Sensitive enzyme immunoassay (immune complex transfer enzyme immunoassay) for (anti‐human T‐cell leukemia virus type I) IgG in serum using recombinant gag p24(14–214) as antigen

A sensitive enzyme immunoassay (immune complex transfer enzyme immunoassay) for (anti‐human T‐cell leukemia virus type 1) IgG (anti‐HTLV‐l IgG) in serum using recombinant gag p24 (14–214) of HTLV‐l is described. The recombinant gag p24(14–214) is soluble in the absence of detergents and allows the use of enzymes other than horseradish peroxidase as a lbel in teh assays. The usefulness of recombinant gag p24(14–214) was examined with 305 sera characterized by other methods including gelatin particle agglutination, enzyme‐linked immunosorbent assay (ELISA) using HTLV‐l, and Western blotting. This Assay was more sensitive than other methods using HTLV‐l as antigen. The specificity could be tested by preincubation of test serum with excess of the recombinant protein. Most of negative and positive sera were discriminated. However, some results appeared to be false‐positive or false‐negative, and recombinant gag p24(14–214) was suggested to be useful, when used with other recombinant proteins and/or peptides, for improving the reliability of serodiagnosis by separately demonstrating antibodies against as many different epitopes of HTLV‐l as possible. Anti‐HTLV‐l IgG 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‐recombinant gag p24(14–214) conjugate and recombinant gag p24(14–214)‐β‐D‐galactosidase conjugate. The complex formed consisting of the three components was trapped onto polystyrene balls coated with affinity‐purified (anti‐2, 4‐dinintrophenyl 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‐purifiedc (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.