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Clinical and Diagnostic Laboratory Immunology, November 2001, p. 1056-1059, Vol. 8, No. 6
1071-412X/01/$04.00+0 DOI: 10.1128/CDLI.8.6.1056-1059.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Immunoglobulin G1 Antibody Response to
Helicobacter pylori Heat Shock Protein 60 Is Closely
Associated with Low-Grade Gastric Mucosa-Associated Lymphoid
Tissue Lymphoma
E.
Ishii,1
K.
Yokota,1
T.
Sugiyama,2
Y.
Fujinaga,1
K.
Ayada,1
I.
Hokari,2
S.
Hayashi,3
Y.
Hirai,3
M.
Asaka,2 and
K.
Oguma1,*
Department of Bacteriology, Okayama
University Medical School, 2-5-1 Shikata-cho Okayama,
700-8558,1 Department of
Gastroenterology, Hokkaido University Graduate School of Medicine, N15,
W7, Kita-ku, Sapporo, 060-0815,2 and
Department of Microbiology, Jichi Medical School, 3311-1 Yakushiji Minamikouch-cho Kawauch-Gun,
329-0498,3 Japan
Received 5 April 2001/Returned for modification 24 May
2001/Accepted 23 July 2001
 |
ABSTRACT |
Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is
related to Helicobacter pylori infection. Specifically, it
has been pointed out that pathogenesis of MALT lymphoma involves the 60-kDa heat shock protein (hsp60). To investigate humoral immune responses to the H. pylori hsp60 in patients with
gastroduodenal diseases and patients with MALT lymphoma, the hsp60 of
H. pylori was expressed with a glutathione
S-transferase fusion protein and was purified
(recombinant hsp60). Sera were obtained from H. pylori-positive patients with gastroduodenal diseases (MALT lymphoma, n = 13; gastric ulcer, n = 20; duodenal ulcer, n = 20; gastritis,
n = 20) and from H. pylori-negative
healthy volunteers (n = 9). Sera from patients with
MALT lymphoma were also obtained at two times: before and after
eradication therapy. Antibodies to hsp60 and H. pylori were
assessed by enzyme-linked immunosorbent assay. The levels of
immunoglobulin G (IgG) antibodies to the hsp60 of H. pylori-positive patients with gastroduodenal diseases were
significantly elevated compared to those in the controls. The levels of
IgG1 antibodies to hsp60 were elevated and correlated with the levels
of anti-H. pylori antibodies in patients with MALT
lymphoma. Humarol immunity against hsp60 may be important and relevant
to gastroduodenal diseases induced by H. pylori infection.
 |
INTRODUCTION |
Helicobacter
pylori is now recognized as a cause of gastritis, peptic ulcer,
gastric cancer, and gastric mucosa-associated lymphoid tissue (MALT)
lymphoma (9, 19). Several H. pylori pathogenic
factors, including CagA and VacA, may contribute to the gastric
mucosal damage (6, 7). In recent years, it has also been
accepted that host immune reactions play an important role in the
pathogenesis of H. pylori infection. Although H. pylori is a noninvasive bacterium and is restricted to gastric
epithelial cells, infection with H. pylori induces humoral
and cellular immune responses in the gastric mucosa (16,
22). Bacterial attachment causes induction of interleukin-8
(IL-8) release, and Cag proteins evoke activation of nuclear
factor-
B and release of IL-8 that may support leukocyte attachment
during inflammation (8, 17, 21). However, the bacterial
antigens associated with inflammation are still not clear.
Heat shock proteins (hsp's) are immunodominant antigens in various
diseases including H. pylori infection (4, 26).
Our previous studies have shown that the 60-kDa hsp (hsp60) is
expressed in the follicular dendritic cells of the gastric mucosa in
patients with gastric MALT lymphoma (15) and that
antibodies to human hsp60 can be detected in MALT lymphoma patients
(14). These results indicate that hsp60 may be associated
with the host immune reaction in H. pylori infection,
specifically, the pathogensis of gastric MALT lymphoma.
In the present study, H. pylori hsp60 recombinant protein
was expressed, and the levels of immunoglobulin G (IgG), IgG1, IgG2, IgM, and IgA antibodies to hsp60 in sera were measured in patients with
gastric ulcer, duodenal ulcer, gastritis, and gastric MALT lymphoma to
demonstrate the immunological role of hsp60 in H. pylori-infected patients.
 |
MATERIALS AND METHODS |
Patients.
Sera were obtained from 73 H. pylori-positive patients, including 13 patients with gastric MALT
lymphoma (5 women and 8 men; mean age, 56.6 years), 20 patients with
gastric ulcer (3 women and 17 men; mean age, 46.3 years), 20 patients
with duodenal ulcer (10 women and 10 men; mean age, 30.4 years), and 20 patients with gastritis (6 women and 14 men; mean age, 41.5 years).
Sera were also obtained from nine H. pylori-negative
volunteers (six women and three men; mean age, 37.9 years old).
Informed consent was obtained from each patient and healthy volunteer.
In nine patients with gastric MALT lymphoma who were treated with
eradication therapy (a 1-week course of omeprazole at 40 mg/day,
amoxicillin at 1,500 mg/day, and clarithromycin at 400 mg/day),
endoscopic findings and histopathology were assessed 6 months after
therapy and serum samples were collected. All sera were collected at
the Hokkaido University Hospital and were stored at
80°C.
Diagnosis.
The histology of MALT lymphoma was assessed
according to the Wotherspoon classification. All the lymphomas
were diagnosed as low-grade MALT lymphoma. Diagnosis of the other
diseases was determined according to the symptoms and by endoscopy.
Infection with H. pylori was confirmed by culture, the rapid
urease test, and histology of gastric biopsy specimens and by the
presence of serum antibodies to H. pylori as detected by
enzyme-linked immunosorbent assay (ELISA) (14). H. pylori was detected in the gastric mucosae of all patients whose
sera were positive for anti-H. pylori antibodies. In the
healthy control volunteers, negativity for H. pylori
infection was defined by serology.
Cloning, expression, and purification of recombinant
protein.
The hsp60 protein of H. pylori was expressed
as a glutathione S-transferase fusion protein by PCR
cloning. PCR primers were designed on the basis of sequences published
in GenBank. To facilitate cloning, restriction endnuclease cleavage
sites were included in the PCR primer sequence. The PCR primer pair of
GGAGGATCCCCATGGCAAAAGAAATCAAATTT and
GGGGTCGACCATCATGCCGCCCATGCCTCC was used to amplify the open reading frame from purified H. pylori ATCC 43504 genomic DNA.
The PCR was performed in a 20-µl volume containing Extaq polymerase
(Takara), 5 nM sense and antisense oligonucleotide primers, and
500 ng of H. pylori genomic DNA. The cycling conditions were 25 cycles of 94°C for 30 s, 55°C for 30 s, and 72°C for
30 s. The amplicon was cut with BamHI and
SalI restriction endonucleases and cloned into the vector
pGX-5X3 (Amersham Pharmacia) by standard molecular biology techniques,
and the resultant plasmid was transformed into Escherichia
coli DH-5
. Recombinant protein was expressed at 25°C in
Luria-Bertani broth containing 2% glucose and ampicillin (100 µg/ml). At an optical density (OD) at 540 nm of 0.6 to 0.8, the
culture was induced with 0.1 mM
isopropyl-
-D-thiogalactopyranoside and was incubated at
37°C for 3 h. The cells were harvested by centrifugation at
7,000 × g for 10 min and resuspended in ice-cold phosphate-buffered saline (PBS). The bacterial suspension was frozen at
70°C and thawed, and the cells were disrupted by sonication on ice
for 2 min with a probe sonicator (Astron) set to full power. Soluble
fusion protein expressed by the glutathione
S-transferase-hsp clone (hsp60) was purified by
glutathione-Sepharose 4B (Amersham Pharmacia) affinity chromatography
according to the manufacturer's instructions.
ELISA for detection of antibodies to hsp60 and H. pylori.
Serum antibodies to hsp60 and H. pylori
were measured by ELISA. Ninety-six-well microtiter plates were coated
with hsp60 fusion protein (10 µg/ml) or H. pylori lysate
(50 µg/ml) in 100 µl of 0.1 M carbonate-bicarbonate buffer
(pH 9.6) overnight at 4°C. After the wells were blocked with
PBS containing 10% skim milk, the plates were incubated with sera, at
a 1:100 dilution for hsp60 antibody or 1:1,000 for H. pylori
antibody, for 2 h and washed with PBS containing 0.05% Tween 20. Peroxidase-labeled rabbit anti-human IgA, IgM, or IgG antibody (DAKO
Japan) was then added, and the plates was incubated for 2 h. After
the plate was washed, the wells were reacted with 1 mg of
o-phenylenediamine (Wako Pure Chemical) per ml in citrate
buffer (pH 5.5). The ODs were measured at 490 nm on an ELISA plate
reader (Bio-Rad). Cutoff ODs were determined as the mean plus 2 times
the standard deviation for the sera obtained from negative controls.
For the detection of IgG1 or IgG2 antibodies, the contents of the wells
of the microtiter plates were reacted with human sera
as described
above. Anti-human IgG1 or IgG2 monoclonal antibodies
(Pharmingen) were
then added, and the plates were incubated for
2 h, followed by
washing. The wells were continuously reacted
with anti-mouse antibody
conjugated with horseradish peroxidase
(DAKO Japan). After the plates
were washed, the enzyme reaction
described above was used for final
color
development.
Statistical analysis.
Differences in the ODs of the
antibodies among the disease groups were evaluated by the Student
t test. Correlation between antibodies to H. pylori and hsp60 were evaluated with Pearson's correlation
coefficient. P values of <0.05 were considered to represent
a significant difference.
 |
RESULTS |
IgG, IgM, and IgA antibodies to hsp60.
The levels of IgG
antibodies to H. pylori whole antigens and hsp60 in
the sera of patients with gastroduodenal diseases were significantly
higher than those in the sera of healthy control (Fig. 1A and
B). The cutoff ODs of the ELISA for
anti-whole-antigens and hsp60 antibodies were 0.59 and 1.20 respectively. The specificity and sensitivity of IgG antibodies to the
whole antigens were 100 and 91.8%, respectively and the sensitivity
and specificity of IgG antibodies to hsp60 were 100 and 69.9%
respectively. The levels of IgM antibodies and IgA antibodies were
elevated, but they were not significantly different from those in the
control group (Fig. 1C and D).

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FIG. 1.
Levels of antibodies to H. pylori and hsp60
in patients with gastroduodenal disease. Antibody levels in patients
with gastric ulcer (GU), duodenal ulcer (DU), gastritis (G), and
gastric MALT lymphoma and in H. pylori-negative healthy
volunteer (cont) were measured by ELISA. (A) IgG antibodies to H. pylori; (B) IgG antibodies to hsp60; (C) IgM antibodies to hsp60;
(D) IgA antibodies to hsp60. *, P < 0.05 versus the
control group; **, P < 0.01 versus the control
group.
|
|
Correlation coefficient between IgG and IgG1 antibodies to hsp60
and H. pylori.
IgG isotype antibodies were measured in
patients with gastroduodenal diseases. The levels of IgG1 antibodies to
H. pylori and hsp60 were significantly elevated in patients
with gastroduodenal diseases compared with the levels in the control
group. However, the levels of IgG2 antibodies to both H. pylori whole antigens and hsp60 were increased in patients, but
the difference was not statistically significant (data not
shown). We statistically analyzed correlations between IgG antibodies
to H. pylori and IgG1 antibodies to hsp60 in the patients.
The patients with MALT lymphoma had a high correlation coefficient,
although patients with other disease had only low correlation
coefficients (Fig. 2).

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FIG. 2.
Scatter diagrams of anti-H. pylori and
anti-hsp60 antibodies. Correlation coefficients for IgG1 antibodies
between H. pylori and hsp60 are 0.45 for patients with
gastric ulcers (A), 0.398 for patients with duodenal ulcers, (B), 0.376 for patients with gastritis (C), and 0.72 for patients with MALT
lymphoma (D).
|
|
IgG antibodies after eradication therapy in patients with MALT
lymphoma.
We studied the change in total IgG antibody levels after
eradication therapy in nine patients with MALT lymphoma. Eradication therapy resulted in histological and endscopic remission in six MALT
lymphoma patients; however, three patients did not have a regression 6 months after eradication therapy. IgG antibody levels to whole H. pylori and hsp60 in the patients with regression were significantly decreased (Fig. 3A and B).
One levels of IgG antibodies to hsp60 in patients with or without
regressions were decreased following eradication therapy, and at
pretreatment levels of IgG antibody to hsp60 in the six patients with
regressions were significantly higher than those in the three patients
without regressions (Fig. 3B).

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|
FIG. 3.
Antibody levels pre- or posteradication in patients with
MALT lymphoma. (A) Anti-H. pylori IgG antibodies at pre- and
posteradication therapy in six healed patients (left side of the
panel) and in three patients without regression (right side of the
panel). (B) Anti-hsp60 IgG antibodies. *, P < 0.05
versus antibody levels pretreatment in patients with regression as a
result of eradication therapy.
|
|
 |
DISCUSSION |
We have reported on the measurement of the levels of
immunoglobulin antibody against hsp60 in H. pylori-infected
patients. Specifically, the IgG1 response against hsp60 is closely
associated with MALT lymphoma in H. pylori-infected
patients. IgG1 antibodies are produced by B cells activated under the
T-helper 2 (Th2) cytokine IL-4. Th1 cells that produce gamma interferon
are able to promote the production of IgG2 opsonizing and
complement-fixing antibodies. An IgG subclass response to H. pylori in patients with chronic active gastritis and duodenal
ulcer was reported by Bontkes et al (5). They indicated
that the titers of IgG1 antibodies to the bacteria were raised in
patients with H. pylori infection and that the titers of
IgG2 antibodies in duodenal ulcer patients were higher than those in
gastritis patients. In this study, there was a strong
correspondence between total serum anti-H. pylori and
anti-hsp60 IgG levels in patients with gastritis; however, the
correspondence for IgG1 and IgG2 antibodies individually was weak. The
anti-hsp60 IgG1 antibodies of patients with MALT lymphoma had a strong
correspondence with anti-H. pylori IgG1 antibodies. The
results indicate that a long-standing H. pylori infection induced the Th-2 reaction against hsp60 in patients with gastric MALT lymphoma.
We have reported that autoimmunity through human hsp60 is involved in
patients with MALT lymphoma (14, 15) and that it may be
caused by a long-term Th-2 reaction against bacterial hsp60. Infection
with H. pylori also leads to an IgG response against the
bacteria and hsp60 in patients with peptic ulcer and gastritis. We
assessed the anti-hsp60 IgG antibody titers in a few patients with
peptic ulcers and found that total levels of IgG to hsp60 were
decreased by antibacterial eradication therapy (data not shown).
However, the responses of Th-1 (IgG2) and/or Th-2 (IgG1) were diverse
in patients with gastritis and peptic ulcer; hence, gastritis and ulcer
diseases may be characterized by the development of cellular or humoral
immune responses at various stages.
Some markers related to the pathogenesis of gastric MALT lymphoma have
been investigated. Homozygous p16 tumor suppressor gene deletion was
found in the gastric mucosae of patients with high-grade MALT lymphoma
but were not found in those of patients with gastritis
(18). The cell cycle regulatory gene
(cdc2/cdk1) might play an important role in the modulation
of cellular death, proliferation, and translation during the evolution
of chronic gastritis to MALT lymphoma (3). PCR detection
of IgH rearrangement in gastric biopsy specimens could be used to
monitor MALT lymphoma regression during treatment (1).
These observations about host epithelial cell growth and/or lymphocyte
regulations indicated that some bacterial antigens were involved in the
progression of the gastric lesion of MALT lymphoma; however, the
bacterial antigen was not clearly detected. The present study showed
that the levels of IgG antibodies against hsp60 are markedly decreased during eradication therapy and may possibly be used as a marker of the
host immune reactions in patients with MALT lymphoma.
Bacterial virulence factors, like CagA and VacA s1, show a
strong association with duodenal ulcer disease (2, 20,
23). Serological study of patients indicated that MALT lymphoma
is associated with H. pylori strains expressing the CagA
protein (10). On the other hand, a large variety of
H. pylori strains could be considered responsible for the
induction of MALT lymphoma, as judged from the heterogeneity of their
antigenic properties and the fact that CagA did not seem to be a
virulence marker associated with the disease in Japan
(13). H. pylori infection induces class II
major histocompatibility complex expression and CD4-positive T-cell
activation (11); however, antigens associated with
lymphocyte activation were not detected. We have reported that local
immunoglobulin against hsp60 is associated with infiltrating cell
numbers in the gastric mucosae of patients with gastritis
(12) and have also reported that anti-hsp60 antibodies are
relevant to gastric inflammation in patients with peptic ulcer during
eradication therapy (25). In addition, the level of
expression of CD40L on the peripheral blood mononuclear cells (PBMCs)
of patients with MALT lymphoma was increased by cytokines
(granulocyte-macrophage colony-stimulating factor and IL-4) or by
cytokine plus hsp60 stimulation compared to the level of expression on
PBMCs of patients with gastritis or healthy volunteers. The production
of IL-4 in PBMC cultures was also increased by cytokines and/or hsp60
stimulation in patients with MALT lymphoma. In patients with MALT
lymphoma, however, the level of production of gamma interferon was at
the low end (24). Hence, hsp60 may be an important antigen
for the production of antibodies and T-cell activation in patients with H. pylori infection.
In conclusion, the present study indicated that H. pylori
infection induced an IgG1 response (humoral Th-2 immunity) against hsp60 in patients with MALT lymphoma, and that may be a disposition of
MALT lymphoma as a host factor. This study also indicated that hsp60 is
an immunodominant antigen in H. pylori infection, and analysis of the subclass of IgG antibody to hsp60 may be used to assess
the immunological future in patients with H. pylori-associated diseases. This information will provide
immunological data that can be used to make diagnoses once further
studies have been conducted.
 |
FOOTNOTES |
*
Corresponding author. Mailing address: Department of
Bacteriology, Okayama University Medical School, 2-5-1 Shikata-cho
Okayama, 700-8558, Japan. Phone and fax: 81-86-235-7162. E-mail:
kuma{at}med.okayama-u.ac.jp.
 |
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Role of heat shock proteins in protection from and pathogenesis of infectious diseases.
Clin. Microbiol. Rev.
12:19-39[Abstract/Free Full Text].
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Clinical and Diagnostic Laboratory Immunology, November 2001, p. 1056-1059, Vol. 8, No. 6
1071-412X/01/$04.00+0 DOI: 10.1128/CDLI.8.6.1056-1059.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
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