Background Fucosylated glycosaminoglycan (FG) is a novel glycosaminoglycan with a chondroitin sulfate-like backbone and fucose sulfate branches. The aim of this study is to investigate the mechanism and structure–activity relationships (SAR) of FG for combating HIV-1 infection. Methods Anti-HIV activities of FGs were assessed by a cytopathic effect assay and an HIV-1 p24 detection assay. The biomolecule interactions were explored via biolayer interferometry technology. The SAR was established by comparing its anti-HIV-1 activities, conserved CD4 induced (CD4i) epitope-dependent interactions and anticoagulant activities. Results FG efficiently and selectively inhibited the X4- and R5X4-tropic HIV-1 infections in C8166 cells with little cytotoxicity against C8166 cells and PBMCs. Our data indicated that FG bound to gp120 with nanomolar affinity and may interact with CD4i of gp120. Additionally, the CD4i binding affinity of FG was higher than that of dextran sulfate. SAR studies suggested that the unique sulfated fucose branches account for the anti-HIV-1 activity. The molecular size and present carboxyl groups of FG may also play important roles in various activities. Notably, several FG derivatives showed higher anti-HIV-1 activities and much lower anticoagulant activities than those of heparin. Conclusions FG exhibits strong activity against X4- and R5X4-tropic HIV-1 infections. The mechanism may be related to targeting CD4i of gp120, which results in inhibition of HIV-1 entry. The carboxyl group substituted derivatives of FG (8.5–12.8 kDa), might display high anti-HIV-1 activity and low anticoagulant activity. General significance Our data supports further the investigation of FG derivatives as novel HIV-1 entry inhibitors targeting CD4i.
Two kinds of chitosan-stavudine (d4T) conjugates, chitosan- O -isopropyl-5′- O -d4T monophosphate conjugate (Cs-P-d4T) with a phosphoramide linkage and chitosan-5′- O -succinyl-d4T conjugate (Cs-S-d4T) with a succinic spacer, were synthesized using an Atherton-Todd reaction and carbodiimide coupling reaction, respectively, and then structurally characterized. Their in vitro drug release behaviors and anti-human immunodeficiency virus (HIV) activity were investigated and compared. Both of the chitosan-d4T conjugates more strongly prefer to release corresponding d4T derivatives rather than free d4T in a prolonged manner but have different hydrolysis routes. The anti-HIV activity and cytotoxicity evaluated in the MT4 cell line revealed that the anti-HIV selectivity index was in the following order: Cs-P-d4T > d4T >> Cs-S-d4T since the released d4T-5′-( O -isopropyl) monophosphate from Cs-P-d4T can bypass the rate-limiting bottleneck of nucleoside phosphorylation, while the released 5′- O -succinyl-d4T from Cs-S-d4T has to be hydrolyzed to d4T and then successively phosphorylated to its active form to exert antiviral activity. The results suggested that constructing a chitosan-nucleoside reverse transcriptase inhibitor (NRTI) conjugate with a phosphoramide linkage may be an efficient approach for improving NRTI therapy efficacy in antiretroviral treatment.
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