δ Infection in asymptomatic carriers of hepatitis B surface antigen: Low prevalence of δ activity and effective suppression of hepatitis B virus replication

We examined the prevalence of serum anti‐δ antibody among 769 intravenous drug abusers in Taiwan. δ infection was found extremely common in the HBsAg‐positive carriers with drug abuse, because 128 (85%) of 151 carriers were positive for anti‐δ. However, most of antibody titers were low (<1:5,000). By molecular hybridization, δ RNA genomes were detectable in only five (4%) of 128 asymptomatic carriers positive for anti‐δ. The results suggested that most of them had previous, instead of ongoing, δ infection. We also studied the serum markers reflecting hepatitis B virus replication in these carriers and a control group. Hepatitis B e antigen was positive in only 12 (10%) of 115 anti‐δ positive carriers in contrast to 22 (23%) of 95 age‐ and sex‐matched HBsAg‐positive, anti‐δ negative volunteers donating blood (p < 0.025). Furthermore, in contrast to the close association between HBeAg and hepatitis B virus DNA generally present in HBsAg carriers (concordance in this series: 79%), among the 12 HBeAg‐positive subjects of the δ infected group, only two, or 17%, had serum hepatitis B virus DNA (p < 0.003). Such suppressing effects did not require a simultaneous presence of the δ agent, as shown by the lack of δ RNA genomes in the serum by sensitive assay. We conclude that although δ superinfection is common in the asymptomatic HBsAg carriers with intravenous drug abuse in the nonendemic area of Taiwan, continuous δ activities are uncommon in them. In addition, the previous δ infection probably exerts effective suppression on the hepatitis B virus replication in these HBsAg carriers.