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*
Laboratory of Host Defense and Germfree Life, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Nagoya, Japan;
Department of Periodontology, School of Dentistry, Aichi-Gakuin University, Chikusa-ku, Nagoya, Japan; and
GBF-German Research Center for Biotechnology, Braunschweig, Germany
| Abstract |
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in response to purified protein
derivative of M.tb. Administration of anti-IL-10 Ab
partly inhibited the suppressive effect of pretreatment with peptide
234252 on the development of AA. Furthermore, transfer of a T cell
line specific for the epitope at the time of AA induction markedly
suppressed AA. These findings suggested that T cells recognizing
peptide 234252 may play a regulatory role in inflammation during AA
via the production of suppressive cytokines including
IL-10. | Introduction |
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ß+ Th1-type T cells recognizing an
epitope of HSP65 have been reported to cause some types of autoimmune
diseases in rats and mice (3, 4, 5, 6). Adjuvant arthritis (AA)
is widely used as an experimental model for rheumatoid arthritis and
can be induced in Lewis rats by immunization with heat-killed
Mycobacterium tuberculosis (M.tb) suspended in
IFA (7, 8). The antigenic epitope recognized by an
arthritogenic T cell clone, which can induce AA, was identified as
residues 180188 of the mycobacterial HSP65 (3, 9, 10).
On the other hand, TCR
ß+ T cells recognizing
different epitopes of HSP65 were suggested to modulate autoimmune
diseases in rats. Pretreatment with 256270 epitope or 376408
epitope of mycobacterial HSP65 was reported to suppress AA (11, 12). Furthermore, transfer of T cell lines specific for 256265
epitope can prevent against AA induction (11). Beech et
al. (13) reported that pretreatment with mycobacterial
HSP65 protected against pristane-induced arthritis via induction of a
Th2-dominant response characterized by IL-4 production. Oral
administration of recombinant HSP65 was reported to suppress AA,
possibly by induction of Th3 cells capable of producing TGF-ß
(14). Thus, similarly to T cells recognizing conventional
Ags, HSP65-reactive T cells may be classified into several subsets in
terms of function, and the nature of the HSP65 epitope may be an
important factor to determine whether proliferating
CD4+ T cells will differentiate into each T cell
subset. In addition to HSP65, pretreatment with mycobacterial
recombinant HSP70 was also reported to suppress AA in rats. Kingston et
al. (15) demonstrated that s.c. injection of recombinant
HSP70 produced inhibitory effects on induction of arthritis by
M.tb. However, the mechanisms underlying the suppressive
effect and nature of Ag epitopes of HSP70 remain to be determined. We have previously reported that HSP70-reactive CD4+ T cells appeared in the peritoneal cavity during the course of Listeria monocytogenes infection in rats. The HSP70-reactive CD4+ T cells recognized a peptide comprising residues 234252 of HSP70 of M.tb in the context of RT1.B MHC class II molecules. The HSP70-reactive CD4+ T cells produced significant amounts of TGF-ß1 and IL-10 and suppressed host defense against listerial infection (16). We hypothesized that T cells recognizing the specific epitope of HSP70 may be involved in termination of Th1 cell-mediated excessive inflammation after the battle against L. monocytogenes has been won.
In the present study, we investigated the effects of pretreatment with peptide 234252 of HSP70 derived from M.tb on the development of AA, a Th1 cell-mediated autoimmune disease. Pretreatment with peptide 234252 of HSP70 protected against AA induction, and the T cells from rats pretreated with peptide 234252 produced significant amounts of IL-10 in response to the relevant epitope. Administration of a T cell line specific for the epitope at the time of AA induction suppressed AA. These findings may facilitate an insight into vaccine development for human arthritic diseases.
| Materials and Methods |
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Male Lewis rats were obtained from Charles River (Tokyo, Japan). The rats were 56 wk old at the start of each experiment.
Ags and adjuvant
M.tb strain H37Ra was obtained from Difco (Detroit, MI). Recombinant HSP70 derived from M.tb was kindly provided by GBF-German Research Center for Biotechnology (Braunschweig, Germany). IFA was used as an adjuvant (Difco). PPD (purified protein derivative of M.tb) was purchased from the Japan BCG Association (Tokyo, Japan). Two kinds of synthetic peptides of the HSP70 of M.tb were synthesized using a method of simultaneous multiple peptide synthesis (Kurabo, Osaka, Japan): peptide 84103 and 234252 representing the amino acid sequence 84103 and 234252, respectively, which are at comparable levels to the recombinant HSP derived from M.tb. These peptides encompass the residues, which can bind to mouse I-Ab molecules, as assessed by T Sites software (MedImmune, Gaithersburg, MD) (16).
Pretreatment with synthetic peptide and induction of adjuvant arthritis
Synthetic peptides were dissolved in PBS and mixed with an equal volume of IFA. The heat-killed M.tb were finely ground in a mortar and pestle and suspended in IFA at a concentration of 5 mg/ml. Rats were pretreated by inoculation of 100 µl of emulsions containing 1 mg/ml synthetic peptide into the base of the tail, and were immunized 7 days later by inoculation of 100 µl of M.tb/IFA into the base of the tail. Severity of arthritis was assessed by scoring each paw from 0 to 4 based on degree of swelling, erythema, and deformity of the joints. Thus, the maximum possible arthritis score was 16 (17).
Preparation of cells and cell culture
Lymph node cells (LNC) were derived as pooled inguinal and popliteal LN from rats pretreated with the peptide/IFA 7 days previously or on day 35 after M.tb/IFA immunization. The cells were passed over nylon fiber column and purified to >80% CD3+ cells, as assessed by FACS analysis. Triplicate cultures of the enriched T cells (2 x 106 cells/ml) were cultured with the same number of mitomycin (MMC)-treated normal syngeneic spleen cells as APC in the presence or absence of Ag in 96-well flat-bottom plates (Falcon, Becton Dickinson, Lincoln Park, NJ) for 72 h at 37°C in a humidified atmosphere of 5% CO2. RPMI 1640 complete culture medium contained 10% FBS (CSL, Victoria, Australia), 100 U/ml penicillin, 100 mg/ml streptomycin, and 10 mM HEPES. An optimal dose of each Ag for the maximal response was added to the culture as follows: 50 µg/ml each peptide and 25 µg/ml PPD. For the last 18 h, triplicate cultures of cells were pulse labeled with [3H]thymidine (1 µCi/well; Amersham Life Science, Amersham, U.K.) before harvesting on glass fiber filters. Incorporation of [3H]thymidine was determined with MicroBeta (Wallac, Turku, Finland).
In vivo administration of anti-IL-10 Ab
Rats were injected i.p. with 250 µg of anti-IL-10 Ab (Biosource, Camarillo, CA) or isotype control Ab (Zymed, South San Francisco, CA) three times every 3 days from the beginning of immunization with M.tb/IFA. Five rats per each group were used for the experiment.
T cell lines
RT1.B-restricted T cell line specific for peptide 234252 of
mycobacterial HSP70 was isolated from rats immunized with HSP70. T
cells were cultured at 5 x 106 cells/ml in
culture medium in the presence of 10 µg/ml peptide. After 3 days,
viable cells were harvested using a Ficoll-Isopaque gradient and
cultured for an additional 4 days in culture medium plus 5% FCS and
5% Con A-activated spleen supernatant. Seven days after initial
stimulation, cells were restimulated with irradiated spleen APC and 10
µg/ml peptide. Cell lines were maintained by restimulation every 7
days. Rats were administered 5 x 106 T
cells i.v. at the time of AA induction with M.tb/IFA. The T
cell line is of
CD4+TCR
ß+CD44high
phenotype and produced IL-10 in response to peptide 234252 or
recombinant HSP70. RT1.B-restricted T cell line specific for
heat-killed Listeria (HKL) was isolated from rats infected
with viable L. monocytogenes (16). The
HKL-specific T cell line is of
CD4+TCR
ß+CD44high
phenotype and produced IFN-
, but no IL-10 in response to
HKL.
Cytokine assays
Culture supernatants were harvested after 72-h incubation time.
IFN-
, IL-10, IL-4, and TGF-ß1 activities in the culture
supernatants were measured by ELISA using a rat IFN-
, IL-10, IL-4
ELISA kits (Bioscore International, Carmarillo, CA), and TGF-ß1 human
ELISA system (Amersham Life Science), respectively.
Flow-cytometric analysis
Flow-cytometric analysis was used to determine the phenotype of
T cells. Cells were stained with FITC-conjugated anti-CD8
mAb or
FITC-TCR
mAb or FITC-CD44, PE-conjugated anti-CD4 or
PE-conjugated anti TCR
ß mAb, and biotin-conjugated anti-CD3
mAb, followed by streptavidin-Red670 (Life Technologies, Gaithersburg,
MD). The stained cells were analyzed using a FACS flow cytometer
(Becton Dickinson, Oxnard, MA).
Statistical analysis
The statistical significance of arthritis score was determined by the generation of Kaplan-Meier cumulative hazard plots and Log-rank (Mantel-Cox) analysis. Other data were analyzed using an ANOVA model controlling for treatment, experiment, and the potential for an experiment by treatment interaction. p < 0.05 was taken as the level of significance. Analyses were completed using StatView 4.5 software (Abacus Concepts, Berkeley, CA) and Power Macintosh 7200 computers (Apple Computer, Cupertino, CA).
| Results |
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To determine whether pretreatment with peptide 234252 of
mycobacterial HSP70 has a protective effect against AA induction, we
examined the modulation of AA development by pretreatment with peptide
234252 in IFA (Fig. 1
B).
Rats were pretreated with 50 µg of recombinant HSP70, 100 µg of
83103 or 234252 peptide 7 days before induction with
M.tb/IFA. Consistent with previous findings
(15), pretreatment with whole recombinant HSP70 protected
against AA induction (mean maximum score = 3.3) (Fig. 1
A). Notably, pretreatment with peptide 234252
significantly suppressed the development of AA (mean maximum score
= 1.6) as compared with the PBS-pretreated group. (mean maximum
score = 14). Of the nine rats pretreated with peptide 234252,
four did develop clinical signs of arthritis, which were milder
than those seen in control rats (p < 0.01). No
significant differences in the onset or score of AA were observed in
rats pretreated with the control peptide 84103 (mean maximum
score = 15.3).
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To determine whether pretreatment of rats with a synthetic
peptide could prime for T cell reactivity to the epitope, we examined
the proliferative responses of the enriched LN T cells against peptide
234252 or PPD. The enriched T cells, which were prepared from rats on
day 7 after pretreatment with peptide 234252/IFA or PBS/IFA, were
used as responder cells, and peptide 234252 or PPD, and MMC-treated
normal syngeneic spleen cells were used as Ag and APC, respectively. As
shown in Fig. 2
A, the enriched
T cells from rats pretreated with peptide 234252 showed a significant
proliferative response to peptide 234252 and, to a lesser degree,
to PPD.
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levels were measured in culture
supernatants of the enriched T cells incubated with peptide 234252 or
PPD by ELISA. The enriched T cells from rats pretreated with peptide
234252 produced a large amount of IL-10 (Fig. 2
in response to peptide 234252 (Fig. 2
in response to PPD. These findings suggested that
pretreatment with the synthetic peptide primed a T cell response
producing IL-10 specific for the 234252 of HSP70. In vitro response of T cells from rats pretreated with peptide 234252 and immunized with M.tb/IFA
To determine whether T cells induced by the peptide 234256 are
activated after immunization with M.tb/IFA, we examined the
proliferative responses and cytokine production of the enriched LN T
cells from rats pretreated with the peptide/IFA and immunized with
M.tb/IFA against peptide 234252 or PPD. Rats were
pretreated with PBS/IFA or the peptide/IFA, and 7 days later, immunized
with M.tb/IFA. The enriched T cells, which were prepared
from rats on day 35 after immunization with M.tb/IFA, were
used as responder cells. As shown in Fig. 3
A, the enriched T cells from
rats pretreated with peptide 234252 showed a significant
proliferative response to peptide 234252, while those from the
control group pretreated with PBS showed limited blastogenesis in
response to the peptide. On the other hand, T cells from rats
pretreated with peptide 234252 appeared to proliferate less in
response to PPD than those from control rats.
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in response to
PPD, but no IL-10 was produced in response to peptide 234252. On the
other hand, the enriched T cells from rats pretreated with peptide
234252/IFA and challenged with M.tb/IFA produced a large
amount of IL-10, whereas little, if any, amount of IFN-
was
detectable in the culture supernatants in response to peptide 234252
or PPD. There were no differences in the production of TGF-ß1 among
the culture supernatants of these T cells, and IL-4 was not detected in
any culture supernatant (data not shown). These findings suggested that
the peptide-specific T cells producing IL-10, but few arthritogenic Th1
cells producing IFN-
, were activated in rats pretreated with the
peptide/IFA after immunization with M.tb/IFA. Effect of in vivo administration of anti-IL-10 Ab on the development of AA in rats pretreated with peptide 234252
Pretreatment with the epitope 234256 induced an epitope-specific
T cell response producing IL-10 and protected against AA. To determine
whether IL-10 is involved in the peptide-induced suppression of AA, we
examined the effect of in vivo administration of anti-IL-10 Ab on
suppression of AA induced by pretreatment with peptide 234252. As
shown in Fig. 4
, administration of
anti-IL-10 Ab from the beginning of AA induction partly inhibited,
but significantly, the suppression of AA in rats pretreated with the
peptide. None of the five rats pretreated with the peptide and given
control of IgG developed AA, whereas all of the five rats developed
clinical signs of arthritis when anti-IL-10 Ab was administered at
the beginning of AA induction. Administration of anti-IL-10 Ab at
the later stage after immunization with M.tb/IFA had no
effect on the peptide-induced suppression of AA development (data not
shown).
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To obtain direct evidence for the protective role of the
epitope-specific T cells in AA development, we used the
epitope-specific T cell line generated from HSP70-immunized rats and
the HKS-specific T cell line generated from
Listeria-infected rats. We confirmed that the
epitope-specific T cell line produced IL-10, but no IFN-
in
response to the peptide, and that the HKL-specific T cell line produced
IFN-
, but no IL-10 in response to HKL. Each of the two T cell lines
was administered i.v. to rats at the same time as M.tb/IFA
for AA induction. None of the five rats transferred with a T cell line
specific for epitope 234256 developed clinical signs of arthritis,
whereas administration of a Listeria-specific Th1 cell line
had no effect on AA (Fig. 5
).
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| Discussion |
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Th1 cells secrete IL-2, IFN-
, and TNF-ß for the induction of
cell-mediated immunity characterized by macrophage activation and CTL
induction (18, 19), and are responsible for the
pathogenesis of several types of autoimmune diseases including AA
(6). Th2 cells uniquely secrete IL-4 not only to induce Ab
production, but also to inhibit activities of macrophages and NK cells
by shutting down the cytokine synthesis of Th1 cells
(18, 19, 20, 21, 22). Recently, a unique subpopulation of Th cells
termed Th3 cells was reported to play an important role in immune
regulation, especially oral tolerance, through TGF-ß production
(23, 24, 25). Beech et al. (13) reported that
pretreatment with mycobacterial HSP65 protected against
pristane-induced arthritis in CBA/Ig mice via induction of
CD4+ Th2 cells specific for mycobacterial HSP65.
Haque et al. (14) reported that oral administration of
recombinant HSP65 suppressed AA possibly by induction of Th3 cells
producing TGF-ß. Therefore, it is possible that Th2 and/or Th3 cells
may be involved in protection against AA by pretreatment with HSP70.
The results of the present study indicated that
CD4+ T cells stimulated by pretreatment with
synthetic peptide 234252 produced IL-10, but not IL-4, in response to
the relevant Ag in Lewis rats. IL-10 has been reported to shut down the
cytokine synthesis of Th1 cells such as IFN-
(26, 27, 28).
In fact, T cells from rats pretreated with the synthetic peptide and
challenged with M.tb/IFA produced a lower amount of IFN-
in response to PPD as compared with controls pretreated with PBS/IFA.
It has been reported that daily i.p. injection of murine recombinant
rIL-10 caused mice to develop milder collagen-induced arthritis
(29). We reported previously that
CD4+ T cells specific for peptide 234252
emerged during the natural course of rat listeriosis and suppressed
host defense against listerial infection probably through production of
IL-10 and TGF-ß1 (16). Protection against infection with
intracellular parasites such as L. monocytogenes is
dependent on Th1 response capable of producing IFN-
(30). Therefore, T cells specific for peptide 234252 of
mycobacterial HSP70 may play a vital role in the down-regulation of
aggressive Th1 responses through IL-10 production.
Several mechanisms might explain the suppressive effect of
234252 peptide-primed T cells on the development of AA through IL-10
production. The first is that IL-10 produced by the peptide-specific T
cells may suppress the functions of arthritogenic Th1 cells at the
effector phase through shutting down IFN-
production. However, it is
unlikely because administration of anti-IL-10 Ab at the later stage
after immunization with M.tb/IFA had no effect on
suppression of AA development by pretreatment with peptide/IFA.
Furthermore, transfer of the peptide-specific T cells at the later
stage after immunization had no effect on the development of AA (data
not shown). The second is that IL-10 produced by the peptide-specific T
cells inhibits the generation of arthritogenic Th1 cells at the
induction stage after immunization with M.tb/IFA.
CD4+ T cells initially stimulated in the presence
of IL-12 and IFN-
tend to develop into CD4+
Th1 cells (31). IL-10 is known to exhibit a potent
suppressive effect on IL-12 production by dendritic cells and
macrophages, besides the suppressive effect on IFN-
production by NK
and T cells (32, 33). Therefore, a high level of IL-10
production at the initial phase of AA induction may inhibit the
generation of Th1 cells responsible for AA via suppression of IL-12 and
IFN-
production. Administration of anti-IL-10 Ab from the
beginning of immunization inhibited the suppression of AA induced by
pretreatment with the HSP70 peptide and transfer of the
peptide-specific T cell line at the same time AA induction inhibited
the AA development, supporting this mechanism. However, our results
with anti-IL-10 Ab do not necessarily imply that protective
mechanisms are mediated by IL-10 produced by the epitope-specific T
cells because anti-IL-10 Ab administration only partly inhibited
the peptide-induced suppression of AA. It is possible that the amounts
of the Ab may not be sufficient to neutralize endogenous IL-10.
Alternatively, other suppressive cytokines, including TGF-ß2 and
IL-13, may be involved in the peptide-induced suppression. Additional
experiments are needed to clarify these possibilities.
Anderton et al. (11) proposed that cross-reactivity between bacterial and self HSP65 may be important to maintain a protective self-reactive T cell population, which suppresses excessive Th1 responses, induced by exogenous Ags. Peptide 234252 of HSP70 used in this study differed from the equivalent rat HSP70 by eight amino acid substitutions and showed 58% amino acid identity. In our preliminary experiments, a T cell line specific for peptide 234256 responded to the conserved peptides corresponding to the equivalent region of the rat HSP70 homologue, supporting the hypothesis described above. However, additional experiments are needed to clarify this proposal.
There are striking strain differences in susceptibility to AA and listerial infection. Lewis rats are highly susceptible to AA, but resistant to listeriosis, whereas F344 and (F344 x Lewis)F1 rats are resistant to AA induction, but susceptible to listeriosis (34, 35, 36). Preliminary experiments revealed that the reactivity of T cells to peptide 234252 of HSP70 was closely correlated with susceptibility to listeriosis and resistance to AA induction. Activities of macrophages, including cytokine synthesis, were reported to be different between Lewis and F344 rats (37, 38). Thus, it would appear that the different processing activity of APC to generate the fragment epitopes of HSP70 between Lewis and F344 rats may be at least partially responsible for the differences in susceptibility to AA and listeriosis.
In conclusion, we have demonstrated that pretreatment with peptide 234252 of HSP70 derived from M.tb suppressed the development of AA. T cells from rats pretreated with peptide 234252 produced IL-10 in response to the relevant epitope and administration of T cells specific for peptide 234252 significantly protected against AA. These findings suggested that T cells recognizing peptide 234252 may have a regulatory role in inflammation during AA via the production of suppressive cytokines such as IL-10.
| Acknowledgments |
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| Footnotes |
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2 Address correspondence and reprint requests to Dr. Yasunobu Yoshikai, Laboratory of Host Defense and Germfree Life, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine. 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan. E-mail address: ![]()
3 Abbreviations used in this paper: HSP, heat-shock protein; AA, adjuvant arthritis; HKL, heat-killed Listeria; LN, lymph node; LNC, LN cell; MMC, mitomycin; M.tb, Mycobacterium tuberculosis; PPD, purified protein derivative of M.tb. ![]()
Received for publication April 6, 1999. Accepted for publication September 7, 1999.
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expression by astrocytes from experimental allergic encephalomyelitis-susceptible and -resistant rat strains. J. Exp. Med. 173:801.This article has been cited by other articles:
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