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To design and construct an HIV-1 subunit vaccine containing the N-terminal heptad repeat (NHR) domain N51 in gp41 of the HIV-1 CRF01_AE recombinant subtype in China and study its immunogenicity.Two pairs of primers were designed to amplify DNA fragment encoding N51Fd gene, which was then subcloned into pFUSE-hIgG1-Fc2 vector. The recombinant plasmid pFUSE/N51Fd was confirmed by DNA sequencing. Western blotting was used to measure the correct expression of the recombinant protein N51FdFc-AE. The N51FdFc-AE protein was used to immunize BALB/c mice, and the specific antibody response was measured by ELISA.A recombinant plasmid pFUSE/N51Fd was successfully constructed and the N51FdFc-AE recombinant protein was expressed effectively in 293T cells. The purified N51FdFc-AE recombinant protein (35 kD) was detected by Western blotting with rabbit anti-gp41 N/C peptide antibodies. The mouse anti-sera could specifically recognize the antigens derived from gp41 NHR. The titers of the specific antibodies were up to 1:102 400 with an average titer of 1:51 200.The recombinant N51FdFc-AE protein can effectively induce the gp41 NHR-specific immune responses in BALB/c mice and could be used as an immunogen for design of HIV-1 subunit vaccine.

To develop an objective bioassay for quantitative detection of HIV-induced cell-cell fusion for screening HIV entry inhibitors.HL2/3 cells expressing HIV envelope proteins gp120/gp41, Tat, and other HIV proteins were co-cultured with HeLa-CD4-LTR-beta-gal cells expressing CD4 receptor and HIV LTR triggered reporter gene beta-galactosidase. The enzyme activities of beta-galactosidase were detected by a chromogenic substrate, chlorophenol red-beta-galactopyranoside (CPRG). Specific HIV entry inhibitors were used to validate the established detecting method.No syncytium was formed by mixing HL2/3 and HeLa-CD4-LTR-beta-gal cells. However, the membrane could be fused and the Tat expressed by HL2/3 cells could bind to HIV LTR on HeLa-CD4-LTR-beta-gal cells and trigger the expression of beta-galactosidase. CPRG allowed quantitative and sensitive detection of the activity of beta-galactosidase. Further studies showed that HIV entry inhibitors could inhibit the activity of beta-galactosidase in a dose-dependent manner.We have developed a simple, cheap, objective and quantitative non-infectious cell-cell fusion bioassay that can be used to screen for anti-HIV agents targeting the virus entry from natural and synthetic compound libraries.

To observe the inhibitory effect of 1,2,6-Tri-O-galloyl-beta-D-glucopyranose (TGGP) from Balanophora japonica Makino on human immunodeficiency virus (HIV) entry into the host cells and explore the mechanisms.TGGP was purified from Balanophora japonica Makino by n-hexane and ethyl acetate extraction and column chromatography. The inhibitory activity of TGGP on HIV gp41 six-helix bundle formation was measured with ELISA, N-PAGE and SE-HPLC, and the inhibitory effect of TGGP on HIV envelope grlycoprotein-induced cell-cell fusion was detected using a non-infectious cell-based assay.TGGP inhibited HIV gp41 six-helix bundle formation, with an IC50 of 1.37-/+0.19 microg/ml as determined by ELISA, and this activity was further confirmed by N-PAGE and SE-HPLC. TGGP at 25 microg/ml significantly inhibited syncytium formation between the effector (CHO-WT) and the target (MT-2) cells.The HIV transmembrane subunit gp41 mediates the entry of HIV into the target cells. TGGP can inhibit HIV fusion and entry into the target cells by inhibiting the formation of gp41 six-helix bundles, suggesting the potential of TGGP as a microbicide to prevent sexual transmission of HIV.

To investigate the mechanism by which tannin inhibits HIV-1 entry into target cells.The inhibitory activity of tannin on HIV-1 replication and entry was detected by p24 production and HIV-1-mediated cell fusion, respectively. The inhibitory activity on the gp41 six-helix bundle formation was determined by an improved sandwich ELISA.Tannins from different sources showed potent inhibitory activity on HIV-1 replication, HIV-1-mediated cell fusion, and the gp41 six-helix bundle formation.Tannin inhibits HIV-1 entry into target cells by interfering with the gp41 six-helix bundle formation, thus blocking HIV-1 fusion with the target cell.