) and serovar Typhi (serovar Typhi CVD 908). The MisL β domain was predicted by alignment with AIDA-I, amplified from serovar Typhimurium SL3261, cloned in a plasmid fused to four repeats of the tetrapeptide NANP behind the Escherichia coli heat-labile enterotoxin B subunit signal peptide to ensure periplasmic traffic, and expressed under the control of the anaerobically inducible nirB promoter. The fusion protein was translocated to the outer membrane of both bacterial strains, although the foreign epitope was displayed more efficiently in serovar Typhimurium SL3261, which elicited a better specific antibody response in BALB/c mice. More importantly, antibodies were able to recognize the native CSP in P. falciparum sporozoites. These results confirm that MisL is indeed an autotransporter and that it can be used to express foreign immunogenic epitopes on the surface of gram-negative bacteria.

scholarly journals Evidence for Active Efflux as the Primary Mechanism of Resistance to Ciprofloxacin in Salmonella enterica Serovar Typhimurium

2000 ◽  
Vol 44 (5) ◽  
pp. 1223-1228 ◽  
Author(s):  
Etienne Giraud ◽  
Axel Cloeckaert ◽  
Dominique Kerboeuf ◽  
Elisabeth Chaslus-Dancla
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Efflux Pump ◽  
Enzyme Linked Immunosorbent Assay ◽  
Topoisomerase Iv ◽  
Efflux Pump Inhibitor ◽  
Active Efflux ◽  
Fluorimetric Method ◽  
Serovar Typhimurium ◽  
Acrab Efflux Pump

ABSTRACT The occurrence of active efflux and cell wall modifications were studied in Salmonella enterica serovar Typhimurium mutants that were selected with enrofloxacin and whose phenotypes of resistance to fluoroquinolones could not be explained only by mutations in the genes coding for gyrase or topoisomerase IV. Mutant BN18/21 exhibited a decreased susceptibility to ciprofloxacin (MIC = 0.125 μg/ml) but did not have a mutation in the gyrA gene. Mutants BN18/41 and BN18/71 had the same substitution, Gly81Cys in GyrA, but exhibited different levels of resistance to ciprofloxacin (MICs = 2 and 8 μg/ml, respectively). None of the mutants had mutations in the parC gene. Evidence for active efflux was provided by a classical fluorimetric method, which revealed a three- to fourfold decrease in ciprofloxacin accumulation in the three mutants compared to that in the parent strain, which was annuled by addition of the efflux pump inhibitor carbonyl cyanide m-chlorophenylhydrazone. In mutant BN18/71, a second fluorimetric method also showed a 50% reduction in the level of accumulation of ethidium bromide, a known efflux pump substrate. Immunoblotting and enzyme-linked immunosorbent assay experiments with an anti-AcrA antibody revealed that the resistance phenotype was strongly correlated with the expression level of the AcrAB efflux pump and suggested that decreased susceptibility to ciprofloxacin due to active efflux probably related to overproduction of this pump could occur before that due to gyrA mutations. Alterations were also found in the outer membrane protein and lipopolysaccharide profiles of the mutants, and these alterations were possibly responsible for the decrease in the permeability of the outer membrane that was observed in the mutants and that could act synergistically with active efflux to decrease the level of ciprofloxacin accumulation.

scholarly journals Characterization of an Outer Membrane Protein of Salmonella enterica Serovar Typhimurium That Confers Protection against Typhoid

2008 ◽  
Vol 15 (9) ◽  
pp. 1461-1471 ◽  
Author(s):  
Nowsheen Hamid ◽  
S. K. Jain
Keyword(s):  
Molecular Mass ◽  
Outer Membrane ◽  
Salmonella Enterica ◽  
Outer Membrane Proteins ◽  
Lethal Dose ◽  
Health Concern ◽  
Delayed Type Hypersensitivity ◽  
Enzyme Linked Immunosorbent Assay ◽  
Protein Database ◽  
Serovar Typhimurium

ABSTRACT Typhoid caused by Salmonella enterica serovar Typhi remains a major health concern worldwide. The emergence of multidrug-resistant strains of Salmonella with increased virulence, communicability, and survivability leading to increased morbidity and mortality has further complicated its management. Currently available vaccines for typhoid have less-than-desired efficacy and certain unacceptable side effects, making it pertinent to search for new immunogens suitable for vaccine formulation. The outer membrane proteins (OMPs) of Salmonella have been considered possible candidates for conferring protection against typhoid. OMPs interface the cell with the environment, thus representing important virulence factors with a significant role in the pathobiology of gram-negative bacteria and bacterial adaptation. An OMP of Salmonella enterica serovar Typhimurium with an apparent molecular mass of 49 kDa that is highly immunogenic, evokes humoral and cell-mediated immune responses, and confers 100% protection to immunized rats against challenge with very high doses (up to 100 times the 50% lethal dose) of Salmonella enterica serovar Typhimurium has been identified. Further, very efficient clearance of bacteria from the reticuloendothelial systems of immunized animals was seen. This protein is recognized by the antibodies present in serum of typhoid patients. When sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel-eluted protein was further analyzed by high-performance liquid chromatography (HPLC) and two-dimensional electrophoresis, two polypeptides with the same molecular weight were resolved. These have different isoelectric points and gave two peaks with different retention times in reverse-phase HPLC. However, only one of the two bands interacted with patient serum. The immunogenicity studies (enzyme-linked immunosorbent assay and delayed-type hypersensitivity [DTH]) indicated that the immunoreactive protein evoked a strong immune response in rats. The N-terminal sequencing and analysis of the homology of this protein with sequences in the protein database of Salmonella resulted in a match with the N-terminal sequences of a protein in Salmonella enterica serovar Typhi (CT18 and Ty2 strains). The homology search further revealed it to be a hypothetical protein, whose gene had unidentified open reading frames in Salmonella serovar Typhi encoding 447 amino acid residues, corresponding to a molecular mass of 49 kDa. The nucleotide sequence of the encoding gene was deduced, and the gene was amplified by PCR using appropriate primers. An amplified 1.3-kb band was purified and sequenced to confirm its identity. These OMPs provide promising targets for the development of a candidate vaccine against typhoid.

scholarly journals Construction and Immunological Evaluation of Dual Cell Surface Display of HIV-1 Gag and Salmonella enterica Serovar Typhimurium FliC in Lactobacillus acidophilus for Vaccine Delivery

2012 ◽  
Vol 19 (9) ◽  
pp. 1374-1381 ◽  
Author(s):  
Akinobu Kajikawa ◽  
Lin Zhang ◽  
Julie Long ◽  
Shila Nordone ◽  
Laura Stoeker ◽  
...  
Keyword(s):  
Cell Surface ◽  
Immune Responses ◽  
Signal Peptide ◽  
Lactobacillus Acidophilus ◽  
Bacterial Cell ◽  
Salmonella Enterica ◽  
Oral Vaccines ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Hiv 1

ABSTRACTOral vaccines that elicit a mucosal immune response may be effective against human immunodeficiency virus type 1 (HIV-1) because its transmission occurs mainly at the mucosa. The aim of this study was to construct recombinantLactobacillusfor oral delivery of oral vaccines against HIV-1 and to evaluate their immunogenicity. A recombinantLactobacillus acidophilusstrain expressing the HIV-1 Gag on the bacterial cell surface was established by fusion with the signal peptide and anchor motif of a mucus binding protein (Mub) fromL. acidophiluswith or without coexpression ofSalmonella entericaserovar Typhimurium flagellin (FliC) fused to a different Mub signal peptide and anchor. Using HEK293 cells engineered to express Toll-like receptor 5 (TLR5), the biological activity of FliC on the bacterial cell surfaces was determined. The surface-exposed flagellin retained its TLR5-stimulating activity, suggesting that the recombinant strain with Gag and FliC dual display might provide a different immunopotency than the strain expressing only Gag. The immunological properties of the recombinant strains were assessed by coculture with human myeloid dendritic cells (DCs). The heterologous antigens on the cell surface affected maturation and cytokine responses of DCs. Acquired immune responses were also investigated by intragastric immunization of mice. The enzyme-linked immunosorbent spot assay showed induction of gamma interferon-producing cells at local mucosa after immunization of mice with the Gag-producing strain. Meanwhile, the immunization withL. acidophilusdisplaying both Gag and FliC resulted in an increase of Gag-specific IgA-secreting cells. These results suggested that the Gag-displayingL. acidophiluselicited specific immune responses and the coexistence of FliC conferred an adjuvant effect on local IgA production.

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