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-I IgG in test serum, which had been incubated with excess of inactive beta-D-galactosidase to eliminate interference by anti-beta-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)-beta-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 beta-D-galactosidase conjugate, the complex was eluted from the polystyrene balls with epsilon N-2,4-dinitrophenyl-L-lysine and transferred to polystyrene balls coated with affinity-purified (anti-human IgG gamma-chain) IgG. Beta-D-Galactosidase activity bound to the (anti-human IgG gamma-chain) IgG-coated polystyrene balls was assayed by fluorometry. This assay was 100-fold more sensitive than the conventional enzyme 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 gamma-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 beta-D-galactosidase activity discriminated almost all seropositive samples from seronegative ones.