A paper radioimmunosorbent test (PRIST) for the detection of larva-specific antibodies to toxocara canis in human sera

A paper radioimmunosorbent test (PRIST) was shown to be sensitive and reproducible when used with excretory/secretory antigen of Toxocara canis second stage larvae. Whatman No. 50 filter paper (5 mm discs) gave the most consistent and clear results with antigen at a concentration of 100 μg/ml, and could be stored for up to 3 weeks in vacuo at ?70°C. Antigen coated discs were incubated with test sera at 1 : 10 dilution for 3 h at room temperature (21°C), reacted with ¹²⁵I]anti-human IgG for 1 h and counts determined in a gamma counter. Sera from patients with fascioliasis, taeniasis, schistosomiasis, oxyuriasis, trichinellosis and ancyclostomiasis gave counts similar to cord serum controls. Sera from patients with ascariasis gave counts of up to twice as great as controls, but sera from patients with toxicariasis produced counts of 7,000–13,000, a 4–6-fold increase.