A simple ELISA procedure for HIV-1 based on the enzyme beta-lactamase.

The enzyme beta-lactamase (penicillin-amido-beta-lactam-hydrolase, EC 3.5.2.6.) has been shown to be suitable for use in ELISA procedures. The assay proposed requires a conjugate containing a beta-lactam-hydrolase as the enzymatic component, penicillin or one of its derivatives as substrate and an iodic complex (an iodine-starch or an iodine-polyvinylic alcohol complex) as the chromogenic component. Binding of conjugate molecules results in the transition of the iodic complex from dark blue to colourless. The transition is readily visualized without the aid of an EIA reader. The decolorization occurs specifically giving a clear-cut yes/no decision without a cut-off value. The rate of the colour transition strongly depends on the amount of bound conjugate. beta-lactamase-based ELISA techniques are of potential use in the immunological diagnosis of some virus diseases. The sensitivity and specificity of the assay were assessed on a panel of 670 negative and 141 positive HIV-1 sera, giving values of 100% and 99.85%, respectively.