ENZYME-LINKED IMMUNOSORBENT ASSAY OF NEOPTERIN USING PENICILLINASE AS LABEL

An enzyme-linked immunosorbent assay for neopterin using penicillinase as marker enzyme is reported here by polyclonal antibodies against neopterin conjugated to bovine serum albumin which were raised in rabbits. Immunoglobulin fractions were purified and coated on wells of microtiter plates. A chain heterology was introduced in neopterin derivative and conjugated to penicillinase. The assay is completed within 4 hr. The limit of detection was 10 pg of neopterin with a sensitivity range between 15-10000 pg. A low level of cross-reactivity with other pteridines was noted (biopterin <0.05%, pteroic acid <0.05%, and pterin <5%). The sensitivity and selectivity observed in the assay may be attributable to the selection of penicillinase as the enzyme marker and the element of conformation (heterology between the antigen-linked and enzyme-conjugated hapten).