Antiviral Activity of a Zymolytic Grain Based Extract on Human Immunodeficiency Virus Type 1 In Vitro

Figure 3

ZGE acts on both the structural protein on viral surface and the post-attachment stage of viral infection. (a) A diagram of the drug blocking assay. During the −1.5 h, TZM-bl cells and the prepared virions were incubated with ZGE respectively at 4°C in Procedure IIand III. During the following 1.5 h for viral attachment, the viruses alone (I, II, and V) or with ZGE (IV and VI), ZGE-S (VII), or ZGE-P (VIII) were added to the cells. The already incubated viruses with ZGE in Procedure (III) were added as the others. Finally, the cells wereincubated in the absence (I–IV) or presence of ZGE (V and VI), ZGE-S (VII), or ZGE-P (VIII) until harvested. (b) Relative infectivity of viruses in the procedures shown in (a) was tested in a luciferase indicator assay, with the viruses in Procedure (I) set to 100% (blackcolumn). Results shown are the average of three independent infections. The statistical significance was tested between the virus control group and other groups. (c) ZGE, 3TC and 4E10 were tested for their blocking stages according to the procedures described in (a). (d) Model of drug blocking at different stages in the process of HIV-1 attachment and membrane fusion. (Upper left) ZGE may act on the HIV-1 Env surface subunit gp120 via the 1.5 h incubation with the viruses, resulting in the inhibition of viral infectivity. (Upper right) gp120 binds with the coreceptors on the target cell at 4°C. ZGE continues to interfere with this process. (Lower) The HIV-1 Env transmembrane subunit gp41 does not change conformation to expose the epitope that 4E10 binds to until the temperature is shifted to 37°C. Thus 4E10 functions at the post-attachment stage. The HIV-1 envelope fuses withthe cytoplasmic membrane and viral RNA is released into the cytoplasm where 3TC functions to inhibit the process of reverse transcription (RT). ZGE also has effects on the post-attachment stage where the mechanism is not clear yet.

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