Journal of Medical Virology 38:13%141 (1992)
HTLV-I Infection in Patients With Autoimmune Thyroiditis (Hashimoto’sThyroiditis) H. Kawai, T. Inui, S. Kashiwagi, T. Tsuchihashi, K. Masuda, A. Kondo, S. Niki, M. Iwasa, and S. Saito First Department of Internal Medicine, School of Medicine, The University of Tokushima (H.K., S.K., T.T., K.M., A.K., S.N., M.I., S.S.), and Department of Neurology, National Sanatorium Tokushima Hospital ( T.I.), Tokushima, Japan To investigate the possible relationship of HTLV-I virus infection to autoimmune thyroid disease, we examined, firstly, the frequency of HTLV-I seropositivity among patients with Hashimoto’s thyroiditis and, secondly, the frequency of Hashimoto’s thyroiditis in patients with HTLV-I associated myelopathy/tropical spastic paraparesis (HAMITSP). Of 144 patients with Hashimoto’s thyroiditis in the Tokushima and Kochi Prefectures, Japan, 9 (6.3%) were positive for serum HTLV-Ivirus antibody 2 of whom were confirmed histologically to have Hashimoto’s thyroiditis. This percentage is significantly higher ( P < 0.01) than the estimated prevalence (2.2%) of HTLV-I carriers among the general population in this region. Of 9 patients with HAM/TSP, 3 (33.3%),including 2 biopsy-proven cases, had evidence of Hashimoto’s thyroiditis. This proportion is apparently much higher than the prevalence (1.7%) of Hashimoto‘s thyroiditis in the general population. These findings suggest that HTLV-I virus may be related to the development of Hashimoto’s thyroiditis. Q 1992 Wiley-Liss, Inc.
KEY WORDS: HTLV-I, HAM/TSP, Hashimoto‘s thyroiditis, autoimmune thyroiditis, epidemiology, retrovirus
INTRODUCTION Human T-lymphotropic virus type I (HTLV-I) is a retrovirus etiologically associated with adult T-cell leukemia. The exact pathogenetic mechanism of HTLV-I associated myelopathy/tropical spastic paraparesis (HAMITSP) [Gessain et al., 1985; Osame et al., 19861 is still unknown. However, one of the most favored hypotheses is a n immune-mediated mechanism because this disease is frequently associated with a spectrum of autoimmune disorders. During studies on autoimmune disorders associated with HAMITSP [Kawai et al., 1991a1, we found 2 HAM/TSP patients with Hashimoto’s thyroiditis [Kawai et al., 1991bI. 0 1992 WILEY-LISS, INC.
We screened patients with Hashimoto’s thyroiditis for serum anti-HTLV-I antibody, and HAMITSP patients for anti-thyroid antibodies to investigate the relationship between HTLV-I virus infection and the pathogenesis of Hashimoto’s thyroiditis.
MATERIALS AND METHODS The subjects studied were 144 patients with Hashimoto’s thyroiditis (13 males, 131 females; age, 24-82 yr, mean 62.4 yr) and 9 patients with HAM/TSP (one male, 8 females; age, 42-65 yr, mean 57.3 yr). Of these patients, 102 with Hashimoto’s thyroiditis and 2 with HAM/TSP were inhabitants of Tokushima Prefecture and 42 with Hashimoto’s thyroiditis and 1 with HAM/ TSP were inhabitants of the Aki and Kami counties of Kochi Prefecture which are adjacent to the southern part of Tokushima Prefecture. Hashimoto’s thyroiditis was diagnosed by 1)the presence of diffuse and hard goitre, the presence of antithyroid microsomal antibody or anti-thyroglobulin antibody, and euthyroid or hypothyroid function; or 2) the presence of anti-thyroglobulin autoantibody and hypothyroidism in the absence of goitre. Biopsy of the thyroid was performed in selected cases to confirm the diagnosis of Hashimoto’s thyroiditis. HAM/TSP was diagnosed according to the criteria of Osame et al. [1990]. Anti-thyroid microsomal antibody (MCAb) and antithyroglobulin antibody (TGAb) were measured with Serocrit MC and TG kits, respectively (Sanko-Junyaku, Tokyo, Japan). TGAb was also assayed with a n RIA kit (CIS Bio-international, Cedex, France). HTLV-I antibodies in the serum and cerebrospinal fluid were measured by a particle agglutination method with a Serodia HTLV-I kit (Fujirebio Inc., Tokyo, Japan). Positive samples were further characterized by western blotting with a Novapath ATL kit (BioRad Lab., Richmond, CA). The serum specimens with p19 band and
Accepted for publication March 19, 1992. Address reprint requests t o Hisaomi Kawai, M.D., First Department of Internal Medicine, School of Medicine, The University of Tokushima, Kuramoto-3, Tokushima 770, Japan.
HTLV-I and Autoimmune Thyroiditis
139
p24 band were judged a s HTLV-I positive. Statistical analysis was done by Wilcoxon’s method or the binomial test.
RESULTS HTLV-I Infection in Patients With Hashimoto’s Thyroiditis Of 144 patients with Hashimoto’s thyroiditis, 9 (6.3%; 8 females and 1 male) had serum HTLV-I antibody. These patients were 4 (3.9%) of 102 living in Tokushima Prefecture and 5 (11.9%) of 42 living in Kochi Prefecture. The frequency of 6.3% was significantly higher (P < 0.01) than the expected frequency (2.2%)in these two prefectures. The age of these 9 patients ranged from 24 to 76 yr (mean 62.1 yr), which was not significantly different (P > 0.01) from that of sero-negative patients (mean 56.1 yr). The male to femle ratio was 1 : 8. Goitre was noted in all the patients except one female. In these sero-positive patients, the titre of MCAb antibody ranged from 1:lOO to 1:12,800 (normal value; below 100) with a mean of 1:3,500 and that of TGAb antibody from a normal value (below 100) to 1:400,000 with a mean of 1:45,117. The titres in the seronegative patients ranged from a normal value to 1:102,400 (mean 1:22,664) for MCAb, and from a normal value to over 1:102,400 (mean 1:16,834) for TGAb. The titres of these antibodies in HTLV-I sero-positive and sero-negative patients were not significantly different. Thyroid function was normal in 3 patients and decreased in 6 patients. Two patients were found by thyroid echography to have small nodular hypoechoic regions. Other clinical features seemed to be similar to those in Hashimoto’s thyroiditis without HTLV-I infection. The serum HTLV-I antibody titre, determined by a particle agglutination method, ranged from 1 5 1 2 to 1:65,536 (mean, 1:11,605). On western blot analysis, bands of both p19 and p24 were found in all these cases (Fig. 1).Two of the HTLV-I sero-positive patients (cases 5 and 7) were confirmed to have Hashimoto’s thyroiditis by histological examination of thyroid tissues.
Fig. 1. Western blot analysis for anti HTLV-I of serum specimens from 12 patients with Hashimoto’s thyroiditis. C indicates control sero-positive serum, and figures show case numbers. Bands of p19, p24, gp46, and p53 are seen in cases 2-4 and 8-12, and those of p19, p24, and p53 in cases 5 and 7. Bands of p19 and p24 are seen in cases 1 and 6.
tibody are summarized in Table I. Cases 10, 11,and 12 are those who also had HAM/TSP.
DISCUSSION Of the patients examined in Tokushima and Kochi Prefectures with Hashimoto’s thyroiditis, 6.3% were sero-positive for HTLV-I. This was a significantly higher percentage (P < 0.01) than that expected (2.2%) according to the frequency of HTLV-I carriers and the number of patients in the two prefectures [Kawai et al., 1991a; Taguchi et al., 19861. This variation in the frequency was not the result of a n age difference a s the ages of sero-positive and sero-negative patients were not significantly different. Hashimoto’s Thyroiditis With HAM/TSP Three of 9 HAMPTSP patients (33.3%) had HashimoOf 9 HAMITSP patients, 3 (33.3%) had Hashimoto’s to’s thyroiditis. Although the total number is small, the thyroiditis. These 3 cases gave positive reactions for percentage is much higher than the prevalence (1.7%) MCAb and/or TGAb. Diffuse and hard goitre was ob- of Hashimoto’s thyroiditis among females of over 30 served in 2 patients (cases 10 and 11). Thyroid echo- years old in Tokushima Prefecture [Oshimo et al., grams showed small nodular hypoechoic regions in all 3 19881. These results suggest a possible causal relationship patients and biopsy of the goitre confirmed Hashimoto’s thyroiditis in 2 cases [Kawai et al., 1991bl. Two pa- between HTLV-I infection and Hashimoto’s thyroiditis tients (cases 10 & 12) were hypothyroid, and one (case in a certain proportion of the patients. To the best of our knowledge, this has not previously been reported. 11)euthyroid. Viral infection may lead to a n autoimmune disorder HTLV-I antibody titres of the 3 cases of thyroiditis ranged from 1:8,192 to 1:131,072 (mean, 1:51,883), by several mechanisms [Mims, 1986; Schattner and which was higher (P < 0.05)than the mean of 1:11,605in Rager-Zisman, 19901; 1) modulation of the host imthe 6 patients with HAM/TSP without Hashimoto’s mune system, 2) harmful effects of reactive viral antithyroiditis. Western blot analysis demonstrated p19, bodies, including molecular mimicry and immune complex formation, 3) modification of the antigenicity of a p24, gp46, and p53 in all these 3 cases (Fig. 1). The clinical and laboratory profiles of the 12 patients host cell protein(s1, or 4) induction of class I1 antigen with Hashimoto’s thyroiditis with positive HTLV-I an- expression by interferons and other cytokines such as
Kawai et al.
140
Case No. 1* 2 3* 4*
5 6* 7 8 9* 10 11
12*
Age (yr) 61 54 76 71 64 67 67 24 76 47 60 65
TABLE I. Summary of Patients With Hashimoto’s Thyroiditis and HTLV-I Antibody? MCAb TGAb TGAb(R1A) Thyroid Sex Diagnosis Struma (titres) (titres) (U/ml) function 67.0
HTLV-I Infection in Patients With Autoimmune Thyroiditis (Hashimoto’sThyroiditis) H. Kawai, T. Inui, S. Kashiwagi, T. Tsuchihashi, K. Masuda, A. Kondo, S. Niki, M. Iwasa, and S. Saito First Department of Internal Medicine, School of Medicine, The University of Tokushima (H.K., S.K., T.T., K.M., A.K., S.N., M.I., S.S.), and Department of Neurology, National Sanatorium Tokushima Hospital ( T.I.), Tokushima, Japan To investigate the possible relationship of HTLV-I virus infection to autoimmune thyroid disease, we examined, firstly, the frequency of HTLV-I seropositivity among patients with Hashimoto’s thyroiditis and, secondly, the frequency of Hashimoto’s thyroiditis in patients with HTLV-I associated myelopathy/tropical spastic paraparesis (HAMITSP). Of 144 patients with Hashimoto’s thyroiditis in the Tokushima and Kochi Prefectures, Japan, 9 (6.3%) were positive for serum HTLV-Ivirus antibody 2 of whom were confirmed histologically to have Hashimoto’s thyroiditis. This percentage is significantly higher ( P < 0.01) than the estimated prevalence (2.2%) of HTLV-I carriers among the general population in this region. Of 9 patients with HAM/TSP, 3 (33.3%),including 2 biopsy-proven cases, had evidence of Hashimoto’s thyroiditis. This proportion is apparently much higher than the prevalence (1.7%) of Hashimoto‘s thyroiditis in the general population. These findings suggest that HTLV-I virus may be related to the development of Hashimoto’s thyroiditis. Q 1992 Wiley-Liss, Inc.
KEY WORDS: HTLV-I, HAM/TSP, Hashimoto‘s thyroiditis, autoimmune thyroiditis, epidemiology, retrovirus
INTRODUCTION Human T-lymphotropic virus type I (HTLV-I) is a retrovirus etiologically associated with adult T-cell leukemia. The exact pathogenetic mechanism of HTLV-I associated myelopathy/tropical spastic paraparesis (HAMITSP) [Gessain et al., 1985; Osame et al., 19861 is still unknown. However, one of the most favored hypotheses is a n immune-mediated mechanism because this disease is frequently associated with a spectrum of autoimmune disorders. During studies on autoimmune disorders associated with HAMITSP [Kawai et al., 1991a1, we found 2 HAM/TSP patients with Hashimoto’s thyroiditis [Kawai et al., 1991bI. 0 1992 WILEY-LISS, INC.
We screened patients with Hashimoto’s thyroiditis for serum anti-HTLV-I antibody, and HAMITSP patients for anti-thyroid antibodies to investigate the relationship between HTLV-I virus infection and the pathogenesis of Hashimoto’s thyroiditis.
MATERIALS AND METHODS The subjects studied were 144 patients with Hashimoto’s thyroiditis (13 males, 131 females; age, 24-82 yr, mean 62.4 yr) and 9 patients with HAM/TSP (one male, 8 females; age, 42-65 yr, mean 57.3 yr). Of these patients, 102 with Hashimoto’s thyroiditis and 2 with HAM/TSP were inhabitants of Tokushima Prefecture and 42 with Hashimoto’s thyroiditis and 1 with HAM/ TSP were inhabitants of the Aki and Kami counties of Kochi Prefecture which are adjacent to the southern part of Tokushima Prefecture. Hashimoto’s thyroiditis was diagnosed by 1)the presence of diffuse and hard goitre, the presence of antithyroid microsomal antibody or anti-thyroglobulin antibody, and euthyroid or hypothyroid function; or 2) the presence of anti-thyroglobulin autoantibody and hypothyroidism in the absence of goitre. Biopsy of the thyroid was performed in selected cases to confirm the diagnosis of Hashimoto’s thyroiditis. HAM/TSP was diagnosed according to the criteria of Osame et al. [1990]. Anti-thyroid microsomal antibody (MCAb) and antithyroglobulin antibody (TGAb) were measured with Serocrit MC and TG kits, respectively (Sanko-Junyaku, Tokyo, Japan). TGAb was also assayed with a n RIA kit (CIS Bio-international, Cedex, France). HTLV-I antibodies in the serum and cerebrospinal fluid were measured by a particle agglutination method with a Serodia HTLV-I kit (Fujirebio Inc., Tokyo, Japan). Positive samples were further characterized by western blotting with a Novapath ATL kit (BioRad Lab., Richmond, CA). The serum specimens with p19 band and
Accepted for publication March 19, 1992. Address reprint requests t o Hisaomi Kawai, M.D., First Department of Internal Medicine, School of Medicine, The University of Tokushima, Kuramoto-3, Tokushima 770, Japan.
HTLV-I and Autoimmune Thyroiditis
139
p24 band were judged a s HTLV-I positive. Statistical analysis was done by Wilcoxon’s method or the binomial test.
RESULTS HTLV-I Infection in Patients With Hashimoto’s Thyroiditis Of 144 patients with Hashimoto’s thyroiditis, 9 (6.3%; 8 females and 1 male) had serum HTLV-I antibody. These patients were 4 (3.9%) of 102 living in Tokushima Prefecture and 5 (11.9%) of 42 living in Kochi Prefecture. The frequency of 6.3% was significantly higher (P < 0.01) than the expected frequency (2.2%)in these two prefectures. The age of these 9 patients ranged from 24 to 76 yr (mean 62.1 yr), which was not significantly different (P > 0.01) from that of sero-negative patients (mean 56.1 yr). The male to femle ratio was 1 : 8. Goitre was noted in all the patients except one female. In these sero-positive patients, the titre of MCAb antibody ranged from 1:lOO to 1:12,800 (normal value; below 100) with a mean of 1:3,500 and that of TGAb antibody from a normal value (below 100) to 1:400,000 with a mean of 1:45,117. The titres in the seronegative patients ranged from a normal value to 1:102,400 (mean 1:22,664) for MCAb, and from a normal value to over 1:102,400 (mean 1:16,834) for TGAb. The titres of these antibodies in HTLV-I sero-positive and sero-negative patients were not significantly different. Thyroid function was normal in 3 patients and decreased in 6 patients. Two patients were found by thyroid echography to have small nodular hypoechoic regions. Other clinical features seemed to be similar to those in Hashimoto’s thyroiditis without HTLV-I infection. The serum HTLV-I antibody titre, determined by a particle agglutination method, ranged from 1 5 1 2 to 1:65,536 (mean, 1:11,605). On western blot analysis, bands of both p19 and p24 were found in all these cases (Fig. 1).Two of the HTLV-I sero-positive patients (cases 5 and 7) were confirmed to have Hashimoto’s thyroiditis by histological examination of thyroid tissues.
Fig. 1. Western blot analysis for anti HTLV-I of serum specimens from 12 patients with Hashimoto’s thyroiditis. C indicates control sero-positive serum, and figures show case numbers. Bands of p19, p24, gp46, and p53 are seen in cases 2-4 and 8-12, and those of p19, p24, and p53 in cases 5 and 7. Bands of p19 and p24 are seen in cases 1 and 6.
tibody are summarized in Table I. Cases 10, 11,and 12 are those who also had HAM/TSP.
DISCUSSION Of the patients examined in Tokushima and Kochi Prefectures with Hashimoto’s thyroiditis, 6.3% were sero-positive for HTLV-I. This was a significantly higher percentage (P < 0.01) than that expected (2.2%) according to the frequency of HTLV-I carriers and the number of patients in the two prefectures [Kawai et al., 1991a; Taguchi et al., 19861. This variation in the frequency was not the result of a n age difference a s the ages of sero-positive and sero-negative patients were not significantly different. Hashimoto’s Thyroiditis With HAM/TSP Three of 9 HAMPTSP patients (33.3%) had HashimoOf 9 HAMITSP patients, 3 (33.3%) had Hashimoto’s to’s thyroiditis. Although the total number is small, the thyroiditis. These 3 cases gave positive reactions for percentage is much higher than the prevalence (1.7%) MCAb and/or TGAb. Diffuse and hard goitre was ob- of Hashimoto’s thyroiditis among females of over 30 served in 2 patients (cases 10 and 11). Thyroid echo- years old in Tokushima Prefecture [Oshimo et al., grams showed small nodular hypoechoic regions in all 3 19881. These results suggest a possible causal relationship patients and biopsy of the goitre confirmed Hashimoto’s thyroiditis in 2 cases [Kawai et al., 1991bl. Two pa- between HTLV-I infection and Hashimoto’s thyroiditis tients (cases 10 & 12) were hypothyroid, and one (case in a certain proportion of the patients. To the best of our knowledge, this has not previously been reported. 11)euthyroid. Viral infection may lead to a n autoimmune disorder HTLV-I antibody titres of the 3 cases of thyroiditis ranged from 1:8,192 to 1:131,072 (mean, 1:51,883), by several mechanisms [Mims, 1986; Schattner and which was higher (P < 0.05)than the mean of 1:11,605in Rager-Zisman, 19901; 1) modulation of the host imthe 6 patients with HAM/TSP without Hashimoto’s mune system, 2) harmful effects of reactive viral antithyroiditis. Western blot analysis demonstrated p19, bodies, including molecular mimicry and immune complex formation, 3) modification of the antigenicity of a p24, gp46, and p53 in all these 3 cases (Fig. 1). The clinical and laboratory profiles of the 12 patients host cell protein(s1, or 4) induction of class I1 antigen with Hashimoto’s thyroiditis with positive HTLV-I an- expression by interferons and other cytokines such as
Kawai et al.
140
Case No. 1* 2 3* 4*
5 6* 7 8 9* 10 11
12*
Age (yr) 61 54 76 71 64 67 67 24 76 47 60 65
TABLE I. Summary of Patients With Hashimoto’s Thyroiditis and HTLV-I Antibody? MCAb TGAb TGAb(R1A) Thyroid Sex Diagnosis Struma (titres) (titres) (U/ml) function 67.0
