Susceptibility to hepatitis A virus infection among chronic liver disease patients and healthy blood donors in Thailand.

Due to improvements in socio-economic and sanitation conditions, Thailand has undergone a change from hyperendemicity to intermediate endemicity for hepatitis A virus infection, leaving a large part of the adult population without immunity. At the same time, the country is still highly endemic for hepatitis B and especially in the northeast, hepatitis C virus infection both of which when acquired during infancy or early childhood exhibit a strong tendency to turn towards chronic liver disease, although in particular with hepatitis B virus the asymptomatic carrier state is also rather common. As no cross-immunity exists between any of these viruses, double or triple infections do occur, a situation where previously acquired immunity to HAV becomes crucial as double infections have been shown to take a more severe or even fatal course. In the present study, we investigated 820 HBV- and/or HCV-related chronic liver disease (CLD) patients and 195 blood donors, both groups divided by 10-year age intervals, for the prevalence of anti-HAV. The results showed the same age dependence of immunity for all groups tested as can be expected for an area of intermediate endemicity, in that approximately 50% of those between 21 and 30 years of age had acquired anti-HAV. These findings indicate the immune response to HAV infection not to be altered by chronic infection with either HBV or HCV. Hence, vaccination against HAV should be considered, particularly in anti-HAV-negative patients with CLD.

alpha 1-antitrypsin phenotype PiMZ, a risk factor for liver cirrhosis but not for liver cancers in Thailand.

The risk of developing liver cirrhosis, hepatoma (HCC) and bile duct carcinoma (BDC) have been associated with homozygous alpha 1-antitrypsin (AT) deficiency especially linked to the Z allele. While the association between liver cancers and AT deficiency remains debatable, the risk of adult AT deficiency carriers to develop liver cirrhosis has not been assessed quantitatively. Liver cancers and liver diseases with subsequent liver cirrhosis are highly prevalent in tropical countries such as Thailand and heterozygous AT phenotypes are rather common in this country as well. The aim of this study was to assess the risk of developing liver cirrhosis, HCC and BDC by means of case-control studies with Thai patients and controls in connection with AT deficiency. For hepatitis, HCC and BDC to association with AT deficiency was detected. Carriers of PiMZ phenotype in Thailand have a high risk to develop liver cirrhosis (odds. ratio of 10.8, 95% confidence interval = 1.3-88.1). Patients with predisposing diseases should be screened for Pi phenotypes so that rigorous measures to combat the occurrence of liver cirrhosis can be implemented.

Antibodies to hepatitis C virus among patients with hepatocellular carcinoma and blood donors in Thailand.

HCC is the most cancer among Thai men. It is not known if HCV plays an oncogenic role in HCC in this country where HBV is endemic. Anti-HCV and HBsAg were assayed in 154 sera from HCC and 3,387 voluntary blood donors. The prevalence of anti-HCV in HCC (8.4%) was significantly higher than blood donors (1.38%). The prevalence of HBsAg in HCC (61%) was also significantly higher than blood donors (5.28%). The prevalence of anti-HCV in HCC was lower than that of Spain, Italy, Africa and Taiwan. Anti-HCV was found associated with a small portion of patients with HCC while HBV was found closely associated with the larger proportion of HCC. HCV in normal Thais was as common as those in southern Europe and HCV was found associated with HCC. However, HBV remains the major etiological factor of HCC in Thailand.

Diagnosis of opisthorchiasis by enzyme-linked immunosorbent assay using partially purified antigens.

Opisthorchis viverrini antigens were partially purified from adult worms collected from liver and extrahepatic biliary system of infected hamsters. Tegument fraction was obtained by chemical extraction, whereas other fractions were purified by Sephadex G-200 gel filtration chromatography. Five fractions of O. viverrini antigens were obtained, namely tegument extract, somatic extract, fraction 1 (P1), fraction 2 (P2) and fraction 3 (P3), respectively. The enzyme-linked immunosorbent assay technique was used to compare the reactivity of the five partially purified antigens. The sensitivity and specificity of all five antigens were compared by testing against the sera of 78 O. viverrini-infected individuals from O. viverrini endemic areas and 70 individuals from non-endemic areas infected with hookworm, Trichuris and Ascaris including 49 individuals with negative stool examination. The assays performed with tegument extract, somatic extract and P1 fraction were found to have 100% sensitivity, whereas the sensitivities of those with P2 and P3 were 96.1% and 83.3%, respectively. The tegument extract had the highest specificity as demonstrated by the lowest cross-reactivity with other parasites. Our results indicated that surface tegument is the most suitable antigen for use in immunological diagnosis of opisthorchiasis.

Enzyme-linked immunosorbent assay for detection of Opisthorchis viverrini infection.

Antibodies to O. viverrini in the sera of people from endemic and non-endemic areas were investigated using indirect ELISA technique. For the patients from the endemic area, 92.8% who passed eggs in the stool were found to be positive for O. viverrini antibody. In addition, 46.5% of the people who did not pass eggs in the stool were also found to have low titer of O. viverrini antibody. On the other hand only 2.4% of the people from the non-endemic area with other intestinal parasite infections were found to have O. viverrini antibody in their sera. It was concluded that positive reaction of O. viverrini antibody is not cause by cross-reaction with other parasites but low liter of antibody is probably due to low-level or past infection. There is a positive correlation between the titer of O. viverrini antibody and intensity of infection as indicated by number of eggs excreted per milligram of feces. Patients with a few O. viverrini eggs in feces, but biopsy-proved-cholangiocarcinoma had very high titer of antibody.