Neutralizing activity and antibody reactivity toward immunogenic regions of the human T cell leukemia virus type I surface glycoprotein in sera of infected patients with different clinical states.

The induction of specific neutralizing antibodies is an important part of vaccine strategy against human T cell leukemia virus type I (HTLV-I). A recently developed reporter gene induction assay was used to detect and quantify neutralizing antibodies in sera of HTLV-I-infected patients with different clinical states: Most sera (73/89) displayed an inhibitory activity. Neutralizing antibodies were more frequently detected in sera of patients with tropical spastic paraparesis/HTLV-associated myelopathy (TSP/HAM) or sicca syndrome (SS) (100%) than in sera of patients with adult T cell leukemia (ATL; 50%) or of asymptomatic carriers (AS; 83%). The mean titers in the different groups were significantly different (ATL < AS < TSP/HAM and SS). The antibody reactivity detected by the reporter gene inhibition assay was significantly related to the recognition of the neutralizable immunodominant domain (aa 175-199) of the surface envelope glycoprotein, indicating the importance of this region for potential vaccines.

Effects of bolesatine on a cell line from the SP2/O thymic lymphosarcoma.

Bolesatine, a toxic protein isolated from Boletus satanas Lenz inhibits in vitro protein synthesis in a concentration-dependent manner in a cell line from a radiation-induced thymic lymphosarcoma (SP2/O) with a 50% inhibitory concentration (IC50) of 9.5 nM (0.6 microgram/ml). In vivo, an i.p. single injection of bolesatine, corresponding to 1/6 and 1/10 of 24-h 50% lethal dose, in Balb/c mice having ascitic tumour induced by the i.p. preinjection of SP2/O cells allows a remission of 50% and 30%, respectively. Treated mice survived 120 days after the treatment, i.e. 90 days after the death of control animals.

Identification of HTLV-I- or HTLV-II-producing cells by cocultivation with BHK-21 cells stably transfected with a LTR-lacZ gene construct.

The Syrian Hamster kidney cell line (BHK-21) was stably transfected with a plasmid vector containing the lacZ bacterial gene under the control of a HTLV-I-LTR promoter. In these cells termed pA18G-BHK-21, this lacZ construct is inducible by the tax protein produced by a tax expression vector. It was also shown that beta-galactosidase synthesis was detected within 48 h after cocultivation of pA18G-BHK-21 cells with HTLV-I (HUT-102, MT2, C91/PL, 2060) or HTLV-II (MoT strain) -producing cells. The number of positive cells was directly related to the number of HTLV-I or -II-infected cells seeded. In addition, the LTR transactivation observed in coculture with HTLV-I-infected cells was specifically inhibited by sera containing antibodies directed against HTLV-I proteins, but not, or only weakly, by sera containing HTLV-II antibodies. Conversely, beta-galactosidase expression induced by HTLV-II-infected cells was inhibited by sera of HTLV-II-infected individuals, but not, or only weakly, by HTLV-I-positive sera. Irrespective of the inducer cell, sera from uninfected people did not inhibit LTR-driven expression of the lacZ gene in pA18G-BHK-21 cells cocultivated with HTLV-producing cells. This assay may thus be employed profitably for the detection and quantification of both HTLV-producing cells and HTLV-specific antibodies.