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-titre IgM anti-HD (greater than 1/10,000) 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.(ABSTRACT TRUNCATED AT 250 WORDS)

An indirect ELISA and an inhibition ELISA were developed for the detection of cytomegalovirus (CMV)-specific immunoglobulin G (IgG) and CMV-specific total immunoglobulin, respectively. Both assays were more specific than the complement fixation (CF) test, and titres of positive sera were 660 times higher by IgG ELISA and 6 times higher by inhibition ELISA than titres by the CF test. Titres by IgG ELISA were reliably determined using the absorbance obtained at a single serum dilution of 1/1,000 in conjunction with a standard graph. Both ELISAs compared favourably with each other in sensitivity and specificity in determining CMV immune status. The inhibition ELISA, in particular, provides a simple and reliable method of screening sera, which requires no control antigen or predilution of sera. It should prove useful for large-scale screening procedures, such as blood donor testing.

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