Masaaki Mizui

Red Cross, Washington, Washington, D.C., United States

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Publications (14)28.93 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Aim:  To follow up blood donors found with hepatitis C virus (HCV) infection, to improve the outcome by antiviral treatments. Methods:  Between 1991 and 2001, 3377 of the 1 925 860 donors (0.18%) were found to have HCV infection at the Hiroshima Red Cross Blood Center in Japan. Of them, 987 were able to be followed regularly over 9-18 years until 2009, and received antiviral treatments as required. Results:  At the start, chronic hepatitis was diagnosed in 541 (54.8%), cirrhosis in five (0.5%) and hepatocellular carcinoma (HCC) in one (0.1%), whereas the remaining 439 (44.5%) had persistently normal aminotransferase levels (PNAL). Hospital visits were terminated voluntarily in 24.3% within the first year, 46.8% by 10 years and 50.9% by 17 years. Liver disease improved in 178 (18.0%), remained stable in 606 (61.4%) and aggravated in 170 (17.2%). Of the 541 donors with chronic hepatitis, HCC developed in 28 (5.2%) and cirrhosis in 11 (2.0%), whereas HCV infection was cleared in 107 (19.8%) by antiviral treatments. In addition, HCV infection resolved in 54 of the 439 donors (12.3%) with PNAL after they had developed chronic hepatitis and received treatments. In donors with chronic hepatitis, the cumulative incidence of HCC was 4.1% at 10 years. By multivariate analysis, age and diagnosis of chronic hepatitis at the entry were found to be independent risk factors for the development of HCC. Conclusion:  Individuals with undiagnosed HCV infection need to be identified and receive medical care. They have to be motivated to merit from this health-care program.
    Hepatology Research 01/2012; 42(7):637-647. · 2.07 Impact Factor
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    ABSTRACT: Objective: To estimate total numbers of undiagnosed carriers of hepatitis C virus (HCV) and hepatitis B virus (HBV) in Japan. Methods: Area- and age-specific prevalence of HCV as well as HBV was determined in the first-time blood donors [20-39 years (n = 2,429,364)] and examinees of periodical health check-ups [40-74 years (6,204,968 for HCV and 6,228,967 for HBV)] in Japan. Prevalence in adolescents [5-19 years (79,256 for HCV and 68,792 for HBV)] was determined in a single prefecture, and that of HCV in the elderly (≥ 75 years) was estimated by the exponential model. HBV infection was determined by the detection of hepatitis B surface antigen, and HCV infection by either the algorithm or assuming persistent infection in 70% of the individuals with antibody to HCV. Results: Of the total population of 127,285,653 in 2005, 807,903 (95% CI 679,886-974,292) were estimated to be infected with HCV at a carrier rate of 0.63%, and 903,145 (837,189-969,572) with HBV at that of 0.71%. Conclusion: Accurate estimation of undiagnosed HCV and HBV carriers in the general population would help to predict the future burden of liver disease, and take appropriate measures for improving healthcare.
    Intervirology 03/2011; 54(4):185-95. · 1.89 Impact Factor
  • Journal of Hepatology - J HEPATOL. 01/2011; 54.
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    ABSTRACT: Infection with hepatitis C virus (HCV) persisted for longer than 29 weeks in 2 chimpanzees after they had been inoculated with it experimentally. One of them (C-210) received short-term subcutaneous interferon-α (IFN-α) 6 million units (MU) daily for 7 days at week 29. He cleared HCV RNA from the serum and remained negative for it during 25 weeks after the withdrawal of IFN. The other (C-224) did not respond to 2 courses of a short-term IFN monotherapy at weeks 20 and 23. Twelve weeks thereafter, he received IFN-α 3 MU daily for 2 weeks and then 3 times a week for 14 weeks combined with oral ribavirin 600 mg daily during 16 weeks. HCV RNA disappeared from the serum and stayed negative until the last follow-up 24 weeks after the completion of combination therapy.
    Intervirology 01/2011; 54(4):229-32. · 1.89 Impact Factor
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    ABSTRACT: Studies of hepatitis B virus (HBV) infection in non-human primates such as chimpanzees are no longer possible due to ethical considerations and the endangered status of chimpanzees since April 2007 in Japan. A human hepatocyte transplanted chimeric mouse was used to characterize HBV infectivity in serial stages of acute infection. Chimeric mice were inoculated intravenously with serum samples obtained from an experimentally infected chimpanzee with HBV. Sera from the pre-acute phases (i.e., rump-up viremia prior to anti-HBc) and late acute phases (i.e., declining phase of HBsAg and anti-HBcAb positive) were collected from the chimpanzees 57 and 244 days after inoculation. These sera contained 2.6 x 10(6) and 2.8 x 10(6) copies/ml of HBV DNA, respectively. Three chimeric mice inoculated intravenously with 100 microl of pre-acute serum (equivalent to 10(0) copy of HBV DNA) developed an HBV infection. The three chimeric mice that received 100 microl of pre-acute serum (equivalent to 10(1) copies of HBV DNA), developed high levels of serum HBV DNA. None of the three chimeric mice inoculated with 100 microl of 1:10(4) dilution (equivalent to 10(1) copies of HBV DNA) of late-acute serum was infected, while only one of three chimeric mice inoculated with 100 microl of 1:10(3) dilution (equivalent to 10(2) copies of HBV DNA) of late-acute serum developed an HBV infection. Based on these results, chimeric mice can be used as animal models for the study of HBV infectivity, pathogenesis and control. The results show that pre-acute phase HBV serum is about 100-times more infectious than late acute phase serum.
    Journal of Medical Virology 01/2009; 80(12):2064-8. · 2.37 Impact Factor
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    ABSTRACT: In planning optimal hepatitis B virus (HBV) blood screening strategies, the minimum infectious dose and early dynamics of HBV need to be determined for defining the window period for HBV DNA as well as for hepatitis B surface antigen (HBsAg). Pairs of chimpanzees were inoculated with preacute-phase inocula containing HBV of genotype A or genotype C to determine the minimum infectious dose, and two pairs of chimps infected with the lowest infectious dose of genotypes A and C were followed for HBV markers. The minimum 50 percent chimpanzee infectious dose (CID50) was estimated to be approximately 10 copies for genotype A and for genotype C. In the two chimps inoculated with the lowest infectious dose, the HBV DNA window was 55 to 76 days for genotype A and 35 to 50 days for genotype C, respectively. The HBsAg window was 69 to 97 days for genotype A and 50 to 64 days for genotype C, respectively. The doubling times of HBV DNA were 3.4 days (95% confidence interval [CI], 2.6-4.9 days) for genotype A and 1.9 days (95% CI, 1.6-2.3 days) for genotype C. When comparing the replication velocity of HBV DNA between the two genotypes, the doubling time of genotype C was significantly shorter than that of HBV genotype A (p < 0.01). Although the CID50 of approximately 10 copies was similar for the two HBV genotypes, the doubling time and pre-HBV nucleic acid amplification technology (<100 copies/mL) window period in chimps infected with the lowest infectious dose seemed to be shorter for genotype C than for genotype A.
    Transfusion 02/2008; 48(2):286-94. · 3.53 Impact Factor
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    ABSTRACT: Although prevalence rates of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections have kept decreasing in blood donors, there is little information on incidence rates of these hepatitis viruses in Japan. During 10 years from June 1994 through April 2004, 418,269 inhabitants of Hiroshima, Japan, donated blood (1,409,465 units in total). They were screened for serum markers of HBV and HCV infections, and individuals who developed de novo infections were identified. Infection with HBV occurred at a rate of 2.78 per 100,000 person-years (95% confidence interval: 1.78-4.14/100,000 person-years) and that with HCV at a rate of 1.86 per 100,000 person-years (95% confidence interval: 1.06-3.01/100,000 person-years). Residual risks of transmission by transfusions, based on the relationship risk [window period (estimated at 0.15 and 0.03 years in chimpanzees inoculated with minimum infectious doses for HBV and HCV, respectively) x incidence], were 1/243,000 for HBV and 1/1,960,000 for HCV infections. At present, incidence rates of HBV and HCV infections are extremely low in Japan.
    Intervirology 02/2008; 51(1):33-41. · 1.89 Impact Factor
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    ABSTRACT: Aim: To portray liver disease and project outcomes in carriers of hepatitis C virus (HCV) in the general population.Methods: Liver disease was evaluated in 1019 individuals who were found with HCV infection at blood donation, and they were followed for 5–10 years with or without receiving interferon (IFN).Results: At baseline, chronic hepatitis was detected in 529 (51.9%) HCV carriers and more frequently in men than in women (62.6% [299/478]vs 42.5% [230/541], P < 0.01); cirrhosis was diagnosed in five (0.5% [three men included]) and hepatocellular carcinoma (HCC) in one (0.1% [man]). Of the carriers who were followed for 5 years or longer, loss of HCV-RNA from serum was achieved in 61 (31.0%) of the 197 treated with interferon (IFN) and only one of the 211 (0.5%) without IFN (P < 0.0001). HCC developed in 14 carriers including six ofthe 211 (2.8%) without IFN and eight of the 197 (4.1%) with IFN (six non-responders included). Follow ups of the 949 carriers identified age (P < 0.002), male gender (P < 0.01) and cirrhosis at the baseline (P < 0.0001) as factors contributing to the development of HCC. Cumulative incidence rates of HCC during 10 years among carriers found with chronic hepatitis increased in parallel with the age at the baseline.Conclusion: Identification of HCV carriers in the general population and treating those indicated with IFN would help decrease the development of HCC and lift its medical, as well as economic, burdens off society.
    Hepatology Research 07/2007; 37(12):994 - 1001. · 2.07 Impact Factor
  • Journal of Clinical Virology 06/2006; 36 Suppl 1:S56-64. · 3.29 Impact Factor
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    ABSTRACT: Two chimpanzees were inoculated with hepatitis C virus (HCV) and followed on a daily basis for 12 days. HCV RNA became detectable in their sera on day 5 by polymerase chain reaction with the detection limit of 10(2) copies/ml. Based on an exponential growth observed until 8 or 9 days after inoculation in their sera, the doubling time of HCV in the circulation was estimated at 6.3-8.6 h and log time (time required to grow 10-fold) at 31.3- 42.9 h. The exact doubling time of HCV determined in them would help plan an efficient strategy for screening out blood donors in the window period of infection between the exposure and the development of antibody to HCV in serum.
    Intervirology 01/2005; 48(2-3):120-3. · 1.89 Impact Factor
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    ABSTRACT: To determine the copy number of hepatitis C virus (HCV) RNA, determined by nucleic acid amplification test (NAT) for screening blood units in Japan, that can transmit infection to chimpanzees. Fresh-frozen plasma with markers of HCV infection, as well as inocula pedigreed from 1 of them, were evaluated for the infectious activity in chimpanzees. One unit each (273-282 ml) of fresh-frozen plasma from 2 blood donors or a pool from 13 donors to make a unit, which contained high-titered antibody to HCV but without HCV RNA detectable by NAT, did not infect any of 3 chimpanzees. Two chimpanzees were infected, however, when they were inoculated with 1 ml of serum from a blood donor in the 'window period' of HCV infection and containing 7.0 x 10(6) copies/ml of HCV RNA. The preacute phase serum from 1 of them harvested 7 weeks after the inoculation was titrated in 2 chimpanzees, and an inoculum containing approximately 2 x 10(1) copies of HCV RNA could transmit infection to both of them. Approximately 20 copies of HCV can transmit infection to recipients, which needs to be taken into consideration in planning the screening of blood units for HCV RNA by NAT. Although the sensitivity of present NAT could be improved further, there would be a limit of it in detecting a low-level HCV RNA in the window period of donors with the infectious capacity in recipients.
    Intervirology 02/2004; 47(1):57-64. · 1.89 Impact Factor
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    ABSTRACT: Carriers of hepatitis B virus (HBV) and hepatitis C virus (HCV) in Japan were estimated on a national basis. Sera from the first-time blood donors aged 16-64 years in eight jurisdictions of the Japanese Red Cross Blood Center during 1995-2000 were tested for hepatitis B surface antigen (HBsAg) and antibody to HCV (anti-HCV). Viremia with HCV was estimated to be present in 70% of donors with anti-HCV. HBsAg was detected in 22,018 of 3,485,648 (0.63%) blood donors including 12,990 of 1,780,149 (0.73%) men and 9,028 of 1,705,499 (0.53%) women, and anti-HCV in 17,010 (0.49%) including 8,504 (0.48%) men and 8,506 (0.50%) women. Multiplying the carrier rate by the population registered in the Census 2000, the total HBV carriers aged 15-65 years were estimated at 967,753 (95% confidence interval 806,760-1,128,745), of whom 571,210 (479,267-663,152) were men and 396,543 (327,494-465,593) were women. Likewise, the total HCV carriers were estimated at 884,954 (95% confidence interval 725,082-1,044,826), of whom 464,363 (377,927-550,799) were men and 420,591 (347,156-494,027) were women. Estimated numbers of HBV and HCV carriers would help plan to prevent the development of hepatocellular carcinoma in Japan.
    Intervirology 02/2004; 47(1):32-40. · 1.89 Impact Factor
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    ABSTRACT: The Markov model was introduced to simulate natural histories of hepatitis C virus (HCV) infection in men and women. The data set was constructed on 942 HCV carriers who were examined at least once a year without receiving antiviral therapies. Based on 2,251 patient-year data, the probabilities of transition between any two of the four clinical states, i.e., asymptomatic carrier state, chronic hepatitis, liver cirrhosis and hepatocellular carcinoma in 1 year were calculated. Hepatocellular carcinoma was defined as the absorbing state from where no transitions occur. Probability matrices thus obtained on six each subsets of HCV infection (asymptomatic carrier state, chronic hepatitis and liver cirrhosis in men and women) in their forties, fifties, and sixties, were used to simulate long-term outcomes of HCV infection. Male asymptomatic carriers aged 40 years were expected to retain the asymptomatic carrier state in 2.6%, evolve into chronic hepatitis in 48.4%, liver cirrhosis in 14.6% and hepatocellular carcinoma in 34.4% after 30 years when they reached 70 years of age, in contrast to 1.9%, 45.3%, 32.8% and 20.0%, respectively, of female asymptomatic carriers. Likewise, male patients with chronic hepatitis aged 40 years were expected to remain with chronic hepatitis in 43.8%, evolve into liver cirrhosis in 15.0% and hepatocellular carcinoma in 41.1%, contrasting with 38.9%, 32.7% and 22.0%, respectively, of female patients during 30 years. The Markov model could simulate the outcomes of 153 HCV carriers identified among blood donors after 5 years. The Markov simulation would help in assessing the long-term outcome of HCV infection and making decisions in the management of HCV carriers toward prevention of hepatocellular carcinoma.
    Journal of Medical Virology 08/2003; 70(3):378-86. · 2.37 Impact Factor
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    ABSTRACT: The role of resolved hepatitis B virus (HBV) infection in promoting hepatocellular carcinoma (HCC) in patients infected with hepatitis C virus (HCV) in Japan was evaluated by epidemiological surveys. Antibody to hepatitis B core (anti-HBc) was determined in age-matched blood donors, and the frequency was compared with that in patients with HCV-associated HCC in Japan. Anti-HBc was detected significantly more frequently in the blood donors with than without antibody to HCV (anti-HCV; 76/135 or 56.3% vs. 65/255 or 25.5%, p < 0.001). In the patients with HCV-associated HCC, anti-HBc was detected in 109 of 202 (54.0%), which was comparable to the frequency in anti-HCV-positive blood donors (56.3%). Among the blood donors with anti-HCV, the prevalence of anti-HBc was no different between those with and without HCV RNA in serum (40/77 or 51.9% vs. 36/58 or 62.1%). The individuals of an age with high cancer frequency (>or=40 years) in Japan would have been exposed to HBV frequently (>50%), whether or not they have developed HCV-associated HCC. Despite repeated assertions in the literature, no epidemiological evidence was obtained for a role of past HBV infection in hepatocarcinogenesis in patients infected with HCV in Japan.
    Intervirology 01/2003; 46(3):171-6. · 1.89 Impact Factor

Publication Stats

234 Citations
28.93 Total Impact Points

Institutions

  • 2012
    • Red Cross
      Washington, Washington, D.C., United States
  • 2003–2011
    • Japanese Red Cross
      Edo, Tōkyō, Japan
  • 2008–2009
    • Hiroshima University
      • Department of Epidemiology
      Hiroshima-shi, Hiroshima-ken, Japan