NEW, ULTRASENSITIVE ENZYME-IMMUNOASSAY FOR DETECTING VACCINE-INDUCED AND DISEASE-INDUCED HEPATITIS-A VIRUS-SPECIFIC IMMUNOGLOBULIN-G IN SALIVA

Although detection of disease-induced hepatitis A virus (HAV)-specific antibodies in saliva has been successfully utilized in a few epidemio logical studies, available assays fail to detect lower salivary anti-H AV levels associated with vaccine-induced immunity. We present a new c apture enzyme immunoassay which employs a three-layer antibody recogni tion system. Evaluation of paired saliva-serum specimens from 1,025 in ternational travellers, 134 other volunteers, and 91 hepatitis A vacci ne recipients demonstrated 99.6% (95% confidence interval, 98.4 to 99. 9) specificity and 98.7% (95% confidence interval, 97.7 to 99.4) sensi tivity of this salivary assay in differentiating between immune and su sceptible individuals, compared with serum based methods. We conclude that this assay is sufficiently sensitive for reliable detection of bo th vaccine- and infection-induced HAV-specific immunoglobulin G in sal iva, even when corresponding anti-HAV levels in serum are very low (<1 IU/ml).