Case-control study of factors associated with human T-cell leukemia virus type I infection in southern Miyazaki, Japan.

BACKGROUND: An unusual age- and sex-specific distribution and a remarkably restricted geographic seroprevalence characterize human T-cell leukemia virus type I (HTLV-I) infection. Although the transmission routes of HTLV-I are known, these seroepidemiologic features cannot be fully explained. PURPOSE: This study was designed to identify potential characteristics associated with HTLV-I infection in a highly endemic Japanese community. METHODS: We evaluated occupational, residential, dietary, and medical histories in a case-control study conducted in two neighboring villages in southeastern Miyazaki Prefecture. One hundred forty-four case subjects and 276 control subjects, frequency matched by age, sex, and village, were interviewed. Village-specific profiles of demographic determinants of HTLV-I seroprevalence were generated using multiple logistic regression. RESULTS: Although a different pattern of factors was found for each village, occupations of the subjects and their fathers were associated with HTLV-I infection in both communities--farming in village A and fishing and farming in village B. For village A, there was more than a twofold association both with residence in the township for 55 years or more and with living in a particular area within the village. In addition, case subjects were more likely to have a mother who was deceased (odds ratio = 1.7; 95% confidence interval = 0.96-2.9). CONCLUSIONS: HTLV-I infection is characterized by a high degree of microepidemicity in this population, with seroprevalence related to both sociologic and geographic determinants. Moreover, as carriers' mothers themselves have a higher probability of being HTLV-I positive, an increased mortality among those infected with the virus is suggested.

Determinants of HTLV-1 seroprevalence in Miyazaki Prefecture, Japan: a cross-sectional study.

To evaluate determinants of the prevalence of human T-cell leukemia virus type I (HTLV-I) antibody positivity in an endemic region, Miyazaki Prefecture, Japan, demographic and serologic data were collected on 7,055 individuals consecutively seen at Miyazaki City Health Promotion Center between September 1983 and December 1984. The overall HTLV-I seroprevalence was 8.5%; age and gender distributions of HTLV-1 antibody positivity were consistent with previous findings for endemic populations. The prefecture could be divided into two geographic areas based on seroprevalence: high prevalence (12.1%) in the southwest and medium prevalence (6.6%) for the rest of the prefecture. Current occupation in fishing, forestry, or livestock raising significantly correlated with HTLV-1 seropositivity [relative risk (RR) = 3.0, 2.5, 2.0, respectively]; farming also was associated but only in the medium prevalence region (RR = 1.3; p = 0.06). For a subset of 157 HTLV-I-positives and 175 negative controls screened for antibodies to the toxoplasmosis organisms, toxoplasma exposure was not significantly associated with HTLV-I infection. In this endemic Japanese population, both geographic and sociologic factors characterized the distribution of HTLV-I seroprevalence, reflecting transmission patterns and historical duration of the infection.

The minimum number of clones necessary to sequence in order to obtain the maximum information about hepatitis C virus quasispecies: a comparison of subjects with and without liver cancer.

Most studies of hepatitis C virus (HCV) quasispecies have reported the results of sequencing only three to five clones per sample. The possibility that sequencing so few clones might not provide a representative picture of the quasispecies present in a sample has never been evaluated. The present study was conducted to evaluate whether sequencing greater numbers of clones results in better information about the HCV quasispecies number and distribution, and to compare the HCV quasispecies in liver cancer cases and controls. RNA was extracted from serial serum samples from six subjects with HCV-associated liver cancer and 11 age- and sex-matched HCV-infected controls without liver cancer. The hypervariable region 1 (HVR1) of the HCV genome was amplified, cloned, and sequenced. For further studies of 12 serum samples from two liver cancer cases and two matched controls, successive groups of 10 additional clones were sequenced up to a total of 50 clones per serum sample. When only 10 clones were sequenced from each specimen, no consistent differences were seen between the number of HCV quasispecies in the six liver cancer cases and the 11 controls. However, sequencing 40 clones from each of 12 samples from two liver cancer cases and two controls revealed a greater number of quasispecies in liver cancer cases than in controls. Testing an additional 10 clones (50 clones per sample) did not significantly increase the number of quasispecies detected.

Usefulness of a new immuno-radiometric assay to detect hepatitis C core antigen in a community-based population.

A new immuno-radiometric assay (IRMA) to detect hepatitis C virus (HCV) core antigen (HCVcAg) has been developed. The aim of the present study was to investigate the sensitivity and specificity of this IRMA to measure HCV antigenemia, based on the detection of HCV RNA as the gold standard, and to assess the utility of the IRMA in a community-based population. Anti-HCV positive residents in a hyperendemic area of HCV infection in Japan were studied. Serum levels of HCVcAg were measured using IRMA, and the presence of HCV RNA was determined by a qualitative reverse transcription-polymerase chain reaction (RT-PCR) assay. The sensitivity and the specificity of the IRMA were 96.4 and 100%, respectively. The sensitivity of the IRMA was similar between serological HCV group I (HCV genotypes 1a and 1b) (97.6%) and group II (HCV genotypes 2a and 2b) (94.0%). There was a strong correlation between serum HCVcAg level and HCV-RNA measured by a quantitative RT-PCR (r = 0.832, P < 0.0001). There also was a very strong correlation of HCVcAg level between IRMA measurements performed on serum and those performed on plasma (r = 0.984, P < 0.0001). In conclusion, this new IRMA is useful for the detection of HCV core antigen in a community-based population.

Towards global control of liver cancer?

On a global scale, liver cancer is one of the leading causes of cancer morbidity and mortality. However, liver cancer rates vary substantially by country, with more than 80% of liver cancer cases occurring in the developing world. The major risk factors for hepatocellular carcinoma (HCC), the predominant histologic sub-type, are considered to be chronic infection with hepatitis B virus (HBV), hepatitis C virus (HCV) infection, exposure to aflatoxins, and excessive alcohol consumption; tobacco smoking and oral contraceptive use also may be associated with increased risk of HCC. This paper focuses on those risk factors that represent new targets for intervention, namely HBV and HCV infections and aflatoxin exposure. Childhood vaccination against HBV represents the greatest potential for reducing the liver cancer burden and could lead to the elimination of as much as 60% of all cases.

Liver cancer.

The trends in liver cancer incidence and mortality were investigated by gender in Japan, Norway, Singapore, Spain, Sweden, the UK and the USA. Cancer Incidence in Five Continents, Vols I-VI, were the principal source of the analysis of age specific incidence rates by sex; additional incidence information was obtained from the published data of the Connecticut Tumor Registry and the Surveillance, Epidemiology and End Results Program in the USA. Mortality rates were calculated using the World Health Organization database. The trends observed were generally weak. Increasing occurrence of primary liver cancer was noted in Japan and the Nordic countries, although the rates seemed to be stabilizing or even decreasing in the most recent data from Sweden. By contrast, decreasing trends were apparent in Spain and Singapore. Changes in the rates appeared to be more evident or somewhat stronger for males than for females. Some biological explanations were offered to account for these trends. However, the dominant determinants of the apparent changes in the incidence and mortality of primary liver cancer were felt to be related to classification and coding revisions as well as to variations over time in diagnostic and certification practices.

Infection with hepatitis B and C viruses, social class and cancer.

The hepatitis B and C viruses (HBV and HCV) are major etiological factors in the occurrence of hepatocellular carcinoma (HCC) worldwide, but most especially in developing countries where the majority of liver cancer cases can be found. In parallel with the geographic distribution of HCC, high levels of HBV endemicity are concentrated in the developing world. The association between chronic infection with HBV and low social class is quite strong; socioeconomic factors such as low educational attainment, lower social stratum, and crowded urban residence have been reported to predict higher HBV chronic carrier prevalence in both developed and developing countries. More importantly, the effect of poverty on HBV endemicity is clearly evident among younger age groups, and earlier chronic HBV infection seems to increase the risk of development of HCC. As assays for detecting HCV antibodies have only recently become available, the data on the relationship between HCV infection and socioeconomic status are much fewer. However, the limited number of studies that have investigated the seroepidemiology of HCV report an association between higher prevalence of antibodies to HCV and indicators of low social class. It would appear that the striking correlation between HCC and low socioeconomic status is largely related to the impact of poverty on the spread of HBV and probably HCV.

Evaluation of morbidity among human T lymphotropic virus type 1 carriers in Miyazaki, Japan.

Morbidity associated with human T lymphotropic virus type I (HTLV-I) infection was investigated in a Japanese population within an area in which HTLV-I infection is endemic. Of 1824 subjects enrolled in the Miyazaki Cohort Study between November 1984 and May 1991, 500 (27.4%) were seropositive for HTLV-I antibodies. As expected from previous studies, HTLV-I positively appeared to be associated with baseline history of anemia (adjusted odds ratio [OR]= 1.3; 95% confidence interval [CI]= 0.99-1.7) and kidney disease (OR=1.6; 95% CI= 0.91-2.9); a positive association also was noted for asthma in men (OR=3.4; 95% CI=1.2-9.8). Unanticipated findings included a relationship between HTLV-I infection and cardiac disease history (OR=1.4; 95% CI=0.94-2.2; HTLV-I carriers also were more likely to have an abnormal electrocardiogram at baseline (OR=1.5; 95% CI=1.2-1.9). Furthermore, an apparent protective effect for ulcers (OR=0.62; 95% CI=0.40-0.95) and diabetes (OR=0.49;95% CI=0.22-1.1) was observed. HTLV-I infection may modify the risk of specific disease outcomes by altering host immune function.

HCV infection and liver cancer mortality in a Japanese population with HTLV-I.

In a cohort study of human T-lymphotropic virus type I (HTLV-I) infection in Japan, 10 cases of liver cancer death occurred from 1984 through 1993. To analyze the role of hepatitis C virus (HCV), which has been associated with an increasing incidence of hepatocellular carcinoma (HCC) in Japan, a nested case-control study was performed. Five of the 10 liver cancer cases were positive for antibody to HTLV-I (anti-HTLV-I). The possible interaction between HCV and HTLV-I infections in the etiology of HCC was investigated, with each liver cancer case matched to 5 cohort controls by gender, age, serum sample date and anti-HTLV-I status. Using a matched analysis odds ratio (OR) were generated for the relationship between HCV serologic status and death liver cancer. Based on second-generation enzyme immunoassay with confirmation by recombinant immunoblot assay, 8 of 9 cases with adequate serum available (89%) and 9 of 50 (18%) controls were found to be positive for antibody to HCV (anti-HCV). Liver cancer death was highly associated with anti-HCV (matched OR = infinity; p < 0.001). Anti-HTLV-I seroprevalence was some what correlated with HCV infection. However, the high risk of liver cancer death observed for anti-HCV-positive Individuals in this population did not vary with respect to whether or not the subjects were also infected with HTLV-I.

Gender difference in skin reactivity to purified protein derivative among carriers of HTLV-I in Japan.

The incidence of malignancies due to oncogenic virus infections tends to be higher in men than in women. Gender-related differences in cell-mediated immunity, which plays a role in viral pathogenesis, may explain this observation. To explore this possibility in the context of HTLV-I infection, we examined skin reactivity to purified protein derivative (PPD) among 128 residents of an HTLV-I endemic area in Japan, who were born before 1921 and are assumed to have been exposed to M. tuberculosis bacilli. The odds ratio (OR) for reduced PPD reactivity (erythema <10 mm in diameter) was calculated by multiple logistic regression analysis. Men were significantly less likely than women to have reduced PPD reactivity among HTLV-I-negative individuals (26% versus 59%; p < .01); whereas this gender difference was not apparent among HTLV-I carriers (63% versus 62%; p = .87). HTLV-I positivity was strongly associated with reduced PPD reactivity in men, but not in women (odds ratio [OR], 7.3 versus 1.2; p = .05). Although this observation may be due, in part, to a longer average duration of HTLV-I infection in men compared with women, the finding also raises the possibility that men may be inherently more susceptible to loss of PPD reactivity by HTLV-I infection.

Sex-specific mortality from adult T-cell leukemia among carriers of human T-lymphotropic virus type I.

Perinatal infection with human T-lymphotropic virus type I (HTLV-I) is considered a risk factor for adult T-cell leukemia (ATL). Incidence of ATL in Japan is generally higher in males compared with females, perhaps partly due to an earlier average age of infection among males. We estimated sex-specific ATL mortality among perinatally-infected HTLV-I carriers in the prospective Miyazaki Cohort Study in Japan. Based on the approximated proportion of perinatally-infected carriers, the relative risk (RR) of ATL for males compared with females was calculated. Six ATL deaths (4 males, 2 females) occurred among the 550 HTLV-I carriers in the cohort during 13 years of follow-up. The overall ATL mortality was 190.5 (95% CI 51.9-487.7) per 10(5) person-years for males and 51.7 (6.3-186.8) per 10(5) person-years for females (age-standardized RR = 3.9, p=0.02). By approximating the number of persons who acquired infection perinatally, the estimated mortality among those perinatally-infected HTLV-I carriers was 209.1 (57.0-535.2) per 10(5) person-years for males and 60.9 (7.4-219.9) per 10(5) person-years for females (age-standardized RR = 3.7, p=0.02). The adjusted RR changed minimally from the unadjusted RR, suggesting that earlier age of infection alone is unlikely the explanation for the male predominance in ATL. Based on the small number of cases available for analysis, aspects of gender itself appear to play a role in the development of this malignancy.

The association between lactation and breast cancer in an international case-control study: a re-analysis by menopausal status.

In the large, hospital-based, international case-control study of breast cancer conducted by MacMahon and colleagues in the 1960s, no protective effect of lactation was observed. However, more recent reports have suggested that such an association may be limited to pre-menopausal women. Therefore, a re-analysis of the data from that original study was performed by menopausal status and with control for additional breast-cancer risk factors since identified. Overall, data from 4,671 parous pre-menopausal and 7,200 parous post-menopausal women were analyzed, from 7 different sites representing areas of high risk (Glamorgan, Wales; Boston, USA), moderate risk (Athens, Greece; Slovenia, ex-Yugoslavia; São Paolo, Brazil), and low risk (Tokyo, Japan; Taipei, Taiwan) of breast cancer. No significant effect of lactation was found for pre-menopausal or post-menopausal women from the high-, moderate-, or low-risk areas; the center-adjusted, combined odds ratio (OR) for having breast-fed was 1.05 (95% confidence interval, 0.86-1.29) among pre-menopausal and 1.04 (0.88-1.24) among post-menopausal women. Moreover, examination of cumulative duration of lactation did not support an inverse association between breast cancer and increased length of total breast-feeding. In conclusion, re-analysis of these data, by menopausal status and adjusting for age at first parity, age at menarche, age at menopause, body-mass index and years of schooling, did not reveal a protective effect of lactation or duration of lactation against breast-cancer occurrence among the pre-menopausal, parous women.

Diet and hepatocellular carcinoma: a case-control study in Greece.

We conducted a case-control study in Athens, Greece, to investigate the role of diet in the etiology of hepatocellular carcinoma (HCC). Subjects were 97 incident cases of HCC and 128 controls with no history of cancer admitted for minor ailments in three major hospitals. Information on diet was collected using a validated food frequency questionnaire, and infection with hepatitis virus B (HBV) or C (HCV) was assessed using third-generation assays. Data were modeled through multiple logistic regression. We found no evidence that vegetable intake may reduce the risk of HCC, as reported in earlier investigations. In a multivariate model, only consumption of milk and dairy products appeared to be inversely related to HCC risk (odds ratio = 0.70, 95% confidence interval = 0.49-1.01), but the association was not statistically significant and is likely to have been generated by the multiple comparisons undertaken overall. Our data do not support an association of specific food groups or particular nutrients with the risk of HCC, whether positive or negative for HBV and/or HCV.

Heterosexual transmission of human T cell leukemia/lymphoma virus type I among married couples in southwestern Japan: an initial report from the Miyazaki Cohort Study.

To identify factors that may modify the heterosexual transmission of human T cell leukemia/lymphoma virus type I (HTLV-I), 534 married couples enrolled in the Miyazaki Cohort Study between November 1984 and April 1989 were studied: 95 husband HTLV-I-seropositive (H+)/wife seropositive (W+), 33 H+/W-, 64 H-/W+, and 342 H-/W-. After 5 years of follow-up, seven seroconversions occurred and clustered significantly among serodiscordant pairs (relative risk [RR] = 41.2); the rate of transmission was 3.9 times higher if the carrier spouse was male (P = .19). Among H+/W- couples, husband's age > or = 60 years strongly predicted seroconversion in the wives (RR = 11.5). All 4 carrier husbands whose wives seroconverted had HTLV-I titers > or = 1:1024 (P = .04) and were anti-tax antibody positive (P = .06). In cross-sectional analysis, total parity also was independently associated with wife's serostatus but only length of marriage with husband's. Overall, sexual transmission of HTLV-I was primarily from older infected husbands to their wives, with husbands' viral status being an important factor.

Analysis of anti-Tax antibody of HTLV-I carriers in an endemic area in Japan.

Sera from 1197 adult residents in Miyazaki district, an area in Japan endemic for human T-cell leukemia virus type I (HTLV-I), were tested for anti-Tax antibody by the recombinant Tax (r-Tax) Western blot assay. Among HTLV-I-seropositive individuals, including 21.5% of 484 males and 28.6% of 713 females, the prevalence of anti-Tax antibody were 59.6% and 58.3% respectively, with no apparent difference in age. There was a significant 6-fold difference in the prevalence of anti-Tax among seropositive subjects with titer > or = 1:8192 (84.6%) compared with those with the lowest titer of 1:16 (14.3%), suggesting the increased production of antibodies to viral structural proteins in anti-Tax-positive individuals. Furthermore, among those anti-Tax-positive subjects, the intensity of serum reactivity to r-Tax protein in the high antibody titer (1:1024 or higher) group was significantly stronger than that in the lower antibody titer (1:512 or lower) group. We also found that 1.6% (14/889) of individuals without detectable levels of HTLV-I antibody had anti-Tax antibody. HTLV-I pro-viral DNA signals could not be detected in DNA sample from the lymphocytes of these individuals by the nested polymerase chain reaction method. Further evaluation is needed to clarify the significance of an anti-Tax-only status population in which HTLV-I is endemic.

Insulin-like growth factor 1 in hepatocellular carcinoma and metastatic liver cancer in men.

The insulin-like growth factor (IGF) axis has important autocrine, paracrine, and endocrine roles in the promotion of growth. Alterations of the IGF system have recently been implicated in the pathogenesis of several malignancies, but the relation to hepatocellular carcinoma (HCC) risk is unclear. To address this issue, we used an immunoradiometric assay to quantify IGF-1 levels in serum samples in a hospital-based, case-control study in Greece. The study subjects were all men and included 53 patients with HCC positive for hepatitis B and/or hepatitis C virus infections, 20 virus-negative HCC patients, 25 virus-negative patients with metastatic liver cancer (MLC), and 111 virus-negative control subjects. Data were analyzed by multiple linear regression, using IGF-1 as the dependent variable. The mean value of IGF-1 was 65.9 ng/ml among virus-positive HCC patients, 79.5 ng/ml among virus-negative HCC patients, 110.8 ng/ml among patients with MLC, and 174.7 ng/ml among hospital controls. After controlling for the degree of liver damage, as assessed by prothrombin time and serum albumin level, the reduction in IGF-1 level among HCC patients was found to be more than could be attributed to liver damage alone. This finding may have both diagnostic and pathophysiological implications.

Birth order, as a proxy for age at infection, in the etiology of hepatocellular carcinoma.

First-born and second-born children are exposed to common infections after enrollment at school, whereas later-born children are exposed to these infections earlier through their older siblings. We have evaluated whether birth order is a risk factor for hepatitis B virus (HBV)-related, hepatitis C virus (HCV)-related, and apparently virus-unrelated hepatocellular carcinoma (HCC) in a large case-control study that included 333 HCC cases and 632 controls. In comparison with controls who were carriers of hepatitis B surface antigen (HBsAg), HBsAg-positive HCC cases were more likely to have been later-born children (odds ratio per increase in birth order = 2.0; 95% confidence interval = 1.2-3.6). There was no such evidence for anti-HCV-positive cases compared with anti-HCV-positive controls or for virus-negative HCC cases compared with virus-negative controls. We conclude that early infection with HBV increases the risk of HBV carriers to develop HCC, over and beyond its role in facilitating the establishment of a carrier state.

Risk factors for adult T-cell leukemia among carriers of human T-lymphotropic virus type I.

The presence of circulating "flower cells" and a low prevalence of antibody to Tax regulatory protein of human T-lymphotropic virus type I (HTLV-I) are characteristics of adult T-cell leukemia (ATL). To examine the predictability of levels of HTLV-I antibodies and of flower cell-like abnormal lymphocytes (Ably) for the risk of ATL among asymptomatic HTLV-I carriers, we prospectively evaluated the levels of viral markers of five HTLV-I carriers who developed ATL and 38 age-, sex-, and screen-matched HTLV-I-positive controls in the Miyazaki Cohort Study. After accounting for matching factors, Ably level was slightly, but not significantly, higher among cases than among controls (P =.13). Anti-HTLV-I (odds ratio [OR] = 1.6 per twofold dilution; 95% confidence interval [CI] 0.94, 3.8) was associated with ATL diagnosis, but antibody to Tax regulatory protein (anti-Tax) was not (OR = 0.78; 95% CI 0.26, 1.7). Anti-Tax level was low for all ATL cases for up to 10 years preceding their diagnosis, independent of the level of anti-HTLV-I titer. HTLV-I carriers with a higher anti-HTLV-I titer and a lower anti-Tax reactivity may be at greatest risk of ATL.

Predictors of level of circulating abnormal lymphocytes among human T-lymphotropic virus type I carriers in Japan.

Human T-lymphotropic virus type I (HTLV-I) carriers often have abnormal lymphocytes (Ably) that resemble malignant cells of adult T-cell leukemia (ATL). To identify predictors of the level of Ably in a longitudinal study of asymptomatic HTLV-I carriers, we analyzed data from 215 subjects (67 men and 148 women) with multiple Ably measurements on blood smears. Ably+ (those having Ably > 0.6% of leukocytes counted on a blood smear at least once) was strongly associated with a high proviral load (OR 8.9; 95% CI 4.1, 19.5). The association among those defined as Ably++ (Ably > 0.6% at all screens or Ably > 1.6% at least once) was higher (19.7; 6.9, 56.1). Ably++ was also significantly associated with male gender (2.8; 1.0, 7.8). Multivariate analysis of Ably level indicates that men with a high proviral load, high anti-HTLV-I titer and low anti-Tax reactivity have the highest Ably level.