Paired measurements of quantitative hepatitis B virus DNA in saliva and serum of chronic hepatitis B patients:: implications for saliva as infectious agent

Background: After intensive source and contact tracing 20% of acute Hepatitis B virus (HBV) infections remain unexplained. Saliva may be an unexpected vehicle of HBV DNA transmission. Objective: To further explore this hypothesis we evaluated the quantitative levels of HBV DNA in saliva and compared these with the HBV DNA levels measured in serum. Study design: Serum and saliva were collected from 27 chronic HBV patients attending our outpatient clinic. Results: There were 16 men and 11 women; 15 patients were HBeAg positive, anti-HBe negative and 11 patients were HBeAg negative, anti-HBe positive. One patient was HBeAg and anti-HBe negative. Samples of serum and saliva were collected on the same day. All saliva specimens were clear on inspection. HBV DNA in serum was measured by the Digene Hybrid Capture II microplate assay (Digene Diagnostics), the HBV Monitor assay (Roche Diagnostics) as well as an in-house developed HBV DNA TaqMan assay. The HBV DNA TaqMan assay was used for the quantitative measurement of HBV DNA in saliva. Median HBV DNA levels in serum were 2.10 x 10(5) geq/ml and ranged from 373 genome equivalents per ml (geq/ml) to 4.13 x 10(9) geq/ml; median HBV DNA levels in saliva were 2.27 x 10(4) geq/ml and ranged from 373 geq/ml to 9.25 x 10(6) geq/ml. A clear correlation was shown between HBV DNA in serum and saliva; log HBV DNA in saliva = 1.01 + 0.56 x (log HBV DNA in serum). Conclusions: this is the first report of precise quantitative measurements of HBV DNA levels in saliva and the relationship with HBV DNA levels in serum. Our findings show that saliva is a source of HBV DNA. This finding may have implications in selected patients for the infectivity of saliva and offer further insight in the routes of transmission of HBV infection. (C) 2003 Elsevier B.V. All rights reserved.