Although hepatitis B virus (HBV) infection is endemic in Southeast Asia, molecular epidemiological data on HBV circulating in some countries are limited. The aims of this study were to evaluate the seroprevalence of HBV and its genetic variability among migrant workers from Cambodia, Laos, and Myanmar in Thailand. Sera collected from 1,119 Cambodian, 787 Laotian, and 1,103 Myanmarese workers were tested for HBsAg. HBV DNA was amplified and the pre-S/S region was sequenced for genotyping and genetic mutation analysis. HBsAg was detected in 282 (9.4%). The prevalence of HBsAg among migrant workers from Cambodia, Laos, and Myanmar was 10.8%, 6.9%, and 9.7%, respectively. Of 224 subjects positive for HBV DNA, 86% were classified as genotype C (99% were sub-genotype C1) and 11.6% were genotype B (30.8%, 34.6%, and 30.8% were sub-genotypes B2, B3, and B4, respectively). Various point mutations in the "a" determinant region were detected in approximately 18% of these samples, of which Ile126Ser/Asn was the most frequent variant. Sequencing analysis showed that 19.1% of samples had pre-S mutations, with pre-S2 deletion as the most common mutant (7.7%) followed by pre-S2 start codon mutation (3.8%) and both pre-S2 deletion and start codon mutation (3.3%). High prevalence of HBV infection (approximately 7-11%) was found among migrant workers from Cambodia, Laos, and Myanmar, which may reflect the current seroprevalence in their respective countries. The data also demonstrated that HBV sub-genotype C1 was the predominant strain and various mutations of HBV occurring naturally were not uncommon among these populations.

This study demonstrated that HBV genotype/subtype C/adr and B/adw were the predominant strains circulating in Thailand. The "a" determinant variants seemed to be uncommon, and might not be attributed to vaccine-induced mutation.

Biliary atresia (BA) is a neonatal obliterative cholangiopathy of unknown etiology. Despite the Kasai procedure, hepatic fibrosis and portal hypertension (PH) still occur. Interleukin-8 (IL-8) is an important mediator of inflammation and immune response in human disease. The objective of this study was to investigate the potential role of IL-8 in the pathogenesis of the progressive, sclerosing, inflammatory process and fibrosis in BA. A total of 60 pediatric patients with BA and 15 healthy children were evaluated. The mean ages of BA patients and controls were 6.3 +/- 0.6 and 6.7 +/- 1.1 years, respectively. The patients were classified into two groups according to their clinical outcomes: patients with jaundice (total bilirubin +/- 25.5 micromol/l) and patients without jaundice (total bilirubin < 25.5 micromol/l). The IL-8 levels in serum samples were determined by commercially available enzyme-linked immunosorbent assay. Serum IL-8 levels were higher in the BA patients than in healthy children (236.2 +/- 60.1 vs. 34.5 +/- 12.1 pg/ml, P < 0.001). Patients with jaundice had lower levels of albumin but had greater levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and gamma glutamyl transpeptidase compared with patients without jaundice. Serum IL-8 levels in the jaundice group were significantly higher than in those without jaundice (516.5 +/- 130.0 vs. 49.3 +/- 10.4 pg/ml, P < 0.0005). Furthermore, patients with PH had higher IL-8 levels than those without PH (378.1 +/- 102.2 vs. 106.6 +/- 48.4 pg/ml, P < 0.005). In the jaundice-free group, IL-8 levels were elevated in patients with PH compared with those without PH (79.0 +/- 17.4 vs. 19.7 +/- 5.8 pg/ml, P < 0.005). The present study demonstrated elevation of serum IL-8 levels in children with BA. Serum IL-8 levels were also higher in patients with jaundice compared with patients without jaundice. These findings suggest that IL-8 may play a significant role in the pathogenesis of BA.

Perinatal transmission of hepatitis B virus (HBV) has been controlled incompletely despite adequate immunoprophylaxis in infants. The aim of this study was to characterize virological factors of HBV associated with vaccine failure in Thailand. Sera of 14 infected infants (13 HBeAg-positive and one HBeAg-negative) with vaccine failure and their respective mothers (group M1) were tested quantitatively for HBV DNA by real-time PCR, HBV genotypes and mutations were characterized by direct sequencing. Sera collected from 15 HBeAg-positive (group M2) and 15 HBeAg-negative (group M3) mothers whose infants had been vaccinated successfully served as controls. The results showed that group M1 and group M2 mothers had equal titers of HBV DNA but higher titers than group M3. All infected infants and their respective mothers had the same HBeAg status and HBV genotypes. DNA analysis in a pair of HBeAg-negative infant and mother revealed that both were infected with an HBV precore mutant (G1896A). Escape mutants in the "a" determinant region (residues 144 and 145) were detected in two (14%) infected infants. The prevalence of BCP mutations/deletions in groups M2 and M3 was higher significantly than in group M1 (P = 0.022 and P < 0.001, respectively). In conclusion, instead of the HBeAg status, a high titer of HBV DNA in mothers was the major contributor to perinatal transmission of HBV. Escape mutants might be associated with vaccine failure in some infants. BCP mutations/deletions in mothers might contribute to the prevention of mother-to-infant transmission of HBV.

Hepatitis A virus (HAV) can infect not only humans but also several other nonhuman primates. This study has been conducted to evaluate the comprehensive anti-HAV seroprevalence in captive nonhuman primate populations in Thailand. The prevalence of antibodies against HAV in 96 captive nonhuman primates of 11 species was evaluated by competitive enzyme immunoassay (EIA). HAV antibodies were found in 64.7% (11/17) of macaques, 85.7% (6/7) of langurs, 28.4% (10/35) of gibbons, and 94.6% (35/37) of orangutans. However, anti-HAV IgM was not found in any sera. These results indicate that the majority of captive nonhuman primates in Thailand were exposed to HAV. It is possible that some of the animals were infected prior to capture.