Resistance to Fas-mediated apoptosis of human T-cell lines expressing human T-lymphotropic virus type-2 (HTLV-2) Tax protein

The susceptibility to Fas-mediated apoptosis was evaluated in seven T-cell lines (two infected with HTLV-2, one with HTLV-1, and four HTLV-free) as well as in Jurkat cells transfected with a Tax-2 expressing vector. Fas-mediated apoptosis was significantly reduced in the HTLV-1- and HTLV-2-infected lines in comparison with the HTLV-free lines regardless of the surface expression of Fas antigen (which was no different in the infected and uninfected cells). Fas-mediated apoptosis was also significantly inhibited in Jurkat cells transfected with the Tax-2 expressing vector without any modification in Fas expression. There was significantly more antiapoptotic Bcl-x(L) mRNA and protein in the transfected than in the untransfected Jurkat T cells. In conclusion, our results suggest that HTLV-2 is capable of inhibiting Fas-mediated apoptosis by means of a mechanism involving the tax-2 gene and probably the expression of bcl-x(L) messenger and protein.

High prevalence of false-negative anti-HTLV type I/II enzyme-linked immunosorbent assay results in HIV type 1-positive patients

A high frequency of false-negative anti-HTLV-I/II ELISA results has been reported by several authors. To verify the possible underestimate of the prevalence of HTLV-II infection in subjects infected by HIV-1, we used the PCR to investigate the presence of HTLV DNA in peripheral blood mononuclear cells (PBMCs) collected from a group of 67 HIV-1-positive anti-HTLV-I/II ELISA-negative individuals; the study population included 31 patients with HIV-1-related peripheral neuropathy (PN), 15 with non-Hodgkin lymphoma (NHL), and 23 without PN or NHL. Two subjects had both PN and NHL. All of the patients who were positive at PCR were investigated for the presence of serum anti-HTLV-I/II antibodies by means of Western blot (WB). Eighteen (26.9%) of the 67 anti-HTLV-I/II ELISA-negative patients had HTLV DNA in their PBMCs and WB-detectable serum antibodies directed against one or more HTLV antigens. The individuals affected by predominantly sensory polyneuropathy (PSP) had a significantly higher prevalence of HTLV DNA than the others. All of the patients in whom HTLV-I/HTLV-II discrimination was successful had HTLV-II, with the exception of one patient who was infected by HTLV-I. The present study confirms the possibility of HTLV infection in the absence of ELISA-detectable serum anti-HTLV-I/II antibodies, especially in the particular setting of HIV-1-infected individuals. Moreover, the fact that the prevalence of HTLV DNA was significantly higher in the subjects affected by predominantly sensory polyneuropathy further supports the possibility of an association between HIV-1-related PSP and HTLV-II.