Core promoter and precore mutants of hepatitis B virus: prevalence and clinical relevance in chronic hepatitis patients.

The present study was conducted to determine prevalence and exact type, as well as nucleotide position of the precore/core mutations of hepatitis B virus found in Thai patients diagnosed with chronic hepatitis and/or cirrhosis in relation to the clinical parameters established with the respective patients. To that end, 24 HBeAg-positive and 56 HBeAg-negative individuals were selected at random from a cohort of altogether 256 chronic liver disease patients. DNA was extracted from their blood sera, amplified by polymerase chain reaction using semi-nested primers and subjected to direct sequencing. Clinically, the HBeAg-positive chronic hepatitis patients displayed significantly higher transaminase levels than those negative for HBeAg. Our results showed 2 of the 7 (28.6%) PCR-positive HBeAg-positive sera displaying double mutations in the core promoter region at position 1762/64. The nucleotide sequences obtained from the 24 PCR-positive HBeAg-negative sera revealed 18 (75%) mutations in the core promoter region (1762/64), and/or 7 (29.2%) mutations at position 1753, and/or 6 (25%) mutations of the start codon (1814), and/or 8 of (33.3%) nucleotide 1896 turning codon 28 into a stop codon and one sample (4.2%) displaying a deletion between nucleotides 1758-1772. It is suggested that the mutations observed have an impact on the DNA secondary structure in such a way that successful transcription of the HBeAg gene is rendered impossible. To what extent this mutation influences the severity of chronic liver disease remains to be elucidated.

Prevalence of core promotor and precore mutants of hepatitis B virus in thailand by RFLP and sequencing.

Hepatitis B virus has been known to frequently undergo mutations of its genome at various sites, mostly due to it employing a reverse transcriptase devoid of proofreading capacity in the course of its replication. The purpose of the present study has been to screen 257 HBsAg-positive chronic liver disease patients, more specifically 78 cases chosen at random out of those negative for HBeAg and 33 of the HBeAg-positive cases serving as controls for three discreet point mutations in the precore/core region of hepatitis B virus. To that end, HBV DNA extracted from sera was amplified by polymerase chain reaction (PCR) using semi-nested primers and subsequently subjected to restriction fragment length polymorphism (RFLP) analysis, 36 HBeAg-negative versus 30 HBeAg-positive sera, respectively, as well as to direct sequencing in some samples randomly selected to corroborate the RFLP results. Our results showed double mutations at positions 1762 and 1764 of the core promoter in between 25/36 (69.4%) and 19/25 (76%) of the sera tested, a missense mutation of the start codon in between 8/36 (22.2%), and 5/25 (20%) and a mutation turning codon 1896 into a stop codon in between 9/36 (25%) and 6/25 (24%) determined by RFLP and sequencing, respectively. These data indicate the double mutation at positions 1762 and 1764 to be the most prevalent among HBeAg-negative chronic hepatitis patients in Thailand whereas, in contrast to reports from other Asian countries, the mutation at nucleotide 1896 occurred in a mere 25%, while on the other hand the mutation abolishing the start of protein synthesis was observed to occur at a higher frequency than determined in several other geographical areas.

TT virus infection in intravenous drug users.

Our group has investigated 201 intravenous drug users for the presence of TTV DNA by means of polymerase chain reaction (PCR). The majority of the individuals tested were male, their age ranging from 16 to 63 years, and the duration of intravenous drug use from one to 40 years. TTV DNA was present in 62 of the 201 IVDUs (30.8%) with its prevalence on the ascent between the age groups below 20 and those between 21 and 30 years, as well as between the groups below 60 and between 60 to 120 months' duration of drug intake, respectively. When tested again after 9 months, nine IVDU (23.7%) were found TTV negative by PCR hinting at potential immunological clearance. Our control group comprised 200 healthy blood donors, 7% of whom were found to harbor TTV DNA in an age-dependent fashion, as observed with the IVDU. From the liver function tests performed we could not detect any statistically significant difference regarding ALT elevation observed in TTV-positive compared with TTV-negative individuals. To date, TTV does not appear to cause any serious liver disease in the majority of cases examined.

Clearance of hepatitis TT virus infection among thalassemia children and IVDU.

The novel transfusion transmissible hepatitis virus TTV first isolated by a group from Japan has predominantly been detected in members of groups at high risk for contracting blood borne viruses. Aside from elevated liver enzymes, the symptoms associated with its infection have been reported to range from asymptomatic to hepatic failure. The purpose of the present study was to determine if and to what extent the host's immune response is capable of clearing TTV infection. Hence, we extracted DNA from sera obtained from altogether 201 intravenous drug users (IVDU) and 80 thalassemia children--both groups at high risk of parenteral exposure--and performed PCR using semi-nested primers. Those positive for TTV DNA were once again subjected to PCR after approximately one year in order to determine how many still harbored the virus. Our results showed TTV DNA to be absent in merely 20.6% of the formerly positive IVDU, whereas it was still present in all the thalassemia children who could be tested for the second time. Based on the small sample size and the high-risk environment, these results ought to be interpreted with caution and definitely merit further investigation.

Alpha 1-antitrypsin phenotype of children with liver diseases in Thailand.

Alpha1-antitrypsin deficiency (PiZZ) constitutes not only the most common hereditary cause of liver diseases, but also of the most prevalent metabolic diseases in need of liver transplantation. It is a codominantly inherited disorder which predisposes to chronic liver disease, usually beginning in early infancy. The purpose of the present study has been to investigate alpha 1-antitrypsin phenotype in pediatric patients with various liver diseases. Phenotypic identification of alpha 1-antitrypsin variants has been carried out in 69 children with various liver diseases and 100 healthy controls using isoelectric focusing on polyacrylamide gel slabs. PIMM represents the most common phenotype detected in both groups (92% in the group with liver diseases and 88% in normal controls). We could detect PiZZ in only one healthy child but in none of those with liver diseases. Consequently alpha 1-antitrypsin deficiency does not appear to be a common cause for liver disease among children in Thailand. Further studies are necessary to elucidate the frequency of various alpha 1-antitrypsin variants and the clinical relevance with respect to liver diseases in Thailand.