Immune complex transfer enzyme immunoassay for (anti‐human t‐cell leukemia virus type i) igg in serum using a synthetic peptide, cys‐gag p19(100–130), as antigen

An immune complex transfer enzyme immunoassay for (anti‐human T‐cell leukemia virus type I) IgG (anti‐HTLV‐I IgG) in serum using a synthetic peptide, cys‐gag p19(100–130), is described. Anti‐HTLV‐IIgG in test serum, which had been incubated with excess of inactive β‐D‐galactosidase to eliminate interference by anti‐β‐D‐galactosidase antibodies, was reacted simultaneously with 2,4‐dinitrophenyl bovine serum albumin‐cys‐gag p19(100–130) conjugate and cys‐gag p19(100–130)‐β‐D‐galactosidase conjugate. The complex formed of the three components was trapped onto polystyrene balls coated with affinity‐purified (anti‐2,4‐dinitrophenyl group) IgG. After washing to eliminate nonspecific IgG in the test serum and excess of the β‐D‐galactosidase conjugate, the complex was eluted from the polystyrene balls with εN‐2,4‐dinitrophenyl‐L‐lysine and transferred to polystyrene balls coated with affinity‐purified (anti‐human IgG γ‐chain) IgG. β‐D‐Galactosidase activity bound to the (anti‐human IgG γ‐chain) IgG‐coated polystyrene balls was assayed by fluorometry. This assay was 100‐fold more sensitive than the conventional enyme immunoassay, in which a cys‐ gag p19(100–130)‐bovine serum albumin‐coated polystyrene ball was incubated with test serum and, after washing, with (anti‐human IgG γ‐chain) Fab'‐peroxidase conjugate. The degree of inhibition by preincubation of test sera with excess of cys‐ gag p19(100–130) in combination with an appropriate cut‐off value for the fluorescence intensity of bound β‐D‐galactosidase activity discriminated almost all seropositive samples from seronegative ones.