The role of pre-core hepatitis B virus mutants on the long-term outcome of chronic hepatitis B virus hepatitis. A longitudinal study

A thermostable DNA polymerase was used in an in vitro DNA amplification procedure, the polymerase chain reaction. The enzyme, isolated from Thermus aquaticus, greatly simplifies the procedure and, by enabling the amplification reaction to be performed at higher temperatures, significantly improves the specificity, yield, sensitivity, and length of products that can be amplified. Single-copy genomic sequences were amplified by a factor of more than 10 million with very high specificity, and DNA segments up to 2000 base pairs were readily amplified. In addition, the method was used to amplify and detect a target DNA molecule present only once in a sample of 10(5) cells.

The complete nucleotide sequence of hepatitis B virus genome (subtype ayw) cloned in Escherichia coli has been determined using the Maxam and Gilbert method and the dideoxynucleotide method. This sequence is 3,182 nucleotides long. Location of the nonsense codons shows that the coding capacity of the L chain is larger than the coding capacity of the S chain. Eight open regions, able to code for polypeptide chains larger than 100 amino acids, have been located. Region 6, which is the largest, covers more than 80% of the genome. The gene S which codes for polypeptide I of the Hbs Ag and was previously located between coordinates 95.1 and 73.6 is contained in region 7.

Twenty-five patients with chronic type B hepatitis documented by liver biopsy were followed for 1 to 6 years with serial measurements of aminotransferase levels, hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg) and antibody (anti-HBe), and hepatitis B virus DNA polymerase. Initially, all were positive for HBsAg and HBeAg and had elevations in serum aminotransferases. In follow-up, only one lost HBsAg reactivity. In 13, however, elevated aminotransferase levels spontaneously fell to normal and have remained normal. These 13 also had a seroconversion from HBeAg to anti-HBe, and all became negative for serum DNA polymerase. Most had a fall in HBsAg titer. This seroconversion occurred concurrently with or several months before the fall in aminotransferase levels. In contrast, the 12 persons who remained HBeAg positive continued to have elevated aminotransferase levels. All 10 of these patients who were initially positive for DNA polymerase remained positive. These data suggest that many patients with chronic type B hepatitis eventually have a spontaneous remission in clinical and biochemical evidence of active disease, usually heralded or accompanied by the disappearance of HBeAg and DNA polymerase.