[Inhibitory effects of HIV-1 gp41 fusion peptide on CD3 antibody activated regulatory T cells].

Aim: To investigate whether the HIV-1 gp41 fusion peptide (FP) could affect the regulatory T cell (Treg) function activated by CD3 antibody.

Methods: Murine CD4(+);CD25(+); Treg and CD4(+);CD25(-); effector T cells (Teff) were isolated from mice spleens by the immune magnetic beads. The splenocytes were treated with mitomycin C to obtain antigen presenting cells (APCs). CCK-8 assay and CFSE loading were employed to evaluate the effects of FP on the Treg inhibitory function via measuring Teff proliferation activated by CD3 antibody. In addition, IL-10 secretion of activated Treg was detected by ELISA. The distribution of FP and TCR on Treg surface was observed by laser scanning confocal microscope.

Results: Through the CCK-8 assay and flow cytometry, we found that Teff cells have significant proliferation stimulated by the CD3 antibodies. When Treg and Teff were co-cultured, the proliferation of Teff was significantly inhibited by Treg. When added with 25 μg/mL FP, the proliferation of Treg+Teff group and Teff group was not significantly affected, but when 5 μg/mL FP was added, the proliferation rate of Treg+Teff group was significantly lower than that of Teff group. IL-10 secretion was low when Treg were not activated, but it significantly increased by CD3 antibodies stimulation. When the concentration of FP was 25 μg/mL, IL-10 level significantly decreased, but 5 μg/mL FP did not significantly influence IL-10 secretion. Through the laser scanning confocal microscope, we found that T cell receptors (TCR) of non-activated Treg showed uniform distribution on the cell surface, and that FP and TCR had no common distribution. When Treg were stimulated by CD3 antibodies, the activated TCR formed half crescent, and FP and the activated TCR had common distribution on cell surface.

Conclusion: Treg inhibitory function is significantly inhibited by 25 μg/mL FP in vitro, but 5 μg/mL FP does not affect it. This may be due to the suppression of IL-10 secretion and the influence of the signaling cross-talk between APC and TCR.