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*
Department of Microbiology, Center for Immunology, University of Minnesota Medical School, Minneapolis, MN 55455; and
Department of Laboratory Medicine and Microbiology, University of Washington, Seattle, WA 98195
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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S. typhi does not cause systemic disease in mammalian hosts other than humans. This is probably due to a requirement for specific interactions with the human cystic fibrosis transmembrane conductance regulator for penetration of the gut epithelium and subsequent visceral infection to occur (2). However, a murine model of human typhoid is provided by infection of susceptible mice with S. typhimurium, which causes a lethal, systemic disease. After gaining entry to the host, Salmonella infect macrophages and persist in an intracellular vacuole by preventing phago-lysosomal fusion (3) and delaying vacuole acidification (4).
As with other intracellular micro-organisms, such as
Leishmania and Mycobacteria, there is an absolute
requirement for Th1-like CD4+ T cells to produce
or induce macrophage-activating cytokines such as IFN-
and TNF-
to resolve infection (5, 6). Thus, mice lacking class-II
restricted CD4+ T cells succumb to infection with
attenuated Salmonella, whereas mice lacking class-I
restricted T cells or 
T cells resolve infection (7, 8). Further evidence that cellular immunity is required for the
resolution of a primary Salmonella infection is demonstrated
by experiments using IFN-R knockout mice (8) or mice
treated with neutralizing Abs to IL-12 (9), neither of
which are able to resolve infection with an attenuated strain. A
similar requirement for cellular immunity has been observed in humans
with certain genetic or acquired cellular immunodeficiencies that
confer an increased susceptibility to Salmonella infection
(10, 11).
It has long been known in the murine model that protective immunity can be conferred by immunization with attenuated bacteria (12). Thus, susceptible strains of mice that resolve infection with an attenuated strain develop specific immunity, allowing resistance to secondary challenge with a virulent strain. However, it is not known which Ags are responsible for inducing such resistance, and there have been few reports of successful immunization of susceptible mice with purified Salmonella proteins. The best characterized of these are the Salmonella porins, which have been shown to protect susceptible mice against challenge with virulent Salmonella (13). A number of other bacterial extracts have been shown to be effective in protecting against Salmonella infection, but the identity of the immunizing Ag was not determined (14, 15). In addition, limited attempts at transferring immunity with Salmonella-specific T cell lines have failed to identify the specificity of the response (16, 17).
In this paper we report the characterization of a CD4+ T cell response induced by attenuated Salmonella in C57BL/6 mice. We demonstrate that a significant fraction of CD4+ T cells respond to the flagellar protein, FliC, in vivo during vaccination with an attenuated strain, and that responses to FliC are sufficient to protect against infection with a virulent strain. We also identified a stimulating epitope within a constant region of FliC as well as the TCRs that recognize this epitope. Finally, we demonstrated that responses to this peptide arise in vivo only upon secondary infection with Salmonella.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Female C57BL/6 (H-2b), BALB/c (H-2d) mice were purchased from the National Cancer Institute (Frederick, MD) and used at 8–16 wk of age for immunization experiments and for preparing APC populations.
Bacterial strains, infection, and Ag preparation
Mice were infected with Salmonella as previously
described (18). Bacterial strains (Table I
) were grown overnight in Luria-Bertoni
medium and diluted in PBS after estimating bacterial concentration
using a spectrophotometer. Immediately before oral infection by gavage,
mice were given a 5% sodium bicarbonate solution to neutralize stomach
acids, thus promoting infection. The effective dose of bacteria given
to the mice was verified by plating out dilutions of the bacterial
solution on MacConkey agar plates. In all experiments the estimated
bacterial concentration differed from the actual concentration by
<3-fold (data not shown). Heat-killed S. typhimurium
(HKST)3
(3) was prepared from an overnight culture of SL1344 that
was washed twice in PBS before incubation at 65°C for 1 h. Other
heat-killed Salmonella or Shigella were prepared
in a similar manner, and each strain was assessed for motility in soft
agar to confirm flagella expression before the preparation of
heat-killed bacteria. FliC was prepared from phase-fixed bacterial
strains BC115 and BC116 using both shearing and differential
centrifugation as previously described (19, 20). FliC was
further purified using a Sephadex G-200 column, collecting fractions
that contained a single band of the relevant m.w. on Coomassie-stained
SDS-PAGE gels. These FliC fractions were concentrated and pooled before
the presence of FliC in these preparations was confirmed by Western
blotting using an mAb specific for FliC (Biogenesis, Sandown, NH) that
detected a single band coincident with the band detected by Coomassie
staining. FliC was the only protein detected by silver staining (data
not shown).
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ELISPOT
The frequency of Salmonella-specific and
FliC-specific IFN--producing T cells was determined by the ELISPOT
assay (21). C57BL/6 mice were infected orally with 1
x 109 SL3261, and CD4+ T
cells were purified by positive selection from infected or uninfected
spleens. Spleen cells were incubated on ice with FITC-conjugated
anti-CD4 (PharMingen, San Diego, CA) followed by anti-FITC
microbeads (Miltenyi Biotech, Auburn, CA) before selection using a
magnetic cell sorter according to the manufacturer’s instructions.
After this procedure samples were routinely 97–99%
CD4+ cells, as assessed by flow cytometry after
two serial passages through the columns. Purified
CD4+ cells (5 x
106/well) were added to 24-well tissue culture
plates containing 5 x 106 irradiated
syngeneic splenocytes as APC. These wells then were supplemented with
medium alone, HKST (5 x 107/ml), purified
FliC (100 µg/ml), or peptide (10 µM) and incubated for 48 h at
37°C (these concentrations were determined to be optimal for IFN-
production). Live cells were recovered using Histopaque (density,
1.083; Sigma, St. Louis, MO) and added in serial dilutions to 96-well
microtiter plates (Millipore, Bedford, MA) that had been coated with
purified anti-IFN- (PharMingen). After 20 h, cells were
removed, and spots were visualized using biotinylated anti-IFN-
(PharMingen) and avidin peroxidase (Sigma) in conjunction with
3-amino-9-ethylcarbazole substrate (Sigma). Spots were counted under a
dissecting microscope and then recounted by an investigator who was
unaware of the experimental protocol to confirm accurate counting.
Immunization and Ab measurement
Mice were immunized twice, s.c. in the flanks with 200 µg of FliC or OVA mixed 1/1 with CFA, at 2-wk intervals. One week after the second dose, blood was obtained from the retro-orbital plexus, and serum was prepared. The Ab to FliC and OVA was measured using an ELISA method as previously described (18). Briefly, Ag was coated on 96-well microtiter plates (Costar, Cambridge, MA), and serum was added to plates in serial dilutions. After washing, bound Ab was detected using goat anti-mouse IgG1 and IgG2a HRP-conjugated Abs (Southern Biotechnology Associates, Birmingham, AL).
Generation of T cell lines and clones
T cell lines were prepared as previously described (22). Briefly, a single cell suspension of spleen cells from FliC-immunized or orally infected mice was cultured with HKST for 4 days. Live cells recovered from this culture were rested for an additional 10 days in the absence of Ag before a further round of restimulation with Ag and APC. Clones were derived from the line by limiting dilution in 96-well plates after stimulation with HKST and the addition of recombinant human IL-2 (Roche, Indianapolis, IN). Clones from 96-well plates that had <30% positive wells were expanded in 24-well plates before being assessed for reactivity to HKST. Clones were maintained by repeated cycles of stimulation with HKST followed by expansion with rIL-2 and at least 1 wk of rest before further restimulation.
Proliferation assays
T cells (1 x 104/well) were added to 96-well plates containing 5 x 105 irradiated APC and serial dilutions of HKST, purified FliC, or heat-killed Escherichia coli expressing pMal-FliC. After 2 days of stimulation, 1 µCi of [3H]thymidine was added to each well, and incorporated thymidine was measured the following day using liquid scintillation spectrophotometry.
Construction and characterization of pMal-FliC and derivatives
The construction of these strains has been described in detail
previously (23). Briefly, fliC from SL1344
chromosomal DNA was amplified by PCR using standard techniques and
ligated into the vector pMIE1. This construct, which encodes a 90-kDa
MalE-FliC fusion protein, was digested sequentially by exonuclease III
and S1 nuclease to make nested deletions in fliC from the 3'
end. The PCR products from these constructs were examined for the
extent of deletion and were ordered by size. E. coli
DH5-containing plasmids were grown to mid-log phase in Luria-Bertoni
broth and induced for 3–4 h with 500 µM isopropyl
-D-thiogalactoside (IPTG) before being washed
and killed at 65°C. We define regions of S. typhimurium
FliC by sequence homology as described previously (24),
numbering from the N-terminal alanine of the mature polypeptide
translated from the corrected sequence for fliC (GenBank
accession no. D13689): regions I (aa 1–100), II (aa 101–160), III (aa
161–179), IV (aa 180–300), V (aa 301–323), VI (324–360), VII (aa
361–421), and VIII (aa 422–494).
Flow cytometry
T cell lines, clones, or freshly isolated spleen cells (1
x 106) were incubated on ice for 15 min with
blocking solution (anti-Fc receptor supernatant from 24G2; 2% rat
serum, 2% mouse serum, and 0.01% sodium azide) before staining with
the following Abs; PE-conjugated anti-V2, -3, -4, -5.1/5.2, -6,
-7, -8.1/8.2, -8.3, -10, -11, and –13; biotin-conjugated
anti-V9, -12, and –14; FITC-conjugated V2, -3.2, -8, and
-11.1; NK1.1; or CD4. Streptavidin-PE was used as a detecting agent for
biotin-labeled Abs. After staining, cells were washed and analyzed
using a FACScan (Becton Dickinson, Mountain View, CA).
The TCR sequencing
Sequencing of TCR variable regions was accomplished using the
method of Candiasis et al. (25). Briefly, VDJ or
VJ regions were amplified by nested RT-PCR from each T cell clone
using degenerate primers. These DNA fragments were gel purified and
cloned into the pGem-3Z vector (Promega, Madison, WI). The inserted DNA
was sequenced using M13 primers (Promega), upstream and downstream of
the insert site.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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It is clearly established that CD4+ T cells
are critical for the resolution of Salmonella infection
(7, 8). However, the Ags recognized by T cells during
infection are largely unknown. As a first step in this direction, we
estimated the frequency of IFN- producing,
Salmonella-specific CD4+ T cells
during infection using an ELISPOT assay. These experiments demonstrated
that Salmonella-specific IFN- producing
CD4+ T cells can be detected in the spleen as
early as 1 wk after oral infection, although the frequency of
responding cells is low at this time point (Fig. 1). Salmonella-specific
CD4+ T cells increased in number from
4,000/spleen at 1 wk postinfection to 60,000/spleen at 4 wk (Fig. 1A). At 4 wk postinfection this number accounted for
0.2% of all CD4+ T cells in the spleen (Fig. 1B). In uninfected mice, the frequency of
Salmonella-specific CD4+ T cells was
below the limit of detection in this assay (estimated at 1,000
cells/spleen, data not shown).
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-producing CD4+ T cells
responding to FliC in Salmonella-infected C57BL/6 mice (Fig. 1
). A large fraction of Salmonella-specific,
CD4+ T cells responded to FliC at both 2 and 4 wk
postinfection, indicating that FliC is a major target for the immune
response during primary infection with SL3261. However, T cells
specific for unknown Ags, other than FliC, are clearly responding to
Salmonella, especially during the first 2 wk of
infection.
Similarly, after secondary challenge with SL3261, a large fraction of
Salmonella-specific IFN--producing
CD4+ T cells recognized FliC (Fig. 1C). One week after i.v. challenge with the attenuated
strain 0.15% of CD4+ T cells responded to
both FliC and HKST in this assay, indicating that there were 45,000
cells/spleen with FliC specificity. Thus, FliC-specific T cells also
account for a large fraction of all IFN--producing,
Salmonella-specific CD4+ T cells
during a secondary response.
Purified FliC can protect mice against lethal challenge
Because the magnitude of the CD4+ T cell
response to FliC was large in infected mice, it was possible that the
response to FliC would be sufficient to protect mice against challenge
with the virulent strain, SL1344. It has been reported that protection
of mice against S. typhimurium requires the transfer of both
immune T cells and immune serum (26). We therefore
immunized mice with purified FliC or OVA and first confirmed that
FliC-immunized mice make serum Ab responses to HKST (data not shown).
Furthermore, challenge with a lethal dose of the virulent strain,
SL1344, demonstrated that mice immunized with FliC were protected from
infection with virulent Salmonella, although the degree of
protection was less than that provided by the live vaccine strain (Fig. 2). Thus, immune responses to FliC alone
can protect against Salmonella infection, although responses
to other Ags may be required for optimal protection.
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To further analyze CD4+ T cell responses to
Salmonella typhimurium in vaccinated mice, we generated a
CD4+ T cell line from C57BL/6 mice that had
resolved an infection with the attenuated strain, SL3261. After three
rounds of stimulation with HKST in vitro, the line was responsive to
HKST presented by APC expressing H-2b but not
H-2d MHC molecules (Fig. 3A). As shown in Fig. 3B, this line was also stimulated by purified FliC presented
by syngeneic spleen cells. The specificity of this FliC response was
confirmed by generating an OVA-specific CD4+
T cell line from OVA-immunized C57BL/6 mice that responded to OVA
presented by I-Ab, but did not proliferate in
response to the FliC preparation (data not shown). Flow cytometric
analysis confirmed that cells in the line expressed CD4 (data not
shown), and because B6 mice lack the I-E class II molecule, the FliC
peptides responsible for stimulating the line must therefore be
presented in the context of I-Ab. To identify the
epitopes recognized by FliC-reactive CD4+ T cells
within this line we generated a series of truncated MalE-FliC fusion
proteins expressed in E. coli, as previously described
(23). This analysis showed that only a single region of
FliC, close to the carboxyl terminus, was recognized (Fig. 3C).
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The line described above was cloned by limiting dilution, and all
clones were tested for responsiveness to both HKST and FliC. All
clones (26 in total) that responded to HKST also responded to FliC
in vitro. The responses of four representative clones are shown in Fig. 3, D and E. These clones were further tested for
responsiveness to the same truncated FliC fusion proteins described
above. As expected from the limited mapping of the line (Fig. 3C), all clones responded to the same C-terminal region of
FliC (data not shown).
The FliC protein sequence has been divided into eight regions based on
homology between Salmonella serovars (24). The
initial epitope mapping indicated that the T cells recognized either
region VII or VIII, both of which have relatively conserved amino acid
sequences between serovars (75 and 100% homology for regions VII and
VIII, respectively). Thus, it was possible that these clones might
recognize FliC proteins from other distinct Salmonella
serovars due to the sharing of a conserved epitope. Indeed, consistent
with a constant region epitope, we found that these clones responded to
a conserved epitope in FliC produced by S. paratyphi, S.
gaminara, S. typhimurium (Fig. 4A), and S.
cholerasuis (data not shown), but that is not present in S.
enteritidis (Fig. 4A) or Shigella sonnei
(data not shown).
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B, the clones still responded to
these bacteria in the absence of FliC, although the response was weaker
than that to FliC-expressing bacteria. Together these data indicate that this FliC epitope recognized by a CD4+ T cell from naturally infected C57BL/6 mice is located in a region common to a number of distinct Salmonella serovars and is present in both phase variants.
The dominant epitope is contained within the constant C-terminus of FliC
We constructed additional truncated FliC fusion proteins that
overlap the region thought to contain the stimulatory epitope
recognized by our T cell clones. The genes encoding MalE-FliC
truncations closest to the epitope, indicated by loss of responsiveness
in the stimulation assays, were then subjected to DNA sequence
analysis. All T cell clones tested responded in a similar fashion to
the representative clone CN.B1 shown in Fig. 5. These data suggest that the terminal
NLG at positions 437–39 are critical to maintain responsiveness. We
therefore synthesized four overlapping 15-mer peptides around this
region and used these to stimulate the clones. As shown in Fig. 6, both peptides 427–441 and 425–439
were able to stimulate the clones; 427–441 was more efficient. This
epitope, as predicted from the extensive cross-reactivity in the
proliferation experiments described above, is found within constant
region VIII, which has almost 100% homology between
Salmonella serovars and between FliC and FljB (Table II). Indeed, there is extensive homology
between this region of FliC and the flagellar sequence of other
bacteria, such as Shigella sonnei and E. coli,
further emphasizing the conserved nature of this epitope. As all
nonresponding bacteria tested to date have an N to D substitution at
position 433 (Table II), this may indicate a contact residue for either
MHC or TCR molecules.
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2/V10+, and NK1.1-
To assess heterogeneity among the FliC-specific clones from
infected mice we stained each clone for the TCR variable region using
mAbs. We initially screened with a panel of V- and V-specific
mAbs specific for 15 V-chains and four V-chains. All clones
were found to be both CD4+ and
V2+ and did not stain with any other
-chain-specific Ab or any of the four V Abs tested (data not
shown). It was recently reported that infection of beige mice with
Salmonella induces a population of IL-4-secreting
NK1.1+ T cells (28), and that a
class II-dependent NK1.1+ cell population
is induced after peritoneal infection with Salmonella
(29). Since the majority of CD4+
NK1.1+ T cells express a limited range of TCR
V-chains including V2, we stained all clones with an Ab against
NK1.1 to rule out the possibility that we had cloned an NK-T cell.
However, none of the clones stained positively for NK1.1, while the Ab
was able to detect an NK1.1+ population in the
spleen of uninfected B6 mice (data not shown).
As none of the anti-V Abs stained the clones, we had no
information regarding V usage. Therefore, we determined the TCR
usage of four representative FliC-specific clones by RT-PCR using
degenerate primers to amplify the VDJ region of the -chain or the VJ
region of the rearranged -chain (25). As shown in Table III all four clones contained in-frame
transcripts for V2 and V10 with identical junctional regions,
indicating that these four clones were derived from a single
FliC-specific CD4+ T cell. It was therefore
possible that despite cloning the T cell line after only three rounds
of stimulation in vitro, the T cell line was composed mainly of a
single dominant clone. We therefore generated a second T cell line from
mice immunized s.c. with FliC/CFA and again made a number of T cell
clones. These were assessed in a stimulation assay using truncated FliC
fusion proteins as described above. In summary, all of these clones (10
of 10) responded to the FliC427–441 epitope
described above (data not shown). In addition, we sequenced the TCR
and variable regions from two of these clones, and these data
indicate a more heterogeneous TCR usage (Table III). Together these
data suggested that the FliC epitope 427–441 is an epitope recognized
by T cell clones derived from C57BL/6 mice regardless of initial
priming conditions in the mouse.
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To determine the proportion of FliC-specific
CD4+ T cells that respond to epitope 427–441 in
vivo, we used the ELISPOT technique to measure the frequency of
IFN--producing CD4+ T cells from
Salmonella-infected mice after in vitro restimulation with
peptide. Surprisingly, we were unable to detect a response to this
epitope at any stage of a primary infection (data not shown). However,
upon secondary challenge with SL3261, responses to this peptide were
clearly detected, accounting for approximately one-third of all
FliC-specific IFN--producing cells (Fig. 1C).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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FliC was initially identified as a target for CD4+ T cells from experiments with S. typhimurium-infected C3H mice (23). There is also evidence from infection of human volunteers with attenuated S. typhi that FliC is probably a major target of the cellular immune response, as T cells from these infected patients proliferated in response to flagellar extracts in vitro (30). In this report we extend these studies and demonstrate with a quantitative ELISPOT assay that FliC is a major target for CD4+ T cell responses during natural infection of C57BL/6 mice with attenuated S. typhimurium.
Why does FliC elicit such a strong response? It has been reported that despite a requirement for flagellar expression for motility, FliC is not a virulence factor, i.e., nonmotile Salmonella lacking FliC are just as virulent in vivo as motile FliC-expressing strains (31). Therefore, the immune system does not specifically target Salmonella proteins required for growth in the host. However, other factors, such as the amount and physical localization of FliC on the bacterial surface and the biochemical process of self assembly that occurs at the tip of the filament, may mean that there is an abundance of soluble FliC secreted into the surrounding environment. Thus, it may be one of the first Ags to which dendritic cells have access when they encounter Salmonella during the early stages of infection.
The very nature of FliC as an Ag may also encourage an immune response.
Flagellar proteins from Salmonella have long been the
subject of study by immunologists due to their immunogenic properties
and the capacity for polymerization and depolymerization of the
filament (32). In addition, a recent report has described
the production of TNF- from a human promonocytic cell line in
response to FliC (33), suggesting that there may be an
inherent adjuvant effect attributable to FliC itself. Any or all of
these factors might contribute to the selection of FliC as a target for
CD4+ T cell responses during infection with
S. typhimurium.
The identification of FliC as an Ag involved in the primary CD4+ T cell response after infection with a vaccine strain of Salmonella and the capacity of this response to provide protection from a virulent organism may aid in the development of subunit and live attenuated Salmonella vaccines. Expression of heterologous epitopes within the FliC molecule itself has already been shown to be an effective strategy to induce immune responses to heterologous proteins (34). The factors discussed above that may be responsible for a CD4+ response to FliC might similarly enhance responses to these inserted epitopes.
The conserved nature of the I-Ab binding peptide described here indicates that there may be a significant degree of cross-protective immunity between serovars after infection with Salmonella. Previous attempts to map T cell epitopes of S. muenchen in FliC-immunized BALB/c (H-2d) mice using overlapping synthetic peptides identified major epitopes within regions I and II, the conserved amino-terminal portion of the molecule (35). The FliC epitope identified from Salmonella-infected C3H/HeJ mice was located in hypervariable region VI in the middle of the protein. Thus, there is no clear pattern in recognition of FliC epitopes across MHC haplotypes.
Virtually all the T cell clones that we have isolated from infected mice are specific for the 427–441 peptide. Thus, it was surprising that 427–441-specific CD4+ T cells could not be detected by ELISPOT during the primary infection. It is possible that in vitro culture conditions favor clones responding to this epitope and that T cells responding to other undefined epitopes account for the majority of the natural primary response to FliC in vivo. However, T cells responding to peptide 427–441 account for a significant fraction of FliC-specific T cells during a secondary response. It may be that the presence of FliC-specific B cells during this secondary restimulation serves to change the nature of the peptides presented or the APC involved in stimulating FliC-specific CD4+ T cells. This possibility is currently under investigation in our laboratory.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Stephen J. McSorley, Department of Microbiology and Center for Immunology, University of Minnesota Medical School, Room 6-220, BSBE Building, 312 Church Street S.E., Minneapolis, MN 55455. E-mail address:
3 Abbreviations used in this paper: HKST, heat-killed Salmonella typhimurium; ELISPOT, enzyme-linked immunospot.
Received for publication August 24, 1999. Accepted for publication November 4, 1999.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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cells and IFN- in bacterial clearance independent of intracellular location. J. Immunol. 156:3321.[Abstract]
interferon and macrophage activation. Infect. Immun. 66:4767. T cells are induced in mice by Salmonella infection. J. Immunol. 162:1573. in a human promonocytic cell line. Infect. Immun. 66:1127.This article has been cited by other articles:
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  C. J. Sanders, D. A. Moore III, I. R. Williams, and A. T. Gewirtz Both Radioresistant and Hemopoietic Cells Promote Innate and Adaptive Immune Responses to Flagellin J. Immunol., June 1, 2008; 180(11): 7184 - 7192. [Abstract] [Full Text] [PDF]
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 J. C. Noujaim, R. L. A. Filho, E. T. Lima, A. S. Okamoto, R. L. Amorim, and R. T. Neto Detection of T Lymphocytes in Intestine of Broiler Chicks Treated with Lactobacillus spp. and Challenged with Salmonella enterica Serovar Enteritidis Poult. Sci., May 1, 2008; 87(5): 927 - 933. [Abstract] [Full Text] [PDF]
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 J. Benyacoub, F. Rochat, K.-Y. Saudan, I. Rochat, N. Antille, C. Cherbut, T. von der Weid, E. J. Schiffrin, and S. Blum Feeding a Diet Containing a Fructooligosaccharide Mix Can Enhance Salmonella Vaccine Efficacy in Mice J. Nutr., January 1, 2008; 138(1): 123 - 129. [Abstract] [Full Text] [PDF]
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 A. Berndt, A. Wilhelm, C. Jugert, J. Pieper, K. Sachse, and U. Methner Chicken Cecum Immune Response to Salmonella enterica Serovars of Different Levels of Invasiveness Infect. Immun., December 1, 2007; 75(12): 5993 - 6007. [Abstract] [Full Text] [PDF]
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R. C. Alaniz, B. L. Deatherage, J. C. Lara, and B. T. Cookson Membrane Vesicles Are Immunogenic Facsimiles of Salmonella typhimurium That Potently Activate Dendritic Cells, Prime B and T Cell Responses, and Stimulate Protective Immunity In Vivo J. Immunol., December 1, 2007; 179(11): 7692 - 7701. [Abstract] [Full Text] [PDF]
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R.-M. Salazar-Gonzalez, A. Srinivasan, A. Griffin, G. Muralimohan, J. M. Ertelt, R. Ravindran, A. T. Vella, and S. J. McSorley Salmonella Flagellin Induces Bystander Activation of Splenic Dendritic Cells and Hinders Bacterial Replication In Vivo J. Immunol., November 1, 2007; 179(9): 6169 - 6175. [Abstract] [Full Text] [PDF]
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C. Adriaensen, H. De Greve, J. Q. Tian, S. De Craeye, E. Gubbels, V. Eeckhaut, F. Van Immerseel, R. Ducatelle, M. Kumar, and J.-P. Hernalsteens A Live Salmonella enterica Serovar Enteritidis Vaccine Allows Serological Differentiation between Vaccinated and Infected Animals Infect. Immun., May 1, 2007; 75(5): 2461 - 2468. [Abstract] [Full Text] [PDF]
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 A. Srinivasan and S. J. McSorley Exposure to LPS suppresses CD4+ T cell cytokine production in Salmonella-infected mice and exacerbates murine typhoid J. Leukoc. Biol., February 1, 2007; 81(2): 403 - 411. [Abstract] [Full Text] [PDF]
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R. C. Alaniz, L. A. Cummings, M. A. Bergman, S. L. Rassoulian-Barrett, and B. T. Cookson Salmonella typhimurium Coordinately Regulates FliC Location and Reduces Dendritic Cell Activation and Antigen Presentation to CD4+ T cells J. Immunol., September 15, 2006; 177(6): 3983 - 3993. [Abstract] [Full Text] [PDF]
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C. J. Sanders, Y. Yu, D. A. Moore III, I. R. Williams, and A. T. Gewirtz Humoral immune response to flagellin requires T cells and activation of innate immunity. J. Immunol., September 1, 2006; 177(5): 2810 - 2818. [Abstract] [Full Text] [PDF]
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J. R. Maxwell, R. Yadav, R. J. Rossi, C. E. Ruby, A. D. Weinberg, H. L. Aguila, and A. T. Vella IL-18 Bridges Innate and Adaptive Immunity through IFN-{gamma} and the CD134 Pathway J. Immunol., July 1, 2006; 177(1): 234 - 245. [Abstract] [Full Text] [PDF]
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J. Caron, L. Lariviere, M. Nacache, M. Tam, M. M. Stevenson, C. McKerly, P. Gros, and D. Malo Influence of Slc11a1 on the Outcome of Salmonella enterica Serovar Enteritidis Infection in Mice Is Associated with Th Polarization. Infect. Immun., May 1, 2006; 74(5): 2787 - 2802. [Abstract] [Full Text] [PDF]
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S. Ugrinovic, C. G. Brooks, J. Robson, B. A. Blacklaws, C. E. Hormaeche, and J. H. Robinson H2-M3 Major Histocompatibility Complex Class Ib-Restricted CD8 T Cells Induced by Salmonella enterica Serovar Typhimurium Infection Recognize Proteins Released by Salmonella Serovar Typhimurium Infect. Immun., December 1, 2005; 73(12): 8002 - 8008. [Abstract] [Full Text] [PDF]
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M. A. Bergman, L. A. Cummings, R. C. Alaniz, L. Mayeda, I. Fellnerova, and B. T. Cookson CD4+-T-Cell Responses Generated during Murine Salmonella enterica Serovar Typhimurium Infection Are Directed towards Multiple Epitopes within the Natural Antigen FliC Infect. Immun., November 1, 2005; 73(11): 7226 - 7235. [Abstract] [Full Text] [PDF]
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R. Ravindran, J. Foley, T. Stoklasek, L. H. Glimcher, and S. J. McSorley Expression of T-bet by CD4 T Cells Is Essential for Resistance to Salmonella Infection J. Immunol., October 1, 2005; 175(7): 4603 - 4610. [Abstract] [Full Text] [PDF]
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R. Rosales-Reyes, C. Alpuche-Aranda, M. d. l. L. Ramirez-Aguilar, A. D. Castro-Eguiluz, and V. Ortiz-Navarrete Survival of Salmonella enterica Serovar Typhimurium within Late Endosomal-Lysosomal Compartments of B Lymphocytes Is Associated with the Inability To Use the Vacuolar Alternative Major Histocompatibility Complex Class I Antigen-Processing Pathway Infect. Immun., July 1, 2005; 73(7): 3937 - 3944. [Abstract] [Full Text] [PDF]
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L. A. Cummings, S. L. R. Barrett, W. D. Wilkerson, I. Fellnerova, and B. T. Cookson FliC-Specific CD4+ T Cell Responses Are Restricted by Bacterial Regulation of Antigen Expression J. Immunol., June 15, 2005; 174(12): 7929 - 7938. [Abstract] [Full Text] [PDF]
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