DETECTION OF HEPATITIS-B VIRUS-DNA IN HEPATITIS-B SURFACE ANTIGEN-NEGATIVE SERUM BY POLYMERASE CHAIN-REACTION - EVALUATION OF DIFFERENT PRIMER PAIRS AND CONDITIONS

The presence of hepatitis B virus (HBV) DNA was investigated by polyme rase chain reaction (PCR) in the serum of twenty Brazilian blood donor s. All sera were negative for hepatitis B surface antigen (HBsAg), 17 of them presented antibodies to the hepatitis B core antigen (anti-HBc ) as the unique serological marker of HBV infection, and 3 were positi ve for antibodies to HBsAg (anti-HBs) and anti-HBc. PCR assays were ca rried out using different pairs of oligonucleotides designed from cons erved sequences of C, pre-S and S regions of the HBV genome. First, al l oligonucleotide pairs were tested in PCR using plasmids carrying HBV genome from ayw or adw strains as templates. One-round PCR assays wer e able to detect 100 - 25,000 molecules of plasmid DNA, depending on t he oligonucleotide pair, while semi-nested PCR assays detected 10 - 10 00 molecules. The frequency of HBV DNA-positive results with HBsAg(-) sera varied from 0% to 50% depending upon the PCR assay. The results i ndicated that a number of both isolated anti-HBc and anti-HBs(+), anti -HBc(+) samples contained HBV DNA at a very low concentration, neighbo ring the limit of detection.