Detection of the immune modulatory region within the HTLV FP.

<p>(<i>A</i>) Sequences of shorter peptides derived from the full length HTLV FP. (<i>B</i>) MOG_35-55–antigen specific T-cells were activated by APCs in the presence of HTLV FP derived peptides at 10μM and proliferative responses were assessed as described above. The HTLV FP and HTLV FP_5-13 inhibit T-cell proliferation with higher potency than HTLV FP_9-22 and HTLV FP_14-22. The data is presented as mean inhibition of proliferation. n = 12. (<i>C</i>) MOG_35-55–antigen specific T cells were activated by either (<i>i</i>) irradiated MOG_35-55 presenting APCs (black), (<i>ii</i>) antibodies against CD3 and CD28 (white), or (<i>iii</i>) PMA and Ionomycin (gray) in the presence of HTLV FP_5-13 and HIV FP_5-13 at 10μM. Proliferative responses were assessed as described above. The HTLV FP inhibits T-cell proliferation induced either through the TCR or downstream from the TCR with equal potencies. The data is presented as mean inhibition of proliferation. n = 12. (<i>D</i>) Secondary structures of HTLV FP derived peptides as revealed by CD spectroscopy. CD spectra were measured at 25μM in 5mM HEPES buffer containing 1% lyso-phosphatidylcholine (LPC). The HTLV FP and HTLV FP_5-13 exhibit a typical α-helical curve while the HTLV FP_9-22 and HTLV FP_14-22 exhibit a typical random coil. (<i>E</i>) MOG_35-55–antigen specific T-cells were activated by APCs in the presence of HTLV FP_5-13 D/L enantiomers at 10μM and proliferative responses were assessed as described above. Both HTLV FP_5-13 enantiomers inhibit T-cells proliferation with equal potencies. The data is presented as mean inhibition of proliferation. n = 12. One-way ANOVA was used for statistical analysis. *<i>P</i><0.05;<i>**P</i><0.01;***<i>P</i><0.001.