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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.

Objective: To study the effect of HIV-1 gp41 ectodomain (gp41-I90) on the cytoskeletal changes in human brain microvascular endothelial cells (HBMECs) induced by Cryptococcus neoformans., Methods: HBMECs were cultured on collagen-coated chamber slide or transwell to allow the formation of cell monolayers. After pre-treatment with gp41-I90 and infection with Cryptococcus neoformans, the HBMECs were examined for the expression of actin or filamin by immunofluorescence assay. HRP permeability of the HBMECs treated with gp41-I90 was detected by ELISA. Transcytosis of Cryptococcus neoformans through the gp41-I90-treated HBMECs was detected by direct counting from a hemocytometer., Results: gp41-I90 obviously enhanced the cytoskeletal changes of the HBMECs infected by Cryptococcus neoformans, causing curved and sparse filamentous arrangement of actin and filamin. gp41-I90 treatment also resulted in obviously increased HRP permeability of the cells and transcytosis of Cryptococcus neoformans., Conclusion: gp41- I90 enhances Cryptococcus neoformans binding to HBMECs, which is related to its effect in enhancing Cryptococcus neoformans-induced cytoskeletal changes of the cells.

HIV-1 fusion inhibitors are a new class of anti-HIV compounds, which block the entry of HIV into target cells through preventing the fusion between viral and cell plasma membrane and thus interrupt the initial steps of viral replication. T-20 (enfuvirtide), which has been clinically approved as the first fusion inhibitor of HIV-1 by U.S. FDA in 2003, can suppress replication of HIV variants with multi-drug resistance to reverse transcriptase and protease inhibitors. Peptides and small molecules display potent anti-HIV fusion activities by targeting gp41 thus inhibit its fusogenic function. In recent years, with the development of studies on the molecular mechanism of HIV membrane fusion process and the function of gp41, many new fusion inhibitors are found and some have been in advanced clinical trials. This review discusses recent progress in the development of HIV-1 fusion inhibitors targeting the gp41.