| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Departments of Pediatric Sciences (D.L., V.C., M.C.) and Pathology (E.S.), University of Pavia and Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, 27100 Pavia, Italy; Immunohematology and Transfusion Center (M.M., A.M.I.) and Clinical Epidemiology and Biometry Unit (A.D.S.), Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, 27100 Pavia, Italy; and Institute of Internal Medicine (R.N.), Spedali Civili, 25125 Brescia, Italy
Address all correspondence and requests for reprints to: Professor Larizza Daniela, Department of Pediatric Sciences, Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, P.le Golgi n. 2, 27100 Pavia, Italy. E-mail: d.larizza{at}smatteo.pv.it.
| Abstract |
|---|
|
|
|---|
Subjects and Methods: We retrospectively studied 90 children with ATD (median age 11.2 yr), 70 age- and sex-matched healthy subjects as controls, and 65 patients with Turner syndrome (median age 18.8 yr). Antibodies to Hp were determined at diagnosis in ATD patients and, in Turner patients, at the last control in cases without ATD and before the appearance of thyroid autoantibodies in the others. Serological and molecular human leukocyte antigen (HLA) typing for classes I and II polymorphisms was performed.
Results: Prevalence of positive Hp serology resulted significantly higher in ATD patients than controls (P = 0.032). No association was found between individual HLA alleles and Hp serology. HLA-A1, B8, and DRB1*0301 were found significantly associated with ATD. A significant interaction between HLA-DRB1*0301 and Hp infection was present in ATD patients and not controls (P = 0.007), suggesting that the copresence of these two factors might favor ATD development. A similar phenomenon was observed in Turner syndrome patients (P = 0.02; cumulative Mantel test, P = 0.0001).
Conclusions: Another target of Hp-elicited immune inflammatory response might be the thyroid gland in subjects with a peculiar immunogenetic profile so that ATD may be a consequence. Our findings suggest the opportunity of eradicating Hp infection in children with ATD and/or susceptible HLA alleles.
| Introduction |
|---|
|
|
|---|
Helicobacter pylori (Hp) is a Gram-negative gastric pathogen that is responsible for gastritis, gastric and duodenal ulcers (4), gastric mucosa-associated lymphoid tissue lymphoma, and gastric cancer (5). Furthermore, there is evidence that Hp infection can induce autoimmune processes against mucosa (6), with consequent autoimmune gastritis. Hp infection has been also proposed to be involved in the pathogenesis of nongastrointestinal conditions such as rosacea, ischemic heart disease (7, 8), and type 1 diabetes (9, 10). Finally, Hp infection has been reported to be more frequent in adult patients affected by ATD (11, 12, 13).
The aim of the present study was to evaluate the prevalence of Hp infection in young patients affected by ATD at the time of their first diagnosis. Furthermore, we investigated the possibility that a susceptible immunogenetic profile could influence the development of autoimmune thyroiditis in subjects with Hp infection.
| Patients and Methods |
|---|
|
|
|---|
Patients newly diagnosed with ATD in our Pediatric Department during the years 19821999 were submitted for determination of Hp antibodies and human leukocyte antigen (HLA) typing; all of them were from northern Italy. We searched for a possible association between ATD, HLA alleles, and Hp infection through a case-control study. In addition, because thyroid autoimmune disorders are very frequent in Turner syndrome, we also tested this association in cross-sectional studies in a group of Turner patients.
Patients
We retrospectively studied the following groups of patients. The first group consisted of 90 children with ATD (75 females and 15 males, median age at diagnosis 11.2 yr, range 1.121.8 yr). Sixty-five patients (52 females and 13 males, median age at diagnosis 11.1 yr, range 1.117.3 yr) had autoimmune thyroiditis (AT); 49 were treated with substitutive L-thyroxine, and 16 were euthyroid. Twenty-five patients (23 females and two males, median age at diagnosis 11.7 yr, range 3.121.8 yr) were affected by GD; 24 of them were treated with methimazole. Diagnosis of AT and GD had been determined on the basis of the presence of antithyroid antibodies (antibodies to thyroid peroxidase, thyroglobulin, and antibodies directed against TSH receptor); typical ultrasound aspects of the thyroid gland; and in some patients, before ultrasonography was available, fine-needle aspiration biopsy and cytology.
The second group consisted of 65 patients with Turner syndrome (median age at evaluation 18.8 yr, range 2.637.1 yr). Karyotype was 45,X in 42 cases, whereas mosaics and/or structural abnormalities of the X chromosome were found in the others. Thirty patients developed thyroid autoimmunity at the median age of 16.8 yr (range 4.631 yr), and six underwent substitutive treatment for hypothyroidism. Turner patients without thyroid antibodies were evaluated at a median age of 21.8 yr (range 2.637.1 yr). No statistically significant difference was present in the median age of the two groups of Turner patients.
Controls
As a control group, we chose 70 age- and sex matched subjects (15 males and 55 females; mean age 10 yr, range 220 yr; 28 were younger than 10 yr and 42 older) free of autoimmune disorders, coming from the same geographic area and evaluated during the same years as the patients. They had undergone clinical and laboratory evaluation as relatives of patients with congenital adrenal hyperplasia, with negative results. All the controls were subsequently evaluated for Hp serology, taking advantage of their harvested sera; 60 of them were HLA typed at the same resolution level as the patients. No statistically significant difference was present between ATD patients and controls for age and sex.
Hp-specific antibody determination
Antibodies to Hp were determined at the time of the first diagnosis in patients affected by ATD. In Turner patients serology for Hp was evaluated at the last control in cases without thyroid autoimmunity and before the appearance of thyroid autoantibodies in the others. As reported above, no significant difference was present in the median age of the two groups.
This retrospective study was possible, because sera had been taken from all patients, with either ATD or Turner syndrome, at the diagnosis as well as every 6 months during the follow-up.
Circulating antibodies against Hp were detected by a competitive ELISA test based on a monoclonal antibody against a 64-kDa specific Hp antigen. Briefly, 100 µl of undiluted serum sample and calibrators were added to microwells coated with a sonicate of Hp; 100 ml of peroxidase conjugated HpN45 were then added to all the wells. After 1 h of incubation, the plate was washed, color was developed with a tetramethylbenzidine solution, and absorbances read at 450. Anti-Hp titers were expressed in arbitrary units (units per milliliter) [95% confidence intervals (CIs)]. The intra- and interassay coefficients of variation of the assay were between 0.9 and 5.1% and between 3.2 and 9.7%, respectively; specificity of this method was 95% and sensitivity 100% (14).
HLA typing
Serological HLA typing for class I (HLA-A, B, C) and II (HLA-DR, DQ) antigens was obtained in all cases by means of standard microlymphocytotoxicity tests (15). Molecular typing of HLA-DRB1, DRB3, DRB4, DRB5, DQA1, and DQB1 genes was performed using the PCR-sequence-specific primer technique (16).
The study protocol was approved by the ethical committee of our institution. All the patients and/or their parents gave their written consent after being informed about the nature of the study.
Statistical analysis
For the case-control study, association between ATD and HLA alleles or Hp antibodies was tested with
2 or Fisher exact test as appropriate. P < 0.05 was considered significant. Then a multivariate logistic regression model was applied using ATD as dependent variable and HLA-DRB1*0301 allele, Hp antibodies, and their interaction as explicative variables.
In cross-sectional studies the relative risk of carrying both HLA-DRB1*0301 and Hp antibodies was assessed and tested with the
2 test.
The difference in the median age of the two groups of patients with Turner syndrome was tested with the nonparametric Mann-Whitney U test.
Finally, we used the Mantel test to combine the odds ratios (ORs) in a stratified data set, where the strata were formed by the ATD/control sample and the Turner sample.
| Results |
|---|
|
|
|---|
In the ATD sample, 24 of 90 patients (26.7%), eight of 25 (32%) with GD, and 16 of 65 (24.6%) with AT were positive for Hp antibodies; there were 20 of 75 positive females (26.6%) and four of 15 males (26.6%); eight of 38 patients (21%) were younger than 10 yr and 16 of 52 (30.7%) older. In the control group, nine of 70 subjects (12.8%) tested positive for Hp antibodies; there were one of 15 positive male (6.6%) and eight of 55 (14.5%) females; three of 28 subjects younger than 10 yr (10.7%) and six of 42 older (14.3%) tested positive for Hp serology.
The overall prevalence of positive Hp serology was significantly higher in ATD patients than in controls (24 of 90, 26.7% vs. nine of 70, 12.8%; P = 0.032; OR 2.46; 95% CI 1.046.24), also taking in account sex and age (Mantel test P = 0.03 and P = 0.01, respectively). The difference between patients and controls also had statistically significant results when ATD patients were stratified into two subgroups, those with AT and those with GD (Table 1
).
|
|
The OR relative to the HLA-DRB1*0301 effect in Hp-positive and Hp-negative ATD patients is reported in Table 3A
; it shows that this effect is restricted to Hp-positive subjects with ATD and the subgroup with AT. In fact, the frequency of DRB1*0301 in Hp-negative patients was similar to that in controls; also the percentage of Hp-positive subjects in DRB1*0301-negative subjects was not statistically different between ATD or AT and controls, so it seems to be the contemporaneous presence of DRB1*0301 and Hp antibodies to give the higher ORs. In patients with GD, the interaction between Hp antibodies and HLA-DRB1*0301 did not have statistically significant results, probably due to the small number of patients.
|
The effect of the simultaneous presence of the HLA-DRB1*0301 allele and Hp antibodies was independently retested in a sample of Turner patients through cross-sectional studies. In this sample we observed 22 subjects with Hp antibodies and nine subjects carrying the DRB1*0301 allele. All four patients (100%) with both HLA-DRB1*0301 and Hp antibodies developed AT, whereas only 26 of 61 (42.6%) without the copresence of these two factors developed AT (relative risk 2.35; P = 0.02); namely, eight were DRB1*0301 negative/HP positive and 18 were negative for both factors, whereas none of the five Turner patients DRB1*0301 positive/Hp negative developed AT (Table 4
).
|
2 of the simultaneous presence of Hp antibodies and HLA-DRB1*0301 in the two samples of patients with autoimmune thyroid disease and Turner syndrome is shown in Table 5
|
| Discussion |
|---|
|
|
|---|
This study suggests that another target of Hp-elicited immune-inflammatory response might be the thyroid gland and that autoimmune thyroid disease may be a consequence. The significantly increased prevalence of Hp seropositivity we observed in patients with ATD, with or without associated Turner syndrome, in the absence of an association between HLA alleles and Hp-positive serology per se, supports the hypothesis that Hp may have a role in promoting autoimmune disease of the thyroid gland. In fact, the finding of antibodies against Hp at the time of first diagnosis of thyroid disease (ATD sample) or even before it (Turner sample) suggests that Hp infection preceded ATD and had a role in the induction of autoimmune processes against thyroid. It should be noted that in previous adult studies, Hp antibodies were assessed during and not at diagnosis of thyroid disease or before it, as in this study (11, 12, 13).
The lack of association between HLA alleles and Hp-positive serology per se, independently of thyroid disease, rules out a role of the HLA-A, -B, -C, -DRB1, and -DQB1 genes in predisposing to Hp infection. On the other hand, the significant association we found between ATD and the HLA-DRB1*0301 allele, a well-known marker of autoimmunity, strongly supports a role of this allele in sustaining thyroid disease. This conclusion is further supported by the fact that this allele has been specifically involved in both cellular and humoral reactions against self-structures such as hepatocytes, pancreatic insular cells, and thyrocytes (26, 27, 28, 29). Thus, it seems likely that, in children possessing the HLA-DRB1*0301 allele, H. pylori infection may activate an immune response directed against thyroid cells.
Guidelines for the management of Hp infection in children (30) identified gastric and duodenal ulcer disease and the rare cases of mucosa-associated lymphoid tissue lymphoma and atrophic gastritis with intestinal metaplasia as the only indications for therapy. In light of our results, the finding of Hp infection in children with ATD is intriguing and raises the possibility that Hp eradication might prevent or attenuate AT. In fact, a decrease of antithyroid antibodies titer has been recently observed in adult patients with ATD after eradication of Hp infection (31). In addition, Faller et al. (32) observed that antiparietal cell antibody prevalence decreased in patients with autoimmune gastritis after Hp eradication. These findings, coupled with the increased risk for other autoimmune diseases and especially the risk of cancer and carcinoids inherent to Hp-induced atrophic gastritis (5, 19, 24, 33), suggest the opportunity of trying Hp eradication in Hp-infected children with ATD and/or susceptible HLA alleles.
Careful clinical trials are needed on this issue.
| Footnotes |
|---|
First Published Online November 1, 2005
Abbreviations: AT, Autoimmune thyroiditis; ATD, autoimmune thyroid disease; CI, confidence interval; GD, Graves disease; HLA, human leukocyte antigen; Hp, Helicobacter pylori; OR, odds ratio.
Received June 7, 2005.
Accepted October 24, 2005.
| References |
|---|
|
|
|---|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |