High prevalence of hepatitis delta virus infection detectable by enzyme immunoassay among apparently healthy individuals in Mongolia

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Abstract
A previous study revealed a high prevalence of hepatitis B surface antigen (HBsAg) and hepatitis delta virus (HDV) RNA among 249 apparently healthy individuals (mean ± standard deviation age, 48.4 ± 13.9 years; 126 males and 123 females) in Ulaanbaatar, Mongolia. To investigate further the prevalence of HDV infection there, the same serum samples obtained from the cohort were tested for the presence of immunoglobulin G (IgG) class antibody to HDV (anti‐HDV) by a newly developed enzyme‐linked immunosorbent assay using recombinant hepatitis delta antigen protein expressed in the pupae of silkworm as the antigen probe. Anti‐HDV was detected in 42 persons (16.9%), among whom 22 (52.4%) were positive for HBsAg and 20 (47.6%) had detectable HDV RNA. Among 170 persons with anti‐HBc in the absence of HBsAg, 20 (11.8%) tested positive for anti‐HDV, and 1 of the 20 subjects was positive for HDV RNA. Of note, none of 55 anti‐HBc‐negative persons had anti‐HDV, supporting the specificity of the anti‐HDV assay. The optical density (OD) value of anti‐HDV was significantly higher among HDV RNA‐positive subjects (n = 21) than among HDV RNA‐negative subjects (n = 21) (2.513 ± 0.514 vs. 0.836 ± 0.550, P < 0.0001). The present study confirmed the extremely high prevalence of HDV infection in Mongolia, and identified a person who was positive for both anti‐HDV and HDV RNA despite negativity for HBsAg and HBV DNA probably due to viral interference. The anti‐HDV assay may be useful for further epidemiological studies on HDV infection in larger cohorts in urban and rural areas of Mongolia, where elucidation of the transmission route of HDV is required urgently. J. Med. Virol. 76:333–340, 2005.