HBsAg seroclearance in chronic hepatitis B in the Chinese: virological, histological, and clinical aspects.

Few studies have examined Chinese patients with chronic hepatitis B who exhibit hepatitis B surface antigen (HBsAg) seroclearance. We comprehensively studied the biochemical, virological, histological, and clinical aspects of 92 patients with HBsAg seroclearance (median follow-up, 126 months). Ninety-two HBsAg-positive controls matched for age, sex, and duration of follow-up were also recruited. Liver biochemistry, serum hepatitis B virus (HBV) DNA levels, and development of clinical complications were monitored. Intrahepatic total and covalently closed circular (ccc) HBV DNA were measured quantitatively in 16 patients. HBV genotype was determined in 30 patients. The mean age at HBsAg seroclearance was 48.8 (+ 13.81) years. There was a significant improvement in serum alanine aminotransferase levels after HBsAg seroclearance (p<0.0001). Patients with genotype B had a higher chance of HBsAg seroclearance than those with genotype C (P =.014). Ninety-eight percent of patients had undetectable serum HBV DNA. Thirty-seven percent of patients had low titer of intrahepatic HBV DNA, mainly in the form of cccDNA (71%-100%). All 14 patients with liver biopsies had near normal histology. There was no difference in the risk of development of hepatocellular carcinoma (HCC) between patients with and without HBsAg seroclearance. However, the mean age of HBsAg seroclearance was significantly older in patients with HCC than in patients without HCC (P =.016). In conclusion, patients with HBsAg seroclearance had favorable biochemical, virological, and histological parameters. Intrahepatic HBV DNA level was low and predominantly in the form of cccDNA. However, HCC could still develop, particularly in patients with cirrhosis who had HBsAg seroclearance at an older age.

Genotyping single nucleotide polymorphisms directly from genomic DNA by invasive cleavage reaction on microspheres.

Here we report proof-of-principle for a microsphere-based genotyping assay that detects single nucleotide polymorphisms (SNPs) directly from human genomic DNA samples. This assay is based on a structure-specific cleavage reaction that achieves single base discrimination with a 5'-nuclease which recognizes a tripartite substrate formed upon hybridization of target DNA with probe and upstream oligonucleotides. The assay is simple with two easy steps: a cleavage reaction, which generates fluorescent signal on microsphere surfaces, followed by flow cytometry analysis of the microspheres. Genomic DNA samples were genotyped for the SNP in the Apolipoprotein E gene at amino acid position 158. The assay successfully scored wild type, heterozygous and homozygous mutants. To our knowledge, this is the first report of a solid-support assay for detection of SNPs directly from genomic DNA without PCR amplification of the target.

Structure-specific DNA cleavage on surfaces.

The structure-specific invasive cleavage reaction is a useful means for sensitive and specific detection of single nucleotide polymorphisms, or SNPs, directly from genomic DNA without a need for prior target amplification. A new approach integrating this invasive cleavage assay and surface DNA array technology has been developed for potentially large-scale SNP scoring in a parallel format. Two surface invasive cleavage reaction strategies were designed and implemented for a model SNP system in codon 158 of the human ApoE gene. The upstream oligonucleotide, which is required for the invasive cleavage reaction, is either co-immobilized on the surface along with the probe oligonucleotide or alternatively added in solution. The ability of this approach to unambiguously discriminate a single base difference was demonstrated using PCR-amplified human genomic DNA. A theoretical model relating the surface fluorescence intensity to the progress of the invasive cleavage reaction was developed and agreed well with experimental results.

A surface invasive cleavage assay for highly parallel SNP analysis.

The structure-specific invasive cleavage of single-stranded DNA by 5' nucleases is a useful means for sensitive detection of single-nucleotide polymorphisms or SNPs. The solution-phase invasive cleavage reaction has sufficient sensitivity for direct detection of as few as 600 target molecules with no prior target amplification. One approach to the parallelization of SNP analysis is to adapt the invasive cleavage reaction to an addressed array format. Two surface invasive cleavage reaction strategies were designed and tested using the polymorphic site in codon 158 of the human ApoE gene as a model system, with a synthetic oligonucleotide as target. The upstream oligonucleotide, which is required for the invasive cleavage reaction, was either added in solution (strategy 1), or co-immobilized on the surface along with the probe oligonucleotide (strategy 2). Both strategies showed target-concentration and time-dependent amplification of signal. Parameters that govern the rate of the surface-invasive cleavage reactions are discussed.