Increase of peripheral B lymphocytes committed to the production of monoreactive and high affinity antibodies to HTLV-1 in patients with HAM/TSP

We quantitated the frequency of B lymphocytes capable of producing antibodies to HTLV-1 in the peripheral blood from patients with HAM/TSP, non-HAM/TSP HTLV-1 carriers and seronegative healthy subjects. Epstein-Barr virus (EBV) was used as a polyclonal activator of B lymphocytes in a limiting dilution condition. We found that B lymphocytes committed to the production of monoreactive-IgG and -IgA antibodies to recombinant HTLV-1 (gag + env) hybrid protein were significantly increased in a number in patients with HAM/TSP as compared to non-HAM/TSP HTLV-1 carriers and seronegative healthy subjects. By transforming these B lymphocytes with EBV and fusing them with human-mouse heteromyeloma (F3B6), a stable hybridoma producing IgG monoclonal antibody (mAb) to HTLV-1 (gag + env) protein was generated from a patient with HAM/TSP. This mAb (IgG1, κ), designated F31.1, specifically bound to the amino acid residues from 235 to 254 of HTLV-1 envelope glycoproteins (gp46) with high affinity (K_d = 4.0 × 10^-9 mol/1). These data indicate that the antigen-driven process of B lymphocytes maturation by HTLV-1 antigens is markedly increased in patients with HAM/TSP.