Re-evaluation of anti-HBc non-reactive serum samples from patients with persistent hepatitis B infection by immune precipitation with labelled HBV core antigen

BackgroundCore antigen (HBcAg) is the most immunogenic component of hepatitis B virus (HBV) and is believed to induce virtually always antibodies (anti-HBc) in immunocompetent infected persons. However, some chronically infected persons do not develop detectable anti-HBc.ObjectiveA more sensitive assay for anti-HBc was to be developed and used to re-evaluate a cohort of chronically HBV infected persons without detectable anti-HBc.Study designAmong 3309 serum samples which had been tested by commercially available (microparticle) enzyme immune assay (M/EIA) 34 samples from 22 patients were identified having reacted positive for HBsAg and negative for anti-HBc. Nine of these patients had immunosuppression or HIV coinfection, 13 patients were immunocompetent, 5 of them were perinatally infected.Anti-HBc was re-tested for in an immune precipitation (IP) assay using 32P-labelled recombinant HBcAg as reagent and anti-human-IgG-coated magnetic beads as separation system for immunecomplexes containing HBcAg. Specificity was controlled for by competition with unlabelled HBcAg.Results27 serum samples from the 22 patients could be retested. IP was positive in 7 MEIA negative sera, unspecific positive in 4 and negative in 16. Using 5 anti-HBe positive control sera, we found IP to be 1.8-fold (1.3–2.9) more sensitive than MEIA, but IP was 6.5-fold (5.8–7.4) more sensitive with 4 anti-HBe negative, anti-HBc positive sera.ConclusionIP allowed specific detection of anti-HBc in about 25% of MEIA negative chronic HBV patients. The majority of these seem to produce no or very little anti-HBc, however.