Production of a recombinant human T-cell leukemia virus type-I trans-activator (tax1) antigen and its utilization for generation of monoclonal antibodies against various epitopes on the tax1 antigen.

A 42-kDa recombinant protein, PX141, consisting of the trans-activator protein encoded by human T-cell leukemia virus (HTLV-1) (tax1 antigen) and the amino-terminal fusion peptide of 12 amino acid residues of the alpha-peptide encoded by the plasmid pUC19 was produced. In order to investigate the immunogenicity of the tax1 antigen, mice were immunized with the purified PX141 and 4 anti-tax1 monoclonal antibodies (MAbs) designated TAXY-1, TAXY-6, TAXY-7 and TAXY-8 were generated, and their reactivity was characterized along with another anti-tax1 MAb, Lt-4. Immunoblot assays showed that all the MAbs reacted with the PX141, the native tax1 antigen expressed in various HTLV-1-infected cell lines and the gp68 of MT-2 cells expressing the tax1 amino acids 94-353. Immunoblot assays using recombinant, truncated tax1 antigens, XD59 (expressing amino acids 180-338) and XD128 (expressing amino acids 1-47 and 286-353) showed that: (1) TAXY-1 and Lt-4 did not react with either antigen; (2) TAXY-6 and TAXY-8 reacted with only XD128: and (3) TAXY-7 reacted with both. In addition, TAXY-1, but not the other MAbs, reacted with a putative tax antigen of an STLV-I-infected cell line, designated RfM26-I. Competitive binding assays showed that TAXY-6 and TAXY-8 did not compete against each other. Sera from HTLV-I-infected humans interfered with the binding of all of these anti-tax1 MAbs. These results indicate that the tax1 antigen and the PX141 express at least 5 distinct epitopes recognized by human and mouse antibodies.