The association of antibodies against human T cell lymphotropic virus type I (HTLV-I) pX gene mutant products with HTLV-I-associated myelopathy/tropical spastic paraparesis

Antibodies specific for the products of the human T cell lymphotropic virus type 1 (HTLV-I) pX frame-shift mutants were studied by ELISA. The serum IgG antibodies to the synthetic peptide corresponding to one nucleotide insertion at position 7784 were significantly more common in patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients than in HTLV-I carriers who had neither HAM/TSP nor adult T cell leukemia (39% vs. 5%). The seropositivities to the other synthetic peptides, which corresponded to the one nucleotide deletion at position 7475 and the internal deletion of nt 7754-7819 and nt 7853-7936, were rare. A genetic study confirmed the presence of the responsible mutation of the pX gene in peripheral blood mononuclear cells and central nervous system tissue from HTLV-I-infected subjects with and without HAM/TSP. These results suggest that HTLV-I pX frame-shift mutants are expressed in vivo in HTLV-I carriers; they also induce antibodies, especially in those with HAM/TSP.