The serology of delta hepatitis and the detection of IgM anti-HD by EIA using serum derived delta antigen

Abstract

A sensitive and specific capture assay for IgM antibody to hepatitis D virus (HDV) was developed employing serum-derived delta antigen (HDAg). In a retrospective and prospective study of an outbreak of hepatitis B (HB), 135 hepatitis B surface antigen (HBsAg) positive drug-abusers with acute hepatitis and 18 HBsAg carriers, attending various hospitals and clinics in Dublin, were found to be infected with HDV. Serological follow-up was available from 24 of those with acute hepatitis allowing a comparison of the duration and level of IgM anti-HD with the more commonly used markers, HDAg and anti-delta (anti-HD), and an assessment of the usefulness of each. HDV and HB serology was grossly altered by human immunodeficiency virus (HIV) in two patients, with severe clinical manifestation in one. All 135 patients with HDV co-infection had delta antigenaemia. In co-infections with optimum sampling times, the mean duration of delta antigenaemia was 21 days. IgM anti-HD was always found between HDAg and sero-conversion to anti-delta and was the only ‘window’ marker present in five cases. The mean duration of IgM anti-HD was four weeks (optimum at 2.8 weeks) and was of moderate or low titre and occurred simultaneously with HDAg in 78%. In HDV-infected HBsAg carriers, high-litre IgM anti-HD ( > 1 10000 ) persisted for the duration of the study and is a useful indicator of chronic HDV infection. IgM anti-HD was not found in 202 random blood donors nor in 205 patients with non-B hepatitis or other disorders. Total (IgG) anti-HD persisted in all patients (except the two reactivations) at titres of less than 1 1000 in co-infections and greater than 1 5000 in carriers, for the duration of follow-up. We conclude that HDAg is singly the best marker of HDV co-infection and. where only late specimens are available. IgM anti-HD is also useful. IgM anti-HD will also distinguish between chronic HDV infection and previous exposure.