Hepatitis B core antibody screening in a high prevalence group: comparison of three enzyme immunoassays using receiver operating characteristic analysis

Chronoamperometry-Based Redox Cycling for Application to Immunoassays

In this work, the chronoamperometry-based redox cycling of 3,3',5,5'-tetramethylbenzidine (TMB) was performed by using interdigitated electrode (IDE). The signal was obtained from two sequential chronoamperometric profiles: (1) with the generator at the oxidative potential of TMB and the collector at the reductive potential of TMB, and (2) with the generator at the reductive potential of TMB and the collector at the oxidative potential of TMB. The chronoamperometry-based redox cycling (dual mode) showed a sensitivity of 1.49 μA/OD, and the redox cycling efficiency was estimated to be 94% (n = 10). The sensitivities of conventional redox cycling with the same interdigitated electrode and chronoamperometry using a single working electrode (single mode) were estimated to be 0.67 μA/OD and 0.18 μA/OD, respectively. These results showed that the chronoamperometry-based redox cycling (dual mode) could be more effectively used to quantify the oxidized TMB than other amperometric methods. The chronoamperometry-based redox cycling (dual mode) was applied to immunoassays using a commercial ELISA kit for medical diagnosis of the human hepatitis B virus surface antigen (hHBsAg). Finally, the chronoamperometry-based redox cycling (dual mode) provided more than a 10-fold higher sensitivity than conventional chronoamperometry using a single working electrode (single mode) when applied to a commercial ELISA kit for medical diagnosis of hHBsAg.

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

BACKGROUND

Core 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.

OBJECTIVE

A 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 DESIGN

Among 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 (32)P-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.

RESULTS

27 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.

CONCLUSION

IP 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.