HUB1 is an autoantigen frequently eliciting humoral immune response in patients with adult T cell leukemia

The immunological screening of a cDNA phage expression library prepared fro m an adult T cell leukemia (ATL) cell line, ST1, was performed with IgG cla ss antibodies in the serum of an ATL patient by the SEREX method to analyze the repertoire of antigen molecules in ATL. Ten different cDNAs, 7 previou sly reported and 3 newly identified, were isolated. One of the identified c DNAs was homologous to the recently reported gene, HTLV-I USRE binding prot ein 1 (HUB 1) encoding a protein binding to a possible repressor element of the long terminal repeat of the human T lymphotropic virus type I (HTLV-I) . The obtained cDNA was expressed as a fusion protein with glutathione S-tr ansferase. HUB1 protein was prepared by subsequent treatment of the fusion protein with thrombin. Reactivity of IgG serum samples from ATL patients, a symptomatic HTLV-I carriers and normal donors against the purified protein was examined by Western blot analysis. Twenty-one out of 30 samples (70.0%) from ATL patients, 10/24 samples (41.7%) from HTLV-I carriers and 9/24 sam ples (37.5%) from healthy donors showed positive reactivity, indicating the autoantigenicity of HUB1. The development of ATL may be related to higher production of antibodies against HUB1.