A novel stop codon mutation within the hepatitis B surface gene is detected in the liver but not in the peripheral blood mononuclear cells of HIV- infected individuals with occult HBV infection

To characterize occult HBV infection (OHB) in different compartments of HIV+ individuals. This retrospective study involved 38 consecutive HIV+ patients; 24 HBsAg negative (HBV-) and 14 HBsAg positive (HBV+). OHB was assessed in serum samples, liver tissue (LT) and peripheral blood mononuclear cells (PBMC) by genomic amplification of the partial S, X and precore/core regions. HBV genomic analysis was inferred by direct sequencing of PCR products. The intracellular HBV- DNA was measured by a quantitative real- time PCR. HBV+ patients were used as a control for HBV replication and genomic profile. In HBV- patients, HBV- DNA was undetectable in all serum samples, while it was found positive in 7/24 (29%) LT in which genotype D prevailed (57%). HBV- DNA was found in 6/7 (86%) PBMC of occult- positive and none of occult- negative LT. Significantly lower HBV- DNA load was present in both compartments in OHB+ with respect to the HBV+ group (LT: P = 0.002; PBMC: P = 0.026). In the occult- positive cases, HBV replication was significantly higher in LT than in PBMC (P = 0.028). A hyper- mutated S gene in PBMC and a nucleotide mutation at position C695 in LT that produces a translational stop codon at amino acid 181 of the HBs gene characterized OHB. In this group of HIV+ persons, OHB is frequent and exhibits lower replication levels than chronic HBV in the different compartments examined. HBV- DNA detection in PBMC may offer a useful tool to identify OHB in serum- negative cases. The novel HBs gene stop codon found in LT could be responsible for reduced production leading to undetectability of HBsAg.